Chicago ? However far off a cure may be for Alzheimer’s disease, Baxter International Inc.’s announcement Tuesday that a small-scale study showed progress in improving memory function in elderly patients is the latest indication that drug companies and the government are pushing hard to find treatments for an insidious and costly disease.

Just as momentum built in the 1990s in the fight against AIDS, researchers have identified several potential avenues to follow in the search to slow the progression of Alzheimer’s, with the National Institutes of Health putting money toward several projects, including Baxter’s.

There is neither a cure nor is there an approved treatment that will change the course of the disease as there is for AIDS today; there are only some pills that slow the worsening of symptoms for about half the individuals who take them, experts say.

It is hoped that the use of Deerfield, Ill.-based Baxter’s drug Gammagard, currently used as an intravenous immune system treatment, and other drugs that work similarly to bolster immune systems, would actually slow or even stop the progression of Alzheimer’s disease.

The 24-patient study represents a preliminary step forward, and a small one since hundreds of patients can be needed for some drugs to win approval.

But researchers believe Baxter’s drug has one advantage in that it already is established as safe, since the product has been used for years to treat patients with immune system disorders.

“This is really the beginning of a new era,” said Dr. David Bennett, professor of neurological sciences and director of the Rush Alzheimer’s Diseases Center at Rush University Medical Center in Chicago.

“We are moving away from … old drugs that are designed to improve symptoms without affecting the underlying progression of biology,” Bennett added.

“There a lot of things going on right now that are targeting changing the biological processes and slowing the biological progression and possibly reversing the course of the disease.”

The idea behind the Baxter drug is that the body’s own immune system can potentially clear the brain of a protein fragment known as beta-amyloid that builds up and is deemed a key player in the development and progression of Alzheimer’s disease.

Other companies, too, are studying antibody therapies, including a joint venture between New Jersey drug giant Wyeth and Ireland-based Elan Corp. It is pursuing a new drug that analysts consider further along in the research process. It is on track for a possible submission next year to the Food and Drug Administration for approval.

In addition, companies ranging from pharmaceutical giants to small biotech companies are looking at older classes of anti-inflammatories and cholesterol-lowering statins to boost the immune response against the disease.

Alzheimer’s disease affects nearly 5 million Americans and the number is rapidly rising. The disease’s reach increases with age, affecting almost half of people age 85 and older.

The national direct and indirect costs to care for people with Alzheimer’s is estimated at more than $100 billion a year, according to the NIH’s National Institute on Aging.

Baxter’s trial of 24 patients shows that 16 patients on Baxter’s Gammagard had a better cognitive response than 8 patients on a placebo. Neither Baxter nor researchers at Weill Cornell Medical College in New York, which is leading the Gammagard trial, would release specific results of the Phase II trial. They are expected to be published in medical journals, perhaps by the end of this year.

In a statement, Baxter said that “although these results are promising,” they need to be confirmed with larger trials.

Baxter was careful not to hype the study; it did not provide executives for interviews or include quotes from company officials in a news release.

Baxter’s stock, which opened up slightly in trading on the New York Stock Exchange, ended Tuesday’s day of trading down almost 2 percent, or 98 cents a share, to $51.67 as U.S. stocks dropped the most in three weeks as part of a broader market decline.