Lecanemab, Donanemab & Disease Modifying Therapies

Last updated 16/12/2025

In the last few years, you may have come across the name lecanemab in the news or in conversations about new dementia treatments. On 15th April 2025, the European Commission granted EU authorisation for Leqembi (lecanemab), a treatment for people with mild cognitive impairment or early-stage Alzheimer’s disease. This decision was made under strict conditions and marks an important moment in dementia research.  

Lecanemab is the first medicine of its kind to be authorised in the EU, offering a way to slow the decline in memory and thinking for people in the early stages of the condition. 

Lecanemab is known as a disease-modifying treatment.

This means it aims to address the underlying processes that drive Alzheimer’s disease, rather than simply helping to ease the symptoms. 

What Is the Difference Between Leqembi and Lecanemab? 

You may have heard the media discussing Leqembi. Leqembi is the brand name of the drug lecanemab, that was developed by the pharmaceutical companies Biogen and Eisai. 

How Does Lecanemab Work? 

People with Alzheimer’s disease have a build-up of a sticky, toxic protein called amyloid in the brain. Over time, this build-up is thought to harm brain cells, causing them to become sick and eventually die, which leads to the symptoms of Alzheimer’s disease. 

Lecanemab is designed to help with this process. It is a type of immunotherapy, similar to treatments already used in some other areas of medicine (such as cancer).  

More specifically, it’s an antibody-based treatment. Antibodies are proteins that the immune system naturally uses to recognise and fight harmful substances. Lecanemab uses laboratory-made antibodies to work with the brain’s own immune cells to help clear these toxic protein build-ups (amyloid) in people with early-stage Alzheimer’s disease. 

Who Is Lecanemab For? 

Lecanemab has been approved by the European Commission for treating adults with mild cognitive impairment (memory and thinking problems) and in the early stages of dementia due to Alzheimer’s disease.  

Is Lecanemab Approved for Everyone with Dementia? 

Lecanemab is approved for:

• People with early-stage Alzheimer’s disease or Mild Cognitive Impairment
• People who carry none or only one copy of the APOE4 gene variant 

Lecanemab is NOT APPROVED for use in:

• People with moderate or late-stage dementia caused by Alzheimer’s disease
• People 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 

Your doctor may carry out a variety of other tests to determine if lecanemab is right for you.   

Is Lecanemab Available in Ireland? 

As of 15th April 2025, the European Commission has recommended this drug for marketing authorisation in the EU. To our knowledge, lecanemab is not currently available to access in Ireland. It is available in some other European countries such as Germany and Austria. 

How Can I Access Lecanemab? 

Currently lecanemab is not available in Ireland. 

How Well Does Lecanemab Work? 

It is thought that lecanemab slows the progression of Alzheimer’s Disease by approximately 4-6 months.  

What Does Research on Lecanemab Tell Us? 

Approximately 1,795 patients with early-stage Alzheimer’s were treated using lecanemab as part of a Phase 3 clinical trial (CLARITY-AD).  This compared people receiving lecanemab to people on a dummy drug (placebo) over 18 months. 

What Did the Trial Show?

• Slower worsening of symptoms: The trial showed that lecanemab slowed down the rate at which memory and thinking skills got worse (by 27% in people taking the drug compared to people on the dummy drug).
• Better quality of life: The treatment reduced the loss of quality of life by up to 56%.
• Lower amyloid levels: Lecanemab significantly reduced amyloid protein build-up in the brain, as well as in the blood and spinal fluid. 

Early results in 2025 from an extension of the study show that participants receiving lecanemab continued to experience a slowing of clinical decline, along with a reduced rate of amyloid reaccumulating. 

How Is Lecanemab Given? 

Lecanemab is given to patients intravenously, which means into a vein (usually in the arm) through a drip bag. It is usually given every two weeks. 

Is Lecanemab Safe?  

The European Medicines agency scrutinised the safety data on lecanemab and decided that lecanemab is safe as a treatment for early-stage Alzheimer’s disease if certain conditions are met.  

However, all drugs can have some side effects and sometimes, these side effects can be serious. 

What Are the Known Side Effects/Risks of Lecanemab? 

Common side effects are flushing, chills, fever and headache.

Serious and Controversial Side Effects: ARIA

The most controversial side effects are amyloid-related imaging abnormalities (ARIA), which are known to occur with treatments using antibodies like lecanemab. 

In the U.S., lecanemab carries a prescribing warning for ARIA. Not all patients experience ARIA, and some patients may have ARIA without any symptoms.  Features of ARIA may include:

• Temporary brain swelling
• Small brain bleeds
• Headaches
• Confusion
• Visual disturbances 

Reported Deaths

In rare cases, ARIA can be life-threatening. 

There have been three deaths related to lecanemab during the clinical trial and its extension phase. 

Why Did the European Commission Approve Lecanemab if It Has Known Risks? 

All medicines come with potential side effects, and lecanemab is no exception. When the European Commission reviews a new treatment, it carefully weighs the potential benefits against the possible risks. In this case, the evidence showed that, for the right group of people, the benefits of slowing early Alzheimer’s disease outweighed the known risks. 

The approval also includes strict eligibility criteria to ensure the treatment is offered only to people who are at the lowest risk of serious side effects. 

Not everyone who takes lecanemab will experience these side effects, and ultimately, deciding whether to start treatment is a personal decision, made in consultation with a medical team who can explain the risks, benefits, and what they mean for your individual circumstances. 

What Tests/Precautions Are Required Before Receiving Lecanemab? 

ARIA is typically monitored using MRI scans, with a baseline scan at the beginning and then regularly during treatment to check for any changes. 

People on blood thinning medication may be at higher risk of developing ARIA and should consult their doctor to determine if lecanemab is appropriate for them. 

Your doctor will also carry out a variety of other tests to monitor you.   

Are There Any Alternatives to Drugs Like Lecanemab? 

There is currently no cure for dementia, but we are in an encouraging period for dementia research. Recent successful clinical trials have strengthened our understanding of how the disease develops, helping to guide future work on treatments that may be more effective and have fewer side effects. 

Lecanemab is likely to be the first of many new dementia treatments on the way. 

People living with dementia can also be prescribed medications that help ease symptoms, supporting memory, thinking, and day-to-day wellbeing.  You can read more about other treatment options here.   

Additionally, there are a variety of non-pharmacological  (non-drug) therapies that help people with their daily experience of dementia.  

There has been another recently approved drug that works in a similar way to lecanemab – donanemab, and you can read more about it further below on this page.  Donanemab currently is not available in Ireland. 

What Is the Difference Between Lecanemab and Donanemab? 

There are many similarities between these drugs. Both are immunotherapies that target the build-up of amyloid in the brain. However, lecanemab targets amyloid earlier in the process as it begins to form fibres whereas donanemab targets an insoluble form of amyloid once these fibres have clumped together to form a build-up of plaque in the brain. 

How Can I Get Further Support? 

Hearing about new treatments like lecanemab can feel overwhelming, and it’s natural to have questions. We are here to support you. You can access our dementia support services on our website. 

We offer a National Helpline, where our trained team provides personalised information, guidance and advice. While we can’t provide medical or clinical guidance, we can help you navigate available supports and signpost you to services. 

Phone support is available by calling 1-800-341-341, and webchat support is available online. 

This page will be updated as new information becomes available. 

Other Media

17th April 2025 – Dr. Laura O’Philbin wrote an Op-Ed article for The Irish Examiner. Read here, or you can download and read here.

Last updated 16/12/2025 

In recent years, you may have heard about donanemab as a promising development in dementia treatment. In September 2025, the European Commission granted EU authorisation for Kisunla (donanemab) for people with mild cognitive impairment or early-stage Alzheimer’s disease. This approval followed an initial rejection and came after further review, marking another significant step forward in Alzheimer’s research. 

Donanemab is the second medicine of its kind to be authorised in the EU, following lecanemab. It offers another option that can help slow the decline in memory and thinking for people in the early stages of Alzheimer’s disease.

What Is Donanemab? 

Donanemab is known as a disease-modifying treatment.
This means it aims to address the underlying processes that drive Alzheimer’s disease, rather than simply helping to ease the symptoms. 

What Is the Difference between Kisunla and Donanemab? 

You may hear people mention Kisunla when they talk about donanemab. Kisunla is the brand name of the drug donanemab, that was developed by the pharmaceutical company Eli Lilly. 

How Does Donanemab Work? 

People with Alzheimer’s disease have a build-up of a sticky, toxic protein called amyloid in the brain. Over time, this build-up is thought to harm brain cells, causing them to become sick and eventually die, which leads to the symptoms of Alzheimer’s disease. Donanemab is designed to help with this process. It is a type of immunotherapy, similar to treatments already used in some other areas of medicine(such as cancer).  

Donanemab teaches the immune cells to recognise and remove a protein called amyloid, which builds up in the brains of people with Alzheimer’s disease. In clinical trials, around three-quarters of participants taking donanemab had amyloid successfully cleared from their brains by the end of the study. 

Who Is Donanemab For? 

Donanemab has been approved by the European Commission for treating adults with mild cognitive impairment (memory and thinking problems) and in the early stages of dementia due to Alzheimer’s disease.  It was approved on 25th September 2025. This decision follows other regulators such as the FDA in the United States (approved in July 2024) and in other countries such as Qatar, Japan, the United Kingdom, Kuwait, Singapore, Taiwan, Brazil and Australia.

Those who benefitted most were those who were in the earlier stages of the disease and had low levels of another toxic protein called tau in their brains. 

Is Donanemab Approved for Everyone with Dementia?

Donanemab is approved for: 

• People with early-stage Alzheimer’s disease or Mild Cognitive Impairment
• People who carry none or only one copy of the APOE4 gene variant 

Donanemab is NOT APPROVED for use in:   

• People with moderate or late-stage dementia caused by Alzheimer’s disease
• People 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 

Your doctor may carry out a variety of tests to determine if donanemab is right for you. 

How Well Does Donanemab Work? 

It is thought that donanemab slows the progression of Alzheimer’s Disease by approximately 4-7 months.   

What Does Research on Donanemab Tell Us? 

Approximately 1,736 patients with early-stage Alzheimer’s were treated using donanemab as part of a Phase 3 clinical trial (TRAILBLAZER-ALZ2). This compared people taking the drug with those given a dummy treatment (placebo). The results showed that people who started donanemab earlier in the disease experienced the greatest benefit. 

What did the trial show? 

• Slower worsening of symptoms (35%):
  The trial showed that donanemab reduced the rate at which memory and thinking skills got worse (by 35% compared with people on the dummy drug). 

• Better day-to-day functioning (40%):
  It led to a 40% reduction in the decline of daily living skills, such as managing finances, driving, taking part in hobbies and holding conversations. 

• More people with no progression at one year (47%):
  After one year, 47% of people taking donanemab showed no clinical progression, compared with 29% of people in the placebo group. 

• Lower amyloid levels: Participants were considered to have ‘completed’ treatment once a set level of amyloid plaque clearance was reached. Over half completed their course within 12 months, and 72% completed it by 18 months. 

Early results in 2025 from a further study (TRAILBLAZER-ALZ 2 LTE) following these participants up longer show that, people who took donanemab continued to experience a slowing of decline, and a slower reaccumulation rate of amyloid. 

How Is Donanemab Given? 

Donanemab is given is given to patients intravenously, which means into a vein (usually in the arm) through a drip bag. It is usually given every month. 

Is Donanemab Safe?  

The European Medicines agency scrutinised the safety data on donanemab and decided that donanemab is safe as a treatment for early-stage Alzheimer’s disease. 

However, all drugs can have some side effects and sometimes, these side effects can be serious. 

What Are the Known Side Effects/Risks of Donanemab? 

Common Side Effects include flushing, chills, fever and headache.

Serious and Controversial Side Effects: ARIA 

The most controversial side effects are amyloid-related imaging abnormalities (ARIA), which are known to occur with treatments using antibodies like donanemab. 

In the U.S., donanemab carries a prescribing warning for ARIA. Not all patients experience ARIA, but some patients may have ARIA without any symptoms.  

Features of ARIA may include: 

• Temporary brain swelling
• Small brain bleeds
• Headaches
• Confusion
• Visual disturbances

Reported Deaths

 In rare cases, ARIA can be life-threatening. There have been three deaths related to donanemab during the clinical trial and its extension phase. 

Why Did the European Commission Approve Donanemab if It Has Known Risks? 

All medicines come with potential side effects, and donanemab is no exception. When the European Commission reviews a new treatment, it carefully weighs the potential benefits against the possible risks. In this case, the evidence showed that, for the right group of people, the benefits of slowing early Alzheimer’s disease outweighed the known risks. 

The approval also includes strict eligibility criteria to ensure the treatment is offered only to people who are at the lowest risk of serious side effects. 

 Not everyone who takes donanemab will experience these side effects, and ultimately, deciding whether to start treatment is a personal decision, made in consultation with a medical team who can explain the risks, benefits, and what they mean for your individual circumstances. 

What Tests/Precautions Are Required? 

ARIA is typically monitored using MRI scans, with a baseline scan at the beginning and then regularly during treatment to check for any changes. 

People on blood thinning medication may be at higher risk of developing ARIA and should consult their doctor to determine if donanemab is appropriate for them. 

Your doctor will also carry out a variety of other tests to monitor you.  

Is Donanemab Available in Ireland? 

As of September 2025, the European Commission has recommended this drug for marketing authorisation in the EU. To our knowledge, it is not yet available in Ireland. 

How Can I Access Donanemab? 

Currently, donanemab cannot be accessed in Ireland.  

Are There Any Alternatives to Drugs like Donanemab?

There has been another recently approved drug that works in a similar way to donanemab – lecanemab, and you can read more about it on this webpage.   

There is currently no cure for dementia, but we are in an encouraging period for dementia research. Recent successful clinical trials have strengthened our understanding of how the disease develops, helping to guide future work on treatments that may be more effective and have fewer side effects. 

People living with dementia can also be prescribed medications that help ease symptoms, supporting memory, thinking, and day-to-day wellbeing. You can read more about other treatment options here.   

Additionally, there are a variety of non-pharmacological  (non-drug) therapies that help people with their daily experience of dementia.   

 What Is the Difference between Lecanemab and Donanemab? 

There are many similarities between these drugs. Both are immunotherapies that target the build up of amyloid in the brain. However, Lecanemab targets amyloid earlier in the process as it begins to form fibres whereas donanemab targets an insoluble form of amyloid once these fibres have clumped together to form a build up of plaque in the brain. 

How Can I Get Further Support? 

Hearing about new treatments like donanemab can feel overwhelming, and it’s natural to have questions. We are here to support you. You can access our dementia support services on our website. 

We offer a National Helpline, where our trained team provides personalised information, guidance and advice. While we can’t provide medical or clinical guidance, we can help you navigate available supports and signpost you to services. 

Phone support is available by calling 1-800-341-341, and webchat support is available online. 

This page will be updated as new information becomes available.