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Home : Life Style : Health : Dementia, Study Shows Plaque Vaccine Doesn't Slow the Progression

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Dementia, Study Shows Plaque Vaccine Doesn't Slow the Progression

Clara NewsDiscover.com on 28 July, 2008 13:31:20 | 54 times read

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A vaccine aimed at reducing brain plaques didn't stave off Alzheimer's disease, undercutting the theory that sticky wads of protein accumulating in the brain are the driving force of the debilitating disease. The patients were part of a study of AN-1792, a vaccine that Elan Corp. and Wyeth stopped work on in 2002 because of side effects. Researchers led by Clive Holmes of Moorgreen Hospital in Southampton, England wanted to see if the medicine cut the plaque levels, and if a reduction helped decrease symptoms.

While immunization with amyloid-beta peptide cleared the plaques, it didn't h -

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elp patients live longer or slow the disease's progression, according to a study in The Lancet. AN- 1792 was one of the first in a wave of experimental products against the clumps of protein that that build in the brains of patients with Alzheimer's. The disease affects 18 million people around the world, making it the most common form of dementia. Current drugs temporarily ease symptoms of the mind-robbing disease, without slowing it.

``This study will undoubtedly evoke concern that antiamyloid therapies will be ineffectual, and that two decades of experimental work supporting their development were spent barking up the wrong tree,'' Peter St George-Hyslop from the University of Cambridge and John Morris from the University of Toronto said in a comment accompanying the study.

Last June, Salt Lake City-based Myriad Genetics Inc. and Copenhagen-based H. Lundbeck A/S said their experimental Flurizan failed to improve memory or function in a key study of patients with Alzheimer's disease, the latest setback in efforts to slow or stop one of the most debilitating ailments in the elderly. Flurizan didn't improve cognition or the ability of patients to carry out daily activities in the study, which was in the final stage of testing.

A major part of Alzheimer's is accumulation of amyloid-beta molecules in the brain, which leads to the formation of plaques and is thought to contribute to dementia. The results may prompt some ``intriguing challenges'& - #39; to the amyloid hypothesis, Holmes wrote. Holmes followed 80 Alzheimer's patients from a study of the vaccine to determine the long-term effects on their brain function. The vaccine from Dublin-based Elan had reduced plaque and improved brain function in mice.

In eight patients who had given permission for their brains to be examined after death, the researchers found a reduction of amyloid beta compared with controls. Seven of the eight immunized patients, including those with virtually complete plaque removal, had severe end-stage dementia before death. ``Plaque removal is not enough to halt progressive neurodegeneration in Alzheimer's disease,'' Holmes wrote in his study.

The reasons for the findings aren't clear. The presence of the plaque - s may be necessary to initiate, but not to maintain, degeneration and the removal of plaques after immunization may be a slow process, Holmes said. Aggregated amyloid beta in the form of plaques may also be harmless, or even protective, so that removing it may be counterproductive, Holmes said.

Clara Luciana, Yogyakarta - (3336 spacer.gif/wikan)