It comes as no surprise but Sanofi-Aventis has withdrawn its marketing application to gain approval in the USA for its obesity drug Acomplia a month before the country’s regulators were more than likely to turn it down.

Sanofi’s decision comes a fortnight after the US Food and Drug Administration's Endocrinologic and Metabolic Drugs Advisory Committee voted 14-0 against approving Acomplia (rimonabant) in combination with diet and exercise, for the treatment of chronic obesity, or for people who are overweight with at least one risk factor for heart disease. The panel said that the benefits of the drug, which would have sold as Zimulti in the USA, do not outweigh the risk of psychiatric adverse effects seen in patients taking the drug, including suicide and seizures.

The committee’s damning verdict came as a huge blow to Sanofi which had previously hoped that Acomplia would be a $3 billion blockbuster. Those hopes have been dashed, at least in the short term, though confirming the withdrawal of its New Drug Application, the Franco-German drugmaker was fairly upbeat, saying that it is “confident in the positive benefit/risk ratio of rimonabant 20mg when used in the appropriate population”. Sanofi also noted that it is “committed to taking all step necessary” to get the drug on the US market and will “undertake the necessary discussions with the FDA “to determine the required modifications to its file”.

It seems that the best hope for getting Acomplia approved, though that is highly unlikely to happen this decade, lies in studies that Sanofi has been carrying out to try and show that the drug offers a particular benefit to patients with cardiometabolic risk factors - which predisposes a person to conditions such as diabetes. The firm has claimed that an estimated 50% of the observed improvements in HbA1c – a measure of blood glucose levels, triglycerides and high-density lipoprotein – in trials with Acomplia were “beyond that expected from weight loss alone” but these findings were recently questioned in a paper in the Drugs and Therapeutics Bulletin.

Acomplia is also up in front of the European Medicines Agency regarding ongoing safety monitoring of the drug which was approved in Europe in June last year and the findings of the review, for which Sanofi is submitting more data, will be made on July 19. The EMEA will look at the FDA panel’s concerns to see whether any further action is necessary, even though Acomplia’s label already carries a warning about psychiatric side effects and while suspension is highly unlikely, some label tightening in Europe seems certain.