PDCD1 and cancer: The US Food and Drug Administration (FDA) has approved three distinct categories of ICIs for treating various cancer types: CTLA-4 inhibitors (Ipilimumab), PD-L1 inhibitors (such as Atezolimumab, Avelumab, and Durvalumab), and PD-1 inhibitors (including Pembrolizumab, Nivolumab, and Cemiplimab).