- Data Showed LEQEMBI Slowed Clinical Decline by 1.75 Points on CDR-SB at Four Years Compared to the Natural History of Alzheimer’s Disease

- 56% of Patients with Low Tau Continued to Demonstrate Improved Cognitive and Daily Living Function at Four Years

TOKYO and CAMBRIDGE, Mass., July 31, 2025 - (JCN Newswire) - Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”)and Biogen Inc. (Nasdaq: BIIB, Headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher,“Biogen”) announced today that the latest findings demonstrating the benefits of continuous treatment with lecanemab-irmb (U.S. brand name: LEQEMBI®), an anti-amyloid beta (AB) protofibril* antibody for the treatment of early Alzheimer’s disease (AD), were presented at the Alzheimer's Association International Conference(AAIC) 2025, held in Toronto, Canada, and virtually. Only lecanemab fights AD in two ways – targeting both amyloid plaque and protofibrils*, which can impact tau downstream.

Four Years of Lecanemab Therapy Helped Patients Slow the Progression of AD and Remain in the Early Stages of AD Longer Compared to AD’s Natural Course

Clarity AD is a global Phase 3 placebo-controlled, double-blind, parallel-group, randomized study to evaluate lecanemab 10 mg/kg bi-weekly IV treatment of early Alzheimer's disease, which involved 1,795 patients(treatment group: 898, placebo group: 897). 95% of patients who completed the core study (18 months) chose to continue in the open-label extension study (OLE), with 478 patients still receiving treatment for four years. In the Clarity AD core study, the mean change from baseline between the lecanemab treated group and the placebo group after 18 months was -0.45 (P=0.00005) on the primary endpoint of CDR-SB global cognitive and functional scale.

To provide context, a change from 0.5 to 1 on the Clinical Dementia Rating (CDR) score domains of Memory, Community Affairs and Home/Hobbies reflects a shift from mild impairment to loss of independence. This can affect a person’s ability to be left alone safely, recall recent events, participate in daily activities, manage household tasks, and engage in hobbies and intellectual interests.1,2

Over three years of treatment, including both the core study and the OLE, data showed lecanemab demonstrate da reduction in cognitive decline—measured by CDR-SB—of 1.01 points compared to the expected decline observed in the Alzheimer’s Disease Neuroimaging Initiative (ADNI)** cohort. This benefit grew more pronounced after four years, with a reduction of 1.75 points. Similarly, when bench marked against the expected decline in the BioFINDER*** cohort, lecanemab showed a reduction of 1.40 points at three years and an even greater reduction of 2.17 points at the four years mark. 

For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202554pdf.pdf

MEDIA CONTACTS

Eisai Co., Ltd.
Public Relations Department
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Eisai Europe, Ltd.
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Emea-comms@eisai.net

Eisai Inc. (U.S.)
Libby Holman
+1-201-753-1945
Libby_Holman@Eisai.com

Biogen Inc.
Madeleine Shin
+1-781-464-3260
public.affairs@biogen.com

INVESTOR CONTACTS
Eisai Co., Ltd.
Investor Relations Department
TEL: +81 (0) 3-3817-5122

Biogen Inc.
Tim Power
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IR@biogen.com

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