Latrepirdine (Dimebon) was initially sold as an antihistamine in Russia, approved for use there in 1983. In the 1990s, researchers determined that the compound appeared effective in treating Alzheimer's disease in animals. They continued their research in humans and performed several studies, including Phase I and II trials, all of which showed significant and sustained improvement in cognitive behavior with minimal side effects. The Phase II trials, performed in Russia, were overseen by U.S. Alzheimer's researchers, including Mary Sano, PhD, Director of the Mount Sinai Alzheimer's Disease Research Center.

However, when research was continued in the United States in a Phase III trial, the drug did not demonstrate any improvement in people with the disease, causing the sponsors to halt further clinical study of the drug in Alzheimer's disease. Some researchers have speculated that the Russian patients might have had different disease stage or subtype of Alzheimer's, and therefore were more responsive to treatment than the patients in the Phase III trials in the United States.

"When we learned that latrepirdine failed in patients in the United States in 2010, scientists around the world were disappointed and perplexed," said Dr. Sam Gandy. "We wanted to find out why the drug did so well in Russia, but then showed no effect in the global studies. The findings from our animal model studies indicated that this drug should not be discarded, and that, if its mechanism of action can be optimized, it still has potential."

"While this is just the beginning, our research shows that this previously cast-off drug still has strong therapeutic promise," Dr. Gandy added.

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