Alzheimer's Drug Nothing to Sneeze At
Used for Decades as an Allergy Drug, Dimebon now Shows Promise in Treating Alzheimer's Patients
By
Salynn Boyles
WebMD Health News
Reviewed By
Louise Chang, MD
April 17, 2008 — A nearly forgotten allergy drug first used in Russia more
than two decades ago is showing promise for the treatment of Alzheimer's disease.
In a study of the antihistamine Dimebon, Alzheimer's patients with mild
to moderate disease continued to show improvements in memory, thinking, and
daily and overall functioning over six months of treatment.
Some patients showed improvements when treated for up to a year.
Results from the Russian study were presented this week at the 60th annual
meeting of the American Academy of Neurology (AAN) in Chicago. Study results
were also reported last summer at an international conference on Alzheimer's
disease.
Dimebon Alzheimer's Trial
Dimebon was approved as an antihistamine in Russia in the early 1980s.
It attracted attention as a potential Alzheimer's treatment following
positive animal studies in 2000.
The human trial conducted in Russia included 183 patients with
mild-to-moderate disease treated for six months with either Dimebon or placebo.
Some patients continued to take the antihistamine for as long as a year.
Researchers reported significant improvement in memory, thinking, and other
cognitive measures over placebo in as little as 12 weeks, and the differences
were maintained over six months to a year.
Tests to measure mental function and interviews with caregivers confirmed
improvements or disease stabilization in 81% of the Dimebon-treated patients
after six months.
In a presentation delivered Thursday at the AAN meeting, Steven H. Ferris,
PhD, reported that the drug's impact in Alzheimer's patients appears to be
broad, rather than selective.
Ferris directs the Alzheimer's Disease Center at NYU School of Medicine.
"Our sub-analysis of the trial results suggests a broad, general benefit
affecting language, memory, and other domains of cognition," Ferris tells
WebMD.
International Trial Planned
The biopharmaceutical company Medivation Inc., which hopes to market Dimebon
for the treatment of Alzheimer's in the U.S., is funding a second study of the
drug to be conducted in the U.S., Europe, and South America.
If the earlier findings are confirmed, Medivation Inc. CEO David Hung, MD,
tells WebMD that the company plans to petition the FDA for the drug's approval
as an Alzheimer's treatment in 2010.
Dimebon has not been compared to the currently approved Alzheimer's drugs, but Hung says there are
suggestions from the Russian study that it has a different mechanism of action
that is unrelated to its antihistamine properties.
Three of the drugs — Aricept, Razadyne, and Exelon — block the activity of
an enzyme in the brain called cholinesterase and are approved for the treatment
of mild to moderate disease.
"What happens in Alzheimer's disease is that the neurons in the area of
the brain that govern memory and thinking get sick and die," Hung says.
"The cholinesterase inhibitors can slow this down, but they don't keep the
cells from dying."
Early findings suggest that Dimebon may keep the neurons alive and even make
sick neurons healthy again, he says.
Because many patients in the Russian trial showed improvements in memory and
other aspects of mental functioning over time, there is some suggestion that
the drug could modify the course of Alzheimer's disease.
Longer, rigorously designed studies would be needed to prove this,
however.
Alzheimer's disease researcher Steven DeKosky, MD, who was not involved with
the Dimebon research, calls the findings from the Russian study very promising.
But he adds that the findings must be confirmed.
DeKosky directs the Alzheimer's Disease Research Center at the University of
Pittsburgh.
"If the Russian findings hold up, that would be a big deal," he
tells WebMD. "There isn't anything out there that works as well as this
drug appeared to in that study. But there are still a lot of unanswered
questions. We will know more when the phase III international trial is
completed."
SOURCES: American Academy of Neurology 60th Anniversary Annual Meeting, April 12-19,
2008. Steven Farris, PhD, professor of psychiatry; head of the Alzheimer's Disease
Center, New York University School of Medicine, New York, N.Y. David Hung, MD, president and CEO, Medivation Inc. Steven DeKosky, MD, professor and chairman, department of neurology; director, Alzheimer's Disease Research Center, University of Pittsburgh. Lermontova, Bulletin of Experimental Biology and Medicine, 2000.
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