Inhibitors of CTLA-4 (Ipilimumab), PD-L1 (Avelumab, Durvalumab, and Atezolimumab), and PD-1 (Cemiplimab, Pembrolizumab, and Nivolumab) have been approved by the FDA as therapeutic agents against various types of cancers (29). Here, PDCD1 is linked to cancer.