PDCD1 and melanoma: Nivolumab (a fully human IgG4-blocking monoclonal antibody (mAb) against PD-1) was applied to the first-in-human trial of patients with advanced metastatic melanoma, colorectal cancer, castration-resistant prostate cancer, non-small cell lung cancer, and renal cell carcinoma in 2010, and first gained approval from the FDA to treat melanoma in 2014 (48–50).