paclitaxel, an anticancer drug derived from the bark of the rare, slow-growing Pacific yew tree. It is used in the treatment of ovarian cancer. Paclitaxel prevents cancer cells from dividing; it arrests cell division by attaching to microtubules that regulate the formation of spindles necessary for cell division. The anticancer effect of paclitaxel was discovered by the National Cancer Institute in 1963 during a routine investigation of thousands of plant compounds. It takes about 60 pounds of yew bark to produce enough paclitaxel to treat a single patient for several weeks. Semisynthetic and synthetic methods of production have reduced, but not eliminated, the use of yew bark.
