Alzheimer’s disease is the most common form of dementia, but there are other types, like vascular, Lewy body and frontotemporal dementia. Some people are diagnosed with several forms at once.
It can be heartbreaking for loved ones to see their relatives’ memories gradually fade. Other symptoms, like behavioural or mood changes, make Alzheimer’s disease and other forms of dementia a challenge to manage.
Until recently, treatments could only control symptoms, rather than tackle the underlying causes of dementia. Now, two new drugs – lecanemab and donanemab – could mark a turning point in cognitive impairment therapy.
We’ll explore how they work and reveal when they might become available in the UK below.
What’s new: the latest treatments for dementia
Lecanemab and donanemab both show promise in the treatment of early stage Alzheimer's disease, but don’t work for other types of dementia. Both drugs target amyloid-beta plaques in the brain – but they do so in different ways and at different stages of plaque formation.
In late 2022, American biotechnology company Biogen and Japanese pharmaceutical company Eisai presented the results of an 18-month-long phase three trial on lecanemab at the Clinical Trials on Alzheimer's Disease conference in San Francisco.
Altogether, 1,795 participants with early stage Alzheimer’s disease took part in the double-blind study. Half were given lecanemab as an infusion every fortnight, while the remaining half got a placebo.
At the end of the trial, people who'd received lecanemab infusions had 27% less cognitive decline than those who hadn’t. Researchers estimated the drug slowed progression of Alzheimer’s symptoms by about seven months over the course of the study.
Here’s what you need to know about lecanemab:
- It’s a type of immunotherapy treatment – specifically, an antibody treatment.
- The drug works with the immune system, binding to types of amyloid-beta as they begin to form fibres and plaques in the brain.
- It works best for people in the early stages of Alzheimer’s disease.
- Side effects can include brain swelling and microbleeds in the brain, which don’t usually cause symptoms, but which can be serious.
- It’s given as an intravenous infusion, usually once every two weeks.
In the United States, the FDA approved lecanemab for use in January 2023: it’s currently being marketed as LEQEMBI.
At the moment, lecanemab isn’t approved for use in the UK, but Esai has applied to the Medicines and Healthcare Products Regulatory Agency (MHRA), so it might become available on the NHS in 2024.
In July 2023, JAMA journal published the results of an 18-month-long phase three clinical trial involving Eli Lilly’s donanemab antibody treatment. In total, 1,736 people aged between 60 and 85 with early stage Alzheimer’s disease took part.
Half the study participants received a donanemab infusion while the other half got a placebo every month during the trial. At the end of the study, people who’d received donanemab had 35% less cognitive decline than those who’d been given the placebo.
Encouragingly, some of the participants who were given donanemab stopped receiving infusions after only a year because the treatments were so effective at removing amyloid plaques.
Here are some quick facts about donanemab:
- Like lecanemab, donanemab is an antibody treatment.
- Donanemab works with the immune system to target amyloid plaques that have already formed in the brain.
- It’s most effective in people who have mild Alzheimer’s symptoms.
- Side effects include brain swelling, which usually resolves on its own, but which can be serious: four people who took part in the study died.
- It’s given as an intravenous infusion once every month.
Donanemab isn’t available in any country yet, but Eli Lilly has applied for FDA approval in the United States and will apply for approval in the UK soon. If approved, it could become available on the NHS in 2025.
The roundup on amyloid beta-focussed treatments
Researchers measured progress by looking at what people were able to do throughout the trials. They also took MRI scans to compare participants’ brains before, during and after the studies.
At the end of both trials, MRIs showed fewer amyloid plaques in the brains of people who'd taken lecanemab and donanemab. People who'd taken the drugs were also able to do more meaningful things than participants who’d been given placebos: for example talk about current events, play games, go shopping, cook, have conversations and interact with loved ones.
It’s important to understand that neither drug is a quick fix: both need time to begin working. Side effects like brain swelling have to be taken seriously, too. We also don’t know yet how they’ll perform over time – they might continue to remove amyloid buildup, or they might stop working after a while.
A reason to hope
Newer drugs like lecanemab and donanemab represent real progress in the fight against Alzheimer’s disease, but they’re not for everyone. To benefit, people need to be in the beginning stages of the disease. However, other immunotherapy drugs suitable for people in the more advanced stages of Alzheimer’s disease might become available in the future.
Overall, there are lots of reasons to feel hopeful about dementia and memory loss treatment. As Dr Susan Kohlhaas, Executive Director of Research and Partnerships at Alzheimer’s Research UK says, “The outlook for dementia and its impact on people and society is finally changing.” We’re excited to follow along – and we’ll report back on future study results as they emerge.
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