One of the lead researchers in the largest North American clinical trial of diet drug Acomplia (rimonabant) claimed in a CBS interview on November 29th that he has absolutely no idea why action on the highly anticipated diet pill remains stalled at the U.S. Food and Drug Administration.

Dr. Louis J. Aronne, who in presentations on the results of the RIO-North America rimonabant trial has emerged as one of the most enthusiastic supporters of Acomplia, was asked by a CBS interviewer what the main concerns are behind the FDA's delay in approving the weight loss drug.

"I just can't tell you," Aronne said. "Nobody knows what the FDA is looking at. That's all secret."

Aronne, director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital, was one of three doctors listed along with two Sanofi-Aventis researchers who reported in the Journal of the American Medical Association on their analysis of the RIO North America trial.

Data from this trial and three other studies formed the core of the material Sanofi presented to the FDA in seeking approval to market the drug in the United States.

Since Sanofi clearly knows what issues the FDA is looking at, Aronne's profession to know nothing about the FDA's concerns struck some observers as a bit curious.

Many believe one of the outstanding issues at the FDA is the question of Acomplia's side effects, particularly since no previous drug has been approved that acts on the cannobinoid receptors in the brain. But in the CBS interview, Aronne was dismissive of concerns about side-effects of Acomplia.

While he noted that nausea, dizziness, anxiety and a depressed mood were seen among some participants in the clinical trials, he asserted that "these were relatively uncommon compared to other treatments we have had in the past.

"They go away when the pill is stopped," Aronne said. "We found this was a very tolerable treatment."