Eisai and Biogen today presented new data from their study on lecanemab-irmb, an anti-amyloid beta protofibril antibody for the treatment of early Alzheimer’s disease (AD), at the Alzheimer’s Association International Conference (AAIC) 2025 held in Toronto and virtually.
According to the companies, lecanemab is the only therapy that targets both amyloid plaque and protofibrils, which may affect tau accumulation downstream. The latest findings demonstrated that continuous treatment with lecanemab over four years helped patients remain in the early stages of AD longer than the natural course of the disease.
The data stem from the Clarity AD study, a global Phase 3 placebo-controlled, double-blind, parallel-group, randomised trial involving 1,795 participants diagnosed with early Alzheimer’s disease. Of these, 898 received lecanemab 10 mg/kg bi-weekly via intravenous infusion, and 897 were assigned to the placebo group. After 18 months, 95 per cent of patients who completed the core study opted to continue in the open-label extension (OLE). A total of 478 patients have continued treatment for four years.
At the end of the core study period, the mean difference between the lecanemab and placebo groups on the CDR-SB (Clinical Dementia Rating–Sum of Boxes) cognitive and functional scale was -0.45 (P=0.00005). The CDR-SB is used to evaluate memory, community involvement, and ability to carry out home or leisure activities. A shift from 0.5 to 1.0 on CDR score domains typically indicates a transition from mild impairment to loss of independence, which may affect an individual’s ability to be left alone safely or manage routine tasks.
Over the three-year treatment period, which includes both the core and OLE phases, lecanemab showed a 1.01-point reduction in CDR-SB decline compared to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. This reduction increased to 1.75 points after four years. When compared against the BioFINDER cohort, the three-year and four-year reductions were 1.40 and 2.17 points, respectively.