Dimebon is an over-the-counter drug in Russia, where it
has been used for over 20 years as an antihistamine. Russian
scientists collaborating with researchers in San Francisco have
shown that Dimebon antagonizes -- in other words,
slows down -- cell receptor proteins that promote calcium
entry into cells (Grigorev et al. 2003). This may help
Huntington's people, because excess calcium has been shown to
damage brain cells in Huntington's.
In 2001, Russian investigators reported success in a Phase 1 trial of Dimebon in Alzheimer's patients (Bachurin et al. 2001). A small U.S. company, Medivation, bought rights to the drug and, in 2006, reported a successful Phase 2 trial in Alzheimer's patients in Russia (press release). In this Phase 2 trial of 183 patients, Dimebon out-performed the drugs commonly used for Alzheimer's in measures of cognitive and daily living functions. The drug also improved mood. There were no significant side effects reported. One very positive sign is that all participants wanted to continue the drug for 6 months beyond the originally planned end of the trial.
A clinical trial of Dimebon for Huntington's is starting in the U.S. under the auspices of the Huntington Study Group (HSG) with financial support from Medivation(press release). The trial is expected to enroll 111 participants with early to moderate symptoms and will compare a placebo group to groups that receive active drug at different doses over a 4 month time period.At present, the only recruitment center where people can sign up for the trial is at the University of Virginia (announcement). We hope that other recruitment sites will be announced soon, but we have no firm information as to which centers will be involved or when this will happen. The company says that information on participating centers will be posted at www.clinicaltrials.gov as soon as each site receives approval to start recruiting. HSG has published a toll free number 1-800-487-7671 for those interested in learning more about Dimebon trials.
If early trials are successful, Medivation can be expected to make a deal with a larger pharmaceutical company to support the cost of a much larger Phase 3 trial that will be necessary for FDA approval.
Grigorev VV, Dranyi OA, Bachurin SO. Comparative study of action
mechanisms of dimebon and memantine on AMPA- and NMDA-subtypes
glutamate receptors in rat cerebral neurons. Bull Exp Biol
Med. 2003 Nov;136(5):474-7. PubMed abstract
Bachurin S, Bukatina E, Lermontova N, Tkachenko S, Afanasiev A, Grigoriev V, Grigorieva I, Ivanov Y, Sablin S, Zefirov N. Antihistamine agent Dimebon as a novel neuroprotector and a cognition enhancer. Ann N Y Acad Sci. 2001 Jun;939:425-35. PubMed abstract