Vatalanib (PTK787 or ZK-222584, cpg-79787 2HCl) 2HCl is a novel, potent and orally bioavailable inhibitor of VEGFR2/KDR with potential anticancer activity. In a cell-free experiment, it inhibits VEGFR2/KDR with an IC50 of 37 nM, is less effective against VEGFR1/Flt-1, and is 18-fold more potent against VEGFR3/Flt-4. With strong anti-proliferative activity in vitro and strong antitumor efficaciousness in vivo, it is an anilinophthalazine analog. The protein kinase domains of VEGFR 1 and 2 are bound by vatalanib, which then inhibits them. The PDGF receptor, c-Kit, and c-Fms are among the related receptor tyrosine kinases that this agent binds to and inhibits.