Immune checkpoint inhibition for the treatment of mesothelioma.

Single agent anti-CTLA4 blockade is inactive in mesothelioma. Single agent PD-1 blockade as second or subsequent treatment gives 20-29% partial responses; no randomized comparisons against placebo or chemotherapy are available. Biomarkers of response have been difficult to identify. There is no consensus as to whether tumor PD-L1 expression predicts outcomes. Combination checkpoint inhibitors (CTLA4 and PD1 blockade) provide a small incremental increase in response rates and progression-free survival. Chemoimmunotherapy is the next frontier.