Novel cyanocombretastatins as potent tubulin polymerisation inhibitors

A series of novel cyanocombretastatins bearing a 3,4,5-trimethoxyphenyl moiety combined with a variety of substituted phenyl rings, were synthesised and their antitumour activity was evaluated. The Z-cyanocombretastatins were synthesised in a one-step protocol in high purity and yield. Fluoro, bromo, iodo, and derivatives with boronic acid and an ethyne function at meta position of the B ring were synthesised. In vitro MTT bioassays against human chronic myelogenous leukaemia (K562) and transfected breast adenocarcinoma (MDA NQO1) cell lines, revealed promising IC50 inhibitory values in nanomolar range (<50 nM). Introduction of a nitrile function on the olefinic bond not only increased the cytotoxicity of the less active Z-isomers but rendered the analogues as moderate to potent inhibitors of tubulin polymerisation comparable to that of CA-4 (IC50 = 2.2 μM).