An Alzheimer’s disease treatment that was previously rejected after producing conflicting results in clinical trials has demonstrated new potential in mouse models.

Researchers in the 1990s suggested that latrepirdine, commercially known as Dimebon, appeared to be effective in treating Alzheimer’s disease in animals. Resulting phase one and two trials demonstrated significant and sustained improvement in cognitive behaviour.

Research into Dimebon, which was originally approved as an antihistamine in Russia, continued in the US where it was advanced into a phase three trial. However, the drug failed to demonstrate any improvement in Alzheimer’s patients, and sponsors halted further clinical studies as a result.

Dimebon’s failure in the US led to some researchers speculating that Russian patients who responded well to the drug may have had a different disease stage or subtype, explaining the conflicting results.

Mount Sinai Center for Cognitive Health director Dr. Sam Gandy examined the drug’s failure and responded by conducting research into mouse models, randomly administering latrepirdine or placebo to mice engineered to present early stage Alzheimer’s disease.

The drug was found to halt both behavioural decline and progression of neuropathology by enhancing autophagy, the process in which cells protect the brain from neurodegenration, giving hope that the drug could still be advanced into clinical trials to treat early-stage Alzheimer’s.

"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 optimised, it still has potential," said Gandy.

The findings of the study were published in Molecular Psychiatry on 31 July 2012.