Test of Alzheimer's vaccine in mice shows promise

July 7, 1999
Web posted at: 11:09 p.m. EDT (0309 GMT)

From staff and wire reports

(CNN) -- An experimental vaccine shows promise in reducing brain deposits linked to Alzheimer's disease in mice -- suggesting the substance might one day be used to treat humans suffering from the debilitating disorder.

Scientists at Elan Pharmaceuticals developed the vaccine, called AN-1792. It is designed to attack the characteristic plaques found in the brains of Alzheimer's sufferers, which are caused by a sticky protein called amyloid.

"We view the plaque, if you will, as an invader in the brain, and we were curious to know if we would treat this as though it was any other type of invader, such as a bacteria, and thus use a vaccination approach," said Dr. Ivan Lieberburg of Elan Pharmaceuticals.

Elan's findings were reported in Thursday's edition of the journal Nature. The company hopes to begin testing the vaccine in humans next year

In one experiment, young mice genetically engineered to develop Alzheimer's disease were immunized with AN-1792 before they developed the brain plaques. Thirteen months later, the immunized mice showed no signs of disease.

In a second experiment, mature mice showing signs of Alzheimer's brain damage were treated with AN-1792 for seven months. Researchers found that during that time, plaque formation was not only halted but reduced.

"If we see anything resembling like what we saw in our animals in patients treated with this vaccine, this should revolutionize Alzheimer's therapy," Lieberburg said.

While the findings are promising, researchers caution that Alzheimer's disease in mice only partially mimics the disease in humans. Also, the amyloid plaques may be a symptom of Alzheimer's disease, rather than its cause.

Still, according to the Alzheimer's Association, the research could yield other important information.

"We may be able to block the amyloid deposits and do nothing for the disease. If that happens, we can then move on to looking at other causes that we already know are potential causes of Alzheimer's disease," said Bill Thies of the Alzheimer's Association.

If the vaccine does work, scientists will face another challenge -- determining who needs it. While detectable genetic flaws are linked to some Alzheimer's cases, most patients have no such telltale markers.

"If we are going to have the maximal effect of this, we need to find out who has the disease -- who is at risk -- much earlier," said Dr. Zaven Khachaturian, senior medical adviser to the Alzheimer's Association.

There is no known cure for Alzheimer's, which is believed to affect some 18 million people worldwide. Patients, most older than 60, progress from forgetfulness to dementia and usually die five to 10 years after diagnosis.

Medical Correspondent Rhonda Rowland and The Associated Press contributed to this report.