Immune checkpoint inhibitors are monoclonal antibodies that most commonly target cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed cell death protein-1 (PD-1), or its ligand (PD-L1) by inhibiting the suppression of T cell activity and re-enabling the immune system to attack tumor cells (12). Here, PDCD1 is linked to neoplasm.