PDCD1 and neoplasm: Currently, numerous ICIs, such as anti-PD-1 (nivolumab or pembrolizumab), anti-PD-L1 (atezolizumab, avelumab, or durvalumab), and anti-CTLA-4 (ipilimumab or tremelimumab) antibodies, can activate the anti-tumor immune response and inhibit the growth of tumor cells (Weyand et al., 2018).