A potent and selective inhibitor (IC₅₀ = 700 nM) of vascular endothelial growth factor receptor 2 (VEGFR 2) (also known as Flk1). Very weak inhibitor of PDGFR-kinase (IC₅₀ >50 µM), EGFR-kinase (IC₅₀ >100 µM)and HER-2 kinase (IC₅₀>100 µM). SU1498 has been shown to cause accumulation of phosphorylated ERK and inhibits its activity in vivo and in vitro by inhibition of ERK dephosphorylation.