What a quick turnaround: a drug used to treat cancer can reverse Alzheimer's disease in mice – and it takes just 72 hours to work its magic. It remains to be seen if the drug has the same effect in people with Alzheimer's, though.
Alzheimer's disease is associated with deposits of beta-amyloid peptides in the brain. The build-up is thought to underlie the abnormal brain activity that leads to memory problems, and also kick-starts a chemical cascade that ultimately leads to the death of neurons.
Paige Cramer at Case Western Reserve University School of Medicine in Cleveland, Ohio, reckoned it might be possible to prevent that build-up using bexarotene, an anti-cancer drug. She reasoned that a healthy brain can clear beta-amyloid deposits through a process facilitated by a substance called apolipoprotein E (ApoE). ApoE is activated in part by a receptor called RXR – and bexarotene enhances the action of RXR.
When mice with Alzheimer's-like brain damage were given bexarotene orally, they were able to clear more than half of the beta-amyloid peptides from the brain within 72 hours. They also showed a rapid reversal of cognitive and social deficits.
Cramer says she hopes to begin phase 1 clinical trials in the next few months. "We believe that because bexarotene is approved [for use in humans], we will be able to transition much more quickly from basic research to the clinic," she says.
Other researchers caution that the study, while encouraging, does not mean that the drug will work so well in people with Alzheimer's. Many drugs that have shown promising results in mice fail to have similar effects in humans.
"The drug development world is littered with drugs that seemed to work on transgenic mice, but didn't work on people," says Derek Hill at University College London. "A programme of clinical trials is needed to assess whether these potentially promising results translate into an effect on the human disease."
David Allsop, a neuroscientist at the University of Lancaster, UK, agrees. "It looks promising in the mouse model, but in recent years these types of experiments in mice have not translated well into humans, and so it is too early to get excited about the prospect of an effective therapy for Alzheimer's disease," he says
Journal reference: Science, DOI: 10.1126/science.1217697