An Alzheimer’s drug could prevent dementia before symptoms show, with research suggesting it could clear toxic brain plaques in just three months.

Trontinemab, a medicine given as a monthly infusion, will be offered to about 1,600 people with no memory problems who are at high risk of the disease to see whether it can stave off symptoms.

Scientists said the landmark trial could be a “game changer”, raising the prospect of “statins for the brain” being routinely offered to people in mid-life.

The phase III trial – the final pre-approval testing stage for a new treatment – will use blood tests to identify those most likely to benefit from taking part.

People aged 55 and over who are “cognitively unimpaired” but have biomarkers linked to the development of Alzheimer’s will be invited to take part.

Trontinemab, manufactured by Swiss pharmaceutical firm Roche, works by removing sticky amyloid plaques that aggregate in the brain and cause the degenerative disease.

Treatment ‘could stop people from ever showing signs of dementia’

Research presented at the Alzheimer’s Association International Conference in London found that blood tests could identify healthy older adults at the greatest risk of the disease.

Dr Maria Carrillo, chief science officer at the Alzheimer’s Association, said: “This is the future of Alzheimer’s care, targeting the earliest stages of the disease, including in its silent stage before memory issues arise.

“This is when treatments may have the greatest benefit – perhaps even keeping people from ever experiencing dementia symptoms.”

People who receive a positive test have an almost eight in 10 chance of developing cognitive impairment within a decade, data show.

Trontinemab is a next-generation version of lecanemab and donanemab, the first Alzheimer’s drugs shown to slow disease progression.

The previous drugs are licensed for use in the UK but are not approved on the NHS because they are not considered good value for money.

Trontinemab has been designed to reach the brain more efficiently than its predecessors and appears to have fewer side effects, so could require less monitoring, bringing down costs.

The new research suggests trontinemab can remove amyloid plaques much more quickly than existing treatments.

Hilary Evans-Newton, the chief executive of Alzheimer’s Research UK, said: “The science is advancing rapidly, and every new discovery brings us closer to a future where diseases can be identified and treated much earlier.

“Over the next five to 10 years, we will see a transformation in what’s possible, including the prospect of treatments that help protect brain health before symptoms progress – the concept of a ‘statin for the brain’.”

Scientists used data from 178 patients given the treatment and 477 brain scans to model how the drug would perform in a larger trial.

Trontinemab is administered through a drip in a hospital and analysis suggests brains of patients receiving the highest dose would be free of dementia-causing amyloid after three monthly infusions.

Top-up doses every three months are enough to keep plaque levels low for 18 months, data show.

It has yet to be seen whether the drug’s ability to remove plaque also prevents cognitive decline in the way shown with the previous Alzheimer’s drugs.

Lecanemab and donanemab were found to slow cognitive decline in symptomatic patients by 27 per cent and 35 per cent, respectively.

Highly accurate blood test

The prevention study for trontinemab, known as PrevenTRON, will recruit cognitively healthy volunteers in countries across the world, including the UK, aged between 55 and 80.

Volunteers will have tested positive for elevated levels of the biomarker p-tau217, which is found in the blood and linked to Alzheimer’s disease.

Younger participants will need additional genetic or family risk factors to be considered.

Evidence presented at the conference showed that using blood tests for p-tau217 provides up to 95 per cent accuracy at predicting Alzheimer’s disease.

Dr Rachel Buckley, associate professor of neurology at Harvard Medical School, said the new generation of treatments being trialled was “wonderful”, adding that she hoped to see success in cognitively unimpaired individuals in the coming 12 to 24 months.

“If these trials are positive, the game changes,” she told an event organised by the Women’s Alzheimer’s Movement.

Close to one million people in the UK have dementia, a figure predicted to reach 1.4 million by 2040.

Both lecanemab and donanemab were rejected for routine NHS use after the National Institute for Health and Care Excellence concluded they did not represent good value for money.

The last-generation drugs also caused brain bleeds in as many as one in four patients, but early studies suggest trontinemab causes the complication less often because it enters the brain more efficiently, raising hopes it could require much less monitoring, pushing down costs.

More than 50 GP practices are to start offering blood tests for Alzheimer’s disease, as part of the UK’s largest study using the diagnostic tests at surgeries. Up to 500 patients with suspected Alzheimer’s in Scotland will be offered tests measuring p-tau proteins.

‘Clearest evidence yet’ for pinpointing disease early

Separate research, published in the Journal of the American Medical Association, analysed almost 2,700 cognitively healthy adults with an average age of 70. Those with the highest p-tau217 levels had an estimated 78 per cent chance of developing cognitive impairment within 10 years, compared with 45 per cent of those with moderately raised levels.

Dr Buckley, the lead author of the paper, said: “Our findings provide some of the clearest evidence yet that elevated p-tau217 levels may help detect dementia risk years earlier – even in adults with no noticeable memory or thinking problems.

“In the future, when treatments are approved for use early in the disease process, these tests could help guide monitoring, treatment decisions and counselling for patients and families.”

Dr Richard Oakley, associate director of research and innovation at the Alzheimer’s Society, said: “One in three people born today will develop dementia in their lifetime, making it vital that we find new ways to detect and diagnose the condition earlier. Blood tests are the most promising development in dementia diagnosis research and this study suggests they could also help identify people at increased risk of memory and thinking problems years before symptoms appear.”

Dr Jacqui Hanley, head of research funding at Alzheimer’s Research UK, said the latest findings were encouraging, and she called for larger trials to show whether the drugs made a “meaningful impact” to people’s lives.

She said: “PrevenTRON is part of an important shift in research, from focusing on people who already have symptoms towards finding those most at risk and seeing whether treatment can delay, or perhaps one day prevent symptoms developing. It raises the exciting possibility that Alzheimer’s could eventually be treated preventively, in a similar way to using medicines to reduce the risk of heart attacks and strokes.”

‘I feel like I’m taking back some control’

Carole Greig, 71, a retired bank worker from south-west London, was diagnosed with Alzheimer’s disease after her daughter Amanda noticed she was becoming increasingly anxious and getting lost.

After seeing her GP, Carole was referred for memory tests and later diagnosed with Alzheimer’s.

She said: “The diagnosis was a terrible shock and left me feeling helpless. Thanks to an early diagnosis, I was eligible to take part in the new trontinemab trial at King’s College London.”

She joined the study in February after undergoing PET scans and cognitive tests.

She said: “The whole experience has been very positive. I feel like I’m taking back some control after my diagnosis. I have monthly infusions and haven’t had any side effects.

“I’m closely monitored throughout the trial with regular MRI and PET scans, as well as cognitive tests every three months. It gives me enormous confidence that my health is being carefully monitored. Without the trial, there is no system for routinely tracking people after a dementia diagnosis.

“I’m very grateful to be taking part and hope one day everyone will have access to treatments. Research gives people the best chance of living well for longer.

“At the moment I don’t know whether I’m receiving the drug or a placebo, but after a year I’ll receive the treatment either way. That gives me great hope, not just for delaying my own symptoms and giving me more quality time with my family, but for future generations too.

“I would say to anyone with symptoms, don’t delay and get a diagnosis because you can then be proactive by giving yourself more choices and better chances for your future.”