Since the approval of ipilimumab, a humanized cytotoxic T-lymphocyte associated antigen 4 antibody (anti-CTLA-4) in 2011, pembrolizumab and nivolumab (both targeting programmed cell death protein 1 [anti-PD-1]), as well as combination therapy (ipilimumab/nivolumab) have been shown to prolong progression-free survival and were approved for treatment of stage 4 melanoma. 1 Here, PDCD1 is linked to melanoma.