The new diet drug rimonabant (Acomplia) helped people lose significantly more weight than a placebo in a two-year clinical trial, the largest of the studies of this drug conducted to date, according to researchers.

The study also showed that while most of the weight loss occured in the first year, continuing to take rimonabant was important to keeping the weight off. Trial participants who stopped taking the drug after one year regained the weight, while those who stayed on rimonabant kept it off, the researchers said.

Results from the two-year study entitled, Effect of Rimonabant on Weight Reduction and Weight Maintenance: RIO-NORTH AMERICA, were presented on November 9th at the American Heart Association's 2004 Scientific Sessions.

The eagerly awaited study showed that approximately one-third of patients who took a 20 mg dose of rimonabant daily for two years lost in excess of 10 percent of their initial body weight and almost two-thirds of the trial participants lost at least five percent of their body weight.

Equally important, much of the weight loss was of abdominal fat, which is widely viewed as a key indicator of cardiovascular risk.

Waist circumference of trial participants after two years was reduced by 3.1 inches for patients taking a daily 20 mg dose of rimonabant, by 1.9 inches for those taking a lower 5 mg dose, compared to 1.5 inches for trial participants taking a placebo.

Patients taking rimonabant also had significantly improved levels of HDL (good cholesterol) after two years, as well as lower triglycerides and improved insulin sensitivity, according to the researchers.

"I think you're getting a double whammy," said Dr. Xavier Pi-Sunyer, Chief of the Division of Endocrinology at Saint Luke's - Roosevelt Hospital Center in New York. "One is related to the weight loss and the other to the lipid improvement.

"The two-year results of the RIO-North America trial confirm that rimonabant is an innovative and promising tool for the long-term management of weight and associated cardiovascular risk factors in abdominally obese patients," he added.

The researchers also reported that rimonabant also proved to be safe and tolerable throughout the two year study period, with side effects "mainly minor and short-lived."

Side effects included a slightly higher incidence in depression, anxiety and irritability in the 20 mg group for those taking the higher dose of rimonabant compared to the placebo group. There was also a slightly higher prevalence of nausea.

The two-year results of study of 3,040 patients at 72 centers in the U.S. and Canada strongly support one-year data from European studies reported earlier this year, and appear to enhance the likelihood of Sanofi-Aventis winning regulatory European and U.S. regulatory approval.

For more details on results of the RIO-North America study, please CLICK HERE.