An experimental diet drug seems to help some obese people shed pounds, and keep them off for two years, researchers report.
The drug, which will be called Qnexa if it reaches the market, is a combination of the appetite suppressant phentermine and the anti-seizure drug topiramate.
So far, it's had a bumpy road to approval. Last year, the Food and Drug Administration (FDA) rejected Qnexa, citing safety concerns -- including elevated heart rate in some users and the potential for birth defects if pregnant women used the drug.
But last month, the FDA accepted a new application from Qnexa maker Vivus Inc., which is now seeking approval for the drug to be marketed with a warning that it shouldn't be used by women of childbearing age.
The new study, reported in the American Journal of Clinical Nutrition, is an extension of an earlier clinical trial. That one found that Qnexa, added to lifestyle changes, helped obese adults lose more weight over one year, versus placebo pills.
The current study suggests that the benefit lasts for two years, according to researchers led by Dr. W. Timothy Garvey of the University of Alabama at Birmingham.
That compared with a two percent decline among 227 people given a placebo.
Qnexa users also showed a decline in obesity-related health problems. On average, their blood sugar and insulin levels dipped, and they were less likely than placebo users to develop diabetes.
Almost four percent of the placebo group developed diabetes per year. By comparison, just under two percent of people on a lower Qnexa dose developed diabetes each year, as did one percent of those on a higher dose.
Whether the diet drug will actually become available is still up in the air.
Qnexa and two other weight-loss drugs -- Arena Pharmaceuticals' lorcaserin and Orexigen Therapeutics' Contrave -- were all rejected by the FDA in the past year over potential safety concerns.
All three companies, though, are still working on addressing the FDA's concerns to try to win approval.
Drugmakers have struggled for years to develop weight-loss drugs that are both effective and safe.
Back in 1997, the infamous diet drug "fen-phen" was pulled from the market after reports of fatal heart-valve problems in some users. Another diet pill, Meridia, was pulled from the U.S. market last year after being linked to heart problems.
In this latest Qnexa trial, the most common side effects were upper respiratory infections, constipation, dry mouth and tingling sensations. Over two years, 3 percent of placebo users and about 4.5 percent of Qnexa users dropped out of the trial because of side effects.
For now, the drug options are few for obese people who fail to lose weight through diet changes and exercise alone.
The only drug approved for long-term use is orlistat (Xenical), which is also available as a lower-dose, over-the-counter version called Alli. But Xenical has its issues as well, including side effects of gas, uncontrolled bowel movements, and cases of serious liver problems.