Immunotherapy with the humanized monoclonal antibodies nivolumab and pembrolizumab, which bind to the programmed cell death protein 1 (PD1) receptor, have become the new standard of care, achieving long durable responses in about 35–40% of metastatic melanoma patients, regardless of the BRAF mutation status [3,7,9]. The gene discussed is PDCD1; the disease is metastatic melanoma.