updated 11/5/2008 6:17:31 PM ET 2008-11-05T23:17:31

French drugmaker Sanofi-Aventis said Wednesday it is halting all research on a diet drug sold in Europe, Acomplia, and rival Pfizer Inc. hours later said it is ending research on an experimental weight-loss drug in the same class.

  1. Don't miss these Health stories
    1. Splash News
      More women opting for preventive mastectomy - but should they be?

      Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

    2. Larry Page's damaged vocal cords: Treatment comes with trade-offs
    3. Report questioning salt guidelines riles heart experts
    4. CDC: 2012 was deadliest year for West Nile in US
    5. What stresses moms most? Themselves, survey says

Both drugs work by blocking the pleasure centers that give marijuana smokers the "munchies" — the cannabinoid type 1, or CB1, receptors.

Given that obesity and related complications are arguably the world's biggest public health problem, the demise of both drugs will be a big disappointment for patients and doctors, and possibly for investors. The decisions leave New York-based Pfizer, the world's top drugmaker by sales, and Paris-based Sanofi-Aventis, ranked No. 4, suddenly without drugs in a category all but guaranteed as a blockbuster.

"This will significantly affect the perception of their (future) revenues," but the companies could overcome that with replacement drugs down the road, said analyst Steve Brozak of WBB Securities.

Just four years ago, scientists were touting Acomplia as a Holy Grail of medical research, saying it showed promise in helping people lose weight, control blood sugar and other aspects of diabetes, lower cholesterol, quit smoking and stop abusing alcohol, marijuana and cocaine.

Some researchers predicted that once Acomplia got approval for weight loss or smoking cessation, research would ramp up in those other areas. But that early promise didn't materialize, it didn't win approval for smoking cessation and problems began piling up as psychiatric side effects — now a huge red flag for regulators — emerged in various studies of Acomplia as a diet drug.

Sanofi-Aventis said in a brief statement it was stopping ongoing human testing of Acomplia, known chemically as rimonabant, for all uses, "in light of recent demands by certain national health authorities."

Check obesity rates in your stateTwo weeks ago, Sanofi-Aventis temporarily stopped sales in Europe, where the pill had been marketed in 18 European Union countries since 2006. That move came after the European Medicines Agency recommended the European Commission temporarily suspend sales of Acomplia, saying its risks — depression, anxiety and stress disorders — outweighed its benefits.

At the time, Sanofi-Aventis said it "remains committed to Acomplia to bring an important therapeutic approach to obese and overweight patients," about 700,000 of whom it said had used Acomplia and gained health benefits. The company said it planned to provide additional evidence for health officials to re-evaluate its risks and benefits in patients with diabetes and heart disease.

In the U.S., a Food and Drug Administration advisory panel unanimously rejected the drug on June 13, 2007, citing psychiatric problems including increased risk of suicidal thoughts. Two weeks later, Sanofi-Aventis withdrew its application for U.S. approval.

For the first nine months of this year, Accomplia had sales of only 81 euros, about $113 million, not even making the company's top 15 products.

On Wednesday, Pfizer said it ended final-stage human testing of a drug known only by the designation CP-945,598 — not explicitly for safety concerns but because of "changing regulatory perspectives on the risk/benefit profile of the CB1 class and likely new regulatory requirements for approval."

"While confident in the safety of the compound, we believe that this is the appropriate decision based on all available information regarding this class of agents, as well as recent discussions with regulatory authorities," Martin Mackay, president of Pfizer Global Research and Development, said in a statement.

The statement said the company believes the compound "has the potential to be a safe and effective treatment for weight management."

Brozak, the analyst, said that Pfizer is technically correct in stating that even if the drug is safe, it's not certain that it could make it onto the U.S. market because the FDA "has almost become paralyzed with caution in its approval process."

Sanofi-Aventis said its decision would not affect its profit forecast. The company would not say whether it has any plans to try to resume sales, which never approached the levels anticipated. Past statements from Sanofi-Aventis indicate the drug at one point was approved for sale in 37 countries, yet was marketed in only 18.

Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments