PDCD1 and cancer: These immune checkpoint pathways have emerged as promising targets for cancer immunotherapy, with the development of monoclonal antibodies against PD-1 (e.g. nivolumab, pembrolizumab), PD-L1 (e.g. avelumab, atezolizumab, durvalumab) and CTLA-4 (e.g. ipilimumab) showing clinical efficacy in the treatment of various cancers [93, 95].