ANALYSIS-New obesity drug uses old approach for big results

* Vivus drug caused major weight loss in human trials

* Works by affecting both behavior and metabolism

* About 60 percent of U.S. adults are overweight or obese

WASHINGTON, Sept 9 (Reuters) - Qnexa, an experimental obesity drug, helped people lose an average of nearly 15 percent of their body weight by combining an older weight-loss drug with an epilepsy drug, corporate researchers said on Wednesday.

The stunning result from Mountain View, California-based Vivus Inc


shows it may not require breakthrough approaches to drug design to help the most severely obese people lose enough weight to improve their health -- although it remains to be seen how long they can keep the weight off [ID:nN09205479].

It also suggests that tackling obesity from two directions -- by altering both behavior and biology -- can pay off.

Many researchers have tried to tackle the problem of obesity, attacking hormones such as leptin and ghrelin, brain chemicals such as neuropeptide Y and even trying to stop the body from absorbing nutrients.

One big problem, however, is human behavior. Drugs can speed up metabolism, suppress appetite and even prevent the body from absorbing fat. But some people will gorge themselves even when they are full.

Vivus bet that it could improve on the notorious "fen-phen" combination pulled off the market in 1997 after it was found to damage the heart and cause sometimes fatal cases of pulmonary hypertension.

Fen-phen combined fenfluramine and phentermine. Phentermine, a stimulant now available generically, appears safe and is used in the new Vivus drug Qnexa.

Fenfluramine, once sold by companies now a part of Wyeth


under the brand names Redux and Pondimin, could damage heart valves, causing fluid to build up -- the main symptom of pulmonary hypertension. Wyeth is still settling lawsuits from patients who said they were injured by the combination.


Vivus, whose shares shot up nearly 80 percent on the news, combined phentermine with the epilepsy drug topiramate, available generically and sold by Johnson & Johnson's


Ortho-McNeil unit under the brand name Topamax.

Phentermine takes an old-fashioned and logical approach to weight loss -- it is a stimulant that speeds up the metabolism. Topiramate, an anti-convulsant, has been shown to interfere with binge eating and studies show it can help patients lose weight and lower their blood pressure.

A trial of 1,267 morbidly obese patients showed those who took the highest dose lost an average of 37 pounds (17 kg) or 14.7 percent of their body weight over a year, compared to patients who took a placebo and lost 2.5 percent.

Another group of patients lost 13 percent and those taking a lower dose lost 10 percent.

Losing just 10 percent of body weight is enough to lower cholesterol, reduce the risk of diabetes and death. About 60 percent of U.S. adults are overweight or obese and about 9 million are morbidly obese, with a body mass index above 40.

The U.S. National Institutes of Health says people who are obese, with a BMI of 30 or more, have a 50 to 100 percent higher chance of dying of anything but especially heart disease in any given time period, compared to people of healthy weight.

A person six feet (1.83 metres) tall has a healthy BMI of 25 at 184 pounds (83 kilograms) but becomes obese, with a BMI of 30, at 221 pounds (100 kg) and morbidly obese at about 300 pounds (136 kg). (Editing by Eric Walsh)