CTLA4 and cancer: Although immune checkpoint blockers (ICBs) such as anti-CTLA-4 antibody ipilimumab, anti-PD-1 antibodies nivolumab and pembrolizumab, and anti-PD-L1 antibody atezolizumab have been evaluated in the treatment of many different cancers [7], ICB therapy works only on certain types of cancers.