Based on the results of two randomized, double-blind trials (CheckMate 069, CheckMate 067) combined immunotherapy with anti-cytotoxic T lymphocyte antigen-4 antibody (anti-CTLA-4) ipilimumab plus anti-programmed cell death protein 1 antibody (anti-PD-1) nivolumab was the first dual checkpoint blockade approved by the Food and Drug Administration (FDA) for the treatment of metastatic melanoma [2, 3]. The gene discussed is PDCD1; the disease is metastatic melanoma.