As we approach the twenty-first century; we seem helpless to conquer the worst life-threatening diseases. Cancer strikes one in four and will claim the lives of one in six. Heart attacks kill more than 600,000 Americans annually. Each year, hypertension affects 58 million Americans; it is the third leading cause of death in this country. Across the globe, malaria, the scourge of the past, kills 1 to 2 million annually, mostly children. Many of the weapons we have used for centuries to fight these devastating diseases come from the plant kingdom. Plants contain novel compounds beyond the imagination of a chemist. New medicines derived from plants are discovered, like most medicines, in several ways: serendipity, screening, folklore, rational design, or a combination of these methods [see "New Medicines from Plants," THE WORLD & I, September 1988].
Three drugs with promising anticancer activity are racing to be added to the oncologist's armamentarium. Each has its origins in the investigative process, involving both serendipity and screening, leading to the discovery of its parent, camptothecin (CPT). This alkaloid was discovered in 1966 by Monroe Wall, who also discovered taxol, the drug derived from the Pacific yew that holds great promise against ovarian cancer.
One derivative, CPT-11, developed by Japan's Yakult Honsha Company, Ltd., has shown impressive activity against non-small-cell lung cancer, a difficult disease to treat. It is being tested in Japan and Europe.
A second, topotecan (hycamptamine), is being tested in clinical trials against lung, ovarian, breast, and colon cancers. The developer of the drug, the American pharmaceutical company SmithKline Beecham, is very excited about this new product.
The third, dubbed 9AC and made by Wall and his collaborator Mansukh Wani, is now in clinical trials because it is highly effective against drug-resistant human colon tumors implanted in mice.
The journey begins
The source of CPT is Camptotheca acuminata, a rare, rapidly growing tree commonly found along streams in the mild southeastern provinces of China. It reaches a height of 80 feet, has a trunk up to two feet in diameter, and is in a family, Nyssaceae, that has only two other genera. One contains a tree, native to eastern North America, known variously as the black gum, black tupelo, pepperridge, or sour gum; the other contains the dove tree of China, so named because the large white floral bracts suggest the shape of a dove. The genus of this tree, Davidia, was named after the French missionary Armand David, who botanized in China in the late 1800s.
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