Scientists have hailed a "historic moment" in Alzheimer’s research after a trial identified the first ever drug to reduce memory decline and destroy key proteins associated with the disease.
The landmark study of 1,800 people showed that twice-weekly injections of lecanemab can reduce progress of the disease by 27 per cent, compared with a placebo.
The drug is the first ever disease-modifying treatment to both slow cognitive decline and reduce the plaques associated with the disease.
Changes were evident as early as six months after participants started taking the drug, lecanemab, researchers said. The drug was found to slow decline in participants’ memory and functional thinking.
Manufacturers Eisai, a Tokyo-based pharmaceutical company which has partnered with US biotech firm Biogen to develop the drug, is expected to file for approval in the US this year, before applying for a licence in Europe early next year.
Experts stressed that the drug has not been shown to cure Alzheimer’s disease. But researchers are now recruiting those at high risk of the condition to see if the drug could work even before any symptoms have developed.
Lecanemab is designed to target and clear amyloid, one of the proteins that builds up in the brains of people with Alzheimer’s at an early stage of the disease.
Eisai examined the drug – an “anti-amyloid beta protofibril antibody” – for the treatment of mild cognitive impairment for patients with amyloid in the brain.
The study, called CLARITY-AD, was the largest to date to test a long-debated theory that clearing toxic brain plaques, called amyloid, might slow the progress of Alzheimer’s disease.
The pharmaceutical company said the results were “highly statistically significant” results.
It compared results of people taking the drug and those taking a placebo – or dummy drug.
Scientists found that after 18 months the drug slowed the disease progression by 27 per cent compared with those taking the placebo.
At the same time, the trials showed differences in the build-up of amyloid in the brain in scans of participants, with those taking the drug having lower levels compared to those taking the placebo.
'Historic moment for dementia research'
Dr Susan Kohlhaas, director of research at Alzheimer’s Research UK, said: "This is a historic moment for dementia research, as this is the first phase three trial of an Alzheimer’s drug in a generation to successfully slow cognitive decline.
"This is the first drug that’s been shown to not only remove the build-up of a protein called amyloid in the brain, but to have a small but statistically significant impact on cognitive decline in people with early-stage disease."
Dr Kohlhaas said that "substantial side effects" will need to be considered, and that regulators across the world will need to assess the full data to determine whether the drug is safe and effective enough to be used in people with the disease.
She added that the drug "won't be a silver bullet for all causes of dementia", but said she hoped the results will "spark renewed investment in dementia research across the globe".
Of the people who experienced side effects, the most common were headaches and swelling in the brain, known as "amyloid-related imaging abnormalities".
'Time will tell if effect increases over time'
Dr Catherine Mummery, consultant neurologist at the National Hospital for Neurology and Neurosurgery, said the results are "exciting".
"If borne out by the full details of the study, as they are the clearest indicator so far that by lowering amyloid levels in the brain, cognitive decline can be slowed," she said.
"However, the size of the effect, while significant, is small – the disease is slowed by 27 per cent over 18 months. What we cannot know yet is whether that effect increases over time in an individual; that would be predicted but is untested – time will tell."
Rob Howard, professor of old age psychiatry, University College London, said: "This is an unambiguously statistically positive result and represents something of an historic moment when we see the first convincing modification of Alzheimer’s disease... God knows, we’ve waited long enough for this."
'Very likely more people will see their doctor now'
Meanwhile, Dr Liz Coulthard, an associate professor in dementia neurology at the University of Bristol, said: "Up to now, many people have not come forward when they first worry about their memory as there were no treatments for dementia.
"It is very likely more people will come to see their doctor now – and we, as doctors, need to be ready. Most people with mild memory symptoms will not have Alzheimer’s disease. We need to develop an effective and quick triage system so we can reassure people without Alzheimer’s and offer treatment to those with Alzheimer’s."
The trial evaluated the drug's ability to reduce cognitive and functional decline based on the Clinical Dementia Rating-Sum of Boxes (CDR-SB), a numerical scale used to quantify the severity of dementia in patients in areas such as memory, orientation, judgment and problem solving and personal care.