Over the past decade, immune checkpoint inhibitors—anti-programmed cell death-1 (anti–PD-1) antibodies (nivolumab, pembrolizumab) and anti-cytotoxic T-lymphocyte-associated antigen 4 (anti–CTLA-4) antibodies (ipilimumab)—have transformed melanoma care, with targeted therapies available for select patients with BRAF or KIT mutations. This evidence concerns the gene PDCD1 and melanoma.