Dimebon disappointment

Dimebon (latrepirdine) has received widespread publicity as a potential therapy for Alzheimer's disease following a very positive phase 2 study carried out in Russia and published in the Lancet in 2008. In this study there were improvements over 6 months in all endpoints (cognitive, global, daily function and behaviour), with continuing improvement at 12 months in cognition and daily function. A more recent multinational phase 3 study, however, showed no improvements whatsoever and no difference between the two drug-treated groups and the placebo group. Of note, there was little deterioration in any of the groups after 6 months in contrast to the placebo group in the phase 2 study. The potential reasons for these disappointing results are discussed, as well as the implication for dimebon and drug treatment in Alzheimer's disease.