Immune checkpoints that target the programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) have received approval across a wide range of cancer types, including lung cancer, melanoma, and head and neck, among others [16]. The gene discussed is PDCD1; the disease is melanoma.