Dimebon Shines as Alzheimer's Therapy
Alzheimer's Stable With Dimebon; Alzheimer's Drug Rember Looks Good, Too
July 30, 2008 -- Dimebon, a 25-year-old Russian antihistamine, seems to stabilize Alzheimer's disease in an 18-month study, surprising experts at this week's International Conference on Alzheimer's disease.
It's not the only experimental Alzheimer's treatment to show promise. That's especially good news, coming on the heels of a conference report that drove the last nail into the coffin of Flurizan, a once-promising Alzheimer's treatment.
Dimebon is now only one clinical trial away from approval. That trial is now recruiting patients. Success -- not guaranteed, as the Flurizan flop shows -- means Dimebon could be in pharmacies in two or three years.
In Russia, where the drug was tested against a placebo in 183 patients with mild or moderate Alzheimer's disease, Dimebon stabilized disease for at least 18 months. Overall, patients treated with Dimebon tended to have better or not-much-worse mental function, while those given placebo pills got significantly worse.
That difference is the biggest ever seen in Alzheimer's studies, says David T. Hung, MD, president and CEO of Medivation, the U.S. firm developing Dimebon.
"The effect size for Dimebon is the largest ever seen over placebo in a trial of an Alzheimer's treatment," Hung tells WebMD. "And over one year, when placebo patients had declined, our patients were kept at or even above baseline on every parameter tested, including memory, cognitive function, and behavior."
Less impressed with the findings is Gary J. Kennedy, MD, director of geriatric psychiatry at New York's Montefiore Medical Center. Kennedy warns that placebo-treated Alzheimer's patients in Russia get far different care than U.S. patients, who must be allowed access to existing treatments.
That would make any effect of Dimebon seem greater compared with placebo. And Kennedy says that patients' actual improvement on Dimebon is not very different from improvement seen with the existing Alzheimer's drugs Aricept, Razadyne, and Exelon.
"They say people improve over time on Dimebon, and that it has a bigger impact on Alzheimer's disease than we've seen before -- but the data don't bear out much enthusiasm for that," Kennedy tells WebMD. "However, what is exciting is that this drug has a different mechanism of action than other dementia drugs. So this is a medication that could be combined with existing drugs to possibly slow down the course of the disease."
Samuel Gandy, MD, PhD, chairman of the Alzheimer's Association's Medical and Scientific Advisory Council, found the Dimebon data "very encouraging," but warns patients not to get their hopes up too high -- yet.
Although the Russian study included well-respected Alzheimer's researchers from the U.S., the study must be replicated by independent investigators in American and Western European settings. And it's not at all clear whether Dimebon alters the course of Alzheimer's disease or just makes symptoms better for a while.