PDCD1 and cancer: To date, monoclonal antibodies (mAbs) targeting PD-1 (e.g. Cemiplimab, Nivolumab, and Pembrolizumab) or PD-L1 (e.g. Durvalumab, Avelumab, and Atezolizumab) are approved by the United States FDA for the treatment of a series of malignancies [16, 36–38].