Design, synthesis, and biological evaluation of Indazole-based CA-4 analogues as tubulin polymerization inhibitors

Microtubules represent a clinically validated target for anticancer therapy. However, the clinical utility of existing tubulin inhibitors is frequently compromised by the emergence of drug resistance and systemic toxicities. Herein, we designed and synthesized a series of indazole-based Combretastatin A-4 (CA-4) analogues as potent tubulin polymerization inhibitors. Among them, SMU-G4 potently inhibited the proliferation of B16-F10 melanoma cells (IC₅₀ = 4 nM). Moreover, SMU-G4 significantly induced G2/M phase cell cycle arrest and triggered apoptosis, while effectively suppressing tumor cell migration in vitro. Most importantly, SMU-G4 demonstrated potent in vivo antitumor efficacy in a B16-F10 xenograft mouse model (TGI = 74.4%, 15 mg/kg) without inducing significant systemic toxicity or observable adverse effects. These findings suggest that SMU-G4, characterized by its novel scaffold and potent inhibitory profile, serves as a promising lead compound for the development of next-generation microtubule-targeting agents.