CTLA4 and melanoma: In 2015, the combination of nivolumab (a monoclonal antibody against programmed cell death protein 1 [PD-1]) and ipilimumab (a monoclonal antibody against cytotoxic T-lymphocyte-associated protein 4 [CTLA-4]) became the first combination regimen to receive approval by the U.S. Food and Drug Administration (FDA) for the treatment of wild-type BRAF V600 melanoma.