Therapeutic targeting of immune checkpoints such as programmed death-ligand 1 (PD-L1), programmed cell death protein 1 (PD-1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) with immune checkpoint inhibitors (ICIs) has revolutionised the treatment of advanced cutaneous melanoma as well as other tumour types over the past decade. The gene discussed is PDCD1; the disease is cutaneous melanoma.