The experimental diet drug Qnexa -- which combines the diet pill phentermine and the active ingredient in Topamax (topiramate), a drug used to prevent migraines and treat seizures -- produced an average weight loss of 26 pounds for patients completing a 24 week Phase II clinical trial, researchers reported on October 24th.

While preliminary highlights of the 200-patient trial conducted by Duke University Medical Center appeared in Diet Drug Report in May, further details were presented this week at the annual meeting of the North American Association for the Study of Obesity.

Patients treated with Qnexa who completed the trial lost on average 11.1 percent of their baseline body weight, compared to an average 2.8 percent in the placebo group, reported Dr. Kishore M. Gadde, Director, Obesity Clinical Trials Program, Duke University Medical Center.

Those in the Qnexa also saw had a mean reduction of 10 percent for cholesterol and 16.2 percent for triglycerides, while decreases in blood pressure were also observed.

These findings suggest that Qnexa may improve certain metabolic risk factors in obese patients as does Acomplia (rimonabant), the highly anticipatged diet drug currently awaiting action by the U.S. Food and Drug Administration.

The researchers said there were no dropouts among those treated with Qnexa for side affects, but said that adverse events occurring in greater than 10 percent of those treated with Qnexa included paresthesia (mild tingling of the extremities), altered taste and increased urinary frequency.

"Qnexa demonstrated significant weight loss and reduction in waist circumference in this study, coupled with excellent tolerability and a positive impact on certain factors pertaining to metabolic syndrome in obese patients," said CEO Leland Wilson of Vivus, Inc., developer of the drug.

But while the two active ingredients in Qnexa may have been individually approved by the FDA, Qnexa is hardly likely to make it to market anytime soon.

Phentermine, which is continues to be sold as a diet drug, was part of the diet drug combination Fen-phen that was pulled from the market in the 1990s when the combination was found to contribute to heart valve damage.

As for topiramate, Johnson & Johnson's patent covers weight-loss as well as the other indications for which Topamax currently is sold. While Vivus obviously is hopeful of avoiding patent issues, it is by no means a certainty