Pembrolizumab (KEYTRUDA®, Merck & Co., Inc., Kenilworth, NJ) is a humanized, mouse- derived anti-PD-1 antibody that promotes tumor-cell apoptosis by binding to T-cell PD-1 receptors and disrupting interaction with PD-L1 molecules on tumor cells [4, 5]. The gene discussed is PDCD1; the disease is neoplasm.