PDCD1 and neoplasm: Drugs targeting immune checkpoints, such as Cytotoxic T-Lymphocyte-Associated Protein 4 (CTLA-4), Programmed Cell Death Protein 1 (PD-1), and Programmed Death-Ligand 1 (PD-L1), can enhance the anti-tumor immune response and enable T cells to more effectively eradicate cancer cells.