PDCD1 and neoplasm: ICIs are monoclonal antibodies that target and inhibit either cytotoxic T lymphocyte antigen 4 (anti-CTLA4 as ipilimumab), programmed cell death-1 (anti-PD-1, as pembrolizumab, nivolumab), or its ligand PD-L1 (anti-PD-L1, as atezolizumab, avelumab and durvalumab), potentiating anti-tumor immune responses.