Novel Potent Orally Active Multitargeted Receptor Tyrosine Kinase Inhibitors: Synthesis, Structure−Activity Relationships, and Antitumor Activities of 2-Indolinone Derivatives

The inhibition of receptor tyrosine kinases (RTKs) has become a successful approach in the development of anticancer agents. Many potent small-molecule kinase inhibitors have been discovered. We report herein a series of pyrrolo-fused-heterocycle-2-indolinone analogues as inhibitors of vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), and c-Kit. Among them, some pyrrolo-fused six- and seven-membered-heterocycle derivatives such as 9, 15, 23, and 25 are potent inhibitors of VEGFR, PDGFR, and c-Kit both enzymatically (<50 nM) and cellularly (<50 nM). Furthermore, compounds 9 and 25 possess favorable pharmacokinetic profiles and demonstrate good efficacies against human HT-29 cell colon tumor xenografts in nude mice. Further evaluations are in progress.