Eisai Reports Four-Year Sustained Benefits of Leqembi in Early Alzheimer’s Disease
Eisai has unveiled compelling new clinical data demonstrating that patients with early Alzheimer’s disease can experience sustained benefits from long-term treatment with its anti-amyloid therapy, Leqembi (lecanemab).
The findings, presented at the Alzheimer’s Association International Conference (AAIC) 2025 in Toronto and online, underscore the potential of the drug to meaningfully slow disease progression over a four-year period.
Long-Term Efficacy Confirmed
Results from the Clarity AD open-label extension study showed that lecanemab slowed clinical decline by 1.75 points on the Clinical Dementia Rating–Sum of Boxes (CDR-SB) scale compared to expected decline in the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort.
This benefit was observed across all apolipoprotein E ε4 (ApoE ε4) genotypes, reinforcing the therapy’s broad applicability within its indicated patient group.
Importantly, the effect strengthened over time. At three years, lecanemab reduced decline by 1.01 points versus ADNI, rising to 1.75 points at four years. When compared against the BioFINDER cohort, the reduction was even greater – 1.40 points at three years and 2.17 points at four years.
Targeting Alzheimer’s at the Source
Lecanemab is an amyloid-beta monoclonal antibody that targets and clears toxic protofibrils, reducing amyloid plaques – protein aggregates strongly linked to neuronal injury and cognitive decline in Alzheimer’s disease.
In the EU and United Kingdom, it is indicated for adults with mild cognitive impairment or mild dementia due to Alzheimer’s disease, specifically those who are ApoE ε4 non-carriers or heterozygotes with confirmed amyloid pathology.
Study Design and Patient Experience
A total of 478 patients who completed the 18-month Clarity AD core study continued treatment for four years in the extension phase.
No new safety signals emerged during this period. Rates of amyloid-related imaging abnormalities (ARIA) decreased after the first year and remained stable throughout the remainder of the study.
The most common adverse events reported in the phase 3 trial included infusion reactions, ARIA-H (haemosiderin deposits), ARIA-E (oedema), headache, and falls. These events were consistent with previous findings and considered manageable within the existing treatment framework.
A Potential Paradigm Shift in Alzheimer’s Care
The sustained benefits observed over four years mark an important milestone for both patients and clinicians.
By slowing cognitive decline in a measurable and clinically relevant way, lecanemab could help preserve quality of life for people in the earliest stages of Alzheimer’s disease – when intervention has the greatest potential impact.
In conclusion
Eisai’s latest data adds weight to the growing body of evidence supporting long-term amyloid-targeting therapies as a viable approach in Alzheimer’s disease management.
With benefits that not only persist but increase over time, lecanemab offers renewed hope that the trajectory of this devastating disease can be altered for those diagnosed early enough to act.
News Credits: Eisai data shows sustained benefit of lecanemab in early Alzheimer’s disease
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