In contrast to the Vinca alkaloids, paclitaxel and docetaxel induce assembly of microtubules and stabilize microtubule networks. Cells treated in vitro with paclitaxel form disorganized bundles of microtubules in all phases of the cell cycle. During cell division, paclitaxel induces the formation of many abnormal spindle asters. Cells are either arrested in mitosis or in G or S phases. Docetaxel has twice the potency of paclitaxel in inducing microtubule polymerization.
Treated cells accumulate in the mitotic phase of the cell cycle.
Their side effect profile is largely predictable from the mechanism of action. Normal body cells with a high turnover or with processes dependent on microtubule formation, such as white blood cells, gastrointestinal mucosa, neurons, and secretory cells are preferentially incapacitated to some degree by paclitaxel and docetaxel. Thsese effects are generally reversible and doses schedules have been developed to maximize tumor response and minimize side effects. These taxene compounds are and will continue to be important anticancer agents, particularly if supply problems are solved.