SU11248 is similar to Gleevec in the way it works. It is a small molecule inhibitor of the receptor tyrosine kinases PDGFRA, VEGFR, KIT and FLT3. For patients with KIT or PDGFRA mutations, the main targets of this drug are still KIT and PDGRFA. SU11248 also inhibits VEGFR. This provides an anti-angiogenic effect in addition to the primary anti-tumor effect. All tumors need new blood vessels (angiogenesis) in order for tumor growth to occur; treatments that block the growth of these new blood vessels are called “anti-angiogenesis” treatments.