Research

What is lecanemab?

In August 2024, lecanemab (marketed as Leqembi in the UK) was approved as a treatment for some people living with early Alzheimer’s disease. The drug can slow down the decline in memory and thinking skills of people living with early Alzheimer’s disease.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) determine the safety and effectiveness of a drug whilst the National Institute for Health and Care Excellence (NICE) assess clinical and cost-effectiveness and decide if a drug can be prescribed through the NHS.

NICE has made a final recommendation that lecanemab will not be provided through the NHS after an extended review and stakeholder consultation.

Another similar drug called donanemab (marketed as Kisunla) has also been approved by the MHRA. Similarly, after extended review, NICE has not recommended donanemab be provided through the NHS.
 

The MHRA’s approval of the first safe and effective Alzheimer’s disease treatment, shown to slow progression, was a defining moment. There is no doubt that the final NICE decisions on lecanemab and donanemab are a setback for people living with dementia but with over 130 Alzheimer’s disease drugs in clinical trials, over 30 of which are in late-stage clinical trials, more new treatments are on the horizon and could be submitted to regulators within the next few years.”

What is lecanemab?

Lecanemab (brand name Leqembi) is a disease-modifying drug, which means that it was developed to tackle the causes of Alzheimer’s disease rather than only relieving the symptoms.

It targets a protein called amyloid. The importance of this protein in the development of Alzheimer’s disease was discovered by Alzheimer’s Society funded research led by Professor Sir John Hardy over thirty years ago. It laid the foundations for billions of pounds of investment into many drugs like lecanemab, with over 130 other drugs currently being tested in clinical trials.

Lecanemab is a disease-modifying immunotherapy drug. Immunotherapies are already used in medicine, for example in the treatment of some cancers. More specifically, lecanemab is an antibody treatment. Antibodies already exist in the human body – they are a type of protein produced by the body’s immune system to fight against disease.

It uses antibodies to recognise amyloid in the brain and works with the brain’s immune cells to clear amyloid protein build-up from the brains of people living with early-stage Alzheimer’s disease. These amyloid protein build-ups are thought to be toxic to brain cells, causing them to get sick and eventually die, leading to the symptoms of Alzheimer’s disease. 

Lecanemab is given to patients intravenously, which means into a vein through a drip bag.

How can I access lecanemab?

The MHRA has granted a license for lecanemab to be available in the UK. In the UK, lecanemab is marketed under a brand name Leqembi.

The MHRA has approved lecanemab for people at the early stages of Alzheimer’s disease. This excludes:  

• people with moderate or late-stage dementia caused by Alzheimer’s disease
• those with other forms of dementia such as vascular dementia, Lewy body dementia or frontotemporal dementia
• people who carry two copies of the APOE4 gene variant

The MHRA makes decisions based on the safety and effectiveness of drugs, and in their review of the available data, have chosen to make these exclusions due to the higher risk of side effects in these individuals.

Lecanemab is now available through some private health providers.  

Will it be available on the NHS?

The National Institute for Health and Care Excellence (NICE) decide which medicines should be made available on the NHS.  Whilst the MHRA has approved lecaneamb, guidance from NICE has not recommended it for use on the NHS as it does not meet NICE’s cost effectiveness threshold.   

Does lecanemab work?  

The MHRA’s decision to approve lecanemab shows that it is safe and effective for use as treatment of early-stage Alzheimer’s disease. The MHRA will have reviewed results from clinical trials to make their decision.

The clinical trial was carried out by Eisai. The results of lecanemab’s phase 3 clinical trial, called Clarity-AD, were shared at the Clinical Trials on Alzheimer’s Disease (CTAD) conference in San Francisco.

Clarity-AD was a phase 3 clinical trial involving 1,795 people. The trial involved people living with early-stage Alzheimer’s disease who have amyloid protein build-ups in their brains. Half the participants were given lecanemab and half received a dummy drug over 18 months.

The trial showed that lecanemab slowed down the speed at which memory and thinking skills got worse by 27% in people taking the drug compared to people on the dummy drug.

The research team also found that the drug reduced loss of quality of life by up to 56%.

Importantly, the drug reduced the amount of amyloid protein present in the brain. Amyloid protein levels were also reduced in the blood and spinal fluid.  

Is lecanemab safe?

As part of the approval process, the MHRA scrutinised the lecanemab safety data and decided that lecanemab is both safe and effective as a treatment for early-stage Alzheimer’s disease. However, like all drugs, lecanemab was found to have some side effects. Some of these side effects are serious.

During the clinical trial, some people taking lecanemab experienced reactions to having the drug infused, while some others were found to have swelling or microbleeds in the brain in response to lecanemab. These are known as Amyloid Related Imaging Abnormalities or ARIA. There have also been three deaths related to taking lecanemab in the clinical trial and extension phase. This is less than 0.2% of the participants in the trial. The majority of people who experienced ARIA had no symptoms and these changes in the brain were only detected using MRI brain scanning.

The MHRA will continue to monitor the safety and effectiveness of lecanemab in the future. Patients who receive lecanemab as treatment can report any adverse effects through MHRA’s Yellow Card Scheme.  

Are there other treatments available?

Currently, there is no cure for dementia. However, we are at an exciting time in dementia research and there are promising new drugs on the horizon.

Along with lecanemab, another drug that targets amyloid, called donanemab has also been approved by the MHRA for use in the UK. Like lecanemab, donanemab is not recommended for use on the NHS.  

Successful clinical trials have confirmed our understanding of the underlying disease mechanism, helping us to target future research to develop new and better treatments that are more effective, easier to administer and with fewer side effects. Lecanemab will be succeeded by many more dementia treatments.  

There are over 130 drugs currently in clinical trials.  

Patients can also access medications to ease dementia symptoms, as well as other treatments and support that do not involve medication, such as talking therapies. You can read more about alternative treatment options here.  

What does this mean for the future and for people affected by dementia?

The approval of lecanemab by the MHRA was a defining moment for dementia. However, the NICE recommendations for lecanemab and donanemab is of course, a setback for people with dementia who might have been eligible.

We still believe we are heading towards a future where disease-modifying treatments reduce the devastation caused by dementia and there are three steps that will be critical for preparing for new treatments. 

Firstly, the UK government must commit to long-term investment to transform dementia diagnosis. Lecanemab is most effective in the early stages of disease, therefore it is important to diagnose Alzheimer’s disease early. The reality is that, if a disease-modifying treatment was approved for use on the NHS tomorrow, too many people with dementia wouldn’t be able to access it as currently more than a third of people with dementia don’t get a diagnosis. 

Secondly, we will be encouraging NICE, and relevant research and clinical communities, to identify learnings from the process of assessing these first disease-modifying treatments.

And thirdly, it is important that real world data from private access to lecanemab and donanemab in the UK is collected and that learnings from implementation of these treatments in other countries are shared, to improve our understanding of the drugs’ effectiveness and safety in real world populations. 

Research will beat dementia. It’s important to recognise that lecanemab and donanemab are first generation treatments, and in other conditions we have seen treatments become cheaper, safer and more effective as research continues. We hope to see similar progress in Alzheimer's disease in the months and years ahead.

How can I access further support?  

The news about lecanemab might be overwhelming. No matter the issue, we are here for you. You can access our dementia support services on our website.  

We also operate a dementia support line, where you can access personalised information, support, and advice. Phone support is available 7 days a week by calling 0333 150 3456.  

We will update this page as new information becomes available. Last updated: 19 June 2025.