A half-strength version of the prescription weight-loss drug Xenical (orlistat) moved another step closer to becoming available over-the-counter when GlaxoSmithKline announced on April 7th that it had received an "approvable" letter for alli from the U.S. Food and Drug Administration.

An "approvable" letter means certain issues still need to be resolved prior to FDA action, and Steven L. Burton, vice president of weight control products for Glaxo, declined to elaborate on what was holding up FDA approval except to say the agency did not ask for additional human testing.

Burton said the company was entering discussions with the FDA to address its additional questions, and expressed optimism that alli (pronounced Al-EYE) could be in drugstores later this year, becoming the first FDA-approved diet drug product sold without a prescription.

Glaxo had previously been expressing optimism that alli would be on the market before mid-summer.

A request for more testing would have been a major surprise since Xenical has been available as a prescription drug since 1999. In that time, no major safety issues have surfaced.

But Xenical never became a blockbuster drug, largely because many who take it experience diarrhea, oily stools and flatulence because of fat that is excreted from the body rather than absorbed.

Two FDA advisory committees, following a Jan. 23rd meeting at which they heard arguments both for and against approving the over-the-counter version of Xenical, voted 11-to-3 in favor of non-prescription sale of the drug.

Members of the FDA advisory panels concluded unanimously that the proposed over-the-counter version helped patients lose an extra 5 to 6 pounds during the six months they would take it. They also voted 12-to-3 that the drug appeared generally safe, although some members voiced concerns about repeated and long-term use.

Glaxo has said alli could cost consumers $12 to $25 a week, and that an estimated 5 million to 6 million Americans a year would buy the over-the-counter drug.

Glaxo hopes to market alli as a prescription-quality alternative to unapproved diet supplements are sold in health-food stores, drugstores and over the internet. The company plans a marketing campaign for alli that will include extensive advice on dieting and exercise.

Another proposed weight-loss medication, Sanofi's highly touted Acomplia (rimonabant), received an "approvable" letter from the FDA in February. There have been no hints from Sanofi as to what issues remain to be resolved prior to further FDA action on Acomplia.