Patent Application
20220118108
Adeno-associated virus (AAV), a member of the Parvovirus family, is a small non-enveloped, icosahedral virus with single-stranded linear DNA (ssDNA) genomes of about 4.7 kilobases (kb) long. The wild-type genome comprises inverted terminal repeats (ITRs) at both ends of the DNA strand, and two open reading frames (ORFs): rep and cap. Rep is composed of four overlapping genes encoding rep proteins required for the AAV life cycle, and cap contains overlapping nucleotide sequences of capsid proteins: VP1, VP2 and VP3, which self-assemble to form a capsid of an icosahedral symmetry.
Recombinant adeno-associated virus (rAAV) vectors derived from the replication defective human parvovirus have been described as suitable vehicles for gene delivery. Typically, functional rep genes and the cap gene are removed from the vector, resulting in a replication-incompetent vector. These functions are provided during the vector production system but absent in the final vector.
To date, there have been several different well-characterized AAVs isolated from human or non-human primates (NHP). It has been found that AAVs of different serotypes exhibit different transfection efficiencies, and exhibit tropism for different cells or tissues. Many different AAV clades have been described in WO 2005/033321, including clade F which is identified therein as having just three members, AAV9, AAVhu31 and AAVhu32. A structural analysis of AAV9 is provided in M. A. DiMattia et al, J. Virol. (June 2012) vol. 86 no. 12 6947-6958. This paper reports that AAV9 has 60 copies (in total) of the three variable proteins (vps) that are encoded by the cap gene and have overlapping sequences. These include VP1 (87 kDa), VP2 (73 kDa), and VP3 (62 kDa), which are present in a predicted ratio of 1:1:10, respectively. The entire sequence of VP3 is within VP2, and all of VP2 is within VP1. VP1 has a unique N-terminal domain. The refined coordinates and structure factors are available under accession no. 3UX1 from the RCSB PDB database.
Several different AAV9 variants have been engineered in order to detarget or target different tissue. See, e.g., N. Pulicheria, “Engineering Liver-detargeted AAV9 Vectors for Cardiac and Musculoskeletal Gene Transfer”, Molecular Therapy, Vol, 19, no. 6, p. 1070-1078 (June 2011). The development of AAV9 variants to deliver gene across the blood-brain barrier has also been reported. See, e.g., B. E. Deverman et al, Nature Biotech, Vol. 34, No. 2, p 204-211 (published online 1 Feb. 2016) and Caltech press release, A. Wetherston, www.neurology-central.com/2016/02/10/successful-delivery-of-genes-through-the-blood-brain-barrier/, accessed Oct. 5, 2016. See, also, WO 2016/0492301 and U.S. Pat. No. 8,734,809.
Recently, AAVhu68, which was identified following amplification of the capsid gene from a natural source, was identified as a new AAV capsid. See, e.g., WO 2018/160582. This AAV is within Clade F, as is AAV9.
Krabbe disease (globoid cell leukodystrophy; GLD) is an autosomal recessive lysosomal storage disease (LSD) caused by mutations in the gene encoding the hydrolytic enzyme galactosylceramidase (GALC) (Wenger D. A., et al. (2000) Mol Genet Metab. 70(1):1-9). This enzyme is responsible for the degradation of certain galactolipids, including galactosylceramide (ceramide) and galactosylsphingosine (psychosine), which are found almost exclusively in the myelin sheath. In Krabbe disease, GALC deficiency causes toxic accumulation of psychosine (but not galactosylceramide) in the lysosomes (Svennerholm et al., 1980). The accumulation of psychosine is particularly toxic to myelin-producing oligodendrocytes in the CNS and Schwann cells in the PNS, resulting in rapid and widespread death of these cell types. Myelin breakdown in both the CNS and PNS is accompanied by reactive astroytic gliosis and the infiltration of giant multinucleated macrophages (“globoid cells”) (Suzuki K. (2003) J Child Neurol. 18(9):595-603). Galactosylceramide does not accumulate in the absence of GALC activity due primarily to hydrolysis by another enzyme, GM1 ganglioside β-galactosidase (Kobayashi T., et al. (1985) J Biol Chem. 260(28):14982-7) and the death of oligodendrocytes contributing to an arrest in the galactosylceramide synthesis (Svennerholm L., et al. (1980) J Lipid Res. 21(1):53-64).
The only disease-modifying treatment currently available for Krabbe disease is hematopoietic stem cell transplant (HSCT), which is often provided by umbilical cord blood transplant (UCBT), allogeneic peripheral blood stem cells, or allogeneic bone marrow. There has been only modest success using HSCT to treat patients with infantile Krabbe disease, who typically present with symptoms before their first birthday. When performed after the onset of overt symptoms in infantile Krabbe disease, HSCT provides only minimal neurologic improvement and does not substantially improve survival (Escolar M. L., et al. (2005) N Engl J Med. 352(20):2069-81). HSCT can be efficacious when performed in pre-symptomatic patients, but even then, motor outcomes are poor (Escolar M. L., et al. (2005) N Engl J Med. 352(20):2069-81; Wright M. D., et al. (2017) Neurology. 89(13):1365-1372; van den Broek B. T. A., et al. (2018) Blood Adv. 2(1):49-60). Infants transplanted before 30 days of age had better survival and functional outcomes compared with those transplanted later (Allewelt H., et al. (2018) Biol Blood Marrow Transplant. 24(11):2233-2238). Presymptomatic transplantation is reported to result in significantly better outcomes with progressive central myelination, normal receptive language, attenuation of symptom severity, and longer survival compared with infantile Krabbe disease patients who were either untreated or treated after symptom onset (Escolar M. L., et al. (2005) N Engl J Med. 352(20):2069-81; Duffner P. K., et al. (2009) Genet Med. 11(6):450-4; Wright M. D., et al. (2017) Neurology. 89(13):1365-1372). Even so, most children treated before the emergence of symptoms remain well below average for height and weight, and have progressive gross motor delays ranging from mild spasticity to inability to walk independently (Escolar M. L., et al. (2005) N Engl J Med. 352(20):2069-81; Duffner P. K., et al. (2009) Genet Med. 11(6):450-4). Some children also have residual impairments, including acquired microcephaly, the need for gastrostomy, and dysarthria (Duffner P. K., et al. (2009) Genet Med. 11(6):450-4). Moreover, HSCT only appears to influence the CNS-specific disease pathology. Clinical features associated with the PNS pathology, such as peripheral neuropathy, remain unaffected by HSCT. These results highlight the limitations of HSCT, especially in early onset forms where rapid disease progression outpaces the time needed for hematopoietic stem cells to engraft, migrate to the CNS, differentiate, and provide therapeutic effect through GALC secretion and cross-correction (i.e., the process by which enzyme secreted by corrective cells is taken up by GALC-deficient cells).
There remains a need in the art for improved treatments for Krabbe disease patients.
A composition comprising a recombinant adeno-associated virus (rAAV) is provided which comprises an AAV capsid which targets cells in the central nervous system and a vector genome comprising (i) a galactosylceramidase coding sequence encoding a mature galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 under the control of regulatory sequences which direct expression of the protein, and (ii) AAV inverted terminal repeats necessary for packaging the vector genome in an AAV capsid, wherein the vector genome is packaged in the AAV capsid. In certain embodiments, the AAV capsid is an AAVhu68 capsid. In certain embodiments, the coding sequence has the nucleic acid sequence of SEQ ID NO: 9 or a sequence 95% to 99.9% identical thereto. In certain embodiments, the coding sequence encodes the mature protein of SEQ ID NO: 10 and an exogenous signal peptide suitable for human cells in the central nervous system. In certain embodiments, the regulatory sequences comprise: a beta-actin promoter, an intron, and/or a rabbit globin polyA. In certain embodiments, the composition comprises an rAAV having the vector genome CB7.CI.hGALC.rBG.
In certain embodiments, a recombinant adeno-associated virus is provided which comprises an AAV capsid which targets cells in the central nervous system and a vector genome comprising (i) a galactosylceramidase coding sequence encoding a mature galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 under the control of regulatory sequences which direct expression of the mature galactosylceramidase protein, and (ii) AAV inverted terminal repeats necessary for packaging the vector genome in an AAV capsid. In certain embodiments, the AAV capsid is an AAVhu68 capsid. In certain embodiments, the coding sequence has the nucleic acid sequence of SEQ ID NO: 9 or a sequence 95% to 99.9% identical thereto. In certain embodiments, the coding sequence encodes the mature protein of SEQ ID NO: 10 and an exogenous signal peptide suitable for human cells in the central nervous system. In certain embodiments, the regulatory sequences comprise a beta-actin promoter, an intron, and/or a rabbit globin polyA. In certain embodiments, the vector genome is CB7.CI.hGALC.RBG.
In certain embodiments, a composition is provided which comprises a stock of rAAV which is useful for treatment of Krabbe disease. In certain embodiments, use of a composition comprising a stock of rAAV in preparing a medicament is provided. In certain embodiments, the composition provided is useful for treating dysfunction of peripheral nerves and/or for treating Krabbe disease. In certain embodiments, the rAAV is administrable as a co-therapy with hematopoietic stem cell therapy, bone marrow transplant, and/or substrate reduction therapy
In certain embodiments, a plasmid comprising a galactosylceramidase coding sequence encoding a signal peptide and a mature human galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 (aa 43 to 685) is provided. In certain embodiments, the plasmid comprises a nucleic acid sequence of SEQ ID NO: 9 or a sequence 95% to 99.9% identical thereto.
In certain embodiments, use of a composition is provided for treating Krabbe disease, correcting dysfunction of peripheral nerves which causes respiratory failure and motor function loss caused by Krabbe disease, or delaying the onset or frequency of seizures caused by Krabbe disease comprising administering to a patient a composition comprising a stock of recombinant adeno-associated virus (rAAV), said rAAV comprising: (a) an AAV capsid which targets cells in the central nervous system; and (b) a vector genome comprising a galactosylceramidase coding sequence encoding a mature galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 under the control of regulatory sequences which direct expression of the protein, said vector genome further comprising AAV inverted terminal repeats necessary for packaging the vector genome in an AAV capsid, wherein the vector genome is packaged in the AAV capsid. In certain embodiments, the patient has Late infantile Krabbe disease (LIKD). In certain embodiments, the patient has Juvenile Krabbe disease (JKD). In certain embodiments, the patient has adolescent/adult onset Krabbe disease. In certain embodiments, the rAAV is administered as a co-therapy to hematopoietic stem cell transplant (HSCT), bone marrow transplant, and/or substrate reduction therapy. In certain embodiments, the rAAV is delivered via intrathecal, intracerebroventricular, or intraparenchymal administration.
In certain embodiments, the composition provided is formulated for intrathecal, intracerebroventricular, intraparenchymal administration. In certain embodiments, the composition is administered as a single dose via a computed tomography- (CT-) guided sub-occipital injection into the cisterna magna (intra-cisterna magna).
These and other aspects of the invention will be apparent from the following detailed description of the invention.
A recombinant adeno-associated virus (rAAV) which expresses a human galactosylceramidase (GALC) protein is provided, as are compositions containing the rAAV and uses thereof. In certain embodiments, the rAAV.hGALC provides for the first time, a disease-modifying treatment for symptomatic infantile Krabbe patients (early infantile Krabbe disease, EIKD). In certain embodiments, the rAAV.hGALC provides a treatment for presymptomatic infantile patients. In certain embodiments, the rAAV.hGALC provides a therapy that can correct peripheral nerves which cause respiratory failure and motor function loss. In certain embodiments, the rAAV.hGALC provides additional options for treatment of later-onset patients for whom the benefit-risk ratio is not in favor of hematopoietic stem cell transplant (HSCT), which is currently the only disease-modifying treatment.
As used herein, a “rAAV.GALC” refers to a rAAV having an AAV capsid which has packaged therein a vector genome containing, at a minimum, a coding sequence for the galactosylceramidase protein (enzyme). rAAVhu68.GALC refers to a rAAV in which the AAV capsid is an AAVhu68 capsid, which is defined herein. The examples below also illustrate other AAV capsids.
The term “cGALC” refers to a coding sequence which expresses a canine GALC, which as used in the examples below for studies in dogs. Canine GALC has a 26 bp signal peptide and a total length of the protein of 669 amino acids.
The term “hGALC” refers to a coding sequence for a human GALC.
Isoform 1 of hGALC is the canonical sequence and is 685 amino acids in length. This amino acid sequence is reproduced in SEQ ID NO: 6. The mature protein is located at about amino acid 43 to about 685 and a signal peptide is located in positions 1 to 42, although there is some suggestion that the initiating Met is at position 17 rather than at position 1. Although multiple isoforms of GALC are known (isoforms 1-5), and over three dozen natural variants have been described, the present inventors have discovered that a variation having a threonine (T) to Alanine (A) mutation at position 641 is particularly desirable. This sequence is provided in SEQ ID NO: 10. This variant is the protein sequence encoded by the human galactosylceramidase (hGALC) coding sequence illustrated in the examples in the rAAV and vector genomes provided herein. Galactosylceramidase (GALC) is also known as galactocerebrosidase and these names are used interchangeably. In certain embodiments, this variant may be used in enzyme replacement therapy or co-therapies.
As used herein, “CB7.CI.hGALC.rBG” refers to a vector genome (e.g., as depicted in
In certain embodiments, a fusion protein is contemplated which contains at least the mature GALC with all or a portion of the native signal peptide removed (aa 1-17, or aa 1-42) and substituted with an exogenous signal peptide. Such a fusion protein may contain an exogenous signal peptide and at least the mature human GALC protein (e.g., amino acid 43 to 695 of SEQ ID NO: 6 or SEQ ID NO: 10). In certain embodiments, the fusion protein contains an exogenous signal peptide suitable for human cells in the CNS, i.e. a signal peptide that is substituted for a native signal peptide to improve production, intracellular transport, and/or secretion of the protein (i.e. hGALC) in cells present in the human CNS. Exogenous signal peptides suitable for human cells in the CNS, include, but are not limited to those natively found in an immunoglobulin (e.g., IgG), a cytokine (e.g., IL-2, IL12, IL18, or the like), insulin, albumin, β-glucuronidase, alkaline protease, von Willebrand factor (VWF), or the fibronectin secretory signal peptides (See, also, e.g., www.signalpeptide.de/index.php?m=listspdb_mammalia).
Also encompassed by the present invention are nucleic acid sequences which encode the GALC protein(s) provided herein (e.g., SEQ ID NO: 6, SEQ ID NO: 10, or fusion proteins comprising the mature GALC). In certain embodiments, a coding sequence is a cDNA sequence encoding the protein. However, also encompassed are the corresponding RNA sequences.
In certain embodiments, a nucleic acid coding sequence has the cDNA sequence of SEQ ID NO: 5 or a sequence 95% to 99.9% identical thereto, or a fragment thereof. Suitable fragments include the coding sequence for the mature protein (about nt 127 to about nt 2058), or the coding sequence for the mature protein with a fragment of the signal peptide (e.g., about nt 54 to about nt 2058). In certain embodiments, the coding sequence has the nucleic acid sequence encoding the mature hGALC of SEQ ID NO: 5 (nt 127 to 2058) or a fusion protein comprising the same and an exogenous leader, or a sequence 95% to 99.9% identical thereto. In certain embodiments, the coding sequence has the nucleic acid sequence encoding the mature hGALC of SEQ ID NO: 5 (nt 127 to 2058) or a sequence 95% to 99.9% identical thereto, or a fragment thereof comprising a fragment of the leader sequence and the mature hGALC. In certain embodiments, the coding sequence encodes a full-length human GALC protein having the amino acid sequence of SEQ ID NO: 10. In certain embodiments, the coding sequence encodes the hGALC leader (nucleic acids 1 to 126) and mature protein (encoded by nucleic acids 127 to 2058) of SEQ ID NO: 5.
In certain embodiments, the expression cassette comprises one or more miRNA target sequences that repress expression of hGALC in dorsal root ganglion (drg) (see, e.g., International Patent Application No. PCT/US19/67872, filed Feb. 12, 2020, which is incorporated herein by reference).
As used herein, Krabbe disease, also known as globoid cell leukodystrophy (GLD) is a lysosomal storage disease caused by mutation affecting the activity of galactosylceramidase (GALC), an enzyme responsible for the degradation of myelin galactolipids. Several types of Krabbe disease have been described which depend on the severity of the enzymatic deficit. From the most severe to least severe enzymatic deficit are: early infantile Krabbe disease (EIKD) defined by onset <6 months of age; late infantile Krabbe disease (LIKD) defined by onset from 7 to 12 months; juvenile Krabbe disease (JKD) defined by onset from 13 months to 10 years; and adolescent/adult onset Krabbe disease.
In certain embodiments, an effective amount of a rAAV.GALC vector increases GALC enzyme levels in the CSF to within about 30% to about 100% of normal levels. In other embodiments, an effective amount of a rAAV.GALC vector increases GALC enzyme levels in the plasma to within about 30% to about 100% of normal levels. In certain embodiments, lower amounts of increased CSF or plasma levels of GALC are observed, but an improvement is observed in one or more of the symptoms associated with Krabbe disease, as described herein.
A “recombinant AAV” or “rAAV” is a DNAse-resistant viral particle containing two elements, an AAV capsid and a vector genome containing at least non-AAV coding sequences packaged within the AAV capsid. Unless otherwise specified, this term may be used interchangeably with the phrase “rAAV vector”. The rAAV is a “replication-defective virus” or “viral vector”, as it lacks any functional AAV rep gene or functional AAV cap gene and cannot generate progeny. In certain embodiments, the only AAV sequences are the AAV inverted terminal repeat sequences (ITRs), typically located at the extreme 5′ and 3′ ends of the vector genome in order to allow the gene and regulatory sequences located between the ITRs to be packaged within the AAV capsid.
As used herein, a “vector genome” refers to the nucleic acid sequence packaged inside the rAAV capsid which forms a viral particle. Such a nucleic acid sequence contains AAV inverted terminal repeat sequences (ITRs). In the examples herein, a vector genome contains, at a minimum, from 5′ to 3′, an AAV 5′ ITR, coding sequence(s), and an AAV 3′ ITR. ITRs from AAV2, a different source AAV than the capsid, or other than full-length ITRs may be selected. In certain embodiments, the ITRs are from the same AAV source as the AAV which provides the rep function during production or a transcomplementing AAV. Further, other ITRs may be used. Further, the vector genome contains regulatory sequences which direct expression of the gene products. Suitable components of a vector genome are discussed in more detail herein.
As described in the examples below, the rAAV provided herein comprises an AAVhu68 capsid. See, e.g., WO 2018/160582, which is incorporated herein by reference. AAVhu68 is within clade F. AAVhu68 (SEQ ID NO: 2) varies from another Clade F virus AAV9 (SEQ ID NO: 4) by two encoded amino acids at positions 67 and 157 of vp1. In contrast, the other Clade F AAV (AAV9, hu31, hu31) has an Ala at position 67 and an Ala at position 157.
A rAAVhu68 is composed of an AAVhu68 capsid and a vector genome. In one embodiment, a composition comprising rAAVhu68 comprises an assembly of a heterogeneous population of vp1, a heterogeneous population of vp2, and a heterogeneous population of vp3 proteins. As used herein when used to refer to vp capsid proteins, the term “heterogeneous” or any grammatical variation thereof, refers to a population consisting of elements that are not the same, for example, having vp1, vp2 or vp3 monomers (proteins) with different modified amino acid sequences. SEQ ID NO: 2 provides the encoded amino acid sequence of the AAVhu68 vp1 protein. The AAVhu68 capsid contains subpopulations within the vp1 proteins, within the vp2 proteins and within the vp3 proteins which have modifications from the predicted amino acid residues in SEQ ID NO: 2. These subpopulations include, at a minimum, certain deamidated asparagine (N or Asn) residues. For example, certain subpopulations comprise at least one, two, three or four highly deamidated asparagines (N) positions in asparagine—glycine pairs in SEQ ID NO: 2 and optionally further comprising other deamidated amino acids, wherein the deamidation results in an amino acid change and other optional modifications. The various combinations of these and other modifications are described herein.
As used herein, a “subpopulation” of vp proteins refers to a group of vp proteins which has at least one defined characteristic in common and which consists of at least one group member to less than all members of the reference group, unless otherwise specified. For example, a “subpopulation” of vp1 proteins is at least one (1) vp1 protein and less than all vp1 proteins in an assembled AAV capsid, unless otherwise specified. A “subpopulation” of vp3 proteins may be one (1) vp3 protein to less than all vp3 proteins in an assembled AAV capsid, unless otherwise specified. For example, vp1 proteins may be a subpopulation of vp proteins; vp2 proteins may be a separate subpopulation of vp proteins, and vp3 are yet a further subpopulation of vp proteins in an assembled AAV capsid. In another example, vp1, vp2 and vp3 proteins may contain subpopulations having different modifications, e.g., at least one, two, three or four highly deamidated asparagines, e.g., at asparagine—glycine pairs.
Unless otherwise specified, highly deamidated refers to at least 45% deamidated, at least 50% deamidated, at least 60% deamidated, at least 65% deamidated, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, 97%, 99%, up to about 100% deamidated at a referenced amino acid position, as compared to the predicted amino acid sequence at the reference amino acid position (e.g., at least 80% of the asparagines at amino acid 57 of SEQ ID NO: 2 may be deamidated based on the total vp1 proteins or 20% of the asparagines at amino acid 409 of SEQ ID NO: 2 may be deamidated based on the total vp1, vp2 and vp3 proteins). Such percentages may be determined using 2D-gel, mass spectrometry techniques, or other suitable techniques.
As provided herein, each deamidated N of SEQ ID NO: 2 may independently be aspartic acid (Asp), isoaspartic acid (isoAsp), aspartate, and/or an interconverting blend of Asp and isoAsp, or combinations thereof. Any suitable ratio of α- and isoaspartic acid may be present. For example, in certain embodiments, the ratio may be from 10:1 to 1:10 aspartic to isoaspartic, about 50:50 aspartic: isoaspartic, or about 1:3 aspartic: isoaspartic, or another selected ratio. In certain embodiments, one or more glutamine (Q) in SEQ ID NO: 2 deamidates to glutamic acid (Glu), i.e., α-glutamic acid, γ-glutamic acid (Glu), or a blend of α- and γ-glutamic acid, which may interconvert through a common glutarinimide intermediate. Any suitable ratio of α- and γ-glutamic acid may be present. For example, in certain embodiments, the ratio may be from 10:1 to 1:10 α to γ, about 50:50 α:γ, or about 1:3 α:γ, or another selected ratio.
Thus, an rAAVhu68 includes subpopulations within the rAAVhu68 capsid of vp1, vp2 and/or vp3 proteins with deamidated amino acids, including at a minimum, at least one subpopulation comprising at least one highly deamidated asparagine. In addition, other modifications may include isomerization, particularly at selected aspartic acid (D or Asp) residue positions. In still other embodiments, modifications may include an amidation at an Asp position.
In certain embodiments, an AAVhu68 capsid contains subpopulations of vp1, vp2 and vp3 having at least 4 to at least about 25 deamidated amino acid residue positions, of which at least 1 to 10% are deamidated as compared to the encoded amino acid sequence of SEQ ID NO: 2. The majority of these may be N residues. However, Q residues may also be deamidated.
In certain embodiments, an AAVhu68 capsid is further characterized by one or more of the following. AAVhu68 capsid proteins that comprise: AAVhu68 vp1 proteins produced by expression from a nucleic acid sequence which encodes the predicted amino acid sequence of 1 to 736 of SEQ ID NO: 2, vp1 proteins produced from SEQ ID NO: 1, or vpl proteins produced from a nucleic acid sequence at least 70% identical to SEQ ID NO:1 which encodes the predicted amino acid sequence of 1 to 736 of SEQ ID NO: 2; AAVhu68 vp2 proteins produced by expression from a nucleic acid sequence which encodes the predicted amino acid sequence of at least about amino acids 138 to 736 of SEQ ID NO:2, vp2 proteins produced from a sequence comprising at least nucleotides 412 to 2211 of SEQ ID NO:1, or vp2 proteins produced from a nucleic acid sequence at least 70% identical to at least nucleotides 412 to 2211 of SEQ ID NO: 1 which encodes the predicted amino acid sequence of at least about amino acids 138 to 736 of SEQ ID NO: 2, and/or AAVhu68 vp3 proteins produced by expression from a nucleic acid sequence which encodes the predicted amino acid sequence of at least about amino acids 203 to 736 of SEQ ID NO: 2, vp3 proteins produced from a sequence comprising at least nucleotides 607 to 2211 of SEQ ID NO: 1, or vp3 proteins produced from a nucleic acid sequence at least 70% identical to at least nucleotides 607 to 2211 of SEQ ID NO: 1 which encodes the predicted amino acid sequence of at least about amino acids 203 to 736 of SEQ ID NO: 2.
Additionally or alternatively, an AAV capsid is provided which comprises a heterogeneous population of vp1 proteins optionally comprising a valine at position 157, a heterogeneous population of vp2 proteins optionally comprising a valine at position 157, and a heterogeneous population of vp3 proteins, wherein at least a subpopulation of the vp1 and vp2 proteins comprise a valine at position 157 and optionally further comprising a glutamic acid at position 67 based on the numbering of the vp1 capsid of SEQ ID NO:2. Additionally or alternatively, an AAVhu68 capsid is provided which comprises a heterogeneous population of vp1 proteins which are the product of a nucleic acid sequence encoding the amino acid sequence of SEQ ID NO: 2, a heterogeneous population of vp2 proteins which are the product of a nucleic acid sequence encoding the amino acid sequence of at least about amino acids 138 to 736 of SEQ ID NO: 2, and a heterogeneous population of vp3 proteins which are the product of a nucleic acid sequence encoding at least amino acids 203 to 736 of SEQ ID NO: 2, wherein: the vp1, vp2 and vp3 proteins contain subpopulations with amino acid modifications
The AAVhu68 vp1, vp2 and vp3 proteins are typically expressed as alternative splice variants encoded by the same nucleic acid sequence which encodes the full-length vp1 amino acid sequence of SEQ ID NO: 2 (amino acid 1 to 736). Optionally the vp1-encoding sequence is used alone to express the vp1, vp2 and vp3 proteins. Alternatively, this sequence may be co-expressed with one or more of a nucleic acid sequence which encodes the AAVhu68 vp3 amino acid sequence of SEQ ID NO: 2 (about aa 203 to 736) without the vp1-unique region (about aa 1 to about aa 137) and/or vp2-unique regions (about aa 1 to about aa 202), or a strand complementary thereto, the corresponding mRNA or tRNA (about nt 607 to about nt 2211 of SEQ ID NO: 1), or a sequence at least 70% to at least 99% (e.g., at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99%) identical to SEQ ID NO: 1 which encodes aa 203 to 736 of SEQ ID NO: 2. Additionally, or alternatively, the vp1-encoding and/or the vp2-encoding sequence may be co-expressed with the nucleic acid sequence which encodes the AAVhu68 vp2 amino acid sequence of SEQ ID NO: 2 (about aa 138 to 736) without the vp1-unique region (about aa 1 to about 137), or a strand complementary thereto, the corresponding mRNA or tRNA (nt 412 to 22121 of SEQ ID NO: 1), or a sequence at least 70% to at least 99% (e.g., at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99%) identical to SEQ ID NO: 1 which encodes about aa 138 to 736 of SEQ ID NO: 2.
As described herein, a rAAVhu68 has a rAAVhu68 capsid produced in a production system expressing capsids from an AAVhu68 nucleic acid which encodes the vp1 amino acid sequence of SEQ ID NO: 2, and optionally additional nucleic acid sequences, e.g., encoding a vp3 protein free of the vp1 and/or vp2-unique regions. The rAAVhu68 resulting from production using a single nucleic acid sequence vp1 produces the heterogeneous populations of vp1 proteins, vp2 proteins and vp3 proteins. More particularly, the rAAVhu68 capsid contains subpopulations within the vp1 proteins, within the vp2 proteins and within the vp3 proteins which have modifications from the predicted amino acid residues in SEQ ID NO:2. These subpopulations include, at a minimum, deamidated asparagine (N or Asn) residues. For example, asparagines in asparagine-glycine pairs are highly deamidated.
In one embodiment, the AAVhu68 vp1 nucleic acid sequence has the sequence of SEQ ID NO: 1, or a strand complementary thereto, e.g., the corresponding mRNA or tRNA. In certain embodiments, the vp2 and/or vp3 proteins may be expressed additionally or alternatively from different nucleic acid sequences than the vp1, e.g., to alter the ratio of the vp proteins in a selected expression system. In certain embodiments, also provided is a nucleic acid sequence which encodes the AAVhu68 vp3 amino acid sequence of SEQ ID NO: 2 (about aa 203 to 736) without the vp1-unique region (about aa 1 to about aa 137) and/or vp2-unique regions (about aa 1 to about aa 202), or a strand complementary thereto, the corresponding mRNA or tRNA (about nt 607 to about nt 2211 of SEQ ID NO: 1). In certain embodiments, also provided is a nucleic acid sequence which encodes the AAVhu68 vp2 amino acid sequence of SEQ ID NO: 2 (about aa 138 to 736) without the vp1-unique region (about aa 1 to about 137), or a strand complementary thereto, the corresponding mRNA or tRNA (nt 412 to 2211 of SEQ ID NO: 1).
However, other nucleic acid sequences which encode the amino acid sequence of SEQ ID NO: 2 may be selected for use in producing rAAVhu68 capsids. In certain embodiments, the nucleic acid sequence has the nucleic acid sequence of SEQ ID NO: 1 or a sequence at least 70% to 99% identical, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, or at least 99% identical to SEQ ID NO: 1 which encodes SEQ ID NO: 2. In certain embodiments, the nucleic acid sequence has the nucleic acid sequence of SEQ ID NO: 1 or a sequence at least 70% to 99%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, or at least 99% identical to about nt 412 to about nt 2211 of SEQ ID NO: 1 which encodes the vp2 capsid protein (about aa 138 to 736) of SEQ ID NO: 2. In certain embodiments, the nucleic acid sequence has the nucleic acid sequence of about nt 607 to about nt 2211 of SEQ ID NO: 1 or a sequence at least 70% to 99.%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, or at least 99% identical to about nt 607 to about nt 2211 SEQ ID NO: 1 which encodes the vp3 capsid protein (about aa 203 to 736) of SEQ ID NO: 2.
It is within the skill in the art to design nucleic acid sequences encoding this rAAVhu68 capsid, including DNA (genomic or cDNA), or RNA (e.g., mRNA). In certain embodiments, the nucleic acid sequence encoding the AAVhu68 vp1 capsid protein is provided in SEQ ID NO: 1. In other embodiments, a nucleic acid sequence of 70% to 99.9% identity to SEQ ID NO: 1 may be selected to express the AAVhu68 capsid proteins. In certain other embodiments, the nucleic acid sequence is at least about 75% identical, at least 80% identical, at least 85%, at least 90%, at least 95%, at least 97% identical, or at least 99% to 99.9% identical to SEQ ID NO: 1. Such nucleic acid sequences may be codon-optimized for expression in a selected system (i.e., cell type) can be designed by various methods. This optimization may be performed using methods which are available on-line (e.g., GeneArt), published methods, or a company which provides codon optimizing services, e.g., DNA2.0 (Menlo Park, Calif.). One codon optimizing method is described, e.g., in US International Patent Publication No. WO 2015/012924, which is incorporated by reference herein in its entirety. See also, e.g., US Patent Publication No. 2014/0032186 and US Patent Publication No. 2006/0136184. Suitably, the entire length of the open reading frame (ORF) for the product is modified. However, in some embodiments, only a fragment of the ORF may be altered. By using one of these methods, one can apply the frequencies to any given polypeptide sequence and produce a nucleic acid fragment of a codon-optimized coding region which encodes the polypeptide. A number of options are available for performing the actual changes to the codons or for synthesizing the codon-optimized coding regions designed as described herein. Such modifications or synthesis can be performed using standard and routine molecular biological manipulations well known to those of ordinary skill in the art. In one approach, a series of complementary oligonucleotide pairs of 80-90 nucleotides each in length and spanning the length of the desired sequence are synthesized by standard methods. These oligonucleotide pairs are synthesized such that upon annealing, they form double stranded fragments of 80-90 base pairs, containing cohesive ends, e.g., each oligonucleotide in the pair is synthesized to extend 3, 4, 5, 6, 7, 8, 9, 10, or more bases beyond the region that is complementary to the other oligonucleotide in the pair. The single-stranded ends of each pair of oligonucleotides are designed to anneal with the single-stranded end of another pair of oligonucleotides. The oligonucleotide pairs are allowed to anneal, and approximately five to six of these double-stranded fragments are then allowed to anneal together via the cohesive single stranded ends, and then they ligated together and cloned into a standard bacterial cloning vector, for example, a TOPO® vector available from Invitrogen Corporation, Carlsbad, Calif. The construct is then sequenced by standard methods. Several of these constructs consisting of 5 to 6 fragments of 80 to 90 base pair fragments ligated together, i.e., fragments of about 500 base pairs, are prepared, such that the entire desired sequence is represented in a series of plasmid constructs. The inserts of these plasmids are then cut with appropriate restriction enzymes and ligated together to form the final construct. The final construct is then cloned into a standard bacterial cloning vector, and sequenced. Additional methods would be immediately apparent to the skilled artisan. In addition, gene synthesis is readily available commercially.
In certain embodiments, the asparagine (N) in N-G pairs in the rAAVhu68 vp 1, vp2 and vp3 proteins are highly deamidated. In the case of the rAAVhu68 capsid protein, 4 residues (N57, N329, N452, N512) routinely display levels of deamidation >70% and it most cases >90% across various lots. Additional asparagine residues (N94, N253, N270, N304, N409, N477, and Q599) also display deamidation levels up to ˜20% across various lots. The deamidation levels were initially identified using a trypsin digest and verified with a chymotrypsin digestion.
In certain embodiments, an rAAVhu68 capsid contains subpopulations of AAV vp1, vp2 and/or vp3 capsid proteins having at least four asparagine (N) positions in the rAAVhu68 capsid proteins which are highly deamidated. In certain embodiments, about 20 to 50% of the N-N pairs (exclusive of N-N-N triplets) show deamidation. In certain embodiments, the first N is deamidated. In certain embodiments, the second N is deamidated. In certain embodiments, the deamidation is between about 15% to about 25% deamidation. Deamidation at the Q at position 259 of SEQ ID NO: 2 is about 8% to about 42% of the AAVhu68 vp1, vp2 and vp3 capsid proteins of an AAVhu68 protein.
In certain embodiments, the rAAVhu68 capsid is further characterized by an amidation in D297 the vp1, vp2 and vp3 proteins. In certain embodiments, about 70% to about 75% of the D at position 297 of the vp1, vp2 and/or vp3 proteins in a AAVhu68 capsid are amidated, based on the numbering of SEQ ID NO: 2. In certain embodiments, at least one Asp in the vp1, vp2 and/or vp3 of the capsid is isomerized to D-Asp. Such isomers are generally present in an amount of less than about 1% of the Asp at one or more of residue positions 97, 107, 384, based on the numbering of SEQ ID NO: 2.
In certain embodiments, a rAAVhu68 has an AAVhu68 capsid having vp1, vp2 and vp3 proteins having subpopulations comprising combinations of one, two, three, four or more deamidated residues at the positions set forth in the table below. Deamidation in the rAAV may be determined using 2D gel electrophoresis, and/or mass spectrometry, and/or protein modelling techniques. Online chromatography may be performed with an Acclaim PepMap column and a Thermo UltiMate 3000 RSLC system (Thermo Fisher Scientific) coupled to a Q Exactive HF with a NanoFlex source (Thermo Fisher Scientific). MS data is acquired using a data-dependent top-20 method for the Q Exactive HF, dynamically choosing the most abundant not-yet-sequenced precursor ions from the survey scans (200-2000 m/z). Sequencing is performed via higher energy collisional dissociation fragmentation with a target value of 1e5 ions determined with predictive automatic gain control and an isolation of precursors was performed with a window of 4 m/z. Survey scans were acquired at a resolution of 120,000 at m/z 200. Resolution for HCD spectra may be set to 30,000 at m/z200 with a maximum ion injection time of 50 ms and a normalized collision energy of 30. The S-lens RF level may be set at 50, to give optimal transmission of the m/z region occupied by the peptides from the digest. Precursor ions may be excluded with single, unassigned, or six and higher charge states from fragmentation selection. BioPharma Finder 1.0 software (Thermo Fischer Scientific) may be used for analysis of the data acquired. For peptide mapping, searches are performed using a single-entry protein FASTA database with carbamidomethylation set as a fixed modification; and oxidation, deamidation, and phosphorylation set as variable modifications, a 10-ppm mass accuracy, a high protease specificity, and a confidence level of 0.8 for MS/MS spectra. Examples of suitable proteases may include, e.g., trypsin or chymotrypsin. Mass spectrometric identification of deamidated peptides is relatively straightforward, as deamidation adds to the mass of intact molecule +0.984 Da (the mass difference between —OH and —NH2 groups). The percent deamidation of a particular peptide is determined mass area of the deamidated peptide divided by the sum of the area of the deamidated and native peptides. Considering the number of possible deamidation sites, isobaric species which are deamidated at different sites may co-migrate in a single peak. Consequently, fragment ions originating from peptides with multiple potential deamidation sites can be used to locate or differentiate multiple sites of deamidation. In these cases, the relative intensities within the observed isotope patterns can be used to specifically determine the relative abundance of the different deamidated peptide isomers. This method assumes that the fragmentation efficiency for all isomeric species is the same and independent on the site of deamidation. It will be understood by one of skill in the art that a number of variations on these illustrative methods can be used. For example, suitable mass spectrometers may include, e.g, a quadrupole time of flight mass spectrometer (QTOF), such as a Waters Xevo or Agilent 6530 or an orbitrap instrument, such as the Orbitrap Fusion or Orbitrap Velos (Thermo Fisher). Suitably liquid chromatography systems include, e.g., Acquity UPLC system from Waters or Agilent systems (1100 or 1200 series). Suitable data analysis software may include, e.g., MassLynx (Waters), Pinpoint and Pepfinder (Thermo Fischer Scientific), Mascot (Matrix Science), Peaks DB (Bioinformatics Solutions). Still other techniques may be described, e.g., in X. Jin et al, Hu Gene Therapy Methods, Vol. 28, No. 5, pp. 255-267, published online Jun. 16, 2017.
In certain embodiments, the AAVhu68 capsid is characterized by having capsid proteins in which at least 45% of N residues are deamidated at least one of positions N57, N329, N452, and/or N512 based on the numbering of amino acid sequence of SEQ ID NO: 2. In certain embodiments, at least about 60%, at least about 70%, at least about 80%, or at least 90% of the N residues at one or more of these N-G positions (i.e., N57, N329, N452, and/or N512, based on the numbering of amino acid sequence of SEQ ID NO: 2) are deamidated. In these and other embodiments, an AAVhu68 capsid is further characterized by having a population of proteins in which about 1% to about 20% of the N residues have deamidations at one or more of positions: N94, N253, N270, N304, N409, N477, and/or Q599, based on the numbering of amino acid sequence of SEQ ID NO: 2. In certain embodiments, the AAVhu68 comprises at least a subpopulation of vp 1, vp2 and/or vp3 proteins which are deamidated at one or more of positions N35, N57, N66, N94, N113, N252, N253, Q259, N270, N303, N304, N305, N319, N328, N329, N336, N409, N410, N452, N477, N515, N598, Q599, N628, N651, N663, N709, N735, based on the numbering of amino acid sequence of SEQ ID NO: 2, or combinations thereof. In certain embodiments, the capsid proteins may have one or more amidated amino acids.
Still other modifications are observed, most of which do not result in conversion of one amino acid to a different amino acid residue. Optionally, at least one Lys in the vp1, vp2 and vp3 of the capsid are acetylated. Optionally, at least one Asp in the vp1, vp2 and/or vp3 of the capsid is isomerized to D-Asp. Optionally, at least one S (Ser, Serine) in the vp1, vp2 and/or vp3 of the capsid is phosphorylated. Optionally, at least one T (Thr, Threonine) in the vp1, vp2 and/or vp3 of the capsid is phosphorylated. Optionally, at least one W (trp, tryptophan) in the vp1, vp2 and/or vp3 of the capsid is oxidized. Optionally, at least one M (Met, Methionine) in the vp1, vp2 and/or vp3 of the capsid is oxidized. In certain embodiments, the capsid proteins have one or more phosphorylations. For example, certain vpl capsid proteins may be phosphorylated at position 149.
In certain embodiments, an rAAVhu68 capsid comprises a heterogeneous population of vp1 proteins which are the product of a nucleic acid sequence encoding the amino acid sequence of SEQ ID NO: 2, wherein the vp1 proteins comprise a Glutamic acid (Glu) at position 67 and/or a valine (Val) at position 157; a heterogeneous population of vp2 proteins optionally comprising a valine (Val) at position 157; and a heterogeneous population of vp3 proteins. The AAVhu68 capsid contains at least one subpopulation in which at least 65% of asparagines (N) in asparagine—glycine pairs located at position 57 of the vp1 proteins and at least 70% of asparagines (N) in asparagine—glycine pairs at positions 329, 452 and/or 512 of the vp1, v2 and vp3 proteins are deamidated, based on the residue numbering of the amino acid sequence of SEQ ID NO: 2, wherein the deamidation results in an amino acid change.
As discussed in more detail herein, the deamidated asparagines may be deamidated to aspartic acid, isoaspartic acid, an interconverting aspartic acid/isoaspartic acid pair, or combinations thereof. In certain embodiments, the rAAVhu68 are further characterized by one or more of: (a) each of the vp2 proteins is independently the product of a nucleic acid sequence encoding at least the vp2 protein of SEQ ID NO: 2; (b) each of the vp3 proteins is independently the product of a nucleic acid sequence encoding at least the vp3 protein of SEQ ID NO: 2; (c) the nucleic acid sequence encoding the vp1 proteins is SEQ ID NO: 1, or a sequence at least 70% to at least 99% (e.g., at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99%) identical to SEQ ID NO: 1 which encodes the amino acid sequence of SEQ ID NO: 2. Optionally that sequence is used alone to express the vp1, vp2 and vp3 proteins. Alternatively, this sequence may be co-expressed with one or more of a nucleic acid sequence which encodes the AAVhu68 vp3 amino acid sequence of SEQ ID NO: 2 (about aa 203 to 736) without the vp1-unique region (about aa 1 to about aa 137) and/or vp2-unique regions (about aa 1 to about aa 202), or a strand complementary thereto, the corresponding mRNA or tRNA (about nt 607 to about nt 2211 of SEQ ID NO: 1), or a sequence at least 70% to at least 99% (e.g., at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99%) identical to SEQ ID NO: 1 which encodes aa 203 to 736 of SEQ ID NO: 2. Additionally, or alternatively, the vp1-encoding and/or the vp2-encoding sequence may be co-expressed with the nucleic acid sequence which encodes the AAVhu68 vp2 amino acid sequence of SEQ ID NO: 2 (about aa 138 to 736) without the vp1-unique region (about aa 1 to about 137), or a strand complementary thereto, the corresponding mRNA or tRNA (nt 412 to 2211 of SEQ ID NO: 1), or a sequence at least 70% to at least 99% (e.g., at least 85%, at least 90%, at least 95%, at least 97%, at least 98% or at least 99%) identical to SEQ ID NO: 1 which encodes about aa 138 to 736 of SEQ ID NO: 2.
Additionally or alternatively, the rAAVhu68 capsid comprises at least a subpopulation of vp 1, vp2 and/or vp3 proteins which are deamidated at one or more of positions N57, N66, N94, N113, N252, N253, Q259, N270, N303, N304, N305, N319, N328, N329, N336, N409, N410, N452, N477, N512, N515, N598, Q599, N628, N651, N663, N709, based on the numbering of SEQ ID NO:2, or combinations thereof; (e) rAAVhu68 capsid comprises a subpopulation of vp1, vp2 and/or vp3 proteins which comprise 1% to 20% deamidation at one or more of positions N66, N94, N113, N252, N253, Q259, N270, N303, N304, N305, N319, N328, N336, N409, N410, N477, N515, N598, Q599, N628, N651, N663, N709, based on the numbering of SEQ ID NO:2, or combinations thereof; (f) the rAAVhu68 capsid comprises a subpopulation of vp1 in which 65% to 100% of the N at position 57 of the vp1 proteins, based on the numbering of SEQ ID NO:2, are deamidated; (g) the rAAVhu68 capsid comprises subpopulation of vp1 proteins in which 75% to 100% of the N at position 57 of the vp1 proteins are deamidated; (h) the rAAVhu68 capsid comprises subpopulation of vp1 proteins, vp2 proteins, and/or vp3 proteins in which 80% to 100% of the N at position 329, based on the numbering of SEQ ID NO:2, are deamidated; (i) the rAAVhu68 capsid comprises subpopulation of vp1 proteins, vp2 proteins, and/or vp3 proteins in which 80% to 100% of the N at position 452, based on the numbering of SEQ ID NO:2, are deamidated; (j) the rAAVhu68 capsid comprises subpopulation of vpl proteins, vp2 proteins, and/or vp3 proteins in which 80% to 100% of the N at position 512, based on the numbering of SEQ ID NO: 2, are deamidated; (k) the rAAV comprises about 60 total capsid proteins in a ratio of about 1 vp1 to about 1 to 1.5 vp2 to 3 to 10 vp3 proteins; (1) the rAAV comprises about 60 total capsid proteins in a ratio of about 1 vp1 to about 1 vp2 to 3 to 9 vp3 proteins.
In certain embodiments, the AAVhu68 is modified to change the glycine in an asparagine-glycine pair, in order to reduce deamidation. In other embodiments, the asparagine is altered to a different amino acid, e.g., a glutamine which deamidates at a slower rate; or to an amino acid which lacks amide groups (e.g., glutamine and asparagine contain amide groups); and/or to an amino acid which lacks amine groups (e.g., lysine, arginine and histidine contain amide groups). As used herein, amino acids lacking amide or amine side groups refer to, e.g., glycine, alanine, valine, leucine, isoleucine, serine, threonine, cystine, phenylalanine, tyrosine, or tryptophan, and/or proline. Modifications such as described may be in one, two, or three of the asparagine-glycine pairs found in the encoded AAVhu68 amino acid sequence. In certain embodiments, such modifications are not made in all four of the asparagine-glycine pairs. Thus, a method is provided for reducing deamidation of rAAVhu68 and/or engineered rAAVhu68 variants having lower deamidation rates. Additionally, one or more other amide amino acids may be changed to a non-amide amino acid to reduce deamidation of the rAAVhu68.
These amino acid modifications may be made by conventional genetic engineering techniques. For example, a nucleic acid sequence containing modified AAVhu68 vp codons may be generated in which one to three of the codons encoding glycine at position 58, 330, 453 and/or 513 in SEQ ID NO: 2 (asparagine-glycine pairs) are modified to encode an amino acid other than glycine. In certain embodiments, a nucleic acid sequence containing modified asparagine codons may be engineered at one to three of the asparagine-glycine pairs located at position 57, 329, 452 and/or 512 in SEQ ID NO: 2, such that the modified codon encodes an amino acid other than asparagine. Each modified codon may encode a different amino acid. Alternatively, one or more of the altered codons may encode the same amino acid. In certain embodiments, these modified AAVhu68 nucleic acid sequences may be used to generate a mutant rAAVhu68 having a capsid with lower deamidation than the native hu68 capsid. Such mutant rAAVhu68 may have reduced immunogenicity and/or increase stability on storage, particularly storage in suspension form. As used herein, a “codon” refers to three nucleotides in a sequence which encodes an amino acid.
As used herein, “encoded amino acid sequence” refers to the amino acid which is predicted based on the translation of a known DNA codon of a referenced nucleic acid sequence being translated to an amino acid. The following table illustrates DNA codons and twenty common amino acids, showing both the single letter code (SLC) and three letter code (3LC).
rAAVhu68 capsids may be useful in certain embodiments. For example, such capsids may be used in generating monoclonal antibodies and/or generating reagents useful in assays for monitoring AAVhu68 concentration levels in gene therapy patients. Techniques for generating useful anti-AAVhu68 antibodies, labelling such antibodies or empty capsids, and suitable assay formats are known to those of skill in the art.
In certain embodiments, provided herein is a nucleic acid sequence of SEQ ID NO: 1 or a sequence at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 99%, which encodes the vp1 amino acid sequence of SEQ ID NO: 2 with a modification (e.g., deamidated amino acid) as described herein. In certain embodiments, the vp1 amino acid sequence is reproduced in SEQ ID NO: 2.
As used herein, the term “clade” as it relates to groups of AAV refers to a group of AAV which are phylogenetically related to one another as determined using a Neighbor-Joining algorithm by a bootstrap value of at least 75% (of at least 1000 replicates) and a Poisson correction distance measurement of no more than 0.05, based on alignment of the AAV vp1 amino acid sequence. The Neighbor-Joining algorithm has been described in the literature. See, e.g., M. Nei and S. Kumar, Molecular Evolution and Phylogenetics (Oxford University Press, New York (2000). Computer programs are available that can be used to implement this algorithm. For example, the MEGA v2.1 program implements the modified Nei-Gojobori method. Using these techniques and computer programs, and the sequence of an AAV vp1 capsid protein, one of skill in the art can readily determine whether a selected AAV is contained in one of the clades identified herein, in another clade, or is outside these clades. See, e.g., G Gao, et al, J Virol, 2004 June; 78(10: 6381-6388, which identifies Clades A, B, C, D, E and F, GenBank Accession Numbers AY530553 to AY530629. See, also, WO 2005/033321.
As used herein, an “AAV9 capsid” is a self-assembled AAV capsid composed of multiple AAV9 vp proteins. The AAV9 vp proteins are typically expressed as alternative splice variants encoded by a nucleic acid sequence of SEQ ID NO: 3 which encodes the vp1 amino acid sequence of SEQ ID NO: 4 (GenBank accession: AAS99264). These splice variants result in proteins of different length of SEQ ID NO: 4. In certain embodiments, “AAV9 capsid” includes an AAV having an amino acid sequence which is 99% identical to AAS99264 or 99% identical to SEQ ID NO: 4. See, also U.S. Pat. No. 7,906,111 and WO 2005/033321. As used herein “AAV9 variants” include those described in, e.g., WO2016/049230, U.S. Pat. No. 8,927,514, US 2015/0344911, and U.S. Pat. No. 8,734,809.
Methods of generating the capsid, coding sequences therefore, and methods for production of rAAV viral vectors have been described. See, e.g., Gao, et al, Proc. Natl. Acad. Sci. U.S.A. 100 (10), 6081-6086 (2003) and US 2013/0045186A1.
The term “substantial homology” or “substantial similarity,” when referring to a nucleic acid, or fragment thereof, indicates that, when optimally aligned with appropriate nucleotide insertions or deletions with another nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 95 to 99% of the aligned sequences. Preferably, the homology is over full-length sequence, or an open reading frame thereof, or another suitable fragment which is at least 15 nucleotides in length. Examples of suitable fragments are described herein.
The terms “sequence identity” “percent sequence identity” or “percent identical” in the context of nucleic acid sequences refers to the residues in the two sequences which are the same when aligned for maximum correspondence. The length of sequence identity comparison may be over the full-length of the genome, the full-length of a gene coding sequence, or a fragment of at least about 500 to 5000 nucleotides, is desired. However, identity among smaller fragments, e.g. of at least about nine nucleotides, usually at least about 20 to 24 nucleotides, at least about 28 to 32 nucleotides, at least about 36 or more nucleotides, may also be desired. Similarly, “percent sequence identity” may be readily determined for amino acid sequences, over the full-length of a protein, or a fragment thereof. Suitably, a fragment is at least about 8 amino acids in length and may be up to about 700 amino acids. Examples of suitable fragments are described herein.
The term “substantial homology” or “substantial similarity,” when referring to amino acids or fragments thereof, indicates that, when optimally aligned with appropriate amino acid insertions or deletions with another amino acid (or its complementary strand), there is amino acid sequence identity in at least about 95 to 99% of the aligned sequences. Preferably, the homology is over full-length sequence, or a protein thereof, e.g., a cap protein, a rep protein, or a fragment thereof which is at least 8 amino acids, or more desirably, at least 15 amino acids in length. Examples of suitable fragments are described herein.
By the term “highly conserved” is meant at least 80% identity, preferably at least 90% identity, and more preferably, over 97% identity. Identity is readily determined by one of skill in the art by resort to algorithms and computer programs known by those of skill in the art.
Generally, when referring to “identity”, “homology”, or “similarity” between two different adeno-associated viruses, “identity”, “homology” or “similarity” is determined in reference to “aligned” sequences. “Aligned” sequences or “alignments” refer to multiple nucleic acid sequences or protein (amino acids) sequences, often containing corrections for missing or additional bases or amino acids as compared to a reference sequence. In the examples, AAV alignments are performed using the published AAV9 sequences as a reference point. Alignments are performed using any of a variety of publicly or commercially available Multiple Sequence Alignment Programs. Examples of such programs include, “Clustal Omega”, “Clustal W”, “CAP Sequence Assembly”, “MAP”, and “MEME”, which are accessible through Web Servers on the internet. Other sources for such programs are known to those of skill in the art. Alternatively, Vector NTI utilities are also used. There are also a number of algorithms known in the art that can be used to measure nucleotide sequence identity, including those contained in the programs described above. As another example, polynucleotide sequences can be compared using Fasta™, a program in GCG Version 6.1. Fasta™ provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences. For instance, percent sequence identity between nucleic acid sequences can be determined using Fasta™ with its default parameters (a word size of 6 and the NOPAM factor for the scoring matrix) as provided in GCG Version 6.1, herein incorporated by reference. Multiple sequence alignment programs are also available for amino acid sequences, e.g., the “Clustal Omega”, “Clustal X”, “MAP”, “PIMA”, “MSA”, “BLOCKMAKER”, “MEME”, and “Match-Box” programs. Generally, any of these programs are used at default settings, although one of skill in the art can alter these settings as needed. Alternatively, one of skill in the art can utilize another algorithm or computer program which provides at least the level of identity or alignment as that provided by the referenced algorithms and programs. See, e.g., J. D. Thomson et al, Nucl. Acids. Res., “A comprehensive comparison of multiple sequence alignments”, 27(13):2682-2690 (1999).
rAAV Vectors
As indicated above, the AAVhu68 sequences and proteins are useful in production of rAAV, and are also useful in recombinant AAV vectors which may be antisense delivery vectors, gene therapy vectors, or vaccine vectors. Additionally, the engineered AAV capsids described herein, e.g., those having mutant amino acids at position 67, 157, or both relative to the numbering of the vp1 capsid protein in SEQ ID NO: 2, may be used to engineer rAAV vectors for delivery of a number of suitable nucleic acid molecules to target cells and tissues.
Genomic sequences which are packaged into an AAV capsid and delivered to a host cell are typically composed of, at a minimum, a transgene and its regulatory sequences, and AAV inverted terminal repeats (ITRs). Both single-stranded AAV and self-complementary (sc) AAV are encompassed with the rAAV. The transgene is a nucleic acid coding sequence, heterologous to the vector sequences, which encodes a polypeptide, protein, functional RNA molecule (e.g., miRNA, miRNA inhibitor) or other gene product, of interest.
In particular, the present disclosure provides rAAV comprising a coding sequence of human galactosylceramidase (GALC). In some embodiments, the coding sequence is an engineered GALC coding sequence. In some embodiments, the coding sequence is the sequence of cGALC gene (cGALCco) of SEQ ID NO: 9.
The nucleic acid coding sequence is operatively linked to regulatory components in a manner which permits transgene transcription, translation, and/or expression in a cell of a target tissue. In some embodiments, the regulatory sequences comprise a beta-actin promoter, an intron, and a rabbit globin polyA. In some embodiments, the regulatory sequences comprise SEQ ID NO: 13. In some embodiments, the regulatory sequences comprise SEQ ID NO: 15. In some embodiments, the regulatory sequences comprise SEQ ID NO: 16.
The AAV sequences of the vector typically comprise the cis-acting 5′ and 3′ inverted terminal repeat sequences (See, e.g., B. J. Carter, in “Handbook of Parvoviruses”, ed., P. Tijsser, CRC Press, pp. 155 168 (1990)). The ITR sequences are about 145 bp in length. Preferably, substantially the entire sequences encoding the ITRs are used in the molecule, although some degree of minor modification of these sequences is permissible. The ability to modify these ITR sequences is within the skill of the art. (See, e.g., texts such as Sambrook et al, “Molecular Cloning. A Laboratory Manual”, 2d ed., Cold Spring Harbor Laboratory, N.Y. (1989); and K. Fisher et al., J. Virol., 70:520 532 (1996)). An example of such a molecule employed in the present invention is a “cis-acting” plasmid containing the transgene, in which the selected transgene sequence and associated regulatory elements are flanked by the 5′ and 3′ AAV ITR sequences. In one embodiment, the ITRs are from an AAV different than that supplying a capsid. In one embodiment, the ITR sequences from AAV2. A shortened version of the 5′ ITR, termed AITR, has been described in which the D-sequence and terminal resolution site (trs) are deleted. In other embodiments, the full-length AAV 5′ and 3′ ITRs are used. However, ITRs from other AAV sources may be selected. Where the source of the ITRs is from AAV2 and the AAV capsid is from another AAV source, the resulting vector may be termed pseudotyped. However, other configurations of these elements may be suitable.
In addition to the major elements identified above for the recombinant AAV vector, the vector also includes conventional control elements necessary which are operably linked to the transgene in a manner which permits its transcription, translation and/or expression in a cell transfected with the plasmid vector or infected with the virus produced by the invention. As used herein, “operably linked” sequences include both expression control sequences that are contiguous with the gene of interest and expression control sequences that act in trans or at a distance to control the gene of interest.
The regulatory control elements typically contain a promoter sequence as part of the expression control sequences, e.g., located between the selected 5′ ITR sequence and the coding sequence. Constitutive promoters, regulatable promoters [see, e.g., WO 2011/126808 and WO 2013/04943], tissue specific promoters, or a promoter responsive to physiologic cues may be used may be utilized in the vectors described herein. The promoter(s) can be selected from different sources, e.g., human cytomegalovirus (CMV) immediate-early enhancer/promoter, the SV40 early enhancer/promoter, the JC polymovirus promoter, myelin basic protein (MBP) or glial fibrillary acidic protein (GFAP) promoters, herpes simplex virus (HSV-1) latency associated promoter (LAP), rouse sarcoma virus (RSV) long terminal repeat (LTR) promoter, neuron-specific promoter (NSE), platelet derived growth factor (PDGF) promoter, hSYN, melanin-concentrating hormone (MCH) promoter, CBA, matrix metalloprotein promoter (MPP), and the chicken beta-actin promoter. In addition to a promoter a vector may contain one or more other appropriate transcription initiation, termination, enhancer sequences, efficient RNA processing signals such as splicing and polyadenylation (polyA) signals; sequences that stabilize cytoplasmic mRNA for example WPRE; sequences that enhance translation efficiency (i.e., Kozak consensus sequence); sequences that enhance protein stability; and when desired, sequences that enhance secretion of the encoded product. An example of a suitable enhancer is the CMV enhancer. Other suitable enhancers include those that are appropriate for desired target tissue indications. In one embodiment, the expression cassette comprises one or more expression enhancers. In one embodiment, the expression cassette contains two or more expression enhancers. These enhancers may be the same or may differ from one another. For example, an enhancer may include a CMV immediate early enhancer. This enhancer may be present in two copies which are located adjacent to one another. Alternatively, the dual copies of the enhancer may be separated by one or more sequences. In still another embodiment, the expression cassette further contains an intron, e.g, the chicken beta-actin intron. Other suitable introns include those known in the art, e.g., such as are described in WO 2011/126808. Examples of suitable polyA sequences include, e.g., SV40, SV50, bovine growth hormone (bGH), human growth hormone, and synthetic polyAs. Optionally, one or more sequences may be selected to stabilize mRNA. An example of such a sequence is a modified WPRE sequence, which may be engineered upstream of the polyA sequence and downstream of the coding sequence [see, e.g., MA Zanta-Boussif, et al, Gene Therapy (2009) 16: 605-619.
These rAAVs are particularly well suited to gene delivery for therapeutic purposes and for immunization, including inducing protective immunity. Further, the compositions of the invention may also be used for production of a desired gene product in vitro. For in vitro production, a desired product (e.g., a protein) may be obtained from a desired culture following transfection of host cells with a rAAV containing the molecule encoding the desired product and culturing the cell culture under conditions which permit expression. The expressed product may then be purified and isolated, as desired. Suitable techniques for transfection, cell culturing, purification, and isolation are known to those of skill in the art.
rAAV Vector Production
For use in producing an AAV viral vector (e.g., a recombinant (r) AAV), the expression cassettes can be carried on any suitable vector, e.g., a plasmid, which is delivered to a packaging host cell. The plasmids useful in this invention may be engineered such that they are suitable for replication and packaging in vitro in prokaryotic cells, insect cells, mammalian cells, among others. Suitable transfection techniques and packaging host cells are known and/or can be readily designed by one of skill in the art.
Methods for generating and isolating AAVs suitable for use as vectors are known in the art. See generally, e.g., Grieger & Samulski, 2005, “Adeno-associated virus as a gene therapy vector: Vector development, production and clinical applications,” Adv. Biochem. Engin/Biotechnol. 99: 119-145; Buning et al., 2008, “Recent developments in adeno-associated virus vector technology,” J Gene Med. 10:717-733; and the references cited below, each of which is incorporated herein by reference in its entirety. For packaging a gene into virions, the ITRs are the only AAV components required in cis in the same construct as the nucleic acid molecule containing the expression cassette(s). The cap and rep genes can be supplied in trans.
In one embodiment, the expression cassettes described herein are engineered into a genetic element (e.g., a shuttle plasmid) which transfers the immunoglobulin construct sequences carried thereon into a packaging host cell for production a viral vector. In one embodiment, the selected genetic element may be delivered to an AAV packaging cell by any suitable method, including transfection, electroporation, liposome delivery, membrane fusion techniques, high velocity DNA-coated pellets, viral infection and protoplast fusion. Stable AAV packaging cells can also be made. Alternatively, the expression cassettes may be used to generate a viral vector other than AAV, or for production of mixtures of antibodies in vitro. The methods used to make such constructs are known to those with skill in nucleic acid manipulation and include genetic engineering, recombinant engineering, and synthetic techniques. See, e.g., Molecular Cloning: A Laboratory Manual, ed. Green and Sambrook, Cold Spring Harbor Press, Cold Spring Harbor, N.Y. (2012).
The term “AAV intermediate” or “AAV vector intermediate” refers to an assembled rAAV capsid which lacks the desired genomic sequences packaged therein. These may also be termed an “empty” capsid. Such a capsid may contain no detectable genomic sequences of an expression cassette, or only partially packaged genomic sequences which are insufficient to achieve expression of the gene product. These empty capsids are non-functional to transfer the gene of interest to a host cell.
The recombinant adeno-associated virus (AAV) described herein may be generated using techniques which are known. See, e.g., WO 2003/042397; WO 2005/033321, WO 2006/110689; U.S. Pat. No. 7,588,772 B2. Such a method involves culturing a host cell which contains a nucleic acid sequence encoding an AAV capsid protein; a functional rep gene; an expression cassette composed of, at a minimum, AAV inverted terminal repeats (ITRs) and a transgene; and sufficient helper functions to permit packaging of the expression cassette into the AAV capsid protein. Methods of generating the capsid, coding sequences therefor, and methods for production of rAAV viral vectors have been described. See, e.g., Gao, et al, Proc. Natl. Acad. Sci. U.S.A. 100 (10), 6081-6086 (2003) and US 2013/0045186A1.
In one embodiment, a production cell culture useful for producing a recombinant rAAVhu68 is provided. Such a cell culture contains a nucleic acid which expresses the rAAVhu68 capsid protein in the host cell; a nucleic acid molecule suitable for packaging into the rAAVhu68 capsid, e.g., a vector genome which contains AAV ITRs and a non-AAV nucleic acid sequence encoding a gene product operably linked to sequences which direct expression of the product in a host cell; and sufficient AAV rep functions and adenovirus helper functions to permit packaging of the nucleic acid molecule into the recombinant AAVhu68 capsid. In one embodiment, the cell culture is composed of mammalian cells (e.g., human embryonic kidney 293 cells, among others) or insect cells (e.g., baculovirus).
Suitably, the rep functions are provided by an AAV which is from the same source as the ITRs which are present in the vector genome, or from another source which packages the vector genome into the AAV capsid (e.g., AAVhu68). In certain embodiments, the rep protein is from AAV2. However, in other embodiments In another embodiment, the rep protein is a heterologous rep protein other than AAVhu68rep, for example but not limited to, AAV1 rep protein, AAV2 rep protein, AAV3 rep protein, AAV4 rep protein, AAV5 rep protein, AAV6 rep protein, AAV7 rep protein, AAV8 rep protein; or rep 78, rep 68, rep 52, rep 40, rep68/78 and rep40/52; or a fragment thereof; or another source. Any of these AAVhu68 or mutant AAV capsid sequences may be under the control of exogenous regulatory control sequences which direct expression thereof in a production cell.
In one embodiment, cells are manufactured in a suitable cell culture (e.g., HEK 293) cells. Methods for manufacturing the gene therapy vectors described herein include methods well known in the art such as generation of plasmid DNA used for production of the gene therapy vectors, generation of the vectors, and purification of the vectors. In some embodiments, the gene therapy vector is an AAV vector and the plasmids generated are an AAV cis-plasmid encoding the AAV genome and the gene of interest, an AAV trans-plasmid containing AAV rep and cap genes, and an adenovirus helper plasmid. The vector generation process can include method steps such as initiation of cell culture, passage of cells, seeding of cells, transfection of cells with the plasmid DNA, post-transfection medium exchange to serum free medium, and the harvest of vector-containing cells and culture media. The harvested vector-containing cells and culture media are referred to herein as crude cell harvest. In yet another system, the gene therapy vectors are introduced into insect cells by infection with baculovirus-based vectors. For reviews on these production systems, see generally, e.g., Zhang et al., 2009, “Adenovirus-adeno-associated virus hybrid for large-scale recombinant adeno-associated virus production,” Human Gene Therapy 20:922-929, the contents of each of which is incorporated herein by reference in its entirety. Methods of making and using these and other AAV production systems are also described in the following U.S. patents, the contents of each of which is incorporated herein by reference in its entirety: U.S. Pat. Nos. 5,139,941; 5,741,683; 6,057,152; 6,204,059; 6,268,213; 6,491,907; 6,660,514; 6,951,753; 7,094,604; 7,172,893; 7,201,898; 7,229,823; and 7,439,065.
In certain embodiments, the manufacturing process for rAAV.hGALC involves transient transfection of HEK293 cells with plasmid DNA. A single batch or multiple batches are produced by PEI-mediated triple transfection of HEK293 cells in PALL iCELL is bioreactors. Harvested AAV material are purified sequentially by clarification, TFF, affinity chromatography, and anion exchange chromatography in disposable, closed bioprocessing systems where possible.
The crude cell harvest may thereafter be subject method steps such as concentration of the vector harvest, diafiltration of the vector harvest, microfluidization of the vector harvest, nuclease digestion of the vector harvest, filtration of microfluidized intermediate, crude purification by chromatography, crude purification by ultracentrifugation, buffer exchange by tangential flow filtration, and/or formulation and filtration to prepare bulk vector.
A two-step affinity chromatography purification at high salt concentration followed anion exchange resin chromatography are used to purify the vector drug product and to remove empty capsids. These methods are described in more detail in International Patent Application No. PCT/US2016/065970, filed Dec. 9, 2016 and its priority documents, U.S. Patent Application Nos. 62/322,071, filed Apr. 13, 2016 and 62/226,357, filed Dec. 11, 2015 and entitled “Scalable Purification Method for AAV9”, which is incorporated by reference herein. Purification methods for AAV8, International Patent Application No. PCT/US2016/065976, filed Dec. 9, 2016 and its priority documents U.S. Patent Application Nos. 62/322,098, filed Apr. 13, 2016 and 62/266,341, filed Dec. 11, 2015, and rh10, International Patent Application No. PCT/US16/66013, filed Dec. 9, 2016 and its priority documents, U.S. Patent Application No. 62/322,055, filed Apr. 13, 2016 and 62/266,347, entitled “Scalable Purification Method for AAVrh10”, also filed Dec. 11, 2015, and for AAV1, International Patent Application No. PCT/US2016/065974, filed Dec. 9, 2016 and its priority documents U.S. Patent Application Nos. 62/322,083, filed Apr. 13, 2016 and 62/26,351, for “Scalable Purification Method for AAV1”, filed Dec. 11, 2015, are all incorporated by reference herein.
To calculate empty and full particle content, VP3 band volumes for a selected sample (e.g., in examples herein an iodixanol gradient-purified preparation where # of GC=# of particles) are plotted against GC particles loaded. The resulting linear equation (y=mx+c) is used to calculate the number of particles in the band volumes of the test article peaks. The number of particles (pt) per 20 μL loaded is then multiplied by 50 to give particles (pt)/mL. Pt/mL divided by GC/mL gives the ratio of particles to genome copies (pt/GC). Pt/mL-GC/mL gives empty pt/mL. Empty pt/mL divided by pt/mL and x 100 gives the percentage of empty particles.
Generally, methods for assaying for empty capsids and AAV vector particles with packaged genomes have been known in the art. See, e.g., Grimm et al., Gene Therapy (1999) 6:1322-1330; Sommer et al., Molec. Ther. (2003) 7:122-128. To test for denatured capsid, the methods include subjecting the treated AAV stock to SDS-polyacrylamide gel electrophoresis, consisting of any gel capable of separating the three capsid proteins, for example, a gradient gel containing 3-8% Tris-acetate in the buffer, then running the gel until sample material is separated, and blotting the gel onto nylon or nitrocellulose membranes, preferably nylon. Anti-AAV capsid antibodies are then used as the primary antibodies that bind to denatured capsid proteins, preferably an anti-AAV capsid monoclonal antibody, most preferably the B1 anti-AAV-2 monoclonal antibody (Wobus et al., J. Vivol. (2000) 74:9281-9293). A secondary antibody is then used, one that binds to the primary antibody and contains a means for detecting binding with the primary antibody, more preferably an anti-IgG antibody containing a detection molecule covalently bound to it, most preferably a sheep anti-mouse IgG antibody covalently linked to horseradish peroxidase. A method for detecting binding is used to semi-quantitatively determine binding between the primary and secondary antibodies, preferably a detection method capable of detecting radioactive isotope emissions, electromagnetic radiation, or colorimetric changes, most preferably a chemiluminescence detection kit. For example, for SDS-PAGE, samples from column fractions can be taken and heated in SDS-PAGE loading buffer containing reducing agent (e.g., DTT), and capsid proteins were resolved on pre-cast gradient polyacrylamide gels (e.g., Novex). Silver staining may be performed using SilverXpress (Invitrogen, Calif.) according to the manufacturer's instructions or other suitable staining method, i.e. SYPRO ruby or coomassie stains. In one embodiment, the concentration of AAV vector genomes (vg) in column fractions can be measured by quantitative real time PCR (Q-PCR). Samples are diluted and digested with DNase I (or another suitable nuclease) to remove exogenous DNA. After inactivation of the nuclease, the samples are further diluted and amplified using primers and a TaqMan™ fluorogenic probe specific for the DNA sequence between the primers. The number of cycles required to reach a defined level of fluorescence (threshold cycle, Ct) is measured for each sample on an Applied Biosystems Prism 7700 Sequence Detection System. Plasmid DNA containing identical sequences to that contained in the AAV vector is employed to generate a standard curve in the Q-PCR reaction. The cycle threshold (Ct) values obtained from the samples are used to determine vector genome titer by normalizing it to the Ct value of the plasmid standard curve. End-point assays based on the digital PCR can also be used.
In one aspect, an optimized q-PCR method is used which utilizes a broad-spectrum serine protease, e.g., proteinase K (such as is commercially available from Qiagen). More particularly, the optimized qPCR genome titer assay is similar to a standard assay, except that after the DNase I digestion, samples are diluted with proteinase K buffer and treated with proteinase K followed by heat inactivation. Suitably samples are diluted with proteinase K buffer in an amount equal to the sample size. The proteinase K buffer may be concentrated to 2-fold or higher. Typically, proteinase K treatment is about 0.2 mg/mL, but may be varied from 0.1 mg/mL to about 1 mg/mL. The treatment step is generally conducted at about 55° C. for about 15 minutes, but may be performed at a lower temperature (e.g., about 37° C. to about 50° C.) over a longer time period (e.g., about 20 minutes to about 30 minutes), or a higher temperature (e.g., up to about 60° C.) for a shorter time period (e.g., about 5 to 10 minutes). Similarly, heat inactivation is generally at about 95° C. for about 15 minutes, but the temperature may be lowered (e.g., about 70 to about 90° C.) and the time extended (e.g., about 20 minutes to about 30 minutes). Samples are then diluted (e.g., 1000-fold) and subjected to TaqMan analysis as described in the standard assay.
Additionally, or alternatively, droplet digital PCR (ddPCR) may be used. For example, methods for determining single-stranded and self-complementary AAV vector genome titers by ddPCR have been described. See, e.g., M. Lock et al, Hu Gene Therapy Methods. 2014 April; 25(2):115-25. doi: 10.1089/hgtb.2013.131. Epub 2014 Feb. 14.
In brief, the method for separating rAAVhu68 particles having packaged genomic sequences from genome-deficient AAVhu68 intermediates involves subjecting a suspension comprising recombinant AAVhu68 viral particles and AAVhu689 capsid intermediates to fast performance liquid chromatography, wherein the AAVhu68 viral particles and AAVhu68 intermediates are bound to a strong anion exchange resin equilibrated at a pH of 10.2, and subjected to a salt gradient while monitoring eluate for ultraviolet absorbance at about 260 and about 280. Although less optimal for rAAV9hu68, the pH may be in the range of about 10.0 to 10.4. In this method, the AAVhu68 full capsids are collected from a fraction which is eluted when the ratio of A260/A280 reaches an inflection point. In one example, for the Affinity Chromatography step, the diafiltered product may be applied to a Capture Select™ Poros-AAV2/9 affinity resin (Life Technologies) that efficiently captures the AAV2/hu68 serotype. Under these ionic conditions, a significant percentage of residual cellular DNA and proteins flow through the column, while AAV particles are efficiently captured.
Provided herein are compositions containing at least one rAAV.hGALC stock (e.g., an rAAVhu68 stock or a mutant rAAV stock) and an optional carrier, excipient and/or preservative. An rAAV stock refers to a plurality of rAAV vectors which are the same, e.g., such as in the amounts described below in the discussion of concentrations and dosage units.
As used herein, “carrier” includes any and all solvents, dispersion media, vehicles, coatings, diluents, antibacterial and antifungal agents, isotonic and absorption delaying agents, buffers, carrier solutions, suspensions, colloids, and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Supplementary active ingredients can also be incorporated into the compositions. The phrase “pharmaceutically-acceptable” refers to molecular entities and compositions that do not produce an allergic or similar untoward reaction when administered to a host. Delivery vehicles such as liposomes, anocapsules, microparticles, microspheres, lipid particles, vesicles, and the like, may be used for the introduction of the compositions of the present invention into suitable host cells, in particular, the rAAV vector delivered vector genomes may be formulated for delivery either encapsulated in a lipid particle, a liposome, a vesicle, a nanosphere, or a nanoparticle or the like.
In one embodiment, a composition includes a final formulation suitable for delivery to a subject, e.g., is an aqueous liquid suspension buffered to a physiologically compatible pH and salt concentration. Optionally, one or more surfactants are present in the formulation. In another embodiment, the composition may be transported as a concentrate which is diluted for administration to a subject. In other embodiments, the composition may be lyophilized and reconstituted at the time of administration.
A suitable surfactant, or combination of surfactants, may be selected from among non-ionic surfactants that are nontoxic. In one embodiment, a difunctional block copolymer surfactant terminating in primary hydroxyl groups is selected, e.g., such as Pluronic® F68 [BASF], also known as Poloxamer 188, which has a neutral pH, has an average molecular weight of 8400. Other surfactants and other Poloxamers may be selected, i.e., nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)), SOLUTOL HS 15 (Macrogol-15 Hydroxystearate), LABRASOL (Polyoxy capryllic glyceride), polyoxy 10 oleyl ether, TWEEN (polyoxyethylene sorbitan fatty acid esters), ethanol and polyethylene glycol. In one embodiment, the formulation contains a poloxamer. These copolymers are commonly named with the letter “P” (for poloxamer) followed by three digits: the first two digits x 100 give the approximate molecular mass of the polyoxypropylene core, and the last digit x 10 gives the percentage polyoxyethylene content. In one embodiment Poloxamer 188 is selected. The surfactant may be present in an amount up to about 0.0005% to about 0.001% of the suspension.
The vectors are administered in sufficient amounts to transfect the cells and to provide sufficient levels of gene transfer and expression to provide a therapeutic benefit without undue adverse effects, or with medically acceptable physiological effects, which can be determined by those skilled in the medical arts. Conventional and pharmaceutically acceptable routes of administration include, but are not limited to, direct delivery to a desired organ (e.g., the liver (optionally via the hepatic artery), lung, heart, eye, kidney,), oral, inhalation, intranasal, intrathecal, intratracheal, intraarterial, intraocular, intravenous, intramuscular, subcutaneous, intradermal, and other parental routes of administration. Routes of administration may be combined, if desired.
Dosages of the viral vector depend primarily on factors such as the condition being treated, the age, weight and health of the patient, and may thus vary among patients. For example, a therapeutically effective human dosage of the viral vector is generally in the range of from about 25 to about 1000 microliters to about 100 mL of solution containing concentrations of from about 1×109 to 1×1016 genomes virus vector. The dosage is adjusted to balance the therapeutic benefit against any side effects and such dosages may vary depending upon the therapeutic application for which the recombinant vector is employed. The levels of expression of the transgene product can be monitored to determine the frequency of dosage resulting in viral vectors, preferably AAV vectors containing the minigene. Optionally, dosage regimens similar to those described for therapeutic purposes may be utilized for immunization using the compositions of the invention.
The replication-defective virus compositions can be formulated in dosage units to contain an amount of replication-defective virus that is in the range of about 1.0×109 GC to about 1.0×1016 GC (to treat an average subject of 70 kg in body weight) including all integers or fractional amounts within the range, and preferably 1.0×1012 GC to 1.0×1014 GC for a human patient. In one embodiment, the compositions are formulated to contain at least 1×109, 2×109, 3×109, 4×109, 5×109, 6×109, 7×109, 8×109, or 9×109 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1010, 2×1010, 3×1010, 4×1010, 5×1010, 6×1010, 7×1010, 8×1010, or 9×1010 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1011, 2×1011, 3×1011, 4×1011, 5×1011, 6×1011, 7×1011, 8×1011, or 9×1011 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1012, 2×1012, 3×1012, 4×1012, 5×1012, 6×1012, 7×1012, 8×1012, or 9×1012 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1013, 2×1013, 3×1013, 4×1013, 5×1013, 6×1013, 7×1013, 8×1013, or 9×1013 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1014, 2×1014, 3×1014, 4×1014, 5×1014, 6×1014, 7×1014, 8×1014, or 9×1014 GC per dose including all integers or fractional amounts within the range. In another embodiment, the compositions are formulated to contain at least 1×1015, 2×1015, 3×1015, 4×1015, 5×1015, 6×1015, 7×1015, 8×1015, or 9×1015 GC per dose including all integers or fractional amounts within the range. In one embodiment, for human application the dose can range from 1×1010 to about 1×1012 GC per dose including all integers or fractional amounts within the range. In one embodiment, for human application the dose can range from 1.4×1013 to about 4×1014 GC per dose including all integers or fractional amounts within the range.
These above doses may be administered in a variety of volumes of carrier, excipient or buffer formulation, ranging from about 25 to about 1000 microliters, or higher volumes, including all numbers within the range, depending on the size of the area to be treated, the viral titer used, the route of administration, and the desired effect of the method. In one embodiment, the volume of carrier, excipient or buffer is at least about 25 μL. In one embodiment, the volume is about 50 μL. In another embodiment, the volume is about 75 pt. In another embodiment, the volume is about 100 μL. In another embodiment, the volume is about 125 μL. In another embodiment, the volume is about 150 μL. In another embodiment, the volume is about 175 μL. In yet another embodiment, the volume is about 200 μL. In another embodiment, the volume is about 225 μL. In yet another embodiment, the volume is about 250 μL. In yet another embodiment, the volume is about 275 μL. In yet another embodiment, the volume is about 300 μL. In yet another embodiment, the volume is about 325 μL. In another embodiment, the volume is about 350 μL. In another embodiment, the volume is about 375 μL. In another embodiment, the volume is about 400 μL. In another embodiment, the volume is about 450 μL. In another embodiment, the volume is about 500 μL. In another embodiment, the volume is about 550 μL. In another embodiment, the volume is about 600 μL. In another embodiment, the volume is about 650 μL. In another embodiment, the volume is about 700 μL. In another embodiment, the volume is between about 700 and 1000 μL.
Therapeutically effective intrathecal/intracisternal doses of the rAAV.hGALC range from about 1×1011 to 7.0×1014 GC (flat doses)—the equivalent of 109 to 5×1010 GC/g brain mass of the patient. Alternatively, the following therapeutically effective flat doses can be administered to patients of the indicated age group:
In certain embodiments, the dose may be in the range of about 1×109 GC/g brain mass to about 1×1012 GC/g brain mass. In certain embodiments, the dose may be in the range of about 3×1010 GC/g brain mass to about 3×1011 GC/g brain mass. In certain embodiments, the dose may be in the range of about 5×1010 GC/g brain mass to about 1.85×1011 GC/g brain mass. For scaling between infants and adolescent/adults, brain mass is in some instances estimated to be about 600 g to about 800 g for a four to 12 month old; about 800 g to about 1000 g for a nine month to 18 month old, about 1000 g to about 1100 g for an 18 month old to a three year old; 1100 g to about 1300 g an adolescent or adult humans, or about 1300 g for an adult human.
In one embodiment, the viral constructs may be delivered in doses of from at least about least 1×109 GCs to about 1×1015, or about 1×1011 to 5×1012 GC. Suitable volumes for delivery of these doses and concentrations may be determined by one of skill in the art. For example, volumes of about 1 μL to 150 mL may be selected, with the higher volumes being selected for adults. Typically, for newborn infants a suitable volume is about 0.5 mL to about 10 mL, for older infants, about 0.5 mL to about 15 mL may be selected. For toddlers, a volume of about 0.5 mL to about 20 mL may be selected. For children, volumes of up to about 30 mL may be selected. For pre-teens and teens, volumes up to about 50 mL may be selected. In still other embodiments, a patient may receive an intrathecal administration in a volume of about 5 mL to about 15 mL are selected, or about 7.5 mL to about 10 mL. Other suitable volumes and dosages may be determined. The dosage is adjusted to balance the therapeutic benefit against any side effects and such dosages may vary depending upon the therapeutic application for which the recombinant vector is employed.
The above-described recombinant vectors may be delivered to host cells according to published methods. The rAAV, preferably suspended in a physiologically compatible carrier, may be administered to a human or non-human mammalian patient. In certain embodiments, for administration to a human patient, the rAAV is suitably suspended in an aqueous solution containing saline, a surfactant, and a physiologically compatible salt or mixture of salts. Suitably, the formulation is adjusted to a physiologically acceptable pH, e.g., in the range of pH 6 to 9, or pH 6.5 to 7.5, pH 7.0 to 7.7, or pH 7.2 to 7.8. As the pH of the cerebrospinal fluid is about 7.28 to about 7.32, for intrathecal delivery, a pH within this range may be desired; whereas for intravenous delivery, a pH of about 6.8 to about 7.2 may be desired. However, other pHs within the broadest ranges and these subranges may be selected for other routes of delivery.
In another embodiment, the composition includes a carrier, diluent, excipient and/or adjuvant. Suitable carriers may be readily selected by one of skill in the art in view of the indication for which the transfer virus is directed. For example, one suitable carrier includes saline, which may be formulated with a variety of buffering solutions (e.g., phosphate buffered saline). Other exemplary carriers include sterile saline, lactose, sucrose, calcium phosphate, gelatin, dextran, agar, pectin, peanut oil, sesame oil, and water. The buffer/carrier should include a component that prevents the rAAV, from sticking to the infusion tubing but does not interfere with the rAAV binding activity in vivo.
In one example, the formulation may contain, e.g., buffered saline solution comprising one or more of sodium chloride, sodium bicarbonate, dextrose, magnesium sulfate (e.g., magnesium sulfate.7H2O), potassium chloride, calcium chloride (e.g., calcium chloride.2H2O), dibasic sodium phosphate, and mixtures thereof, in water. Suitably, for intrathecal delivery, the osmolarity is within a range compatible with cerebrospinal fluid (e.g., about 275 to about 290); see, e.g., emedicine.medscape.com/article/2093316-overview. Optionally, for intrathecal delivery, a commercially available diluent may be used as a suspending agent, or in combination with another suspending agent and other optional excipients. See, e.g., Elliotts B® solution [Lukare Medical].
In certain embodiments, the formulation may contain a buffered saline aqueous solution not comprising sodium bicarbonate. Such a formulation may contain a buffered saline aqueous solution comprising one or more of sodium phosphate, sodium chloride, potassium chloride, calcium chloride, magnesium chloride and mixtures thereof, in water, such as a Harvard's buffer. The aqueous solution may further contain Kolliphor® P188, a poloxamer which is commercially available from BASF which was formerly sold under the trade name Lutrol® F68. The aqueous solution may have a pH of 7.2.
In other embodiments, the formulation may contain one or more permeation enhancers. Examples of suitable permeation enhancers may include, e.g., mannitol, sodium glycocholate, sodium taurocholate, sodium deoxycholate, sodium salicylate, sodium caprylate, sodium caprate, sodium lauryl sulfate, polyoxyethylene-9-laurel ether, or EDTA.
Optionally, the compositions of the invention may contain, in addition to the rAAV and carrier(s), other conventional pharmaceutical ingredients, such as preservatives, or chemical stabilizers. Suitable exemplary preservatives include chlorobutanol, potassium sorbate, sorbic acid, sulfur dioxide, propyl gallate, the parabens, ethyl vanillin, glycerin, phenol, and parachlorophenol. Suitable chemical stabilizers include gelatin and albumin.
The compositions according to the present invention may comprise a pharmaceutically acceptable carrier, such as defined above. Suitably, the compositions described herein comprise an effective amount of one or more AAV suspended in a pharmaceutically suitable carrier and/or admixed with suitable excipients designed for delivery to the subject via injection, osmotic pump, intrathecal catheter, or for delivery by another device or route. In one example, the composition is formulated for intrathecal delivery.
As used herein, the terms “intrathecal delivery” or “intrathecal administration” refer to a route of administration for drugs via an injection into the spinal canal, more specifically into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF). Intrathecal delivery may include lumbar puncture, intraventricular (including intracerebroventricular (ICV)), suboccipital/intracisternal, and/or C1-2 puncture. For example, material may be introduced for diffusion throughout the subarachnoid space by means of lumbar puncture. In another example, injection may be into the cisterna magna.
As used herein, the terms “intracisternal delivery” or “intracisternal administration” refer to a route of administration for drugs directly into the cerebrospinal fluid of the cisterna magna cerebellomedularis, more specifically via a suboccipital puncture or by direct injection into the cisterna magna or via permanently positioned tube.
As used herein, the term Computed Tomography (CT) refers to radiography in which a three-dimensional image of a body structure is constructed by computer from a series of plane cross-sectional images made along an axis.
The rAAV.GALC vectors and compositions provided herein are useful for correcting conditions associated with deficient levels of GALC enzymatic activity. In certain embodiments, the rAAV.GALC vectors and compositions provided herein are useful for treating dysfunction of peripheral nerves caused by deficiencies in GALC, useful in treating respiratory failure and/or motor function loss caused by GALC deficiencies, useful in treating Krabbe disease, and/or useful in treating symptoms associated with Krabbe disease in patients.
In certain embodiments, a composition comprising an effective amount of rAAV.hGALC is administered to a patient who is less than 6 months of age who has early infantile Krabbe disease (EIKD). In certain embodiments, the patient is less than 6 months of age and has GALC enzymatic deficiencies which are less severe than EIKD.
In certain embodiments, a composition comprising an effective amount of rAAV.hGALC is administered to a patient who is older than 6 months of age, e.g., 7 months to about 12 months who has late infantile Krabbe disease (LIKD). In certain embodiments, the patient is older than 6 months, or about 7 months to 12 months of age, and has GALC enzymatic deficiencies which are less severe than LIKD.
In certain embodiments, the patient is over a year old (e.g., from 13 months to 10 years) of age and has juvenile Krabbe disease (JKD). In certain embodiments, the patient is from 13 months to 10 years of age and has GALC enzymatic deficiencies which are less severe than JKD.
In certain embodiments, the patient is over 10 years of age (e.g., from over 10 years to 12 years, or from 10 years to 18 years or older) of age and has adolescent or adult onset Krabbe disease.
In any of the embodiments described above, the rAAV.hGALC therapy provided herein may be administered as a co-therapy with hematopoietic stem cell replacement therapy, bone marrow transplant (BMT), and/or substrate reduction therapy (SRT). In certain embodiments, the rAAV.hGALC therapy (e.g., EIKD) is followed by a co-therapy such as HSCT or BMT, or enzyme replacement therapy. In certain embodiments, the therapy results in rapid enzyme production following administration of the vector, including within 1 week post-treatment.
In certain embodiments, enzyme replacement therapy involves administration of the human GALC protein of SEQ ID NO: 10. In other embodiments, other hGALC protein variants (e.g., such as the canonical sequence identified herein, or an engineered protein), may be used in enzyme replacement therapy. Combinations of different hGALC proteins may be used in enzyme replacement therapy. In such embodiments, the hGALC protein may be produced in vitro using a suitable production system See, e.g., C. Lee et al, 2005 Oct. 1, Enzyme replacement therapy results in substantial improvements in early clinical phenotype in a mouse model of globoid cell leukodystrophy, FASEB journal, The FASEB Journal 19(11):1549-51, October 2005]. The hGALC proteins may be formulated for delivery (e.g., suspended in a physiologically compatible saline solution) by any suitable route including, but not limited to intravenous, intraperitoneal, or an intrathecal route. Suitable doses may range from 1 mg/kg to 20 mg/kg, or 5 mg/kg to 10 mg/kg and may be readministered once a week, or more or less frequently, as needed (e.g., once every other day, once every two weeks, etc). Using CSF administration of the hAAVhu68.GALC vector, GALC levels in brain and serum can be supraphysiological without toxicity and improved neuromotor function and myelination in CNS and PNS may be observed. When newborn CSF administration is followed by bone marrow transplant in a postnatal conditioned animal model, survival can be extended (e.g., to >300 days) in the absence of overt signs. In a presymptomatic Krabbe patient, a single cisterna magna injection of AAV.cGALC may provide phenotypic correction, survival increase, nerve conduction normalization, and/or improved brain MRI.
In certain embodiments, the rAAV.hGALC therapy is provided following HSCT or BMT (e.g., LIKD or JKD). However, in certain embodiments, the rAAV.hGALC provides sufficient GALC levels that HSCT or BMT are not required.
The goal of treatment is to functionally replace the patient's defective GALC via rAAV-based CNS- and PNS-directed gene therapy. Efficacy of the therapy for EIKD or LIKD patients can be measured by assessing improvement in one or more of the symptoms of EIKD or LIKD: crying and irritability, spasticity, fisted hands, loss of smiling, poor head control and feeding difficulties; mental and motor deterioration, hyper or hypotonicity, seizures, blindness, deafness, and increased survival (for EIKD, without treatment, death typically occurs before the age of 2; for LIKD, survival may increase to 3-5 years of age). Additionally, for these and other Krabbe patients, efficacy of treatment may be assessed by: a decrease in dysmyelination and demyelination affecting both peripheral nerves and CNS white matter (deep cerebral white matter and dentate/cerebellar white matter) which can be monitored via imaging (e.g., magnetic resonance imaging (MRI)); a decrease in abnormal nerve conduction velocity (NCV) and/or brainstem auditory evoked potentials (BAEPs); increased levels of GALC may be observed in cerebrospinal fluid and/or plasma; and/or decreased accumulation of psychosine.
A composition comprising a recombinant adeno-associated virus (rAAV) is provided which comprises an AAV capsid which targets cells in the central nervous system and which has packaged therein a vector genome comprising a galactosylceramidase coding sequence encoding a mature galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 under the control of regulatory sequences which direct expression of the protein, said vector genome further comprising AAV inverted terminal repeats necessary for packaging the vector genome in an AAV capsid.
In certain embodiments, a composition useful for treating Krabbe disease is provided which comprises rAAVhu68 having a vector genome of CB7.CI.hGALC.rBG. In one embodiment, the vector genome has the coding sequence of (SEQ ID NO: 19).
In certain embodiments, use of a composition is provided in a method for correcting dysfunction of peripheral nerves caused by a GALC deficiency and/or a method for treating respiratory failure and motor function loss caused by a GALC deficiency. In certain embodiments, the method comprises administering a composition comprising a stock of recombinant adeno-associated virus (rAAV) which comprises: (a) an AAV capsid which targets cells in the central nervous system and which has a vector genome of (b) packaged therein; and (b) a vector genome comprising a galactosylceramidase coding sequence encoding a mature galactosylceramidase protein having the amino acid sequence in SEQ ID NO: 10 under the control of regulatory sequences which direct expression of the protein, wherein the vector genome further comprises AAV inverted terminal repeats necessary for packaging the vector genome in an AAV capsid.
In certain embodiments, a rAAV.hGALC composition as provided herein is delivered intrathecally for treatment of a patient with early infantile Krabbe disease. In certain embodiments, a composition as provided herein is delivered intrathecally for treatment of a patient with late infantile Krabbe disease (LIKD). In certain embodiments, a rAAV.hGALC composition as provided herein is delivered intrathecally for treatment of a patient with Juvenile Krabbe disease (JKD). In certain embodiments, rAAV.hGALC composition as provided herein is delivered intrathecally for treatment of a patient with adolescent or adult onset Krabbe disease. In certain embodiments, the rAAV.hGALC composition is administered as a co-therapy to hematopoietic stem cell transplant (HSCT), bone marrow transplant, and/or substrate reduction therapy. In certain embodiments, the rAAV.hGALC composition is administered as a single dose via a computed tomography-(CT-) guided sub-occipital injection into the cisterna magna (intra-cisterna magna).
Administration of rAAV.hGALC stabilizes disease progression as measured by survival, preventing loss of developmental and motor milestone potentially supporting acquisition of new milestones, onset and frequency of seizures. Thus, in certain embodiments, methods for monitoring treatment are provided wherein endpoints are measured at, for example, 30 days, 90 days and/or 6 months, and then, for example, every 6 months during the 2-year short-term follow-up period. In certain embodiments, measurement frequency decreases to once every 12 months during the long-term extension. Given the severity of disease in the target population, subjects may have achieved motor skills by enrollment, developed and subsequently lost other motor milestones, or not yet shown signs of motor milestone development. Assessments therefore track age-at-achievement and age-at-loss for all milestones. In certain embodiments, milestones include, for example, one or more of sitting without support, hand-and-knees crawling, standing with assistance, walking with assistance, standing alone, and/or walking alone. In certain embodiments, treatment results in a delayed onset of seizure activity and/or a decrease in the frequency of seizure events.
In certain embodiments, methods of monitoring treatment in a subject uses clinical scales to quantify the effects of treatment on development and changes in adaptive behaviors, cognition, language, motor function, and/or health-related quality of life. Scales and domains include, for example, the Bayley Scales of Infant and Toddler Development (assesses development of infant and toddlers across five domains: cognitive, language, motor, social-emotional, and adaptive behavior), the Vineland Adaptive Behavior Scales (Edition III) (assesses adaptive behavior from birth through adulthood (0-90 years) across five domains: communication, daily living skills, socialization, motor skills, and maladaptive behavior), the Peabody Developmental Motor Scales-Second Edition (measures interrelated motor function from birth to children five years of age; assessments focus on six domains: reflexes, stationary, locomotion, object manipulation, grasping, and visual-motor integration), the Infant Toddler Quality of Life Questionnaire (ITQOL) (parent-reported measure of health-related quality of life designed for infants 2 months of age up to toddlers 5 years of age), and the Mullen Scales of Early Learning (assesses language, motor, and perceptual abilities in infants and toddlers up to 68 months of age). In certain embodiments, the effects of treatments are monitored or measured by evaluating changes in myelination, functional outcomes related to myelination, and potential disease biomarkers. In certain embodiments, central and peripheral demyelination slow or cease in progression following treatment of a subject. Central demyelination may be tracked by diffusion-tensor magnetic resonance imaging (DT-MRI) anisotropy measurements of white matter regions and fiber tracking of corticospinal motors tracts, changes in which are indicators of disease state and progression. Peripheral demyelination may be measured indirectly via nerve conduction velocity (NCV) studies on the motor nerves (deep peroneal, tibial, and ulnar nerves) and sensory nerves (sural, and median nerves) to monitor for fluctuations indicative of a change in biologically active myelin (i.e., F-wave and distal latencies, amplitude or presence or absence of a response).
In certain embodiments, a method of monitoring treatment following rAAV.hGALC administration is provided wherein the subject is evaluated for a delay in vision loss or absence of vision loss for those subjects that have not developed significant vision loss prior to treatment. Measurement of visual evoked potentials (VEPs) is therefore used to objectively measure responses to visual stimuli as an indicator of central visual impairment or loss. In certain embodiments, the subject is monitored for hearing loss following treatment using, for example, brainstem auditory evoked response (BAER) testing. In certain embodiments, a method of monitoring treatment following rAAV.hGALC administration is provided wherein a subject's psychosine levels are measured.
It is to be noted that the term “a” or “an” refers to one or more. As such, the terms “a” (or “an”), “one or more”, and “at least one” are used interchangeably herein.
The words “comprise”, “comprises”, “comprising”, “containing”, and “including” are to be interpreted inclusively rather than exclusively. The words “consist”, “consisting”, and its variants, are to be interpreted exclusively, rather than inclusively. While various embodiments in the specification are presented using “comprising” language, under other circumstances, a related embodiment is also intended to be interpreted and described using “consisting of” or “consisting essentially of” language.
As used herein, the term “about” means a variability of 10% (±10%) from the reference given, unless otherwise specified.
As used herein, “disease”, “disorder”, and “condition” are used interchangeably, to indicate an abnormal state in a subject.
The term “expression” is used herein in its broadest meaning and comprises the production of RNA or of RNA and protein. With respect to RNA, the term “expression” or “translation” relates in particular to the production of peptides or proteins. Expression may be transient or may be stable.
As used herein, an “expression cassette” refers to a nucleic acid molecule which comprises a coding sequence, promoter, and may include other regulatory sequences therefor. In certain embodiments, a vector genome may contain two or more expression cassettes. In other embodiments, the term “transgene” may be used interchangeably with “expression cassette”. Typically, such an expression cassette for generating a viral vector contains the coding sequence for the gene product described herein flanked by packaging signals of the viral genome and other expression control sequences such as those described herein.
The abbreviation “sc” refers to self-complementary. “Self-complementary AAV” refers a construct in which a coding region carried by a recombinant AAV nucleic acid sequence has been designed to form an intra-molecular double-stranded DNA template. Upon infection, rather than waiting for cell mediated synthesis of the second strand, the two complementary halves of scAAV will associate to form one double stranded DNA (dsDNA) unit that is ready for immediate replication and transcription. See, e.g., D M McCarty et al, “Self-complementary recombinant adeno-associated virus (scAAV) vectors promote efficient transduction independently of DNA synthesis”, Gene Therapy, (August 2001), Vol 8, Number 16, Pages 1248-1254. Self-complementary AAVs are described in, e.g., U.S. Pat. Nos. 6,596,535; 7,125,717; and 7,456,683, each of which is incorporated herein by reference in its entirety.
The term “heterologous” when used with reference to a protein or a nucleic acid indicates that the protein or the nucleic acid comprises two or more sequences or subsequences which are not found in the same relationship to each other in nature. For instance, the nucleic acid is typically recombinantly produced, having two or more sequences from unrelated genes arranged to make a new functional nucleic acid. For example, in one embodiment, the nucleic acid has a promoter from one gene arranged to direct the expression of a coding sequence from a different gene. Thus, with reference to the coding sequence, the promoter is heterologous.
A “replication-defective virus” or “viral vector” refers to a synthetic or artificial viral particle in which an expression cassette containing a gene of interest is packaged in a viral capsid or envelope, where any viral genomic sequences also packaged within the viral capsid or envelope are replication-deficient; i.e., they cannot generate progeny virions but retain the ability to infect target cells. In one embodiment, the genome of the viral vector does not include genes encoding the enzymes required to replicate (the genome can be engineered to be “gutless”—containing only the gene of interest flanked by the signals required for amplification and packaging of the artificial genome), but these genes may be supplied during production. Therefore, it is deemed safe for use in gene therapy since replication and infection by progeny virions cannot occur except in the presence of the viral enzyme required for replication.
In many instances, rAAV particles are referred to as DNase resistant. However, in addition to this endonuclease (DNase), other endo- and exo-nucleases may also be used in the purification steps described herein, to remove contaminating nucleic acids. Such nucleases may be selected to degrade single stranded DNA and/or double-stranded DNA, and RNA. Such steps may contain a single nuclease, or mixtures of nucleases directed to different targets, and may be endonucleases or exonucleases.
The term “nuclease-resistant” indicates that the AAV capsid has fully assembled around the expression cassette which is designed to deliver a gene to a host cell and protects these packaged genomic sequences from degradation (digestion) during nuclease incubation steps designed to remove contaminating nucleic acids which may be present from the production process.
As used herein, an “effective amount” refers to the amount of the rAAV composition which delivers and expresses in the target cells an amount of the gene product from the vector genome. An effective amount may be determined based on an animal model, rather than a human patient. Examples of a suitable murine model are described herein.
Unless defined otherwise in this specification, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art and by reference to published texts, which provide one skilled in the art with a general guide to many of the terms used in the present application.
The following examples are illustrative only and are not intended to limit the present invention.
rAAVhu68.hGALC is an AAV that carries an engineered sequence encoding a human GALC. The AAVhu68 capsid of rAAVhu68.hGALC is 99% identical at the amino acid level to AAV9. The two amino acids that differ between the AAV9 [SEQ ID NO: 4] and AAVhu68 capsids [SEQ ID NO: 2] are located in the VP1 (67 and 157) and VP2 (157) regions of the capsid and are identifies in
rAAVhu68.hGALC is produced by triple plasmid transfection of HEK293 cells with an AAV cis plasmid encoding the transgene cassette flanked by AAV ITRs, the AAV trans plasmid encoding the AAV2 rep and AAVhu68 cap genes (pAAV2/hu68.KanR), and the helper adenovirus plasmid (pAdAF6.KanR).
A. AAV Vector Genome Plasmid Sequence Elements
A linear map of the vector genome is shown in
Inverted Terminal Repeat (ITR): The ITRs are identical, reverse complementary sequences derived from AAV2 (130 bp, GenBank: NC_001401) that flank all components of the vector genome. The ITRs function as both the origin of vector DNA replication and the packaging signal for the vector genome when AAV and adenovirus helper functions are provided in trans. As such, the ITR sequences represent the only cis sequences required for vector genome replication and packaging.
Human Cytomegalovirus Immediate-Early Enhancer (CMV IE): This enhancer sequence obtained from human-derived CMV (382 bp, GenBank: K03104.1) increases expression of downstream transgenes.
Chicken β-Actin Promoter (BA): This ubiquitous promoter (282 bp, GenBank: X00182.1) was selected to drive transgene expression in any CNS cell type.
Chimeric Intron (CI): The hybrid intron consists of a chicken β-actin splice donor (973 bp, GenBank: X00182.1) and rabbit β-globin splice acceptor element. The intron is transcribed, but removed from the mature mRNA by splicing, bringing together the sequences on either side of it. The presence of an intron in an expression cassette has been shown to facilitate the transport of mRNA from the nucleus to the cytoplasm, thus enhancing the accumulation of the steady level of mRNA for translation. This is a common feature in gene vectors intended for increased levels of gene expression.
Coding sequence: An engineered cDNA of the human GALC gene encodes human galactosylceramidase protein, which is a lysosomal enzyme responsible for the hydrolysis and degradation of myelin galactolipids (2055 bp; 685 amino acids [aa], GenBank: EAW81361.1).
Rabbit β-Globin Polyadenylation Signal (rBG PolyA): The rBG PolyA signal (127 bp, GenBank: V00882.1) facilitates efficient polyadenylation of the transgene mRNA in cis. This element functions as a signal for transcriptional termination, a specific cleavage event at the 3′ end of the nascent transcript and the addition of a long polyadenyl tail.
B. Trans Plasmid: pAAV2/1.KanR (p0068)
The AAV2/hu68 trans plasmid pAAV2/hu68.KanR (p0068) is presented in
The AAV2/hu68 trans plasmid is pAAV2/hu68.KanR (p0068). The pAAV2/hu68.KanR plasmid is 8030 bp in length and encodes four wild type AAV2 replicase (Rep) proteins required for the replication and packaging of the AAV vector genome. The pAAV2/hu68.KanR plasmid also encodes three WT AAVhu68 virion protein capsid (Cap) proteins, which assemble into a virion shell of the AAV serotype hu68 to house the AAV vector genome.
To create the pAAV2/hu68.KanR trans plasmid, the AAV9 cap gene from plasmid pAAV2/9n (p0061-2) (which encodes the wild type AAV2 rep and AAV9 cap genes on a plasmid backbone derived from the pBluescript KS vector) was removed and replaced with the AAVhu68 cap gene. The ampicillin resistance (AmpR) gene was also replaced with the kanamycin resistance (KanR) gene, yielding pAAV2/hu68.KanR (p0068). This cloning strategy relocated the AAV p5 promoter sequence (which normally drives rep expression) from the 5′ end of rep to the 3′ end of cap, leaving behind a truncated p5 promoter upstream of rep. This truncated promoter serves to down-regulate expression of rep and, consequently, maximize vector production (
All component parts of the plasmid have been verified by direct sequencing.
C. Adenovirus Helper Plasmid: pAdDeltaF6(KanR)
The adenovirus helper plasmid pAdDeltaF6(KanR) is presented in (
Plasmid pAdDeltaF6(KanR) is 15,770 bp in size. The plasmid contains the regions of adenovirus genome that are important for AAV replication; namely, E2A, E4, and VA RNA (the adenovirus El functions are provided by the HEK293 cells). However, the plasmid does not contain other adenovirus replication or structural genes. The plasmid does not contain the cis elements critical for replication, such as the adenoviral ITRs; therefore, no infectious adenovirus is expected to be generated. The plasmid was derived from an El, E3-deleted molecular clone of Ad5 (pBHG10, a pBR322-based plasmid). Deletions were introduced into Ad5 to eliminate expression of unnecessary adenovirus genes and reduce the amount of adenovirus DNA from 32 kb to 12 kb (
The studies described below used the Twitcher mouse model to establish the potential for delivery of an rAAVhu68 vector (
The Twitcher mouse is a naturally occurring inbred model of Krabbe disease that was identified as a spontaneous mutation at the Jackson Laboratory in 1976 (Kobayashi T., et al. (1980) Brain Research. 202(2):479-483). Affected mice are homozygous for the twitcher loss-of-function allele (twi), which consists of a G to A mutation in the Galc gene. This mutation causes an early stop codon (W339X). The truncated GALC protein has residual enzymatic activity close to 0%, which is similar to GALC activity levels observed in patients with the infantile form of Krabbe disease. Heterozygous carrier mice (twi/+) are phenotypically normal.
The progression of disease in the Twitcher mouse is well-documented (
Infantile Krabbe patients exhibit similar clinical features as the Twitcher mice. Thus, the Twitcher mouse model is adequate to assess the efficacy (rescue of enzyme activity to improve survival, motor function, and brain and nerve pathology) of rAAVhu68.hGALC to support an infantile Krabbe indication. Studies using the Twitcher mouse, described below, demonstrated the efficacy of rAAVhu68.hGALC to express active GALC enzyme in the relevant tissues, rescue survival, ameliorate motor function, and ameliorate CNS and PNS histopathology after a single ICV administration (the most efficient route of administration in mouse models where ICM is not technically feasible).
The aim of this study was to establish the optimal ROA, capsid serotype, and dose range for achieving maximal efficacy in the Twitcher mouse model. Presymptomatic newborn mice were selected for these studies in order to maximize the change of observing disease rescue.
To establish the optimal ROA, the IV route via injection into the temporal vein was compared to the ICV route because both routes can transduce the CNS and PNS in newborn animals. Presymptomatic Twitcher mice (twi/twi) were administered rAAVhu68.hGALC either IV at a dose of 1.00×1011 GC or ICV at a 5-fold lower dose of 2.00×1010 GC on PND 0. The IV dose was selected because it corresponds to 1.00×1014 GC/kg, a high dose needed to achieve CNS transduction, and a 5-fold lower ICV dose was selected because direct administration into the CSF facilitates CNS transduction at lower doses. As a control, presymptomic age-matched Twitcher mice were injected ICV with vehicle (PBS). Animals were euthanized upon reaching a humane endpoint defined by weight loss >20% of maximal body weight and/or hind leg paralysis, and survival was recorded. IV administration of rAAVhu68.hGALC at the higher dose (1.00×1011 GC) provided some survival benefit compared to the untreated controls. However, compared to IV administration, ICV-administered rAAVhu68.hGALC at a 5-fold lower dose (2.00×1010 GC) conferred a superior survival benefit (
To identify the best AAV capsid for nervous system delivery of a vector genome encoding human GALC, four different AAV capsids were tested. The capsids included AAV serotype 3b (AAV3b), AAV serotype 5 (AAV5), AAV serotype 1 (AAV1), and AAV serotype hu68 (rAAVhu68.hGALC). Each AAV vector was administered ICV at a dose of 2.00×1010 GC, which was the low dose and ROA previously established to effectively prolong survival in presymptomatic Twitcher mice while allowing a short study duration (
To determine the dose range, rAAVhu68.hGALC was ICV-administered at a dose of 2.00×1010 GC, 5.00×1010 GC, or 1.00×1011 GC to newborn presymptomatic Twitcher mice on PND 0. As controls, age-matched presymptomatic Twitcher (twi/twi) mice and unaffected heterozygotes (twi/+) and wild type mice were ICV-administered vehicle (PBS) on PND 0.
At PND 35, the mobility and coordination of the mice were assessed using a rod assay (
Following the rotarod assay, survival was tracked for all treatment groups. A dose-dependent increase in survival was observed for Twitcher (twi/twi) mice administered rAAVhu68.hGALC presymptomatically on PND 0 compared to the vehicle-treated Twitcher (twi/twi) controls. The longest median survival (130 days) was observed for mice administered the highest rAAVhu68.hGALC dose of 1.00×1011 GC (
Cumulatively, these POC experiments to identify the optimal ROA, capsid, and dose range demonstrate the efficacy of rAAVhu68.hGALC at preserving neuromotor function and prolonging survival if administered prior to symptom onset in Twitcher mice.
The aim of this study was to examine the efficacy of rAAVhu68.hGALC when administered during the early phase of disease pathology prior to the onset of behavioral symptoms (PND 12; referred to as “early-symptomatic”) or during a later phase of disease pathology when mice display behavioral symptoms (PND 21; referred to as “later-symptomatic”) because we wanted to recapitulate a context similar to patients enrolled after symptom onset. Moreover, PND 0 mice have a brain maturation equivalent to a pre-term fetus, whereas PND 12 and PND 21 translate to a 2-month-old and a 9-month-old, respectively (www.translatingtime.org), which more closely recapitulates the intended infantile population for the FIH.
Early-symptomatic Twitcher mice were ICV-administered rAAVhu68.hGALC at a dose of either 1.00×1011 GC or 2.00×1011 GC on PND 12, while another cohort of later-symptomatic Twitcher mice were ICV-administered rAAVhu68.hGALC at a higher dose of 2.00×1011 GC on PND 21. The lower dose of 1.00×1011 GC was selected for administration because it was found to be the most effective dose at increasing survival of Twitcher mice (described above). A higher rAAVhu68.hGALC dose of 2.00×1011 GC was also utilized for the treatment of mice on PND 21 because it was hypothesized that a higher dose might be needed for mice with more severe demyelination. As controls, early-symptomatic Twitcher mice (twi/twi) and unaffected heterozygotes (twi/+) were ICV-administered vehicle only (PBS) on PND 12, and historic data from Study 1 were used to compare with Twitcher mice (twi/twi) administered 1.11×1011 GC at PND 0.
At PND 35, the mobility and coordination of the mice were assessed using the rotarod assay, which is a time point at which Twitcher mice (twi/twi) display measurable motor deficits. The rotarod assay revealed partial rescue of motor and coordination when rAAVhu68.hGALC was administered to pre-symptomatic Twitcher mice on PND 0 at a dose of 1.00×1011 GC (p<0.01) or to early-symptomatic Twitcher mice on PND 12 at a dose of either 1.00×1011 GC (p<0.001) or 2.00×1011 GC (p<0.01). No significant rescue of motor and coordination was observed when a rAAVhu68.hGALC dose of 2.00×1011 GC was administered to later-symptomatic Twitcher mice on PND 21 (
Following the rotarod assay, survival was tracked for all treatment groups. Compared to vehicle-treated Twitcher controls, longer survival was observed following rAAVhu68.hGALC administration in both early-symptomatic Twitcher mice on PND 12 and later-symptomatic Twitcher mice on PND 21. However, maximal survival was obtained when early-symptomatic Twitcher mice were administered rAAVhu68.hGALC at the high dose of 2.00×1011 GC on PND 12 (
Cumulatively, improvements in survival and neuromotor function of Twitcher mice suggested that rAAVhu68.hGALC may be more efficacious if administered at earlier stages of disease.
The aim of this study was to assess pharmacology, functional, and histopathology readouts after rAAVhu68.hGALC administration. Because previous studies sacrificed animals at a humane endpoint in order to faciliate survival anlyses, this precluded the collection of pharmacology and histology readouts at age-matched time points in Twitcher mice and vehicle-treated controls. Therefore, this study examined these endpoints.
Early-symptomatic Twitcher mice (twi/twi) were ICV-administered rAAVhu68.hGALC at a dose of 2.00×1011 GC on PND 12. Age-matched unaffected Twitcher heterozygotes (twi/+) and wild-type mice were ICV-adminstered PBS as controls on PND 12. A rAAVhu68.hGALC dose of 2.00×1011 GC was selected for POC to achieve maximal efficacy, and PND 12 was selected as the day of dosing because it is shortly after the onset of PNS demyelination in an animal with brain maturation equivalent to a 2-month-old infant (www.translatingtime.org), which mirrors the intended infantile population for the FIH trial.
Beginning on PND 22, all mice were monitored daily for clinical signs. PND 22 was selected as the first time point for this assessment because this is one of the earliest days at which behavior phenotypes are observable in Twitcher mice. Clinical signs were scored using an unpublished assessment of clasping ability, gait, tremor, kyphosis, and fur quality as detailed in Table 1. These measures effectively assess the clinical status of Twitcher mice based upon the symptoms they typically present. Scores above 0 indicate clinical deterioration.
Using this assessment, early-symptomatic Twitcher mice (twi/twi) administered rAAVhu68.hGALC on PND 12 displayed clinical scores close to 0, which was comparable to the scores of wild-type and unaffected Twitcher heterozygotes (twi/+). In constrast, the age-matched vehicle-treated Twitcher (twi/twi) mice displayed higher assessment scores over most of the time course, indicating clinical deterioration (
As a complementary functional assay, the rotarod test was performed on PND 35 to evaluate neuromotor phenotypes. Early-symptomatic Twitcher mice (twi/twi) administered rAAVhu68.hGALC on PND 12 displayed fall latencies comparable to those of the wild-type and unaffected Twitcher heterozygotes (twi/+), while the age-matched vehicle-treated Twitcher mice (twi/twi) displayed significantly shorter fall latencies (p<0.05), indicating deterioration of neuromotor function (
To determine whether the observed benefits of rAAVhu68.hGALC administration on functional endpoints correlated with histologic improvements, all mice were necropsied on PND 40, and the sciatic nerve of the hind limb was examined histologically. PND 40 was selected as the necropsy time point because it is the approximate age when untreated or vehicle-treated Twitcher mice reach humane endpoint and it is a time point at which the neuropathology is most severe. The sciatic nerve was selected for histology because it peripheral nerves are more affected by demyelination in Twitcher mice compared to the CNS. Furthermore, lack of correction of the PNS by HSCT in patients remains a major unmet neet in infantile patients, so an examination of the effect of rAAVhu68.hGALC administration on the PNS is of interest.
Sections of the sciatic nerves were processed for visualization of myelin (dark staining) and globoid cells (light staining) (
Finally, samples of brain, liver, and serum were obtained from wild type and Twitcher mice (twi/twi) on the day of necropsy (PND 40) to quantify activity levels of the transgene product, GALC. GALC was quantified using a fluorophore-based GALC activity assay to confirm that following rAAVhu68.hGALC administration, the AAV vector was transduced and a functional enzyme was expressed. Wild type animals were used as the control for this assay, and Twitcher heterozygotes (twi/+) were excluded because GALC activity levels are reduced in those mice despite having no observable phenotype. The brain was examined because the nervous system is the target tissue for GALC delivery, and the liver and serum were examined to assess transduction in peripherial organ systems.
Twenty-eight days after ICV administration of rAAVhu68.hGALC at a dose of 2.00×1011 GC, supraphysiologic levels of GALC activity were observed in the brain, liver, and serum of Twitcher (twi/twi), which were higher than the levels observed in the same tissues of vehicle-treated Twitcher (twi/twi) mice and wild type controls (
Cumulatively, the data demonstrated that the administration of rAAVhu68.hGALC to early-symptomatic Twitcher mice results in supraphysiologic levels of GALC activity that correlates with less severe clinical symptoms, neuromotor dysfunction, PNS demyelination, and globoid cell neuropathology.
Effect of Bone Marrow Transplant in Combination with rAAVhu68.hGALC Administration
This study investigated the potential benefit of a dual therapy of rAAVhu68.hGALC and bone marrow transplant (BMT). We investigated this combination therapy because of the prominent neuroinflammatory component of Krabbe disease. In theory, there is a synergistic effect because the HSCT provides an additional source of GALC enzyme in the CNS (from macrophage/microglial cells derived from the transplanted cells and rAAVhu68.hGALC-transduced neurons), while rAAVhu68.hGALC provides correction to the PNS, which is not affected by HSCT. Moreover, different combination treatment designs were examined in this study to assess whether rAAVhu68.hGALC might be efficacious in 1) patients who receive a HSCT first through NBS programs followed by gene therapy and/or 2) patients who receive gene therapy first followed by HSCT, if eligible.
The combination therapy study is summarized in Table 2.
The rAAVhu68.hGALC dose of 1.00×1011 GC was utilized because we anticipate a better response due to the combination therapy, which permits a lower dose of rAAVhu68.hGALC than was used in previous studies of rAAVhu68.hGALC monotherapy. Efficacy of rAAVhu68.hGALC is assessed in terms of survival, body weight, and neurologic observations (e.g., presence of tremor and abnormal clasping reflex).
The survival data for Groups 1-3 are shown in
Cumulatively, these data suggest that combining rAAVhu68.hGALC treatment with a subsequent BMT may provide more efficacy than each treatment alone in the murine model of Krabbe disease.
The MED study is performed in the Twitcher mouse using the toxicological vector lot manufactured for a nonhuman primate pharmacology-toxicology study. The study includes at least two timepoints and evaluates four dose levels to determine the MED, pharmacology, and histopathology (efficacy and safety). The dose levels were selected based on the pilot dose range study and the maximal feasible dose when scaled to humans. Animals are injected ICV at PND12 to mimic early symptomatic patients. Some of the animals are sacrificed one-month post-injection (when vehicle treated reach humane endpoint) to obtain pharmacological and efficacy readouts compared to age-matched controls (similar design than study 3). The remaining mice are followed until a humane endpoint to evaluate the effect of treatment on survival. Personnel doing the in-life evaluation (body weight, clinical scoring and rotarod assay) are blinded to the mice treatment and genotype.
MED is determined upon analysis of survival benefit, clinical scoring, body weight, neuromotor function using the rotarod assay, GALC activity levels in target organs, and correction of neuropathology in the CNS and PNS (i.e., improved myelination, decreased globoid cells infiltration).
The study design and study schedule are presented below in Table 3 and Table 4.
While an informative disease model, the Twitcher mouse does have some limitations. The mice display only mild CNS involvement, which is distinct from infantile Krabbe patients, who present with more severe CNS features of demyelination of brain atrophy. Furthermore, the small size of the mouse poses experimental challenges. The ICV route must be used in mice because their small size makes it difficult to reliably inject AAV vector via the intended clinical route (ICM). Sufficient quantities of serial samples of CSF and blood also cannot be obtained from mice for all of the desired pharmacological assays. Treatment with rAAVhu68.GALC was therefore evaluated in a larger animal, the canine model of Krabbe disease, which can overcome these technical constraints and confirm the scalability of our therapeutic approach.
Like the Twitcher mouse, the Krabbe dog is a naturally occurring autosomal recessive disease model deriving from a spontaneous A to C mutation in the GALC gene that causes a missense mutation (Y158S). The mutant GALC protein has residual enzymatic activity close to 0%, which is similar to GALC activity levels observed in patients with the infantile form of Krabbe disease. While heterozygous dogs do not display symptoms, dogs homozygous for the mutation are affected.
Krabbe dogs present with a severe phenotype similar to infantile Krabbe disease as summarized in Table 5. While the progression of the Krabbe dog phenotype is less well characterized than the Twitcher mouse, affected Krabbe dogs display demyelination and globoid cells accumulation that affects both CNS and peripheral nerves. They develop hind limb weakness, thoracic limb dysmetria, and tremors at approximately 4-6 weeks of age. Like infantile Krabbe patients, Krabbe dogs present with a consistent and rapid neurologic deterioration after the onset of symptoms. Ultimately, these symptoms progress to a humane endpoint characterized by severe ataxia, pelvic limb paralysis, wasting, urinary incontinence, and sensory deficits by around 15 weeks of age (Fletcher T. F. & Kurtz H. J. (1972) Am J Pathol. 66(2):375-8; Wenger D. A. (2000) Molec Med Today. 6(11):449-451; Bradbury A. M., et al. (2018) Hum Gene Ther. 29(7):785-801).
The aim of this study was to assess the scalability of our therapeutic approach by evaluating the efficacy of an AAV vector similar to rAAVhu68.hGALC in a large animal disease model. To accomplish this, we utilized a naturally occurring canine model of Krabbe disease, which was administered via the intended clinical route (ICM) a vector similar to rAAVhu68.hGALC that encodes an engineered canine version of GALC (AAVhu68.CB7.CI.cGALCco.rBG) (
A study design is provided in
After dosing, animals were monitored daily (cage-side observations), weighed weekly, and videotaped biweekly. They also received a brain MRI and, periodically, a complete physical exam, neurological exam, nerve conduction recordings, and BAER recording. The purpose of these examinations was to evaluate the integrity of the CNS and PNS. Efficacy readouts included brain myelination (assessed by MRI 8 weeks post injection, BAER, and histology at the terminal endpoint), peripheral nerve myelination (assessed by NCV and histology at the terminal endpoint), neurological examination, and physical examination (body weight, gait, reflexes, proprioception, videotaping of dogs playing in an open area biweekly). In addition, pharmacology, safety, and vector biodistribution were assessed because the vector injected was comparable to rAAVhu68.hGALC and the intended clinical ROA (ICM administration) was used. Nerve conduction assessments measured the integrity of nerves as an indirect measurement of myelin integrity. BAER recording is similar to NCV, except it tests conduction and myelin integrity in the auditory pathways of the CNS (i.e., the brainstem). Safety readouts include periodical cell blood counts (CBC), serum chemistry, and coagulation on Day 0 before injection, and Day 14, 28, 56, 70, 120, and 180 (each time ±2 days). CSF was also processed for lipidomic biomarker analysis and cell counts when volume permitted to investigate disease correction (lipidomics, psychosine concentration) and WBC counts (pleocytosis) as a safety readout. On Day 56, dogs were examined by MRI (T1 and T2-weighted) to observe myelination in the CNS. Enzymatic activity of GALC was assessed in both CSF and serum at baseline at the time points indicated below to measure the quantity of active therapeutic enzyme secreted in the CNS and PNS. The study days for each assay were selected in order to minimize the sedation of the animals while collecting complete data at the appropriate time points that correspond to the known Krabbe disease progression in dogs (
Blood and CSF were collected for safety and biomarker analysis. A comprehensive list of tissues were sampled for histopathology to determine whether the administration of rAAVhu68.hGALC reduces demyelination and neuroinflammation. Transduction and expression of rAAVhu68.hGALC were assessed by biodistribution. GALC enzyme activity readouts (
In presymptomatic Krabbe dogs, a single cisterna magna injection of rAAVhu68.cGALC at 3.00×1013 GC provided phenotypic correction (
The study schedule and endpoints are presented below in Table 6.
A toxicology study is conducted using the same rAAVhu68.hGALC vector lot as that used in the mouse MED study and is conducted in NHPs because they better replicate the size and CNS anatomy of humans and can be treated using the clinical ROA (ICM). It is expected that the similarity in size, anatomy, and ROA results in representative vector distribution and transduction profiles, which allows for more accurate assessment of toxicity than is possible in mice or dogs. In addition, more rigorous neurological assessments can be performed in NHPs than in rodent or canine models, allowing for more sensitive detection of CNS toxicity.
ICM vector administration results in immediate vector distribution within the CSF compartment. Doses are scaled by brain mass, which provides an approximation of the size of the CSF compartment. Dose conversions are based on a brain mass of 0.15 g for a newborn mouse (Gu Z., et al. (2012) PLoS One. 7(7):e41542.), 0.4 g for a juvenile-adult mouse (Gu Z., et al. (2012) PLoS One. 7(7):e41542.), 90 g for a juvenile and adult rhesus macaque (Herndon J. G., et al. (1998) Neurobiol Aging. 19(3):267-72), 60 g for a dog, 800 g for 4-12-month-old infants, and 1300 g for adult humans (Dekaban A. S. (1978) Ann Neurol. 4(4):345-56). Doses for the NHP toxicology study, the murine MED study, and the equivalent human doses are shown in Table 7.
Juvenile rhesus macaques are selected depending on disease target in order to be similar anatomically to the proposed Phase ½ study population. The doses for the NHP toxicology study reflect the doses that are used in a Phase ½ clinical study, and are selected with consideration of: 1) results from the pharmacology studies and 2) translation of dose from the pharmacology studies to NHP and human, with consideration of the maximal feasible dose.
Accordingly, a 180-day GLP-compliant safety study is conducted in adult rhesus macaques to investigate the toxicology of rAAVhu68.CB7.CI.cGALCco.rBG (rAAVhu68.hGALC) following ICM administration. The 180-day evaluation period was selected because this allows sufficient time for a secreted transgene product to reach stable plateau levels following ICM AAV administration. The study design is outlined in Table 8 and Table 9. Juvenile Rhesus macaques (approximately 1.5 years of age) receive either 4.50×1012 GC total or 1.50×1013 GC total (or vehicle). Dose levels are selected to be equivalent to those are evaluated in the MED study when scaled by brain mass (assuming 0.4 g for the juvenile-adult mouse, 90 g for the rhesus monkey. The high dose is equivalent to the dose evaluated in the Krabbe dog model (assuming a brain weight of 60 g). Baseline neurologic examinations, clinical pathology (cell counts with differentials, clinical chemistries, and a coagulation panel), CSF chemistry, and CSF cytology are performed. Following vector (or vehicle) administration, the animals are monitored daily for signs of distress and abnormal behavior.
Blood and CSF clinical pathology assessments and neurologic examinations are performed on a weekly basis for 30 days following vector or vehicle administration, and every 30 days thereafter. At baseline and at each 30-day time point thereafter, anti-AAVhu68 NAbs and cytotoxic T lymphocyte (CTL) responses to AAVhu68 and the GALC product are assessed by an interferon gamma (IFN-γ) enzyme-linked immunospot (ELISpot) assay.
At either 90 or 180 days following rAAVhu68.hGALC or vehicle administration, animals are euthanized, and tissues are harvested for comprehensive microscopic histopathological examination. The histopathological examination focuses on CNS tissues (brain, spinal cord, and dorsal root ganglia) and the liver because these are the most heavily transduced tissues following ICM administration of rAAVhu68 vectors. In addition, lymphocytes are harvested from the systemic circulation (PBMC), spleen, and CNS-draining lymph nodes to evaluate the presence of T cells reactive to both the capsid and transgene product in these organs at the time of necropsy. Tissues are harvested and archived in case any finding warrants further analysis of vector biodistribution.
aNumber of animals assessed.
bIncludes complete blood counts and differentials (hematology), clinical chemistries and coagulation panel
cIncludes clinical pathology and biomarker
The FIH trial is a Phase ½ dose escalation study of a single ICM administration of rAAVhu68.hGALC in pediatric patients with the infantile form of Krabbe disease caused by homozygous or compound heterozygous mutations in the GALC gene. This FIH trial enrolls and treats at least 12 subjects who are followed up for 2 years, with continued long-term follow-up (LTFU) for a total of 5 years post-dose in line with the recommended LTFU for adenoviral vectors described in the draft “FDA Guidance for Industry: Long Term Follow-Up after Administration of Human Gene Therapy Products” (July 2018). The primary objectives are to assess the safety and tolerability of rAAVhu68.hGALC. The secondary objectives of this study are to evaluate the impact of rAAVhu68.hGALC on disease-relevant assessments, including survival, age-appropriate neurocognitive measurements, and age-appropriate motor and/or linguistic assessments. These endpoints are selected in consultation with disease experts and clinicians and based on observations on the disease evolution in untreated patients with infantile Krabbe disease.
Optionally, combination therapy of HSCT and AAV gene therapy can be evaluated.
The FIH is an open-label, multi-center, dose escalation study of rAAVhu68.hGALC to evaluate safety, tolerability, and exploratory efficacy endpoints in pediatric subjects with the infantile form of Krabbe disease. The dose-escalation phase assesses the safety and tolerability of a single ICM administration of two dose levels of rAAVhu68.hGALC, with staggered, sequential dosing of subjects. The rAAVhu68.hGALC dose levels are determined based on data from the GLP NHP toxicology study and the murine (MED) study and consist of a low dose (administered to Cohort 1) and a high dose (administered Cohort 2). Both dose levels are anticipated to confer therapeutic benefit, with the understanding that, if tolerated, the higher dose is expected to be advantageous. The sequential evaluation of the low dose followed by the high dose enables the identification of the maximum tolerated dose (MTD) of the doses tested. Finally, an expansion cohort (Cohort 3) receives the MTD of rAAVhu68.hGALC (
Since infantile Krabbe Disease is marked by a rapid disease course once symptoms emerge, and given that some neonates present with signs of disease at birth, the proposed study design allows for concurrent enrollment of subjects 30 days after dosing of the first patient in Cohort 1 (low dose) and Cohort 2 (high dose), based on the Investigator's benefit-risk assessment for that subject. The rationale for this is that the risk of missing the treatment window because the patient experienced disease progression would outweigh the potential benefit of prolonged safety follow-up before dosing the next patient. Such a scenario where patients experience substantial disease progression in a matter of weeks was cited as a possible cause of the poor transplant outcomes observed in EIKD patients identified through NBS in New York (Wasserstein M. P., et al. (2016) Genet Med. 18(12):1235-1243), highlighting the need for prompt referral of patients for treatment.
An independent Safety Board conducts a safety review of all accumulated safety data between cohorts and after full enrollment of the second cohort to make a recommendation regarding further conduct of the trial. The Safety Board also conducts a review any time a safety review trigger (SRT) is observed. The 1-month dosing interval between the first and second subject in each cohort allows for evaluation of AEs indicative of acute immune reactions, immunogenicity or other dose-limiting toxicities as well as clinical review of any sensory neuropathy that might present itself consistent with the anticipated time course for development of sensory neuropathology secondary to transduction of DRG, which occurs within 2-4 weeks in non-clinical studies.
Additional subjects are enrolled in an expansion cohort that receives the MTD. Enrollment of these additional subjects does not require a 4-week observation window between subjects (
All treated subjects are followed for 2 years to evaluate the safety profile and to characterize the pharmacodynamic and efficacy properties of rAAVhu68.hGALC. Subjects are followed for an additional 3 years (for a total of 5 years post-dose) during the LTFU period of the study to evaluate long-term clinical outcomes, which is in line with draft “FDA Guidance for Industry: Long Term Follow-Up after Administration of Human Gene Therapy Products” (July 2018).
No statistical comparisons are planned for safety evaluations; all results are descriptive only. Data are listed and summary tables are produced.
Statistical comparisons are performed for secondary and exploratory endpoints. Measurements at each time point are compared to baseline values for each subject, as well as data from age matched healthy controls and natural history data from Krabbe disease patients with comparable cohort characteristics where available for each endpoint.
All data are presented in subject data listings. Categorical variables are summarized using frequencies and percentages, and continuous variables are summarized using descriptive statistics (number of non-missing observations, mean, SD, median, minimum, and maximum). Graphical displays are presented as appropriate.
The FIH focuses on infantile subjects with symptom onset before 9 months of age, who represent the population with the highest unmet need as HSCT is not indicated for these patients. Furthermore, these patients have a singularly devastating disease course with rapid and highly predictable decline that is homogeneous in the presentation of both motor and cognitive impairment (Bascou N., et al. (2018) Orphanet J Rare Dis. 13(1):126). In fact, patients presenting with symptoms before 9 months of age have a disease course that resembles early infantile Krabbe Disease, with rapid and severe cognitive and motor impairment progression, and failure to gain any functional skills following initial signs and symptoms of disease. The majority of these patients is expected to die within the first few years of life (2 year survival ranges from 26-50% (Duffner P. K., et al. (2011) Pediatr Neurol. 45(3):141-8; Beltran-Quintero M. L., et al. (2019) Orphanet J Rare Dis. 14(1):46). The phenotype of infants with onset between 9 and 12 months of age is more variable, with some exhibiting the severe early infantile Krabbe Disease phenotype, while others have a less severe disease presentation with (near) normal cognition and markedly better adaptive and fine motor skills, which makes it difficult to predict the phenotype of a newly diagnosed patient with onset between 9 and 12 months (Bascou N., et al. (2018) Orphanet J Rare Dis. 13(1):126). Consequently, the population is restricted to subjects with symptom onset <9 months of age whose predictable and rapid decline supports a robust study design and evaluation of functional outcomes within a reasonable follow up period. For this group, treatment is expected to stabilize disease progression and prevent loss of skills such as acquired developmental and motor milestones, prolong survival, delay or prevent development of seizures.
Despite a shared underlying pathophysiology, the adult Krabbe phenotype and disease course is notably milder from devastating infantile Krabbe Disease form so demonstration of disease stabilization in adults would not provide reason to believe for the therapy in infantile Krabbe Disease. Importantly, adult Krabbe disease onset is highly variable, and progression is slower and more variable with decline occurring over many years to decades (Jardim L. B., et al. (1999) Arch Neurol. 56(8):1014-7; Debs R., et al. (2013) J Inherit Metab Dis. 36(5):859-68). It would be very challenging to design a clinical trial that could unequivocally demonstrate efficacy of the investigational therapy in the context of a protracted natural course. The fact that HSCT provides a treatment option able to stabilize or even improve the disease manifestations is another important consideration (Sharp M. E., et al. (2013) JIMD Rep. 10:57-9; Laule C., et al. (2018) Journal of Neuroimaging. 28(3):252-255). Finally, NBS has not been widely adopted in the US and is not available in Europe, and the ambiguous, non-specific clinical presentation means that adult Krabbe disease continues to be underdiagnosed and thus access to such patients remains exceedingly rare (Wasserstein M. P., et al. (2016) Genet Med. 18(12):1235-1243).
Study Population—Exclusion of Subjects with Severe Disease
Given the nature of Krabbe disease with CNS injury thought to be largely irreversible and the very rapid disease progression in the infantile population, rAAVhu68.hGALC is expected to confer the greatest potential for benefit in patients with no or mild to moderate disease that do not exhibit signs that are uniquely associated with the latter stages of disease, including deafness, blindness, severe weakness with loss of primitive reflexes (Escolar M. L., et al. (2006) Pediatrics. 118(3):e879-89). Additionally, abnormal pupillary reflexes, jerky eye movement, or visual tracking difficulties are more common in very advanced disease than in patients with moderate signs and symptoms, and are not typically observed in the early disease stages (Escolar M. L., et al. (2006) Pediatrics. 118(3):e879-89). Therefore, evidence of more than one of these signs are considered an indicator of advanced disease and result in exclusion from the trial. Due to the severe disability, these patients would be unlikely to gain substantial benefit from the therapy beyond stabilization of disease at a low level of clinical function are excluded, the benefit/risk profile would not be favorable, and they would exhibit floor effects on various clinical and instrumental assessments that would preclude evaluation of the efficacy of rAAVhu68.hGALC. This population may also present with a higher risk for non-treatment-related safety concerns due to the advanced state of disease sequelae and are excluded from this trial.
Patients with clinical seizures are not excluded from the trial, unless in the opinion of the Investigator the child has other signs of advanced disease and would be unlikely to benefit from treatment. This is because 1) seizures are not uniquely associated with advanced disease and 2) seizures are an endpoint in the trial and excluding patients with seizures might bias the study towards a population that is less prone to experience seizures.
Presymptomatic infantile Krabbe Disease patients are excluded from the dose escalation portion of the study (Cohort 1 and Cohort 2) in which rAAVhu68.hGALC alone is evaluated. For these patients, at least in the US, HSCT is considered a therapeutic option and the treatment of choice, even if it only serves to delay disease progression. The prevailing US KOL opinion is that testing an unproven investigational therapy would be considered unethical in this population because the exceedingly narrow therapeutic window would effectively deprive the patient of access to a treatment shown to provide at least partial benefit (i.e., should gene therapy prove unsuccessful there would unlikely be time to “rescue” with HSCT). Thus, rAAVhu68.hGALC should be reserved for patients with the clearest unmet need (i.e., infantile Krabbe disease patients with signs and symptoms who are not eligible for HSCT).
Our preclinical studies confirm superior efficacy of a gene therapy and HSCT combined over either approach alone, thus the combination therapy of HSCT and rAAVhu68.hGALC is evaluated as an expansion cohort in the FIH study (Cohort 3). Both symptomatic and pre-symptomatic patients who meet the criteria outlined in this document are eligible for enrollment as this cohort evaluates the safety and efficacy of rAAVhu68.hGALC in the context of HSCT and only progresses if the preclinical data provide a reason to believe for improved efficacy over HSCT alone.
Given that symptom onset can occur perinatally, or even in utero, treatment occurs as early as possible to maximize potential benefit, thus the minimum age of the study was selected as 1 month old at dosing as current consensus guidelines recommend HSCT before 1 month of age in eligible patients (Kwon J. M., et al. (2018) Orphanet J Rare Dis. 13(1):30). Requiring subjects to be 1 month or older allows subjects and families to consider other forms of standard-of-care treatment prior to their eligibility for this trial.
Another consideration in selecting the lower age limit is to ensure that the treatment, and specifically the ICM procedure can be safely carried out in such a young patient. After careful review of imaging scans from infants as young as 1 or 2 weeks of age, an expert interventional radiologist at the University of Pennsylvania confirmed that there is no specific anatomical concern with performing CT guided ICM administration in a 1-month-old infant, provided the rationale for treatment is supported.
In addition to measuring safety and tolerability as primary endpoints, secondary and exploratory pharmacodynamic and efficacy endpoints were chosen for this study based on the current literature and in consultation with leading clinicians specializing in Krabbe disease. These endpoints are anticipated to demonstrate meaningful functional and clinical outcomes in this population. Endpoints are measured at 30 days, 90 days and 6 months, and then every 6 months during the 2-year short-term follow-up period, except for those that require sedation and/or a lumbar puncture, as presented in
In view of the rapid and homogeneous rate of disease progression in the infantile population (Duffner P. K., et al. (2011) Pediatr Neurol. 45(3):141-8; Bascou N., et al. (2018) Orphanet J Rare Dis. 13(1):126) a 2 year follow up for primary outcomes evaluation is considered sufficient to evaluate the impact of rAAVhu68.hGALC over time. In addition, the LTFU to 5 years post-treatment is very informative for assessing long-term outcomes and if the treatment is effective in prolonging survival and stabilizing patients at a level of function similar or superior to the outcomes observed in presymptomatic patients after HSCT.
Administration of rAAVhu68.hGALC stabilizes disease progression as measured by survival, preventing loss of developmental and motor milestone potentially supporting acquisition of new milestones, onset and frequency of seizures. Death typically occurs in the first 3 years of life for a majority patients diagnosed with early infantile Krabbe disease, with median mortality extending to 5 years in the late infantile population which incorporates patients with symptom onset from 7-12 months (Duffner P. K., et al. (2012) Pediatr Neurol. 46(5):298-306). By limiting the inclusion criteria to patients with onset on or before 9 months of age, the population has more severe, early infantile-like phenotype and disease course (Bascou N., et al. (2018) Orphanet J Rare Dis. 13(1):126). Given the rapid decline seen in cases of untreated infantile Krabbe disease, treatment with rAAVhu68.hGALC extends life expectancy during the follow-up periods. Motor milestone development depends on the age and stage of disease at the time of subject enrollment (Bascou N., et al. (2018) Orphanet J Rare Dis. 13(1):126; Beltran-Quintero M. L., et al. (2019) Orphanet J Rare Dis. 14(1):46). Given the severity of disease in the target population, subjects may have achieved motor skills by enrollment, developed and subsequently lost other motor milestones, or not yet shown signs of motor milestone development. Assessments therefore track age-at-achievement and age-at-loss for all milestones. Motor milestone achievement is defined for six gross milestones based on the World Health Organization (WHO) criteria outlined in Table 11.
Given that subjects with infantile Krabbe disease can develop symptoms within the first weeks or months of life, and acquisition of the first WHO motor milestone (sitting without support) typically does not manifest before 4 months of age (median: 5.9 months of age), this endpoint may lack sensitivity to evaluate the extent of therapeutic benefit, especially in subjects who had more overt symptoms at the time of treatment. For this reason, assessment of age appropriate developmental milestones that can be applied to infants are also included (Sharp M. E., et al. (2013) JIMD Rep. 10:57-9). One short-coming is that the published tool is intended for use by clinicians and parents, and organizes skills around the typical age of milestone acquisition without referencing normal ranges. However, the data may be informative to summarize retention, acquisition, or loss of developmental milestones over time, relative to untreated children with infantile Krabbe disease or the typical time of acquisition in neurotypical children.
While seizures are not a presenting symptom for the infantile population, approximately 30-60% of infantile patients will eventually develop seizures in the later stages of the disease (Duffner P. K., et al. (2011) Pediatr Neurol. 45(3):141-8). The delayed onset of seizure activity enables us to determine if treatment with rAAVhu68.hGALC can either prevent or delay onset of seizures in this population, or decrease the frequency of seizure events. Parents are asked to keep seizure diaries which track onset, frequency, length and type of seizure. These entries are discussed with and interpreted by the clinician at each visit.
As exploratory measures, clinical scales are used to quantify the effects of rAAVhu68.hGALC on development and changes in adaptive behaviors, cognition, language, motor function, and health-related quality of life. Each measure proposed has been used either in the Krabbe population or in a related population.
The scale and relevant domains are briefly described below:
To assess the effect of rAAVhu68.hGALC on disease pathology, changes in myelination, functional outcomes related to myelination, and potential disease biomarkers are measured. As the primary hallmark of disease, central and peripheral demyelination slow or cease in progression with rAAVhu68.hGALC administration. Central demyelination is tracked by diffusion-tensor magnetic resonance imaging (DT-MRI) anisotropy measurements of white matter regions and fiber tracking of corticospinal motors tracts, changes in which are indicators of disease state and progression (McGraw P., et al. (2005) Radiology. 236(1):221-30; Escolar M. L., et al. (2009) AJNR Am J Neuroradiol. 30(5):1017-21). Peripheral demyelination is measured indirectly via nerve conduction velocity (NCV) studies on the motor nerves (deep peroneal, tibial, and ulnar nerves) and sensory nerves (sural, and median nerves) to monitor for fluctuations indicative of a change in biologically active myelin (i.e., F-wave and distal latencies, amplitude or presence or absence of a response).
Development of visual impairment is common in early infantile Krabbe, with 61.2% of the population developing vision loss at some point in the disease according to one study (Duffner P. K., et al. (2011) Pediatr Neurol. 45(3):141-8). Similar to seizures, vision loss is not a common presenting symptom. This offers the opportunity to assess the ability of rAAVhu68.hGALC to delay or prevent vision loss for those subjects that have not developed significant vision loss prior to treatment. Measurement of visual evoked potentials (VEPs) is therefore used to objectively measure responses to visual stimuli as an indicator of central visual impairment or loss. Hearing loss is also common during disease progression and early indications of auditory abnormalities are measured via brainstem auditory evoked response (BAER) testing.
GALC is responsible for the hydrolysis of psychosine. Deficiency of GALC in Krabbe disease results in the accumulation of psychosine both centrally and peripherally. Increased levels of psychosine have been proposed as an indicator of Krabbe disease (Escolar M. L., et al. (2017) Mol Genet Metab. 121(3):271-278). While there is evidence to support its use in detection of early and severe cases of infantile Krabbe, interpretation of fluctuations in psychosine levels over time, following treatment may be difficult, as psychosine levels may also decline in late-stage disease. Thus, evidence of decline in psychosine levels alone would not be sufficient evidence of a treatment effect, unless it was accompanied by clinical disease stabilization.
The following information is provided for sequences containing free text under numeric identifier <223>.
All documents cited in this specification are incorporated herein by reference, as are the sequences and the text of the Sequence Listing (labeled “18-8584PCT_ST25.txt”) filed herewith. U.S. Provisional Patent Application No. 62/810,708, filed Feb. 26, 2019, U.S. Provisional Patent Application No. 62/817,482, filed Mar. 12, 2019, U.S. Provisional Patent Application No. 62/877,707, filed Jul. 23, 2019, and U.S. Provisional Patent Application No. 62/916,652, filed Oct. 17, 2019, are incorporated by reference in their entireties, together with their sequence listings. While the invention has been described with reference to particular embodiments, it will be appreciated that modifications can be made without departing from the spirit of the invention. Such modifications are intended to fall within the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US20/19794 | 2/26/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62810708 | Feb 2019 | US | |
| 62817482 | Mar 2019 | US | |
| 62877707 | Jul 2019 | US | |
| 62916652 | Oct 2019 | US |
