US approves key weight-loss pill

America's Food and Drug Administration (FDA) has approved a new weight-loss drug from Vivus that many doctors consider the most effective therapy in a new generation of anti-obesity pills designed to help patients safely shed pounds.

The agency cleared the pill Qsymia for adults who are obese or overweight and have at least one weight-related condition such as high blood pressure, diabetes or high cholesterol.

Patients taking Qsymia for a year lost 6.7% of their body weight in one study and 8.9% in another study, the FDA said. That was more than two other weight loss pill recently reviewed by the FDA.

Despite its impressive performance in clinical trials, Qsymia is not exactly a scientific breakthrough, and its development underscores the slow pace of research for obesity treatments.

The drug is actually a combination of two older drugs that have long been known to help with weight loss: phentermine and topirimate.

Phentermine is a stimulant that suppresses the appetite and has long been used for short-term weight loss. Topiramate is an anti-convulsant, sold by Johnson & Johnson as Topamax, that makes people feel more satiated after eating.

Researchers say the innovation of Qsymia lies in targeting multiple brain signals that drive people to overeat.

"We now know there are multiple pathways that determine how much energy we take in every day," said Dr Tim Garvey of the University of Alabama at Birmingham. "If you intervene on one pathway it's hard to make much of a difference, you really need to attack multiple mechanisms to get a pronounced effect."

Dr Garvey helped conduct several pivotal trials of the drug.

Qsymia is the second weight loss drug approved by the FDA in less than a month, following Arena Pharmaceutical's pill Belviq in late June. Previously the agency had not approved a new drug for long-term weight loss since 1999.