To date, some immune checkpoint inhibitors (ICIs) have received FDA approval including blockers of PD-1 (nivolumab, pembrolizumab, and cemiplimab), PD-L1 (atezolizumab, avelumab, and durvalumab), and CTLA-4 (ipilimumab) for treating cancers, particularly metastatic melanoma, and nonsmall-cell lung cancer (NSCLC; Supplementary Table 2). Here, PDCD1 is linked to cancer.