New Alzheimer’s drug, donanemab – what is it and how does it work?

This blog was edited on 19th June 2025 in response to the National Institute for Health and Care Excellence’s final decision for d0nanemab to not become available on the NHS.

On Wednesday 23 October 2024, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has licensed a second drug that can slow down Alzheimer’s disease, called donanemab. This means that the MHRA have decided that donanemab is safe and effective to offer to people with Alzheimer’s in the United Kingdom.

However, donanemab will not become available on the NHS. This decision was based on the costs to the NHS of offering the drug against benefits to people living with Alzheimer’s.

You might remember that they reached this decision for a similar drug, called lecanemab.

We understand this news will be disappointing for many. On this page, we explain more about the decision and the development of these treatments.

In May 2023, pharmaceutical company Eli Lilly & Company (Lilly) released the positive initial results of a clinical trial into a new Alzheimer’s drug, donanemab. Kisunla is the brand name for donanemab, you may also hear it by this name.

Like lecanemab – the first drug licensed in the UK to successfully tackle Alzheimer’s disease itself – the effects of donanemab are modest. But it shows how fast dementia research is accelerating towards life changing treatments.

We know that this news will spark lots of questions. So we’ve answered some of the most commonly asked questions to our Dementia Research Infoline and across our social media channels below.

 

What is donanemab?

Donanemab, like lecanemab, is a type of drug called a monoclonal antibody. Antibodies form part of our immune system and bind to harmful proteins to destroy them.

Donanemab contains antibodies that bind to a protein called amyloid, which builds up in the brain in the early stages of Alzheimer’s disease. This treatment tackles the underlying disease, unlike currently available treatments that can only relieve symptoms.

Scientists have long suspected that clearing amyloid from the brains of people with Alzheimer’s will slow down the disease. Allowing them to live independently and with milder symptoms for longer. The results for both drugs confirm this idea.

Doctors deliver the drug via an infusion into the arm, so people in the trial spent several hours in a clinic once a month. This differs from lecanemab, which doctors deliver every two weeks.

 

 

How effective is donanemab?

Lilly’s TRAILBLAZER ALZ-2 clinical trial showed that donanemab slowed decline in symptoms over a year. This included memory, thinking and ability to carry out daily activities.

The international trial included over 1,700 participants with early Alzheimer’s disease. It tested donanemab against a dummy drug (placebo) to see how well it worked at slowing down the progression of the disease and whether it was safe.

People don’t need to continue taking donanemab once it clears the protein amyloid from the brain, unlike lecanemab, . This means that so far, people don’t need the drug for extended periods of time. In trials, almost half of those taking donanemab were able to stop taking the drug within a year. Participants then switched to the placebo for the rest of the trial.

 

Researchers tested participants against several measures of memory and thinking after one year, and again at eighteen months.

Key results

• Donanemab slowed decline in memory and thinking by around a third (35%) compared with placebo in people with low-medium levels of a protein called tau.

Tau is also associated with Alzheimer’s disease, but builds up later than amyloid. This suggests that donanemab is most effective when given in the earliest stages of Alzheimer’s.

• The symptoms of almost half (47%) of those on donanemab did not get significantly worse over a year on the drug, compared with 29% on placebo.
• In people with low-medium levels of tau the drug also resulted in 40% less worsening in the ability to perform everyday activities, like managing finances, driving and carry out hobbies.
• Donanemab had no significant effect in people with high levels of tau.
• Finally, participants on donanemab had a 39% lower risk of progressing to the next stage of disease compared to placebo over 18 months.

For a small group of around 200 people on the trial who were in the very earliest stage of cognitive impairment, the drug appeared to work very well. However because the number of participants in this group was so small, it’s very hard to be sure that the rate of slowing seen here, 60%, is a ‘real’ result. Nevertheless some newspapers reported this number in their initial headline coverage in May 2023.

Lilly are currently trialling donanemab in a larger group of people with the earliest stages of cognitive impairment to see whether donanemab can really slow down decline by 60%.

 

 

As nine out of 10 participants in the trial were white, we don’t know whether the drug will work the same way in people of other ethnic backgrounds. Unfortunately this is common in medical research studies. Researchers need to conduct more trials to investigate whether donanemab is safe and effective in a diverse population.

We don’t know what the long-term effects of donanemab are as the trial only lasted for 18 months. Future studies carried out by Lilly are looking at the long-term effects of the drug, as well as its effects in people with different stages of Alzheimer’s disease.

• Take part in dementia research

Where can I get donanemab?

Donanemab is not available on the NHS. Certain specialist private healthcare services have begun to offer the drug at select clinics.

Donanemab is advertised at between £60,000 – £80,000 per year. However, it’s important to note that there are still ongoing clinical trials which allow some people who meet certain criteria to access the drug free of charge. Contact us for more information about these at infoline@alzheimersresearchuk.org or call 0300 111 5111.

Unlike lecanemab, people taking donanemab can stop treatment once their amyloid levels fall below a threshold, or after 18 months. This could mean that the long-term costs of donanemab are lower than lecanemab.

The overall cost of donanemab for each person will depend on how long they are on it.

Is donanemab available on the NHS?

In June 2025, NHS’s decision-makers, the National Institute of Health and Care Excellence (NICE) rejected donanemab for use in England and Wales. The Scottish Medicines Consortium (SMC) in Scotland also reached the same decision.

Why isn’t donanemab available on the NHS?

The costs of donanemab extend beyond the cost of the drug itself. The way people experience diagnosis would have to change drastically to offer a drug like donanemab.

People considering donanemab must undergo testing in two distinct areas: during diagnosis and throughout their course of treatment.

During diagnosis

As it stands only one in every 50 people who receive a diagnosis of Alzheimer’s have had the in-depth testing required to find out if they are suitable for a drug like donanemab. For people to find out if they can access donanemab, the NHS would need to overhaul how they diagnose dementia. This would include:

• Setting up specialist clinics to diagnose Alzheimer’s.
• Performing regular PET scans or lumbar punctures to test for amyloid.
• Genetic testing for APOE4. You can find out more about APOE4 by scrolling down to the “Is donanemab safe?” section of this page.

Existing GP practices and memory clinics would experience higher demand, as people may be more likely to come forward with concerns about their memory and thinking if there is a treatment that can slow Alzheimer’s available. It’s well-known how stretched these services already are. So, the government would also need to invest more in these services.

People with dementia deserve access to an early and accurate diagnosis, whether they’re considering taking a new treatment or not. Experts debate whether or not these associated costs should be considered part of the wider ‘treatment cost’. With one in three people with dementia in the UK never receiving a formal diagnosis, there is a clear need for change regardless of whether new treatments become available on the NHS.

Collecting more data will be key to addressing the uncertainties that NICE have raised. That’s why Alzheimer’s Research UK, Alzheimer’s Society, Dementia UK, Alzheimer Scotland and the Royal College of Psychiatrists, have come together to call on the NHS for mandatory data collection outside of clinical trial settings.

We are also working to bring forward blood tests for Alzheimer’s, which can detect amyloid and diagnose Alzheimer’s earlier. We hope that this will be key to moving the dial on how memory services operate, and ultimately help diagnose people more accurately, earlier and more affordably.

During treatment

If someone is eligible to take donanemab, there are several more costly factors that the NHS currently don’t have the facilities to deliver, including:

• Monthly intravenous infusions of donanemab.
• Regular MRI brain scans during treatment.
• Routine follow-up appointments every three months.
• Regular monitoring for side effects, including brain swelling and bleeds.

Since donanemab’s effects on Alzheimer’s disease progression are modest, NICE decided that the UK’s health system would not benefit enough to outweigh the significant financial costs of overhauling how doctors currently diagnose and treat people with Alzheimer’s.

 

Who is eligible for donanemab?

Donanemab has been designed for people in the early stages of Alzheimer’s disease. It is only available for people with a diagnosis mild Alzheimer’s disease or mild cognitive impairment (MCI) with evidence of amyloid build up in the brain. This must be confirmed by a spinal fluid test (lumbar puncture) or a PET brain scan.

Many experts suspect donanemab would be unlikely to work in the later stages of Alzheimer’s disease, when levels of tau tend to be higher, although this hasn’t been tested in trials yet.

Unfortunately, this means for the majority of people living with Alzheimer’s now, the treatment is not suitable as most people currently receive a relatively late diagnosis.

We need to see improvements in earlier diagnosis to ensure people eligible for the treatment can be identified. This would include more widely available amyloid testing via lumbar puncture and PET scans so that doctors are able to tell who in the UK is eligible for the treatment. These changes to early diagnosis would result in thousands more people being eligible to receive donanemab.

People with a suitable diagnosis and amyloid in their brain will also have a genetic test to look for the APOE4 gene. People with two copies of APOE4 are at higher risk of developing side effects, like brain swelling and bleeds (known as ‘ARIA’). They will not be eligible for the drug due to safety concerns. You can find out more about this in the next section.

People with cerebral amyloid angiopathy are not suitable for donanemab due to safety concerns. Similarly, people taking anticoagulants are not suitable for donanemab due to an increased risk of brain swellings and bleeds.

Is donanemab safe?

Both lecanemab and donanemab cause a concerning and poorly understood side effect called ARIA (which stands for ‘amyloid related imaging abnormalities’). The name describes changes to brain structure and swelling or bleeding, seen on MRI brain scans, which for some can be serious.

In patients receiving donanemab brain swelling was seen on the scans of one in four participants, with one in 20 experiencing symptoms.

According to Lilly, less than two in every 100 participants experienced serious brain swelling after taking donanemab. However this included two participants whose deaths were attributed to the condition and a third who died after an incident of serious brain swelling.

Doctors observed brain bleeding in around one in three of the donanemab group and around three in every 20 in the placebo group.

 

 

In the general population two in every 100 people inherit two copies of APOE4. As the gene increases our risk of developing Alzheimer’s, 15 in every 100 people with the condition have two copies.

People with two copies of APOE4 are more likely to experience ARIA. In the TRAILBLAZER-ALZ 2 trial, around eight in 20 people with two copies of the APOE4 developed brain swelling (ARIA-E) compared to three in every 20 people with no copies of APOE4 on donanemab.

Nevertheless, scientists poorly understand ARIA, including whether it can become more serious over time. So, longer-term studies closely monitor the risk associated with drugs like donanemab and lecanemab, and regulators will consider this risk when deciding whether to approve these drugs.

Beyond ARIA, other side effects people taking donanemab had included reactions from the intravenous drip needed to give the infusion, which is not uncommon with this type of drug.

Ongoing studies are investigating its safety further.

Will this drug work on other types of dementia, such as vascular dementia or dementia with Lewy bodies?

At the moment donanemab is only intended for people with Alzheimer’s disease. That’s because it targets amyloid, which scientists believe plays an important role in the development of Alzheimer’s. It is not thought to be as important in other types of dementia, so it is unlikely to work against other diseases that cause dementia.

Beyond donanemab, there are over 130 drugs in clinical trials across the world investigating treatments for all types of dementia. At Alzheimer’s Research UK, we believe it is a question of when, not if, treatments for other types of dementia will become available.

How are the drugs that target amyloid, like lecanemab and donanemab, different?

Amyloid plaques build up in the brain in stages. Different anti-amyloid drugs bind to the protein at different stages. We still don’t know why this makes some drugs more effective at treating symptoms than others.

Lecanemab targets amyloid as it begins to form fibres, whereas donanemab binds to amyloid once these fibres have clumped together to become a larger plaque in the brain.

 

 

 

Donanemab is the second drug shown to tackle the underlying disease itself and slow the development of Alzheimer’s disease. However we can’t compare these drugs directly as the two trials are very different. So it’s impossible to say anything concrete.

At what stage of diagnosis could donanemab be given?

Donanemab is designed for people in the early stages of Alzheimer’s disease. People included in the trials of this drug had mild cognitive impairment or mild Alzheimer’s disease, confirmed by a test of their spinal fluid or a PET brain scan showing a build-up of amyloid in their brain. Many experts suspect that it is unlikely to work in later stages of the disease, although trials haven’t tested this yet.

How will donanemab’s approval change dementia research in the UK?

We believe that this decision to licence a second drug that slows Alzheimer’s will:

• Further strengthen the UK’s international reputation as a leader in dementia research.
• Attract even greater commercial investment in UK clinical trials.
• Speed up the need for quicker and more accurate diagnosis methods, like blood tests.
• Ultimately benefit the one in two of us who will either develop dementia in the future, care for someone who has it, or both.

Now that research shows the diseases causing dementia can be slowed, researchers have sparked renewed hope and trust in their work. In turn this will attract more money from drug companies, encourage more people to take part in studies and speed up research towards a cure.

How can I get involved in a trial?

The best way to find out about taking part in dementia research studies, including clinical trials, is through a nationwide register called Join Dementia Research. When you register, you provide personal details about your health, age, and contact information, and the system matches you to suitable studies based on these details.

Signing up to the register is not a commitment to take part in any particular study, it just allows research studies to find willing volunteers.

Currently, there is a donanemab trial recruiting through Join Dementia Research. You can register to Join Dementia Research here.

You can also find out more by calling the Dementia Research Infoline on 0300 111 5 111 (9-5pm Monday to Friday).

If you have recently been diagnosed with mild cognitive impairment or Alzheimer’s disease and would like to share your story to inspire others or help shape our work please get in touch via stories@alzheimersresearchuk.org

Neither lecanemab nor donanemab will become available on the NHS. While we shouldn’t question the safety or effectiveness of the drug, which the MHRA decision is based on, we should question the cost-effectiveness of the drug when the decision doesn’t represent the overall cost of dementia to society.

In 2024 the total cost of dementia to the UK economy was an estimated £42 billion.

Unpaid care, often provided by loved ones, accounts for 50% of dementia costs. The second highest costs fall under social care, with the price of caring for someone with severe dementia three times higher than mild dementia.

 

 

As more people receive diagnoses, they expect the overall cost of dementia to rise to £90 billion by 2040. NICE’s decision is not based on the wider costs of Alzheimer’s disease to society as a whole. Alzheimer’s Research UK, amongst other experts, have raised this concern to NICE following their provisional rejection of lecanemab. We hope that this will open the door to change.

At Alzheimer’s Research UK, we won’t rest until we have found cures for the diseases that cause dementia. Although drugs like donanemab and lecanemab are promising, their effects are modest and they don’t stop the disease from progressing entirely. We’ll likely need to combine these drugs with others that target other underlying disease processes beyond amyloid, to make real progress in stopping dementia.

So we need to keep exploring other treatment avenues in order to find the next generation of effective treatments. Initiatives like our Drug Discovery Alliance, which brings together world-leading scientists from the Universities of Oxford and Cambridge, and University College London, are crucial to unlocking these other routes to treating Alzheimer’s and other types of dementia. You can hear about emerging treatments from some of the researchers themselves, in our recent Online Public event here.

If you have recently been diagnosed with dementia, have previously, or are currently taking part in a clinical trial and would like to share your story to inspire others or help shape our work please get in touch via stories@alzheimersresearchuk.org