Two different series of fifty-two compounds, based on 3',4',5'-trimethoxyaniline (7a-ad) and variably substituted
anilines (8a-v) at the 7-position of the 2-substituted-[1,2,4]triazolo [1,5-a]
pyrimidine nucleus, had moderate to potent antiproliferative activity against A549, MDA-MB-231, HeLa, HT-29 and Jurkat
cancer cell lines. All derivatives with a common 3-phenylpropylamino moiety at the 2-position of the triazolopyrimidine scaffold and different
halogen-substituted
anilines at its 7-position, corresponding to 4'-fluoroaniline (8q), 4'-fluoro-3'-chloroaniline (8r), 4'-chloroaniline (8s) and 4'-bromoaniline (8u), displayed the greatest antiproliferative activity with mean IC50's of 83, 101, 91 and 83 nM, respectively. These four compounds inhibited
tubulin polymerization about 2-fold more potently than
combretastatin A-4 (CA-4), and their activities as inhibitors of [3H]
colchicine binding to
tubulin were similar to that of CA-4. These data underlined that the 3',4',5'-trimethoxyanilino moiety at the 7-position of the [1,2,4]triazolo [1,5-a]
pyrimidine system, which characterized compounds 7a-ad, was not essential for maintaining potent antiproliferative and antitubulin activities. Compounds 8q and 8r had high selectivity against
cancer cells, and their interaction with
tubulin led to the accumulation of HeLa cells in the G2/M phase of the cell cycle and to apoptotic cell death through the mitochondrial pathway. Finally, compound 8q significantly inhibited HeLa cell growth in zebrafish embryos.