Alzheimer’s Drug Lecanemab Offers Long-Lasting Cognitive Support

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A new long-term study is offering hope for people in the early stages of Alzheimer’s disease. Researchers shared updated results from the ongoing Clarity AD clinical trial, which is looking at the long-term effects of lecanemab (brand name Leqembi), a treatment that targets the underlying causes of Alzheimer’s rather than just the symptoms.

Lecanemab is already approved by the U.S. Food and Drug Administration (FDA) for people with mild cognitive impairment (MCI) or mild dementia due to Alzheimer’s. The latest data, presented at the 2025 Alzheimer’s Association International Conference (AAIC) in Toronto, show how this treatment may help preserve memory and daily function for several years — and may even help some patients improve.

What Is Lecanemab?

Lecanemab is a type of medicine called a monoclonal antibody. It works by targeting and clearing abnormal clumps of a protein called amyloid beta in the brain. These protein clumps are believed to play a major role in Alzheimer’s disease by damaging brain cells and interrupting communication between them.

Unlike drugs that help manage symptoms, lecanemab is designed to treat the disease at its source. It was the second drug in its class to receive FDA approval, and new advancements — including a version you can inject at home — are currently under review.

What Did the Study Find?

The study tracked nearly 1,800 participants over four years. Most of these people started in the original 18-month trial and then chose to continue in a longer open-label extension (meaning they all received the treatment, not a placebo). Among the 478 people who completed the full four years of treatment, many maintained stable memory and thinking abilities — or even got better.

Specifically, 69% of patients who had detailed brain scans for tau protein (another marker of Alzheimer’s) either improved or had no decline in a standard memory and function test called the Clinical Dementia Rating-Sum of Boxes (CDR-SB). That’s a significant result, considering Alzheimer’s is typically a progressive condition.

Other cognitive tests also showed benefits:

• 56% improved on the CDR-SB overall score.
• 51% improved or held steady on memory testing (14-item Alzheimer's Disease Assessment Scale - Cognitive subscale [ADAS-Cog14]).
• 64% improved or maintained their ability to perform daily activities (Alzheimer’s Disease Cooperative Study – Activities of Daily Living Scale for use in Mild Cognitive Impairment [ADCS MCI-ADL]).

When investigators compared these patients with groups from other Alzheimer’s research studies (who didn’t receive lecanemab), the people on treatment declined much more slowly over time. In fact, after four years, the difference in memory and function scores between treated patients and untreated ones was greater than two points on the CDR-SB — meaning many people maintained more independence for longer.

Is Lecanemab Safe?

As with all medications, there are side effects to consider. One known risk of amyloid-targeting drugs is something called amyloid-related imaging abnormalities (ARIA). This can include brain swelling or small brain bleeds. In the original study, about 12.5% of patients had ARIA-related swelling and 17.3% had small brain bleeds. However, the new data show that these rates remained steady or dropped after the first year of treatment.

What’s Next for Lecanemab?

One of the most exciting developments is a new form of lecanemab that may be given as an injection at home. The FDA is currently reviewing this new autoinjector version, which could make treatment much easier and more accessible, especially for people who live far from hospitals or infusion centers. A decision is expected by August 31, 2025.

If approved, this new option would allow patients and caregivers to give the treatment themselves, in about 15 seconds, from the comfort of home.