2​ Biological Activity Epothilone A is a new kind of microtubule function inhibitor with an IC50 of 4.4 nM for tubulin polymerization and cytotoxicity. It competitively inhibits [3H]-paclitaxel binding to microtubules. Epothilone A prevents cancer cells from dividing by interfering with tubulin, but in early trials epithilones have better efficacy and milder adverse effects than taxanes. Epothilone A exhibits kinetics similar to paclitaxel by inducing tubulin polymerization in vitro and producing enhanced microtubule stability and bundling in cultured cells. In contrast to paclitaxel, Epothilone A exhibits a greater cytotoxicity against P-glycoprotein-expressing multidrug resistant (MDR) cells (IC50 = 20 nM for MDR CCRF-CEM/VBL100 cells). [1][2] 3​ References Synthesis and Biological Activity of Novel Epothilone Aziridines† Alicia Regueiro-Ren,Robert M. Borzilleri,et al. ORGANIC LETTERS 2001;3:2693-2696 http://en.wikipedia.org/wiki/Epothilone http://en.wikipedia.org/wiki/Epothilone ; The pharmacological and toxicological properties of this product have not been fully investigated. Exercise caution in use and handling. This product must not be used in humans.