Working in the lab

Lecanemab: A new drug for early-stage Alzheimer’s disease

Lecanemab has made headlines as a promising new drug for people living with early-stage Alzheimer’s disease. Here is what we know so far about this breakthrough Alzheimer's drug.

What is the new drug for Alzheimer's disease?

Lecanemab (now marketed as Leqembi) targets a protein called amyloid. The importance of this protein in the development of Alzheimer’s disease was discovered by our 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 117 other drugs currently being tested in clinical trials.

How does lecanemab work?

Lecanemab is a disease modifying immunotherapy drug. It works with the body’s immune system 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.

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.

Lecanemab is given to patients intravenously, which means into a vein through a drip bag. It targets amyloid protein in the brain and then ‘triggers’ the brain’s immune system to clear it out.

What is the latest news on lecanemab? 


Lecanemab was approved by the US Food and Drug Administration (FDA) as a treatment for early Alzheimer's disease in January 2023. This means that it can now be given to patients with early Alzheimer's disease in the USA.

The drug will be marketed under the name Leqembi and has been approved using the FDA's Accelerated Approval Pathway. This allows approval decisions to happen faster and is for treatments that tackle serious conditions where there is a unmet medical need. 

Since the announcement of the decision, the drug company have also submitted an application to the European Medicines Agency for approval in the EU.

Clincial Trials

Late last year, Eisai (the company that makes lecanemab) released the full results of lecanemab’s phase 3 clinical trial called Clarity-AD at the Clinical Trials on Alzheimer’s Disease (CTAD) conference in San Francisco on the 29th November 2022.

Clarity-AD is 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.

Researchers estimate over 18 months the drug may slow the progression of the condition by about 7 months. The research team also found that the drug slowed the decline in 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.

Clinical trials for lecanemab will continue so that researchers can understand the effects of taking this drug over a longer period of time.

Who could benefit from lecanemab treatment?

Lecanemab is a treatment for people with early-stage Alzheimer’s disease who have amyloid in their brain.

This means people with other types of dementia, or in the later stages of Alzheimer’s disease, are unlikely to benefit from this drug. 

Does lecanemab have any side effects?

Like all drugs, lecanemab was found to have some side effects.

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  – known as Amyloid Related Imaging Abnormalities or ARIA.

The majority of people who experienced ARIA had no symptoms and these changes in the brain were only detected using MRI brain scanning.

Safety is closely monitored and is of paramount importance during any clinical trial.

The drug regulatory bodies will scrutinise the lecanemab safety data and use it to make a decision about whether lecanemab is both safe and effective as a treatment for people living with early-stage Alzheimer’s disease. 

When will lecanemab be available in the UK?

At this stage, lecanemab remains an experimental medicine that is not available to patients in the UK outside of clinical trials. Before lecanemab can become available for use, drug regulatory bodies will make a decision as to whether or not lecanemab is both effective and safe as a treatment for early Alzheimer’s disease.

The approval of lecanemab by the FDA in January 2023 was a big step but does not affect whether lecanemab will be available in the UK.

The drug company submitted an application to the European Medicines Agency (EMA) for approval of lecanemab in the EU. We expect the EMA to make a recommendation to the European Commission on whether lecanemab should be approved for use in Europe in the first half of 2024.

For lecanemab to be available in the UK, it would have to be approved by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK. Following Brexit, the Government has stated that the MHRA will follow decisions made by the European Commission until January 2024.

We do not yet know whether lecanemab will be approved for use in the UK.

Approval by the MHRA doesn't mean that lecanemab will be available on the NHS. For that to happen, it would also need to be approved by the National Institute for Health and Care Excellence (NICE). For this decision, NICE will consider the benefits and risks as well as take into account how cost-effective the treatment is.

How can you get involved in dementia research?

Alzheimer’s Society is a partner in a service called Join Dementia Research (JDR). The service allows anyone over the age of 18 to register their interest in participating in dementia research; however, researchers are particularly keen to hear from those with a diagnosis of dementia/ or MCI and those that care/support them to register.

Alzheimer’s Society has a JDR helpdesk which is a great way for people to find out more about the benefits of being involved in dementia research, how the service works, and the types of exciting studies that are currently looking for volunteers including trials looking into new treatments, therapies and improving care and support.

Signing up for the service is easy and our helpdesk can register people over the phone as well as provide ongoing support and advice to help people engage with the service.
If you would like to hear more about this service then please contact our Join Dementia Research helpdesk by calling 0333 150 3456 and asking for the Join Dementia Research helpdesk or emailing us directly at: [email protected] 

We will update this page as new information becomes available. Last updated: 14 July 2023.

Support dementia research

Alzheimer’s Society funds research into the cause, cure, care and prevention of dementia. If you’re able to, please donate to support our work.

Make a donation