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June 18, 2003 -- All FDA approved drugs for Alzheimer's disease are used to treat memory loss and other symptoms of the condition. But a new study involving one of the drugs -- Exelon -- suggests for the first time that they may also slow disease progression.
Researchers found that Alzheimer's patients who dropped out of one of three 26-week trials evaluating Exelon had delayed deterioration in mental function, even though they only took the medication for a few months. Their disease progressed more slowly than patients in the placebo arm of the study who never took Exelon, lead researcher Martin Farlow, MD, of the Indiana University School of Medicine, tells WebMD.
Farlow says the findings suggest a possible effect in delaying the biological progression of Alzheimer's disease. The study appears in the June issue of the journal Archives of Neurology.
"This study clearly shows that even exposure for a short time -- two, three, or four months -- can have an impact on disease progression," he says.
More than 4 million Americans have Alzheimer's disease, and that number could increase to more than 14 million over the next few decades, according to the Alzheimer's Association.
Although the trial only involved the Novartis Pharmaceutical's drug Exelon, other FDA-approved drugs for Alzheimer's -- Pfizer's Aricept, Warner Lambert's Cognex, and Janssen Pharmaceutica's Reminyl -- have similar mechanisms of action. All of these drugs boost levels of the neurotransmitter acetylcholine, which is instrumental in brain function, and all are approved for people with mild-to-moderate disease.
"It makes scientific sense that these drugs which impact acetylcholine levels would delay disease progression, but we haven't had the clinical data to tell us for sure if this is the case," Alzheimer's Association Vice President for Medical and Scientific Affairs Bill Thies, PhD, tells WebMD.
"This research is an interesting way to look at the question, but I don't think that it settles the matter at all. It certainly doesn't change the fact that none of these medications stop the progression of Alzheimer's disease."
Other Drugs in the Pipeline
But research is looking at other drugs for battling Alzheimer's disease. The FDA is considering approval of one of the first in a different class of Alzheimer's drugs. If approved, the drug memantine would be the first treatment available for patients who are in the later stages of Alzheimer's disease. Already approved in Europe, memantine targets a chemical in the brain known as glutamate.
Farlow and colleagues reported the results of a study combining memantine and Aricept three months ago at the annual meeting of the American Academy of Neurology in Hawaii. They found that patients on the combination treatment fared better over the six-month trial period than patients treated with Aricept alone, and they also tolerated the therapy better.
Thies says the combination approach is likely to be the first-line treatment for Alzheimer's disease as soon as memantine wins government approval.
"Because these drugs have different mechanisms of action, my guess is that they will be used together very quickly," he says. "One reason for this is that memantine seems to ease the gastrointestinal distress that is a common side effect of the other drugs. It may be a matter of patient preference as much as anything else."
SOURCES: Archives of Neurology, June 2003. Martin Farlow, MD, professor of neurology; associate director of the Alzheimer's Disease Center, Indiana University School of Medicine. Bill Thies, PhD, vice president of medical and scientific affairs, Alzheimer's Association, Chicago.