While Business Week magazine reports that Sanofi researchers "succeeded beyond their wildest dreams" in creation of Acomplia, the magazine reports in its December 27th issue that U.S. Food and Drug Administration approval of rimonabant for treatment of obesity and tobacco addiction "isn't a slam dunk."

"As the first in an entirely new class of drugs that affect a pleasure center in the brain, even the slightest hint of psychiatric side effects may lead regulators to demand more long-term safety data, potentially delaying Acomplia's launch beyond 2006 as planned," the magazine reports.

Acomplia is works by blocking receptors found in the brain and in fat tissue known as cannabinoid type 1 (CB1). While Sanofi contends that two-year trial data showed that side effects "mainly minor and short-lived," there are no long-term studies yet of the effects of interfering with this part of the brain.

And given the increased regulatory scrutiny of the FDA drug approval process following the recent withdrawal of Vioxx from the market and the current controversies over the safety of Celebrex, Bextra and antidepressants, Business Week says Sanofi "may find it needs to submit more data than anticipated to secure [FDA] approval."

There becomes even more likely in view of what Buisiness Week terms "a noticeable rate of withdrawal in Acomplia's clinical trials due to depression."

"There is reason for caution," Business Week concludes.

And it quotes Dr. Larry D. Sasich of Public Citizen's health research group -- an organization that is playing a lead role in demanding more FDA scrutiny of the safety of new drugs -- as saying: "There has never been a diet drug approved that has had more benefits than risks."

The battle over approval of Acomplia in the United States seems virtually certain to be intense indeed.