Lecanemab (Leqembi) and donanemab (Kisunla) are antibody drugs that clear amyloid from the brain. They are licensed in the EU and the UK for early Alzheimer's disease. That means mild cognitive impairment or mild dementia, with amyloid confirmed by a scan or spinal fluid test, in people with one or no copy of the APOE4 gene.
Neither drug is routinely available through the HSE or the NHS. As of November 2026, NICE has not recommended either drug, and its evaluations are paused while the companies hold price talks with NHS England. In Ireland, the National Centre for Pharmacoeconomics recommended in October 2026 that lecanemab not be reimbursed, and the HSE has yet to decide. Donanemab's Irish assessment is still waiting for the company's submission.
In trials, both drugs slowed decline modestly over 18 months. Both carry a risk of brain swelling and small bleeds, called ARIA, which needs regular MRI scans to detect.
Both are monoclonal antibodies given by drip into a vein. Lecanemab is given every two weeks and donanemab every four weeks, according to the European Medicines Agency.
They target amyloid, one of the two proteins that build up in Alzheimer's. Our explainer on what happens in the brain in Alzheimer's covers the biology and the pooled trial evidence in more depth.
They are not a cure. They do not reverse memory loss. They are not for moderate or severe dementia, and they are not licensed for people without symptoms.
Both drugs reduced decline compared with placebo, and the results were statistically significant. But people on the drugs still declined. The differences are small on scales that run to 18 or 144 points.
NICE's committee concluded that the benefits were too small to justify the cost to the NHS. Whether patients and families would notice the difference over 18 months is still debated. Three 2026 meta-analyses, summarised on our Alzheimer's explainer, put the effect at or below the threshold usually considered clinically meaningful.
For donanemab, the main analysis was in people with low or medium levels of tau, another Alzheimer's protein. Benefit in the combined group, including high tau, was smaller.
ARIA stands for amyloid-related imaging abnormalities. There are two kinds:
Most ARIA causes no symptoms and is found only on scheduled MRI scans. When symptoms occur, the US lecanemab label says they may include headache, confusion, visual changes, dizziness, nausea and difficulty walking. The US labels for both drugs carry a boxed warning that ARIA can be serious, life-threatening and occasionally fatal. Bleeds larger than 1 cm, some fatal, have occurred with this class of drugs.
The FDA label also warns that ARIA-E can mimic a stroke. Doctors should consider ARIA before giving clot-busting treatment to someone on these drugs. Anyone on treatment should carry the patient alert card the EU requires the companies to provide.
APOE4 is a gene variant that raises the risk of Alzheimer's. People can carry none, one or two copies. The MHRA says about 15% of people diagnosed with Alzheimer's carry two copies.
For lecanemab, the MHRA reports ARIA risks from Clarity AD of 45% in people with two copies, 19% with one copy and 13% with none. On placebo, the figures were 22%, 9% and 4%. The MHRA says benefit in people with two copies was uncertain.
For donanemab, the MHRA reported symptomatic brain swelling in 4.1% of non-carriers, 6.1% with one copy and 7.7% with two. Serious ARIA occurred in about 0.7%, 1.7% and 3% respectively.
That is why the EU and UK licences exclude people with two copies. A genetic test is needed before treatment. Learning your APOE4 status can have implications for relatives, so it is worth discussing before testing.
Based on the EU licences and the EMA's summaries, a person would need:
The EMA says the drugs must not be used in people on anticoagulants or with poorly controlled bleeding disorders. They must also not be used if the MRI shows previous brain bleeds, more than 4 microbleeds, superficial siderosis, brain swelling, or other signs of amyloid in blood vessel walls.
Amyloid is usually confirmed by an amyloid PET scan or a lumbar puncture to test spinal fluid. Newer p-tau217 blood tests are being used in diagnosis, but the US lecanemab label says amyloid must be confirmed before treatment starts.
Most people with memory problems would not qualify. That page describes a Swedish primary care study in which only about 13% to 14% of patients met the criteria.
Treatment is demanding for patients and families, and for health services.
Our guide to brain MRI explains what a scan involves.
The EU also requires a controlled access programme, so the drugs are used only in the approved group. It requires an EU-wide registry-based safety study too.
The NCPE completed its lecanemab assessment on 13 October 2026. It recommended that lecanemab "not be considered for reimbursement". The HSE will consider that report, along with a patient organisation submission, when it makes its decision.
For donanemab, a rapid review in December 2025 found a full assessment was needed. As of November 2026, the NCPE was awaiting the company's full submission.
We found no HSE decision to fund either drug. We found no published information on access outside clinical trials in Ireland.
NICE issued final draft guidance against both drugs in June 2025, its third negative decision on each, according to the Pharmaceutical Journal. The manufacturers, Eisai and Eli Lilly, appealed. The appeal panels upheld some points (two for lecanemab, four for donanemab) and sent the guidance back to the committee.
New draft guidance for lecanemab and for donanemab, issued in March 2026, still did not recommend them. The committee met again on 8 July 2026. Later that month, NICE paused both evaluations because the companies and NHS England had started commercial discussions, according to the lecanemab and donanemab project pages.
So, for now, neither drug is routinely available on the NHS in England. NICE is also looking at donanemab for people without symptoms, but that topic is awaiting development.
We did not check the separate position in Scotland.
We have not listed trials. If you are interested in research, ask your memory clinic. A trial is research, not a treatment option.
If you are worried about memory, start with your GP. Our guide to memory worries explains what is and is not typical with age, and our mild cognitive impairment guide explains what that diagnosis means.
Questions worth asking a specialist:
The Alzheimer Society of Ireland runs a national helpline on 1800 341 341, according to its website.
A diagnosis can be hard to take in. If you or someone close to you is struggling or has thoughts of suicide, call Samaritans free on 116 123 in Ireland or the UK, or text 50808 in Ireland. In an emergency, call 112 or 999.
Not at present. The NCPE recommended in October 2026 that lecanemab not be reimbursed, and the HSE has not announced a decision. Donanemab's Irish assessment has not been completed.
Not routinely. NICE has not recommended either drug. Its evaluations were paused in July 2026 for commercial discussions with NHS England.
Their risk of ARIA, including serious ARIA, is higher, and the benefit was uncertain. The EU and UK regulators therefore licensed the drugs only for people with one or no copy.
No. In trials, people on the drugs still declined, but somewhat more slowly than on placebo over about 18 months. They do not restore lost memory.
This article is general information, not medical advice. Talk to your GP or specialist about your own situation.
Reviewed by: Proco Team
Last updated: November 2026