Eisai has presented new clinical data showing that patients with early Alzheimer’s disease continue to benefit from four years of treatment with Leqembi (lecanemab). Findings were shared at the Alzheimer’s Association International Conference 2025, held in Toronto and virtually.
Results from the Clarity AD open label extension show that lecanemab slowed clinical decline by 1.75 points on the Clinical Dementia Rating-Sum of Boxes scale, compared to expected decline in the ADNI cohort. This effect was observed across all apolipoprotein E ε4 genotypes.
The benefit increased over time. At three years, lecanemab reduced decline by 1.01 points vs ADNI, rising to 1.75 points at four years. Against the BioFINDER cohort, the reduction was 1.40 points at three years and 2.17 points at four years.
Lecanemab is an amyloid-beta monoclonal antibody that targets and clears toxic protofibrils and reduces amyloid plaques. These aggregates are linked to neuronal injury in Alzheimer’s disease.
In the EU and UK, lecanemab is indicated for adults with mild cognitive impairment or mild dementia due to Alzheimer’s disease, who are ApoE ε4 non-carriers or heterozygotes with confirmed amyloid pathology.
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 findings were reported during this period.
Rates of amyloid-related imaging abnormalities decreased after the first year and remained stable throughout treatment. The most common adverse events in the phase 3 trial included infusion reactions, ARIA-H, ARIA-E, headache and fall.
