Mechanistically, ICIs block the binding of checkpoint proteins (i.e., programmed cell death protein 1 [PD‐1] and cytotoxic T‐lymphocyte‐associated protein 4 [CTLA‐4]) to their ligands (i.e., programmed cell death protein ligand 1 [PD‐L1] and CD80/CD86, respectively), resulting in immune cell activation and attack of the cancer cells [5]. The gene discussed is PDCD1; the disease is cancer.