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What is lecanemab?

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.

This year we are expecting to hear if two new drugs, lecanemab and donanemab, will be approved for use in the UK. These can slow down the decline in memory and thinking skills of people living with early Alzheimer’s disease. 

Does lecanemab work?

Lecanemab 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. 

On the 29th November 2022, 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.

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 that 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.

Is lecanemab safe?

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. There have also been three deaths related taking lecaneamb 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.

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. 

How does lecanemab work?

Lecanemab 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 117 other drugs currently being tested in clinical trials.

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.

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 mean lecanemab will become available in the UK.
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. A decision on whether or not lecanemab will be approved for use in the UK is expected in the first half of 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. A decision by NICE on lecanemab is expected in July 2024.

How is lecanemab different from donanemab?  

Lecanemab and donanemab are both immunotherapies. Although both drugs target amyloid protein, they target it at different stages in how it builds up in the brain. 

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

This may be partly why we see a difference in how effective both drugs are at slowing down the disease. Who would be eligible to take lecanemab?

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

This means that to be eligible for lecanemab treatment a person would need to be in the early stages of Alzheimer’s disease and have amyloid protein buildup present in their brain. This can be shown using amyloid PET scans or by testing spinal fluid.
People with other types of dementia, or in the later stages of Alzheimer’s disease, are unlikely to benefit from this drug.

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.

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: 19 January 2024.

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