Obesity Drugs Need Longer-Term Safety Data, Researchers Say

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drug safety Jan. 5 (Bloomberg) -- Weight-loss treatments need more study to prove they also help people live longer before doctors can be sure the benefits are greater than the risks and that the high cost is justified, researchers said in today's Lancet.

While drugs such as Roche Holding AG's Xenical and Abbott Laboratories' Meridia have proven to help patients lose weight, tests that show treatments save lives or cut deadly risks such as heart disease should be required, Raj Padwal and Sumit Majumdar of the University of Alberta Hospital in Edmonton said in the journal.

Roche, Abbott and France's Sanofi-Aventis SA already sell weight-loss products and the rising level of obesity around the world is attracting Pfizer Inc. and Merck & Co. Sedentary lifestyles and high-fat diets have caused the number of obese Americans to double over the past 30 years to around 31 percent of the population, according to the U.S. government. About 65 percent of the population is classed as overweight.

"The lack of cardiovascular morbidity and mortality endpoints in obesity drug trials represents a major gap in knowledge," the researchers said. "In our efforts to fill the therapeutic void that characterizes contemporary obesity management, the benefits of obesity pharmacotherapy must outweigh the risks and costs."

Not enough is known about the clinical causes of obesity to ensure the safety of drugs that patients may have to take for years, Padwal and Majumdar said.

"The neurobiology of obesity is extremely complex," the doctors said. "This complexity decreases the probability that targeting any single pathway will result in dramatic weight loss and suggests that multiple drugs with different mechanisms will be needed to produce significant and persistent weight loss."

Roche's Xenical and Abbott's Meridia are approved for long- term use, and work on different principles. Xenical, also known as orlistat, acts on the gut, preventing the absorption of fat. Meridia, also known as sibutramine, was developed as an anti- depressant and works by increasing chemicals in the brain that create a feeling of being full. Neither results in significant weight loss, and both have unpleasant side effects, including diarrhea and higher blood pressure. Xenical reduces weight by around 3 kilograms (6.6 pounds) on average, while Meridia results in a loss of 4 or 5 kilograms, the researchers said.

The newest obesity treatment, Sanofi's Acomplia, is available in Europe and is being reviewed by the U.S. Food and Drug Administration.

The medicine interferes with the system that controls many biological responses, including hunger pangs, bad memories and pain. Acomplia cuts food cravings by blocking so-called endocannabinoid receptors in the brain. Because these receptors are also present in other cells in the body, the drug can also reduce fat and blood sugar, treating other health risks associated with obesity, including diabetes.

"There are no definitive data showing benefit of one anti- obesity drug over another, and all three drugs are limited by modest efficacy and low rates of persistence with treatment," the Canadian researchers said. Because of this, the choice of treatment is largely based on patients' preference, they said.

In the absence of such data, obesity-drug trials should be designed to show that they have vital benefits beyond weight loss, the researchers said.

source - Bloomberg