The discovery of novel indazole derivatives as tubulin colchicine site binding agents that displayed potent antitumor activity both in vitro and in vivo.

Tubulin inhibitors that bind to the colchicine site are widely studied anticancer agents. In continuous our researches, we designed a series of novel indazole derivatives as microtubule-targeting agents (MTAs). The structure-activity relationships (SARs) investigations indicated that a 3,4,5-trimethoxyphenyl moiety and a methyl or methoxy substitution were preferred for the better antiproliferative activity. The indazole derivatives 3c and 3f showed noteworthy low nanomolar potency against HepG2, HCT116, SW620, HT29 and A549 tumor cells. In mechanism studies, 3c and 3f were proved to target the colchicine site, inhibited tubulin polymerization and disrupted cellular microtubule networks, arrested HCT116 cell in G2/M phase and induced cell apoptosis. In the HCT116 xenografts mouse model, 3c and 3f suppressed tumor growth by 45.3% and 58.9% at an orally dose of 25 mg/kg without causing obvious weight loss. The indazole 3f may serve as a good lead or drug candidate for colorectal cancer therapy.