An orally bioavailable, selective inhibitor of PDGFRα, PDGFRβ, and FLT3 (IC50s = 11, 3.2, and 4 nM, respectively); also inhibits mutant forms of these kinases, including the D842V-containing form of PDGFR and D835Y and internal tandem duplication mutations of FLT3, at nanomolar concentrations.