The only prescription obesity drug currently approved for long-term use is Roche Holding AG’s Xenical, which got the FDA’s nod in 1999. GlaxoSmithKline markets a lower-dose, over-the-counter version called Alli. But both have their side effect issues, including liver problems and uncontrolled bowel movements, and provide only modest weight loss.

Qnexa, which combines the appetite suppressant phentermine and anti-seizure drug topiramate, helped patients lose at least 10 percent of their weight after a year of treatment, the company said.

FDA staff reviewers said patients taking the drug had more safety problems, including memory loss and higher heart rates, than those on a placebo, and some of these problems could get worse over time.

However, Vivus said the drug also reduced blood pressure, and a link between heart rates and heart health was not conclusive. Panelists called for the company to study whether a higher heart rate was tied to heart health.

“They need to step up to the plate and do the cardiovascular outcomes trial, and do it fast,” said panel member Dr. Sanjay Kaul, professor in the division of cardiology at Cedars Sinai Medical Center in Los Angeles. “I also encourage the FDA to hold their feet to the fire.”

FDA staff also noted that exposure to one of the ingredients in Qnexa has been linked to a higher rate of birth defects. A Vivus study showed topiramate caused a higher rate of oral clefts in infants of women taking the drug during pregnancy

The FDA has said the rate of potential birth defects is about two to five times higher with topiramate than with a placebo.

Vivus officials said obesity, and its common symptom diabetes, come with their own risks to pregnancy, such as stillbirth, premature birth and other complications.

Arena and Orexigen have been pitching their own fat-fighters to the FDA after rejections.

In February, Orexigen agreed with the FDA on the design of a 10,000-patient heart-safety trial required for the approval of its Contrave drug. The FDA rejected the drug pending the outcome of the trial, despite a 13-7 positive vote from a panel of FDA advisers.

The FDA is also set to review Arena’s lorcaserin by June 27, after rejecting it in October 2010 because of a potential cancer risk.

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By Anna Yukhananov

SILVER SPRING, Maryland