The introduction of treatments with immune checkpoint inhibitors (ICIs), which target the CTLA-4 (Cytotoxic T-Lymphocyte Associated Protein 4) and PD-1/PD-L1 (Programmed Cell Death-1/Programmed Death-Ligand 1) pathways, among others, has been a breakthrough in the fight against cancer. The gene discussed is PDCD1; the disease is cancer.