Anti-PD-L1 antibodies and diagnostic uses thereof

1. A method of detecting the presence or expression level of PD-L1 in a biological sample from a subject comprising contacting the biological sample with an antibody that specifically binds PD-L1 and detecting the presence of the bound antibody, wherein the antibody comprises a heavy chain variable domain (VH) sequence of SEQ ID NO: 16 and a light chain variable domain (VL) sequence of SEQ ID NO: 17.

2. The method of claim 1 , wherein the detecting is by immunohistochemistry (IHC), immunofluorescence (IF), flow cytometry, enzyme-linked immunosorbent assay (ELISA), or immunoblotting.

3. The method of claim 2 , wherein the detecting is by IHC.

4. The method of claim 1 , wherein the biological sample comprises a fixed tissue.

5. The antibody of claim 4 , wherein the fixed tissue is a formalin-fixed paraffin-embedded (FFPE) tissue.

6. The method of claim 1 , wherein the biological sample is from a subject having, or at risk of, a cancer.

7. The method of claim 6 , wherein the cancer is non-small cell lung cancer, squamous cell cancer, small-cell lung cancer, cancer of the peritoneum, hepatocellular cancer, gastrointestinal cancer, pancreatic cancer, glioma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney cancer, liver cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, leukemia, or head and neck cancer.

8. The method of claim 7 , wherein the cancer is non-small cell lung cancer, breast cancer, or bladder cancer.

9. The method of claim 1 , wherein the biological sample is a tumor sample.

10. The method of claim 9 , wherein the tumor sample comprises tumor-infiltrating immune cells, tumor cells, stromal cells, or any combination thereof.

11. The method of claim 10 , wherein the tumor sample has a detectable expression level of PD-L1 in tumor-infiltrating immune cells that comprise about 1% or more of the tumor sample by area.

12. The method of claim 11 , wherein the tumor sample has a detectable expression level of PD-L1 in tumor-infiltrating immune cells that comprise about 5% or more of the tumor sample by area.

13. The method of claim 12 , wherein the tumor sample has a detectable expression level of PD-L1 in tumor-infiltrating immune cells that comprise about 10% or more of the tumor sample by area.

14. The method of claim 9 , wherein the tumor sample has a detectable expression level of PD-L1 in about 1% or more of the tumor cells in the tumor sample.

15. The method of claim 14 , wherein the tumor sample has a detectable expression level of PD-L1 in about 5% or more of the tumor cells in the tumor sample.

16. The method of claim 15 , wherein the tumor sample has a detectable expression level of PD-L1 in about 50% or more of the tumor cells in the tumor sample.

17. The method of claim 1 , wherein the subject is a human.

18. The method of claim 1 , wherein the antibody is a rabbit monoclonal antibody.

19. A method of detecting the presence or expression level of PD-L1 in a tissue sample from a human subject comprising contacting the tissue sample with an antibody that specifically binds PD-L1 and detecting the presence of the bound antibody, wherein:

(i) the antibody is a rabbit monoclonal antibody comprising a heavy chain variable domain (VH) sequence of SEQ g ID NO: 16 and a light chain variable domain (VL) sequence of SEQ ID NO: 17;

(ii) the expression level of PD-L1 is detected in tumor cells, tumor-infiltrating immune cells, or combinations thereof;

(iii) the detecting is by immunohistochemistry (INC); and

(iv) the tissue sample comprises formalin-fixed and paraffin-embedded (FFPE) tissue.

20. The method of claim 19 , wherein the IHC is processed with an automatic staining system.