New Diet Drug Attacks Craving Center

Finding the perfect pill, procedure, or injection to make people lose weight might sound as lofty a goal as genetically engineering a money tree.

Finding the perfect pill, procedure, or injection to make people lose weight might sound as lofty a goal as genetically engineering a money tree. But drug companies are still trying.

Yesterday the makers of a new weight-loss drug called Contrave announced their clinical trials actually exceeded the U.S. Food and Drug Administration's requirements to prove a weight loss drug's effectiveness.

People taking the drug lost an average of 8 percent of their body weight (around 17 pounds) within one year compared with people on the placebo, who lost an average of 1 percent of their body weight in a year.

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"This is the first drug, that I know of, that addressed the craving issue," said Dr. Dennis Kim, senior vice president of medical affairs and communications at Orexigen Therapeutics Inc., maker of Contrave.

"We have clearly cleared the hurdle, the efficacy benchmark, it's of course the FDA's judgment to see if it passes for safety," said Kim, who is also an assistant professor of medicine at University of California, San Diego.

The most common side effects included nausea, constipation and headache. The most severe side effects were one case of gall bladder infection and one person who had seizures. More than 3,000 people were included in the study, but around 40 percent of them dropped out of the trial.

Despite the success in terms of FDA efficacy standards, many obesity specialists voiced caution over the drug, or any weight loss drug.

"I have limited enthusiasm for pharmacotherapy to manage weight, and these results certainly don't change my view on the topic," said Dr. David Katz, associate professor Public Health at Yale University and expert in obesity. "The results are promising, although certainly less than dazzling."

Katz said he thought the Contrave results were "fairly consistent" with the success of other drugs for weight loss.

"Perhaps the single uniquely promising element here is that Contrave is a combination of two drugs long in use for other purposes, and thus likely to be at least relatively safe," Katz wrote in an e-mail to ABC News.

Contrave is the first drug to combine a anti-depression and smoking cessation drug called bupropion and naltrexone, prescribed to fight alcohol and opiate addiction.

Weight Loss Pill That Targets the Brain's Cravings

The point with Contrave, Kim said, isn't to increase metabolism but to block the craving in the craving-reward system in the brain.

"It's not so much the reaction to whatever you're doing, it's more the craving about those activities," said Kim, who added that because the drug targets craving and not reward that patients are less likely to experience diminished enjoyment in exercise or sex.

Other weight-loss drugs on the market also target the brain or central nervous system rather than the metabolism. For example Meridia (or sibutramine) works as an appetite suppressant by boosting chemical messages that tell the brain you're satisfied.

Based on the long-term outcomes of other weight-loss drugs that target the brain, Katz was cautious about the promise of Contrave.

"Weight is regulated by many pathways, and to date, efforts to turn off appetite along one pathway have resulted in compensation in others," he said.

Only time will tell for Contrave. With the FDA bar for efficacy out of the way, the makers of Contrave say they are about to seek FDA approval for the drug in early 2010, which is not guaranteed.

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