Design, Synthesis, and Evaluation of Indolinones as Triple Angiokinase Inhibitors and the Discovery of a Highly Specific 6-Methoxycarbonyl-Substituted Indolinone (BIBF 1120)

Inhibition of tumor angiogenesis through blockade of the vascular endothelial growth factor (VEGF) signaling pathway is a new treatment modality in oncology. Preclinical findings suggest that blockade of additional pro-angiogenic kinases, such as fibroblast and platelet-derived growth factor receptors (FGFR and PDGFR), may improve the efficacy of pharmacological cancer treatment. Indolinones substituted in position 6 were identified as selective inhibitors of VEGF-, PDGF-, and FGF-receptor kinases. In particular, 6-methoxycarbonyl-substituted indolinones showed a highly favorable selectivity profile. Optimization identified potent inhibitors of VEGF-related endothelial cell proliferation with additional efficacy on pericyctes and smooth muscle cells. In contrast, no direct inhibition of tumor cell proliferation was observed. Compounds 2 (BIBF 1000) and 3 (BIBF 1120) are orally available and display encouraging efficacy in in vivo tumor models while being well tolerated. The triple angiokinase inhibitor 3 is currently in phase III clinical trials for the treatment of nonsmall cell lung cancer.