PDCD1 and head and neck cancer: There are several drug administration (FDA)-approved ICIs targeting PD-1, including pembrolizumab and nivolumab, as well as those targeting PD-L1, including avelumab, atezolizumab, and durvalumab for melanoma, renal cell cancer, colorectal cancer [7], head and neck cancer [8], cervical cancer [9], urothelial cancer [10], and lung cancer [11].