Sunitinib, a small molecule interfering with VEGF-R1 and VEGF-R2, PDGF α and PDGF β, KIT receptor, and Flt3 receptor [172], was FDA approved in 2006 and is currently used for the treatment of metastatic renal cell carcinoma and gastrointestinal stromal tumors [173]. Here, FLT1 is linked to gastrointestinal stromal tumor.