Canine monoclonal antibodies against canine cytotoxic T lymphocyte associated protein 4 (CTLA-4)

1. An antibody or antigen-binding fragment thereof comprising an antigen-binding domain that specifically binds to an epitope of canine cytotoxic T lymphocyte-associated protein 4 (CTLA-4), wherein the antigen-binding domain comprises:

(i) a heavy chain variable region comprising an amino acid sequence having at least 80% identity to the amino acid sequence of the heavy chain variable region set forth in SEQ ID NO: 6; and

(ii) a light chain variable region comprising an amino acid sequence having at least 80% identity to the amino acid sequence set forth in SEQ ID NO: 8;

wherein the heavy chain variable region comprises three heavy chain complementarity determining regions (HCDRs), wherein HCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 1, HCDR2 comprises the amino acid sequence set forth in SEQ ID NO: 2, and HCDR3 comprises the amino acid sequence set forth in of SEQ ID NO: 3; and

wherein the light chain variable region comprises three light chain complementarity determining regions (LCDRs), wherein LCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 4, LCDR2 comprises the amino acid sequence of VDG, and LCDR3 comprises the amino acid sequence set forth in SEQ ID NO: 5.

2. The antibody or antigen-binding fragment thereof of claim 1 , wherein the antibody or antigen-binding fragment thereof is a full-length antibody.

3. The antibody or antigen-binding fragment thereof of claim 2 , wherein the full-length antibody is a canine antibody.

4. The antibody or antigen-binding fragment thereof of claim 1 , wherein the antigen binding domain comprises a heavy chain variable region comprising an amino acid sequence having at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 6.

5. The antibody or antigen-binding fragment thereof of claim 1 , wherein the antigen binding domain comprises a heavy chain variable region comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 6.

6. The antibody or antigen-binding fragment thereof of claim 1 , wherein the antigen binding domain comprises a light chain variable region comprising an amino acid sequence having at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 8.

7. The antibody or antigen-binding fragment thereof of claim 1 , wherein the antigen binding domain comprises a light chain variable region comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 8.

8. The antibody or antigen-binding fragment thereof of claim 2 , wherein the antigen binding domain comprises (i) a heavy chain variable region comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 6; and (ii) a light chain variable region comprising an amino acid sequence having at least 95% identity to the amino acid sequence set forth in SEQ ID NO: 8.

9. A full-length antibody comprising an antigen-binding domain that specifically binds to an epitope of canine cytotoxic T lymphocyte associated protein 4 (CTLA-4), wherein the antigen-binding domain comprises:

(i) a heavy chain variable region that comprises three heavy chain complementarity determining regions (HCDRs), wherein HCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 1, HCDR2 comprises the amino acid sequence set forth in SEQ ID NO: 2, and HCDR3 comprises the amino acid sequence set forth in SEQ ID NO: 3; and

(ii) a light chain variable region that comprises three light chain complementarity determining regions (LCDRs), wherein LCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 4, LCDR2 comprises the amino acid sequence of VDG, and LCDR3 comprises the amino acid sequence set forth in SEQ ID NO: 5.

10. The full-length antibody of claim 9 , wherein:

(i) the heavy chain variable region comprises an amino acid sequence having at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 6; and

(ii) the light chain variable region comprises an amino acid sequence having at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 8.

11. The full-length antibody of claim 9 , comprising a heavy chain amino acid sequence comprising an amino acid sequence having at least 90% identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 10, 12, 14, and 16 and a light chain comprising an amino acid sequence having at least 90% identity to the amino acid sequence set forth in SEQ ID NO: 18.

12. The full-length antibody of claim 9 , wherein the full-length antibody is a canine antibody.

13. An isolated nucleic acid encoding the antibody or antigen-binding fragment thereof of claim 1 .

14. A vector comprising the isolated nucleic acid of claim 13 .

15. A host cell comprising the vector of claim 14 .

16. A method of producing an antibody or antigen-binding fragment thereof that binds to canine cytotoxic T lymphocyte associated protein 4 (CTLA-4), the method comprising culturing the host cell of claim 15 .

17. A pharmaceutical composition comprising the antibody or antigen-binding fragment thereof of claim 1 , and a pharmaceutically acceptable carrier.

18. A method for treating a cancer in a subject in need thereof, the method comprising administering to the subject a therapeutically effective amount of the antibody or antigen-binding fragment thereof of claim 1 , thereby treating the cancer in the subject.

19. The method of claim 18 , wherein the cancer is associated with cytotoxic T lymphocyte associated protein 4 (CTLA-4).

20. The method of claim 18 , wherein the subject is canine.