Discovery of Novel Benzimidazole and Indazole Analogues as Tubulin Polymerization Inhibitors with Potent Anticancer Activities

Abstract

Novel indazole and benzimidazole analogues were designed and synthesized as tubulin inhibitors with potent antiproliferative activities. Among them, compound <b>12b</b> exhibited the strongest inhibitory effects on the growth of cancer cells with an average IC₅₀ value of 50 nM, slightly better than colchicine. <b>12b</b> exhibited nearly equal potency against both, a paclitaxel-resistant cancer cell line (A2780/T, IC₅₀ = 9.7 nM) and the corresponding parental cell line (A2780S, IC₅₀ = 6.2 nM), thus effectively overcoming paclitaxel resistance <i>in vitro</i>. The crystal structure of <b>12b</b> in complex with tubulin was solved to 2.45 Å resolution by X-ray crystallography, and its direct binding was confirmed to the colchicine site. Furthermore, <b>12b</b> displayed significant <i>in vivo</i> antitumor efficacy in a melanoma tumor model with tumor growth inhibition rates of 78.70% (15 mg/kg) and 84.32% (30 mg/kg). Collectively, this work shows that <b>12b</b> is a promising lead compound deserving further investigation as a potential anticancer agent.