The advent of immune checkpoint blockade (ICB) therapies, such as blockades of programmed cell death 1 (PD-1), programmed cell death-ligand 1 (PD-L1), or cytotoxic T-lymphocyte antigen-4 (CTLA-4), have revolutionized the treatment modalities of many cancer types [1]. The gene discussed is PDCD1; the disease is cancer.