The discoverers won’t say exactly where the tree of life grows (in the ancient forests of the Pacific Northwest, wildcatters steal the rare yews for the taxol). But no one plans to get taxol by scraping fungus off bark anyway. The idea is to grow the fungus in huge fermentation vats, like the ones used for soy sauce, then separate out the taxol chemically. The cultures at MSU are pretty lethargic so far, yielding mere billionths of a gram of taxol. But microbiologist Arnold Demain of the Massachusetts Institute of Technology suggests they could increase the harvest by giving the fungus more oxygen, or by genetically engineering a better strain. And the Montana team notes that, in many fungi, some chemical in the host plant stimulates production of substances like taxol; if they can isolate such an “on” switch from yew bark, they’d have a natural fertilizer for their fungus.
Already four drug makers are hoping to win licensing rights from MSU. Among them: Bristol-Myers Squibb, which in 1991 negotiated a contract with the government to harvest and sell taxol from the Pacific yew. The firm is in the interesting position of negotiating rights to a process that, by increasing the availability of taxol and perhaps cutting the cost of obtaining it, could reduce the price of the drug. It costs as much as $2,958 for the three “treatment cycles” that the National Cancer Institute recommends to determine if the ovarian tumor is shrinking (thus far, the government has approved taxol only for ovarian cancer). If the drug is working, the patient could require three more cycles (treatment is free for poor patients). About 15,000 Americans receive taxol today; that could climb above 50,000 if the drug is approved for use against breast cancer.
Montana’s fungus isn’t the only challenger to Bristol-Myers’s yew trees. Chemists are synthesizing taxol from the needles of more common European yews, too. Policymakers no longer face the difficult choice of harvesting endangered yews or depriving cancer patients of their last hope. To the contrary: the Stierles found their wonder fungus-a species previously unknown to science-in one of those ancient forests that so often find themselves in the sight of timber firms.
