Patent Application
20190203192
The present invention relates generally to antibody-based molecules for treating various CNS-related diseases.
Therapy is often associated with adverse effects. To minimize the adverse effects, one needs to improve the specificities of the therapeutic agents, i.e., attacking only the disease agents or cells/tissues. However, having such selectivity is not always possible. For example, antibodies are highly specific to their target antigens with high affinities, and have been approved for therapeutic or diagnostic applications in some diseases. However, the target antigen expression is not necessarily disease-specific. Therefore, most therapeutic antibodies may also target normal tissues in addition to targeting the disease lesions, thereby causing adverse effects.
Another approach to reducing the adverse effects is to deliver the therapeutic agents as pro-drugs, which are activated only at the target sites. Many prodrugs are shown to be effective in reducing the undesired side effects. However, most prodrugs are small molecules.
Central nervous system (CNS) presents unique challenges for specific targeting of therapeutic agents. Therefore, there is still a need for better approaches to the treatment of CNS diseases or disorders.
Embodiments of the present invention relate to uses of KLK6 substrate-containing recombinant protein or peptide to fuse with the N-termini of the antibody to produce prodrug antibodies (pro-antibodies) with reduced antigen recognition function. These pro-antibodies can be activated in tissues having high concentrations of KLK6 protease, such as in the CNS.
Inventors of the present invention found that the KLK6 substrate sequences in the pro-antibodies are not cleaved by the KLK6 in serum due to the low concentration of KLK6 in serum. In contrast, the pro-antibodies are cleaved by the KLK6 in the CNS due to higher concentrations of KLK6 therein. Therefore, the functions of the antibodies can be suppressed in the peripheral blood to prevent the adverse effects and to minimize the waste of antibodies in the peripheral tissues. These pro-antibodies can be activated to target CNS-related diseases or disorders once it gets into the CNS.
In one aspect, embodiments of the invention relate to antibody prodrugs capable of being selectively activated in a central nervous system (CNS) by protease KLK6. An antibody prodrug in accordance with one embodiment of the invention includes an antibody, or a binding fragment thereof, for treating a disease or disorder in the CNS; a KLK6 cleavable peptide fused to an N-terminus of a heavy chain and/or a light chain of the antibody; and a blocker fused to an N-terminus of the KLK6 cleavable peptide.
In accordance with embodiments of the invention, the disease or disorder in the central nervous system (CNS) may be a cancer, inflammatory disease, autoimmune disease, infectious disease, or neuron degeneration disease.
In accordance with embodiments of the invention, the blocker comprises a protein, protein domain, or a peptide. In accordance with embodiments of the invention, the KLK6 cleavable peptide is derived from a natural KLK6 substrate, a peptide phage library, a synthetic peptide library, or any peptide sequence that can be cleaved by KLK6.
In accordance with embodiments of the invention, the antibody is a monoclonal antibody or a binding fragment thereof, bispecific antibody, multi-specific antibody, antibody drug conjugates (ADC), immunocytokine, immunohormone, or immunotoxin. The antibody may be a murine antibody, chimeric antibody, humanized antibody, or human antibody. In accordance with embodiments of the invention, the antibody may be any suitable antibody, such as anti-VEGF antibody or anti-PD-1 antibody
In another aspect of the invention, embodiments of the invention relate to methods for treating a disease or disorder in the CNS. A method in accordance with one embodiment of the invention comprises: administering to a subject in need thereof an effective amount of an antibody prodrug (i.e., pro-antibody) of the invention.
An effective amount is the amount that can achieve the desired effects of the treatment. One skilled in the art would appreciate that the effective amount would depend on the disease conditions, the route of administration, the conditions of the patient (e.g., age, body weight, gender, etc.), and one skilled in the art would be able to determine the effective amount without undue experimentation. For example, in accordance with embodiments of the invention, an effective amount may range from 0.1 μg/Kg to 10 mg/Kg, preferably from 1 μg/Kg to 1 mg/Kg, more preferably from 1 μg/Kg to 0.1 mg/Kg, based on the weight of the patient.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
As used herein, the term “antibody” refers to a monoclonal antibody, a bispecific antibody, a multi-specific antibody, or an antibody drug conjugate (ADC). The “antibody drug conjugate” may be an immunocytokine, an immunohormone, or an immunotoxin. The term “immunocytokine” refers to a recombinant antibody-cytokine fusion protein. The term “immunohormone” refers to a recombinant antibody-hormone fusion protein. An example of an immunohormone is an antibody-leptin fusion protein. The term “immunotoxin” refers to a recombinant antibody-toxin conjugate. A binding fragment of an antibody may be an scFv, Fab, or F(ab′)2.
The term “fused to an N-terminus of a protein” refers to forming a fusion protein at the N-terminus of the protein. The term “blocker” refers to a peptide or protein used to reduce or block the activity of an antibody, i.e., to convert the antibody into a prodrug. In addition, the blocker may be used to facilitate delivery into the CNS system, see e.g., Yu, Y. J. et al., “Boosting brain uptake of a therapeutic antibody by reducing its affinity for a transcytosis target,” Sci. Trans. Med. 3, 84ra44 (2011).
The term “KLK6 cleavable peptide” refers to a peptide that can be cleaved by KLK6, which is a trypsin-like protease. Various KLK6 cleavable peptide sequences are known in the art or one skilled in the art can easily determine whether a particular sequence can be cleaved by KLK6 without undue experimentation.
Embodiments of the invention relate to therapeutic antibodies for the treatments of diseases or disorders in the central nervous system (CNS). These antibodies are in the form of a prodrug (pro-antibody), which includes a peptide fragment (blocking peptide, or blocker) attached to the N-terminus of a variable domain of an antibody to block the binding of the antibody to the target antigen. The blocking peptides are similar to the pro-peptides of certain proenzymes. Cleavage of the blocking peptides by a selective protease will release the active antibodies.
Embodiments of the invention rely on kallikrein-6 (KLK-6) for the specific activation of the pro-antibodies. Specifically, embodiments of the present invention use KLK6 substrate-containing recombinant protein or peptide to fuse with the N-termini of an antibody. The KLK6 substrate-containing recombinant protein or peptide functions like a pro peptide to block or reduce the antigen recognition function of the antibody.
The KLK6 substrate would not be cleaved to any appreciable extent by the KLK6 in blood circulation due to the low concentrations of KLK6 in the serum in peripheral blood. However, the KLK6 substrate-containing recombinant protein or peptide can be efficiently cleaved by the KLK6 at a concentration found in the CNS. Therefore, the function of the antibodies can be blocked or minimized in the peripheral blood to prevent the adverse effects and to reduce the unnecessary waste of the antibodies. These pro-antibodies can be activated to target CNS-related diseases once it gets into the CNS.
The human kallikrein (KLK) family includes 15 secreted serine proteases that are expressed in various tissues. Among these, KLK6 is found to be highly expressed in CNS and is also overexpressed in breast and ovarian cancer tissues. KLK6, also known as zyme, protease M, and neurosin, is a trypsin-like serine protease. KLK6 is constitutively expressed in oligodendrocytes in the CNS and its expression is enhanced after spinal cord injury (SCI) and in active multiple sclerosis (MS) lesions. Many proteins have been shown to be cleaved by KLK6, including human myelin basic protein (MBP), beta amyloid peptide (Aβ), plasminogen, myelin, and α-synuclein, etc.
The KLK6 levels in various human fluids have been determined, and KLK6 has been found to be significantly enriched in the cerebrospinal fluid (CSF), as compared to blood circulation. This differential expression levels enable an opportunity for pro-drug activation in the CNS.
In accordance with embodiments of the invention, to reduce the unwanted side effects, antibody prodrugs with reduced function in the peripheral blood have been developed. These antibody prodrugs can be activated by KLK6 in the central nervous system. The invention can be applied in various CNS-related diseases, e.g., cancers, inflammatory diseases, autoimmune diseases, infectious diseases, or neuron degeneration diseases.
In accordance with some embodiments of the invention, only the light-chain N-terminus contains a blocker. In accordance with other embodiments of the invention, only the heavy-chain N-terminus contains a blocker. Because antigen-antibody binding involves the variable domains of both the heavy-chain and the light-chain, blocking either the heavy-chain or the light-chain N-terminus would be sufficient to disrupt the antigen-antibody binding.
In accordance with some embodiments of the invention, both the light-chain N-terminus and the heavy-chain N-terminus each contain a blocker. The dual blocking of both the heavy-chain and the light-chain variable regions may produce better blocking of the antigen-antibody interactions.
In accordance with embodiments of the invention, a blocker comprises a KLK6 substrate-containing protein, protein domain, or peptide, such that the active antibody will be released only in the environment having KLK6 above certain concentration. KLK6 has been shown to be a trypsin-like protease, preferring to cleave on the carboxyl side of an arginine residue. Li et al. found that KLK6 prefers a peptide substrate with the P1 position occupied by Arg and a strong preference for Ser in P1′. (Protein Sci., 17(4): 664-672 (2008)). Magklalra et al. (Biochem. Biophys. Res. Commun., 307(4): 948-55 (2003)) also found that KLK6 cleaves with much higher efficiency after Arg than Lys and with a preference for Ser or Pro in the P2 position. Based on this information, one can design a peptide sequence that would be efficiently cleaved by KLK6. One skilled in the art would appreciate that many peptide sequences would fulfill these criteria and embodiments of the invention are not limited to any particular examples used in this description. Such a peptide will be referred to generically as a KLK6 substrate (or KLK6s) in this description.
Embodiments of the invention are based on the observation that KLK6 exists in a much higher concentration in the CNS than in the peripheral blood. The concentration of KLK6 in the peripheral blood ranges from 0 to 12.6 μg/L, whereas the concentration of KLK6 in the CNS ranges from 41 to 2053 μg/L. With this significant difference in the KLK6 concentrations between the peripheral blood and CNS, a blocker fusion antibody (pro-antibody) of the invention can maintain its low activity in the peripheral blood to prevent any adverse effects, but can be activated by the KLK6 in the CNS for its therapeutic function.
The following description uses specific examples to illustrate embodiments of the invention. One skilled in the art would appreciate that these examples are for illustration only and are not intended to limit the scope of the invention because variations and modifications are possible without departing from the scope of the invention.
In the following examples, various fusion proteins are prepared by constructing expression vectors containing the desired sequences. Any suitable vectors known in the art may be used. In the following examples, the KLK6s-containing peptide/protein-fused antibodies were constructed by polymerase chain reaction (PCR) and cloned into the multiple cloning sites of pTCAE8 vector (plasmid). The particular cDNA sequences for these proteins and the vectors are known in the art and readily available. The methods used are conventional. The various vectors and reagents may be obtained from commercial sources. Thus, one skilled in the art would be able to obtain these reagents and perform the described experiments without undue experimentation.
In this example, a leptin-KLK6s fused Avastin Fab is used as a pro-antibody to test the ability of KLK6 to release Avastin Fab. The fusion protein (pro-antibody) is incubated with KLK6 at the serum concentration, the CSF concentration, 1 μM, or 2 μM, respectively, for 24 hours.
The proteins were separated by SDS-PAGE and stained with Coomassie Brilliant Blue R-250 (CBR) (
These results indicate that a pro-antibody in accordance with embodiments of the invention would survive in the peripheral blood and can be efficiently activated once in the CNS.
In this example, the binding kinetics of anti-VEGF Fab (Lucentics®; ranibizumab) or the Leptin-KLK6s fused Avastin Fab is determined by Surface Plasmon Resonance (SPR) (BIAcore).
These results show that the blocking peptide/protein was effective in preventing pro-antibody bindings to its antigen and that after cleavage of the blocker (pro-peptide or pro-protein), the active antibody was released and could bind specifically to its target. These results validate the approach of the invention.
In this example, an FR1 peptide-KLK6s fused Avastin-KLK6s-Leptin was incubated with KLK6 at the CSF concentration for 6, 24, or 48 hours, respectively, wherein the FR1 peptide is the framework region 1 of Avastin. The proteins were then separated by SDS-PAGE and stained with CBR.
In this example, the binding kinetics of anti-VEGF antibody (Avastin) or the FR1 peptide-KLK6s fused Avastin-KLK6s-Leptin is determined by SPR (BIAcore).
In this example, different KLK6s-containing peptide blockers fused Avastin are incubated with KLK6 at the CSF concentration for 24 hours.
As compared with the Avastin control, different KLK6-cleavable peptide containing blockers fused Avastin without KLK6 digestion showed reduced responses, whereas with the KLK6 digestion the different KLK6-cleavable peptide containing blockers fused Avastin was reactivated for VEGF binding. In the peptide blockers fused Avastin with the uncleavable linker sequence (SSYISNYG; SEQ ID NO:13), the VEGF binding ability of the peptide blockers fused Avastin showed reduced response units before and after KLK6 digestion. These results demonstrated that embodiments of the invention with different blocker sequences or KLK6 substrate sequences can be activated by KLK6. In this example, the peptide blocker sequences and the KLK6s sequences are listed in Table 1. As shown, the peptide blocker sequences may include certain amino acids that function as spacers to separate the KLK6 substrate sequences from the antibody sequences. The spacer function to ensure that KLK6 can access the cleavage sequences. The peptide blocker sequences to the N-terminal side of the cleavage sequences can be any protein or any peptide sequences.
In this example, KLK6s-containing peptide blocker fused to the N-termini of anti-PD-1 mAbs (Nivolumab; Opdivo®) are incubated with KLK6 at the CSF concentration for 24 hours.
In this example, FR1 peptide-KLK6s fused Avastin-KLK6s-Leptin was injected into BALB/c mice through i.v. injection. The serum samples and brain samples were harvested at 0.08, 2, 4, and 8 hours post-injection, respectively. The active antibodies and total antibody concentrations were determined by ELISA.
Some embodiments of the invention relate to methods for treating a CNS disease. A method in accordance with one embodiment of the invention comprises administering to a subject in need thereof an effective amount of a pro-antibody of the invention. The pro-antibody comprises a blocking peptide attached to the N-terminus of the heavy chain and/or light chain of an antibody or a binding fragment thereof. The binding fragment of an antibody may be an Fab, scFv, or F(ab′)2, etc.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. For example, other antibodies may be used instead of the ones shown in these examples. Similarly, the blocking peptide fragment can include any proteins or peptides linked by a KLK6 substrate sequence to the antibodies. Accordingly, the scope of the invention should be limited only by the attached claims.
This claims the benefit of PCT/US2017/069135, filed on Dec. 29, 2017, which claims the benefit of Provisional Application No. 62/440,296, filed on Dec. 29, 2016. The disclosures of these prior application are incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2017/069135 | Dec 2017 | US |
| Child | 15859500 | US |
