What is lecanemab?

Lecanemab, the new treatment for Alzheimer’s disease, has been a big news story recently and in this article, we take a closer look at what it is, if it works and what the big deal is.

Lecanemab is a disease modifying treatment for people living with the early stages of Alzheimer’s disease or mild cognitive impairment. The drug includes antibodies which are designed to attach to and remove amyloid plaques. The accumulation of these amyloid plaques in the brain is linked to the development of Alzheimer's disease.  

What are the results so far?

Lecanemab was trialled on 1,795 people with early-stage Alzheimer’s disease. The treatment group received a dose of lecanemab every two weeks. The other group within the trial received a placebo, which is an inactive substance that looks like the drug being tested. Comparing results from the two groups suggests whether changes in the treatment group result from the treatment or occur by change.

After 18 months of follow-up, participants receiving lecanemab treatment demonstrated a slower rate of cognitive decline (by 27 per cent) compared to those who received the placebo. The lecanemab group also showed a greater reduction in amyloid levels in the brain from baseline at 18 months compared with placebo.

In general, the results show the lecanemab trial was successful, however participants who received lecanemab were more likely to experience side effects than those given the placebo and 7 per cent of people given the drug had to stop because of the side effects.

Side effects recorded included small bleeds and swelling in the brain. Those participants who experienced side effects were monitored with regular brain scans and the dose modified. There have also been three deaths linked to lecanemab treatment. 

Why is it a big deal?

Associate Professor Michael Woodward AM is a Dementia Australia Honorary Medical Advisor and said the results of lecanemab are a breakthrough after a dry spell in the development of treatment for Alzheimer’s disease.

“It’s a major breakthrough but not a miracle cure – in fact, it doesn’t cure the disease it just slows down the rate of decline,” A/Prof Woodward explained.

“This drug should only really be used in the context that it was used in the trial, which is only for people with mild Alzheimer’s disease and Alzheimer’s disease that has been proven by some sort of biomarker such as a blood test.

“It’ll possibly only help about 10-20 per cent of people with Alzheimer’s disease, so before everyone rushes off to their GP, it’s not going to be something they can just write a script for.”

Professor Amy Brodtmann, also a Dementia Australia Honorary Medical Advisor, said that although lecanemab is a promising development there is still much work to be done.

““I think is the first step to dementia disease modifying treatments. I see it as similar to how in the early stages of the development of a treatment for AIDS there were many promising drugs developed, but it took many years for researchers to refine the cocktail of drugs into an effective treatment. I think we are at a similar stage with the search for an effective dementia treatment,” Professor Brodtmann said.

“This is exciting. It’s the first chink in the armour of dementia and we can continue to build to hopefully develop an effective treatment in the future.”

Is it available to the public?

The Food and Drug Administration (FDA) in the United States of America approved lacanemab in January 2023. Marketed as LEQEMBI, the drug can be used in the US by those with mild cognitive impairment or early-stage Alzheimer's disease. An application for lecanemab is currently under consideration by the Therapeutic Goods Administration (TGA) in Australia. Lecanemab is also on the July 2024 Pharmaceutical Benefits Committee (PBAC) Agenda for consideration. It is also likely lecanemab will only ever be a part of the package of care and management of those with Alzheimer's disease.

How is lecanemab different to the other dementia treatment, aducanumab?

Aducanumab was the first drug in this category approved by the FDA in June 2021.

Both lecanemab and aducanumab remove amyloid from the brain but each drug binds to the amyloid in a slightly different way. Aducanumab also requires incremental dosage for the first few months to avoid side effects like brain swelling and bleeding whereas it is claimed lecanemab can be started immediately at the highest dose.

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