BATTLE WEARY

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Taxol is now being produced from the leaves of other yew species, collected in India and Europe, as well as from the bark of the Pacific yew. In its ­efforts to respond to the Taxol supply crisis, NCI learned an important lesson about the need for close communication between ­organiza­tions responsible for drug procurement and clinical investigators. In the future, NCI plans to initiate ­exploration into large scale-up of raw material production as soon as antitumor activity has been confirmed in a substance.

Madagascar periwinkle

Madagascar periwinkle (Catharanthus roseus, formerly Vinca rosea) has been a major source of chemotherapeutic agents for the past thirty years. Native to Madagascar, it is now a cosmopolitan weed in tropical regions and is widely grown as an attractive ornamental. In the early 1960s, researchers in Canada and the United States, working independently, became interested in the plant based on its folk use in diabetes. They discovered a large number of alkaloids that demonstrated anticancer activity in animal experiments. More than seventy different alkaloids, some of which are known to stop cell division in cancer cells, have since been isolated. Two of them, vinblastine and vincristine, were further developed as chemotherapy drugs and came into the market in the mid-1960s. In combination with other drugs, vinblastine is used to treat Hodgkin’s disease and other cancers. Vincristine is used to treat acute leukemia and, in combination with other drugs, Hodgkin’s disease and Wilms’ tumor. In 1984, a semisynthetic derivative of vinblastine, vindesine, became available for use in patients resistant to vincristine and vinblastine. The discovery of the two major anticancer alkaloids from the Madagascar periwinkle has sparked further research into plant-­derived cancer treatments.

The story of two folk remedies

Several other plant compounds are in clinical trials, and time will tell whether they will result in new drugs. Success in the NCI’s natural products branch has been slow in coming. With the advent of new technologies and collaboration with researchers through­out the world, the development of other plant-derived cancer drugs is probable. Because the search for new conventional cancer treatments is long and tedious, individuals diagnosed with cancer continue to seek out alternative therapies, with mixed results. The following are two examples of widely used folk cures whose reputation has not stood up in the laboratory.

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