Several ICB inhibitors against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and/or programmed death-ligand 1 (PD-L1) have been approved by the FDA for the treatment of metastatic melanoma, advanced kidney cancer, metastatic non-small cell lung cancer, and unresectable or metastatic triple negative breast cancer [9,14,15]. This evidence concerns the gene PDCD1 and metastatic melanoma.