While the negative result from the CONNECTION trail could simply mean that Dimebon does not work, says Lipton, it is also possible that the studies used the wrong doses of the drug or gave the doses too infrequently or at the wrong stage of the disease.
Dr. Samuel Gandy, professor of Alzheimer's disease research at Mount Sinai School of Medicine, adds that in light of other trials, such as one published recently in the Archives of Neurology, which find benefit for Huntington's with Dimebon, the negative results are "puzzling" but not necessarily condemning.
"A careful post mortem is in order before the coffin lid is closed," he says.
What's more, other Alzheimer's drugs currently on the market, like Namenda, also failed to show benefit in some of their clinical trials, says Murali Doraiswamy, Chief, Division of Biological Psychiatry at Duke University Medical Center. Doraiswamy is an investigator on another Medivation clincial trial of Dimebon called CONCERT.
He points out that as long as another trial of Dimebon proves positive, the FDA will most likely approve the drug.
Whether puzzling, unexpected, or disappointing, these negative results unfortunately mean that a promising treatment option may not pan out for patients, Lipton says, but as far as pharmaceutical development is concerned, it may be "the end of a chapter but the beginning of a new one."