Drug for dry mouth may prevent lung cancer. (Pharmaceuticals).

A drug that has been prescribed for 30 years for a condition known as dry mouth can also stymie the formation of precancerous lung lesions in cigarette smokers, particularly those who have quit.

Solvay Pharma, a company based near Pads, markets the drug--anethole dithiolethione (ADT)--in several countries, including France and Canada, but has never sought regulatory approval for it in the United States.

ADT induces cells to make extra amounts of an enzyme that can detoxify cancer-causing chemicals in tobacco smoke and other environmental contaminants, say the researchers.

Pulmonologist Stephen Lam of the British Columbia Cancer Agency in Vancouver and his colleagues used a flexible, lighted scope to examine lung tissue and procure a sample of one precancerous lesion from each of 101 current and past smokers around age 40. The volunteers had smoked at least the equivalent of a pack a day for 13 years. After the exam, the volunteers received daily doses of either ADT or a placebo.

After 6 months, the researchers did a second round of tests on the lesion sampled in each person. This revealed that the lesion had progressed in 16 percent of the placebo group but only 7 percent of the ADT-treated participants, Lam says. Moreover, reexamination with the scope showed that 54 percent of the people getting the placebo had more or larger lesions compared with only 32 percent of participants getting ADT

Since ADT has been given to people for 30 years, "we can essentially retool an existing drug" to fight cancer, says molecular geneticist Frank J. Rauscher III of the University of Pennsylvania in Philadelphia.

ADT worked significantly better in former smokers than in current smokers. The drug and the enzyme it stimulates may be unable to keep up with the continuing assault of carcinogens on a smoker's lungs, Lam says.

Solvay biologist Marie-Odile Christen says the company is watching these new findings with interest. But Solvay won't decide before the end of this year whether it will embark on the massive trial that would be needed to secure U.S. approval of ADT for this use. --N.S.