The FDA has approved monoclonal antibodies (mAbs) that target either PD-L1 (e.g., Avelumab, Durvalumab, and Atezolizumab) or PD-1 (e.g., Nivolumab, Cemiplimab, and Pembrolizumab) to treat a number of cancers [12–14]. Here, PDCD1 is linked to cancer.