The experimental obesity drug Qnexa helped patients lose an average of 9.2 percent of their weight throughout a period of 28 weeks, developer Vivus Inc. announced.

Qnexa combines phentermine, which was half of the recalled anorectic fen-phen and the epilepsy drug Topamax (topiramate). Federal regulators decided to recall Fen-Phen diet pill due to the multiple reports of heart damage.

In the clinical trial, 756 obese people were given two different doses of Qnexa and placebo. Those taking the high and low dose of the drug for the 28-week follow-up reported an average 9.2 percent and, respectively, 8.5 percent weight loss, compared to a 1.7 percent weight loss for participants who were administered a placebo.

Results from the phase III “Equate” study showed that both doses of the obesity drug Qnexa met the primary endpoint and were considerably significant, Vivus said. This study is one of three late-stage clinical trials that the manufacturer plans to complete in 2009. After having all results, the company will file for U.S. Food and Drug Administration approval.

Qnexa appears to have been well-tolerated in the study. The most common adverse events patients reported were itching, altered taste, dry mouth, as well as constipation.

Obesity is known to be one of the leading preventable causes of death. Previous studies have showed that mortality risk varies with patient’s body mass index (BMI). According to health officials’ estimates, the condition causes an excess 111,909 to 365,000 death a year in the U.S.