Atovaquone demonstrates evidence of anticancer efficacy against primary leukemic blasts and in patients with AML. (A) Primary leukemic blasts from 3 AML patients were obtained, pretreated with vehicle or atovaquone (25 µM) for 16 hours, and then treated with IL-6 (50 ng/mL) for 15 minutes followed by flow cytometric assessment of STAT3 phosphorylation. MFI, mean fluorescence intensity. Data are representative of 2 independent experiments. (B) The primary cancer cells described in panel A were treated with vehicle or atovaquone (25 µM) for 72 hours, after which viable cell number was assessed. Data are means ± standard deviation of 2 independent experiments. (C) Cumulative incidence of relapse of patients with AML following allogeneic HSCT (see text), classified as >55 days of atovaquone treatment within the first 150 days posttransplant (“high atovaquone”) or otherwise (“low atovaquone”). P value is 2-tailed using Gray’s test.