An Alzheimer's disease breakthrough?

We all hope to get old one day.  But if we do, our chances of getting Alzheimer's disease increase dramatically as we move into our 80s.  As many as 50% of people over age 85 may be affected.  Much progress has been made in understanding the disease, which appears to be caused by "plaques" forming in the brain, but we have no treatment and no cure.

But maybe - just possibly - a dramatic new study offers the first real hope for a treatment.  In a paper published today in the journal Science, a team of researchers led by Gary Landreth at Case Western University and his graduate student Paige Cramer found that an orphan drug called bexarotene has a remarkable affect on mice afflicted with a condition similar to Alzheimer's in humans.  These mice have similar plaques in their brains, compose of beta-amyloid proteins, and they show behavioral and cognitive impairment similar to some of the problems experienced by Alzheimer's patients.

Within just hours of administering bexarotene to these mice, the plaques started to clear.  If that weren't amazing enough, within a few days the mice also recovered cognitive abilities that they had lost.  In particular, they regained the ability to make nests, a behavior that normal mice have and that the Alzheimer's mice had lost.  They also regained at least some of their sense of smell.

Bexarotene (Targretin^TM) is an orphan drug that is approved for use in humans to treat cutaneous T-cell lymphoma, a rare skin cancer.  It works by inhibiting a gene, RXR, that is involved in the production of beta-amyloid proteins.  Cramer, Landreth, and colleagues hypothesized that because bexarotene can cross the blood-brain barrier, it might just help to clear out the plaques associated with Alzheimer's.  It seems that they may be right.

A huge caveat here is that many promising drugs seem to work in mice but fail when used in humans.  This drug is different, at least in the sense that it is already approved for human use, but no one has tested it on Alzheimer's patients.  Studies are likely to begin very very soon, but it will take time - possibly years - before we know if it can slow the progress of Alzheimer's.  But for a disease that affects a huge percentage of the population, with no current treatment, this could be a huge breakthrough.