A common cancer drug may prevent the onset of Alzheimer's disease and could be given to people in their 30s to stop dementia ever developing, scientists believe. Researchers at the University of Cambridge say Bexarotene could be the first "neurostatin" - a drug that works like a statin, but for the brain rather than the heart.
The drug has already been tested on Alzheimer's patients, and did not reverse the condition, but scientists now think that was because it was given too late to be effective.
"You wouldn't give statins to someone who had just had a heart attack, and we doubt that giving a neurostatin to an Alzheimer's patient who could no longer recognise a family member would be very helpful," said Prof Chris Dobson, Master of St John's College, University of Cambridge.
"But if it reduces the risk of the initial step in the process, then it has a serious prospect of being an effective preventive treatment."
The drug targets the first step in the toxic chain reaction that leads to the death of brain cells and the onset of Alzheimer's disease.
Tests showed it delayed the onset of Alzheimer's disease, both in a test tube and in nematode worms. When the drug was given to worms genetically programmed to develop Alzheimer's disease, it had no effect once symptoms had already appeared.
But when the drug was given before any symptoms became apparent, no evidence of the condition appeared.
The drug works by preventing a process called "primary nucleation" which occurs when proteins in the body misfold and begin to clump together, eventually forming the sticky plaques that cause dementia. "The body has a variety of natural defences to protect itself against neurodegeneration, but as we age, these defences
become progressively impaired and can get overwhelmed," said Prof Michele Vendruscolo of Cambridge's Department of Chemistry, the paper's senior author.
"By understanding how these natural defences work, we might be able to support them by designing drugs that behave in similar ways.
"This, in terms of an approach for Alzheimer's disease, would be the equivalent of what statins do for heart conditions. So you would take them well in advance of developing the condition to reduce your risk.
"I think the spirit should be similar to the way statins are used, so they are given to people that are more at risk of disease and given fairly early.
"There is some evidence that amyloid-beta aggregation takes place in middle age, so we may start in people in their 30s."
The research was published in Science.