Alzheimer's vaccine passes key test

The vaccine, called AN-1792, is expected to enter phase two clinical trials by the end of 2002

By Rhonda Rowland
CNN Medical Unit

SAN FRANCISCO (CNN) -- An experimental vaccine designed to fight Alzheimer's disease appears to be safe in humans and is showing an immune response, according to scientists with Elan Corporation.

The scientists report they have concluded the first phase of testing designed to assess safety, and will now take the vaccine into phase two clinical trials by the end of 2002.

Alzheimer's is a degenerative disease of the brain that inexorably attacks nerve cells, causing impairment and loss of memory and mental functions. Worldwide, 22 million people are expected to develop the disease by the year 2025.

VIDEO Experimental vaccine designed to fight Alzheimer's disease shows positive results in humans. CNN's Rhonda Rowland reports (July 23) Play video (QuickTime, Real or Windows Media)     MORE STORIES Dale Schenk: Alzheimer's researcher Volunteers sustain clinical trials     EXTRA INFORMATION Clinical Trial Process Future of Alzheimer's Research    ALZHEIMER'S DISEASE: description risk symptoms treatment prevention Choose a link above to learn more about Alzheimer's disease. Source: WebMD

"We're extremely excited -- we're on the frontier of a completely novel approach to Alzheimer's disease," Dr. Ivan Lieberburg, executive vice president and chief scientific and medical officer of the Elan Corporation, told CNN.

The vaccine, called AN-1792, was studied in 100 patients with mild to moderate Alzheimer's disease in the United States and the United Kingdom. The trials lasted more than a year.

"The product showed that is was safe for patients and we didn't see any significant problems with it other than sore arms at the injection site, which is what you would expect," Lieberburg said.

"More importantly, as well we saw that in a significant proportion of the patients they were able to demonstrate an immune response. Their antibody levels went up and that indicates that this was having an effect in these patients," he said.

The scientists did not indicate any cognitive or memory improvements in the patients but said they were reacting to the vaccine as mice did in previous experiments.

Remarkable results in mice

Elan is developing the vaccine with Wyeth-Ayerst Laboratories, the pharmaceutical division of American Home Products.

Two years ago, Elan researchers reported remarkable results of the vaccine in mice. Mice immunized at a young age were protected from Alzheimer's; in animals that already had the disease, the disease was halted and in some cases reversed.

"We're hoping that if we see anything like what we saw in our mice experiments in people in phase two clinical study, that this would be a truly remarkable result," Lieberburg said.

The vaccine is designed to attack and clear out the characteristic beta amyloid plaques, above, seen in the brains of Alzheimer's patients. Many researchers believe that the amyloid plaques are the cause of Alzheimer's dementia

The Alzheimer's Association said Elan's announcement is an exciting development but should not preclude other avenues of research to find a way of preventing or curing the devastating disease.

"I think it's very exciting to see this product moving forward because it is going to be a test of one of the fundamental theories of Alzheimer's disease," said Dr. William Thies, vice president of medical and scientific affairs at the Alzheimer's Association. "While we don't know whether the product is going to work, we're going to find out an awful lot of valuable information no matter what the outcome of the trial is."

Vaccine attacks plaques

The vaccine is designed to attack and clear out the characteristic beta amyloid plaques seen in the brains of Alzheimer's patients. There is still some debate over whether the amyloid plaques are the cause of Alzheimer's dementia.

"If it turns out that the vaccine clears the protein out and it still doesn't affect the disease, then that's a clear indication that amyloid is not the causative factor," said Thies.

If the vaccine does affect the disease process, it will not be able to cure the disease.

"For people who have well-established disease, the vaccine can do nothing to return dead brain cells and certainly can't return memories," said Thies, "although it could potentially arrest the disease in whatever stage the individual is in."

The next phase of testing will include 375 Alzheimer's patients at multiple centers in the United States and Europe. The trials are expected to last about two years.