PDCD1 and cancer: Regarding immunotherapy delivery systems, these include checkpoint inhibitors, i.e., anti-PD1 (pembrolizumab, nivolumab, cemiplimab), anti-PDL1 (atezolizumab, avelumab, durvalumab), anti-PD1/PDL1 (AUNP12, under experimentation), and anti-CTLA-4 (ipilimumab) monoclonal antibodies, cytokines promoting lymphocyte activation, chimeric antigen receptor (CAR) and T cell receptor (TCR) engineered T cells, agonist antibodies against co-stimulatory receptor and cancer vaccines (9).