Preliminary data from a study of lecanemab, released in September, found it slowed cognitive decline by 27 percent over an 18-month period.
The full study data, published in the New England Journal of Medicine, substantiates these findings but also raises concerns about the occurrence of “side effects,” including cerebral hemorrhage and swelling.
The results showed that 17.3 percent of patients given the drug experienced cerebral hemorrhage, compared with nine percent of those given a placebo.
And 12.6 percent of those taking the drug experienced brain swelling, compared with just 1.7 percent of those in the placebo group.
Deaths were reported at about the same rate in both arms of the study with the drug, which was being developed by the companies Biogen and Eisai.
The findings have been widely welcomed by researchers and advocates for patients with the disease, including Bart De Strooper, director of the UK Dementia Research Institute.
“This is the first drug that offers people with Alzheimer’s a real treatment option,” he said.
“While the clinical benefit appears somewhat limited, it can be expected to become more evident as the drug is administered over a longer period of time.”
– Longer attempts required –
In Alzheimer’s disease, two key proteins, tau and amyloid-beta, build up into tangles and plaques, collectively known as aggregates, which cause brain cell death and brain shrinkage.
Lecanemab works by targeting amyloid, and De Strooper said the drug has proven effective at clearing it, but also has “beneficial effects on other hallmarks of Alzheimer’s, including tau.”
The phase 3 trial involved nearly 1,800 people divided between those receiving the drug and a placebo, and ran for 18 months.
They were assessed on a clinical scale for Alzheimer’s patients that measures cognition and function, as well as changes in amyloid levels and other indicators.
But Tara Spiers-Jones, program manager at the UK Dementia Research Institute, noted that “there is no accepted definition of clinically meaningful effects in the cognitive test they use”.
“It’s not yet clear if the modest reduction in the decline will make a big difference for people with dementia. Longer studies are needed to ensure the benefits of this treatment outweigh the risks,” she added.
The drug also only targets those in the early stages of the disease with a certain level of amyloid formation, limiting the number of people who could potentially use the treatment.
And because Alzheimer’s isn’t always caught quickly, some experts said an overhaul of early detection was needed to ensure more people could benefit from it.
“This isn’t the end of the journey for lecanemab – it will be investigated in further studies to see how well it works over time,” said Richard Oakley, associate research director of the Alzheimer’s Society.
“The safety of drugs is crucial and lecanemab has had side effects, but they are closely scrutinized when decisions are made about whether or not to approve lecanemab to see if the benefits outweigh the risks,” he said.
Biogen and Eisai previously launched Alzheimer’s drug Aduhelm, but there was considerable controversy over the evidence it worked, and its approval led to three high-level resignations from the US Food and Drug Administration.
© Agence France-Presse