Ahead of the Bell: Canceled obesity drugs

On Wednesday, Pfizer and Sanofi-Aventis separately ended clinical testing of drugs that block the cannabinoid type 1 pleasure centers in the brain, part of a class of drugs called CB-1 antagonists that have come under scrutiny for psychiatric side effects. Pfizer said it decided its drug had little chance of gaining marketing approval.

"Pfizer decided to discontinue the program based on the negative global regulatory outlook for the risk/benefit profile of the CB-1 class of compounds," analyst John Boris wrote in a note to clients.

Boris said it was yet another disappointment for Pfizer and will make it harder for the company to post revenue growth. Boris had expected Pfizer's drug candidate to gain regulatory approval in 2011, the same year the patents on its cholesterol drug Lipitor expire. He'd projected sales of $675 million in 2015.

Sanofi-Aventis suspended European sales of its CB-1 antagonist, Acomplia, in October. Sanofi-Aventis cited Acomplia's "risk-benefit" profile and the requirements regulators were likely to make.

The Food and Drug Administration declined to approve Acomplia in 2007. Acomplia was once seen as a potential billion-selling blockbuster and a possible treatment for smoking, diabetes and high cholesterol along with obesity. But beyond obesity, approval in other ailments didn't occur and sales didn't develop.

Weeks before Sanofi-Aventis suspended European sales of Acomplia, Merck and Co. ceased development of a similar drug candidate called Taranabant. Merck said the drug was effective but its "overall profile" wouldn't work for obesity.