Taxane

Taxanes are diterpenes produced by the plants of the genus Taxus (yews), and are widely used as chemotherapy agents. Taxane agents include paclitaxel (Taxol) and docetaxel (Taxotere).

Taxanes present difficulties in formulation as medicines because they are poorly soluble in water.

Production
As their name suggests, taxanes were first derived from natural sources, but some have been synthesized artificially. Paclitaxel was originally derived from the Pacific yew tree. Taxanes are difficult to synthesize because of their numerous chiral centres — Taxol has 11 of these.

Mechanism of action
The principal mechanism of action of the taxane class of drugs is the disruption of microtubule function. Microtubules are essential to cell division, and taxanes stabilize GDP-bound tubulin in the microtubule, thereby inhibiting the process of cell division — a "frozen mitosis". Thus, in essence, taxanes are mitotic inhibitors. In contrast to the taxanes, the vinca alkaloids destroy mitotic spindles. Both taxanes and vinca alkaloids are, therefore, named spindle poisons or mitosis poisons, but they act in different ways. Taxanes are also thought to be radiosensitizing.