Discovery of polymethoxyphenyl-pyridines bearing amino side chains as tubulin colchicine-binding site inhibitors

• Nineteen new polymethoxyphenyl-pyridines were designed and synthesized. • 8j bearing a 4-methoxybenzyl aniline side-chain displayed the best activities against glioma. • 8o exhibited lower cytotoxicities for normal cells, but best antiproliferative activities. • 8o shows good tubulin polymerization inhibitory activity (IC 50 = 3.1± 0.5 µM). • 8o induced cell cycle arrest at the G2/M phase and cellular apoptosis. Nineteen TH03 analogues were designed and synthesized as tubulin colchicine-binding site inhibitors with potent antiproliferative activities. Among these compounds, 3,5-dimethoxyphenylpyridines 8j bearing a 4-methoxybenzyl aniline side-chain displayed the best antiproliferative activities against glioma (U87MG and U251). In addition, the trimethoxyphenylpyridine 8o bearing a 4-methyl-N-methyl aniline side-chain showed the best antiproliferative activities against colon carcinoma and lung cancer with the lowest IC 50 value (0.09 µM < IC 50 < 0.86 µM). Compared with CA-4, Compounds 8j and 8o displayed lower cytotoxicities toward normal cells but higher antiproliferative activities against PKO (IC 50 = 0.15 µM and 0.09 µM respectively), NCI-H1299 (IC 50 = 0.73 µM and 0.14 µM respectively), and A549 cells (IC 50 = 0.86 µM and 0.37 µM respectively). Further investigations revealed that 8o shows higher tubulin polymerization inhibitory activity (IC 50 = 3.1 ± 0.5 µM) than colchicine (IC 50 = 8.6 ± 0.2 µM), and induced cell cycle arrest at the G2/M phase and cellular apoptosis through disrupting the microtubule network.