To date, 6 MAbs against human PD-1 or PD-L1 have been approved by the Food and Drug Administration (FDA) for cancer immunotherapy: Pembrolizumab, Nivolumab, and Cemiplimab targeting PD-1, and Atezolizumab, Durvalumab, and Avelumab targeting PD-L1. Here, PDCD1 is linked to cancer.