A drug used to treat a certain type of colorectal cancer that has mutations (changes) in genes involved in DNA repair. It is also used in some patients to treat cancer of the head and neck, Hodgkin lymphoma, melanoma, non-small cell lung cancer, renal cell carcinoma, urothelial carcinoma, and hepatocellular carcinoma. It is also being studied in the treatment of other types of cancer. Nivolumab binds to a protein called PD-1, which is found on T cells (a type of white blood cell). Nivolumab may block PD-1 and help the immune system kill cancer cells. It is a type of monoclonal antibody and a type of immune checkpoint inhibitor. Also called Opdivo.