Findings could help give those at risk of the incurable condition "more years of healthy life".
09:46, 21 Mar 2025
Conceptual image of clinical research to develop a possible cure for Alzheimer's and dementia
Dementia is a degenerative condition that impacts the brain.(Image: Getty Images/Science Photo Library RF)
An medication has been found to half the risk of Alzheimer's-related dementia in people "all but guaranteed" to develop the disease in their thirties, forties and fifties.
A new study, published this week (March 19) in The Lancet Neurology, showed that participants with medical predispositions for developing Alzheimer's had their risk halved after trialling an experimental drug named gantenerumab over an eight-year span.
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Findings suggest - for the first time ever in a clinical trial - that early treatment to remove amyloid plaques from the brain - misfolded proteins that form into clumps that disrupt cell function - years before symptoms arise can delay the onset of Alzheimer's.
Dementia is an umbrella term for a range of disorders that affect the brain and impair cognitive functions like judgement and memory over time and currently has no cure. Alzheimer's is its most common form, with an estimated 90,000 people in Scotland living with the condition, according to Alzheimer's Scotland.
The international study involved 73 people with rare, inherited genetic mutations that cause the overproduction of amyloid in the brain, all but guaranteeing that they will develop Alzheimer's disease in middle age.
For a subgroup of 22 participants who had no cognitive problems at the study's start and who received the drug the longest - an average of eight years - the treatment lowered the risk of developing symptoms from essentially 100 percent to about 50 percent, according to a primary analysis of the data.
Elderly man with Alzheimer's and depression, with his back turned, looking out the window. Concept of old age, disease, loneliness, forgetfulness and memory.
Dementia causes the brain's function to deteriorate and currently has no cure(Image: Getty Images)
"Everyone in this study was destined to develop Alzheimer's disease and some of them haven't yet," said senior author Randall J. Bateman, MD, the Charles F. and Joanne Knight Distinguished Professor of Neurology at WashU Medicine.
"We don't yet know how long they will remain symptom-free - maybe a few years or maybe decades. In order to give them the best opportunity to stay cognitively normal, we have continued treatment with another anti-amyloid antibody in hopes they will never develop symptoms at all.
"What we do know is that it's possible at least to delay the onset of the symptoms of Alzheimer's disease and give people more years of healthy life."
The findings provide new evidence to support the so-called amyloid hypothesis of Alzheimer's disease, which posits that the first step on the road to dementia is the build-up of amyloid plaques in the brain, and that removing such plaques or blocking their formation can stop symptoms from arising.
For this study, Bateman and colleagues evaluated the effects of an experimental anti-amyloid drug to see if the medication could prevent the development of dementia.
3d illustration of nerve cells. Affected Human nervous system, concept for Neurological Diseases, tumors and brain surgery.
The incurable disease affects the nervous system(Image: Getty Images/iStockphoto)
The study's participants consisted of people who had originally enrolled in the Knight Family DIAN-TU-001, the first Alzheimer's prevention trial in the world, and then continued into an extension of the trial in which they received an anti-amyloid drug.
All in the trial had no to very mild cognitive decline, and were within 15 years before to 10 years after their expected age of Alzheimer's onset, based on family history.
When the trial concluded in 2020, Bateman and colleagues reported that one of the drugs - gantenerumab - lowered amyloid levels in the brain and improved some measures of Alzheimer's proteins.
But researchers did not see evidence of cognitive benefit yet because the group without symptoms - regardless of whether they were on drug or placebo - hadn't declined.
These mixed results in the group without symptoms led the trial leaders to launch an open-label extension so the researchers could continue studying gantenerumab's effects and determine whether higher doses or longer treatment could prevent or delay cognitive decline.
All participants who carried a high-risk Alzheimer's genetic mutation were eligible to continue into the extension study, regardless of whether they had received gantenerumab, another drug or a placebo during the trial.
Because all participants in the extension received the experimental drug, there was no internal control group. Instead, researchers compared the extension participants to people in separate related studies who had either received no treatment or a placebo.
Data analysis showed that removal of brain amyloid plaques years before symptoms are expected to arise delayed symptom onset and dementia progression, although the results were only statistically significant for the subgroup of people who started with no symptoms and were treated the longest.
For the group of participants who received gantenerumab only during the extension for two to three years because they had received another drug or placebo during the original trial, there have been no observable effects on cognitive function yet.
The longest-treated group had received gantenerumab for eight years on average, suggesting that treatment years before onset may be necessary for prevention. Effects of gantenerumab were strongest in this longest treated group.
"If late-onset Alzheimer's prevention trials have similar results to the DIAN-TU trials, there soon could be Alzheimer's preventions available for the general population," Bateman said.
"I am highly optimistic now, as this could be the first clinical evidence of what will become preventions for people at risk for Alzheimer's disease. One day soon, we may be delaying the onset of Alzheimer's disease for millions."
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