It looks like the end of the road for Sanofi-Aventis’ Acomplia after European regulators recommended the suspension of the controversial anti-obesity drug.

The European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) has concluded that the benefits of Acomplia (rimonabant) “no longer outweigh its risks” and says marketing authorisation should be suspended.

The CHMP said the new data from “post-marketing experience and ongoing clinical trials indicated that serious psychiatric disorders may be more common than in the clinical trials used in the initial assessment of the medicine”. It also believes that these psychiatric side effects “could not be adequately addressed by further risk minimisation measures”.

In addition, the CHMP noted that “the effectiveness of Acomplia…is more limited than was expected on the basis of the clinical trials, because available data indicate that patients generally take Acomplia only for a short period”.

Sanofi said it will comply with the EMEA’s recommendation for “the temporary suspension” for Acomplia, which has been marketed in 18 European Union countries since 2006. However the French drugmaker is nonplussed by the decision.

The firm says that the drug has provided “significant clinical benefits to patients suffering from obesity and overweight with associated co-morbidities”. More than 700,000 patients have been treated with Acomplia, which blocks cannabinoid type 1 receptors in the brain, and postmarketing surveillance of the drug show that the safety profile of the product “is consistent with the one observed during the clinical development”.

Sanofi quoted Robert Anthenelli, professor of psychiatry at University of Cincinnati as saying that “this first in its class medication continues to demonstrate great promise to reduce cardiometabolic risk and the pattern of side effects remains consistent across the randomised clinical trials conducted to date”.

He added that “as with any new drug category, more will be learned about optimising benefit and minimizing risk through continuing controlled use of the medication in different patient populations”. Prof Anthenelli noted that “while the pendulum has swung in the direction of extreme caution” with the EMEA’s decision, “at the end of the day, the medical community will allow the scientific process to unfold before rendering any final decisions about this medication’s ultimate therapeutic potential”.

Sanofi remains convinced that Acomplia “will remain an important therapeutic answer to a highly prevalent and increasing unmet medical need”. As discussed with the EMEA, it will continue “the ongoing clinical trial programme except Phase IV and is committed to provide additional evidence for the positive re-evaluation of the benefit/risk profile of Acomplia”.

However Sanofi’s enthusiasm is not shared by most observers. The likelihood of Acomplia becoming a blockbuster were dealt a shattering blow in June 2007 when a US Food and Drug Administration's advisory committee voted 14-0 against approval and Sanofi withdrew its application. Still the firm plans to re-submit the drug for US approval to treat diabetes in the fourth quarter of 2009.