On June 17, the FDA approved checkpoint blocker Keytruda (pembrolizumab, Merck & Co. Inc.) “for the treatment of adult and pediatric patients with unresectable or metastatic tumor mutational burden-high (TMB-H) [?10 mutations/megabase (mut/Mb)] solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options.”