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Report on Dimebon
Comments by Dr. Jack Diamond, Scientific Director, Alzheimer Society of Canada
A new report describes a promising improvement in thinking. memory and in a variety of behavioural functions in early to mid-stage Alzheimer patients after being treated for 12 months with a drug called Dimebon.
Although the report includes a number of clinicians in various centres in the US among its authors, the principal investigators are in Russia, where the entire study was carried out. When results such as these are being evaluated, any improvement over the treatment period is important, however slight; even if there were no change in the patients this could represent an advance, because in the absence of treatment an overall decline in their status would have been anticipated over one year. A drug that both halts such a decline and goes further, improving a patient's status, is one to take seriously.
However, are there any concerns here?
Well, as almost always, there are. Firstly, the clinical benefits of Dimebon, some mild, were observed in a wide variety of conditions; it's been tried as an antihistamine agent for allergies, for heart disorders, for infections and, of course, for Alzheimer's disease. While there's nothing wrong in principle in this, the implication is that either (i) the drug is "targeting" a biochemical process (possibly more than one) that is common to a wide variety of the body's organs and tissues, or (ii) the drug is targeting multiple, quite different, biochemical processes, some operating more in one tissue, others in other tissues.
In either event the conclusion is the same; the potential side effects of the drug could be numerous, perhaps serious. Second, the number of patients studied (a total of 183, some taking the drug, some taking an inactive placebo) is far too small to justify accepting the drug as a proven therapeutic agent. Third, a year might not be long enough for important deleterious side effects to become detectable. Moreover the patient population studied, all living in Russia, might not be readily duplicated in say North America. Thus a longer study is now required, with many more patients, and these should reside in a number of different countries including Canada and the USA.
Finally, there is not yet a solid basis for understanding how Dimebon acts at the biochemical or cellular level. This is an important deficiency. At present the drug is not available in Canada.
In the end, a drug supported by reputable clinicians to the extent that this one is deserves serious consideration and support for its now being subjected to international long-term multi-centred clinical trials. If this were to be done an important new therapy for Alzheimer's disease could become available within about 10 years.
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