Here is something frustrating about clinical trials of Alzheimer’s drugs: the FDA requires that such trials show an almost immediate improvement in memory tests of participants in order for the drug to get approval, disregarding improvement in other symptoms, and consequently derailing a possible cure for this dreaded disease.
Here is why I think there is an inherent problem with this guideline:
If you go the the Alzheimer’s Association website and take the interactive tour of a brain with Alzheimer’s (a fantastic tool!), you will notice that there is a general pattern to the progression of Alzheimer’s and its accompanying symptoms. Specifically, looking at slide 13 you will see that the first part of the brain to be affected by Alzheimer’s is the inner core where the hippocampus resides—that part of the brain responsible for short-term memory. From there, damage spreads outwards to the cortex of the various lobes. As the second image in slide 13 shows, the Frontal Cortex is affected in mid stages of Alzheimer’s. This area is responsible for attention, social skills and intelligence (or wit). It is associated with “personality.”
Now, if an effective drug for Alzheimer’s were to be developed, you would expect to see the least damaged areas respond first, followed by the most heavily damaged areas.
Such were the preliminary results of the clinical trial of Dimebon. In reading the various anecdotal accounts of the Dimebon trial (see Bob DeMarco’s piece on the Alzheimer’s Reading Room), the results seemed to show precisely this initial response: Alzheimer’s sufferers reported increased alertness, social skills, and wit. Here is a sample quote from the various testimonials:
The major drug companies are focusing on memory. Are they after the right target? I’ll tell you this, in weeks 6 through 18 in the Dimebon clinical trial my mother was more engaged with me, more aware of her surroundings, more interesting, and more like her “old” self then she had been in six years.
The least damaged areas of the brain were affected in the 12-week trial! Then the trial was stopped because the inner (most damaged) area of the brain showed no marked improvement.
Would it not make sense to glean from the trial that a logical reverse course of the disease was set in motion and to continue it to see if the pattern held?
Pfizer et al, could you give us another 12 weeks when studying Alzheimer’s please?!
[Note: this analysis is mine alone. It may not be true that the least affected areas would show improvement first]