The U.S. Food and Drug Administration appears to have put Sanofi's highly anticipated diet drug rimonabant (Acomplia / Zimulti) on a slow track and is now not expected to make a decision on whether to approve its sale in the United States until sometime next Spring, according to long-time FDA observers.

While the FDA never publicly comments on pending new drug applications, a variety of pieces of evidence which have accumulated over the past week strongly support the view that the FDA intends to take six months -- not the two months hoped for by Sanofi-Aventis -- to act on the company's Oct. 26th resubmission filing for Acomplia.

The tea leaves include:

• Sanofi has not offered even a hint about the notification it by law had to have received from the FDA as to whether the Acomplia resubmission would be subjected to a Class 1 (two-month) or Class 2 (six-month) review.

  Given that Sanofi has issued press releases twice in the past 10 days containing good news about Acomplia decisions made by tiny Sweden and Mexico, it defies belief that Sanofi would not reported good news -- if it had received any -- about Acomplia's prospects in the world's largest market.

• The FDA, meanwhile, published an updated meeting schedule for its advisory panels for the remainder of the year with no meeting scheduled for the Endocrinologic and Metabolic Drugs Advisory Committee -- the expert body that almost certainly will be asked to weigh the pros-and-cons of Acomplia prior to an FDA decision.

  While an optimistic reading of this would be that the FDA intends to approve Acomplia without hearing from its advisory panel on side-effect and safety concerns, that possibility -- never very realistic -- has been rendered far less likely by the next point.

• The FDA -- which continues to be under fire for approving drugs that later have to be taken off the market for safety reasons -- announced it has asked two of its expert panels whether the antibiotic Ketek should be allowed to remain on the U.S. market after reports of liver failure in a dozen patients.

The advisory panels will hold a two-day meeting on Ketek Dec. 14 and 15. Among those most critical of the FDA's handling of Ketek is the U.S. Senate Finance Committee, which is investigating allegations of fraud connected with the Ketek clinical trials.

The fact that the pharmaceutical company that manufactures Ketek is Sanofi-Aventis is certainly not a coincidence likely to encourage the FDA to speed another Sanofi drug with side-effect and safety issues to the market.

All this leads a number of FDA observers to suggest that a best-case scenario for Acomplia would not see the diet pill making it to the market in the United States before the middle part of 2007.

As for precisely what Sanofi has heard from the FDA, we once again have from the French pharmaceutical company what we have had so many times before: total silenc