An inhibitor of mutant IDH1 (IC50s = 0.021 and 0.114 µM for IDH1R132H and IDH1R132C, respectively); selective for mutant IDH1 over wild-type IDH1 and mutant IDH2 (IC50s = 22.4, 27.3, and >100 μM for wild-type IDH1, IDH2R172K, and IDH2R140Q, respectively); inhibits production of 2-HG in U87 cells expressing mutant IDH1R132H, IDH1R132C, IDH1R132L, IDH1R132G, and IDH1R132S (IC50s = 0.009, 0.039, 0.042, 0.006, and 0.009 µM, respectively); reduces intratumor 2-HG levels in HCT116-IDH1R132H and HCT116-IDH1R132C mouse xenograft models at 12.5, 25, and 50 mg/kg