A potent antagonist of the type III receptor tyrosine kinases PDGFRβ, FLT3, and c-Kit (IC₅₀ = 200, 220, and 170 nM, respectively); less potently inhibits CSF-1R (IC₅₀ = 3.4 µM) and does not significantly inhibit other tyrosine or serine/threonine kinases.