A phase III clinical trial of an investigational Alzheimer's disease drug dimebon failed to show encouraging results dooming its future according to its commercial sponsors.
Pfizer and Medivation, the companies co-developing the drug, announced Tuesday that they were stopping all development activities after the phase III CONCERT trial failed to demonstrate significant benefit in patients with mild to moderate Alzheimer's disease. Pfizer and Medivation said that full results from CONCERT would be submitted for presentation at a future scientific meeting.
The companies are also terminating an open-label extension study that followed the main trial, which had randomized 1,003 patients to receive dimebon or placebo in addition to Aricept for one year. A phase III trial called CONNECTION completed in 2010 had also failed to show a benefit for dimebon. The two negative trials offset favorable results seen in an earlier phase III trial reported in 2008.
Dimebon originated in Russia decades ago, where it was long sold as an antihistamine for nasal congestion, leading to observations of apparent benefit in Alzheimer's disease patients. The drug was never approved or sold in the U.S.
Drugmakers Pfizer Inc. and Medivation Inc. have ended their agreement to develop and market Dimebon. Had it worked, it would have been a bigger blockbuster than Pfizer's Aricept, which only treats symptoms and now has generic competition. Pfizer however still has an Alzheimer's compound, a biologic drug called bapineuzamab, in late-stage testing with partner Johnson & Johnson.