It has been six months this week since GlaxoSmithKline received an "approvable" letter from the U.S. Food and Drug Administration for alli, a half-strength over-the-counter version of the prescription weight-loss drug Xenical (orlistat).

An "approvable" letter means certain issues still need to be resolved prior to FDA action, but Glaxo immediately 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.

That's the last encouraging news we have heard about alli. So what's the holdup?

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.

Neither Glaxo nor the FDA has given any indication as to the issues that need to be resolved prior to regulatory action on approval.

But Glaxo was sufficiently encouraged about the prospects for alli that it launched a weight-loss website in April that presumably will be a key part of its efforts to market the diet pill.

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.

Will we actually see the launch of alli, as Glaxo earlier forecast, before the end of the year?

Interestingly, alli is not the only weight-loss drug stalled at the FDA for unclear reasons.

A highly anticipated prescription weight-loss medication, Sanofi's 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.