METHODS OF TREATING CANCER

REFERENCE TO AN ELECTRONIC SEQUENCE LISTING

The contents of the electronic Sequence Listing (757972001001seqlist.xml, size: 482,202 bytes; and Date of Creation: Aug. 17, 2023) are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to methods of treating cancer that comprise administering a polypeptide (e.g. a fusion polypeptide) that comprises a SIRPα D1 domain variant and an Fc domain variant in conjunction with a therapeutic antibody.

BACKGROUND

Many cancers have a poor prognosis, even when treated with available therapeutics. For example, non-small cell lung cancer (NSCLC) patients with metastatic disease receiving PD-1 and PD-L1 checkpoint inhibitors who have failed prior platinum based therapies have a median overall survival rate of approximately one year (Garon et al., New Engl J Med (2015) 372:2018-28; Herbst et al., Lancet (2016) 387:1540-50; Fehrenbacher et al., Lancet (2016) 387(10030):1837-46), and over half NSCLC patients with advanced stage disease have an overall 5-year survival rate of 17.7% (U.S. Cancer Statistics Working Group, available at the web site www(dot)cdc(dot)gov/uscs). Similarly, the overall 5-year survival rate for gastric cancer patients in the United States is 30.4% (U.S. Cancer Statistics Working Group). In patients with relapsed indolent lymphomas, subsequent relapses usually occur with increasingly aggressive histologies and a transformation risk of 30% by 10 years in one series (Montoto et al., J Clin Oncol (2007) 25(17):2426-33). Further, for patients with recurrent aggressive histologies, cure is rare, and novel salvage regimens are needed (Larouche et al., J Clin Oncol (2010) 28(12):2094-100). CD20-positive non-Hodgkin lymphoma (NHL) as the 10th most common cancer globally, is also the 10th leading cause of cancer death, accounting for 199,670 deaths per year, worldwide (World Health Organization 2016(a), available at the website globocan(dot)iarc(dot)fr/Pages/fact_sheets_cancer(dot)aspx). There are estimated to be over 35,000 people living in the US with metastatic HNSCC, with over 50,000 newly incident cases at all stages diagnosed in 2019. Five-year survival is 84% for patients diagnosed with localized disease but decreases to only 39% for those diagnosed with metastatic disease. There is a need in the art for new treatments to provide additional therapeutic options and improve outcomes for such patients.

Tumor cells manipulate the myeloid compartment to evade the anti-tumor host immune response (Gabrilovich et al., Nat Rev Immunol (2012) 12(4):253-68). For example, while CD47 expressed on the surface of normal cells binds SIRPα on macrophages and provides a “don't eat me” signal, tumor cells have also been found to overexpress CD47 to evade the macrophage component of immune surveillance (Oldenborg, ISRN Hematol (2013) 614619).

Macrophage-mediated destruction of cancer cells requires both the disruption of “don't eat me” signals (e.g., CD47-SIRPα) and the activation of “eat me” signals. Neither component alone is sufficient to trigger maximal phagocytic reaction against tumor cells. As described above, CD47 provides a fundamental “don't eat me” signal through its interaction with SIRPα on macrophages. The pro-phagocytic “eat me” signal can be provided to the same macrophages by binding to their activating Fc gamma receptors. For example, the pro-phagocytic “eat me” signal can be provided by binding of anti-tumor antibodies to Fc receptors on macrophages.

All references cited herein, including patent applications, patent publications, and UniProtKB/Swiss-Prot Accession numbers are herein incorporated by reference in their entirety, as if each individual reference were specifically and individually indicated to be incorporated by reference.

SUMMARY OF THE INVENTION

Provided is a method of treating non-small cell lung cancer (NSCLC) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-PD-1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the individual is a human. In some embodiments, the NSCLC in the individual has progressed on a prior immune checkpoint inhibitor (CPI) therapy and/or has a PD-L1 tumor proportion score (TPS) of less than 50%,

Also provided is a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in the manufacture of a medicament for treating NSCLC in an individual, wherein the medicament is for use (such as formulated for use) in combination with an anti-PD1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the individual is a human. In some embodiments, the NSCLC in the individual has progressed on a prior immune checkpoint inhibitor (CPI) therapy and/or has a PD-L1 tumor proportion score (TPS) of less than 50%.

Also provided is a composition (such a pharmaceutical composition) comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in combination with an anti-PD1 antibody for treating NSCLC in an individual (e.g., for use in a method of treating NSCLC in an individual), wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the individual is a human. In some embodiments, the NSCLC in the individual has progressed on a prior immune checkpoint inhibitor (CPI) therapy and/or has a PD-L1 tumor proportion score (TPS) of less than 50%.

In some embodiments, the prior CPI (immune checkpoint inhibitor therapy) comprised one or more agents selected from the group consisting of: nivolumab, pembrolizumab, atezolizumab, avelumab, durvalumab, and cemiplimab. In some embodiments, the anti-PD-1 antibody blocks the interaction between PD-1 and PD-L1. In some embodiments, the anti-PD-1 antibody is pembrolizumab. In some embodiments, the pembrolizumab is administered to the individual at a dose of 200 mg every 3 weeks (Q3W) by intravenous (IV) infusion.

Also provided is a method of treating head and neck squamous cell carcinoma (HNSCC) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-PD-1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the HNSCC in the individual has progressed while on a prior platinum therapy or after the platinum therapy, and wherein the individual is a human.

Also provided is a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in the manufacture of a medicament for treating HNSCC in an individual, wherein the medicament is for use (such as formulated for use) in combination with an anti-PD1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the HNSCC in the individual has progressed while on a prior platinum therapy or after the platinum therapy, and wherein the individual is a human.

Also provided is a composition (such a pharmaceutical composition) comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in combination with an anti-PD1 antibody for treating HNSCC in an individual (e.g., for use in a method of treating HNSCC in an individual), wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the HNSCC in the individual has progressed while on a prior platinum therapy or after the platinum therapy, and wherein the individual is a human.

In some embodiments, the individual with HNSCC received prior therapy with an immune checkpoint inhibitor (e.g., an immune checkpoint inhibitor described herein). In some embodiments, such individual is considered to be/referred to as “checkpoint inhibitor experienced.” In some embodiments, the individual with HNSCC has not received prior therapy with an immune checkpoint inhibitor. In some embodiments, such individual is considered to be/referred to as “checkpoint inhibitor naïve.” In some embodiments, the prior platinum therapy comprised one or more therapeutic agents selected from the group consisting of: cisplatin, carboplatin, and oxaliplatin. In some embodiments, the anti-PD-1 antibody blocks the interaction between PD-1 and PD-L1. In some embodiments, the anti-PD-1 antibody is pembrolizumab. In some embodiments, the pembrolizumab is administered (such as formulated for administration) to the individual at a dose of 200 mg every 3 weeks (Q3W) by intravenous (IV) infusion.

Provided is a method of treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-HER2 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the gastric/GEJ cancer in the individual has progressed following a prior treatment with a fluoropyrimidine-based therapy and/or a prior treatment with an anti-HER2 antibody, and wherein the individual is a human.

Also provided is a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in the manufacture of a medicament for treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual, wherein the medicament is for use (such as formulated for use) in combination with an anti-HER2 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P33 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the gastric/GEJ cancer in the individual has progressed following a prior treatment with a fluoropyrimidine-based therapy and/or a prior treatment with an anti-HER2 antibody, and wherein the individual is a human.

Also provided is a composition (such a pharmaceutical composition) comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in combination with an anti-HER2 antibody for treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual (e.g., for use in a method of treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual), wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the gastric/GEJ cancer in the individual has progressed following a prior treatment with a fluoropyrimidine-based therapy and/or a prior treatment with an anti-HER2 antibody, and wherein the individual is a human.

In some embodiments, the prior treatment with the fluoropyrimidine-based therapy or the prior treatment with the anti-HER2 antibody comprised one or more therapeutic agents selected from the group consisting of: trastuzumab, pertuzumab, 5-fluorouracil, capecitabine, margetuximab, and FOLFOX. In some embodiments, the anti-HER2 antibody is trastuzumab. In some embodiments, trastuzumab is administered (such as formulated for administration) to the individual at an initial dose of 8 mg/kg and at a dose of 6 mg/kg for each subsequent dose, and wherein trastuzumab is administered to the individual by IV infusion every 3 weeks (Q3W).

Provided is a method of treating aggressive non-Hodgkin lymphoma (NHL) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the aggressive NHL in the individual is relapsed and/or refractory to a prior treatment for aggressive NHL and there is no available curative therapy, and wherein the individual is a human.

Also provided is a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in the manufacture of a medicament for treating aggressive non-Hodgkin lymphoma (NHL) in an individual, wherein the medicament is for use (such as formulated for use) in combination with an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the aggressive NHL in the individual is relapsed and/or refractory to a prior treatment for aggressive NHL and there is no available curative therapy, and wherein the individual is a human.

Also provided is a composition (such a pharmaceutical composition) comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in combination with an anti-CD20 antibody for treating aggressive non-Hodgkin lymphoma (NHL) in an individual (e.g., for use in a method of treating aggressive NHL), wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the aggressive NHL in the individual is relapsed and/or refractory to a prior treatment for aggressive NHL and there is no available curative therapy, and wherein the individual is a human.

In some embodiments, the aggressive NHL is diffuse large B-cell lymphoma (DLBCL), e.g., de novo DLBCL or transformed DLBCL. In some embodiments, the prior treatment(s) for aggressive NHL comprised rituximab, cyclophosphamide, doxorubicin, vincristine, gemcitabine, lenalidomide, prednisone, prednisolone, etoposide, procarbazine, epirubicin, bendamustine, cisplatin, oxaliplatin, cytarabine, ifosfamide, carboplatin, dexamethasone, mesna, carmustine, melphalan, solumedrol, methyl-glyoxal-bis(guanylhydrazone), thiotepa, methotrexate, ibrutinib, obinituzumab, tisagenlecleucel, axicabtagene, brentuximab vedotin, and combinations thereof. In some embodiments, the anti-CD20 antibody is rituximab. In some embodiments, the rituximab is administered (such as formulated for administration) to the individual at a dose of 375 mg/m²by IV infusion, wherein rituximab is administered (such as formulated for administration) to the individual once per week for four weeks and once per month thereafter.

Provided is a method of treating indolent lymphoma in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P33 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the indolent lymphoma in the individual is relapsed and/or refractory to a prior treatment for indolent lymphoma, and wherein the individual is a human.

Also provided is a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in the manufacture of a medicament for treating indolent lymphoma in an individual, wherein the medicament is for use (such as formulated for use) in combination with an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the indolent lymphoma in the individual is relapsed and/or refractory to a prior treatment for indolent lymphoma, and wherein the individual is a human.

Also provided is a composition (such a pharmaceutical composition) comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant for use in combination with an anti-CD20 antibody for treating indolent lymphoma in an individual (e.g., for use in a method of treating indolent lymphoma in an individual), wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; wherein the indolent lymphoma in the individual is relapsed and/or refractory to a prior treatment for indolent lymphoma, and wherein the individual is a human.

In some embodiments, the indolent lymphoma is an indolent non-Hodgkin lymphoma (NHL). In some embodiments, the indolent NHL is a marginal zone lymphoma or a follicular lymphoma. In some embodiments, the prior treatment for indolent lymphoma comprised rituximab, cyclophosphamide, doxorubicin, vincristine, gemcitabine, lenalidomide, prednisone, prednisolone, etoposide, procarbazine, epirubicin, bendamustine, cisplatin, oxaliplatin, cytarabine, ifosfamide, carboplatin, dexamethasone, mesna, carmustine, melphalan, solumedrol, methyl-glyoxal-bis(guanylhydrazone), thiotepa, methotrexate, ibrutinib, obinituzumab, tisagenlecleucel, axicabtagene, brentuximab vedotin, fludarabine mitoxantrone, everolimus, bortezomib, navitoclax, and combinations thereof. In some embodiments, the anti-CD20 antibody is rituximab. In some embodiments, the rituximab is administered (such as formulated for administration) to the individual at a dose of 375 mg/m²by IV infusion, wherein rituximab is administered (such as formulated for administration) to the individual once per week for four weeks and once per month thereafter. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (such as the medicament manufactured using such polypeptide or a pharmaceutical composition comprising such polypeptide) is administered (such as formulated for administration) to the individual at a dose of 10 mg/kg or 15 mg/kg once per week (QW), e.g., by IV infusion.

In some embodiments of any of the methods herein, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 85. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NOL: 81. In some embodiments, the Fc domain variant is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant comprises the amino acid sequence of SEQ ID NO: 136. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant comprises the amino acid sequence of SEQ ID NO: 135. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant forms a homodimer.

In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (such as the medicament manufactured using such polypeptide or a pharmaceutical composition comprising such polypeptide) is administered (such as formulated for administration) to the individual at a dose of 10 mg/kg once per week (QW). In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (or the medicament manufactured therefrom or the pharmaceutical composition comprising such polypeptide) is administered (such as formulated for administration) to the individual by IV infusion.

Also provided is a kit comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (such as the medicament manufactured using such polypeptide or a pharmaceutical composition comprising such polypeptide), for use in combination with pembrolizumab for treating non-small cell lung cancer (NSCLC) in an individual (e.g., human individual) in need thereof, according to a method described herein. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P33 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the NSCLC in the individual has progressed on a prior immune checkpoint inhibitor (CPI) therapy and/or has a PD-L1 tumor proportion score (TPS) of less than 50%. In some embodiments, the kit further comprises instructions for administering pembrolizumab at a dose of 200 mg every 3 weeks (Q3W) by IV infusion. In some embodiments, the kit further comprises instructions for administering the polypeptide (e.g. fusion polypeptide) at a dose of 10 mg/kg once a week, e.g., by IV infusion.

Also provided is a kit comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (such as the medicament manufactured using such polypeptide or a pharmaceutical composition comprising such polypeptide) for use in combination with pembrolizumab for treating head and neck squamous cell carcinoma (HNSCC) in an individual (e.g., a human individual) in need thereof, according to a method described herein. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P33 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and the HNSCC in the individual has progressed while on a prior platinum therapy or after the platinum therapy. In some embodiments, the individual received prior therapy with an immune checkpoint inhibitor. In some embodiments, the individual has not received prior therapy with an immune checkpoint inhibitor. In some embodiments, the kit further comprises instructions for administering pembrolizumab at a dose of 200 mg every 3 weeks (Q3W) by IV infusion. In some embodiments, the kit further comprises instructions for administering the polypeptide (e.g. fusion polypeptide) at a dose of 10 mg/kg once a week, e.g., by IV infusion.

Also provided herein is a kit comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant in a pharmaceutically acceptable carrier for use in combination with trastuzumab for treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual (e.g., a human individual) in need thereof, according to a method described herein. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and the HER2-positive gastric/GEJ cancer in the individual has progressed following a prior fluoropyrimidine-based therapy or a prior treatment with an anti-HER2 antibody. In some embodiments, the kit further comprises instructions for administering trastuzumab at an initial dose of 8 mg/kg and at a dose of 6 mg/kg for each subsequent dose, and wherein trastuzumab is administered to the individual by IV infusion every 3 weeks (Q3W). In some embodiments, the kit further comprises instructions for administering the polypeptide (e.g. fusion polypeptide) at a dose of 10 mg/kg once a week, e.g., by IV infusion.

Provided is a kit comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant in a pharmaceutically acceptable carrier for use in combination with rituximab for treating aggressive non-Hodgkin lymphoma (NHL) in an individual (e.g., a human individual) in need thereof, according to a method described herein. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and the aggressive NHL in the individual is relapsed and/or refractory to a prior treatment for aggressive NHL and there is no available curative therapy. In some embodiments, the aggressive NHL is a diffuse large B-cell lymphoma (DLBCL), e.g., a de novo DLBCL or a transformed DLBCL. In some embodiments, the aggressive NHL is a mantle cell lymphoma. In some embodiments, the kit further comprises instructions for administering rituximab at a dose of 375 mg/m²by IV infusion, wherein rituximab is administered to the individual once per week for four weeks and once per month thereafter. In some embodiments, the kit further comprises instructions for administering the polypeptide (e.g. fusion polypeptide) at a dose of 10 mg/kg or 15 mg/kg once a week, e.g., by IV infusion.

Also provided is a kit comprising a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant in a pharmaceutically acceptable carrier, for use in combination with rituximab for treating indolent lymphoma in an individual (e.g., a human individual) in need thereof, according to a method described herein. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and the indolent lymphoma in the individual is relapsed or refractory to a prior treatment for indolent lymphoma. In some embodiments, the indolent lymphoma is an indolent non-Hodgkin lymphoma (NHL). In some embodiments, the indolent NHL is a Marginal zone lymphoma or a follicular lymphoma. In some embodiments, the kit further comprises instructions for administering rituximab at a dose of 375 mg/m²by IV infusion, wherein rituximab is administered to the individual once per week for four weeks and once per month thereafter. In some embodiments, the kit further comprises instructions for administering the polypeptide (e.g. fusion polypeptide) at a dose of 10 mg/kg or 15 mg/kg once a week, e.g., by IV infusion.

In some embodiments of any of the kits, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 85. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NOL: 81. In some embodiments, the Fc domain variant is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant comprises the amino acid sequence of SEQ ID NO: 136. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant comprises the amino acid sequence of SEQ ID NO: 135. In some embodiments, the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant forms a homodimer. In some embodiments, further comprising instructions for administering the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (or the medicament manufactured therefrom or the pharmaceutical composition comprising such polypeptide) to the individual at a dose of 10 mg/kg once per week (QW). In some embodiments, the kit comprises instructions for administering the polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant (or the medicament manufactured therefrom or the pharmaceutical composition comprising such polypeptide) to the individual by IV infusion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B depicts Drug A is a monomer (FIG. 1A), and as a homodimer (FIG. 1B). The SIRPα D1 domain variant selectively binds CD47 with picomolar binding affinity to block its interactions with SIRPα. The molecular weight of Drug A is half the size of a typical antibody, allowing twice the molar concentration to be delivered to tumors. The Fc domain is modified to eliminate binding to Fc gamma receptors to minimize toxicity. Drug A exhibits antibody-like pharmacokinetics.

FIG. 2 provides a schematic of the clinical study described in Example 1.

FIGS. 3A-3C show the clinical activity of Drug A+trastuzumab in the HER2 positive gastric/GEJ cancer expansion cohort. FIG. 3A provides the change in tumor size, shown as percent from baseline. ORR=overall response rate; DCR=disease control rate; mPFS=median progression-free; CI=confidence interval. The changes in tumor sizes shown as percent from baseline for each patient over the course of the study are provided in FIG. 3B. For FIGS. 3A-3B: patients who received at least one dose of Drug A in the expansion phase, had a baseline assessment, and at least one post-baseline disease assessment are included; the top dashed line indicates the threshold for objective progression; the bottom dashed line indicates the threshold for overall response. The duration of treatment for each enrolled patient who received at least one dose of Drug A in the expansion phase is provided in FIG. 3C. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

FIGS. 4A-4C show the clinical activity of Drug A+pembrolizumab in the HNSCC expansion cohort. FIG. 4A provides the change in tumor size, shown as percent from baseline. ORR=overall response rate; DCR=disease control rate; mPFS=median progression-free survival; CI=confidence interval; CP=immune checkpoint therapy; CPS=combination positive score for PD-L1 staining. The changes in tumor sizes shown as percent from baseline for each patient over the course of the study are provided in FIG. 4B. For FIGS. 4A-4B: patients who received at least one dose of Drug A in the expansion phase, had a baseline assessment, and at least one post-baseline disease assessment are included; the top dashed line indicates the threshold for objective progression; the bottom dashed line indicates the threshold for overall response. The duration of treatment for each enrolled patient who received at least one dose of Drug A in the expansion phase is provided in FIG. 4C. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

FIGS. 5A-5C show the clinical activity of Drug A+pembrolizumab in the NSCLC expansion cohort. FIG. 5A provides the change in tumor size, shown as percent from baseline. DCR=disease control rate; mPFS=median progression-free survival; CI=confidence interval; TPS=tumor proportion score for PD-L1 staining. The changes in tumor sizes shown as percent from baseline for each patient over the course of the study are provided in FIG. 5B. For FIGS. 5A-5B: patients who received at least one dose of Drug A in the expansion phase, had a baseline assessment, and at least one post-baseline disease assessment are included; the top dashed line indicates the threshold for objective progression; the bottom dashed line indicates the threshold for partial response. The duration of treatment for each enrolled patient who received at least one dose of Drug A in the expansion phase is provided in FIG. 5C. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

FIGS. 6A-6B provide pharmacokinetic and CD47 target occupancy parameters of Drug A administered in combination with pembrolizumab or trastuzumab over the course of the study. As shown in FIG. 6A, Drug A PK (Drug A serum concentration) were within predicted 95% intervals based on an established population PK model. The steady-state half-life of Drug A (10 mg/kg QW) was predicted to be approximately 16 days. Drug A PK time points included intensive sampling in cycles 1 and 3, and pre-dose and end-of-infusion only in every cycle thereafter. FIG. 6B shows that near complete CD47 target occupancy is maintained in CD4+ T cells that express CD47 throughout the Drug A dosing interval when Drug A was administered in combination with pembrolizumab or trastuzumab. TO=target occupancy.

FIGS. 7A-7C show the anti-tumor response in patients treated with Drug A in combination with pembrolizumab or trastuzumab. The percent positive intra-tumoral CD68+(left), CD163+(middle), and CD8+(right) cells in paired biopsies before and after treatment from 5 NSCLC patients treated with Drug A+pembrolizumab, 6 HNSCC patients treated with Drug A+pembrolizumab and 1 gastric cancer patient treated with Drug A+trastuzumab are provided in FIG. 7A. Tumor-associated macrophages and infiltrating lymphocytes were increased after treatment. Images from a biopsy of an NSCLC PD-L1(−) patient treated with Drug A+pembrolizumab showing staining for CD68 and CD8 before and during treatment (C3=Cycle 3) are provided in FIG. 7B. Images from a biopsy of an HNSCC PD-L1(+) patient treated with Drug A+pembrolizumab showing staining for CD68 and CD8 before and during treatment (Cycle 3) are provided in FIG. 7C. In FIGS. 7B-7C: the graph to the right shows the changes in tumor sizes as percent from baseline for each patient over the course of the study; the top dashed line indicates the threshold for objective progression; the bottom dashed line indicates the threshold for partial response. CD68 and CD163 markers indicate macrophages; the CD8 marker indicates T lymphocytes.

FIG. 8 provides a schematic depiction of a proposed mechanism for the anti-tumor activity of Drug A when administered in combination with anti-cancer therapeutic antibodies such as pembrolizumab, trastuzumab, or rituximab.

FIG. 9A provides a schematic showing the clinical activity of Drug A in combination with pembrolizumab in response-evaluable ≥2 L HNSCC patients (including both checkpoint inhibitor-naïve patients in checkpoint inhibitor-experienced patients). CPS=combined positive score (i.e., the number of PD-L1 positive staining cells (tumor cells, lymphocytes, and macrophages) divided by the total number of viable tumor cells, multiplied by 100).

FIG. 9B provides a schematic showing the best overall response and duration of response in ≥2 L HNSCC patients treated with Drug A and pembrolizumab.

FIG. 10A provides a schematic showing the clinical activity of Drug A in combination with pembrolizumab in response-evaluable ≥2 L NSCLC patients. Patient indicated with * demonstrated change greater than 80%. TPS=tumor proportion score. FIG. 10B provides a schematic showing the best overall response and duration of response in ≥2 L NSCLC patients treated with Drug A and pembrolizumab.

FIG. 11A provides a schematic showing the clinical activity of Drug A in combination with trastuzumab in response-evaluable ≥2 L HER2⁺ gastric or HER2⁺ GEJ cancer patients. One patient with clinical progression not shown. HER2 score reflects the HER2 expression level of tumor cells. FIG. 11B provides a schematic showing the best overall response and duration of response in ≥2 L HER2⁺ gastric or HER2⁺ GEJ cancer patients treated with Drug A and trastuzumab.

FIG. 12 provides a schematic showing the clinical activity of Drug A in combination with rituximab in response-evaluable patients with relapsed/refractory non-Hodgkin lymphoma. Patients denoted with “{circumflex over ( )}” demonstrated a more than 80% increase in measurable lesion compared to baseline. Patients denoted with “*” achieved complete response or metabolic complete response. Patients denoted with “mPR” achieved metabolic partial response. Two patients (1 each at 10 mg/kg and 15 mg/kg Drug A) with clinical progression are not shown. One patient (10 mg/kg Drug A) with metabolic CR is not represented in the plots.

FIG. 13A provides a schematic showing the best overall response and duration of response in patients relapsed/refractory non-Hodgkin lymphoma treated with 10 mg/kg Drug A and rituximab. FIG. 13B provides a schematic showing the best overall response and duration of response in patients relapsed/refractory non-Hodgkin lymphoma treated with 15 mg/kg Drug A and rituximab. One patient with clinical progression Study Day 8 as best response not shown.

DETAILED DESCRIPTION OF THE INVENTION
Definitions

The term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within 1 or more than 1 standard deviation, per the practice in the art. Alternatively, “about” can mean a range of up to 20%, up to 10%, up to 5%, or up to 1% of a given value. Alternatively, particularly with respect to biological systems or processes, the term can mean within an order of magnitude, preferably within 5-fold, and more preferably within 2-fold, of a value. Where particular values are described in the application and claims, unless otherwise stated the term “about” meaning within an acceptable error range for the particular value should be assumed.

The terminology used herein is for the purpose of describing particular cases only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”

As used herein, the terms “treatment”, “treating”, and the like, refer to administering an agent, or carrying out a procedure, for the purposes of obtaining an effect. In some embodiments, the effect is prophylactic in terms of completely or partially preventing a disease or symptom thereof. In some embodiments, the effect is therapeutic in terms of affecting a partial or complete cure for a disease or symptoms of the disease.

As used herein, the term “antibody” refers to intact antibodies; antibody fragments, provided that they exhibit the desired biological activity (e.g. epitope binding); monoclonal antibodies; polyclonal antibodies; monospecific antibodies; multi-specific antibodies (e.g., bispecific antibodies); and antibody-like proteins.

As used herein, the term “antibody variable domain” refers to the portions of the light and heavy chains of an antibody that include amino acid sequences of complementary determining regions (CDRs, e.g., CDR L1, CDR L2, CDR L3, CDR H1, CDR H2, and CDR H3) and framework regions (FRs).

As used herein, the term “linker” refers to a linkage between two elements, e.g., protein domains. In some embodiments, a linker can be a covalent bond or a spacer. The term “spacer” refers to a moiety (e.g., a polyethylene glycol (PEG) polymer) or an amino acid sequence (e.g., a 1-200 amino acid sequence) occurring between two polypeptides or polypeptide domains to provide space or flexibility (or both space and flexibility) between the two polypeptides or polypeptide domains. In some embodiments, an amino acid spacer is part of the primary sequence of a polypeptide (e.g., joined to the spaced polypeptides or polypeptide domains via the polypeptide backbone).

As used herein, the term “effective amount” refers to an amount of a polypeptide or a pharmaceutical composition containing a polypeptide described herein, e.g., a polypeptide having a SIRPα D1 domain or variant thereof, that is sufficient and effective in achieving a desired therapeutic effect in treating a patient having a disease, such as a cancer, e.g., solid tumor or hematological cancer. In some embodiments, an effective amount of polypeptide will avoid adverse side effects.

As used herein, the term “pharmaceutical composition” refers to a medicinal or pharmaceutical formulation that includes an active ingredient as well as excipients or diluents (or both excipients and diluents) and enables the active ingredient to be administered by suitable methods of administration. In some embodiments, the pharmaceutical compositions disclosed herein include pharmaceutically acceptable components that are compatible with the polypeptide. In some embodiments, the pharmaceutical composition is in tablet or capsule form for oral administration or in aqueous form for intravenous or subcutaneous administration, for example by injection.

As used herein, the terms “subject,” “individual,” and “patient” are used interchangeably to refer to a vertebrate, for example, a mammal. Mammals include, but are not limited to, murines, simians, humans, farm animals, sport animals, and pets. Tissues, cells, and their progeny of a biological entity obtained in vivo or cultured in vitro are also encompassed. None of the terms entail supervision of a medical professional.

As used herein, the term “affinity” or “binding affinity” refers to the strength of the binding interaction between two molecules. Generally, binding affinity refers to the strength of the sum total of non-covalent interactions between a molecule and its binding partner, such as a SIRPα D1 domain variant and CD47. Unless indicated otherwise, binding affinity refers to intrinsic binding affinity, which reflects a 1:1 interaction between members of a binding pair. The binding affinity between two molecules is commonly described by the dissociation constant (KD) or the association constant (KA). Two molecules that have low binding affinity for each other generally bind slowly, tend to dissociate easily, and exhibit a large KD. Two molecules that have high affinity for each other generally bind readily, tend to remain bound longer, and exhibit a small KD. In some embodiments, the KD of two interacting molecules is determined using known methods and techniques, e.g., surface plasmon resonance (SPR). KD can be calculated as the ratio of koff/kon.

As used herein, the term “K_Dless than” refers to a numerically smaller K_Dvalue and an increasing binding affinity relative to the recited KD value. As used herein, the term “KD greater than” refers to a numerically larger KD value and a decreasing binding affinity relative to the recited KD value.

As used herein, “in conjunction with” refers to administration of one treatment modality in addition to another treatment modality. As such, “in conjunction with” refers to administration of one treatment modality before, during, or after administration of the other treatment modality to the individual.

Overview

Provided herein are methods of treating cancer in an individual (e.g., a human individual) that comprise administering to the individual (a) a polypeptide (e.g., a fusion polypeptide) that comprises a SIRPα D1 domain variant and an Fc domain variant and (b) a therapeutic antibody. In some embodiments, the polypeptide comprises any one of the SIRPα D1 domain variants described herein (unless otherwise specified).

In some embodiments, provided is a method of treating non-small cell lung cancer (NSCLC) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-PD-1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85, wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the individual is a human. In some embodiments, the NSCLC in the individual has progressed on a prior immune checkpoint inhibitor (CPI) therapy and/or has a PD-L1 tumor proportion score (TPS) of less than 50%. In some embodiments, the individual has not received prior CPI therapy. In some embodiments, the individual is PD-L1 negative. In some embodiments, the individual is PD-L1 positive.

In some embodiments, provided is a method of treating head and neck squamous cell carcinoma (HNSCC) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-PD-1 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the HNSCC in the individual has progressed while on a prior platinum therapy or after the platinum therapy, and wherein the individual is a human. In some embodiments, the individual received prior immune checkpoint inhibitor (CPI) therapy (e.g., treatment with an immune checkpoint inhibitor described herein). In some embodiments, the individual has not received prior CPI therapy. In some embodiments, the individual is PD-L1 negative. In some embodiments, the individual is PD-L1 positive.

In some embodiments an individual is “PD-L1 negative” if the individual has a cancer that does not express PD-L1 biomarker or expresses very low levels of PD-L1. In some embodiments, the individual is “PD-L1 negative” or has a “PD-L1 negative cancer” if PD-L1 expression (e.g., protein expression) is not detected on (or in) tumor cells (TC) in a sample from the individual, if PD-L1 expression (e.g., protein expression) is not detected on (or in) tumor-infiltrating immune cells (IC) in a sample from the individual, or if PD-L1 expression (e.g., protein expression) is detected at very low levels on (or in) TC and/or IC in a sample from the individual. In some embodiments, the individual is PD-L1 negative if, e.g., 0%, less than about 1%, less than about 5%, or less than about 10% of the tumor cells (TC) and/or tumor-infiltrating immune cells (IC) in a sample obtained from the individual express PD-L1, as determined using an assay (e.g., an assay described herein) for determining the PD-L1 status of an individual. In some embodiments, an individual or tumor may be considered PD-L1 negative because it has no T-cell infiltrates. Such assays are known and routinely used by medical professionals.

In some embodiments, an individual is “PD-L1 positive” if the individual has a cancer that expresses (has been shown to express e.g., in a diagnostic test) PD-L1 biomarker. In some embodiments, such individual is “PD-L1 positive” or has cancer that is a “PD-L1 positive cancer.” In some embodiments, the individual is “PD-L1 positive” or has a “PD-L1 positive cancer” if PD-L1 expression (e.g., protein expression) is detected on (or in) tumor cells (TC) in a sample from the individual, or if PD-L1 expression (e.g., protein expression) is detected on (or in) tumor-infiltrating immune cells (IC) in a sample from the individual. In some embodiments, the individual's TC and/or IC express low levels of PD-L1 biomarker. In some embodiments, the individual's TC and/or IC express high levels PD-L1 biomarker. In some embodiments, the individual is “PD-L1 positive” or has cancer that is a “PD-L1 positive cancer” if the PD-L1 biomarker is present (e.g., detected) in more than 0% of a sample, in at least 1% of a sample, in at least 5% of a sample, or in at least 10% of a sample from the individual (e.g., a sample from the individual that contains the individual's TC and/or IC), as determined using an assay (e.g., an assay described herein) for determining the PD-L1 status of an individual. Such assays are known and routinely used by medical professionals. In some embodiments, an individual is “PD-L1” positive or has a “PD-L1 positive cancer” if the individual's tumor proportion score (TPS) is ≥50% (i.e., if ≥50% of the viable tumor cells in a sample from the individual express PD-L1, e.g., at any level).

In some embodiments, provided is a method of treating HER2-positive gastric/gastroesophageal junction (GEJ) cancer in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-HER2 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the gastric/GEJ cancer in the individual has progressed following a prior treatment with a fluoropyrimidine-based therapy and/or a prior treatment with an anti-HER2 antibody, and wherein the individual is a human.

In some embodiments, provided is a method of treating aggressive non-Hodgkin lymphoma or “NHL” (e.g., de novo or transformed diffuse large B cell lymphoma (DLBCL) or mantle cell lymphoma) in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the aggressive NHL in the individual is relapsed and/or refractory to a prior treatment for aggressive NHL and there is no available curative therapy, and wherein the individual is a human. In some embodiments, the relapsed/refractory aggressive NHL is relapsed/refractory DLBCL (e.g., de novo or transformed DLBCL). In some embodiments, the a relapsed/refractory aggressive NHL is relapsed/refractory mantle cell lymphoma (MCL).

In some embodiments, provided is a method of treating indolent lymphoma in an individual, comprising administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant, and (b) an anti-CD20 antibody, wherein the SIRPα D1 domain variant comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85; wherein the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat; and wherein the indolent lymphoma in the individual is relapsed and/or refractory to a prior treatment for indolent lymphoma, and wherein the individual is a human. In some embodiments, the indolent lymphoma (such as a relapsed/refractory indolent lymphoma) is a non-Hodgkin lymphoma (NHL), e.g., a relapsed/refractory indolent NHL. In some embodiments, the indolent NHL (e.g., relapsed/refractory NHL) is a follicular lymphoma (e.g., a relapsed/refractory follicular lymphoma). In some embodiments, the indolent NHL (e.g., relapsed/refractory NHL) is a marginal zone lymphoma (e.g., a relapsed/refractory marginal zone lymphoma).

Further details regarding the methods of treatment and polypeptides comprising a SIRPα D1 domain variant and an Fc domain variant are described below. See also U.S. Pat. No. 10,259,859, the contents of which are incorporated by reference herein in their entirety.

Signal-Regulatory Protein α (SIRP-α) D1 Domain and Variants Thereof

Disclosed herein, in some embodiments, are polypeptides comprising a signal-regulatory protein α (SIRP-α) D1 variant comprising a SIRPα D1 domain, or a fragment thereof, that comprises an amino acid mutation at residue 80 relative to a wild-type SIRPα D1 domain; and at least one additional amino acid mutation relative to a wild-type SIRPα D1 domain at a residue selected from the group consisting of: residue 6, residue 27, residue 31, residue 47, residue 53, residue 54, residue 56, residue 66, and residue 92.

Also disclosed herein, in some embodiments, are polypeptides comprising an Fc domain variants, wherein an Fc domain variant dimer comprises two Fc domain variants, wherein each Fc domain variant independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A.

Signal-regulatory protein α (“SIRP-α” or “SIRP-alpha”) is a transmembrane glycoprotein belonging to the Ig superfamily that is widely expressed on the membrane of myeloid cells. SIRPα interacts with CD47, a protein broadly expressed on many cell types in the body. The interaction of SIRPα with CD47 prevents engulfment of “self” cells, which can otherwise be recognized by the immune system. It has been observed that high CD47 expression on tumor cells can act, in acute myeloid leukemia and several solid tumor cancers, as a negative prognostic factor for survival.

Native SIRPα comprises 3 highly homologous immunoglobulin (Ig)-like extracellular domains—D1, D2, and D3. The SIRPα D1 domain (“D1 domain”) refers to the membrane distal, extracellular domain of SIRPα and mediates binding of SIRPα to CD47. As used herein, the term “SIRPα polypeptide” refers to any SIRPα polypeptide or fragment thereof that is capable of binding to CD47. There are at least ten variants of wild-type human SIRPα. Table 1 shows the amino acid sequences of the D1 domains of the ten naturally occurring wild-type human SIRPα D1 domain variants (SEQ ID NOs: 1-10). In some embodiments, a SIRPα polypeptide comprises a SIRPα D1 domain. In some embodiments, a SIRPα polypeptide comprises a wild-type D1 domain, such as those provided in SEQ ID NOs: 1-10. In some embodiments, a SIRPα polypeptide includes a D2 or D3 domain (or both a D2 and a D3 domain) (see Table 3) of a wild-type human SIRPα.

TABLE 1

Sequences of Wild-Type SIRPα D1 Domains

SEQ ID NO:
Description
Amino Acid Sequence

1
Wild-type D1
EEELQVIQPDKSVLVAAGETATLRCTATSLIPVGPIQ

domain variant 1
WFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNM

DFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSGAG

TELSVRAKPS

2
Wild-type D1
EEELQVIQPDKSVSVAAGESAILHCTVTSLIPVGPIQW

domain variant 2
FRGAGPARELIYNQKEGHFPRVTTVSESTKRENMDF

SISISNITPADAGTYYCVKFRKGSPDTEFKSGAGTELS

VRAKPS

3
Wild-type D1
EEELQVIQPDKSVSVAAGESAILLCTVTSLIPVGPIQW

domain variant 3
FRGAGPARELIYNQKEGHFPRVTTVSESTKRENMDF

SISISNITPADAGTYYCVKFRKGSPDTEFKSGAGTELS

VRAKPS

4
Wild-type D1
EEGLQVIQPDKSVSVAAGESAILHCTATSLIPVGPIQW

domain variant 4
FRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNMDF

SIRIGNITPADAGTYYCVKFRKGSPDDVEFKSGAGTE

LSVRAKPS

5
Wild-type D1
EEELQVIQPDKFVLVAAGETATLRCTATSLIPVGPIQ

domain variant 5
WFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNM

DFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSGAG

TELSVRAKPS

6
Wild-type D1
EEELQVIQPDKSVLVAAGETATLRCTATSLIPVGPIQ

domain variant 6
WFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNM

DFPIRIGNITPADAGTYYCVKFRKGSPDDVEFKSGAG

TELSVRAKPS

7
Wild-type D1
EEELQVIQPDKSVSVAAGESAILHCTVTSLIPVGPIQW

domain variant 7
FRGAGPARELIYNQKEGHFPRVTTVSESTKRENMDF

SISISNITPADAGTYYCVKFRKGSPDTEFKSGAGTELS

VRGKPS

8
Wild-type D1
EEELQVIQPDKSVLVAAGETATLRCTATSLIPVGPIQ

domain variant 8
WFRGAGPARELIYNQKEGHFPRVTTVSESTKRENMD

FSISISNITPADAGTYYCVKFRKGSPDTEFKSGAGTEL

SVRAKPS

9
domain variant 9
EEELQVIQPDKSVLVAAGETATLRCTATSLIPVGPIQ

Wild-type D1
WFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNM

DFSIRISNITPADAGTYYCVKFRKGSPDDVEFKSGAG

TELSVRAKPS

10
Wild-type D1
EEELQVIQPDKSVSVAAGESAILHCTVTSLIPVGPIQW

domain variant 10
FRGAGPARELIYNQKEGHFPRVTTVSESTKRENMDF

SISISNITPADAGTYYCVKFRKGSPDTEFKSGAGTELS

VRAKPS

11
Wild-type pan-D1
EEX₁LQVIQPDKX₂VX₃VAAGEX₄AX₅LX₆CTX₇TSLIP

domain
VGPIQWFRGAGPX₈RELIYNQKEGHFPRVTTVSX₉X₁₀

TKRX₁₁NMDFX₁₂IX₁₃IX₁₄NITPADAGTYYCVKFRKGS

X₁₅X₁₆DX₁₇EFKSGAGTELSVRX₁₈KPS

Amino acid
X₁ is E or G; X₂ is S or F; X₃ is L or S; X₄ is T or S; X₅ is T

substitutions
or I; X₆ is R, H, or L; X₇ is A or V; X₈ is G or A; X₉ is D or

relative to
E; X₁₀ is L or S; X₁₁ is N or E or D; X₁₂ is S or P; X₁₃ is R

SEQ ID NO: 11
or S; X₁₄ is G or S; X₁₅ is P or absent; X₁₆ is D or P; X₁₇ is

V or T; and X₁₈ is A or G

As used herein, the term “SIRPα D1 domain variant” refers to a polypeptide comprising a SIRPα D1 domain or a CD47-binding portion of a SIRPα polypeptide that has a higher affinity to CD47 than wild-type SIRPα. A SIRPα D1 domain variant comprises at least one amino acid substitution, deletion, or insertion (or a combination thereof) relative to a wild-type SIRPα.

In some embodiments, SIRPα D1 domain variants disclosed herein comprise a SIRPα D1 domain or variant thereof. In some embodiments, a SIRPα D1 domain variant comprises one or more amino acid substitutions, insertions, additions, or deletions relative to a wild-type D1 domain shown in SEQ ID NOs: 1-10. Table 2 lists exemplary amino acid substitutions in each SIRPα D1 domain variant (SEQ ID NOs: 13-22). In some embodiments, the SIRPα D1 domain polypeptide or SIRPα D1 domain variant comprises a fragment of the D1 domain. In some embodiments, the SIRPα polypeptide fragment or SIRPα D1 domain variant fragment comprises an amino acid sequence of less than 10 amino acids in length, about 10 amino acids in length, about 20 amino acids in length, about 30 amino acids in length, about 40 amino acids in length, about 50 amino acids in length, about 60 amino acids in length, about 70 amino acids in length, about 80 amino acids in length, about 90 amino acids in length, about 100 amino acids in length, or more than about 100 amino acids in length. In some embodiments, the SIRPα D1 domain fragments retain the ability to bind to CD47.

In some embodiments, a polypeptide of the disclosure comprising a SIRPα D1 domain variant binds with higher binding affinity to CD47 than a wild-type human SIRPα D1 domain. In some embodiments, the SIRPα D1 domain variant binds to human CD47 with at least 1-fold (e.g., at least 1.5-fold, 2-fold, 2.5-fold, 3-fold, 3.5-fold, 4-fold, 5-fold or greater than 5-fold) affinity than the affinity of a naturally occurring D1 domain. In some embodiments, the SIRPα D1 domain variant binds to human CD47 with at least 1-fold (e.g., at least 10-fold, 100-fold, 1000-fold or greater than 1000-fold) affinity than the affinity of a naturally occurring D1 domain.

As used herein, the term “optimized affinity” or “optimized binding affinity” refers to an optimized strength of the binding interaction between a polypeptide disclosed herein, including a SIRPα D1 domain variant, and CD47. For example, in some embodiments, the polypeptide binds primarily or with higher affinity to CD47 on cancer cells and does not substantially bind or binds with lower affinity to CD47 on non-cancer cells. In some embodiments, the binding affinity between the polypeptide and CD47 is optimized such that the interaction does not cause clinically relevant toxicity or decreases toxicity compared to a variant which binds with maximal affinity. In some embodiments, in order to achieve an optimized binding affinity between a polypeptide provided herein and CD47, the polypeptide including a SIRPα D1 domain variant is developed to have a lower binding affinity to CD47 than which is maximally achievable. In some embodiments, the SIRPα D1 domain variants disclosed herein cross react with rodent, non-human primate (NHP), and human CD47.

As used herein, the term “immunogenicity” refers to the property of a protein (e.g., a therapeutic protein) which causes an immune response in the host as though it is a foreign antigen. The immunogenicity of a protein can be assayed in vitro in a variety of different ways, such as through in vitro T-cell proliferation assays.

As used herein, the term “minimal immunogenicity” refers to an immunogenicity of a protein (e.g., a therapeutic protein) that has been modified, e.g., through amino acid substitutions, to be lower (e.g., at least 10%, 25%, 50%, or 100% lower) than the immunogenicity before the amino acid substitutions are introduced (e.g., an unmodified protein). In some embodiments, a protein (e.g., a therapeutic protein) is modified to have minimal immunogenicity and causes no or very little host immune response even though it is a foreign antigen.

In some embodiments, the SIRPα D1 domain variant demonstrates minimal immunogenicity. In some embodiments, a SIRPα polypeptide of the disclosure administered to a subject has the same amino acid sequence as that of the SIRPα polypeptide in a biological sample of the subject, except for amino acid changes which increase affinity of the SIRPα D1 domain variant. In some embodiments, the polypeptide variants disclosed herein lower the risk of side effects compared to anti-CD47 antibodies or wild-type SIRPα. In some embodiments, the polypeptide variants disclosed herein lower the risk of anemia compared to anti-CD47 antibodies or wild-type SIRPα. In some embodiments, the polypeptide variants disclosed herein do not cause acute anemia in rodent or non-human primates (NHP) studies.

Table 2 lists specific amino acid substitutions in a SIRPα D1 domain variant relative to each D1 domain sequence. In some embodiments, a SIRPα D1 domain variant includes one or more (e.g., two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen or more) of the substitutions listed in Table 2. In some embodiments, a SIRPα D1 domain variant includes at most fourteen amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant includes at most ten amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant includes at most seven amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant of the disclosure has at least 90% (e.g., at least 92%, 95%, 97% or greater than 97%) amino acid sequence identity to a sequence of a wild-type D1 domain.

In some embodiments, a SIRPα D1 domain variant is a chimeric SIRPα D1 domain variant that includes a portion of two or more wild-type D1 domains or variants thereof (e.g., a portion of one wild-type D1 domain or variant thereof and a portion of another wild-type D1 domain or variant thereof). In some embodiments, a chimeric SIRPα D1 domain variant includes at least two portions (e.g., three, four, five or more portions) of wild-type D1 domains or variants thereof, wherein each of the portions is from a different wild-type D1 domain. In some embodiments, a chimeric SIRPα D1 domain variant further includes one or more amino acid substitutions listed in Table 2.

TABLE 2

Amino Acid Substitutions in a SIRPα D1 domain variant

SEQ ID NO:
Description
Amino Acid Sequence

13
D1 domain v1
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVE

X₁₄KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 13

14
D1 domain v2
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄K

SGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 14

15
D1 domain v3
EEEX₁QX₂IQPDKSVSVAAGESX₃ILLCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄K

SGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 15

16
D1 domain v4
EEGX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVE

X₁₄KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 16

17
D1 domain v5
EEEX₁QX₂IQPDKFVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVE

X₁₄KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 17

18
D1 domain v6
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFPIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVE

X₁₄KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 18

19
D1 domain v7
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄K

SGAGTELSVRGKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 19

20
D1 domain v8
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁

RENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄

KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 20

21
D1 domain v9
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRISNITPADAGTYYCX₁₂KX₁₃RKGSPDDVE

X₁₄KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 21

22
D1 domain v10
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄K

SGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

relative
X₁₁= K, R; X₁₂= V, I; X₁₃= F, L, V; X₁₄= F, V

to SEQ ID NO: 22

23
Pan D1 domain
EEX₁X₂QX₃IQPDKX₄VX₅VAAGEX₆X₇X₈LX₉CTX₁₀TSLX₁₁

PVGPIQWFRGAGPX₁₂RX₁₃LIYNQX₁₄X₁₅GX₁₆FPRVTT

VSX₁₇X₁₈TX₁₉RX₂₀NMDFX₂₁IX₂₂IX₂₃NITPADAGTYYCX₂₄

KX₂₅RKGSPDX₂₆X₂₇EX₂₈KSGAGTELSVRX₂₉KPS

—
Amino acid
X₁= E, G; X₂= L, I, V; X₃= V, L, I; X₄= S, F; X₅= L, S; X₆= S,

substitutions
T; X₇= A, V; X₈= I, T; X₉= H, R; X₁₀= A, V, I, L; X₁₁= I, T, S,

relative
F; X₁₂ A, G; X₁₃= E, V, L; X₁₄= K, R; X₁₅= E, Q; X₁₆= H, P,

to SEQ ID NO: 23
R; X₁₇= D, E; X₁₈= S, L, T, G; X₁₉= K, R; X₂₀= E, D; X₂₁= S, P;

X₂₂= S, R; X₂₃= S, G; X₂₄= V, I; X₂₅= F, L, V; X₂₆= D or absent;

X₂₇= T, V; X₂₈= F, V; and X₂₉= A, G

In some embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉F PRVTTVSDX₁₀TX₁₁RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVEX₁₄KSGAGTELSV RAKPS (SEQ ID NO: 13), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 1.

In some embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises a sequence of: EEGX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 16), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 4.

In some embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKFVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉F PRVTTVSDX₁₀TX₁₁RNNMDFSIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVEX₁₄KSGAGTELSV RAKPS (SEQ ID NO: 17), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 5.

In some embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFPIRIGNITPADAGTYYCX₁₂KX₁₃RKGSPDDVEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 18), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 6.

In some embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRXLIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRISNITPADAGTYYCX₁₂KX₁₃RKGSPDDVEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 21), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 9.

In any of the aforementioned embodiments, a polypeptide comprises a SIRPα D1 domain variant that comprises the sequence of any one of SEQ ID NOs: 13, 16-18, and 21, wherein X₁is L, I, or V. In any of the aforementioned embodiments, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is A, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R In any of the aforementioned embodiments, X₁₀is L, T, or G. In any of the aforementioned embodiments, X₁₁is K or R In any of the aforementioned embodiments, X₁₂is V or I. In any of the aforementioned embodiments, X₁₃is F, L, V. In any of the aforementioned embodiments, X₁₄is F or V. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than six amino acid substitutions relative to the wild-type SIRPα D1 domain that comprises the sequence of any one of SEQ ID NOs: 1, 4-6, and 9.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain that comprises the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain that comprises the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain that comprises the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a KD between about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISNITPADAGTYYCX₂KX₁₃RKGSPDTEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 14), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 2.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILLCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 15), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 3.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄KSGAGTELSVRGKPS (SEQ ID NO: 19), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 7.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant that comprises a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISNITPADAGTYYCX₁₂KX₁₃RKGSPDTEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 22), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain that comprises the sequence of SEQ ID NO: 10.

In any of the aforementioned embodiments in this aspect of the disclosure, the polypeptide comprises the sequence of any one of SEQ ID NOs: 14, 15, 19, and 22, wherein X₁is L, I, or V. In any of the aforementioned embodiments, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is V, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R In any of the aforementioned embodiments, X₁₀is S, T, or G. In any of the aforementioned embodiments, X₁₁is K or R In any of the aforementioned embodiments, X₁₂is V or I. In any of the aforementioned embodiments, X₁₃is F, L, or V. In any of the aforementioned embodiments, X₁₄is F or V. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than six amino acid substitutions relative to the wild-type SIRPα D1 domain that comprises the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉F PRVTTVSEX₁₀TX₁₁RENMDFSISISNITPADAGTYYCX₁₂KX₃RKGSPDTEX₁₄KSGAGTELSVRAKPS (SEQ ID NO: 20), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is V or I; X₁₃is F, L, or V; and X₁₄is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 20, wherein X₁is L, I, or V. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is A, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R. In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R. In any of the aforementioned embodiments, X₁₀is S, T, or G. In any of the aforementioned embodiments, X₁₁is K or R. In any of the aforementioned embodiments, X₁₂is V or I. In any of the aforementioned embodiments, X₁₃is F, L, or V. In any of the aforementioned embodiments, X₁₄is F or V. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than six amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEX₁X₂QX₃IQPDKX₄VX₅VAAGEX₆X₇XSLX₉CTX₁₀TSLX₁₁PVGPIQWFRGAGPX₁₂RX₁₃LIYNQX₁₄X₁₅GX₁₆FPRVTTVSX₁₇X₁₈TX₁₉RX₂₀DNMDFX₂₁IX₂₂IX₂₃NITPADAGTYYCX₂₄KX₂₅RKGSPDX₂₆X₂₇EX₂₈KSGAGTELSVRX₂₉KPS (SEQ ID NO: 23), wherein X₁is E or G; X₂is L, I, or V; X₃is V, L, or, I; X₄is S or F; X₅is L or S; X₆is S or T; X₇is A or V; X₈is I or T; X₉is H or R; X₁₀is A, V, I, or L; X₁₁is I, T, S, or F; X₁₂is A or G; X₁₃is E, V, or L; X₁₄is K or R; X₁₅is E or Q; X₁₆is H, P, or R; X₁₇is D or E; X₁₈is S, L, T, or G; X₁₉is K or R X₂₀is E or D; X₂₁is S or P; X is S or R; X₂₃is S or G; X₂₄is V or I; X₂₅is F, L, V; X₂₆is D or absent; X₂₇is T or V; X₂₈is F or V; and X₂₉is A or G; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10.

In any of the aforementioned embodiments in this aspect of the disclosure, X₂is L, I, or V. In any of the aforementioned embodiments, X₃is V, L, or, I. In any of the aforementioned embodiments, X₄is S or F. In any of the aforementioned embodiments, X₅is L or S. In any of the aforementioned embodiments, X₆is S or T. In any of the aforementioned embodiments, X₇is A or V. In any of the aforementioned embodiments, X₈is I or T. In any of the aforementioned embodiments, X₉is H or R. In any of the aforementioned embodiments, X₁₀is A, V, I, or L. In any of the aforementioned embodiments, X₁₁is I, T, S, or F. In any of the aforementioned embodiments, X₁₂is A or G. In any of the aforementioned embodiments, X₁₃is E, V, or L. In any of the aforementioned embodiments, X₁₄is K or R. In any of the aforementioned embodiments, X₁₅is E or Q. In any of the aforementioned embodiments, X₁₆is H, P, or R. In any of the aforementioned embodiments, X₁₇is D or E. In any of the aforementioned embodiments, X₁₈is S, L, T, or G. In any of the aforementioned embodiments, X₁₉is K or R. In any of the aforementioned embodiments, X₂₀is E or D. In any of the aforementioned embodiments, X₂₁is S or P. In any of the aforementioned embodiments, X₂₂is S or R. In any of the aforementioned embodiments, X₂₃is S or G. In any of the aforementioned embodiments, X₂₄is V or I. In any of the aforementioned embodiments, X₂₅is F, L, V. In any of the aforementioned embodiments, X₂₆is D or absent. In any of the aforementioned embodiments, X₂₇is T or V. In any of the aforementioned embodiments, X₂₈is F or V. In any of the aforementioned embodiments, X₂₉is A or G. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than six amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide of the disclosure including a SIRPα D1 domain variant further comprises a D2 domain having the sequence of SEQ ID NO: 24, a D3 domain having the sequence of SEQ ID NO: 25, or a D2 domain having the sequence of SEQ ID NO: 24 and a D3 domain having the sequence of SEQ ID NO: 25 of a wild-type human SIRPα as shown in Table 3. In some embodiments, the SIRPα D1 domain variant further comprises a fragment or variant of a D2 domain or a fragment or variant of a D3 domain. In some embodiments, the SIRPα D1 domain variant further comprises a fragment or variant of a D2 domain and a fragment or variant of a D3 domain. In some embodiments, a SIRPα D1 domain variant is joined to a D2 or D3 domain by way of a linker. In some embodiments, a SIRPα D1 domain variant is joined to a D2 and D3 domain by way of a linker.

TABLE 3

Amino Acid Sequences of SIRPα D2 and D3 Domains

SEQ ID NO:
Description
Amino Acid Sequence

24
SIRPα D2
APVVSGPAARATPQHTVSFTCESHGF

domain
SPRDITLKWFKNGNELSDFQTNVDPV

GESVSYSIHSTAKVVLTREDVHSQVI

CEVAHVTLQGDPLRGTANLSETIR

25
SIRPα D3
VPPTLEVTQQPVRAENQVNVTCQVR

domain
KFYPQRLQLTWLENGNVSRTETAST

VTENKDGTYNWMSWLLVNVSAHRDD

VKLTCQVEHDGQPAVSKSHDLKVS

In some embodiments, a polypeptide of the disclosure including a SIRPα D1 domain variant is attached to an Fc domain variant in order to improve the pharmacokinetic properties of the polypeptide, e.g., increase serum half-life. In some embodiments, a SIRPα D1 domain variant is attached to an Fc domain variant that is unable to dimerize. In some embodiments, Fc domain variants serve to increase the serum half-life of the polypeptides described herein. In some embodiments, a polypeptide of the disclosure including a SIRPα D1 domain variant does not include the sequence of any one of SEQ ID NOs: 26-36 shown in Table 4.

TABLE 4

SEQ

ID

NO:
Amino Acid Sequence

26
EEELQVIQPDKSVSVAAGESAILHCTITSLIPVGPIQWFRGAGPAR

ELIYNQREGHFPRVTTVSETTRRENMDFSISISNITPADAGTYYCV

KFRKGSPDTEVKSGAGTELSVRAKPS

27
EEEVQVIQPDKSVSVAAGESAILHCTLTSLIPVGPIQWFRGAGPAR

VLIYNQRQGHFPRVTTVSEGTRRENMDFSISISNITPADAGTYYCI

KFRKGSPDTEFKSGAGTELSVRAKPS

28
EEEVQIIQPDKSVSVAAGESVILHCTITSLTPVGPIQWFRGAGPAR

LLIYNQREGPFPRVTTVSETTRRENMDFSISISNITPADAGTYYCV

KLRKGSPDTEFKSGAGTELSVRAKPS

29
EEELQIIQPDKSVSVAAGESAILHCTITSLSPVGPIQWFRGAGPAR

VLIYNQRQGPFPRVTTVSEGTKRENMDFSISISNITPADAGTYYCI

KLRKGSPDTEFKSGAGTELSVRAKPS

30
EEEIQVIQPDKSVSVAAGESVIIHCTVTSLFPVGPIQWFRGAGPAR

VLIYNQRQGRFPRVTTVSEGTKRENMDFSISISNITPADAGTYYCV

KVRKGSPDTEVKSGAGTELSVRAKPS

31
EEEVQIIQPDKSVSVAAGESIILHCTVTSLFPVGPIQWFRGAGPAR

VLIYNQREGRFPRVTTVSEGTRRENMDFSISISNITPADAGTYYCI

KLRKGSPDTEFKSGAGTELSVRAKPS

32
EEEVQLIQPDKSVSVAAGESAILHCTVTSLFPVGPIQWFRGAGPAR

VLIYNQREGPFPRVTTVSEGTKRENMDFSISISNITPADAGTYYCI

KFRKGSPDTEVKSGAGTELSVRAKPS

33
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPG

RVLIYNQRQGPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYY

CIKFRKGSPDDVEFKSGAGTELSVRAKPS

34
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPA

RLLIYNQRQGPFPRVTTVSETTKRENMDFSISISNITPADAGTYY

CVKFRKGSPDTEFKSGAGTELSVRAKPS

35
EEEVQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPA

RVLIYNQKQGPFPRVTTISETTRRENMDFSISISNITPADAGTYY

CIKFRKGSPDTEFKSGAGTELSVRAKPS

36
EEELQIIQPDKSVSVAAGESAILHCTITSLTPVGPIQWFRGAGPA

RVLIYNQRQGPFPRVTTVSEGTRRENMDFSISISNITPADAGTYY

CIKFRKGSPDTEVKSGAGTELSVRAKPS

In some embodiments, the polypeptides and polypeptide constructs described herein are utilized in vitro for binding assays, such as immune assays. For example, in some embodiments, the polypeptides and polypeptide constructs described herein are utilized in liquid phase or bound to a solid phase carrier. In some embodiments, polypeptides utilized for immunoassays are detectably labeled in various ways.

In some embodiments, polypeptides and polypeptide constructs described herein are bound to various carriers and used to detect the presence of specific antigen expressing cells. Examples of carriers include glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, agaroses, and magnetite. The nature of the carrier can be either soluble or insoluble.

Various different labels and methods of labeling are known. Examples of labels include enzymes, radioisotopes, fluorescent compounds, colloidal metals, chemiluminescent compounds, and bio-luminescent compounds. Various techniques for binding labels to polypeptides disclosed herein are available.

In some embodiments, the polypeptides are coupled to low molecular weight haptens. These haptens are then specifically detected by means of a second reaction. For example, in some embodiments, the hapten biotin is used with avidin or the haptens dinitrophenol, pyridoxal, or fluorescein are detected with specific anti-hapten antibodies (e.g., anti-dinitrophenol antibodies, anti-pyridoxal antibodies, and anti-fluorescein antibodies respectively).

SIRPα D1 Domain Variants with Altered Glycosylation Patterns

Disclosed herein, in some embodiments, are polypeptides comprising a signal-regulatory protein a (SIRP-α) D1 variant comprising a SIRPα D1 domain, or a fragment thereof, having an amino acid mutation at residue 80 relative to a wild-type SIRPα D1 domain; and at least one additional amino acid mutation relative to a wild-type SIRPα D1 domain at a residue selected from the group consisting of: residue 6, residue 27, residue 31, residue 47, residue 53, residue 54, residue 56, residue 66, and residue 92.

Also disclosed herein, in some embodiments, are polypeptides comprising an Fc domain variant, wherein an Fc domain variant dimer comprises two Fc domain variants, wherein each Fc domain variant independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A.

In some embodiments, a polypeptide in a composition disclosed herein comprises a SIRPα D1 domain variant that has reduced or minimal glycosylation. The D1 domain of each of the ten wild-type human SIRPα proteins (SEQ ID NOs: 1-10 in Table 1) contains a single potential N-linked glycosylation site at amino acid N80 in the sequence N80ITP. Expression of a SIRPα D1 domain in Chinese Hamster Ovary (CHO) cells results in a major band of 16 kDa (non-glycosylated) and a minor band of higher molecular weight that was removed by Endo Hf. Endo Hf is a recombinant protein fusion of Endoglycosidase H and maltose binding protein. Endo Hf cleaves within the chitobiose core of high mannose and some hybrid oligosaccharides from N-linked glycoproteins. This implies that a proline at amino acid position 83 can reduce the efficiency of glycosylation, leading to a protein with different degrees of glycosylation and therefore heterogeneity. For drug development, heterogeneity can give rise to challenges in process development. Therefore, to investigate the possibility of generating homogenous, non-glycosylated forms of SIRPα D1 domain variants, in some embodiments, amino acid N80 of a SIRPα D1 variant is mutated to Ala. In some embodiments, to make a non-glycosylated, SIRPα D1 domain variant, amino acid N80 in a SIRPα D1 domain variant is replaced by any amino acid, including any naturally and non-naturally occurring amino acid, e.g., N80A and N80Q. In some embodiments, a SIRPα D1 domain variant comprises an N80A mutation and at least 1 additional mutation (e.g., at least 2, 3, 4, 5, 6, 7, 8, 9, or 10 additional mutations or more). In some embodiments, the additional mutation is in the CD47 binding site. In some embodiments, the additional mutation is in the hydrophobic core of the D1 domain.

In some embodiments, a polypeptide in a composition disclosed herein includes a SIRPα D1 domain variant that has increased glycosylation relative to a wild-type SIRPα D1 domain. Another option to increase homogeneity of the final product is to enhance the efficiency of glycosylation at amino acid N80 and generate SIRPα D1 domain variants with increased glycosylation relative to a wild-type. In some embodiments, the amino acid P83 in the sequence NITP83 affects the degree of glycosylation at amino acid N80. In some embodiments, changing P83 to any amino acid increases the efficiency of glycosylation at N80. In some embodiments, amino acid P83 in a SIRPα D1 domain variant is replaced by any amino acid, including naturally and non-naturally amino acids, e.g., P83V, P83A, P83I, and P83 L. In some embodiments, a polypeptide of the disclosure is expressed in a cell that is optimized not to glycosylate proteins that are expressed by such cell, for example by genetic engineering of the cell line (e.g., genetically engineered yeast or mammalian host) or modifications of cell culture conditions such as addition of kifunensine or by using a naturally non-glycosylating host such as a prokaryote (E. coli, etc.).

Table 5 lists specific amino acid substitutions in a SIRPα D1 domain variant relative to each D1 domain variant sequence. In some embodiments, a SIRPα D1 domain variant includes one or more (e.g., two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen or more) of the substitutions listed in Table 5. In some embodiments, the SIRPα D1 domain variants are not glycosylated or are minimally glycosylated. In some embodiments, the SIRPα D1 domain variants are fully glycosylated or almost fully glycosylated. In some embodiments, a SIRPα D1 domain variant includes at most fourteen amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant includes at most ten amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant includes at most seven amino acid substitutions relative to a wild-type D1 domain. In some embodiments, a SIRPα D1 domain variant of the disclosure has at least 90% (e.g., at least 92%, 95%, 97% or greater than 97%) amino acid sequence identity to a sequence of a wild-type D1 domain.

TABLE 5

Amino Acid Substitutions in a SIRPα Dl domain variant

SEQ

ID NO:
Description
Amino Acid Sequence

37
D1 domain v1
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDD

VEX₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

to SEQ ID NO: 37
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

38
D1 domain v2
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆

KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

to SEQ ID NO: 38
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

39
D1 domain v3
EEEX₁QX₂IQPDKSVSVAAGESX₃ILLCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆

KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

to SEQ ID NO: 39
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

40
D1 domain v4
EEGX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDD

VEX₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

to SEQ ID NO: 40
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

41
D1 domain v5
EEEX₁QX₂IQPDKFVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDD

VEX₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

to SEQ ID NO: 41
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

42
D1 domain v6
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFPIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDD

VEX₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

to SEQ ID NO: 42
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

43
D1 domain v7
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆

KSGAGTELSVRGKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

to SEQ ID NO: 43
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

44
D1 domain v8
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁

RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTE

X₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

to SEQ ID NO: 44
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

45
D1 domain v9
EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGP

IQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁

RNNMDFSIRISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDD

VEX₁₆KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= A, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= L, T, G;

to SEQ ID NO: 45
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

46
D1 domain v10
EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPI

QWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁R

ENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆

KSGAGTELSVRAKPS

—
Amino acid
X₁= L, I, V; X₂= V, L, I; X₃= A, V; X₄= V, I, L; X₅= I, T, S, F;

substitutions relative
X₆= E, V, L; X₇= K, R; X₈= E, Q; X₉= H, P, R; X₁₀= S, T, G;

to SEQ ID NO: 46
X₁₁= K, R; X₁₂= N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S,

T, V, W, Y; X₁₃= P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R,

S, T, V, W, Y; X₁₄= V, I; X₁₅= F, L, V; X₁₆= F, V

47
Pan D1 domain
EEX₁X₂QX₃IQPDKX₄VX₅VAAGEX₆X₇X₈LX₉CTX₁₀TSLX₁₁

PVGPIQWFRGAGPX₁₂RX₁₃LIYNQX₁₄X₁₅GX₁₆FPRVTT

VSX₁₇X₁₈TX₁₉RX₂₀NMDFX₂₁IX₂₂IX₂₃X₂₄ITX₂₅ADAGTYY

CX₂₆KX₂₇RKGSPDX₂₈X₂₉EX₃₀KSGAGTELSVRX₃₁KPS

—
Amino acid
X₁= E, G; X₂= L, I, V; X₃= V, L, I; X₄= S, F; X₅= L, S; X₆= S,

substitutions relative
T; X₇= A, V; X₈= I, T; X₉= H, R, L; X₁₀= A, V, I, L; X₁₁= I, T,

to SEQ ID NO: 47
S, F; X₁₂= A, G; X₁₃= E, V, L; X₁₄= K, R; X₁₅= E, Q; X₁₆= H, P,

R; X₁₇= D, E; X₁₈= S, L, T, G; X₁₉= K, R; X₂₀= E, N; X₂₁= S, P;

X₂₂= S, R; X₂₃= S, G; X₂₄= any amino acid; X₂₅= any amino

acid; X₂₆= V, I; X₂₇= F, L, V; X₂₈= D or absent; X₂₉= T, V;

X₃₀= F, V; and X₃₁= A, G

48
Pan D1 domain
EEELQX₁IQPDKSVX₂VAAGEX₃AX₄LX₅CTX₆TSLX₇PV

GPIQWFRGAGPX₈RX₉LIYNQX₁₀X₁₁GX₁₂FPRVTTVSX₁₃

X₁₄TKRX₁₅NMDFSIX₁₆IX₁₇X₁₈ITPADAGTYYCX₁₉KFRK

GX₂₀X₂₁X₂₂DX₂₃EFKSGAGTELSVRAKPS

—
Amino acid
X₁= V, I; X₂= L, S; X₃= T, S; X₄= T, I; X₅= R, H; X₆= A, V,

substitutions relative
I; X₇= I, R, Y, K, F; X₈= G, A; X₉= E, V; X₁₀= K, R; X₁₁=

to SEQ ID NO: 48
E, D, Q; X₁₂= H, P; X₁₃= D, E; X₁₄= S, L, T; X₁₅= N, E; X₁₆=

R, S; X₁₇= G, S; X₁₈= N, A; X₁₉= V, I; X₂₀= S, I, M; X₂₁= P

or absent; X₂₂= D, P; and X₂₃= V, T

49
Pan D1 domain
EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQ

WFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNN

MDFSIRIGX₉ITPADAGTYYCX₁₀KFRKGSPDDVEFKSG

AGTELSVRAKPS

—
Amino acid
X₁= V, I, L; X₂= A, I, V, L; X₃= I, F, S, T; X₄= E, V, L; X₅= K,

substitutions relative
R; X₆= E, Q; X₇= H, P, R; X₈= L, T, S, G; X₉= A; and X₁₀= V,

to SEQ ID NO: 49
I

50
Pan D1 domain
EEELQX₁IQPDKSVSVAAGESAILHCTX₂TSLX₃PVGPIQ

WFRGAGPARX₄LIYNQX₅X₆GX₇FPRVTTVSEX₈TKREN

MDFSISISX₉ITPADAGTYYCX₁₀KFRKGSPDTEFKSGAG

TELSVRAKPS

—
Amino acid
X₁= V, I; X₂= V, I; X₃= I, F; X₄= E, V; X₅= K, R; X₆= E, Q;

substitutions relative
X₇= H, P; X₈= S, T; X₉= N, A; and X₁₀= V, I

to SEQ ID NO: 50

51
Pan D1 domain
EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQ

WFRGAGPGRX₄LIYNQX₅EGX₆FPRVTTVSDX₇TKRNN

MDFSIRIGX₈ITPADAGTYYCX₉KFRKGSPDDVEFKSGA

GTELSVRAKPS

—
Amino acid
X₁= V, I; X₂= A, I; X₃= I, F; X₄= E, V; X₅= K, R; X₆= H, P;

substitutions relative
X₇= L, T; X₈= N, A; and X₉= V, I

to SEQ ID NO: 51

52
Pan D1 domain
EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQ

WFRGAGPGRELIYNQX₄EGX₅FPRVTTVSDX₆TKRNNM

DFSIRIGX₇ITPADAGTYYCVKFRKGSPDDVEFKSGAGT

ELSVRAKPS

—
Amino acid
X₁= V, L, I; X₂= A, I, L; X₃= I, T, S, F; X₄= K, R; X₅= H, P, R;

substitutions relative
X₆= L, T, G; and X₇= N, A

to SEQ ID NO: 52

212
Pan D1 domain
EEELQX₁IQPDKSVSVAAGESAILHCTX₂TSLX₃PVGPIQ

WFRGAGPARELIYNQX₄EGX₅FPRVTTVSEX₆TKRENM

DFSISISX₇ITPADAGTYYCVKFRKGSPDTEFKSGAGTE

LSVRAKPS

—
Amino acid
X₁= V, L, I; X₂= V, I, L; X₃= I, T, S, F; X₄= K, R; X₅= H, P, R;

substitutions relative
X₆= S, T, G; and X₇= N, A

to SEQ ID NO: 212

218
Pan D1 domain
EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQ

WFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNN

MDFSIRIGX₉X₁₀X₁₁X₁₂ADAGTYYCX₁₃KFRKGSPDDVE

FKSGAGTELSVRAKPS

—
Amino acid
X₁= V, L, or I; X₂ = A, V, L, or I; X₃= I, S, T, or F; X₄= E, L,

substitutions relative
or V; X₅= K or R; X₆= E or Q; X₇= H, R or P; X₈= S, G, L or T,

to SEQ ID NO: 218
X₉= any amino acid; X₁₀= any amino acid; X₁₁= any amino

acid; X₁₂= any amino acid; and X₁₃= V or I

219
Pan D1 domain
EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQ

WFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNN

MDFSIRIGX₉ITX₁₀ADAGTYYCX₁₁KFRKGSPDDVEFKS

GAGTELSVRAKPS

—
Amino acid
X₁= V, L or I; X₂= A, V, L, or I; X₃= I, S, T or F; X₄= E, L, or

substitutions relative
V; X₅= K or R; X₆= E or Q; X₇= H, R or P; X₈= S, G, L, or T;

to SEQ ID NO: 219
X₉= N; X₁₀= any amino acid other than P; and X₁₁= V or I

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDDVEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 37), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 1.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEGX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDDVEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 40), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 4.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKFVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRIGX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDDVEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 41), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 5.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFPIRIGX₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDDVEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 42), and wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 6.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPGRX₆LIYNQX₇X₈GX₉FPRVTTVSDX₁₀TX₁₁RNNMDFSIRISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDDVEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 45), and wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is L, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 9.

In any of the aforementioned embodiments in this aspect of the disclosure, a polypeptide includes a SIRPα D1 domain variant having a sequence of any one of SEQ ID NOs: 37, 40-42, and 45, wherein X₁is L, I, or V. In any of the aforementioned embodiments, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is A, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R. In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R. In any of the aforementioned embodiments, X₁₀is L, T, or G. In any of the aforementioned embodiments, X₁₁is K or R. In any of the aforementioned embodiments, X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₄is V or I. In any of the aforementioned embodiments, X₁₅is F, L, V. In any of the aforementioned embodiments, X₁₆is F or V.

In some embodiments, a polypeptide provided herein includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, the polypeptide provided herein includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1, 4-6, and 9.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1, 4-6, and 9. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 38), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 2.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILLCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 39), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 3.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆KSGAGTELSVRGKPS (SEQ ID NO: 43), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 7.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVSVAAGESX₃ILHCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 46), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is V, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; Xia is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 10.

In any of the aforementioned embodiments in this aspect of the disclosure, a polypeptide includes a SIRPα D1 domain variant having a sequence of any one of SEQ ID NOs: 38, 39, 43, and 46, wherein X₁is L, I, or V. In any of the aforementioned embodiments, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is V, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R. In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R. In any of the aforementioned embodiments, X₁₀is S, T, or G. In any of the aforementioned embodiments, X₁₁is K or R. In any of the aforementioned embodiments, X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₄is V or I. In any of the aforementioned embodiments, X₁₅is F, L, or V. In any of the aforementioned embodiments, X₁₆is F or V.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10. In some embodiments, a polypeptide includes a SIRPα D1 domain variant having no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 2, 3, 7, and 10.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEEX₁QX₂IQPDKSVLVAAGETX₃TLRCTX₄TSLX₅PVGPIQWFRGAGPARX₆LIYNQX₇X₈GX₉FPRVTTVSEX₁₀TX₁₁RENMDFSISISX₁₂ITX₁₃ADAGTYYCX₁₄KX₁₅RKGSPDTEX₁₆KSGAGTELSVRAKPS (SEQ ID NO: 44), wherein X₁is L, I, or V; X₂is V, L, or, I; X₃is A or V; X₄is A, I, or L; X₅is I, T, S, or F; X₆is E, V, or L; X₇is K or R; X₈is E or Q; X₉is H, P, or R; X₁₀is S, T, or G; X₁₁is K or R; X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; X₁₄is V or I; X₁₅is F, L, or V; and X₁₆is F or V; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 44, wherein X₁is L, I, or V. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is V, L, or, I. In any of the aforementioned embodiments, X₃is A or V. In any of the aforementioned embodiments, X₄is A, I, or L. In any of the aforementioned embodiments, X₅is I, T, S, or F. In any of the aforementioned embodiments, X₆is E, V, or L. In any of the aforementioned embodiments, X₇is K or R. In any of the aforementioned embodiments, X₈is E or Q. In any of the aforementioned embodiments, X₉is H, P, or R. In any of the aforementioned embodiments, X₁₀is S, T, or G. In any of the aforementioned embodiments, X₁₁is K or R. In any of the aforementioned embodiments, X₁₂is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₃is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₁₄is V or I. In any of the aforementioned embodiments, X₁₅is F, L, or V. In any of the aforementioned embodiments, X₁₆is F or V.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8. In some embodiments, a polypeptide includes a SIRPα D1 domain variant having no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of SEQ ID NO: 8.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEX₁X₂QX₃IQPDKX₄VX₅VAAGEX₆X₇XSLX₉CTX₁₀TSLX₁₁PVGPIQWFRGAGPX₁₂RX₁₃LIYNQX₁₄X₁₅GX₁₆FPRVTTVSX₁₇X₁₈TX₁₉RX₂₀DNMDFX₂₁IX₂₁IX₂₃X₂₄ITX₂₅ADAGTYYCX₂₆KX₂₇RKGSPDX₂₈X₂₉EX₃₀KSGAGTELSVRX₃₁KPS (SEQ ID NO: 47), wherein X₁is E or G; X₂is L, I, or V; X₃is V, L, or, I; X₄is S or F; X₅is L or S; X₆is S or T; X₇is A or V; X₈is I or T; X₉is H, R, or L; X₁₀is A, V, I, or L; X₁₁is I, T, S, or F; X₁₂is A or G; X₁₃is E, V, or L; X₁₄is K or R; X₁₅is E or Q; X₁₆is H, P, or R; X₁₇is D or E; X₁₈is S, L, T, or G; X₁₉is K or R X₂₀is E or N; X₂₁is S or P; X₂₂is S or R; X₂₃is S or G; X₂₄is any amino acid; X₂₅is any amino acid; X₂₆is V or I; X₂₇is F, L, V; X₂₈is D or absent; X₂₉is T or V; X₃₀is F or V; and X₃₁is A or G; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 47, wherein X₁is E or G. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is L, I, or V. In any of the aforementioned embodiments, X₃is V, L, or, I. In any of the aforementioned embodiments, X₄is S or F. In any of the aforementioned embodiments, X₅is L or S. In any of the aforementioned embodiments, X₆is S or T. In any of the aforementioned embodiments, X₇is A or V. In any of the aforementioned embodiments, X₈is I or T. In any of the aforementioned embodiments, X₉is H or R. In any of the aforementioned embodiments, X₁₀is A, V, I, or L. In any of the aforementioned embodiments, X₁₁is I, T, S, or F. In any of the aforementioned embodiments, X₁₂is A or G. In any of the aforementioned embodiments, X₁₃is E, V, or L. In any of the aforementioned embodiments, X₁₄is K or R. In any of the aforementioned embodiments, X₁₅is E or Q. In any of the aforementioned embodiments, X₁₆is H, P, or R. In any of the aforementioned embodiments, X₁₇is D or E. In any of the aforementioned embodiments, X₁₈is S, L, T, or G. In any of the aforementioned embodiments, X₁₉is K or R. In any of the aforementioned embodiments, X₂₀is E or N. In any of the aforementioned embodiments, X₂₁is S or P. In any of the aforementioned embodiments, X₂₂is S or R. In any of the aforementioned embodiments, X₂₃is S or G. In any of the aforementioned embodiments, X₂₄is N, A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₂₅is P, A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y. In any of the aforementioned embodiments, X₂₆is V or I. In any of the aforementioned embodiments, X₂₇is F, L, V. In any of the aforementioned embodiments, X₂₈is D or absent. In any of the aforementioned embodiments, X₂₉is T or V. In any of the aforementioned embodiments, X₃₀is F or V. In any of the aforementioned embodiments, X₃₁is A or G.

In some embodiments, the polypeptide of this aspect of the disclosure includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NOs: 1-10. In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In some embodiments, a polypeptide includes a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVX₂VAAGEX₃AX₄LX₅CTX₆TSLX₇PVGPIQWFRGAGPX₈RX₉LIYNQX₁₀X₁₁GX₁₂FPRVTTVSX₁₃X₁₄TKRX₁₅NMDFSIX₁₆IX₁₇X₁₈ITPADAGTYYCX₁₉KFRKGX₂₀X₂₁X₂₂DX₂₃EFKSGAGTELSVRAKPS (SEQ ID NO: 48), wherein X₁is V or I; X₂is L or S; X₃is T or S; X₄is T or I; X₅is R or H; X₆is A, V, or I; X₇is I, R, Y, K or F; X₈is G or A; X₉is E or V; X₁₀is K or R; X₁₁is E, D or Q; X₁₂is H or P; X₁₃is D or E; X₁₄is S, L or T; X₁₅is N or E; X₁₆is R or S; X₁₇is G or S; X₁₈is N or A; X₁₉is V or I; X₂₀is S, I or M; X₂₁is P or absent; X₂₂is D or P; and X₂₃is V or T, or a fragment thereof.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNNMDFSIRIGX₉ITPADAGTYYCX₁₀KFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 49), wherein X₁is V, L, or I; X₂is A, I, V, or L; X₃is I, F, S, or T; X₄is E, V, or L; X₅is K or R X₆is E or Q; X₇is H, P, or R; X₈is L, T, S, or G; X₉is A; and X₁₀is V or I; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 49, wherein X₁is V, L or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is A, I, V, or L. In any of the aforementioned embodiments, X₃is I, F, S, or T. In any of the aforementioned embodiments, X₄is E, V, or L. In any of the aforementioned embodiments, X₅is K or R. In any of the aforementioned embodiments, X₆is E or Q. In any of the aforementioned embodiments, X₇is H, P, or R. In any of the aforementioned embodiments, X₈is L, T, S or G. In any of the aforementioned embodiments, X₉is A. In any of the aforementioned embodiments, X₁₀is V or I.

In some embodiments, the polypeptide comprises a SIRPα D1 domain that comprises at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to SEQ ID NO: 49, wherein each of X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈, X₉, and X₁₀are not a wild-type amino acid.

In some embodiments, the polypeptide of this aspect of the disclosure includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVSVAAGESAILHCTX₂TSLX₃PVGPIQWFRGAGPARX₄LIYNQX₅X₆GX₇FPR VTTVSEX₈TKRENMDFSISISX₉ITPADAGTYYCX₁₀KFRKGSPDTEFKSGAGTELSVRAKPS, (SEQ ID NO: 50), wherein X₁is V or I; X₂is V or I; X₃is I or F; X₄is E or V; X₅is K or R; X₆is E or Q; X₇is H or P; X₈is S or T; X₉is N or A; and X₁₀V or I; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 50, wherein X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is V or I. In any of the aforementioned embodiments, X₃is I or F. In any of the aforementioned embodiments, X₄is E or V. In any of the aforementioned embodiments, X₅is K or R. In any of the aforementioned embodiments, X₆is E or Q. In any of the aforementioned embodiments, X₇is H or P. In any of the aforementioned embodiments, X₈is S or R. In any of the aforementioned embodiments, X₉is N or A. In any of the aforementioned embodiments, X₁₀is V or I.

In some embodiments, the polypeptide comprises a SIRPα D1 domain that comprises at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to SEQ ID NO: 50, wherein each of X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈, X₉, and X₁₀is not a wild-type amino acid.

In some embodiments, the polypeptide of this aspect of the disclosure includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRX₄LIYNQX₅EGX₆FPRVTTVSDX₇TKRNNMDFSIRIGX₈ITPADAGTYYCX₉KFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 221), wherein X₁is V or I; X₂is A or I; X₃is I or F; X₄is E or V; X₅is K or R; X₆is H or P; X₇is L or T; X₈is N or A; and X₉is V or I; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 51, wherein X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is A or I. In any of the aforementioned embodiments, X₃is I or F. In any of the aforementioned embodiments, X₄is E or V. In any of the aforementioned embodiments, X₅is K or R. In any of the aforementioned embodiments, X₆is H or P. In any of the aforementioned embodiments, X₇is L or T. In any of the aforementioned embodiments, X₈is N or A. In any of the aforementioned embodiments, X₉is V or I. In some embodiments, X₄is not V.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 51, wherein X₈is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₈is A and X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₈is A and X₂is A or I. In any of the aforementioned embodiments, X₈is A and X₃is I or F. In any of the aforementioned embodiments, X₈is A and X₄is E or V. In some embodiments, X₄is not V. In any of the aforementioned embodiments, X₈is A and X₅is K or R. In any of the aforementioned embodiments, X₈is A and X₆is H or P. In any of the aforementioned embodiments, X₈is A and X₇is A or V. In any of the aforementioned embodiments, X₈is A and X₉is V or I.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 51, wherein X₈is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₈is A and X₁is I. In any of the aforementioned embodiments in this aspect of the disclosure, X₈is A and X₂is I. In any of the aforementioned embodiments, X₈is A and X₃is F. In any of the aforementioned embodiments, X₈is A and X₄is V. In any of the aforementioned embodiments, X₈is A and X₅is R. In any of the aforementioned embodiments, X₈is A and X₆is P. In any of the aforementioned embodiments, X₈is A and X₇is T. In any of the aforementioned embodiments, X₈is A and X₉is I.

In some embodiments, the polypeptide comprises a SIRPα D1 domain variant that comprises at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to SEQ ID NO: 51, wherein each of X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈, and X₉is not a wild-type amino acid.

In some embodiments, the polypeptide of this aspect of the disclosure comprises no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, the polypeptide of this aspect of the disclosure comprises no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRELIYNQX₄EGX₅FPRVTTVSDX₆TKRNNMDFSIRIGX₇ITPADAGTYYCVKFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 222), wherein X₁is V, L, or I; X₂is A, I, or L; X₃is I, T, S, or F; X₄is K or R; X₅is H or P; X₆is L, T, or G; X₇is N or A; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having a sequence according to SEQ ID NO: 1.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 222, wherein X₁is V, L, or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is A, I, or L. In any of the aforementioned embodiments, X₃is I, T, S, or F. In any of the aforementioned embodiments, X₄is K or R. In any of the aforementioned embodiments, X₅is H or P. In any of the aforementioned embodiments, X₆is L, T, or G. In any of the aforementioned embodiments, X₇is N or A.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 222, wherein X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is A or I. In any of the aforementioned embodiments, X₃is I or F. In any of the aforementioned embodiments, X₄is K or R. In any of the aforementioned embodiments, X₅is H or P. In any of the aforementioned embodiments, X₆is L or T. In any of the aforementioned embodiments, X₇is N or A.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 222, wherein X₇is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₂is A or I. In any of the aforementioned embodiments, X₇is A and X₃is I or F. In any of the aforementioned embodiments, X₇is A and X₄is K or R. In any of the aforementioned embodiments, X₇is A and X₅is H or P. In any of the aforementioned embodiments, X₇is A and X₆is L or T.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 222, wherein X₇is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₁is I. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₂is I. In any of the aforementioned embodiments, X₇is A and X₃is F. In any of the aforementioned embodiments, X₇is A and X₄is R. In any of the aforementioned embodiments, X₇is A and X₅is P. In any of the aforementioned embodiments, X₇is A and X₆is T.

In some embodiments, the polypeptide comprises a SIRPα D1 domain that comprises at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to SEQ ID NO: 222, wherein each of X₁, X₂, X₃, X₄, X₅, X₆, and X₇is not a wild-type amino acid.

In some embodiments, the polypeptide of this aspect of the disclosure includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 1. In some embodiments, fragments include polypeptides of less than 10 amino acids in length, about 10 amino acids in length, about 20 amino acids in length, about 30 amino acids in length, about 40 amino acids in length, about 50 amino acids in length, about 60 amino acids in length, about 70 amino acids in length, about 80 amino acids in length, about 90 amino acids in length, about 100 amino acids in length, or more than about 100 amino acids in length. Fragments retain the ability to bind to CD47. Preferably, SIRPα D1 domain variant polypeptides and fragments thereof bind to CD47 with a higher affinity than a SIRPα polypeptide binds to CD47. For example, in some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

In another aspect, the disclosure features a polypeptide including a SIRPα D1 domain variant having a sequence of: EEELQX₁IQPDKSVSVAAGESAILHCTX₂TSLX₃PVGPIQWFRGAGPARELIYNQX₄EGX₅FPRVTTVSEX₆TKRENMDFSISISX₇ITPADAGTYYCVKFRKGSPDTEFKSGAGTELSVRAKPS (SEQ ID NO: 212), wherein X₁is V, L, or I; X₂is V, I, or L; X₃is I, T, S, or F; X₄is K or R; X₅is H, P, or R; X₆is S, T, of G; X₇is N or A; and wherein the variant comprises at least one amino acid substitution relative to a wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 212, wherein X₁is V, L, or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is V, I, or L. In any of the aforementioned embodiments, X₃is I, T, S, or F. In any of the aforementioned embodiments, X₄is K or R. In any of the aforementioned embodiments, X₅is H or P. In any of the aforementioned embodiments, X₆is S, T, or G. In any of the aforementioned embodiments, X₇is N or A.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 212, wherein X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₂is V or I. In any of the aforementioned embodiments, X₃is I or F. In any of the aforementioned embodiments, X₄is K or R. In any of the aforementioned embodiments, X₅is H or P. In any of the aforementioned embodiments, X₆is S or T. In any of the aforementioned embodiments, X₇is N or A.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 212, wherein X₇is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₁is V or I. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₂is V or I. In any of the aforementioned embodiments, X₇is A and X₃is I or F. In any of the aforementioned embodiments, X₇is A and X₄is K or R. In any of the aforementioned embodiments, X₇is A and X₅is H or P. In any of the aforementioned embodiments, X₇is A and X₆is S or T.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 212, wherein X₇is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₁is I. In any of the aforementioned embodiments in this aspect of the disclosure, X₇is A and X₂is I. In any of the aforementioned embodiments, X₇is A and X₃is F. In any of the aforementioned embodiments, X₇is A and X₄is R. In any of the aforementioned embodiments, X₇is A and X₅is P. In any of the aforementioned embodiments, X₇is A and X₆is T.

In some embodiments, the polypeptide comprises a SIRPα D1 domain having at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to SEQ ID NO: 212, wherein each of X₁, X₂, X₃, X₄, X₅, X₆, and X₇is not a wild-type amino acid.

In some embodiments, the polypeptide of this aspect of the disclosure includes no more than ten amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2. In some embodiments, the polypeptide of this aspect of the disclosure includes no more than seven amino acid substitutions relative to the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2.

In some embodiments, the polypeptide binds CD47 with at least 10-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2. In some embodiments, the polypeptide binds CD47 with at least 100-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2. In some embodiments, the polypeptide binds CD47 with at least 1000-fold greater binding affinity than the wild-type SIRPα D1 domain having the sequence of any one of SEQ ID NO: 2. In some embodiments, fragments include polypeptides of less than 10 amino acids in length, about 10 amino acids in length, about 20 amino acids in length, about 30 amino acids in length, about 40 amino acids in length, about 50 amino acids in length, about 60 amino acids in length, about 70 amino acids in length, about 80 amino acids in length, about 90 amino acids in length, about 100 amino acids in length, or more than about 100 amino acids in length. Fragments retain the ability to bind to CD47. Preferably, SIRPα D1 domain variant polypeptides and fragments thereof bind to CD47 with a higher affinity than a SIRPα polypeptide binds to CD47. For example, in some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dless than 1×10⁻⁸M, less than 5×10⁻⁹M, less than 1×10⁻⁹M, less 5×10⁻¹⁰M, less than 1×10⁻¹⁰M or less than 1×10⁻¹¹M In some embodiments, a SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a K_Dbetween about 500 nM and 100 nM, between about 100 nM and 50 nM, between about 50 nM and 10 nM, between about 10 nM and 5 nM, between about 5 nM and 1 nM, between about 1 nM and 500 pM, between about 500 pM and 100 pM, between about 100 pM and 50 pM, or between about 50 pM and 10 pM.

Described herein, in some embodiments, is a polypeptide comprising a SIRPα D1 domain variant having a sequence according to: EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNNMDFSIRIGX₉X₁₀X₁₁X₁₂ADAGTYYCX₁₃KFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 218), wherein X₁is V, L, or I; X₂is A, V, L, or I; X₃is I, S, T, or F; X₄is E, L, or V; X₅is K or R; X₆is E or Q; X₇is H, R, or P; X₈is S, G, L, or T; X₉is any amino acid; X₁₀is any amino acid; X₁₁is any amino acid; X₁₂is any amino acid; and X₁₃is V or I; and wherein the SIRPα D1 domain variant comprises at least two amino acid substitutions relative to a wild-type SIRPα D1 domain having a sequence according to SEQ ID NO: 1.

In some embodiments, the polypeptide comprises the sequence of SEQ ID NO: 212, wherein X₁, wherein X₉is A. In any of the aforementioned embodiments in this aspect of the disclosure, X₉is N. In any of the aforementioned embodiments in this aspect of the disclosure X₁₀is I. In any of the aforementioned embodiments in this aspect of the disclosure X₉is N and X₁₀is P. In any of the aforementioned embodiments in this aspect of the disclosure X₉is N and X₁₁is any amino acid other than S, T, or C. In any of the aforementioned embodiments in this aspect of the disclosure X₁₁is T. In any of the aforementioned embodiments in this aspect of the disclosure X₁₁is an amino acid other than T. In any of the aforementioned embodiments in this aspect of the disclosure X₁₂is P. In any of the aforementioned embodiments in this aspect of the disclosure X₉is N and X₁₂is any amino acid other than P.

Described herein, in some embodiments, is a polypeptide comprising a SIRPα D1 domain variant having a sequence according to: EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRX₄LIYNQX₅X₆GX₇FPRVTTVSDX₈TKRNNMDFSIRIGX₉ITX₁₀ADAGTYYCX₁₁KFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 219), wherein X₁is V, L, or I; X₂is A, V, L, or I; X₃is I, S, T, or F; X₄is E, L, or V; X₅is K or R; X₆is E or Q; X₇is H, R, or P; X₈is S, G, L, or T; X₉is N; X₁₀is any amino acid other than P; and X₁₁is V or I; and wherein the SIRPα D1 domain variant comprises at least two amino acid substitutions relative to a wild-type SIRPα D1 domain having a sequence according to SEQ ID NO: 1.

In another aspect of the disclosure, compositions are disclosed herein which include a SIRPα D1 domain variant polypeptide having the amino acid sequence of SEQ ID NO: 48, or a fragment thereof. In some embodiments, the SIRPα D1 domain variant polypeptide or fragment thereof binds to CD47 with a higher affinity compared to the affinity that a SIRPα polypeptide binds to the CD47. In some embodiments, the SIRPα D1 domain variant polypeptide binds to CD47 with a K_Dless than 1×10⁻⁸M, or less than 1×10⁻⁹M, less than 1×10⁻¹⁰M or less than 1×10⁻¹M. In some embodiments, the above-mentioned SIRPα D1 domain variant polypeptides are attached or fused to a second polypeptide. In some embodiments, the second polypeptide includes, without limitation, an Fc polypeptide, an Fc variant or a fragment of the foregoing.

Without limiting the foregoing, in some embodiments, a SIRPα D1 domain variant polypeptide is selected from any one of SEQ ID NOs: 53-87 and 213 shown in Table 6.

TABLE 6

SIRPα Variant Polypeptides

SEQ ID NO:
Amino Acid Sequence

53
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

54
EEELQVIQPDKSVSVAAGESAILHCTVTSLFPVGPIQWFRGAGPARELIYNQR

QGPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGA

GTELSVRAKPS

55
EEELQVIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

56
EEELQIIQPDKSVSVAAGESAILHCTVTSLFPVGPIQWFRGAGPARVLIYNQRQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

57
EEELQIIQPDKSVSVAAGESAILHCTITSLIPVGPIQWFRGAGPARVLIYNQRQG

PFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAGT

ELSVRAKPS

58
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARELIYNQRQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

59
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQKQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

60
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRE

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

61
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRQ

GHFPRVTTVSETTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

62
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRQ

GPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCIKFRKGSPDTEFKSGAG

TELSVRAKPS

63
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARVLIYNQRQ

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAG

TELSVRAKPS

64
EEELQVIQPDKSVSVAAGESAILHCTVTSLIPVGPIQWFRGAGPARELIYNQRE

GPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAG

TELSVRAKPS

65
EEELQVIQPDKSVSVAAGESAILHCTVTSLFPVGPIQWFRGAGPARELIYNQR

EGPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGA

GTELSVRAKPS

66
EEELQVIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARELIYNQRE

GPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAG

TELSVRAKPS

67
EEELQVIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARELIYNQRE

GPFPRVTTVSETTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAG

TELSVRAKPS

68
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARELIYNQREG

PFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAGT

ELSVRAKPS

69
EEELQVIQPDKSVSVAAGESAILHCTITSLIPVGPIQWFRGAGPARELIYNQRE

GPFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAG

TELSVRAKPS

70
EEELQIIQPDKSVSVAAGESAILHCTITSLFPVGPIQWFRGAGPARELIYNQREG

PFPRVTTVSETTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGAGT

ELSVRAKPS

71
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

72
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

73
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

74
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

75
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

76
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

77
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPS

78
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPS

79
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

80
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPS

81
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

82
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

83
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

84
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

85
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

86
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPS

87
EEELQVIQPDKSVLVAAGETATLRCTATSLIPVGPIQWFRGAGPGRELIYNQK

EGEIFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

195
EEELQIIQPDKSVLVAAGETATLRCTMTSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

196
EEELQIIQPDKSVLVAAGETATLRCTITSLKPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

197
EEELQIIQPDKSVLVAAGETATLRCTITSLRPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

198
EEELQIIQPDKSVLVAAGETATLRCTITSLYPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

199
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

200
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

201
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGMPDDVEFKS

GAGTELSVRAKPS

202
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDVEFKSGA

GTELSVRAKPS

203
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSSEPDVEFKS

GAGTELSVRAKPS

204
EEELQIIQPDKSVLVAAGETATLRCTITSLRPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

205
EEELQIIQPDKSVLVAAGETATLRCTITSLRPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

206
EEELQIIQPDKSVLVAAGETATLRCTITSLRPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

207
EEELQIIQPDKSVLVAAGETATLRCTITSLYPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPS

208
EEELQIIQPDKSVLVAAGETATLRCTITSLYPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

209
EEELQIIQPDKSVLVAAGETATLRCTITSLYPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

210
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPS

213
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGNITVADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPS

In some embodiments, the polypeptide comprises a SIRPα D1 domain variant that has at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to any variant provided in Table 6.

In some embodiments, the polypeptide comprises a SIRPα D1 domain that has at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99 (SEQ ID NO: 223)%, or 100% sequence identity) to SEQ ID NOs: 80, 81, or 85 in Table 6.

Fc Domain Variants and Fusion Polypeptides Comprising Same

Disclosed herein, in some embodiments, are polypeptides comprising a signal-regulatory protein α (SIRP-α) D1 variant comprising a SIRPα D1 domain, or a fragment thereof, having an amino acid mutation at residue 80 relative to a wild-type SIRPα D1 domain; and at least one additional amino acid mutation relative to a wild-type SIRPα D1 domain at a residue selected from the group consisting of: residue 6, residue 27, residue 31, residue 47, residue 53, residue 54, residue 56, residue 66, and residue 92.

Also disclosed herein, in some embodiments, are Fc domain variant dimers, wherein the Fc domain variant dimer comprises two Fc domain variants, wherein each Fc domain variant independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A.

Antibodies that target cell surface antigens can trigger immunostimulatory and effector functions that are associated with Fc receptor (FcR) engagement on immune cells. There are a number of Fc receptors that are specific for particular classes of antibodies, including IgG (gamma receptors), IgE (eta receptors), IgA (alpha receptors) and IgM (mu receptors). Binding of the Fc region to Fc receptors on cell surfaces can trigger a number of biological responses including phagocytosis of antibody-coated particles (antibody-dependent cell-mediated phagocytosis, or ADCP), clearance of immune complexes, lysis of antibody-coated cells by killer cells (antibody-dependent cell-mediated cytotoxicity, or ADCC) and, release of inflammatory mediators, placental transfer, and control of immunoglobulin production. Additionally, binding of the C1 component of complement to antibodies can activate the complement system. Activation of complement can be important for the lysis of cellular pathogens. However, the activation of complement can also stimulate the inflammatory response and can also be involved in autoimmune hypersensitivity or other immunological disorders. Variant Fc regions with reduced or ablated ability to bind certain Fc receptors are useful for developing therapeutic antibodies and Fc-fusion polypeptide constructs which act by targeting, activating, or neutralizing ligand functions while not damaging or destroying local cells or tissues.

In some embodiments, a SIRPα D1 polypeptide construct comprises a non-naturally occurring SIRPα D1 domain variant linked to an Fc domain variant which forms an Fc domain having ablated or reduced effector function.

In some embodiments, a Fc domain variant refers to a polypeptide chain that includes second and third antibody constant domains (e.g., CH2 and CH3). In some embodiments, an Fc domain variant also includes a hinge domain. In some embodiments, the Fc domain variant is of any immunoglobulin antibody isotype, including IgG, IgE, IgM, IgA, and IgD. Additionally, in some embodiments, an Fc domain variant is of any IgG subtype (e.g., IgG1, IgG2, IgG2a, IgG2b, IgG2c, IgG3, and IgG4). In some embodiments, an Fc domain variant comprises as many as ten amino acid modifications (e.g., insertions, deletions and/or substitutions) relative to a wild-type Fc domain monomer sequence (e.g., 1-10, 1-8, 1-6, 1-4 amino acid substitutions, additions or insertions, deletions, or combinations thereof) that alter the interaction between an Fc domain and an Fc receptor.

As used herein, the term “Fc domain dimer” refers to a dimer of two Fc domains. In a wild-type Fc domain dimer, two wild-type Fc domains dimerize by the interaction between the two CH3 antibody constant domains, as well as one or more disulfide bonds that form between the hinge domains of the two dimerized Fc domains.

As used herein, the term “Fc domain dimer variant” comprises at least one Fc domain variant. In some embodiments, an Fc domain dimer variant comprises Fc domain variants that are mutated to lack effector functions, for example a “dead Fc domain dimer variant.” In some embodiments, each of the Fc domains in an Fc domain dimer variant includes amino acid substitutions in the CH2 antibody constant domain to reduce the interaction or binding between the Fc domain dimer variant and an Fc receptor, such as an Fcγ receptor (FcγR), an Fcα receptor (FcαR), or an Fcε (FcεR).

In some embodiments, a SIRPα D1 domain variant (e.g., any of the variants described in Tables 2, 5, and 6) is fused to an Fc domain variant of an immunoglobulin or a fragment of an Fc domain variant. In some embodiments, an Fc domain variant of an immunoglobulin or a fragment of an Fc domain variant is capable of forming an Fc domain dimer with another Fc domain variant. In some embodiments, an Fc domain variant of an immunoglobulin or a fragment of an Fc domain variant is not capable of forming an Fc domain dimer with another Fc domain variant. In some embodiments, an Fc domain variant or a fragment of an Fc domain variant is fused to a polypeptide of the disclosure to increase serum half-life of the polypeptide. In some embodiments, an Fc domain variant or a fragment of an Fc domain variant fused to a polypeptide of the disclosure dimerizes with a second Fc domain variant to form an Fc domain dimer variant which binds an Fc receptor, or alternatively, an Fc domain variant binds to an Fc receptor. In some embodiments, an Fc domain variant or a fragment of the Fc domain variant fused to a polypeptide to increase serum half-life of the polypeptide does not induce any immune system-related response.

In some embodiments, a SIRPα polypeptide or construct provided herein includes a SIRPα D1 domain or variant thereof joined to a first Fc domain variant and an antibody variable domain joined to a second Fc domain variant, in which the first and second Fc domain variants combine to form an Fc domain dimer variant (e.g., a heterodimeric Fc domain dimer variant). An Fc domain dimer is the protein structure that is found at the C-terminus of an immunoglobulin. An Fc domain dimer includes two Fc domains that are dimerized by the interaction between the CH3 antibody constant domains. A wild-type Fc domain dimer forms the minimum structure that binds to an Fc receptor, e.g., FcγRI, FcγRIIa, FcγRIIb, FcγRIIIa, FcγRIIIb, and FcγRIV.

The Fc domain dimer is not involved directly in binding an antibody to its target, but can be involved in various effector functions, such as participation of the antibody in antibody-dependent cellular toxicity. In some embodiments, the Fc domain in a SIRPα polypeptide or construct of the disclosure comprises amino acid substitutions, additions or insertions, deletions, or any combinations thereof that lead to decreased effector function such as decreased antibody-dependent cell-mediated cytotoxicity (ADCC), decreased complement-dependent cytolysis (CDC), decreased antibody-dependent cell-mediated phagocytosis (ADCP), or any combinations thereof. In some embodiments, the SIRPα polypeptides or constructs of the disclosure are characterized by decreased binding (e.g., minimal binding or absence of binding) to a human Fc receptor and decreased binding (e.g., minimal binding or absence of binding) to complement protein C1q. In some embodiments, the SIRPα constructs of the disclosure are characterized by decreased binding (e.g., minimal binding or absence of binding) to human FcγRI, FcγRIIA, FcγRIIB, FcγRIIIB, or any combinations thereof, and C1q. To alter or reduce an antibody-dependent effector function, such as ADCC, CDC, ADCP, or any combinations thereof, in some embodiments, the Fc domains in SIRPα constructs of the disclosure are of the IgG class and comprise one or more amino acid substitutions at E233, L234, L235, G236, G237, D265, D270, N297, E318, K320, K322, A327, A330, P331, or P329 (numbering according to the EU index of Kabat (Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD. (1991))).

In some embodiments, polypeptide constructs comprising a non-native Fc region described herein exhibit reduced or ablated binding to at least one of Fcγ receptors CD16a, CD32a, CD32b, CD32c, and CD64 as compared to a polypeptide construct comprising a native Fc region. In some cases, the polypeptide constructs described herein exhibit reduced or ablated binding to CD16a, CD32a, CD32b, CD32c, and CD64 Fcγ receptors.

CDC refers to a form of cytotoxicity in which the complement cascade is activated by the complement component C1q binding to antibody Fc domains. In some embodiments, polypeptide constructs comprising a non-native Fc region described herein exhibit at least a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or greater reduction in C1q binding compared to a polypeptide construct comprising a wild-type Fc region. In some cases, polypeptide constructs comprising a non-native Fc region as described herein exhibit reduced CDC as compared to a polypeptide construct comprising a wild-type Fc region. In some embodiments, polypeptide constructs comprising a non-native Fc region as described herein exhibit at least a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or greater reduction in CDC compared to a polypeptide construct comprising a wild-type Fc region. In some cases, polypeptide constructs comprising a non-natural Fc domain variants or Fc domain dimer variants as described herein exhibit negligible CDC as compared to a polypeptide construct comprising a wild-type Fc region.

In some embodiments, the Fc domain variants or Fc domain dimer variants described herein are minimally glycosylated or have reduced glycosylation relative to a wild-type sequence. In some embodiments, deglycosylation is accomplished with a mutation of N297A, or by mutating N297 to any amino acid which is not N. In some embodiments, deglycosylation is accomplished by disrupting the motif N-Xaa1-Xaa2-Xaa3, wherein N=asparagine; Xaa1=any amino acid except P (proline); Xaa2=T (threonine), S (serine) or C (cysteine); and Xaa3=any amino acid except P (proline). In one embodiment, the N-Xaa1-Xaa2-Xaa3 motif refers to residues 297-300 as designated according to Kabat et al., 1991. In some embodiments, a mutation to any one or more of N, Xaa1, Xaa2, or Xaa3 results in deglycosylation of the Fc domain variant or Fc domain dimer variant.

In some embodiments, variants of antibody IgG constant regions (e.g., Fc domain variants or Fc domain dimer variants) possess a reduced capacity to specifically bind Fcγ receptors or have a reduced capacity to induce phagocytosis. In some embodiments, variants of antibody IgG constant regions (e.g., Fc domain variants or Fc domain dimer variants) possess a reduced capacity to specifically bind Fcγ receptors and have a reduced capacity to induce phagocytosis. For example, in some embodiments, an Fc domain variant is mutated to lack effector functions, typical of a “dead” Fc domain variant. For example, in some embodiments, an Fc domain variant includes specific amino acid substitutions that are known to minimize the interaction between the Fc domain dimer and an Fcγ receptor. In some embodiments, an Fc domain variant is from an IgG1 antibody and includes one or more of amino acid substitutions L234A, L235A, G237A, and N297A (as designated according to the EU numbering system per Kabat et al., 1991). In some embodiments, one or more additional mutations are included in such IgG1 Fc domain variant. Non-limiting examples of such additional mutations for human IgG1 Fc domain variants include E318A and K322A. In some instances, a human IgG1 Fc domain variant has up to 12, 11, 10, 9, 8, 7, 6, 5 or 4 or fewer mutations in total as compared to wild-type human IgG1 sequence. In some embodiments, one or more additional deletions are included in such IgG1 Fc domain variant. For example, in some embodiments, the C-terminal lysine of the Fc domain IgG1 heavy chain constant region provided in SEQ ID NO: 88 in Table 7 is deleted, for example to increase the homogeneity of the polypeptide when the polypeptide is produced in bacterial or mammalian cells. In some instances, a human IgG1 Fc domain variant has up to 12, 11, 10, 9, 8, 7, 6, 5 or 4 or fewer deletions in total as compared to wild-type human IgG1 sequence (see, e.g., SEQ ID NO: 161 below). In some embodiments, a IgG1 Fc domain variant has a sequence according to any one of SEQ ID NO: 135, SEQ ID NO: 136 or SEQ ID NO: 137.

SEQ ID NO: 161:

DKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHED

PEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYK

CKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVK

GFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQG

NVFSCSVMHEALHNHYTQKSLSLSPG

In some embodiments, an Fc domain variant is from an IgG2 or IgG4 antibody and includes amino acid substitutions A330S, P331S, or both A330S and P331S. The aforementioned amino acid positions are defined according to Kabat, et al. (1991). The Kabat numbering of amino acid residues can be determined for a given antibody by alignment at regions of homology of the sequence of the antibody with a “standard” Kabat numbered sequence. In some embodiments, the Fc domain variant comprises a human IgG2 Fc domain sequence comprising one or more of A330S, P331S and N297A amino acid substitutions (as designated according to the EU numbering system per Kabat, et al. (1991). In some embodiments, one or more additional mutations are included in such IgG2 Fc domain variants. Non-limiting examples of such additional mutations for human IgG2 Fc domain variant include V234A, G237A, P238S, V309 L and H268A (as designated according to the EU numbering system per Kabat et al. (1991)). In some instances, a human IgG2 Fc domain variant has up to 12, 11, 10, 9, 8, 7, 6, 5, 4, 3 or fewer mutations in total as compared to wild-type human IgG2 sequence. In some embodiments, one or more additional deletions are included in such IgG2 Fc domain variant. For example, in some embodiments, the C-terminal lysine of the Fc domain IgG2 heavy chain constant region provided in SEQ ID NO: 89 in Table 7 is deleted, for example to increase the homogeneity of the polypeptide when the polypeptide is produced in bacterial or mammalian cells. In some instances, a human IgG2 Fc domain variant has up to 12, 11, 10, 9, 8, 7, 6, 5 or 4 or fewer deletions in total as compared to wild-type human IgG2 sequence (see, e.g., SEQ ID NO: 162 below).

SEQ ID NO: 162:

ERKCCVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHE

DPEVQFNWYVDGVEVHNAKTKPREEQFNSTFRVVSVLTVVHQDWLNGKEY

KCKVSNKGLPAPIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLV

KGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSMVQQ

GNVFSCSVMHEALHNHYTQKSLSLSPG

When the Fc domain variant is an IgG4 Fc domain variant, in some embodiments, such Fc domain variant comprises a S228P mutation (as designated according to Kabat, et al. (1991)). In some instances, a human IgG4 Fc domain variant has up to 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 mutation(s) in total as compared to wild-type human IgG4 sequence. In some embodiments, the Fc domain variant comprises a human IgG4 Fc sequence comprising one or more of S228P, E233P, F234V, L235A, and delG236 amino acid substitutions (as designated according to the EU numbering system per Kabat, et al. (1991). In some embodiments, the Fc domain variant comprises a human IgG4 Fc sequence comprising one or more of S228P, E233P, F234V, L235A, delG236, and N297A amino acid substitutions (as designated according to the EU numbering system per Kabat, et al. (1991).

In some embodiments, the Fc domain variant includes at least one of the mutations L234A, L235A, G237A or N297A of an IgG1 Fc region or at least one of the mutations A330S, P331S or N297A of an IgG2 Fc region. In some embodiments, the Fc domain variant includes at least two of the mutations L234A, L235A, G237A or N297A of an IgG1 Fc region or at least two of the mutations A330S, P331S or N297A of an IgG2 Fc region. In some embodiments, the Fc domain variant includes at least three of the mutations L234A, L235A, G237A or N297A of an IgG1 Fc region or consists of the mutations A330S, P331S and N297A of an IgG2 Fc region. In some embodiments, the Fc domain variant consists of the mutations L234A, L235A, G237A and N297A.

In some embodiments, the Fc domain variant exhibits reduced binding to an Fc receptor of the subject compared to the wild-type human IgG Fc region. In some embodiments, the Fc domain variant exhibits ablated binding to an Fc receptor of the subject compared to the wild-type human IgG Fc region. In some embodiments, the Fc domain variant exhibits a reduction of phagocytosis compared to the wild-type human IgG Fc region. In some embodiments, the Fc domain variant exhibits ablated phagocytosis compared to the wild-type human IgG Fc region. SEQ ID NO: 88 and SEQ ID NO: 89 provide amino acid sequences of Fc domain IgG1 and IgG2 heavy chain constant regions. In some embodiments, an Fc domain variant is any variant of SEQ ID NOs: 90-95 as shown in Table 7.

TABLE 7

Amino Acid Sequences of Fc Domain Variants

SEQ ID NO:
Amino Acid Sequence

88
EPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSH

EDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGK

EYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLV

KGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQG

NVFSCSVMHEALHNHYTQKSLSLSPGK

89
STKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP

AVLQSSGLYSLSSVVTVPSSSLGTQTYTCNVDEIKPSNTKVDKTVERKCCVE

CPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVQFNWY

VDGVEVHNAKTKPREEQFNSTFRVVSVLTVVHQDWLNGKEYKCKVSNKGL

PAPIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEW

ESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEAL

HNHYTQKSLSLSPGK

90
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPE

VKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKC

KVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFY

PSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFS

CSVMHEALHNHYTQKSLSLSPGK

91
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPE

VKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKC

KVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFY

PSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFS

CSVMHEALHNHYTQKSLSLSPG

92
VECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVQFN

WYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLNGKEYKCKVSN

KGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIA

VEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVM

HEALHNHYTQKSLSLSPGK

93
VECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVQFN

WYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLNGKEYKCKVSN

KGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIA

VEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVM

HEALHNHYTQKSLSLSPG

94
ERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPE

VQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLNGKEYKC

KVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYP

SDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSC

SVMHEALHNHYTQKSLSLSPGK

95
ERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSEIEDPE

VQFNWYVDGVEVEINAKTKPREEQFASTFRVVSVLTVVHQDWLNGKEYKC

KVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYP

SDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQGNVFSC

SVMHEALHNHYTQKSLSLSPG

Antibody-dependent cell-mediated cytotoxicity, which is also referred to herein as ADCC, refers to a form of cytotoxicity in which secreted Ig bound onto Fc receptors (FcRs) present on certain cytotoxic cells (e.g., Natural Killer (NK) cells and neutrophils) enabling these cytotoxic effector cells to bind specifically to an antigen-bearing target cell and subsequently kill the target cell. Antibody-dependent cell-mediated phagocytosis, which is also referred to herein as ADCP, refers to a form of cytotoxicity in which secreted Ig bound onto Fc receptors (FcRs) present on certain phagocytic cells (e.g., macrophages) enabling these phagocytic effector cells to bind specifically to an antigen-bearing target cell and subsequently engulf and digest the target cell. Ligand-specific high-affinity IgG antibodies directed to the surface of target cells can stimulate the cytotoxic or phagocytic cells and can be used for such killing. In some embodiments, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit reduced ADCC or ADCP as compared to a polypeptide construct comprising a wild-type Fc region. In some embodiments, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit at least a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or greater reduction in ADCC or ADCP compared to a polypeptide construct comprising a wild-type Fc region. In some embodiments, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit ablated ADCC or ADCP as compared to a polypeptide construct comprising a wild-type Fc region.

Complement-directed cytotoxicity, which is also referred to herein as CDC, refers to a form of cytotoxicity in which the complement cascade is activated by the complement component C1q binding to antibody Fc domains. In some embodiments, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit at least a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or greater reduction in C1q binding compared to a polypeptide construct comprising a wild-type Fc region. In some cases, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit reduced CDC as compared to a polypeptide construct comprising a wild-type Fc region. In some embodiments, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit at least a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or greater reduction in CDC compared to a polypeptide construct comprising a wild-type Fc region. In some cases, polypeptide constructs comprising an Fc domain variant or Fc domain dimer variant as described herein exhibit negligible CDC as compared to a polypeptide construct comprising a wild-type Fc region.

Fc domain variants or Fc domain dimer variants herein include those that exhibit reduced binding to an Fcγ receptor compared to the wild-type human IgG Fc region. For example, in some embodiments, an Fc domain variant or Fc domain dimer variant exhibits binding to an Fcγ receptor that is less than the binding exhibited by a wild-type human IgG Fc region to an Fcγ receptor, as described in the Examples. In some instances, an Fc domain variant or Fc domain dimer variant has reduced binding to an Fcγ receptor by a factor of 10%, 20% 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99% or 100% (fully ablated effector function). In some embodiments, the reduced binding is for any one or more Fcγ receptor, e.g., CD16a, CD32a, CD32b, CD32c, or CD64.

In some instances, the Fc domain variants or Fc domain dimer variants disclosed herein exhibit a reduction of phagocytosis compared to its wild-type human IgG Fc region. Such Fc domain variants or Fc domain dimer variants exhibit a reduction in phagocytosis compared to its wild-type human IgG Fc region, wherein the reduction of phagocytosis activity is e.g., by a factor of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99% or 100%. In some instances, an Fc domain variant or Fc domain dimer variant exhibits ablated phagocytosis compared to its wild-type human IgG Fc region.

In some embodiments, the Fc domain variants or Fc domain dimer variants disclosed herein are coupled to one or more fusion partners. In some cases the fusion partner is a therapeutic moiety. In some cases, the fusion partner is selected to enable targeting of an expressed protein, purification, screening, display, and the like. In some embodiments, the fusion partner also affects the degree of binding to Fc receptors or the degree of phagocytosis reduction. As described herein, in some embodiments, when an Fc domain variant or Fc domain dimer variant is coupled to a fusion partner, it forms a polypeptide construct as described below.

In some embodiments, fusion partners are linked to the Fc domain variant or Fc domain dimer variant sequence via a linker sequence. In some embodiments, the linker sequence generally comprises a small number of amino acids, such as less than ten amino acids, although longer linkers are also utilized. In some cases, the linker has a length less than 10, 9, 8, 7, 6, or 5 amino acids or shorter. In some cases, the linker has a length of at least 10, 11, 12, 13, 14, 15, 20, 25, 30, or 35 amino acids or longer. Optionally, in some embodiments, a cleavable linker is employed.

In some embodiments, a fusion partner is a targeting or signal sequence that directs an Fc domain variant or Fc domain dimer variant protein and any associated fusion partners to a desired cellular location or to the extracellular media. In some embodiments, certain signaling sequences target a protein to be either secreted into the growth media, or into the periplasmic space, located between the inner and outer membrane of the cell. In some embodiments, a fusion partner is a sequence that encodes a peptide or protein that enables purification or screening. Such fusion partners include, but are not limited to, polyhistidine tags (His-tags) (for example His6 (SEQ ID NO: 223) and His10 (SEQ ID NO: 224)) or other tags for use with Immobilized Metal Affinity Chromatography (IMAC) systems (e.g., Ni+2 affinity columns), GST fusions, MBP fusions, Strep-tag, the BSP biotinylation target sequence of the bacterial enzyme BirA, and epitope tags which are targeted by antibodies (for example c-myc tags, flag-tags, and the like).

In some embodiments, such tags are useful for purification, for screening, or both. For example, in some embodiments, an Fc domain variant or Fc domain dimer variant is purified using a His-tag by immobilizing it to a Ni+2 affinity column, and then after purification the same His-tag is used to immobilize the antibody to a Ni+2 coated plate to perform an ELISA or other binding assay as described elsewhere herein. In some embodiments, a fusion partner enables the use of a selection method to screen Fc domain variants or Fc domain dimer variants as described herein.

Various fusion partners that enable a variety of selection methods are available. For example, by fusing the members of an Fc domain variant or Fc domain dimer variant library to the gene III protein, phage display can be employed. In some embodiments, fusion partners Fc domain variants or Fc domain dimer variants to be labeled. Alternatively, in some embodiments, a fusion partner binds to a specific sequence on the expression vector, enabling the fusion partner and associated Fc domain variant or Fc domain dimer variant to be linked covalently or noncovalently with the nucleic acid that encodes them.

In some embodiments, when a fusion partner is a therapeutic moiety, the therapeutic moiety is, e.g., a peptide, a protein, an antibody, a siRNA, or a small molecule. Non-limiting examples of therapeutic antibodies that are coupled to the Fc domain variants or Fc domain dimer variants of the present disclosure include, but are not limited to antibodies that recognize CD47. Non-limiting examples of therapeutic polypeptides that are coupled to the Fc domain variants or Fc domain dimer variants of the present disclosure include, but are not limited to, CD47 binding polypeptides, including SIRPα polypeptides. In such instances, the CD47 binding polypeptide is attached or fused to an Fc domain variant or Fc domain dimer variant of the disclosure. Examples of CD47 binding polypeptides include, but are not limited to, anti-CD47 antibodies or fragments thereof, and ligands of CD47 such as SIRPα or a fragment thereof. Additional examples of CD47 binding polypeptides include, but are not limited to naturally-occurring forms of SIRP as well as mutants thereof.

In some embodiments, disclosed herein is a polypeptide comprising an Fc domain dimer variant, wherein the Fc domain dimer variant comprises two Fc domain variants, wherein each Fc domain variant independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A. In some embodiments, the Fc domain variants are identical (i.e., homodimer). In some embodiments, the Fc domain variants are different (i.e., heterodimer). In some embodiments, at least one of the Fc domain variant in an Fc domain dimer is a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A. In some embodiments, at least one of the Fc domain variants in an Fc domain dimer is a human IgG2 Fc region consisting of mutations A330S, P331S and N297A. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to an Fcγ receptor compared to the wild-type version of the human IgG Fc region. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to CD16a, CD32a, CD32b, CD32c, and CD64 Fcγ receptors compared to the wild-type version of the human IgG Fc region. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to C1q compared to the wild-type version of the human IgG Fc fusion. In some embodiments, at least one of the Fc domain variants in an Fc domain dimer variant is a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to an Fcγ receptor compared to the wild-type human IgG4 Fc region. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to CD16a and CD32b Fcγ receptors compared to the wild-type version of its human IgG4 Fc region. In some embodiments, the Fc domain dimer variant binds to an Fcγ receptor with a K_Dgreater than about 5×10⁻⁶M.

In some embodiments, the Fc domain dimer variant further comprises a CD47 binding polypeptide. In some embodiments, the Fc domain dimer variant exhibits ablated or reduced binding to an Fcγ receptor compared to a wild-type version of a human IgG Fc region. In some embodiments, the CD47 binding polypeptide does not cause acute anemia in rodents and non-human primates. In some embodiments, the CD47 binding polypeptide does not cause acute anemia in humans.

In some embodiments, the CD47 binding polypeptide is a signal-regulatory protein a (SIRP-α) polypeptide or a fragment thereof. In some embodiments, the SIRPα polypeptide comprises a SIRPα D1 domain variant comprising the amino acid sequence, EEELQX₁IQPDKSVLVAAGETATLRCTX₂TSLX₃PVGPIQWFRGAGPGRX₄LIYNQX₅EGX₆FPR VTTVSDX₇TKRNNMDFSIRIGX₈ITPADAGTYYCX₉KFRKGSPDDVEFKSGAGTELSVRAKPS (SEQ ID NO: 221), wherein X₁is V or I; X₂is A or I; X₃is I or F; X₄is E or V; X₅is K or R; X₆is H or P; X₇is L or T; X₈is any amino acid other than N; and X₉is V or I. In some embodiments, the SIRPα polypeptide comprises a SIRPα D1 domain variant wherein X₁is V or I; X₂is A or I; X₃is I or F; X₄is E; X₅is K or R; X₆is H or P; X₇is L or T; X₈is not N; and X₉is V.

In some embodiments, disclosed herein, is a polypeptide comprising: a SIRPα D1 domain variant, wherein the SIRPα D1 domain variant is a non-naturally occurring high affinity SIRPα D1 domain, wherein the SIRPα D1 domain variant binds to human CD47 with an affinity that is at least 10-fold greater than the affinity of a naturally occurring D1 domain; and an Fc domain variant, wherein the Fc domain variant is linked to a second polypeptide comprising a second Fc domain variant to form an Fc domain dimer variant, wherein the Fc domain dimer variant has ablated or reduced effector function. In some embodiments, the non-naturally occurring high affinity SIRPα D1 domain comprises an amino acid mutation at residue 80.

In some embodiments, disclosed herein, is a SIRPα D1 domain variant, wherein the SIRPα D1 domain variant binds CD47 from a first species with a K_Dless than 250 nM; and wherein the SIRPα D1 domain variant binds CD47 from a second species with a K_Dless than 250 nM; and the K_Dfor CD47 from the first species and the K_Dfor CD47 from the second species are within 100 fold of each other; wherein the first species and the second species are selected from the group consisting of: human, rodent, and non-human primate. In some embodiments, the SIRPα D1 domain variant binds CD47 from at least 3 different species. In some embodiments, the non-human primate is cynomolgus monkey.

In some embodiments, disclosed herein, is a polypeptide comprising (a) a SIRPα D1 domain that binds human CD47 with a K_Dless than 250 nM; and (b) an Fc domain or variant thereof linked to the N-terminus or the C-terminus of the SIRPα D1 domain, wherein the polypeptide does not cause acute anemia in rodents and non-human primates. In some embodiments, the polypeptide is a non-naturally occurring variant of a human SIRP-α. In some embodiments, administration of the polypeptide in vivo results in hemoglobin reduction by less than 50% during the first week after administration. In some embodiments, administration of the polypeptide in humans results in hemoglobin reduction by less than 50% during the first week after administration. In some embodiments, the polypeptide further comprises at least one Fc domain dimer variant, wherein the Fc domain dimer variant comprises an Fc domain variant selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A. In some embodiments, the Fc domain variant is a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A. In some embodiments, the Fc domain variant is a human IgG2 Fc region consisting of mutations A330S, P331S and N297A.

The SIRPα constructs of the disclosure include a SIRPα domain or variant thereof that has its C-terminus joined to the N-terminus of an Fc domain or variant thereof by way of a linker using conventional genetic or chemical means, e.g., chemical conjugation. In some embodiments, a linker (e.g., a spacer) is inserted between the polypeptide and the Fc domain or variant thereof. In some embodiments, a polypeptide of the disclosure including a SIRPα D1 domain variant is fused to an Fc domain variant that is incapable of forming a dimer. In some embodiments, a polypeptide of the disclosure is fused to an Fc domain or variant thereof that is capable of forming a dimer, e.g., a heterodimer, with another Fc domain or variant thereof. In some embodiments, a polypeptide of the invention is fused to an Fc domain or variant thereof and this fusion protein forms a homodimer. In some embodiments, a polypeptide of the disclosure is fused to a first Fc domain or variant thereof and a different protein or peptide (e.g., an antibody variable region) is fused to a second Fc domain or variant thereof. In some embodiments, a SIRPα D1 domain or variant thereof is joined to a first Fc domain or variant thereof and a therapeutic protein (e.g., a cytokine, an interleukin, an antigen, a steroid, an anti-inflammatory agent, or an immunomodulatory agent) is joined to a second Fc domain or variant thereof. In some embodiments, the first and second Fc domains or variants thereof form a heterodimer.

Without the limiting the foregoing, in some embodiments, a SIRPα D1 domain variant polypeptide (e.g., any of the variants described in Tables 2, 5, and 6) is fused to an Fc polypeptide or Fc variant polypeptide, such as an Fc domain or variant thereof. Examples of polypeptides comprising a SIRPα D1 domain variant polypeptide and a fused Fc domain variant polypeptide include, but are not limited to, SEQ ID NOS: 96-137, 214, and 216 shown in Table 8.

TABLE 8

Polypeptides Comprising SIRPα D1 Domain Variants Fused to Fc

Domain Variants

SEQ ID NO:
Amino Acid Sequence

96
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

97
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

98
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

99
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

100
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

101
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

102
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

103
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

104
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

105
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

106
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVV

DVSHEDPEVQFNWYVDGVEVEINAKTKPREEQFASTFRVVSVLTVVHQDWL

NGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTC

LVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQ

QGNVFSCSVMHEALHNHYTQKSLSLSPGK

107
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

108
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVV

DVSHEDPEVQFNWYVDGVEVEINAKTKPREEQFASTFRVVSVLTVVHQDWL

NGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTC

LVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQ

QGNVFSCSVMHEALHNHYTQKSLSLSPGK

109
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVV

DVSHEDPEVQFNWYVDGVEVEINAKTKPREEQFASTFRVVSVLTVVHQDWL

NGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTC

LVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQ

QGNVFSCSVMHEALHNHYTQKSLSLSPGK

110
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

111
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

112
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

113
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTCVVVD

VSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQDWLN

GKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQVSLTCL

VKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKSRWQQ

GNVFSCSVMHEALEINHYTQKSLSLSPGK

114
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

115
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVH

QDWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDK

SRWQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

116
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

117
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

QGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVH

QDWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDK

SRWQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

118
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSEIEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVH

QDWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDK

SRWQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

119
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSEIEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

120
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSEIEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

121
EEELQVIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSEIEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

122
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSEIEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

123
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCV

VVDVSEIEDPEVKFNWYVDGVEVEINAKTKPREEQYNSTYRVVSVLTVLHQD

WLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVS

LTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

124
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

125
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCV

VVDVSHEDPEVKFNWYVDGVEVEINAKTKPREEQYASTYRVVSVLTVLHQD

WLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVS

LTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

126
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKCCVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPAPIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

127
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKCCVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

128
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKCCVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPAPIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

129
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSERKCCVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

130
EEELQVIQPDKSVSVAAGESAILHCTVTSLIPVGPIQWFRGAGPARELIYNQKE

GHFPRVTTVSESTKRENMDFSISISNITPADAGTYYCVKFRKGSPDTEFKSGA

GTELSVRAKPSESKYGPPCPSCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSR

WQEGNVFSCSVMHEALEINHYTQKSLSLSLGK

131
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSESKYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSQEDPEVQFNWYVDGVEVEINAKTKPREEQFNSTYRVVSVLTVLH

QDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKS

RWQEGNVFSCSVMHEALEINHYTQKSLSLSLGK

132
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSESKYGPPCPPCPAPEFEGGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSQEDPEVQFNWYVDGVEVEINAKTKPREEQFNSTYRVVSVLTVLH

QDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKS

RWQEGNVFSCSVMHEALEINHYTQKSLSLSLGK

133
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSESKYGPPCPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSR

WQEGNVFSCSVMHEALEINHYTQKSLSLSLGK

134
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSAAAPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCV

VVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQD

WLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQVS

LTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSR

WQEGNVFSCSVMHEALEINHYTQKSLSLSPGK

135
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKS

RWQQGNVFSCSVMHEALHNHYTQKSLSLSPG

136
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPG

137
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPG

211
EEELQIIQPDKSVLVAAGETATLRCTITSLRPVGPIQWFRGAGPGRELIYNQRD

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGIPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPG

214
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQR

EGPFPRVTTVSDLTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSERKSSVECPPCPAPPVAGPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVQFNWYVDGVEVHNAKTKPREEQFASTFRVVSVLTVVH

QDWLNGKEYKCKVSNKGLPSSIEKTISKTKGQPREPQVYTLPPSREEMTKNQ

VSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPMLDSDGSFFLYSKLTVDK

SRWQQGNVFSCSVMHEALEINHYTQKSLSLSPG

216
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQRQ

GPFPRVTTVSDTTKRNNMDFSIRIGNITPADAGTYYCIKFRKGSPDDVEFKSG

AGTELSVRAKPSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCV

VVDVSHEDPEVKFNWYVDGVEVEINAKTKPREEQYNSTYRVVSVLTVLHQD

WLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVS

LTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALEINHYTQKSLSLSPGK

217
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKSG

AGTELSVRAKPSEKTHTCPECPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTC

VVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQ

DWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQV

SLTCEVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR

WQQGNVFSCSVMHEALIINHYTQKSLSLSPGK

In some embodiments, the polypeptide comprises a SIRPα D1 variant domain that has at least 85% sequence identity (e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity) to any variant provided in Table 8.

In some embodiments, the polypeptide comprises (a) a signal-regulatory protein α (SIRP-α) D1 variant, wherein the SIRPα D1 domain variant comprises the amino acid sequence, EEX₁X₂QX₃IQPDKX₄VX₅VAAGEX₆X₇XSLX₉CTX₁₀TSLX₁₁PVGPIQWFRGAGPX₁₂RX₁₃LIYNQ X₁₄X₁₅GX₁₆FPRVTTVSX₁₇X₁₈TX₁₉RX₂₀DNMDFX₂₁X₂₂IX₂₃X₂₄ITX₂₅ADAGTYYCX₂₆KX₂₇RKGSPDX₂₈X₂₉EX₃₀KSGAGTELSVRX₃₁KPS (SEQ ID NO: 47), wherein X₁is E, or G; X₂is L, I, or V; X₃is V, L, or I; X₄is S, or F; X₅is L, or S; X₆is S, or T; X₇is A, or V; X₈is I, or T; X₉is H, R, or L; X₁₀is A, V, I, or L; X₁₁is I, T, S, or F; X₁₂is A, or G; X₁₃is E, V, or L; X₁₄is K, or R; X₁₅is E, or Q; X₁₆is H, P, or R; X₁₇is D, or E; X₁₈is S, L, T, or G; X₁₉is K, or R; X₂₀is E, or N; X₂₁is S, or P; X₂₂is S, or R; X₂₃is S, or G; X₂₄is any amino acid; X₂₅is any amino acid; X₂₆is V, or I; X₂₇is F, L, or V; X₂n is D or absent; X₂₉is T, or V; X₃₀is F, or V; and X₃₁is A, or G; and wherein the SIRPα D1 domain variant comprises at least two amino acid substitutions relative to a wild-type SIRPα D1 domain having a sequence according to any one of SEQ ID NOs: 1 to 10; and (b) an Fc domain dimer variant having two Fc domain variants, wherein each Fc domain variant independently is (i) a human IgG1 Fc region comprising a N297A mutation; (ii) a human IgG1 Fc region comprising L234A, L235A, and G237A mutations; (iii) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations; (iv) a human IgG2 Fc region comprising a N297A mutation; (v) a human IgG2 Fc region comprising A330S and P331S mutations; (vi) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations; (vii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations; or (viii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations.

In some embodiments, the polypeptide comprises a SIRPα D1 domain variant wherein the SIRPα D1 domain variant comprises an amino acid sequence according to SEQ ID NO: 47; an Fc domain dimer having two Fc domains, wherein one of the Fc domains is an Fc domain variant comprising a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations.

Dimerization of Fc Domains

In some embodiments, a SIRPα D1 domain variant polypeptide (e.g., any of the variants described in Tables 2, 5, and 6) is fused to a first Fc domain (e.g., an Fc domain variant) either at the N-terminus or at the C-terminus. In some embodiments, the first Fc domain is a variant that is incapable of forming an dimer. In some embodiments, the first Fc domain forms a dimer with a second Fc domain. In some embodiments, the first and second Fc domains comprise amino acid substitutions that promote heterodimerization between the first and second domain Fc domains.

In some embodiments, each of the two Fc domains in an Fc domain dimer includes amino acid substitutions that promote the heterodimerization of the two monomers. In some embodiments, a SIRPα construct is formed, for example, from a first subunit including a SIRPα D1 domain variant polypeptide fused to a first Fc domain and a second subunit including a second Fc domain (e.g., without a SIRPα D1 domain variant polypeptide or any other polypeptide). In some embodiments, a construct has a single SIRPα D1 domain variant polypeptide linked to an Fc domain dimer (e.g., single arm). In some embodiments, a construct has two SIRPα D1 domain variant polypeptides linked to an Fc domain dimer (e.g., double arm). In some embodiments, a SIRPα D1 domain variant having a K_Dof about 500 nM is particularly useful in a double arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 50 nM is particularly useful in a double arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 5 nM is useful in a double arm construct and a single arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 500 pM is useful in a double arm construct and a single arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 100 pM is useful in a double arm construct and a single arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 50 pM is useful in a double arm construct and a single arm construct. In some embodiments, a SIRPα D1 domain variant having a K_Dof about 10 pM is useful in a double arm construct and a single arm construct.

In some embodiments, heterodimerization of Fc domains is promoted by introducing different, but compatible, substitutions in the two Fc domains, such as “knob-into-hole” residue pairs and charge residue pairs. The knob and hole interaction favors heterodimer formation, whereas the knob-knob and the hole-hole interaction hinder homodimer formation due to steric clash and deletion of favorable interactions. A hole refers to a void that is created when an original amino acid in a protein is replaced with a different amino acid having a smaller side-chain volume. A knob refers to a bump that is created when an original amino acid in a protein is replaced with a different amino acid having a larger side-chain volume. For example, in some embodiments, an amino acid being replaced is in the CH3 antibody constant domain of an Fc domain and involved in the dimerization of two Fc domains. In some embodiments, a hole in one CH3 antibody constant domain is created to accommodate a knob in another CH3 antibody constant domain, such that the knob and hole amino acids act to promote or favor the heterodimerization of the two Fc domains. In some embodiments, a hole in one CH3 antibody constant domain is created to better accommodate an original amino acid in another CH3 antibody constant domain. In some embodiments, a knob in one CH3 antibody constant domain is created to form additional interactions with original amino acids in another CH3 antibody constant domain.

In some embodiments, a hole is constructed by replacing amino acids having larger side chains such as tyrosine or tryptophan with amino acids having smaller side chains such as alanine, valine, or threonine, for example a Y407V mutation in the CH3 antibody constant domain. Similarly, in some embodiments, a knob is constructed by replacing amino acids having smaller side chains with amino acids having larger side chains, for example a T366W mutation in the CH3 antibody constant domain. In some embodiments, one Fc domain includes the knob mutation T366W and the other Fc domain includes hole mutations T366S, L358A, and Y407V. In some embodiments, a polypeptide of the disclosure including a SIRPα D1 domain variant is fused to an Fc domain including the knob mutation T366W to limit unwanted knob-knob homodimer formation. Examples of knob-into-hole amino acid pairs are included, without limitation, in Table 9 and examples of knob-into-hole Fc domain variants and SIRPα-Fc fusions are provided in Table 10.

TABLE 9

Knob-into-Hole Amino Acid Pairs

First Fc
Y407T
Y407A
F405A
T394S
T366S
T394W
T394S
T366W

Domain

L358A
Y407T
Y407A
T394S

Y407V

Second Fc
T366Y
T366W
T394W
F405W
T366W
T366Y
T366W
F405W

Domain

F405A
F405W
Y407A

TABLE 10

Exemplary Fc Domain Variants and SIRPα D1 Domain Variant-Fc Domain

Variant Fusion Polypeptides

SEQ ID NO:
Amino Acid Sequence

138
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQR

QGPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKN

QVSLWCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTV

DKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

139
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEV

KFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCK

VSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLSCAVKGFYPS

DIAVEWESNGQPENNYKTTPPVLDSDGSFFLVSKLTVDKSRWQQGNVFSCS

VMHEALHNHYTQKSLSLSPGK

140
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRVLIYNQR

QGPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCIKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKN

QVSLSCAVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLVSKLTVD

KSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

141
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEV

KFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCK

VSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLWCLVKGFYP

SDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSC

SVMHEALHNHYTQKSLSLSPGK

142
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKN

QVSLWCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTV

DKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

143
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKN

QVSLSCAVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLVSKLTVD

KSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

144
QVQLKQSGPGLVQPSQSLSITCTVSGFSLTNYGVHWVRQSPGKGLEWLGVI

WSGGNTDYNTPFTSRLSINKDNSKSQVFFKMNSLQSNDTAIYYCARALTYY

DYEFAYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPE

PVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNH

KPSNTKVDKKVEPKSCRKTHTCPRCPAPELLGGPSVFLFPPKPKDTLMISRTP

EVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLT

VLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEM

TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRL

TVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

145
EEELQIIQPDKSVLVAAGETATLRCTITSLFPVGPIQWFRGAGPGRELIYNQRE

GPFPRVTTVSDTTKRNNMDFSIRIGAITPADAGTYYCVKFRKGSPDDVEFKS

GAGTELSVRAKPSEKTHTCPECPAPEAAGAPSVFLFPPKPKDTLMISRTPEVT

CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLH

QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKN

QVSLTCEVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVD

KSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

146
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQ

RQGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEF

KSGAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPE

VTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV

LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMT

KNQVSLWCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKL

TVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

147
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEV

KFNWYVDGVEVEINAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCK

VSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLSCAVKGFYPS

DIAVEWESNGQPENNYKTTPPVLDSDGSFFLVSKLTVDKSRWQQGNVFSCS

VMHEALHNHYTQKSLSLSPGK

148
EEELQVIQPDKSVLVAAGETATLRCTATSLFPVGPIQWFRGAGPGRELIYNQ

RQGPFPRVTTVSDLTKRNNMDFSIRIGNITPADAGTYYCVKFRKGSPDDVEF

KSGAGTELSVRAKPSDKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPE

VTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV

LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMT

KNQVSLSCAVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLVSKLT

VDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

149
DKTHTCPPCPAPEAAGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEV

KFNWYVDGVEVEINAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCK

VSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLWCLVKGFYP

SDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSC

SVMHEALHNHYTQKSLSLSPGK

In addition to the knob-into-hole strategy, in some embodiments, electrostatic steering is also used to control the dimerization of Fc domains. Electrostatic steering refers to the utilization of favorable electrostatic interactions between oppositely charged amino acids in peptides, protein domains, and proteins to control the formation of higher ordered protein molecules. In particular, to control the dimerization of Fc domains using electrostatic steering, one or more amino acid residues that make up the CH3-CH3 interface are replaced with positively- or negatively-charged amino acid residues such that the interaction becomes electrostatically favorable or unfavorable depending on the specific charged amino acids introduced. In some embodiments, a positively-charged amino acid in the interface, such as lysine, arginine, or histidine, is replaced with a negatively-charged amino acid such as aspartic acid or glutamic acid. In some embodiments, a negatively-charged amino acid in the interface is replaced with a positively-charged amino acid. In some embodiments, the charged amino acids are introduced to one of the interacting CH3 antibody constant domains, or both. In some embodiments, introducing charged amino acids to the interacting CH3 antibody constant domains of the two Fc domains promotes the selective formation of heterodimers of Fc domains as controlled by the electrostatic steering effects resulting from the interaction between charged amino acids. Examples of electrostatic steering amino acid pairs are included, without limitation, in Table 11.

TABLE 11

Electrostatic Steering Amino Acid Pairs

Fc domain
K409D
K409D
K409E
K409E
K392D
K392D
K392E
K392E
K409D
K370E

monomer 1

K392D
K409D

K439E

Fc domain
D399K
D399R
D399K
D399R
D399K
D399R
D399K
D399R
D399K
D356K

monomer 2

D356K
E357K

D399K

Other methods used to control the heterodimerization of Fc domains, especially in the context of constructing a bispecific antibody, are available.

In some embodiments, a first Fc domain and a second Fc domain each includes one or more of the following amino acid substitutions: T366W, T366S, L368A, Y407V, T366Y, T394W, F405W, Y349T, Y349E, Y349V, L351T, L351H, L351N, L351K, P353S, S354D, D356K, D356R, D356S, E357K, E357R, E357Q, S364A, T366E, L368T, L368Y, L368E, K370E, K370D, K370Q, K392E, K392D, T394N, P395N, P396T, V397T, V397Q, L398T, D399K, D399R, D399N, F405T, F405H, F405R, Y407T, Y407H, Y407I, K409E, K409D, K409T, and K409I, relative to the sequence of human IgG1.

In some embodiments an Fc domain comprises: (a) one of the following amino acid substitutions relative to wild type human IgG1: T366W, T366S, L368A, Y407V, T366Y, T394W, F405W, Y349T, Y349E, Y349V, L351T, L351H, L351N, L351K, P353S, S354D, D356K, D356R, D356S, E357K, E357R, E357Q, S364A, T366E, L368T, L368Y, L368E, K370E, K370D, K370Q, K392E, K392D, T394N, P395N, P396T, V397T, V397Q, L398T, D399K, D399R, D399N, F405T, F405H, F405R, Y407T, Y407H, Y407I, K409E, K409D, K409T, or K409I; or (b) (i) a N297A mutation relative to a human IgG1 Fc region; (ii) a L234A, L235A, and G237A mutation relative to a human IgG1 Fc region; (iii) a L234A, L235A, G237A, and N297A mutation relative to a human IgG1 Fc region; (iv) a N297A mutation relative to a human IgG2 Fc region; (v) a A330S and P331S mutation relative to a human IgG2 Fc region; (vi) a A330S, P33 IS, and N297A mutation relative to a human IgG2 Fc region; (vii) a S228P, E233P, F234V, L235A, and delG236 mutation relative to a human IgG4 Fc region; or (viii) a S228P, E233P, F234V, L235A, delG236, and N297A mutation relative to a human IgG4 Fc region. In some embodiments an Fc domain variant comprises: (a) one of the following amino acid substitutions relative to wild type human IgG1: T366W, T366S, L368A, Y407V, T366Y, T394W, F405W, Y349T, Y349E, Y349V, L351T, L351H, L351N, L351K, P353S, S354D, D356K, D356R, D356S, E357K, E357R, E357Q, S364A, T366E, L368T, L368Y, L368E, K370E, K370D, K370Q, K392E, K392D, T394N, P395N, P396T, V397T, V397Q, L398T, D399K, D399R, D399N, F405T, F405H, F405R, Y407T, Y407H, Y407I, K409E, K409D, K409T, or K409I; and (b) further comprises (i) a N297A mutation relative to a human IgG1 Fc region; (ii) a L234A, L235A, and G237A mutation relative to a human IgG1 Fc region; (iii) a L234A, L235A, G237A, and N297A mutation relative to a human IgG1 Fc region; (iv) a N297A mutation relative to a human IgG2 Fc region; (v) a A330S and P331S mutation relative to a human IgG2 Fc region; (vi) a A330S, P331S, and N297A mutation relative to a human IgG2 Fc region; (vii) a S228P, E233P, F234V, L235A, and delG236 mutation relative to a human IgG4 Fc region; or (viii) a S228P, E233P, F234V, L235A, delG236, and N297A mutation relative to a human IgG4 Fc region.

In some embodiments, the first and second Fc domains include different amino acid substitutions. In some embodiments, the first Fc domain includes T366W. In some embodiments, the second Fc domain includes T366S, L368A, and Y407V. In some embodiments, the first Fc domain includes D399K. In some embodiments, the second Fc domain includes K409D.

Linkers

Also disclosed herein, in some embodiments, are polypeptides comprising an Fc variant, wherein the Fc variant comprises an Fc domain dimer comprising two Fc domain variants, wherein each Fc domain variant independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A.

In the present disclosure, a linker is used to describe a linkage or connection between polypeptides or protein domains or associated non-protein moieties. In some embodiments, a linker is a linkage or connection between an Fc domain (or variant thereof) and a SIRPα D1 domain variant. In some embodiments, the linker connects the C-terminus of the SIRPα D1 domain variant and the N-terminus of the Fc domain variant, such that the two polypeptides are joined to each other in tandem series.

In some embodiments, a linker is a simple covalent bond, e.g., a peptide bond, a synthetic polymer, or any kind of bond created from a chemical reaction, e.g. chemical conjugation. When a linker is a peptide bond, in some embodiments, the carboxylic acid group at the C-terminus of one protein domain reacts with the amino group at the N-terminus of another protein domain in a condensation reaction to form a peptide bond. In some embodiments, the peptide bond is formed from synthetic means through a conventional organic chemistry reaction, or by natural production from a host cell, wherein a nucleic acid molecule encoding the DNA sequences of both proteins (e.g., an Fc domain variant and a SIRPα D1 domain variant) in tandem series can be directly transcribed and translated into a contiguous polypeptide encoding both proteins by the necessary molecular machineries (e.g., DNA polymerase and ribosome) in the host cell.

When a linker is a synthetic polymer, in some embodiments, the polymer is functionalized with reactive chemical functional groups at each end to react with the terminal amino acids at the connecting ends of two proteins.

When a linker (except peptide bond mentioned above) is made from a chemical reaction, in some embodiments, chemical functional groups (e.g., amine, carboxylic acid, ester, azide, or other functional groups), are attached synthetically to the C-terminus of one protein and the N-terminus of another protein, respectively. In some embodiments, the two functional groups then react through synthetic chemistry means to form a chemical bond, thus connecting the two proteins together.

Spacers

In the present disclosure, in some embodiments, a linker between an Fc domain monomer and a SIRPα D1 variant polypeptide of the disclosure, is an amino acid spacer including about 1-200 amino acids. Suitable peptide spacers include peptide linkers containing flexible amino acid residues such as glycine and serine. Examples of linker sequences are provided in Table 12. In some embodiments, a spacer contains motifs, e.g., multiple or repeating motifs, of GS, GG, GGS, GGG, GGGGS (SEQ ID NO: 163), GGSG (SEQ ID NO: 164), or SGGG (SEQ ID NO: 165). In some embodiments, a spacer contains 2 to 12 amino acids including motifs of GS, e.g., GS, GSGS (SEQ ID NO: 166), GSGSGS (SEQ ID NO: 167), GSGSGSGS (SEQ ID NO: 168), GSGSGSGSGS (SEQ ID NO: 169), or GSGSGSGSGSGS (SEQ ID NO: 170). In some embodiments, a spacer contains 3 to 12 amino acids including motifs of GGS, e.g., GGS, GGSGGS (SEQ ID NO: 171), GGSGGSGGS (SEQ ID NO: 172), and GGSGGSGGSGGS (SEQ ID NO: 173). In some embodiments, a spacer contains 4 to 12 amino acids including motifs of GGSG (SEQ ID NO: 164), e.g., GGSG (SEQ ID NO: 164), GGSGGGSG (SEQ ID NO: 174), or GGSGGGSGGGSG (SEQ ID NO: 175). In some embodiments, a spacer contains motifs of GGGGS (SEQ ID NO: 163), e.g., GGGGSGGGGSGGGGS (SEQ ID NO: 176). In some embodiments, a spacer contains amino acids other than glycine and serine, e.g., AAS, AAAL (SEQ ID NO: 178), AAAK (SEQ ID NO: 179), AAAR (SEQ ID NO: 180), EGKSSGSGSESKST (SEQ ID NO: 181), GSAGSAAGSGEF (SEQ ID NO: 182), AEAAAKEAAAKA (SEQ ID NO: 183), KESGSVSSEQLAQFRSLD (SEQ ID NO: 184), GGGGAGGGG (SEQ ID NO: 185), GENLYFQSGG (SEQ ID NO: 186), SACYCELS (SEQ ID NO: 187), RSIAT (SEQ ID NO: 188), RPACKIPNDLKQKVMNH (SEQ ID NO: 189), GGSAGGSGSGSSGGSSGASGTGTAGGTGSGSGTGSG (SEQ ID NO: 190), AAANSSIDLISVPVDSR (SEQ ID NO: 191), or GGSGGGSEGGGSEGGGSEGGGSEGGGSEGGGSGGGS (SEQ ID NO: 192).

In some embodiments, a spacer contains motifs, e.g., multiple or repeating motifs, of EAAAK (SEQ ID NO: 193). In some embodiments, a spacer contains motifs, e.g., multiple or repeating motifs, of proline-rich sequences such as (XP)n, in which X is any amino acid (e.g., A, K, or E) and n is from 1-5, and PAPAP (SEQ ID NO: 194).

TABLE 12

Linker Sequences

SEQ ID NO:
AminoAcidSequence

163
GGGGS

164
GGSG

165
SGGG

166
GSGS

167
GSGSGS

168
GSGSGSGS

169
GSGSGSGSGS

170
GSGSGSGSGSGS

171
GGSGGS

172
GGSGGSGGS

173
GGSGGSGGSGGS

174
GGSGGGSG

175
GGSGGGSGGGSG

176
GGGGSGGGGSGGGGS

177
AAS

178
AAAL

179
AAAK

180
AAAR

181
EGKSSGSGSESKST

182
GSAGSAAGSGEF

183
AEAAAKEAAAKA

184
KESGSVSSEQLAQFRSLD

185
GGGGAGGGG

186
GENLYFQSGG

187
SACYCELS

188
RSIAT

189
RPACKIPNDLKQKVMNH

190
GGSAGGSGSGSSGGSSGASGTGTAGGTGSGSGTGSG

191
AAANSSIDLISVPVDSR

192
GGSGGGSEGGGSEGGGSEGGGSEGGGSEGGGSGGGS

193
EAAAK

194
PAPAP

In some embodiments, the length of the peptide spacer and the amino acids used is adjusted depending on the two proteins involved and the degree of flexibility desired in the final protein fusion polypeptide. In some embodiments, the length of the spacer is adjusted to ensure proper protein folding and avoid aggregate formation. In some embodiments, a spacer is A or AAAL (SEQ ID NO: 178).

Vectors, Host Cells, and Protein Production

Disclosed herein, in some embodiments, are polypeptides comprising a signal-regulatory protein α (SIRP-(α) D1 variant comprising a SIRPα D1 domain, or a fragment thereof, having an amino acid mutation at residue 80 relative to a wild-type SIRPα D1 domain; and at least one additional amino acid mutation relative to a wild-type SIRPα D1 domain at a residue selected from the group consisting of: residue 6, residue 27, residue 31, residue 47, residue 53, residue 54, residue 56, residue 66, and residue 92.

Also disclosed herein, in some embodiments, are polypeptides comprising an Fc variant, wherein the Fc variant comprises an Fc domain dimer having two Fc domain monomers, wherein each Fc domain monomer independently is selected from (i) a human IgG1 Fc region consisting of mutations L234A, L235A, G237A, and N297A; (ii) a human IgG2 Fc region consisting of mutations A330S, P331S and N297A; or (iii) a human IgG4 Fc region comprising mutations S228P, E233P, F234V, L235A, delG236, and N297A.

In some embodiments, the polypeptides of the disclosure are produced from a host cell. A host cell refers to a vehicle that includes the necessary cellular components, e.g., organelles, needed to express the polypeptides and fusion polypeptides described herein from their corresponding nucleic acids. In some embodiments, the nucleic acids are included in nucleic acid vectors introduced into the host cell by transformation, transfection, electroporation, calcium phosphate precipitation, direct microinjection, infection, etc. In some embodiments, the choice of nucleic acid vector depends on the host cell to be used. In some embodiments, host cells are of either prokaryotic (e.g., bacterial) or eukaryotic (e.g., mammalian) origin.

In some embodiments, a polypeptide, for example a polypeptide construct comprising a SIRPα D1 domain variant (e.g., any variant provided in Tables 2, 5, and 6) and a fusion partner such as an Fc variant are produced by culturing a host cell transformed with a nucleic acid, preferably an expression vector, containing a nucleic acid encoding the polypeptide construct (e.g., Fc variant, linker, and fusion partner) under the appropriate conditions to induce or cause expression of the polypeptide construct. In some embodiments, the conditions appropriate for expression varies with the expression vector and the host cell chosen. In some embodiments, a wide variety of appropriate host cells are used, including, but not limited to, mammalian cells, bacteria, insect cells, and yeast. For example, a variety of cell lines that find use in the present disclosure are described in the ATCC® cell line catalog, available from the American Type Culture Collection. In some embodiments, Fc domain variants of this disclosure are expressed in a cell that is optimized not to glycosylate proteins that are expressed by such cell, either by genetic engineering of the cell line or modifications of cell culture conditions such as addition of kifunensine or by using a naturally non-glycosylating host such as a prokaryote (E. coli, etc.), and in some cases, modification of the glycosylation sequence in the Fc is not be needed.

Nucleic Acid Vector Construction and Host Cells

A nucleic acid sequence encoding the amino acid sequence of a polypeptide of the disclosure can be prepared by a variety of methods. These methods include, but are not limited to, oligonucleotide-mediated (or site-directed) mutagenesis and PCR mutagenesis. In some embodiments, a nucleic acid molecule encoding a polypeptide of the disclosure is obtained using standard techniques, e.g., gene synthesis. Alternatively, a nucleic acid molecule encoding a wild-type SIRPα D1 domain is mutated to include specific amino acid substitutions using standard techniques, e.g., QuikChange™ mutagenesis. In some cases, nucleic acid molecules are synthesized using a nucleotide synthesizer or PCR techniques.

In some embodiments, the nucleic acids that encode a polypeptide construct, for example a polypeptide construct comprising a SIRPα D1 domain variant (e.g., any variant provided in Tables 2, 5, and 6) and a fusion partner such as an Fc variant are incorporated into an expression vector in order to express the protein. A variety of expression vectors can be utilized for protein expression. Expression vectors can comprise self-replicating, extra-chromosomal vectors or vectors which integrate into a host genome. A vector can also include various components or elements. For example, in some embodiments, the vector components include, but are not limited to, transcriptional and translational regulatory sequences such as a promoter sequence, a ribosomal binding site, a signal sequence, transcriptional start and stop sequences, translational start and stop sequences, 3′ and 5′ untranslated regions (UTRs), and enhancer or activator sequences; an origin of replication; a selection marker gene; and the nucleic acid sequence encoding the polypeptide of interest, and a transcription termination sequence. In some embodiments, expression vectors comprise a protein operably linked with control or regulatory sequences, selectable markers, any fusion partners, additional elements, or any combinations thereof. The term “operably linked” means that the nucleic acid is placed into a functional relationship with another nucleic acid sequence. Generally, these expression vectors include transcriptional and translational regulatory nucleic acid operably linked to the nucleic acid encoding the Fc variant, and are typically appropriate to the host cell used to express the protein. A selection gene or marker, such as, but not limited to, an antibiotic resistance gene or fluorescent protein gene, can be used to select for host cells containing the expression vector, for example by antibiotic or fluorescence expression. Various selection genes are available.

In some embodiments, the components or elements of a vector are optimized such that expression vectors are compatible with the host cell type. Expression vectors which find use in the present disclosure include, but are not limited to, those which enable protein expression in mammalian cells, bacteria, insect cells, yeast, and in in vitro systems.

In some embodiments, mammalian cells are used as host cells to produce polypeptides of the disclosure. Examples of mammalian cell types include, but are not limited to, human embryonic kidney (HEK) (e.g., HEK293, HEK 293F), Chinese hamster ovary (CHO), HeLa, COS, PC3, Vero, MC3T3, NS0, Sp2/0, VERY, BHK, MDCK, W138, BT483, Hs578T, HTB2, BT20, T47D, NS0 (a murine myeloma cell line that does not endogenously produce any immunoglobulin chains), CRL7030, and HsS78Bst cells. In some embodiments, E. coli cells are used as host cells to produce polypeptides of the disclosure. Examples of E. coli strains include, but are not limited to, E. coli 294 (ATCC® 31,446), E. coli λ 1776 (ATCC® 31,537, E. coli BL21 (DE3) (ATCC® BAA-1025), and E. coli RV308 (ATCC® 31,608).

Different host cells have characteristic and specific mechanisms for the posttranslational processing and modification of protein products (e.g., glycosylation). In some embodiments, appropriate cell lines or host systems are chosen to ensure the correct modification and processing of the polypeptide expressed. Once the vectors are introduced into host cells for protein production, host cells are cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences.

In some embodiments, a polypeptide construct, for example a polypeptide construct comprising a SIRPα D1 domain variant (e.g., any variant provided in Tables 2, 5, and 6) and a fusion partner such as an Fc variant are expressed in mammalian expression systems, including systems in which the expression constructs are introduced into the mammalian cells using virus such as retrovirus or adenovirus. In some embodiments, human, mouse, rat, hamster, or primate cells are utilized. Suitable cells also include known research cells, including but not limited to Jurkat T cells, NIH3T3, CHO, COS, and 293 cells. Alternately, in some embodiments, proteins are expressed in bacterial cells. Bacterial expression systems are well known in the art, and include Escherichia coli (E. coli), Bacillus subtilis, Streptococcus cremoris, and Streptococcus lividans. In some cases, polypeptide constructs comprising Fc domain variants are produced in insect cells such as but not limited to Sf9 and Sf21 cells or yeast cells such as but not limited to organisms from the genera Saccharomyces, Pichia, Kluyveromyces, Hansenula and Yarrowia. In some cases, polypeptide constructs comprising Fc domain variants are expressed in vitro using cell free translation systems. In vitro translation systems derived from both prokaryotic (e.g., E. coli) and eukaryotic (e.g., wheat germ, rabbit reticulocytes) cells are available and, in some embodiments, chosen based on the expression levels and functional properties of the protein of interest. For example, as appreciated by those skilled in the art, in vitro translation is required for some display technologies, for example ribosome display. In addition, in some embodiments, the Fc domain variants are produced by chemical synthesis methods such as, but not limited to, liquid-phase peptide synthesis and solid-phase peptide synthesis. In the case of in vitro transcription using a non-glycosylating system such as bacterial extracts, the Fc will not be glycosylated even in presence of the natural glycosylation site and therefore inactivation of the Fc will be equivalently obtained.

In some embodiments, a polypeptide construct includes non-natural amino acids, amino acid analogues, amino acid mimetics, or any combinations thereof that function in a manner similar to the naturally occurring amino acids. Naturally encoded amino acids generally refer to the 20 common amino acids (alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine) and pyrrolysine and selenocysteine. Amino acid analogs refers to compounds that have the same basic chemical structure as a naturally occurring amino acid, e.g., a carbon that is bound to a hydrogen, a carboxyl group, an amino group, and an R group, such as, homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. In some embodiments, such analogs have modified R groups (such as, norleucine) or modified peptide backbones, but generally retain the same basic chemical structure as a naturally occurring amino acid.

Protein Production, Recovery, and Purification

In some embodiments, host cells used to produce polypeptides of the disclosure are grown in media suitable for culturing of the selected host cells. Examples of suitable media for mammalian host cells include Minimal Essential Medium (MEM), Dulbecco's Modified Eagle's Medium (DMEM), Expi293™ Expression Medium, DMEM with supplemented fetal bovine serum (FBS), and RPMI-1640. Examples of suitable media for bacterial host cells include Luria broth (LB) plus necessary supplements, such as a selection agent, e.g., ampicillin. In some embodiments, host cells are cultured at suitable temperatures, such as from about 20° C. to about 39° C., e.g., from about 25° C. to about 37° C., preferably 37° C., and CO2 levels, such as about 5% to 10%. In some embodiments, the pH of the medium is from about pH 6.8 to pH 7.4, e.g., pH 7.0, depending mainly on the host organism. If an inducible promoter is used in the expression vector, protein expression can be induced under conditions suitable for the activation of the promoter.

In some embodiments, protein recovery involves disrupting the host cell, for example by osmotic shock, sonication, or lysis. Once the cells are disrupted, cell debris is removed by centrifugation or filtration. The proteins can then be further purified. In some embodiments, a polypeptide of the disclosure is purified by various methods of protein purification, for example, by chromatography (e.g., ion exchange chromatography, affinity chromatography, and size-exclusion column chromatography), centrifugation, differential solubility, or by any other standard technique for the purification of proteins. For example, in some embodiments, the protein is isolated and purified by appropriately selecting and combining affinity columns such as Protein A column (e.g., POROS Protein A chromatography) with chromatography columns (e.g., POROS HS-50 cation exchange chromatography), filtration, ultra-filtration, de-salting and dialysis procedures. In some embodiments, a polypeptide is conjugated to marker sequences, such as a peptide to facilitate purification. An example of a marker amino acid sequence is a hexa-histidine peptide (His6-tag (SEQ ID NO: 223)), which can bind to a nickel-functionalized agarose affinity column with micromolar affinity. As an alternative, a hemagglutinin “HA” tag, which corresponds to an epitope derived from the influenza hemagglutinin protein can be used.

In some embodiments, polypeptides of the disclosure, for example a polypeptide construct comprising a SIRPα D1 domain variant (e.g., any variant provided in Tables 2, 5, and 6) and a fusion partner such as an Fc variant are produced by the cells of a subject (e.g., a human), e.g., in the context of gene therapy, by administrating a vector such as a viral vector (e.g., a retroviral vector, adenoviral vector, poxviral vector (e.g., vaccinia viral vector, such as Modified Vaccinia Ankara (MVA)), adeno-associated viral vector, and alphaviral vector) containing a nucleic acid molecule encoding a polypeptide of the disclosure. The vector, once inside a cell of the subject (e.g., by transformation, transfection, electroporation, calcium phosphate precipitation, direct microinjection, infection, etc.) can be used for the expression of a polypeptide disclosed herein. In some cases, the polypeptide is secreted from the cell. In some embodiments, if treatment of a disease or disorder is the desired outcome, no further action is required. In some embodiments, if collection of the protein is desired, blood is collected from the subject and the protein purified from the blood by various methods.

Methods of Treating Cancer

Provided herein is a method of treating cancer in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic antibody.

Lung Cancer

In some embodiments, provided is a method of treating lung cancer (e.g., non-small cell lung cancer or “NSCLC”), in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide (e.g., fusion polypeptide) comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic antibody that disrupts the interaction between PD-1 and PD-L1, wherein the individual progressed (e.g., demonstrated disease progression) while on (or following) a prior therapy for lung cancer (e.g., NSCLC). In some embodiments, the prior therapy was immune checkpoint inhibitor (CPI) therapy. Additionally or alternatively, in some embodiments, the individual has a PD-L1 tumor proportion score (TPS) of less than 50%. In some embodiments, the individual has not received prior CPI therapy. In some embodiments, the polypeptide (e.g., fusion polypeptide) comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P33 IS, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises an Fc domain variant that is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises the amino acid sequence of SEQ ID NO: 136 or SEQ ID NO: 135. In some embodiments the polypeptide (e.g., fusion polypeptide) forms a homodimer. In some embodiments, the therapeutic antibody that blocks the interaction between PD-1 and PD-L1 is an anti-PD-1 antibody. In some embodiments, the anti-PD-1 antibody is pembrolizumab.

In some embodiments, the pembrolizumab is administered subcutaneously. In some embodiments, the pembrolizumab is administered via intravenous infusion. In some embodiments, the pembrolizumab is administered according to its label instructions. In some embodiments, the pembrolizumab is administered to the individual (e.g., via IV infusion) at a dose of about 200 mg every three weeks (Q3W). In some embodiments, the pembrolizumab is administered to the individual for up to 24 months. In some embodiments, the pembrolizumab is administered to the individual for at least 24 months. In some embodiments, dose modifications of pembrolizumab are made according to the local package insert. Complete information about pembrolizumab preparation, dispensing, dosage, and administration schedule can be found in the local package insert (for the United States, see, e.g., www(dot)accessdata(dot)fda(dot)gov/drugsatfda_docs/label/2016/125514s0121bl(dot)pdf; for Europe, see, e.g., www(dot)ema(dot)europa(dot)eu/en/documents/product-information/keytruda-epar-product-information_en(dot)pdf). In some embodiments, the polypeptide(e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual weekly (i.e., once every 7 days or “qw”), e.g., at a dose of 10.0 mg/kg.

In some embodiments, the lung cancer is NSCLC. In some embodiments, the NSCLC is locally advanced NSCLC. In some embodiments, the NSCLC is metastatic NSCLC. In some embodiments, the individual has metastatic NSCLC and has not demonstrated disease progression within 8 weeks of the start of a prior therapy with a PD-1 or PD-L1 inhibitor. In some embodiments, the individual has a PD-L1 tumor proportion score (TPS) score of ≥1%. In some embodiments, the individual has locally advanced or metastatic NSCLC with a TPS score <50%. In some embodiments, the individual progressed following systemic therapy for their metastatic disease. In some embodiments, the individual has locally advanced or metastatic NSCLC with a TPS score ≥1%, and the individual progressed on prior checkpoint inhibitor (CPI) therapy for NSCLC.

In some embodiments, the prior CPI therapy for lung cancer (e.g., NSCLC) on which the individual progressed was a therapy that comprised treatment with nivolumab, pembrolizumab, atezolizumab, avelumab, durvalumab, cemiplimab, tislelizumab (also known as BGB-A317), toripalimab, sintilimab, camrelizumab (also known as SHR-1210 or INCSHR-1210), spartalizumab (also known as PDR001), TSR-042, and/or FAZ053. In some embodiments, the individual is considered to have progressed on the prior CPI therapy for lung cancer (e.g., NSCLC) if the individual demonstrated progressive disease (PD), e.g., as assessed by Response Evaluation In Solid Tumor (RECIST) criteria (e.g., version 1.0 or 1.1) or modified RECIST criteria (see, e.g., Therasse et al. (2000) J. Natl Cancer Inst. 92: 205-216; Eisenhauer et al. (2009) Eur J. Cancer. 45: 229-247; and Jang et al. (2013) Chin J. Cancer Res. 25(6): 689-694), World Health Organization (WHO) criteria (see, e.g., WHO. Handbook for Reporting Results of Cancer Treatment. Geneva: World Health Organization Offset Publication; 1979. p. 48; and Miller et al. (1981) Cancer. 47: 207-214), or any set of response criteria described in Hwang et al. (2017) “Response Evaluation of Chemotherapy for Lung Cancer.” Tuberc Respir Dis (Seoul). 80(2): 136-142 and references cited therein. In some embodiments, the individual is resistant to standard therapy (e.g., curative therapy) for lung cancer (e.g., NSCLC). In some embodiments, there is no standard therapy (e.g., curative therapy) available to treat the lung cancer (e.g., NSCLC).

In some embodiments, the individual's PD-L1 tumor proportion score (TPS) is assessed using an in vitro diagnostic immunohistochemistry (IHC) assay for detection of PD-L1 in formalin-fixed, paraffin-embedded (FFPE) human tissue sections. In some embodiments, the IHC assay is PD-L1 IHC 22C3 Pharm Dx. PD-L1 IHC 22C3 Pharm Dx is a qualitative immunohistochemical assay in which a murine monoclonal anti-PD-L1 antibody (clone 22C3) is used to detect PD-L1 (i.e., human PD-L1) in formalin-fixed, paraffin-embedded (FFPE) lung cancer tissue (e.g., NSCLC tissue) obtained from an individual (e.g., patient) on the DAKO™ AUTOSTAINER LINK 48 automated staining system using the ENVISION™ FLEX visualization system. In some embodiments, TPS is a measure of PD-L1 protein expression in the lung cancer (e.g., NSCLC) tissue sample from the individual (e.g., patient). In some embodiments, TPS is the percentage of viable tumor cells showing partial or complete membrane staining at any intensity. The specimen should be considered PD-L1 positive if TPS ≥50% of the viable tumor cells exhibit membrane staining at any intensity. In some embodiments, tumor-associated immune cells (such as infiltrating lymphocytes or macrophages) are not included in the scoring for the determination of TPS. In some embodiments the labeling of the lung cancer (e.g., NSCLC) sample is performed by a pathologist. In some embodiments, the staining is assessed via light microscope at 10×-40× magnification. Further details regarding the PD-L1 IHC 22C3 Pharm Dx assay, reagents and equipment to perform the assay, interpretation of assay results, and TPS scoring are provided at www(dot)accessdata(dot)fda(dot)gov/cdrh_docs/pdfi5/p150013b(dot)pdf and Reck et al. (2016) “Pembrolizumab versus Chemotherapy for PD-L1-Positive Non-Small-Cell Lung Cancer.” NEJM. 375: 1823-1833.

Head and Neck Cancer

In some embodiments, provided is a method of treating head and neck cancer (e.g., head and neck squamous cell carcinoma or “HNSSC”) in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide (e.g., fusion polypeptide) comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic antibody that disrupts the interaction between PD-1 and PD-L1, wherein the individual progressed (e.g., demonstrated disease progression) while on a prior therapy or following a prior therapy for head and neck cancer (e.g., HNSCC). In some embodiments, the prior therapy was a platinum-containing therapy. In some embodiments, the polypeptide (e.g., fusion polypeptide) comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises an Fc domain variant that is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises the amino acid sequence of SEQ ID NO: 136 or SEQ ID NO: 135. In some embodiments the polypeptide (e.g., fusion polypeptide) forms a homodimer. In some embodiments, the therapeutic antibody that blocks the interaction between PD-1 and PD-L1 is an anti-PD-1 antibody. In some embodiments, the anti-PD-1 antibody is pembrolizumab. In some embodiments, the HNSCC is PD-L1 negative. In some embodiments, the HNSCC is PD-L1 positive. Further details regarding “PD-L1 negative” and “PD-L1 positive” are provided elsewhere herein

In some embodiments, the pembrolizumab is administered subcutaneously. In some embodiments, the pembrolizumab is administered via intravenous infusion. In some embodiments, the pembrolizumab is administered according to its label instructions. In some embodiments, the pembrolizumab is administered to the individual (e.g., via IV infusion) at a dose of about 200 mg every three weeks (Q3W). In some embodiments, the pembrolizumab is administered to the individual for up to 24 months. In some embodiments, the pembrolizumab is administered to the individual for at least 24 months. In some embodiments, dose modifications of pembrolizumab are made according to the local package insert. Complete information about pembrolizumab preparation, dispensing, dosage, and administration schedule can be found in the local package insert (for the United States, see, e.g., www(dot)accessdata(dot)fda(dot)gov/drugsatfda_docs/label/2016/125514s0121bl(dot)pdf; for Europe, see, e.g., www(dot)ema(dot)europa(dot)eu/en/documents/product-information/keytruda-epar-product-information_en(dot)pdf). In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual weekly (i.e., once every 7 days or “qw”), e.g., at a dose of 10.0 mg/kg.

In some embodiments, the individual has recurrent HNSCC. In some embodiments, the HNSCC is metastatic HNSCC. In some embodiments, the individual received prior therapy with an immune checkpoint inhibitor (“CPI”), i.e., the individual is a “CPI experienced” individual. In some embodiments, the individual has recurrent or metastatic HNSCC and has not demonstrated with disease progression within 8 weeks of the start of a prior therapy with a CPI. In some embodiments, the prior CPI therapy was or comprised a PD-1 or PD-L1 inhibitor. In some embodiments, the prior CPI was or comprised treatment with nivolumab, pembrolizumab, atezolizumab, avelumab, durvalumab, cemiplimab, tislelizumab (also known as BGB-A317), toripalimab, sintilimab, camrelizumab (also known as SHR-1210 or INCSHR-1210), spartalizumab (also known as PDR001), TSR-042, and/or FAZ053. In some embodiments, the individual has not received prior therapy with an CPI (e.g., the individual is “immune checkpoint inhibitor naïve” or “CPI naïve”).

In some embodiments, the prior platinum-containing therapy on which the individual progressed or following which the individual progressed was a therapy that comprised treatment with carboplatin, cisplatin, oxaliplatin, nedaplatin, triplatin tetranitrate, phenanthriplatin, picoplatin, and/or satraplatin. In some embodiments, the individual is considered to have progressed on or following the prior platinum-containing therapy for head and neck cancer (e.g., HNSCC) if the individual demonstrated progressive disease (PD), e.g., as assessed by Response Evaluation In Solid Tumor (RECIST) criteria (e.g., version 1.0 or 1.1) or modified RECIST criteria (see, e.g., Therasse et al. (2000) J. Natl Cancer Inst. 92: 205-216; Eisenhauer et al. (2009) Eur J. Cancer. 45: 229-247; and Jang et al. (2013) Chin J. Cancer Res. 25(6): 689-694), World Health Organization (WHO) criteria (see, e.g., WHO. Handbook for Reporting Results of Cancer Treatment. Geneva: World Health Organization Offset Publication; 1979. p. 48; and Miller et al. (1981) Cancer. 47: 207-214), or a set of response criteria described in Wray et al. (2016) “Therapy Response Assessment and Patient Outcomes in Head and Neck Squamous Cell Carcinoma: FDG PET Hopkins Criteria Versus Residual Neck Node Size and Morphologic Features.” Am J. Roentgenology. 207:641-647. In some embodiments, the individual is resistant to standard therapy (e.g., curative therapy) for head and neck cancer (e.g., HNSCC). In some embodiments, there is no standard therapy (e.g., curative therapy) available to treat the head and neck cancer (e.g., HNSCC).

Gastric/Gastroesophageal (GEJ) Cancer

In some embodiments, provided is a method of treating gastric/gastroesophageal (GEJ) cancer (e.g., HER2-positive gastric or GEJ adenocarcinoma) in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide (e.g., fusion polypeptide) comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic anti-HER2 antibody, wherein the individual progressed (e.g., demonstrated disease progression) during a prior therapy or following a prior therapy for gastric/GEJ cancer (e.g., gastric/GEJ adenocarcinoma), and wherein the prior therapy was an anti-HER2 antibody therapy and/or a fluoropyrimidine-based therapy. In some embodiments, the polypeptide (e.g., fusion polypeptide) comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises an Fc domain variant that is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises the amino acid sequence of SEQ ID NO: 136 or SEQ ID NO: 135. In some embodiments the polypeptide (e.g., fusion polypeptide) forms a homodimer. In some embodiments, the therapeutic anti-HER2 antibody that administered to the individual in combination with the fusion polypeptide is trastuzumab.

In some embodiments, the trastuzumab is administered subcutaneously. In some embodiments, the trastuzumab is administered via intravenous infusion. In some embodiments, the trastuzumab is administered according to its label instructions. In some embodiments, the trastuzumab is administered to the individual (e.g., via intravenous infusion) every three weeks (Q3W). In some embodiments, the initial (i.e., first) dose of trastuzumab is about 8 mg/kg, and every subsequent dose (i.e., following the first dose) is about 6 mg/kg. In some embodiments, dose modifications of trastuzumab are made according to the local package insert. Complete information about trastuzumab preparation, dispensing, dosage, and administration schedule can be found in the local package insert (for the United States, see, e.g., www.accessdata(dot)fda(dot)gov/drugsatfda_docs/label/2017/103792s53371bl(dot) pdf; for Europe, see, e.g., www(dot)ema(dot)Europa(dot)eu/en/documents/product-information/herceptin-epar-product-information_en(dot)pdf). In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual weekly (i.e., once every 7 days or “qw”), e.g., at a dose of 10.0 mg/kg.

In some embodiments HER2 status (i.e., HER2-positive status or HER2-negative status) of the gastric or GEJ cancer is assessed via immunohistochemistry (IHC) or in situ hybridization (ISH, e.g., fluorescent ISH or “FISH”). In some embodiments, the HER2 status of the gastric or GEJ cancer is evaluated according to criteria described in Abrahao-Machado et al. (2016) World J. Gastroenterol. 22(19): 4619-4625 and references cited therein. In some embodiments, the HER2-positive gastric or HER2-positive GEJ cancer is HER2-positive gastric/HER2-positive GEJ adenocarcinoma. In some embodiments, the HER2-positive gastric/HER2-positive GEJ cancer (e.g., adenocarcinoma) is metastatic gastric/GEJ cancer (e.g., metastatic adenocarcinoma). In some embodiments, the individual has metastatic gastric/GEJ cancer (e.g., adenocarcinoma) and has demonstrated a response of at least stable disease (SD) (i.e., a response better than progressive disease (PD)) as the best response to a prior therapy.

In some embodiments, the individual progressed (e.g., demonstrated disease progression) during prior therapy or following prior therapy with an anti-HER2 antibody. In some embodiments, the prior anti-HER2 antibody therapy comprised treatment with trastuzumab, pertuzumab, and/or margetuximab. Additionally or alternatively, in some embodiments, the individual progressed (e.g., demonstrated disease progression) during prior therapy or following prior therapy with a fluoropyrimidine-based therapy. In some embodiments the prior fluoropyrimidine-based therapy comprised treatment with, e.g., capecitabine, floxuridine, 4-fluorouracil, 5-fluorouracil, carmofur, doxifluridine, ftorafur (Tegafur), UFT (i.e., a 1:4 molar combination of ftorafur with uracil), S-1 (a combination of ftorafur, gimeracil, and oteracil), and/or FOLFOX (a combination of folinic acid, 5-fluorouracil, and oxaliplatin). In some embodiments, the individual progressed while on therapy or following therapy with an anti-HER2 antibody and a fluoropyrimidine-based therapy. In some embodiments, the anti-HER2 antibody and the fluoropyrimidine-based therapy were administered in combination (e.g., wherein both agents were part of a single treatment regimen). In some embodiments the anti-HER2 antibody and the fluoropyrimidine-based therapy were each administered in separate treatment regimens (e.g., in two separate prior therapies or two separate prior lines of therapy).

In some embodiments, the individual is considered to have progressed on the prior anti-HER2 antibody therapy and/or the prior fluoropyrimidine-based therapy for gastric/GEJ cancer (e.g., HER2-positive gastric/GEJ cancer) if the individual demonstrated progressive disease (PD), e.g., as assessed by Response Evaluation In Solid Tumor (RECIST) criteria (e.g., version 1.0 or 1.1) or modified RECIST criteria (see, e.g., Therasse et al. (2000) J. Natl Cancer Inst. 92: 205-216; Eisenhauer et al. (2009) Eur J. Cancer. 45: 229-247; and Jang et al. (2013) Chin J. Cancer Res. 25(6): 689-694), World Health Organization (WHO) criteria (see, e.g., WHO. Handbook for Reporting Results of Cancer Treatment. Geneva: World Health Organization Offset Publication; 1979. p. 48; and Miller et al. (1981) Cancer. 47: 207-214), or any set of response criteria described in Kurokawa et al. (2013) Ann Surg Oncol. 20(9): 3009-3014; Yanagawa et al. (2012) J Nucl Med. 53(6): 872-880; Lordick et al. (2016) Ann Oncol. 27(suppl 5): v50-v57; or Kim et al. (2015) Oncology. 88:69-75. In some embodiments, the individual is resistant to standard therapy (e.g., curative therapy) for gastric/GEJ cancer (e.g., HER2-positive gastric/HER2-positive GEJ cancer). In some embodiments, there is no standard therapy (e.g., curative therapy) available to treat the gastric/GEJ cancer (e.g., HER2-positive gastric/HER2-positive GEJ cancer).

Lymphomas

(i) Aggressive Non-Hodgkin Lymphoma

In some embodiments, provided is a method of treating aggressive non-Hodgkin lymphoma or “NHL” (e.g., diffuse large B-cell lymphoma (“DLBCL”, e.g., de novo DLBCL or transformed DLBCL or mantle cell lymphoma (MCL)) in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide (e.g., fusion polypeptide) comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic anti-CD20 antibody, wherein the aggressive NHL is relapsed and/or refractory aggressive NHL (e.g., wherein the individual has relapsed during or following a prior treatment for aggressive NHL and/or has been refractory to a prior treatment for aggressive NHL) and wherein there is no available therapy (e.g., curative therapy) for the aggressive NHL (e.g., DLBCL, such as de novo DLBCL, transformed DLBCL, or mantle cell lymphoma). In some embodiments, the polypeptide (e.g., fusion polypeptide) comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises an Fc domain variant that is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises the amino acid sequence of SEQ ID NO: 136 or SEQ ID NO: 135. In some embodiments the polypeptide (e.g., fusion polypeptide) forms a homodimer. In some embodiments, the therapeutic anti-CD20 antibody is rituximab. In some embodiments, the aggressive NHL is diffuse large B-cell lymphoma (DLBCL), e.g., de novo DLBCL or transformed DLBCL. In some embodiments, the aggressive NHL is mantle cell lymphoma (MCL).

In some embodiments, the rituximab is administered subcutaneously. In some embodiments, the rituximab is administered via intravenous infusion. In some embodiments, the rituximab is administered according to its label instructions. In some embodiments, the rituximab is administered to the individual (e.g., via intravenous infusion) at a dose of about 375 mg/m². In some embodiments, the first four doses (i.e. doses 1-4) of rituximab are administered to the individual (e.g., at a dose of about 375 mg/m²) once a week (e.g., once every 7 days or “qw”) for the first four weeks (e.g., 28 days) of treatment, and the next eight doses (i.e., doses 5-12) are administered to the individual once every four weeks (e.g., every 28 days or “q4w”). In some embodiments, the first four doses (i.e. doses 1-4) of rituximab are administered to the individual (e.g., at a dose of about 375 mg/m²) once a week (e.g., once every 7 days or “qw”) for the first four weeks (e.g., 28 days) of treatment, and the next four doses (i.e., doses 5-8) are administered to the individual once every four weeks (e.g., every 28 days or “q4w”). In some embodiments, dose modifications of rituximab are made according to the local package insert. Complete information about rituximab preparation, dispensing, dosage, and administration schedule can be found in the local package insert (for the United States, see, e.g., www(dot)accessdata(dot)fda(dot)gov/drugsatfda_docs/label/2012/103705s5367s53881bl(dot)pdf; for Europe, see, e.g., www(dot)ema(dot)europa(dot)eu/en/documents/product-information/mabthera-epar-product-information_en(dot)pdf). In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual weekly (i.e., once every 7 days or “qw”), e.g., at a dose of 10.0 mg/kg or 15.0 mg/kg.

In some embodiments, the individual is diagnosed as having de novo DLBCL (e.g., de novo relapsed and/or refractory DLBCL) if the individual had no prior history of lymphoma. In some embodiments, the individual is diagnosed as having transformed DLBCL if the individual has a history of lymphoma, e.g., indolent lymphoma, such as marginal zone lymphoma, lymphoplasmacytic lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia, follicular lymphoma, or lymphocyte predominant Hodgkin lymphoma. In some embodiments, the individual is diagnosed as having mantle cell lymphoma (MCL) if the individual is found to have one or more of the following chromosomal abnormalities: t(11;14), t(14;18). In some embodiments, the individual is diagnosed with mantle cell lymphoma (MCL) if SOX11 overexpression is detected in a sample of leukemic cells from the individual. Other criteria for diagnosing de novo DLBCL, transformed DLBCL, and MCL are known in the art and routinely used by skilled artisans. See, e.g., Balsas et al. (2017) Blood. 130(4):501-513; National Guideline Alliance (UK). Non-Hodgkin's Lymphoma: Diagnosis and Management. London: National Institute for Health and Care Excellence (UK); 2016 July (NICE Guideline, No. 52.) 3, Staging; Dreyling et al. Am Soc Clin Oncol Educ Book. 2014:191-8; and others.

In some embodiments, the individual is considered to have relapsed following a prior therapy for aggressive NHL (e.g., de novo DLBCL, transformed DLBCL, or MCL) if the individual achieved a therapeutic response of least stable disease (SD) to the prior therapy, but stopped responding (e.g., demonstrated disease progression) within about any one of, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 months following the cessation of the prior therapy. In some embodiments, the individual is considered to be refractory to a prior therapy for aggressive NHL if the individual was unresponsive to the prior therapy (e.g., failed to achieve a therapeutic response of at least stable disease (SD) during or following the prior therapy). In some embodiments, the therapeutic response to a therapy for aggressive NHL is assessed according to the criteria described in Cheson et al. (2014) “Recommendations for Initial Evaluation, Staging and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification.” J. Clin Oncol. 32: 3059-3067.

In some embodiments, the individual was refractory to or had relapsed following treatment with at least one prior therapy (e.g., at least one prior standard approved therapy, at least two prior standard approved therapies, at least three standard approved therapies etc.) for aggressive NHL. Standard therapies for DLBCL (e.g., de novo or transformed DLBCL) and MCL include, but are not limited to, e.g., rituximab, RCHP (i.e., rituximab, cyclophosphamide, doxorubicin, and prednisone); R-CHOP (i.e., rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone); R-CHOEP (i.e., rituximab, cyclophosphamide, doxorubicin, vincristine, etoposide, and prednisone that is typically administered in 21-day cycles for 6 cycles); EPOCH-R (i.e., rituximab, cyclophosphamide, doxorubicin, vincristine, etoposide, and prednisone that is typically administered as a continuous infusion over 4 days); R-GCVP (i.e., rituximab, gemcitabine, cyclophosphamide, vincristine, and prednisolone); R-CEPP (i.e., rituximab, cyclophosphamide, etoposide, procarbazine, and prednisone); R-CEOP (i.e., rituximab, cyclophosphamide, epirubicin, vincristine, and prednisone); R-CVP (i.e., rituximab, cyclophosphamide, vincristine, and prednisone); rituximab and bendamustine; rituximab and lenalidomide: DHAP (i.e., dexamethasone, high-dose cytarabine and cisplatin); RDHAP (i.e., DHAP in combination with rituximab); ICE (i.e., ifosfamide, carboplatin, and etoposide); RICE (i.e., ICE in combination with rituximab); DICE (i.e., ICE in combination with dexamethasone); DICE and mesna; BEAM (i.e., carmustine, etoposide, cytarabine, and melphalan); R-BEAM (i.e., BEAM in combination with rituximab); ESHAP (i.e., etoposide, solumedrol, high-dose cytarabine, and cisplatin); R-ESHAP (i.e., ESHAP in combination with rituximab); MIME (i.e., methyl-glyoxal-bis(guanylhydrazone), ifosfamide, methotrexate, and etoposide); parsaclisib (also known as INCB050465); MATRIX (i.e., methotrexate, cytarabine, thiotepa, and rituximab); hyper-CVAD or HCVAD (i.e., hyper-fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone) RHCVAD (i.e., HCVAD in combination with rituximab); RHCVAD/MA (i.e., RHCVAD alternating with methotrexate and cytarabine); DHAP (i.e., dexamethasone, cisplatin, and cytarabine); R-DHAP (i.e., DHAP in combination with rituximab); ibrutinib; rituximab, obinituzumab, CVAD (i.e., cyclophosphamide, doxorubicin, vincristine, and prednisolone); RCVAD (i.e., CVAD in combination with rituximab); GemOx (i.e., gemcitabine and oxaliplatin); R-GemOx (i.e., GemOx in combination with rituximab); DHAX (i.e., dexamethasone, cytarabine, and oxaliplatin); R-DHAX (i.e., DHAX in combination with rituximab); GIFOX (i.e., gemcitabine, ifosfamide, and oxaliplatin); RGIFOX (i.e., GIFOX in combination with rituximab); bortezomib and GIFOX; ASCT (i.e., autologous stem cell transplantation) HD-ASCT (i.e., ASCT in combination with high dose therapy, e.g., high-dose chemotherapy); CAR T-cell therapy (e.g., tisagenlecleucel or axicabtagene); brentuximab vedotin, and lenalidomide. In some embodiments, the prior therapy for aggressive NHL comprised any two or more of the preceding treatments (given together in a single treatment regimen, or given in separate treatment regimens). In some embodiments, there are no available treatment options (e.g., curative treatment options) for the individual with aggressive NHL (e.g., relapsed/refractory aggressive NHL). In some embodiments, the individual has DLBCL (e.g., de novo DLBCL or transformed DLBCL) or MCL for which no curative therapy is available. In some embodiments, the individual has DLBCL (e.g., de novo DLBCL or transformed DLBCL) or MCL that has relapsed following or has been refractory to standard approved therapies (e.g., curative therapies).

(ii) Indolent Lymphoma

In some embodiments, provided is a method of treating indolent lymphoma in an individual (e.g., a human individual) that comprises administering to the individual an effective amount of (a) a polypeptide (e.g., fusion polypeptide) comprising a SIRPα D1 domain variant (e.g., a SIRPα D1 domain variant described herein) and an Fc domain variant (e.g., an Fc domain variant described herein) and (b) a therapeutic anti-CD20 antibody, wherein the indolent lymphoma is relapsed and/or refractory indolent lymphoma (e.g., wherein the individual has relapsed during or following at least one prior treatment, e.g., a standard approved therapy, for indolent lymphoma and/or or has been refractory to at least one prior treatment, e.g., a standard approved therapy, for indolent lymphoma. In some embodiments, the individual has relapsed during or after more than one standard approved therapy (e.g., 2, 3, or more standard therapies) for indolent lymphoma and/or is refractory to more than one standard therapy (e.g., 2, 3, or more standard therapies, e.g., curative therapies) for indolent lymphoma In some embodiments, the polypeptide (e.g., fusion polypeptide) comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises a SIRPα D1 domain variant that comprises the amino acid sequence of SEQ ID NO: 81 or SEQ ID NO: 85. In some embodiments the polypeptide (e.g., fusion polypeptide) administered to the individual comprises an Fc domain variant that is a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments, the polypeptide (e.g., fusion polypeptide) administered to the individual comprises the amino acid sequence of SEQ ID NO: 136 or SEQ ID NO: 135. In some embodiments the polypeptide (e.g., fusion polypeptide) forms a homodimer. In some embodiments, the therapeutic anti-CD20 antibody is rituximab.

In some embodiments, the indolent lymphoma is an indolent non-Hodgkin lymphoma (NHL). In some embodiments, the indolent NHL is marginal zone lymphoma (MZL). In some embodiments, the indolent NHL is follicular lymphoma (FL). Details regarding the diagnosis and classification of marginal zone lymphoma and follicular lymphoma (as well as DLBCL, and mantle cell lymphoma) are provided in, e.g., Ayyappan et al. (2018) Curr Oncol Rep. 20(4): 33; Dreyling et al. (2013) ESMO Consensus Guidelines: Marginal Cell Lymphoma, Mantle Cell Lymphoma, Peripheral T-cell Lymphoma.” Ann Oncol. 24(4): 857-877; Vose, J M (2017) “Mantle cell lymphoma: 2017 update on diagnosis, risk-stratification, and clinical management.” Am J. Hematol. 92(8): 806-813; Ciobanu et al. (2013) “Indolent Lymphoma: Diagnosis and Prognosis in Medical Practice.” Maedica (Buchar) 8(4) 338-342, and others.

In some embodiments, the individual is considered to have relapsed following a prior therapy for indolent lymphoma (e.g., indolent NHL) if the individual achieved a therapeutic response of least stable disease (SD) to the prior therapy, but stopped responding (e.g., demonstrated disease progression) within about any one of, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 months following the cessation of the prior therapy. In some embodiments, the individual is considered to be refractory to a prior therapy for indolent lymphoma (e.g., indolent NHL) if the individual was unresponsive to the prior therapy (e.g., failed to achieve a therapeutic response of at least stable disease (SD) during or following the prior therapy). In some embodiments, the therapeutic response to therapy for indolent lymphoma (e.g., indolent NHL) is assessed according to the criteria described in Cheson et al. (2014) “Recommendations for Initial Evaluation, Staging and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification.” J. Clin Oncol. 32: 3059-3067.

In some embodiments of any of the methods of treatment provided herein, the fusion polypeptide is supplied for use (e.g., intravenous administration) in a 100 mg/5 ml Type I clear glass vial sealed with a 20 mm Teflon coated rubber septum stopper and aluminum seal. In some embodiments, the fusion polypeptide is supplied for use (e.g., intravenous administration) in a 400 mg/20 ml Type I clear glass vial sealed with a 20 mm Teflon coated rubber septum stopper and aluminum seal. In some embodiments, the fusion polypeptide is stored in its original container at 2-8*C (36-46° F.) until use (e.g., intravenous administration).

In some embodiments of any of the methods of treatment described herein, the polypeptide (e.g., fusion polypeptide comprising a SIRPα D1 domain variant and an Fc domain variant) is administered subcutaneously. In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered via intravenous infusion. In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual (e.g., human individual) at a dose of 0.3 mg/kg, 1.0 mg/kg, 3.0 mg/kg, 10.0 mg/kg, 15.0 mg/kg, or 30.0 mg/kg, including any range in between these values. In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered (e.g., via intravenous infusion) to the individual weekly (i.e., once every 7 days or “qw”), e.g., at a dose of 0.3 mg/kg, 1.0 mg/kg, 3.0 mg/kg, 10.0 mg/kg, 15.0 mg/kg, or 30.0 mg/kg, including any range in between these values. In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered to the individual (e.g., via intravenous infusion) every other week (i.e., once every 14 days or “q2w” or “QoW”), e.g., at a dose of 0.3 mg/kg, 1.0 mg/kg, 3.0 mg/kg, 10.0 mg/kg, 15.0 mg/kg, or 30.0 mg/kg, including any range in between these values. In some embodiments, on the days when the dosing schedules of the polypeptide (e.g., fusion polypeptide) and the therapeutic antibody (e.g., the anti-PD1 antibody (pembrolizumab), the anti-HER2 antibody (trastuzumab), or the anti-CD20 antibody (rituximab)) coincide, the polypeptide and the therapeutic antibody are administered sequentially. In some embodiments, the polypeptide (e.g., fusion polypeptide) is administered prior (e.g., about 30 minutes prior) to the therapeutic antibody. In some embodiments, in the event of a missed dose of the polypeptide, the therapeutic antibody is administered about 24 hours after the missed dose.

In some embodiments, the therapeutic response of an individual having NSCLC, HNSCC, gastric cancer or GEJ cancer to a method of treatment provided herein is assessed according to the RECIST version 1.1 criteria, e.g., as described in Therasse et al. (2000) J. Natl Cancer Inst. 92: 205-216; Eisenhauer et al. (2009) Eur J. Cancer. 45: 229-247, the immune-related response criteria derived from RECIST 1.1 (irRECIST), e.g., as adapted from Nishino, et al. (2013) “Developing a Common Language for Tumor Response to Immunotherapy: Immune-Related Response Criteria Using Unidimensional Measurements.” Clinical Cancer Research 19(14):3936-43. In some embodiments, the therapeutic response of an individual having aggressive lymphoma (e.g., aggressive NHL such as DLBCL or MCL) to a method of treatment provided herein is assessed according to the Lugano criteria, e.g., as described in Cheson et al. (2014) “Recommendations for Initial Evaluation, Staging and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification.” J. Clin Oncol. 32: 3059-3067. In some embodiments, the therapeutic response of an individual having indolent lymphoma (e.g., indolent NHL such as FL or MZL) to a method of treatment provided herein is assessed according to the Lugano criteria (see Cheson et al 2014).

In some embodiments, the individual receiving treatment for HNSCC, NSCLC, gastric cancer, or GEJ cancer has at least one measurable lesion as defined by RECIST version 1.1 criteria, e.g., as described in Therasse et al. (2000) J. Natl Cancer Inst. 92: 205-216; Eisenhauer et al. (2009) Eur J. Cancer. 45: 229-247. In some embodiments, the individual receiving treatment for lymphoma (e.g., aggressive lymphoma (such as DLBCL or MCL) or indolent lymphoma (such as FL or MZL) has at least one measurable lesion as defined by Lugano criteria e.g., as described in Cheson et al. (2014) “Recommendations for Initial Evaluation, Staging and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification.” J. Clin Oncol. 32: 3059-3067.

In some embodiments, the individual receiving treatment according to a method herein has adequate bone marrow function, renal function, liver function, and cardiac function. In some embodiments, the individual has an Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) score of 0 or 1 (see, e.g., www(dot)npcrc(dot)org/files/news/ECOG)_performance_status(dot)pdf). In some embodiments, the individual does not have symptomatic central nervous system (CNS) metastases or leptomeningeal disease requiring steroids. In some embodiments, the individual receiving treatment for lung cancer according to a method herein (e.g., NSCLC) does not have ALK or EGFR genomic tumor aberrations. In some embodiments, an individual receiving treatment according to a method herein does not have a history of (non-infectious) pneumonitis that required steroids or has current pneumonitis. In some embodiments, the individual receiving treatment according to a method herein does not have high grade lymphoma (e.g., Burkitts lymphoma, lymphoblastic lymphoma, or Richter's transformation), chronic lymphocytic leukemia, or plasma cell leukemia. In some embodiments, the individual has not undergone high-dose chemotherapy requiring allogeneic stem cell rescue. In some embodiments, the individual receiving treatment for lung cancer (e.g., NSCLC), head and neck cancer (e.g., HNSCC), or gastric/GEJ cancer (e.g., HER2-positive gastric/GEJ adenocarcinoma) according to a method herein has not undergone prior irradiation to >25% of the bone marrow. In some embodiments, the individual has not received radiotherapy within 2 weeks of start of treatment. In some embodiments, the individual has not received prior treatment with any anti-CD47 or anti-SIRP agent. In some embodiments, the individual has not received systemic anti-cancer therapy within 4 weeks of starting treatment (6 weeks for mitomycin C or nitrosoureas). In some embodiments, the individual does not have an intolerance to or has not had a severe allergic or anaphylactic reaction to antibodies or infused therapeutic protein(s) or any excipients in the formulation(s) comprising the therapeutic protein. In some embodiments, the individual has not discontinued treatment due to a Grade 3 or higher immune-related adverse event (AE) from prior therapy with an anti-PD-1, anti-PD-L1, or anti PD-L2 agent or with an agent aiming to modulate another immune cell target (e.g. CTLA-1, OX40, 41BB, etc.). In some embodiments, the individual has not received experimental antibodies or live vaccines (e.g., including, but not limited to vaccines for measles, mumps, rubella, varicella/zoster, yellow fever, rabies, Bacillus Calmette-Guérin (BCG), typhoid, and intranasal influenza vaccines). In some embodiments, the individual is not undergoing current active therapy for the primary diagnosis (e.g., lung cancer (NSCLC), head and neck cancer (HNSCC), gastric/GEJ cancer (HER2-positive gastric/GEJ adenocarcinoma), aggressive lymphoma (de novo DLBCL or transformed DLBCL or mantle cell lymphoma), or indolent lymphoma (e.g., indolent NHL, such as marginal zone lymphoma or follicular lymphoma). In some embodiments, the individual has not received a blood product transfusion within 14 days of the start of treatment. In some embodiments, the individual does not have a history of active autoimmune disorders (including but not limited to, e.g., Crohn's Disease, rheumatoid arthritis, scleroderma, systemic lupus erythematosus, Grave's disease, autoimmune hemolytic anemia, autoimmune thrombocytopenia) and other conditions that compromise or impair the immune system (other than hypogammaglobulinemia). In some embodiments, the individual does not have an active, uncontrolled, clinically significant bacterial, fungal, or viral infection, including hepatitis B (HBV), hepatitis C (HCV), known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS)-related illness. In some embodiments, the individual does not have active graft versus host disease (GVHD) or is not undergoing immunosuppression therapy for GVHD. In some embodiments, the individual has not had any of the following in the previous 12 months: myocardial infarction, severe/unstable angina, coronary/peripheral artery bypass graft, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, deep venous thrombosis, or symptomatic pulmonary embolism. In some embodiments, the individual has not been diagnosed with any other malignancy within the last 3 years prior to the start of treatment, except for, e.g., adequately treated non-melanomatous skin cancer, or carcinoma in situ (e.g., breast carcinoma, cervical cancer in situ) that have undergone potentially curative therapy.

Kits and Articles of Manufacture

In another embodiment of the invention, an article of manufacture or a kit is provided comprising a polypeptide (e.g., a fusion polypeptide described herein) comprising a SIRPα D1 domain variant and an Fc domain variant. In some embodiments, the SIRPα D1 domain variant comprises the amino acid sequence selected from the group consisting of: SEQ ID NO: 81, SEQ ID NO: 85. In some embodiments, the Fc domain variant is (i) a human IgG1 Fc region comprising L234A, L235A, G237A, and N297A mutations, wherein numbering is according to the EU index of Kabat; (ii) a human IgG2 Fc region comprising A330S, P331S, and N297A mutations, wherein numbering is according to the EU index of Kabat; (iii) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, and delG236 mutations, wherein numbering is according to the EU index of Kabat; or (iv) a human IgG4 Fc region comprising S228P, E233P, F234V, L235A, delG236, and N297A mutations, wherein numbering is according to the EU index of Kabat. In some embodiments, the Fc domain variant comprises the amino acid sequence of SEQ ID NO: 91. In some embodiments the polypeptide comprises the amino acid sequence of SEQ ID NO: 135 or SEQ ID NO: 136. In some embodiments, the polypeptide forms a homodimer. In some embodiments, the kit or article of manufacture is for use according to a method of treatment provided herein.

In some embodiments, the kit or article of manufacture further comprises an anti-PD1 antibody. In some embodiments, the anti-PD1 antibody is pembrolizumab. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of lung cancer (e.g., NSCLC, including metastatic NSCLC) in an individual according to a method herein. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of lung cancer (e.g., NSCLC, including metastatic NSCLC) in an individual has received prior therapy for NSCLC. In some embodiments, the individual has progressed (e.g., demonstrated disease progression) during (or following) a prior therapy (e.g., prior immune checkpoint inhibitor therapy) for lung cancer. In some embodiments, the individual has a PD-L1 tumor proportion score (TPS) of less than 50%. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of HNSCC in an individual according to a method herein. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of HNSCC in an individual who has received prior immune checkpoint inhibitor therapy (e.g., for HNSCC). In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of HNSCC in an individual who has not received prior immune checkpoint inhibitor therapy (e.g., for HNSCC). In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-PD1 antibody (e.g., pembrolizumab) to treat or delay progression of head and neck cancer (e.g., HNSCC, including metastatic HNSCC) in an individual who has progressed (e.g., demonstrated disease progression) on (or following) a prior platinum therapy (e.g., a platinum-containing therapy). In some embodiments, the kit or article of manufacture further comprises instructions for administering the pembrolizumab at a dose of 200 mg every 3 weeks (Q3W) by IV infusion. In some embodiments, the kit or article of manufacture further comprises instructions for administering the polypeptide (e.g., fusion polypeptide) at a dose of 10 mg/kg every week (QW) by IV infusion.

In some embodiments, the kit or article of manufacture further comprises an anti-HER2 antibody. In some embodiments, the anti-HER2 antibody is trastuzumab. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-HER2 antibody (e.g., trastuzumab) to treat or delay progression of HER2-positive gastric or HER2-positive GEJ cancer (e.g., HER2-positive gastric adenocarcinoma or HER2-positive GEJ adenocarcinoma) in an individual according to a method provided herein. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-HER2 antibody (e.g., trastuzumab) to treat or delay progression of HER2-positive gastric or HER2-positive GEJ cancer (e.g., HER2-positive gastric adenocarcinoma or HER2-positive GEJ adenocarcinoma) in an individual who has progressed (e.g., demonstrated disease progression) while on (or following) a prior therapy for gastric or GEJ cancer. In some embodiments the prior therapy comprised anti-HER2 antibody and/or a prior fluoropyrimidine-based therapy. In some embodiments, the kit or article of manufacture further comprises instructions for administering the trastuzumab via intravenous infusion once every three weeks (q3W), wherein the initial dose of trastuzumab is 8 mg/kg and each subsequent dose of trastuzumab (i.e., following the initial dose) is 6 mg/kg. In some embodiments, the kit or article of manufacture further comprises instructions for administering the polypeptide (e.g., fusion polypeptide) at a dose of 10 mg/kg every week (QW) by IV infusion.

In some embodiments, the kit or article of manufacture further comprises an anti-CD20 antibody. In some embodiments, the anti-CD20 antibody is rituximab. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-CD20 antibody (e.g., rituximab) to treat or delay progression of aggressive non-Hodgkin lymphoma or “NHL” (e.g., de novo DLBCL or transformed DLBCL, or mantle cell lymphoma) in an individual according to a method herein. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-CD20 antibody (e.g., rituximab) to treat or delay progression of aggressive non-Hodgkin lymphoma or “NHL” (e.g., de novo DLBCL or transformed DLBCL, or mantle cell lymphoma) in an individual who has relapsed or was refractory to prior therapy (e.g., prior standard therapy/curative therapy) for aggressive NHL, or in an individual for whom there is no available therapy (e.g., curative therapy) for aggressive NHL. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-CD20 antibody (e.g., rituximab) to treat or delay progression of indolent lymphoma (e.g., indolent NHL, such as marginal zone lymphoma or follicular lymphoma) in an individual according to a method herein. In some embodiments, the kit comprises a package insert or label with instructions for using the polypeptide (e.g., fusion polypeptide) in conjunction with the anti-CD20 antibody (e.g., rituximab) to treat or delay progression of indolent lymphoma (e.g., indolent NHL, such as marginal zone lymphoma or follicular lymphoma) in an individual who has relapsed or was refractory to prior therapy (e.g., prior standard therapy, e.g., curative therapy) for indolent lymphoma (e.g., indolent NHL), or in an individual for whom there is no available therapy (e.g., curative therapy) for indolent lymphoma (e.g., indolent NHL). In some embodiments, the kit or article of manufacture further comprises instructions for administering the rituximab to the individual at a dose of 375 mg/m²once a week (e.g., once every 7 days or “qw”) for the first four weeks (e.g., 28 days) of treatment, and then administering the rituximab to the individual at a dose of 375 mg/m²once every four weeks (e.g., every 28 days or “q4w”) for up to four additional doses following the first four doses, or for up to 8 additional doses following the first four doses. In some embodiments, the kit or article of manufacture further comprises instructions for administering the polypeptide (e.g., fusion polypeptide) at a dose of 10 mg/kg or 15 mg/kg every week (QW) by IV infusion.

In some embodiments of any of the kits or articles of manufacture provided herein, the polypeptide (e.g., fusion polypeptide) and the therapeutic antibody (e.g., pembrolizumab, trastuzumab, or rituximab) are in the same container or separate containers. Suitable containers include, for example, bottles, vials, bags and syringes. The container may be formed from a variety of materials such as glass, plastic (such as polyvinyl chloride or polyolefin), or metal alloy (such as stainless steel or hastelloy). In some embodiments, the container holds the formulation and the label on, or associated with, the container may indicate directions for use. The article of manufacture or kit may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, syringes, and package inserts with instructions for use. In some embodiments, the article of manufacture further includes one or more of another agent (e.g., a chemotherapeutic agent, and anti-neoplastic agent). Suitable containers for the one or more agents include, for example, bottles, vials, bags and syringes.

The specification is considered to be sufficient to enable one skilled in the art to practice the invention. Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.

EXAMPLES
Example 1: A Phase 1 Study of Drug A in Combination with Established Anticancer Antibodies in Patients with Advanced Malignancies

This Example describes a Phase 1 clinical study that evaluated the safety, efficacy, pharmacodynamics (PD) and pharmacokinetics (PK) of Drug A in combination with pembrolizumab, trastuzumab, or rituximab for patients with advanced malignancies. Drug A is a fusion protein consisting of a high affinity CD47-binding SIRPα D1 domain variant fused to a human immunoglobulin Fc domain variant that is modified to eliminate binding to Fc gamma receptors (FIG. 1).

Study Objectives

Primary Objective

The primary objective of this study was to evaluate the safety and tolerability of Drug A administered once every week and/or every 2 weeks in combination with pembrolizumab, trastuzumab, or rituximab in patients with advanced malignancies including non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), HER2-overexpressing gastric cancer, and non-Hodgkin lymphoma (NHL).

Secondary Objectives

The secondary objectives of this study were:

- To evaluate the anti-tumor effect of Drug A in combination with anti-cancer therapeutics in patients with advanced malignancies.
- To evaluate the overall safety profile of Drug A in combination with other anti-cancer therapeutics.
- To characterize the maximum tolerated dose (MTD)/optimal biological dose (OBD) of Drug A in combination with anti-cancer therapeutic agents.
- To characterize the single and multiple dose pharmacokinetics of Drug A in combination with the anti-cancer therapeutics pembrolizumab, trastuzumab or rituximab.
- To evaluate the immunogenicity of Drug A.

Exploratory Objectives

The exploratory objective of this study was to explore the pharmacodynamic effect of Drug A in combination with anti-cancer therapeutics in patients with advanced malignancies.

Patients

Inclusion Criteria

All patients met the following criteria for the dose escalation phase of the study:

- Histological or cytological diagnosis of advanced/metastatic solid tumor malignancy or relapsed/refractory CD20⁺ B Cell non Hodgkin lymphoma that:
  - Was resistant to standard therapy or for which no curative therapy was available; or
  - Met any criteria (a-d) for dose expansion described below
- Lesions could be measurable or non-measurable.

All patients met the following criteria for the dose expansion phase of the study:

- a) Locally advanced or metastatic NSCLC (TPS ≥1%) which had progressed on prior checkpoint therapy, OR Locally advanced or metastatic NSCLC (TPS <50%) that had progressed following systemic therapy for their metastatic disease; patients were suitable for treatment with pembrolizumab; Or
- b) Recurrent or metastatic HNSCC with disease progression on or after platinum-containing chemotherapy and were suitable for treatment with pembrolizumab; Or
- c) HER2 overexpressing metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma that had progressed following systemic therapy with a fluoropyrimidine-containing regimen and/or therapy with an anti-HER2 antibody for their metastatic disease and were suitable for treatment with trastuzumab;
- d) Relapsed or refractory, de novo or transformed diffuse large B-cell lymphoma (DLBCL), or mantle cell lymphoma for which no curative therapy was available; OR indolent lymphoma (Marginal zone, follicular) that was relapsed or refractory to standard approved therapies.
- Patients had at least one measurable lesion as defined by RECIST version 1.1 or Lugano criteria (2014).

In addition, all patients met the following criteria:

- Adequate Bone Marrow Function, including:
  - Absolute Neutrophil Count (ANC) ≥1,500/mm³(≥1.5×10⁹/L); Non Hodgkin lymphoma, only, ANC ≥1,000/mm³(≥1.0×10⁹/L);
  - Platelets ≥75,000/mm³(≥75×10⁹/L); Non Hodgkin lymphoma only: Platelets ≥50,000/mm³(≥250×10⁹/L);
  - Hemoglobin ≥9 g/dL (≥90 g/L); Non Hodgkin lymphoma only: Hemoglobin ≥8 g/dL (≥80 g/L).
- Adequate Renal Function, including:
  - Serum creatinine ≤1.5× upper limit of normal (ULN) or estimated creatinine clearance ≥60 mL/min as calculated using the method standard for the institution.
- Adequate Liver Function, including:
  - Total serum bilirubin ≤1.5×ULN (≤3.0×ULN if the patient had documented Gilbert syndrome);
  - Aspartate and Alanine transaminase (AST and ALT)≤3.0×ULN; ≤5.0×ULN if there was liver involvement secondary to tumor;
  - Alkaline phosphatase ≤2.5×ULN (≤5.0×ULN if bone or liver metastasis).
- QT interval corrected for heart rate Fridericia's (QTcF) interval of ≤480 msec (based upon mean value from triplicate ECGs).
- Age ≥18 years.
- Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) was 0 or 1.
- Resolved acute effects of any prior therapy to baseline severity or Grade ≤1 (NCI CTCAE v.4.03) except for AEs not constituting a safety risk by Investigator judgment.
- Available archival (or fresh) metastatic biopsy sample prior to study entry (expansion phase only).
- Serum pregnancy test (for females of childbearing potential) negative at screening.

Exclusion Criteria

Patients with any of the following characteristics were not included in this study:

- Patients with known symptomatic CNS metastases or leptomeningeal disease requiring steroids. Patients with previously diagnosed brain metastases were eligible if they completed their treatment and recovered from the acute effects of radiation therapy or surgery prior to study entry, discontinued corticosteroid treatment for these metastases and were clinically stable off anticonvulsants for at least 4 weeks and were neurologically stable before enrollment.
- Patients with ALK or EGFR genomic tumor aberrations (NSCLC, Part 2 expansion only), or any patient with a history of (non-infectious) pneumonitis that required steroids or had current pneumonitis.
- Patients with high grade lymphoma (including Burkitts lymphoma, lymphoblastic lymphoma, Richter's transformation), CLL or plasma cell leukemia
- Previous high-dose chemotherapy requiring allogeneic stem cell rescue.
- Prior irradiation to >25% of the bone marrow (non-lymphoma patients only), or any patient who received prior radiotherapy within 2 weeks of start of study treatment. Note: Participants must have recovered from all radiation-related toxicities, did not require corticosteroids, and not have had radiation pneumonitis. A 1-week washout was permitted for palliative radiation (≤2 weeks of radiotherapy) to non-CNS disease.
- Prior treatment with any anti-CD47 or anti-SIRPα agent.
- Systemic anti-cancer therapy within 4 weeks of starting study treatment (6 weeks for mitomycin C or nitrosoureas). If systemic anti-cancer therapy was given within 4 weeks, patient was included if 4-5 times elimination half-life of the drug had passed.
- Prior treatment with (Expansion phase only):
  - A PD-1 or PD-L1 inhibitor (NSCLC; HNSCC) for metastatic disease with disease progression within 8 weeks of initiation.
  - Trastuzumab (Gastric/GEJ Cancer) for metastatic disease with disease progression as the best response.
- Patients with intolerance to or who had a severe allergic or anaphylactic reaction to antibodies or infused therapeutic proteins, or patients who had a severe allergic or anaphylactic reaction to any of the substances included in the study drug (including excipients); or who discontinued treatment due to a Grade 3 or higher immune related AE from prior therapy with an anti-PD-1, anti-PD-L1, or anti PD-L2 agent or with an agent aiming to modulate another immune cell target (e.g., CTLA-1, OX40, 41BB, etc.).
- Any experimental antibodies or live vaccines in the last 28 days prior to the first dose of study drug. Live attenuated vaccines were not allowed.
- Current active therapy for the primary diagnosis.
- Blood product transfusions within 14 days of Cycle 1 Day 1.
- History of (or active) autoimmune disorders (including but not limited to: Crohn's Disease, rheumatoid arthritis, scleroderma, systemic lupus erythematosus, Grave's disease) and other conditions that compromise or impair the immune system (with the exception of hypogammaglobulinemia).
- History of autoimmune hemolytic anemia or autoimmune thrombocytopenia.
- Patients with active, uncontrolled, clinically significant bacterial, fungal, or viral infection, including hepatitis B (HBV), hepatitis C (HCV), known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS)-related illness.
- Patients with active graft versus host disease (GVHD) or ongoing immunosuppression for GVHD.
- Any of the following in the previous 12 months: myocardial infarction, severe/unstable angina, coronary/peripheral artery bypass graft, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, deep venous thrombosis, or symptomatic pulmonary embolism.
- Current active treatment in another interventional therapeutic clinical study.
- Diagnosis of any other malignancy within the last 3 years prior to enrollment except for adequately treated non-melanomatous skin cancer, or carcinoma in situ (e.g., breast carcinoma, cervical cancer in situ) that underwent potentially curative therapy.
- Other severe acute or chronic medical or psychiatric condition, including recent (within the past year) or active suicidal ideation or behavior, or laboratory abnormality that increased the risk associated with study participation or investigational product administration or interfered with the interpretation of study results and, in the judgment of the Investigator, made the patient inappropriate for entry into this study.
- Males and females of childbearing potential not using highly effective contraception or not having agreed to continue highly effective contraception for at least 90 days after last dose of investigational product.
- Patients who were pregnant or breastfeeding.

Study Treatment

As shown in FIG. 2, this study had three treatment arms (Drug A+pembrolizumab; Drug A+trastuzumab; Drug A+rituximab). The study included an initial dose escalation portion followed by a dose expansion portion. Each dose escalation group had approximately 12 advanced malignancy patients. Each expansion group had approximately 20-40 patients at multiple sites.

Drug A was administered weekly (or every 2 weeks) as an IV infusion over approximately 60 minutes on an outpatient basis. The use of an infusion pump was the preferred method of administration to ensure accurate delivery of the investigational product, but gravity drips were allowed.

Drug A was supplied in either a 100 mg/5 mL or 400 mg/20 mL Type 1 clear glass vial, sealed with a 20 mm Teflon coated rubber serum stopper and a tamper-evident aluminum seal. Each single use vial delivers 100 mg Drug A (5 mL) or 400 mg Drug A (20 mL) and is intended for intravenous (IV) administration.

A cycle was defined as the time from the Day 1 dose to the next Day 1 dose. If there were no treatment delays, a cycle was 21 days for the weekly dosing and 28 days for the dosing every 2 weeks.

All trial treatments were administered on an outpatient basis. Patients were observed in the clinic for at least 2 hours after infusion of Drug A on day 1 of cycle 1 (C1D1) and as clinically indicated thereafter.

No premedication for Drug A was required. Guidelines in the pembrolizumab, trastuzumab and rituximab combination therapy package inserts were followed.

In the dose escalation and expansion phases, the combination partner therapy was administered according to its label instructions:

- Trastuzumab: Initial dose of 8 mg/kg administered as an intravenous infusion over 90 minutes, followed by 6 mg/kg intravenous infusion (IV) administered over 30 to 90 minutes every 3 weeks.
- Pembrolizumab: 200 mg IV administered as an intravenous infusion over 30 minutes every 3 weeks for up to 24 months.
- Rityximab: 375 mg/m²administered as an intravenous infusion once weekly for 4 doses followed by once monthly for 8 doses (initiated at a rate of 50 mg/hr and increased by 50 mg/hr increments every 30 minutes, to a maximum of 400 mg/hr in the absence of infusion toxicity). If the first infusion of rituximab was tolerated, subsequent infusions were started at a rate of 100 mg/hr and increased by 100 mg/hr increments at 30-minute intervals, to a maximum of 400 mg/hr in the absence of toxicity.

On administration days when dosing schedules coincided, the combination partner commenced approximately 30 minutes after Drug A therapy finished. On such days, in the event of a missed dose of the Drug A drug due to toxicity, the partner drug was administered 24 hours after the missed dose. In the event the Drug A was permanently discontinued, the patient was discontinued from the treatment phase of the study. In the event that the partner drug was permanently discontinued, the patient continued single agent Drug A for up to 24 months if in the investigator's opinion, the patient was deriving clinical benefit from Drug A.

Dose Escalation Component

For Drug A, the initial dose escalation component began one dose level below the single agent maximum tolerated dose (MTD) or maximum administered dose (MAD) (3-6 patients in each dose level) taking into account the observed Drug A single agent dose limiting toxicity (DLT) profile and known safety profile of the proposed combination agent (Table A). If the Drug A dose was safe and well tolerated in combination, then the dose level of Drug A was increased to the MTD or MAD with the combination agent.

No MTD for Drug A as a single agent has been reached. The MAD for Drug A as a single agent was 30 mg/kg administered IV every other week (QOW or Q2W)

TABLE A

Dose escalation for Drug A.

Route of

Cohort
Dosage mg/kg
Administration
Frequency of Dosing

1
0.3
IV
Once a week

2
1.0
IV
Once a week

3
3.0
IV
Once a week

4
10.0
IV
Once a week

5
30.0
IV
Once every 2 weeks

Expansion Phase

Drug A was administered once per week (QW) at a dose of 10 mg/kg as an intravenous (IV) infusion over approximately 60 minutes on an outpatient basis.

In the expansion phase, the combination partner therapy was administered according to its label instructions, as described above.

The Drug A+pembrolizumab expansion group included up to 20 patients with metastatic NSCLC and up to 20 patients with recurrent or metastatic head and neck squamous cell carcinoma.

The Drug A+trastuzumab expansion group included up to 20 patients with HER2-overexpressing (HER2 positive) gastric carcinoma.

The Drug A+rituximab expansion group included approximately 10 patients with relapsed or refractory, diffuse large B cell lymphoma, and approximately 10 patients with indolent lymphoma.

Each patient received Drug A until disease progression, unacceptable toxicity, withdrawal of consent, or study termination. Patients received study therapy on study after radiographic progression if, in the estimation of the Investigator, the patient was deriving clinical benefit from the study treatment.

Efficacy Analyse

Overall response rate (ORR), disease control rate (DCR), duration of response (DoR), progression free survival (PFS), and overall survival (OS) were analyzed in the ITT population and Evaluable Population.

The objective tumor response was evaluated using the using the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 for solid tumors. Tumor assessments included all known or suspected disease sites. Imaging included chest, abdomen and pelvis CT or MRI scans; brain CT or MRI scan for patients with known or suspected brain metastases; bone scan and/or bone x-rays for patients with known or suspected bone metastases. In addition, for lymphoma patients, tests included PET scans and bone marrow evaluation. The same imaging technique used to characterize each identified and reported lesion at baseline was employed in the following tumor assessments.

Antitumor activity was assessed through radiological tumor assessments conducted at baseline, during treatment, whenever disease progression was suspected (e.g., symptomatic deterioration), and at the time of withdrawal from the study (if not done in the previous 6 weeks).

Assessment of response was made using RECIST version 1.1 or, where relevant, the Lugano Criteria (Cheson et al., J. Clin. Oncol (2014) 32:27: 3059-3068).

Changes in tumor size were categorized as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD), the latter incorporating the appearance of new lesions. In the expansion cohorts, a secondary analysis was carried out using the Immune-Related RECIST 1.1. To facilitate this secondary analysis, in expansion cohorts, only, the diameters (longest for non-nodal lesions, shortest for nodal lesions) of all target and new measurable lesions were collected. Additionally, in the expansion cohorts, confirmation of both progression and response by imaging at least 4 weeks from the date first documented was required.

PK/PD and Biomarker Analyses

Drug concentrations of Drug A were measured using validated methods. Drug A serum concentrations were analyzed using a validated ligand binding ELISA. PK parameters were determined from the respective concentration-time data using standard noncompartmental methods. Actual sample collection times were used for the parameter calculations. For Drug A, PK parameters including maximum concentration (C_max), time to maximum concentration (T_max), area under the concentration-time curve (AUC_last, AUC_inf, and/or AUC_τ) were calculated. As appropriate, additional PK parameters including clearance (CL), volume of distribution (Vz), terminal elimination half-life (t_1/2), and accumulation ratio (R_ac) were calculated.

PK/PD analyses were conducted to explore the exposure-response relationship using appropriate model-based methods to assist OBD determination. Pharmacodynamic data (receptor occupancy and immunophenotyping) were summarized graphically and with descriptive statistics by time and dose.

PK/PD analysis using appropriate model-based methods were explored to better understand the exposure-response relationship. Pre- and post-dose levels of CD47 target occupancy were analyzed and immunophenotyping of circulating leukocyte population was performed. CD47 target occupancy in peripheral blood T lymphocytes and erythrocytes was measured by flow cytometry. Infiltrating leukocyte populations and immune-modulatory molecules in tumor biopsy tissue before and after treatment, and specific cytokines and chemokines in serum before and after treatment were analyzed. Exploratory molecular analysis (including but not limited to additional immune markers) in peripheral blood and tumor biopsy samples was performed before and after treatment.

CD8, CD68, CD163, and PD-L1 on tumor tissue were measured by immunohistochemistry (IHC) assays. Percent positive values for CD8, CD68, and CD163 were obtained by image analysis. PD-L1 (Clone 22C3) tumor proportion score (TPS) and combined positive score (CPS) were obtained by pathologist review. HER2 levels were determined using HERCEPTES™. RNA expression from paired tumor biopsies were assessed using NANOSTRING IO360™ expression panel. Cell type abundance and pathway profiling analyses using pre-defined gene signatures were performed using NANOSTRING nSOLVER™ analysis software.

Blood samples were collected at the Baseline visit and retained for pharmacogenomic analyses related to drug response. For example, SIRPα gene polymorphisms, putative safety biomarkers, drug metabolizing enzyme genes, drug transport protein genes, or genes thought to be related to the mechanism of drug action are examined.

Results

Patient Characteristics

Eighty-two patients with advanced solid tumor malignancies were enrolled in this study. The patient baseline characteristics are provided in Table B.

TABLE B

Patient baseline characteristics

Trastuzumab
Pembrolizumab

n = 30
N = 52

Primary
Gastric/GEJ/Esophageal
25
—

Disease, n
HNSCC
—
20

NSCLC
—
26

Breast
2
—

Colorectal
—
2

Ovarian
1
2

Pancreatic
1
—

Peritoneal
—
1

Appendiceal
—
1

Urothelial
1
—

Median age, years (range)
58 (45-79)
61 (32-81)

Sex, n
F
9
23

M
21
29

Race, n
White
13
34

Asian
14
11

Other
3
7

ECOG PS, n
0
8
16

1
22
36

Safety

Drug A in combination with trastuzumab or pembrolizumab was well tolerated, and most treatment-related adverse events (TRAE) were of low grade and frequency. Treatment-related adverse events occurring in two or more patients are provided in Table C for the Drug A+trastuzumab combination, and in Table D for the Drug A+pembrolizumab combination. The most frequent TRAE in the Drug A+trastuzumab combination was fatigue (26.7%/). The most frequent TRAE the Drug A+pembrolizumnab combination was AST increased (15.4%).

TABLE C

Treatment-related adverse events that occurred in two or more

patients treated with the Drug A + trastuzumab combination.

Treatment Related Adverse Events

Drug A + Trastuzumab (N = 30)

Adverse Event
Total n (%)
≥Grade 3

Fatigue
8 (26.7)

Platelets decreased
4 (13.3)
2 (6.7)

Decreased appetite
3 (10)

Pyrexia
3 (10)

Anemia
2 (6.7)

Nausea
2 (6.7)

Neutropenia
2 (6.7)
2 (6.7)

TABLE D

Treatment-related adverse events that occurred in two or

more patients treated with the Drug A + pembrolizumab combination.

Treatment Related Adverse Events

Drug A + Pembrolizumab (N = 52)

Adverse Event
Total n (%)
≥Grade 3

AST Increased
8 (15.4)

ALT Increased
7 (13.5)
1 (1.9)

Fatigue
6 (11.5)

Pruritus
5 (9.6)

Anemia
4 (7.7)
1 (1.9)

Infusion reaction
4 (7.7)

Platelets decreased
4 (7.7)
2 (3.8)

Alkaline phosphatase
3 (5.7)

increased

Arthralgia
3 (5.8)

Pyrexia
3 (5.8)

WBC decreased
3 (5.8)

Decreased appetite
2 (3.8)

Myalgia
2 (3.8)

Nausea
2 (3.8)

Neutropenia
2 (3.8)
1 (1.9)

Rash
2 (3.8)

TRAEs of Grade 3 severity were of low frequency. In the Drug A+trastuzumab combination, one treatment-related serious adverse event of febrile neutropenia was reported. In the Drug A+pembrolizumab combination, three treatment-related serious adverse events were reported: one autoimmune hemolytic anemia, one febrile neutropenia, and one neutropenia.

Efficacy

Dose Escalation

The dose escalation component had a total of 22 patients. In the Drug A+trastuzumab combination cohort (n=10), of the 8 evaluable patients, 3 exhibited stable disease (SD) (2 patients had breast cancer, 1 patient had GEJ). In the Drug A+pembrolizumab combination cohort (n=12), of the 10 evaluable patients, 1 exhibited a partial response (PR) (NSCLC that was CPI refractory) and 3 exhibited stable disease (1 patient had appendiceal cancer, 2 patients had NSCLC).

Dose Expansion

The dose expansion phase had a total of 60 patients.

Drug A+trastuzumab combination cohort with HER2 positive gastric/GEJ cancer (n=20): Of the 18 evaluable patients, 4 exhibited partial response (confirmed) and 5 exhibited stable disease. FIG. 3A provides the percent change of disease assessment from baseline. The ORR was 22%, the DCR was 28% and the mPFS was 2.2 months. FIG. 3B provides the percent change of disease assessment from baseline for each patient over the study period. FIG. 3C provides the duration of treatment for enrolled patients in this cohort. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

Drug A+pembrolizumab combination cohort with HNSCC (n=20): Of the 19 evaluable patients, 3 exhibited a partial response (2 confirmed, 1 unconfirmed), and 6 exhibited stable disease. FIG. 4A provides the percent change of disease assessment from baseline. The ORR was 16% for all patients, and 30% for checkpoint therapy naïve patients; the DCR was 26% for all patients, and 30% for checkpoint therapy naïve patients; and the mPFS was 2.1 months for all patients. In addition, the combined positive score (CPS) for PD-L1 staining is reported for each patient. FIG. 4B provides the percent change of disease assessment from baseline for each patient over the study period. FIG. 4C provides the duration of treatment for enrolled patients in this cohort. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

Drug A+pembrolizumab combination cohort with NSCLC (n=20): Of the 18 evaluable patients, 8 exhibited stable disease. FIG. 5A provides the percent change of disease assessment from baseline. The disease control rate (DCR) was 17% and the mPFS was 2 months. In addition, the tumor proportion score (TPS) for PD-L1 staining is reported for each patient. FIG. 5B provides the percent change of disease assessment from baseline for each patient over the study period. FIG. 5C provides the duration of treatment for enrolled patients in this cohort. Tumors were assessed according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247.)

Pharmacokinetics

Drug A PK observations from combination cohorts Drug A+trastuzumab and Drug A+pembrolizumab were within predicted 95% intervals based on an established population PK model (Jin F. et al., (2018) Soc Immunotherpay of Cancer Conference, #P340) (FIG. 6A). The steady-state half-life of Drug A (10 mg/kg QW) was predicted to be approximately 16 days. As shown in FIG. 6B, near complete CD47 target occupancy on CD4+ T cells that express CD47 was maintained throughout the Drug A dosing interval in both combinations cohorts.

Anti-Tumor Response

As shown in FIG. 7A, paired biopsies from 5 NSCLC patients treated with Drug A+pembrolizumab, 6 HNSCC patients treated with Drug A+pembrolizumab, and 1 gastric cancer patient treated with Drug A+trastuzumab revealed an increase in tumor-associated macrophages and infiltrating lymphocytes after treatment. Images from individual patients showing staining for CD68 and CD8 before and during treatment are provided in FIG. 7B (NSCLC PD-L1(−) patient treated with Drug A+pembrolizumab) and FIG. 7C (HNSCC PD-L1(+) patient treated with Drug A+pembrolizumab). CD68 and CD163 markers indicate macrophages; the CD8 marker indicates T lymphocytes.

Conclusions

Drug A in combination with pembrolizumab or trastuzumab demonstrates excellent tolerability with favorable PK/PD characteristics. Objective responses were observed in patients with late line NSCLC, HNSCC, and Gastric/GEJ, including disease relapsed/refractory to prior CPI and HER2-targeted therapies.

Drug A (10 mg/kg QW; molar equivalent to 20 mg/kg of an antibody) in combination with standard regimens of trastuzumab or pembrolizumab was well tolerated with a favorable hematologic safety profile.

Drug A demonstrates anti-cancer activity in combination with trastuzumab in HER2 positive patients that have progressed on prior HER2 targeted therapies (e.g., HER2-positive Gastric/GEJ tumors that have progressed on prior HER2 targeted therapies).

Drug A demonstrates anti-cancer activity in combination with pembrolizumab in patients with:

- ≥2 L HNSCC that compares favorably to the pembrolizumab single agent experience.
- NSCLC, including tumors resistant/refractory to prior checkpoint inhibitor therapy.

Drug A demonstrates antibody-like PK and complete CD47 target occupancy in combination with trastuzumab or pembrolizumab.

Preliminary data from paired tumor biopsies suggests increased intra-tumoral macrophages and CD8+ T cells following Drug A treatment.

Taken together, the data presented in this Example demonstrate the efficacy and safety of Drug A administered in combination with pembrolizumab, trastuzumab or rituximab, in patients with advanced malignancies including non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), HER2-overexpressing gastric cancer, and non-Hodgkin lymphoma (NHL). Without wishing to be bound by theory, as shown in FIG. 8, it is believed that Drug A, when administered in combination with anti-cancer therapeutic antibodies such as pembrolizumab, trastuzumab or rituximab, maximizes the innate and adaptive immune response to cancer. In particular, it is believed that Drug A: 1) Enhances macrophage phagocytosis of cancer cells by blocking CD47; 2) Increases the ratio of inflammatory M1 tumor-associated macrophages (TAMs) to suppressive M2 TAMs; and 3) Activates dendritic cells (DCs) and enhances cross-priming of T cells. Furthermore, it is believed that Drug A in combination with anti-cancer antibodies avoids dose-limiting toxicities associated with other CD47-target approaches while maximizing the innate and adaptive immune response.

Example 2A: Further Safety Results from a Phase 1 Study of Drug A in Combination with Pembrolizumab or Trastuzumab

As described in Example 1, 52 patients with solid tumor received Drug A in combination with pembrolizumab, and 30 patients with solid tumor received Drug A in combination with trastuzumab. Treatment-related adverse effects (TRAEs) (including fatigue, AST increase, platelet decrease, ALT increase, anemia, and/or pruritus) were of low grade and low frequency.

35 (67.3%) of patients who received Drug A+pembrolizumab and 22 (73.3%) of patients who received Drug A+trastuzumab experienced any TRAE. The most frequent TRAE experienced by patients who received Drug A+pembrolizumab was low-grade aspartate transaminase (AST) increase (17.3%), and the most frequent TRAE experienced by patients who received Drug A+trastuzumab was low grade fatigue (30%). TRAEs of ≥Grade 3 severity were of low frequency. See Tables E and F below.

TABLE E

TRAE in Patients Receiving Drug A + Trastuzumab

Adverse Event
Total N (%)
≥Grade 3

Fatigue
9 (30)
—

PLATELETS DECREASED
5 (16.7)
2 (6.7)

Decreased Appetite
3 (10)
—

PRURITUS
3 (10)
—

Pyrexia
3 (10)
—

Anemia
2 (6.7)
—

Nausea
2 (6.7)
—

Neutropenia
2 (6.7)
2 (6.7)

TABLE F

TRAE in Patients Receiving Drug A + Pembrolizumab

Adverse Event
Total N (%)
≥Grade 3

AST Increased
9 (17.3)
—

ALT Increased
7 (13.5)
1 (1.9)

Fatigue
6 (11.5)
—

Anemia
5 (9.6)
1 (1.9)

Pruritus
5 (9.6)
—

RASH
5 (9.6)
—

Infusion Reaction
4 (7.7)
—

PLATELETS DECREASED
4 (7.7)
2 (3.8)

Alkaline Phosphatase Increased
3 (5.8)
—

Arthralgia
3 (5.8)
—

Pyrexia
3 (5.8)
—

WBC Decreased
3 (5.8)
—

Decreased Appetite
2 (3.8)
—

Myalgia
2 (3.8)
—

Nausea
2 (3.8)
—

Neutropenia
2 (3.8)
1 (1.9)

- For Tables E and F, RASH: rash, rash papulo-macular, rash vesicular, rash pruritic dermatitis; PLATELETS DECREASED: platelets decrease, thrombocytopenia; PRURITUS: pruritus, pruritus generalized.

Four treatment-related serious adverse events (TRSAEs) were reported in patients receiving Drug A+pembrolizumab: 1 patient experienced autoimmune hemolytic anemia/pancytopenia; 1 patient experienced febrile neutropenia; 1 patient experienced neutropenia; and 1 patient experienced peripheral neuropathy. One TRSAE was reported in patients receiving Drug A+trastuzumab. The patient experienced febrile neutropenia.

Drug A displays a favorable exposure-safety relationship across the exposure ranges administered in the clinic (i.e., 10 mg/kg qw-30 mg/kg qow) with no exposure-dependent cytopenias observed.

Example 2B: Further Results from a Phase 1 Study of Drug A in Combination with Pembrolizumnab in Patients with ≥2 L Head and Neck Squamous Ceil Carcinoma

As described in Example 1, 20 patients with ≥2M HNSCC received Drug A in combination with pembrolizumnab. Baseline characteristics of all patients receiving Drug A+pembrolizumab (including patients with ≥2 L NSCLC, as described in further detail in Example 2C below) are shown in Table G.

TABLE G

Baseline Characteristic of All Patients*

Receiving Drug A + Pembrolizumab

Drug A + Pembrolizumab

N = 52

Primary Disease, n

Lung
25

HNSCC
20

Gastric/GEJ Esophageal
—

Breast
—

Colorectal
2

Ovarian
2

Pancreatic
—

Appendiceal
1

Sarcoma
1

Urothelial
—

Unknown
1

Median Age

Years (range)
61 (32-81)

Sex, n

M
29

F
23

Race, n

White
34

Asian
11

Black
3

Other
4

ECOG PS, n

0
18

1
34

*patients included those with ≥2 L HNSCC and ≥2 L NSCLC (see Example 2C).

Anticancer efficacy in HNSCC patients was observed in response-evaluable patients. Clinical activity was based on investigator assessed response using RECIST 1.1 criteria (E. A. Eisenhauer, et al., European Journal of Cancer 45 (2009) 228-247). Among the 10 patients who were checkpoint inhibitor-naïve (i.e., who had not received prior treatment with an immune checkpoint inhibitor), the overall response rate (ORR) was 40% (95% CI:12.2, 73.8); the median PFS (mPFS) was 4.61 months (95% CI:0.53; 7.53), and the median overall survival (mOS) had not been reached with a 14.4 month median follow-up or a 17.9 month follow-up. The disease control rate (DCR) was 50% (95% CI: 18.7: 81.3): 4/10 of the checkpoint-inhibitor naïve patients achieved partial response (“PR”) (2 confirmed); 2/10 achieved stable disease (“SD”); and 4 demonstrated progressive disease (“PD”). The duration of response (DOR) was 4.31 months. Among the 10 patients who were checkpoint inhibitor-experienced (i.e., who had received prior treatment with an immune checkpoint inhibitor), the ORR was 0%; the mPFS was 2.0 months [95% CI:0.9; 3.6], and the mOS as 7.4 months (95% CI: 3.1; NC). 3 patients in the checkpoint inhibitor-experienced subgroup achieved SD, and 7 demonstrated PD. See FIG. 9A, which shows the clinical activity of the Drug A+pembrolizumab combination in response-evaluable patients, and FIG. 9B, which shows the best overall response and duration of response in ≥2 L HNSCC patients treated with Drug A and pembrolizumab. Additional details regarding ORR, DCR, DOR, mPFS, and mOS for all patients (i.e., both checkpoint inhibitor experienced and checkpoint inhibitor naïve) are provided in FIG. 9A.

Full peripheral CD47 target occupancy and increased infiltrating immune cells in tumor biopsies were seen. These data confirm clinical activity of the Drug A+pembrolizumab combination treatment in patients with advanced checkpoint inhibitor-naïve HNSCC (including PD-L1 negative patients). The clinical activity compares favorably with historic controls, namely, the pembrolizumab single-agent experience. Preliminary biomarker analyses suggested that baseline levels of CD47 and SIRPα gene expression and tumor-infiltrating CD8⁺ cells CD68⁺ cells, and CD163⁺ cells are not associated with tumor response as measured by % change of target lesion size from baseline.

Example 2C: Further Results from a Phase 1 Study of Drug A in Combination with Pembrolizumab in Patients with ≥2 L NSCLC Who Progressed on Prior Checkpoint Inhibitor Therapy

As described in Example 1, 20 patients with ≥2 L NSCLC received Drug A in combination with pembrolizumab. 17 had progressed on prior checkpoint inhibitor therapy, and 3 of the patients were checkpoint-inhibitor naïve.) Baseline characteristics of all patients receiving Drug A+pembrolizumab (including those being treated for HNSCC) are shown in Table G above. Clinical activity in NSCLC patients was based on investigator assessed response using RECIST 1.1 criteria. The overall response rate (ORR) was 5% (95% CI: 0.1, 24.9), with 1 patient achieving partial response (PR), 9 patients achieving stable disease (SD), and 10 patients demonstrating progressive disease (PD). The patient who achieved PR initially exhibited progressive disease, followed by stable disease and subsequent partial response. The patient who achieved PR had a tumor proportion score of 0%. The disease control rate (DCR) was 35% (95% CI:15.4, 59.2). The median progression-free survival was 2.01 months (95% CI: 1.88, 5.56), and the median overall survival was 9.11 months (95% CI: 7.17, NC). See FIG. 10A, which shows the clinical activity of the Drug A+pembrolizumab combination in response-evaluable ≥2 L NSCLC patients, and FIG. 10B, which shows the best overall response and duration of response in ≥2 L NSCLC patients treated with Drug A and pembrolizumab.

These data confirm clinical activity of the Drug A+pembrolizumab combination treatment in patients with ≥2 L NSCLC, including those who are resistant/refractory to prior checkpoint inhibitor therapy. Preliminary biomarker analyses suggested that baseline levels of CD47 and SIRPα gene expression and tumor-infiltrating CD8⁺ cells CD68⁺ cells, and CD163⁺ cells are not associated with tumor response as measured by % change of target lesion size from baseline.

Example 2D: Further Results from a Phase 1 Study of Drug A in Combination with Trastuzumab in Patients with ≥2 L HER2-Positive Gastric/GEJ Cancer

As described in Example 1, 25 patients with ≥2 L HER2⁺ gastric cancer or HER2⁺ gastroesophageal cancer received Drug A in combination with trastuzumab. Baseline characteristics of all patients receiving Drug A+trastuzumab are shown in Table H below:

TABLE H

Baseline Characteristics

Drug A + Trastuzumab

N = 30

Primary Disease, n

Lung
—

HNSCC
—

Gastric/GEJ Esophageal
25

Breast
2

Colorectal
—

Ovarian
1

Pancreatic
1

Appendiceal
—

Sarcoma
—

Urothelial
1

Unknown
—

Median Age

Years (range)
60 (45-79)

Sex, n

M
21

F
9

Race, n

White
13

Asian
14

Black
1

Other
2

ECOG PS, n

0
11

1
19

Clinical activity in patients with gastric cancer/GEJ cancer was based on investigator assessed response using RECIST 1.1 criteria. Anticancer efficacy was observed in response-evaluable patients. The ORR was 21.1% (95% CI: 6.1, 45.6), the mPFS was 2.2 months (95% CI: 1.9; 5.4), the mOS was 11.5 months (95% CI: 3.36; 14.0). Among the 19 response-evaluable patients, 4 achieved partial response (3 confirmed); 5 achieved stable disease; and 10 demonstrated progressive disease. The disease control rate (DCR) was 26.3% (95% CI: 9.1, 51.2), and the duration of response was 9.38 months. See FIG. 11A, which shows the clinical activity of the Drug A+trastuzumab combination in response-evaluable ≥2 L HER2⁺ gastric cancer or ≥2 L HER2⁺ GEJ cancer patients, and FIG. 9B, which shows the best overall response and duration of response in ≥2 L HER2⁺ gastric cancer or ≥2 L HER2⁺ GEJ cancer patients treated with Drug A and trastuzumab.

Full peripheral CD47 target occupancy and increased infiltrating immune cells in tumor biopsies were seen. These data confirm clinical activity of the Drug A+trastuzumab combination treatment in patients with HER2⁺ gastric or gastroesophageal cancer that have progressed on prior HER2-targeted therapies. The clinical activity compares favorably with historic controls. Preliminary biomarker analyses suggested that baseline levels of CD47 and SIRPα gene expression and tumor-infiltrating CD8⁺ cells CD68⁺ cells, and CD163⁺ cells are not associated with tumor response as measured by % change of target lesion size from baseline.

Example 2E: Further Results from a Phase 1 Study of Drug A in Combination with Rituximab in Patients with Non-Hodgkin Lymphoma

This example provides further results from the clinical study of Drug A's safety profile and antitumor activity in combination with rituximab with both aggressive and indolent histologies of non-Hodgkin Lymphoma (NHL), as described in Example 1.

Patients enrolled in the study were ≥18 years of age and had relapsed or refractory CD20-positive B-cell NHL for which no curative therapy was available or were relapsed or refractory to standard approved therapies. Patients were required to have adequate organ function and hemoglobin ≥28 g/dL; absolute neutrophil count ≥1,000/mm³, and platelets ≥50,000/mm³. Patients who had received prior treatment with any anti-CD47 or anti-SIRPα agent were excluded.

Patients received Drug A (10 mg/kg QW or 15 mg/kg QW) in combination with rituximab (375 mg/m²weekly for 4 doses followed by once monthly for 8 doses). The primary endpoint for the safety confirmation population was first cycle dose limiting toxicity (DLT). Tumor response (using Lugano Working Group 2014 response criteria in NHL), adverse events (characterized using NCI CTCAE v 4.03), pharmacokinetic (PK), and pharmacodynamic (PD) markers were assessed in all patients.

33 NHL patients (23 male, 10 female; median prior lines of therapy=3) were administered with Drug A in combination with rituximab. 22 patients (11 with diffuse large B-cell lymphoma (DLBCL); 4 with mantle cell lymphoma (MCL); 5 with follicular lymphoma (FL); and 2 with marginal zone lymphoma (MZL)) were given Drug A 10 mg/kg QW+rituximab, and 11 patients (6 with DLBCL; 1 with MCL; 3 with FL; and 1 with MZL) were given Drug A 15 mg/kg QW+rituximab. The baseline characteristics of the patients are shown in Table I, and patient drug exposure and disposition are shown in Table J.

TABLE I

Baseline Characteristics of Patients Receiving

Drug A + Rituximab for NHL

Drug A (10 mg/kg
Drug A (15 mg/kg

QW) + Rituximab
QW) + Rituximab

(N = 22)
(N = 11)

Primary Disease, n

Follicular
5
3

Marginal Zone
2
1

DLBCL
11
6

Mantle Cell
4
1

Median Age

Years (range)
66 (32-80)
64 (53-78)

Sex, n

M
17
6

F
5
5

Race, n

Asian
18
9

White
4
2

ECOG PS, n

0
7
2

1
15
8

TABLE J

Patient Drug Exposure and Disposition

Drug A + Rituximab

Drug A 10 mg/kg
Drug A 15 mg/kg

(N = 22)
(N = 11)

Dose Reductions, n
0
0

Discontinuation Due to TRAE
1{circumflex over ( )}
0

Discontinuation Due to PD
12
4

Discontinuation Due to Death
2*
0

Discontinuation Due to Other
1
1

Ongoing Treatment
6
6

{circumflex over ( )}Discontinuation due to rituximab infusion reaction;

*Death due to disease progression.

No patient required a dose reduction, and the most common reason for discontinuation of treatment was disease progression.

Drug A in combination with rituximab was well tolerated, and most treatment related adverse events (TRAEs) were of low grade and low frequency. Twenty-six (78.8%) patients experienced any adverse event. Fifteen (45.5%) patients experienced any TRAE. The most common TRAE of Drug A in combination with rituximab was Grade 1-2 rash (18%), fatigue (9% n=3), anemia (6%, n=2), nausea (6%, n=2), and neutropenia (6%, n=2). TRAEs ≥Grade 3 severity were of low frequency (see Table K). No treatment related serious adverse events were reported. There were 2 deaths on study, both due to disease progression.

TABLE K

Treatment-Related Adverse Events

Adverse Event
Total N (%)
≥Grade 3

Rash
6 (18%)
—

Fatigue
3 (9%)
—

Nausea
2 (6%)
—

Neutrophil Count Decreased
2 (6%)
2 (6%)

Anemia
2 (6%)
1 (3%)

No Drug A dose limiting toxicities were reported. The maximum tolerated dose (MTD) of Drug A in combination with rituximab was not reached. The maximum administered dose of Drug A (i.e., administered in combination with rituximab) was 15 mg/kg QW. No significant exposure-cytopenia relationship was observed across the Drug A exposure range evaluated (10 mg/kg QW-15 mg/kg QW).

Anti-tumor activity was observed across all histologies in response-evaluable patients with relapsed/refractory aggressive histologies (i.e., DLBCL and MCL) and relapsed/refractory indolent histologies (i.e., FL and MZL). Responses were evaluated according to Lugano 2014 response criteria (see Cheson et al. (2014) “Recommendations for Initial Evaluation, Staging and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification.” J. Clin Oncol. 32: 3059-3067). As shown in Table L and FIG. 12, the overall response rate (ORR) among patients treated with 10 mg/kg QW Drug A+rituximab was 40.9%. 3 Patients (i.e., one with Mantle Cell Lymphoma (MCL), one with Follicular Lymphoma (FL), and one with MZL) achieved complete response (CR), 6 patients (two with Diffuse Large B-Cell Lymphoma (DLBCL), two with MCL, and two with FL) achieved partial response (PR). 6 patients (two with DLBCL, one with MCL, two with FL, and one with MZL) demonstrated stable disease (SD). The ORR among patients treated with 15 mg/kg QW Drug A+rituximab was 54.6% ORR. 2 patients (both with FL) achieved CR 4 patients (one with MZL, two with DLBCL, and one with MCL) achieved PR. 1 patient (with FL) demonstrated SD. See Table L below and FIG. 12. Further details regarding the duration of treatment for patients administered with 10 mg/kg Drug A+rituximab are provided in FIG. 13A, and further details regarding the duration of treatment for patients administered with 15 mg/kg Drug A+rituximab are provide in FIG. 13B.

TABLE L

Drug A + Rituximab Combination-Clinical Activity in Response-Evaluable Patients

Median
Median
Median
Median

Population

ORR
DOR
PFS
OS
Follow-Up

Drug A Dose
N
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)

NHL (10 mg/
22
40.9%
NC
7.4
NC
11.3

kg ALL)

(23.3; 61.3)

(1.9; 13.2)

(10.2; 15.2)

NHL (10 mg/
15
33.3%
5.6
2.5
8.9
10.4

kg aggressive)

(15.2; 58.3)
(1.8; NC)
(1.0; 7.4)
(2.5; NC)
(9.5; 15.2)

NHL (10 mg/
7
57.1%
NC
NC
NC
11.3

kg indolent)

(25.1; 84.2)

(7.8; 20.4)

NHL (15 mg/
11
54.6%
NC
NC
NC
5.1

kg ALL)

(28.0; 78.7)

(4.0; 5.6)

NHL (15 mg/
7
42.9%
NC
1.9
NC
4.7

kg aggressive)

(15.8; 75.0)

(1.1; NC)

(4.0; 5.4)

NHL (15 mg/
4
75%
NC
NC
NC
5.9

kg indolent)

(30.1; 95.4)

(3.5; 7.4)

Aggressive = relapsed refractory DLBCL or relapsed refractory mantle cell lymphoma;

Indolent = relapsed refractory follicular lymphoma or relapsed refractory marginal zone lymphoma;

ORR = objective response rate (complete response + partial response);

mDOR = median duration of response (months);

mPFS = median progression free survival (months);

mFollow-Up = median follow up (months);

NC = could not be calculated.

Across the exposure range evaluated (10 mg/kg QW-15 mg/kg QW), increased Drug A exposure was observed in subjects with a best response of CR and PR compared to subjects with a best response of SD and PD. Favorable Drug A pharmacokinetics and CD47 receptor occupancy were seen across the dosing interval.

Drug A in combination with standard regimens of rituximab was well tolerated with a favorable hematologic safety profile and no maximum tolerated dose reached. The maximum administered dose was 15 mg/kg QW (molar equivalent to 30 mg/kg QW of an antibody) with no exposure dependent anemia, thrombocytopenia or neutropenia observed across the exposure range evaluated. Drug A demonstrates emerging anti-cancer activity with durable responses in combination with rituximab in patients with relapsed/refractory NHL whose tumors have progressed on prior CD20 targeted therapies that compares favorably to historic controls. Preliminary data suggests Drug A is well tolerated and that higher exposure of Drug A is observed in responders vs non-responders.

Each embodiment herein described may be combined with any other embodiment or embodiments unless clearly indicated to the contrary. In particular, any feature or embodiment indicated as being preferred or advantageous may be combined with any other feature or features or embodiment or embodiments indicated as being preferred or advantageous, unless clearly indicated to the contrary.

All references cited in this application are expressly incorporated by reference herein.

	Number	Date	Country
	63022187	May 2020	US
	62855821	May 2019	US

	Number	Date	Country
Parent	16886559	May 2020	US
Child	17692006		US

	Number	Date	Country
Parent	17692006	Mar 2022	US
Child	18452972		US

METHODS OF TREATING CANCER

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