Rimonabant hydrochloride

Under development by Sanofi-Aventis, Acomplia (rimonabant) is a selective CB1 endocannabinoid receptor antagonist indicated for the treatment of obesity.

It works by blocking endogenous cannabinoid binding to neuronal CB1 receptors. Activation of these receptors by endoegenous cannabinoids, such as anadamide, increases appetite. It is the most advanced endocannabinoid receptor antagonist in clinical development and offers a novel therapeutic approach to appetite control and weight reduction.

The drug also has potential as a treatment for smoking cessation because the endocannabinoid system is involved in the body's response to tobacco dependence.

Acomplia (rimonabant) has been available in Europe since the middle of 2006, following regulatory approval by the EMEA in June 2006 for its use as an adjunct to diet and exercise for obese or overweight patients with associated risk factors, such as type 2 diabetes or dyslipidaeamia. However, it has had a less easy passage through the US regulatory system.

Filed for approval with the FDA in April 2005, it has encountered significant delays over the past two years. In February 2007, the company learnt that the FDA had extended their decision on whether or not to approve Acomplia by a further 3 months. Despite the repeated setbacks, analysts remain optimistic that it will eventually be approved in the US as an aid to weight loss.

Data from the World Health Organisation's MONICA project show that in some parts of Europe over 70% of men aged 55-64 years are clinically obese or overweight (BMI >25) and almost 70% of women in this age group. One in five of all Americans is obese and one in three overweight. Furthermore, increasing rates of childhood obesity are likely to exacerbate the trend towards increasing obesity in adulthood.