In fact, nivolumab and pembrolizumab, both of which are antagonistic antibodies to PD-1, were recently approved by the Food and Drug Administration (FDA) to treat advanced melanoma and non-small-cell lung cancer.14, 15, 16, 17 Most recently, an early-phase clinical trial using nivolumab in relapse/refractory Hodgkin's lymphoma reported positive results.39 Importantly, adverse effects of these agents are minimal. This evidence concerns the gene PDCD1 and melanoma.