CTLA4 and cancer: Myriad preclinical studies have shown that cancer vaccines used in combination with checkpoint inhibitors lead to significantly improved efficacy as compared with either treatment used alone,145 and now multiple clinical trials are ongoing evaluating this combination in patients.19 Among the most promising studies thus far, a phase I trial found that a GM-CSF cell-based vaccine (“GVAX”) in combination with ipilimumab, an anti-CTLA-4 antibody, enhanced the preexisting endogenous tumor-specific T-cell response compared to treatment with ipilimumab alone.