CTLA4 and cancer: Cancer immunotherapy, one of the key scientific breakthroughs against cancer, was pioneered by targeting T cell coinhibitory immune checkpoint inhibitors (ICIs), with U.S. Food and Drug Administration–approved therapies including anti-CTLA-4 (ipilimumab) and anti–PD-1 (nivolumab) for melanoma in 2011 and 2014, respectively (1).