Core Insights - Eisai Co., Ltd. and Biogen Inc. presented a two-year real-world study of lecanemab at the Alzheimer's Association International Conference 2025, highlighting its dual action against amyloid plaque and protofibrils in Alzheimer's disease [1][2] Patient Baseline and Treatment Situation - The interim study involved 178 early Alzheimer's disease patients from nine U.S. medical centers, with 57.6% diagnosed with mild cognitive impairment and 42.4% with mild Alzheimer's [3] - The average age of patients was 74.2 years, with a gender ratio of 44.6% men to 55.4% women [3] Treatment Duration and Continuation - The mean duration of lecanemab treatment was 375.4 days, with an average of 24.8 treatments per patient [4] - At the time of reporting, 87.4% of patients were still receiving treatment, with discontinuations primarily due to adverse events or personal reasons [4] Clinical Outcomes - 83.6% of patients remained stable or improved, with 86.7% of those receiving 40 or more doses over 18 months showing similar outcomes [5] - Adverse events were reported in 12.9% of patients, with the majority being asymptomatic [6][8] APOE4 Status Impact - Among 166 patients with known APOE4 status, 18.1% were homozygotes, 49.4% were heterozygotes, and 32.5% were non-carriers [7] - The incidence of ARIA was highest in homozygous carriers at 20.0%, compared to 9.8% in heterozygous and 14.8% in non-carriers [8] Blood-Based Biomarkers Utilization - 27.5% of patients were diagnosed using blood-based biomarkers, with a significant increase in testing volume observed [10][11] Treatment Satisfaction - Physician satisfaction with lecanemab's efficacy and safety averaged 8.7 out of 10, with patient satisfaction rated at 8.8 [12][13] Regulatory and Development Status - Lecanemab has been approved in 46 countries and is under review in 10, with recent approvals for maintenance dosing in the U.S. [19] - Ongoing clinical studies include the Phase 3 AHEAD 3-45 study for preclinical Alzheimer's and the Tau NexGen study for Dominantly Inherited Alzheimer's [20] Collaboration Background - Eisai and Biogen have collaborated on Alzheimer's treatments since 2014, with Eisai leading development and regulatory submissions [21] - Eisai has a long-term partnership with BioArctic for the development of lecanemab, securing global rights in 2007 [22]