The end of the road for diet drug Acomplia (rimonabant) was effectively reached on Nov. 5th when French drugmaker Sanofi-Aventis announced it was halting all further research on what it once expected to be the next blockbuster diet pill.

"It's over,'' Sanofi spokesperson Jean Marc Podvin told Bloomberg News.

More than 700,000 people around the world have taken Acomplia either as part of trials or during the time it was on sale.

Sanofi's decision to pull the plug on Acomplia came two weeks after it was advised by European regulators to suspend sales of the pill in the 18 European Union countries.

Acomplia was the first in what was to be a new class of diet drugs that worked by blocking CB-1 receptors in the brain -- the cannabinoid receptors believed to play a critical role in the regulation of food intake and energy expenditure.

While patients in clinical trials lost significant amounts of weight and saw improvements in a variety of risk factors associated with metabolic syndrome, the trials also had a high drop out rate by participants who suffered a variety of worrisome side-effects.

The U.S. FDA never approved rimonabant, which was to have been sold in the United States under the name Zimulti, citing concerns over psychiatric side-effects including suicidality. But Acomplia was approved for sale in Europe in 2006 and had been on the market there for more than two years.

The European Medicines Agency said in October, however, that it had concluded the risks of depression, anxiety and stress disorders outweighted Acomplia's weight-loss benefits, and recommended that it be withdrawn from the market.

Sanofi halted sale of the drug in Europe, but the company said it remained "committed to Acomplia" and vowed to continue with clinical trials exploring its use in treatment of diabetes and cardiovascular disease.

Sanofi's position on the trials, which involved some 24,000 people worldwide, changed after France and Germany announced that they would not permit a continuation of these trial in those countries.

Sanofi announced in a terse statement that it did not even post on its website it was stopping ongoing human testing of Acomplia, for all uses, "in light of recent demands by certain national health authorities."

"As a result the feasibility of the global clinical development programme has been compromised," Sanofi said.

Four years ago, Sanofi was touting Acomplia as a wonder drug that not only would help people lose weight but also quit smoking, stop abusing alcohol and drugs, lower their cholesterol, control blood sugar and and improve a variety of cardiometabolic risk factors.

But after evidence began accumulating of the drug's psychiatric side-effects, including an increase in suicidality, opposition began to build. While the drug was approved for sale in 38 countries in Europe, Latin America and Asia, it was never marketed in many of these countries.

Just over a month ago, Merck & Co. announced that it was halting development of a similar experimental antiobesity drug taranabant, which also acted on CB-1 receptors, because of concern over side-effects.