ML-309 is an inhibitor of mutant isocitrate dehydrogenase 1 (IDH1). It reversibly and selective inhibits IDH1R132H over wild-type IDH1 (IC50s = 96 and 36,500 nM, respectively). ML-309 reduces 2-hydroxyglutarate production in U87 MG glioblastoma cells (EC50 = 55 nM).