In the past years, the Food and Drug Administration (FDA) and European Medicines Agency (EMA) have approved several monoclonal antibody-based therapies targeting the immune checkpoint molecule programmed cell death receptor 1 (PD-1/CD279) or its ligand 1 (PD-L1/CD274) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4/CD152), based on large randomised clinical trials in e.g. melanoma 1-3, non-small cell lung cancer 4, 5 and renal cell carcinoma 6. The gene discussed is PDCD1; the disease is melanoma.