New Drug May Boost Weight Loss Efforts

Oct. 22, 2008 -- An experimental diet drug may prove to be twice as effective as currently available weight loss medications if results from an early study are confirmed.

Researchers did not compare the drug tesofensine head-to-head with currently approved weight loss medications. But researcher Arne Astrup, MD, of the University of Copenhagen tells WebMD that the weight loss in the study was roughly double that reported in trials of these drugs.

Danish biopharmaceutical company Neurosearch A/S, which hopes to market tesofensine as a weight loss drug, paid for the study.

"Normally the drugs now on the market give you at best a weight loss of 5 kilograms (11 pounds) with diet and exercise," Astrup says. "In this study we doubled that weight loss."

Tesofensine Targets Appetite Centers

Astrup says the drug works on three different appetite regulatory centers of the brain -- the neurotransmitters noradrenaline, dopamine, and serotonin.

The phase II study, reported today in The Lancet, included 203 obese patients whose average weight was about 220 pounds.

All the participants were placed on a calorie-restricted diet and all were asked to increase their physical activity to between 30 minutes to an hour a day.

Participants were treated with either a placebo, 0.25 milligrams of tesofensine, 0.5 milligrams of the drug, or 1 milligram of the drug daily.

In all, 161 of the participants completed the six-month study, with average weight loss ranging from a low of around 5 pounds in the placebo group to 28 pounds among patients taking the highest dose of the tesofensine.

But patients on the highest dose of the experimental drug also showed significant increases in blood pressure.

Because of this, patients who participate in a planned phase III study of the drug will be treated with the 0.5 milligram dose, which rivaled the higher dose in terms of weight loss in the phase II trial but elicited only a slight increase in pressure over placebo.

A spokeswoman for Neurosearch A/S tells WebMD that the phase III trials are planned for both the U.S. and Europe. Assuming the trials are positive, the company hopes to have the drug on the market within four years.

Checking the Drug's Safety

Thomas Wadden, PhD, who directs the University of Pennsylvania School of Medicine Center for Weight and Eating Disorders, tells WebMD that the phase III study should help answer important questions about the safety of the experimental weight loss drug.

"The phase II results are very promising, but larger studies are needed to confirm the findings and tell us more about the safety profile," he says.

Wadden says the blood pressure finding is particularly troubling, as was the finding that study participants treated with tesofensine reported more anger, hostility, and confusion than participants in the placebo arm of the study.

"We need to do more extensive assessment of the psychiatric effect of medications like this one that operate on the central nervous system," he says.