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Alzheimer's vaccine study suspended

The Alzheimer's vaccine that worked well in mice has caused unforeseen complications in human trials.
The Alzheimer's vaccine that worked well in mice has caused unforeseen complications in human trials.  

By Rhonda Rowland
CNN Medical Unit

(CNN) -- A human study of the experimental Alzheimer's vaccine AN-1792, which showed great promise in mice, has hit a snag and is being temporarily halted.

Four patients in France with mild to moderate Alzheimer's disease developed inflammation in the central nervous system according to a statement by the vaccine's manufacturers, Elan Corporation and Wyeth-Ayerst Laboratories.

"Recognizing that in trials a No. 1 concern is for patient safety, halting the dosing is a responsible move," Dr. Jenny Ward Robinson, medical and scientific director of the Alzheimer's Association, told CNN. "The origin of the problem is still unknown. We are not sure if the problem is due to the vaccine or another yet to be determined source."

What's the future of Alzheimer's research? 

While the companies try to pinpoint the cause of this complication, an independent monitoring group will determine if the study should move forward. It's not known how long the process will take.

"This sort of occurrence is not uncommon in the process of testing new medications," said Ward Robinson. "The nature of science is to move through this process towards discovery of what works, how it works and under which conditions successful outcomes are attainable."

So far, approximately 360 patients in Europe and the United States have received multiple doses of the Alzheimer's vaccine.

According to spokespeople at two of the 20 U.S. study sites, the University of California at San Diego and Baylor College of Medicine, dosing has been suspended and no unusual side effects have been seen in any patients. A previous study of AN-1792 in a smaller group of patients deemed the vaccine safe and showed it even produced an immune response.

The vaccine appears to work by interfering with the build-up of amyloid plaque in the brain, which is believed to be one of the hallmarks of Alzheimer's. Studies of AN-1792 in rats showed very promising results. The vaccine halted -- and in some cases reversed -- the disease, and even prevented the development of Alzheimer's in healthy mice.

Several other pharmaceutical companies are testing drugs that may work in a similar way. Besides treating the mind-robbing disease, the vaccine and drugs could help scientists determine the actual cause of Alzheimer's.

"It'll give us important information but I think there will be a great sense of disappointment if these drugs don't work," said Dr. Leon Thal, chairman of the Department of Neurosciences at the University of California, San Diego.


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