Development of Combretastatin A-4 Analogues as Potential Anticancer Agents with Improved Aqueous Solubility

Combretastatin A-4 (CA-4) is a potent tubulin polymerisation inhibitor. However, the clinical application of CA-4 is limited owing to its low aqueous solubility and the easy conversion of the olefin double bond from the more active cis- to the less active trans-configuration. Several structural modifications were investigated to improve the solubility of CA-4 derivatives. Among the compounds we synthesized, the kinetic solubility assay revealed that the solubility of compounds containing a piperazine ring increased the most, and the solubility of compounds 12a1, 12a2, 15 and 18 was increased 230–2494 times compared with that of the control compound (Z)-3-(4-aminophenyl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile (9a). In addition, these synthesised stilbene nitriles had high anticancer cell (AGS, BEL-7402, MCF-7, and HCT-116) selectivity over L-02 and MCF-10A normal cells while maintaining micromolar activity against cancer cells. The most cytotoxic compound is 9a, and the IC50 value is 20 nM against HCT-116 cancer cells. Preliminary studies indicated that compound 12a(1) had excellent plasma stability and moderate binding to rat plasma proteins, suggesting it is a promising lead compound for the development of an anticancer agent.