Design, Synthesis, and Biological Evaluation of 1‑Methyl-1,4-dihydroindeno[1,2‑<i>c</i>]pyrazole Analogues as Potential Anticancer Agents Targeting Tubulin Colchicine Binding Site

By targeting a new binding region at the interface between αβ-tubulin heterodimers at the colchicine binding site, we designed a series of 7-substituted 1-methyl-1,4-dihydroindeno­[1,2-<i>c</i>]­pyrazoles as potential tubulin polymerization inhibitors. Among the compounds synthesized, 2-(6-ethoxy-3-(3-ethoxyphenylamino)-1-methyl-1,4-dihydroindeno­[1,2-<i>c</i>]­pyrazol-7-yloxy)­acetamide <b>6a</b> and 2-(6-ethoxy-3-(3-ethoxyphenylamino)-1-methyl-1,4-dihydroindeno­[1,2-<i>c</i>]­pyrazol-7-yloxy)-<i>N</i>-hydroxyacetamide <b>6n</b> showed noteworthy low nanomolar potency against HepG2, Hela, PC3, and MCF-7 cancer cell lines. In mechanism studies, <b>6a</b> inhibited tubulin polymerization and disorganized microtubule in A549 cells by binding to tubulin colchicine binding site. <b>6a</b> arrested A549 cells in G2/M phase that was related to the alterations in the expression of cyclin B1 and p-cdc2. <b>6a</b> induced A549 cells apoptosis through the activation of caspase-3 and PARP. In addition, <b>6a</b> inhibited capillary tube formation in a concentration-dependent manner. In nonsmall cell lung cancer xenografts mouse model, <b>6a</b> suppressed tumor growth by 59.1% at a dose of 50 mg/kg (ip) without obvious toxicity, indicating its in vivo potential as anticancer agent