Here's what I found on a quick google search:
http://www.drugdevelopment-technology.com/projects/rimonabant/
Under development by Sanofi-Aventis (formerly Sanofi-Synthelabo), Acomplia (rimonabant) is a selective CB1 endocannabinoid receptor antagonist indicated for the treatment of obesity. The drug, which has progressed to phase III development, 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 only endocannabinoid receptor antagonist in clinical development and thus offers a unique therapeutic approach to appetite control and weight reduction. The drug also has potential as a treatment for smoking cessation because the endocannabinoid system is also involved in the body's response to tobacco dependence.
On the back of successful clinical trials in overweight and obese subjects, Sanofi-Aventis filed for regulatory with the US FDA and European EMEA in April 2005. If approved, the company hopes to bring Acomplia to market in early 2006.