PDCD1 and cancer: Combination ICB (CICB) targeting both PD-1 and CTLA-4 has demonstrated synergistic antitumor activity preclinically1 and is now an approved standard of care for patients with diverse cancers, including melanoma2, clear-cell renal cell carcinoma3, non-small cell lung cancer (NSCLC)4, mesothelioma5 and hepatocellular carcinoma6.