Ipilimumab, an antibody targeting the cytotoxic T-lymphocyte-associated protein 4, was the first treatment to show improved overall survival (OS) in metastatic melanoma in a randomised phase III trial,1 followed by programmed cell death protein 1 (PD-1) inhibitors with or without ipilimumab, and BRAF inhibitors with or without MEK inhibitors.2 The gene discussed is PDCD1; the disease is metastatic melanoma.