Two PD-1 inhibitors have been approved by the FDA for the first-line treatment of metastatic melanoma (in September 2014 and January 2015, respectively): nivolumab (Opdivo®; Bristol-Myers Squibb, New York City, New York, USA) and pembrolizumab (formerly MK-3475 or lambrolizumab; Keytruda®; Merck, Kenilworth, New Jersey, USA). Here, PDCD1 is linked to metastatic melanoma.