As month after month passes with no sign of imminent FDA action on diet drug rimonabant (Acomplia / Zimulti), the most significant "wait loss" taking place is loss of the hugh lead Sanofi-Aventis once had in developing a novel approach to weight-loss based on blocking the CB-1 receptors in the brain.

A year ago, the French pharmaceutical company seemed likely to have several years where it would be alone in the multi-billion-dollar weight-loss market with a diet drug that produced highly promising results in clinical trials.

But today, both Merck and Co. and Pfizer have begun Phase III trials of rival CB-1 antagonists (we get excited reports of encouraging results from participants in these trials weekly), and Merck has said it plans to seek FDA approval for its diet pill next year.

Sanofi, meanwhile, maintains a sullen silence on where things stand with the FDA, which cannot be promising since as of Feb. 2, no meeting had yet been scheduled by the FDA advisory committee that almost surely will consider the pros-and-cons of Acomplia before the regulatory agency acts on approval.

"Sanofi has lost a fair amount of time,” Stephen Pope, head of equity research at Cantor Fitzgerald Europe in London, told Bloomberg news. "Once they finally get their act together, they may find that their clothes have been stolen."

While Acomplia has been on sale in some European countries since late last June, the situation there hasn't been all that encouraging since the largest nation where it is available, Germany, turned it down for insurance reimbursement, and the drug still hasn't made it to market in France and Italy.

The next opportunity for Sanofi management to shed some light on where it thinks it is headed with Acomplia comes on February 13th, when executives take questions from financial analysts following a briefing on the company's 2006 results.

If history is any guide, we are not likely to know much more on February 14th than we know today.