Obesity drug Contrave gets a new lease on life

9/22/2011 22:04:43 PM

We’re getting fatter, we don’t stick to diets or we gain the weight back lickety-split if we do --and meanwhile, where are the weight loss drugs?

They’ve been surprisingly hard to develop.

Now one drug that had faltered in the pipeline – Orexigen Therapeutics’ Contrave -- just got a new lease on life after being rejected for approval by the Food and Drug Administration in February. The FDA informed the company Tuesday that it will reconsider Contrave for approval if a clinical trial removes any concern about risks to the heart. The company said in a statement that the FDA’s requirements are “reasonable and feasible” and it plans to go ahead with the trial, which will take several years.

Contrave is a cocktail of two medications, naltrexone and bupropion. Both are already on the market.

Bupropion is the active ingredient of the antidepressant Wellbutrin and the anti-smoking aid Zyban. It increases the available levels of three key chemicals in the brain: dopamine, serotonin and norepinephrine.

Naltrexone blocks the receptors in the brain that opiate drugs attach to, and it’s used to treat people with addictions to heroin and other opiates. It’s also used to treat alcoholism. (A lot of the biology of addiction has to do with the opioid system in the brain, so this makes sense.)

The two drugs were combined as a weight-loss tool because bupropion increases the activity of key neurons in the brain (called POMC neurons), thus causing appetite to diminish and metabolism to rev up. Naltrexone was added to block a certain natural brain opioid that gets in the way of this stimulation.

Clinical trials showed that 50% of people taking the drug were able to lose 5% of their body weight over a year, compared with only 10% in a group that got a placebo. Based on this, in December, an advisory panel recommended –tepidly – that the drug combo be approved for treating obesity, as long as possible heart effects were closely tracked afterward.

But the FDA decided to reject Contrave because many people experienced slight increases in blood pressure or pulse rates. Because part of the reason to get people to lose weight is to help fight heart risks, negative effects such as these would seem to cancel out the gains.

A spate of FDA rejections of obesity drugs has gotten some obesity experts pretty upset, as you’ll see if you read this Dec. 13 article by staff writers Jeannine Stein and Shari Roan.

Clearly, the anti-obesity-drug effort has been tricky because many of the candidate meds have side effects, to say nothing of the fact that the body really doesn’t appreciate being in negative calorie balance and does what it can to stop the loss of fat. Weight loss even in people taking these drugs has been quite modest.

But the article also noted that “as drug after drug falters or falls by the wayside, doctors who treat obese patients are growing increasingly frustrated. They say that the agency’s standards for approving anti-obesity drugs are overly stringent and fail to recognize the health risks of carrying extra weight.”

And it quotes past-president of the Obesity Society, Dr. Donna Ryan, as saying at an obesity society meeting: “Everybody in the obesity field is upset. There is a lot of anger.”

Here’s a recent look at some candidate obesity drugs and where they were as of December. Another of the group, Qnexa, also may be getting a new lease on life: The FDA said earlier this month that it will allow its makers, Vivus of Mountain View, Calif., to resubmit the drug for approval for obese men and women who are ”of non-child-bearing potential.”

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