Research on skin cancer drug shows possible benefit in Alzheimer’s

We’ve had some exciting news broke today about a new study that found an FDA-approved drug for a form of skin cancer might prove to be an effective treatment against Alzheimer’s disease. We’re a long way from knowing if it will actually work as an Alzheimer’s therapy, but this study is promising – so promising that the Alzheimer’s Association will be funding the next step in understanding the mechanisms behind the study.

First, some background…

Plaques are deposits of a protein fragment called beta-amyloid that build up in the spaces between nerve cells. Though most people develop some plaques as they age, those with Alzheimer’s tend to develop far more. It is strongly suspected that plaques somehow play a critical role in blocking communication among nerve cells and disrupting processes that cells need to survive.

Bexarotene is used to treat a form of skin cancer. Previous research showed that this drug stimulates expression of a protein called apoE, which helps with the degradation of beta amyloid.

The Claim

In this study, scientists conducted a trial in mouse models of Alzheimer’s disease of bexarotene, with the goal of enhancing clearance of beta amyloid from the brain by increasing levels of ApoE protein. The scientists found that the orally-administered drug rapidly lowered levels of soluble beta amyloid and amyloid plaques in both young and older test animals, and also improved some cognitive and behavioral deficits.

The methodology

Scientists orally administered the bexarotene to mouse models that had been bred with Alzheimer’s disease. They then observed changes in mouse behavior and the levels of beta amyloid in the brain after delivery of the drug.

Beyond the headline

This is very exciting stuff! Investigating an already FDA-reviewed and -approved therapy may mean that the drug development process takes a somewhat shorter time because the drug has already been tested in hundreds, perhaps thousands, of people. As a result, we already know a lot about the drug and its side effects, though, in this case, it is in cancer populations, not Alzheimer’s disease. So there is still a great deal to learn. For example, without trials in people with Alzheimer’s, we know nothing yet about dose levels or how this compound may interact with other Alzheimer’s drugs.

It’s also important to remember this study of bexarotene is in a mouse model of Alzheimer’s disease. Mouse models of Alzheimer’s are limited in how closely they represent human Alzheimer’s, and mice are not people; so, we are still far away from knowing if this has potential as a therapy for people with Alzheimer’s.

The bottom line

This study is very preliminary. People with Alzheimer’s and their caregivers should not ask their doctor for this drug to treat Alzheimer’s disease. The Alzheimer’s Association awarded the senior scientist on this article, Gary Landreth of Case Western Reserve University, Cleveland, its prestigious Zenith Award in 2011 for research that will follow on from this study to investigate the mechanism of action of this compound. The goal is to further illuminate how and why it works in the way described in the Science Express article, perhaps setting the stage for trials in people – so stay tuned for more on this!

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