In addition to the nonspecific immunotherapies, three immune checkpoint modulators, ipilimumab (anti-cytotoxic T-lymphocyte associated antigen 4 [CTLA-4]), nivolumab (anti–programmed cell death protein 1 [PD-1]), and pembrolizumab (anti–PD-1), have been approved for the treatment of melanoma [19]. The gene discussed is PDCD1; the disease is melanoma.