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A puzzling finding for promising Alzheimer's drug

July 16, 2009 | 10:09 am

Alz Many researchers believe that one way to treat symptoms of Alzheimer's disease is with drugs that reduce a substance called beta amyloid. This is a protein that is the main constituent of plaques found in the brains of people with the disease.

But in a surprising finding presented Wednesday at the Alzheimer's Assn. 2009 International Conference in Vienna, researchers discovered that a promising medication in phase-3 testing in the United States, called dimebolin or Dimebon, actually increases beta amyloid in the brain in animal models.

"This result is highly unexpected in what may prove to be a clinically beneficial Alzheimer's drug," Dr. Samuel Gandy, the lead author of the study, said in a news release. "We need more research to further clarify how dimebolin affects beta amyloid levels in the brain."

Previous studies show that Dimebon, which was used for years in Russia as an antihistamine, appears to help people suffering from mild to moderate Alzheimer's disease symptoms. In June, enrollment was completed for a six-month pivotal trial of the medication. The manufacturer, Medivation Inc., has announced it hopes to file a new drug application for Dimebon in 2011.

Researchers can't explain why Dimebon appears to be helpful even though it increases beta amyloid. It could be the drug's beneficial powers have nothing to do with amyloid. This theory would point to a new avenue of drug targets for treating Alzheimer's disease.

In other news from the Alzheimer's meeting:

A large study of people with mild cognitive impairment showed that the combination of cognitive tests and brain scans can be used to predict the development of Alzheimer's disease.

Researchers at UC Berkeley studied 85 people with mild cognitive impairment. Those with low scores on a memory recall test and low glucose metabolism in a particular brain region (measured by PET scan) had a 15-times greater risk of developing Alzheimer's disease within two years of the study compared with the other participants.

"By the time a patient is diagnosed with Alzheimer's disease, there is usually little one can do to stop or reverse the decline," Dr. William Jagust, the principal investigator of the study, said in a news release. "Researchers are trying to determine whether treating patients before severe symptoms appear will be more effective, and that requires better diagnostic tools than what is currently available."

Several studies have found that middle-age people who have moderate alcohol intake, such as a glass of wine a day, receive some long-term protection against cognitive decline and dementia in old age. A new study, the largest and longest to examine regular alcohol intake on dementia in seniors, has found that this protection also applies in old age. But there is one important exception: People who already have mild cognitive impairment might fare worse if they drink alcohol.

The study examined 3,069 people ages 75 and older about their drinking habits. The participants were examined and interviewed every six months for six years. The study showed that in people with no cognitive impairment at the start of the study, drinking eight to 14 alcoholic beverages a week resulted in a 27% reduction in the risk of developing dementia compared with people who did not drink at all. But for older adults with mild cognitive impairment, any consumption of alcohol was linked to faster rates of cognitive decline. People with mild cognitive impairment who were heavy drinkers were almost twice as likely to develop dementia compared with non-drinkers with mild cognitive impairment.

"Our results suggest that older adults who are normal cognitively and drink moderately do not need to change their drinking behavior," the lead author of the study, Dr. Kaycee Sink, said in a news release. "If you have mild cognitive impairment, however, it might benefit you to restrict your drinking and certainly not exceed one drink a day for women and two drinks a day for men."

-- Shari Roan

Photo: Steve Osman / Los Angeles Times