'Tree-Hugger's Dream

SARA ENGRAM

January 03, 1993|By SARA ENGRAM

The approval this week of the new drug taxol brings a badly needed ray of hope for women who face long odds in their fight against ovarian cancer. It also demonstrates why the term "biological diversity" is more than a tree-hugger's dream.

Taxol, which has been called the most exciting new cancer treatment in 15 years, is notable for a number of reasons, not least of them the attention it has brought to environmental issues.

Derived from the bark of the Pacific yew tree, taxol is an example of the potential that lies in the wealth of plant and animal life around the world -- and the importance of preserving it.

Once routinely burned as scrub, the yew tree has become relatively rare, and that poses a problem.

The amount of yew bark needed to produce enough taxol to meet the demand is enormous: It takes about 60 pounds, roughly three mature trees, to produce enough of the drug to treat one patient.

Multiply that by the number of women with ovarian cancer who could benefit from taxol -- not to mention people with other forms of cancer that might also respond positively -- and the yew tree could be in serious danger of extinction.

Some environmentalists raised the alarm and, in fact, the Food and Drug Administration's unusually rapid approval of this drug would have come even faster had it not paused to draw up an environmental impact statement that provides what it describes as "moderate" protection for the yew tree.

But taxol offers environmentalists an opportunity almost as big as it has handed to cancer researchers. What better way to dramatize the importance of preserving the planet's natural wealth than to trumpet the life-enhancing potential found in a tree once regarded as useless?

Taxol's potential first came to light 30 years ago when scientists were conducting tests on extracts from randomly selected plants. Extracts from the yew tree killed all the cancer cells in a leukemia culture. From that small start, the potent substance was eventually isolated and named, but it took many more years for the National Cancer Institute to take an active interest.

FDA approval of taxol for treatment of ovarian cancer is especially significant for a disease that frequently goes undetected until it reaches advanced stages and becomes difficult to treat. Each year, about 21,000 women are diagnosed with ovarian cancer, and about 13,000 die. Taxol is not a cure, but it offers many women the hope of a longer life, where very little hope existed before.

But its promise extends to breast and lung cancer, as well as cancers of the head and neck. Researchers are also eager to see how it performs in combination with other drugs.

All this excitement is cause for celebration. But it also raises a question. How many other plants hold life-saving mysteries yet to be discovered? And how many of them are in danger of extinction? How many may have already been lost forever?

We human beings have always been prone to hubris, to the pride of thinking we can conquer all our enemies in a relentless march toward invincibility. But many diseases, like ovarian cancer, still elude us. And AIDS is a prime example of nature's ability to catch us unawares.

If the Earth produced the virus that causes AIDS, perhaps it also harbors the substances that will eventually provide a cure.

Many scientists worry that the AIDS threat could be dwarfed by the appearance of other viruses which could prove even more deadly. More than a few people are haunted by the possibility that somewhere in the world healing substances for AIDS and for other ills are slipping into extinction.

The original discovery of taxol sprang from a National Cancer Institute search for cancer treatments derived from natural sources, such as plants and sea creatures. But scientific efforts to tap the healing potential in nature have only scratched the surface of the Earth's biological diversity.

Environmentalists who worried that taxol could threaten the yew with extinction can rest easy. Bristol-Myers Squibb, which in a notable partnership between government and private industry has put top priority on developing the drug and seeking FDA approval, has said that within a year it will be well on the way to synthesizing the drug, and will end its reliance on yew bark by the end of 1995.

Once scientists discover how natural substances work, they can replicate the process. But as one scientist said about taxol, we could never have invented it. Only nature could have come up with something this complex.

Taxol should become Exhibit A in the cause to protect the inventions of nature still waiting to be found.

Sara Engram is editorial-page director for The Evening Sun.

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