ATH686 (ATH-686) is a potent and selective, second-generation inhibitor of mutant FLT3 protein kinase; selectively kills leukemic cells harboring mutant FLT3 with no apparent effect on cells harboring wild-type FLT3, via inhibition of FLT3 kinase activity; potently inhibits cell proliferation of FLT3-ITD-Ba/F3 cells and D835Y-Ba/F3 cells (IC50<1 nM), via induction of apoptosis.