Microtubule destabilizer that blocks tubulin polymerization (IC50 = 0.3 μM). Blocks cell cycle progression at metaphase and displays antitumor activity against a variety of malignancies in vitro (IC50 values ranging from 0.036 - 0.285 μM). Induces complete tumor remission in the Yoshida AH13 rat sarcoma model in vivo. Lacks neurotoxicity due to an ability to discriminate between posttranslationally modified tubulin in mature neuronal microtubules and less-modified tubulin present in immature neuronal or nonneuronal microtubules. Displays oral availability and efficacy towards MDR tumor cells.