Lecanemab Shows Sustained Benefit at 4 Years in Early Alzheimer Disease: AAIC 2025

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Four-year data from the open-label extension (OLE) of the Clarity AD trial show that continuous treatment with lecanemab-irmb (LEQEMBI) is associated with sustained clinical benefit in individuals with early Alzheimer disease (AD).¹

Results were presented at the Alzheimer’s Association International Conference (AAIC) 2025.

Lecanemab, a humanized monoclonal antibody targeting soluble protofibrils and insoluble amyloid beta (Aβ) aggregates, was evaluated in the global Phase 3 Clarity AD trial (n=1 795), which randomized participants with early symptomatic AD to receive lecanemab or placebo biweekly for 18 months. Of those completing the core study, 95% entered the OLE, and 478 patients continued treatment for 4 years.¹

At 18 months, the treatment group showed a mean –0.45 point difference on the Clinical Dementia Rating–Sum of Boxes (CDR-SB) versus placebo (P = .00005). Over four years, the mean CDR-SB benefit compared with the Alzheimer’s Disease Neuroimaging Initiative (ADNI) natural history cohort increased to –1.75 points. When compared with the BioFINDER cohort, the mean benefit reached –2.17 points at four years.¹

An analysis of a tau PET substudy further indicated that 56% of patients with low baseline tau levels showed improvement from baseline on CDR-SB after four years of lecanemab treatment, and 69% showed no decline or improvement. On the ADAS-Cog14, 51% of patients demonstrated either stability or improvement; on the ADCS-MCI-ADL, 58% showed improvement and 64% remained stable or improved.¹

The safety profile of lecanemab remained consistent throughout the OLE. No new safety concerns were identified, and the incidence of amyloid-related imaging abnormalities (ARIA) decreased after the first year and remained stable thereafter.¹

Lecanemab is currently approved in 46 countries and under regulatory review in 10 others. The FDA approved a supplemental Biologics License Application in January 2025 allowing for monthly intravenous maintenance dosing.² A subcutaneous formulation is also under review with a decision expected by August 31, 2025.

References:

1. Early alzheimer’s patients continue to benefit from four years of LEQEMBI® (lecanemab-irmb) therapy new clinical data presented at AAIC. News release. Eisai. July 31, 2025. Accessed August 1, 2025. https://www.eisai.com/news/2025/news202554.html
2. Halsey G. FDA approves monthly IV maintenance dosing of lecanemab for adults with early alzheimer dementia: A first in long-term disease management. Patient Care Online. January 26, 2025. https://www.patientcareonline.com/view/fda-approves-monthly-iv-maintenance-dosing-of-lecanemab-for-adults-with-early-alzheimer-dementia-a-first-in-long-term-disease-management