About five million people in the United States are living with Alzheimer’s, according to the Alzheimer’s Association, an advocacy group funded by individual donors as well as foundations and major corporations, including drug makers. Without a cure or new treatments, the number of those with the disease could grow to 13.2 million by 2050, the National Institute on Aging estimates.

“I think this is going to be the disease, and maybe one of the biggest health care political issues of my generation,” says Robert Essner, 59, Wyeth’s professorial chief executive. “It’s hard for anyone to envision how to provide health care in the United States if you’re going to have to deal with the burden. You just start to add up the cost, 20 years from now as my generation gets old — it’s phenomenal.”

Mr. Essner will have more than a host of grateful baby boomers awaiting him if Wyeth’s crusade is successful. The company could snare a big financial payoff from what still amounts to a risky bet, one that has already cost Wyeth about $450 million in research funds. But with a treatment that slows progress of the disease possibly selling at more than $20,000 a year, the company’s Alzheimer’s program is one reason that some analysts are voicing renewed enthusiasm about Wyeth’s stock, which had been weighed down for years by costly fen-phen diet drug litigation.

Wyeth is hardly the only company looking for Alzheimer’s treatments. Virtually every large drug maker and a number of smaller biotechnology companies are working to develop Alzheimer’s drugs, with several hundred ideas under study. Several companies are expected to announce results of clinical studies during an international Alzheimer’s meeting that is under way in Washington. “There seems to be a current of excitement,” said Peter Davies, a biochemist at the Albert Einstein College of Medicine in the Bronx, who has studied Alzheimer’s for 30 years. Dr. Davies is working with Eli Lilly and Applied NeuroSolutions on a possible course of treatment that is such a secret that he will not say anything about it. “I wouldn’t say it’s a race,” Dr. Davies said, “but this is novel and we want to get a jump on therapeutics.”

The four Alzheimer’s treatments now on the market work by regulating the action of chemical neurotransmitters in the brain. The drugs — Aricept by Eisai and Pfizer, Exelon by Novartis, Razadyne by Johnson & Johnson and Namenda by Forest Laboratories — have shown mixed results treating Alzheimer’s symptoms and do nothing to stop the disease’s progress.