Lecanemab (lek-an-e-mab), also called LEQEMBI®, is a drug treatment for Alzheimer’s disease. It is made by the drug company Eisai.
It has been licensed for prescription in England, Scotland, and Wales for people with a confirmed diagnosis of:
- mild or early-stage Alzheimer’s disease.
- mild cognitive impairment who have high levels of a protein called amyloid in their brain.
Lecanemab is not yet available on the NHS. In August 2024, it was rejected for use in NHS England and Wales. A separate decision for Scotland will be made by the Scottish Medicines Consortium (SMC). An outcome is not expected until 2025.
Lecanemab is the first drug licensed in Great Britain that targets one of the underlying disease processes that affects the brain in Alzheimer’s. It is designed to slow down the disease progression. Existing treatments like donepezil, rivastigmine, galantamine, and memantine can relieve some of the symptoms of Alzheimer’s but do not stop it from getting worse.
Lecanemab is not a cure but may allow some people with early Alzheimer’s to live independently and with milder symptoms for longer by slowing the disease down.
Lecanemab has not been approved to treat people with moderate to severe Alzheimer’s. There is currently no evidence that it can treat other types of dementia, such as vascular dementia, dementia with Lewy bodies, or frontotemporal dementia.
Treatment should be initiated and supervised by physicians experienced in the
diagnosis and treatment of Alzheimer’s disease.
The presence of amyloid beta (Aβ) pathology must be confirmed using approved
methods such as amyloid Positron Emission Tomography (PET) scan or cerebrospinal fluid (CSF) analysis prior to initiating treatment. Testing for apolipoprotein E ε4 (ApoE ε4) status should be performed prior to initiation of treatment. The MHRA has decided to exclude people who carry two copies of the ApoE ε4 due to the increased risk of serious side effects.
Lecanemab is a type of drug called a disease-modifying monoclonal antibody.
Antibodies form part of our immune system and bind to harmful proteins to destroy and remove them. Lecanemab contains antibodies that bind to a protein called amyloid, which builds up in the brains of people with Alzheimer’s.
Although our bodies naturally produce antibodies, the specific anti-amyloid antibodies used in this treatment are created in a laboratory.
Other drugs for Alzheimer’s disease, like donepezil, rivastigmine, galantamine, and memantine, are known as 'symptomatic’ treatments. These allow our brain cells to communicate better and mask the damage caused by diseases like Alzheimer’s for a time. Although symptomatic treatments can make a big difference to somebody’s quality of life, they can’t slow or stop Alzheimer’s from getting worse. By directly targeting amyloid, lecanemab can slow down the disease process. You may be prescribed a symptomatic treatment and lecanemab at the same time. There is no evidence for any negative side effects when used in combination.
Lecanemab has been shown in clinical trials to slow down decline in memory and thinking problems for people with mild Alzheimer’s disease and improve quality of life. Data from the trial shows that Lecanemab slowed down memory and thinking getting worse on average by 27 per cent in people taking the drug, compared to people on placebo (dummy drug).
There is no evidence that lecanemab can restore lost memories or make symptoms go away completely. The aim of treatment is that your symptoms decline less over time. This could allow you to live independently for longer. Researchers estimate that over 18 months the drug may slow the progression of the condition by around four to seven months.
The medicines you take for other conditions and your health history may affect whether you can take Lecanemab. Use of Lecanemab in patients who are on anticoagulants (blood thinners, including warfarin) or have been diagnosed with cerebral amyloid angiopathy (CAA) on MRI before starting treatment is contraindicated as the risks in these patients are considered to outweigh the benefits. History of stroke, or seizures within 12 months of screening is also contraindicated. Also, it would not be appropriate to have it if you are allergic to Lecanemab or any of the other ingredients in it or if your MRI brain scan shows small spots of bleeding or fluid in the brain or evidence of larger bleeding in the past.
If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor for advice before you are given this medicine. It is not known if lecanemab will harm your unborn baby or if this medicine passes into breast milk. If you become pregnant while you are using lecanemab, tell your doctor. You and your doctor can discuss if you should carry on with treatment.
If you are breast-feeding, you and your doctor can discuss if you should carry on with breast-feeding or treatment.
Using contraception
Women of childbearing potential must use effective contraception during and up to 3 months after treatment.
All treatments and procedures have risks, and we will talk to you about the risks of Lecanemab. The main risks are:
Infusion-related reactions (IRR)
Some people taking lecanemab have reactions related to the drug being given into the vein. These are called ‘infusion-related reactions’ (IRR) and can happen with many drugs given in this way, e.g., drugs given for cancer.
When something new is injected into your body, your immune system tries to fight it. Usually, this keeps us safe from harmful viruses and bacteria. But our immune system doesn’t know that lecanemab is actually trying to help us. This can produce symptoms such as fever, redness, and itch.
You may be prescribed medicines to help prevent this reaction, such as paracetamol, antihistamines, or steroids.
Around one in four people taking lecanemab experienced infusion-related reactions in trials. Of these, three out of every four people did so only during their first appointment.
ARIA
Lecanemab can also cause a side effect called "ARIA", or amyloid-related imaging abnormalities.
These are brain changes, including swelling (ARIA-E) and bleeding (ARIA-H) within the brain, which are seen on MRI brain scans. While for the most part these are not associated with symptoms or adverse outcomes, they can in some cases be serious.
In trials of the drug, roughly one in eight people developed ARIA. However, most (four in every five) of the people who developed ARIA did not have symptoms.
Symptoms of ARIA may include:
- headache
- confusion
- dizziness
- vision changes
- nausea
- difficulty walking
- seizures.
There were four deaths related to taking lecanemab in the clinical trials. This is less than two in a thousand of the participants who took part in the trial. The specific cause of death in these cases has been debated, with researchers indicating that underlying health conditions and other factors may have contributed.
As with any medicine, the MHRA will keep the safety and effectiveness of lecanemab under close review. Initiation of treatment will be through a central registration system implemented as part of a controlled access programme. A controlled post-authorisation safety study will be conducted to investigate the safety and benefit-risk profile of lecanemab in routine clinical practice, particularly in relation to incidence and severity of ARIAs and intracerebral haemorrhage, and long-term safety
You will have to undergo MRI scans prior to the 5th, 7th, and 14th infusions of lecanemab. Additionally, an MRI scan is recommended prior to the 26th infusion at week 52. There may also be a need for additional MRI scans in cases where there is evidence of ARIA on a planned MRI scan. If you experience ARIA, the severity will dictate your course of treatment. In mild cases where ARIA-E or ARIA-H are detected on MRI but you are not experiencing any symptoms, it is likely you can continue with your regular Lecanemab infusions, but there will be a need for monthly MRIs until the ARIA resolves or stabilises. In moderate to severe cases of ARIA, it will be necessary to pause lecanemab until there is resolution/stabilisation and in instances of severe ARIA-H, the recommendation is that Lecanemab is stopped permanently.
It is very important that patients being treated with lecanemab carry a Patient Alert Card at all times to alert medical staff to this fact. This card includes information on the prescribing service’s 24-hour contact details and highlights important safety information. Anyone who suspects they are having a side effect from this medicine is encouraged to talk to their doctor or clinical nurse specialist. However, if you experience any of the symptoms above that cause you to feel acutely unwell, you should call 999 or go to the nearest A&E as soon as possible. It’s important to get these symptoms checked quickly and to let any doctor you see know that you are taking this medication.
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If you choose not to take Lecanemab, you will be offered the standard course of symptomatic treatment, such as donepezil, rivastigmine, galantamine and memantine.
There is one other disease-modifying drug approved for use in the UK called donanemab. There are 127 drugs currently in clinical trials.
Your doctor will discuss with you if Lecanemab is appropriate for you. Following the screening process (clinical history and examination, cognitive testing, imaging, biomarkers (PET scan or lumbar puncture), and APOE testing. It is important that you understand you will need to attend the hospital every two weeks to receive an infusion and undergo MRI scans prior to the 5th, 7th, and 14th infusions of Lecanemab. Additionally, an MRI scan is recommended prior to the 26th infusion at week 52.
We would also strongly recommend a care partner or family member can accompany you on visits and is with you afterwards should you feel unwell.
We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent and will ask you to sign a consent form. This confirms that you agree to have the procedure and understand what it involves. Staff will explain all the risks, benefits, and alternatives before they ask you to sign a consent form. If you are unsure about any aspect of your proposed treatment, please don’t hesitate to speak with a senior member of staff again.
Patients, care partners, and appropriate family members should understand the requirements for Lecanemab therapy and the potential benefit and potential harm of treatment
You can eat and drink as normal prior to an infusion and take your medications as normal. You will be given a time to attend the ward. You will be seen by a clinical nurse specialist prior to the infusion to ensure it is safe for you to receive the infusion.
An IV cannula will be placed in a vein in your arm. You will then be connected to an intravenous drip of lecanemab. Each infusion is given over one hour. Your blood pressure, heart rate, temperature, and respiratory rate will be monitored regularly during the infusion and afterwards. After the first infusion, you will need to remain on the ward for an observation time of three hours. This is reduced to two hours for the second and third infusions and reduced to 30 minutes thereafter, provided you have not experienced any infusion reactions.
The cannula will be removed before you leave the ward, and you will be given the date for your next infusion.
You will be able to use public transport to go home, provided you feel well enough to do so.
A clinical nurse specialist will call you the day after your infusion to see how you are. You will be provided with their contact details if you have questions regarding your treatment.You may be advised to take regular paracetamol and antihistamine if you experience any infusion-related reactions.
Lecanemab has no or negligible influence on the ability to drive and use machines. Though please avoid driving or operating machinery if you experience dizziness or confusion during treatment with lecanemab.
Your team will arrange MRI scans before your fifth, seventh, and fourteenth doses of lecanemab. This is routine monitoring to check if you have ARIA. Additional scans can be performed at other times during treatment if your doctor thinks you need them. Your treatment may be stopped temporarily, depending on your MRI results. If you miss an infusion of lecanemab, talk to your team to arrange to have it as soon as possible. Do not wait until your next planned infusion.
Page last updated: 10 January 2025
Review due: 30 September 2025