Pfizer

(PFE) - Get Report

is buying exclusive worldwide rights to an experimental class of

Bayer

(BAY)

obesity drugs.

According to the licensing agreement, Bayer will receive an upfront fee, milestone payments and royalties on sales of the drugs. The companies did not disclose specific financial terms of the deal, which is subject to antitrust approval but expected to close in the second half of the year.

"Obesity and diabetes are expanding hand-in-hand at near epidemic levels throughout the world. The need for new treatment options for patients has never been greater," said Dr. Martin Mackay, head of Pfizer's worldwide research and technology group. "We are excited about the potential of the DGAT-1 inhibitors in the areas of obesity and type 2 diabetes which complement Pfizer's ongoing metabolic disease research programs," Mackay said.

Pfizer's shares lifted 4 cents Wednesday, to $23.08.

The drugs, called DGAT-1 inhibitors, could potentially treat obesity, type 2 diabetes and related disorders by modifying fat metabolism. The lead drug in that class, BAY 74-4113, is currently in phase I trials, the earliest stage of human testing, which involve studying a drug's safety and looking for an indication of efficacy in patients.

Through the agreement, Pfizer is joining a number of drug developers that recognize that the obesity market is ripe for a new treatment since concerns have surfaced regarding the side effects and limited efficacy of

Roche's

Xenical and

Abbott's

(ABT) - Get Report

Meridia.

However, New York-based Pfizer's could be pitting itself against

Sanofi-Aventis'

(SNY) - Get Report

obesity drug Acomplia, whose approval is anticipated later this year. But the FDA

previously refused to approve the drug, saying the company needed to provide additional data before it could be approved. Accomplia is also being considered as a smoking-cessation treatment.

Arena Pharmaceuticals

(ARNA) - Get Report

, is developing a drug called

Lorcaserin, which supposedly works without the need for diet modification or exercise and avoids the cardiovascular side effects of

Wyeth's

(WYE)

notorious diet drug fen-phen, which was pulled from the market in 1997 because of safety concerns.

Nastech Pharmaceutical

(NSTK)

is also developing a treatment for obesity which would be administered as a nasal spray, but concerns that the drug was ineffective caused Nastech's Big Pharma partner

Merck

(MRK) - Get Report

to

pull out of the deal earlier this year. Nastech intends to keep working on the drug.

With a number of fad diets, nutritional supplements and pharmaceutical drugs failing, obesity rates are continuing to expand, and Americans are still looking for another quick fix for the growing problem of their bulging bellies.

Surgical procedures, such as gastric bypass and gastric banding, have also grown more popular, though they're most often used after various other weight-loss methods have failed. The development of a more effective drug, of course, would reduce the need for these potentially dangerous procedures. The mortality rate for patients undergoing gastric bypass procedures is about 2%.