CTLA4 and neoplasm: Since the approval of the first immune checkpoint inhibitor (ICI), ipilimumab (an anti-CTLA-4 monoclonal antibody (mAb)), for the treatment of unresectable and metastatic melanoma by the US Food and Drug Administration (FDA) in 2014, immunotherapy based on immune checkpoint blockers (ICBs) has been approved for the treatment of more tumor types in earlier disease stages.