Following the US Food and Drug Administration (FDA) approval of nivolumab, an anti-PD-1 antibody for kidney cancer in 2015, other ICIs including ipilimumab (anti-CTLA-4), pembrolizumab (anti-PD-1), and avelumab (anti-PD-L1) were also approved in combinational use with other ICIs or axitinib (a VEGF receptor tyrosine kinase inhibitor)27. Here, PDCD1 is linked to kidney cancer.