PHILADELPHIA - It sounds too good to be true: A pill that helps you lose weight, quit smoking and reduce the cardiovascular risks for diabetes and heart disease.

Sanofi-Aventis SA’s new treatment, Acomplia, also known as rimonabant, has shown promise in a half-dozen clinical trials in curbing the cravings that make people hungry and reach for a cigarette.

The experimental drug, which works differently from other weight-loss medicines, could be approved by the Food and Drug Administration as soon as this month. And industry analysts predict it could become the world’s first blockbuster antiobesity treatment, with annual sales of 2 billion to 4 billion euros, or $2.4 billion to $4.8 billion.

In studies, a 20-milligram dose once a day helped patients lose 5 percent to 10 percent of their weight in a year, raise good HDL cholesterol, lower triglycerides and improve blood sugar and blood pressure.

"There is a lot of excitement about it," said Daniel Rader, cholesterol expert and director of Presbyterian Medical Center’s Lipid Referral Center at the University of Pennsylvania. "We haven’t had a new drug for obesity come out in quite a while, and the drugs we have aren’t the greatest."

Rader thinks Acomplia is "likely to be approved" and potentially could be "a very successful drug. There is such a tremendous desire and need for new approaches to help people lose weight, as well as for smoking cessation, and my understanding is the safety has been pretty good in the trials."

If Acomplia gets marketing approval from the FDA later this month, Paris-based Sanofi-Aventis has said it could begin selling the pill by June 30.

Rimonabant is the first in a new class of medicines that works in the body’s endocannabinoid system, which has a role in appetite. The drug works by blocking cannabinoid-1 receptors in the brain, deterring the munchies and cravings for nicotine. In the liver, it blocks the rate of fatty acid synthesis, which alters triglyceride and HDL cholesterol levels, and in fat cells it blocks hormones that increase insulin.

Acomplia’s most common side effects are nausea, dizziness and diarrhea. The drug also can affect mood. Depression and anxiety, while not common, did occur at higher rates than on a placebo.

Susan Yanovski of the National Institutes of Health said in a New England Journal of Medicine editorial in November that weight-loss medicines have a checkered history. Weight loss is rarely sustained after the drugs are stopped, she said. And there have been safety issues. The diet-drug combination known as "fen-phen" was withdrawn in 1997 after it was linked to heart-valve problems. Litigation costs and legal settlements caused Wyeth to set aside $21 billion in charges.

Yet pharmaceutical companies are still seeking a magic pill for obesity. Acomplia is a "source of great speculation for the financial community because of its novelty and unique clinical profile," Prudential Equity Group analyst Timothy Anderson said in a note.

The sales potential of Acomplia has prompted other companies, including Pfizer Inc. and Merck & Co. Inc., to pursue their own cannabinoid-receptor-blocking products. None is close to regulatory review.

The trade group Pharmaceutical Research & Manufacturers of America said there were now 21 new drugs in clinical trials for obesity.

With about 30 percent of U.S. adults obese - more than 60 million people - and 16 percent of children and teens overweight, according to the Centers for Disease Control and Prevention, the potential market is huge, analysts say.

Company executives are in final discussions with the FDA about possible approval of Acomplia, and they have been silent about the timing of a decision and about what medical indications for the drug’s label the FDA might approve.

"We’re down to the wire with the FDA," said Senior Vice President Porter McMillian Jr., head of U.S. operations.