In recent years, monoclonal antibodies targeting programmed cell death protein 1 (PD-1), programmed death ligand 1 (PD-L1), and cytotoxic T lymphocyte associated protein 4 (CTLA-4), hereinafter collectively referred to as immune checkpoints inhibitors (ICIs), have been added to the therapeutic arsenal and have revolutionized cancer management. The gene discussed is PDCD1; the disease is cancer.