Immune checkpoint inhibitors (ICIs), such as anti-programmed cell death protein-1 (PD-1) and anti-programmed cell death ligand-1 (PD-L1) agents, have been approved for the treatment of various cancers, including non-small cell lung cancer (NSCLC), advanced melanoma, urothelial carcinoma, and hepatocellular carcinoma, among others (1). Here, PDCD1 is linked to cancer.