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

Leqembi (lecanemab) long-term 36-month open-label extension data from post-hoc sub-group analysis of ApoE ε4 non-carriers and heterozygotes presented at Alzheimer’s disease congress in Switzerland

September 29, 2025 – Clinical Trials, Drug Discovery, Other, Pharmaceutical – Alzheimer's Disease, Biogen, Eisai, RFMASA 2025, clinical trials

Clarity AD open-label extension data show three years of continuous lecanemab treatment in apolipoprotein E ε4 (ApoE ε4) non-carrier and heterozygote patients continued to accrue benefit relative to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort, as measured by Clinical Dementia Rating—Sum of Boxes (CDR-SB)
The treatment also reduced the risk of progression to the next stage of Alzheimer’s disease by 28% (95% CI: 0.59, 0.87) over 36 months compared to the ADNI cohort, as measured by CDR-SB1.

29 September 2025 — Hatfield, UK and Massachusetts, US — Eisai Europe Ltd. and Biogen Inc. today presented new clinical data from a post-hoc sub-group analysis of the Clarity AD, open-label extension (OLE), demonstrating that treatment with lecanemab in adult patients with early Alzheimer’s disease (AD) (mild cognitive impairment [MCI] or mild dementia due to AD, with confirmed amyloid pathology) who are apolipoprotein E ε4 (ApoE ε4) non-carriers or heterozygotes continued to accrue benefit over 36 months, relative to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. The 36-month data was presented at Rencontres Francophones sur la Maladie d’Alzheimer et les Syndromes Apparentés (RFMASA) 2025 in Lausanne, Switzerland.

Clarity AD is a global Phase 3 placebo-controlled, double-blind, parallel-group, randomised study in 1,795 patients with early AD. Of the total number of patients randomised, 1,521 were ApoE ε4 non-carriers or heterozygotes. The primary endpoint was the change in the score of the global cognitive and functional scale, Clinical Dementia Rating—Sum of Boxes (CDR-SB). Clarity AD includes an OLE phase for eligible patients to evaluate the long-term safety profile and tolerability of lecanemab, and whether the effects of the treatment are maintained over time.

These data show that ApoE ε4 non-carrier and heterozygote patients who received continuous lecanemab treatment from the start of the study through to 36 months (n=486) continued to accrue benefit over time with continued separation through 36 months, relative to the ADNI cohort (n=139), with a 0.86 difference in CDR-SB Adjusted Mean Change from Baseline.¹

CDR-SB is a disease staging tool used in clinical trials, which can help to stage dementia due to AD. It is a global cognitive and functional scale that measures six domains of functioning, including memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care. To provide context, a change from 0.5 to 1 on the 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, recall recent events, participate in daily activities, manage household tasks, and engage in hobbies and intellectual interests.

In an analysis of time to worsening of CDR-SB scores, the OLE data at 36 months showed treatment with lecanemab (n=284) reduced the risk of progression to the next stage of disease by 28%, compared to the ADNI cohort (n=158) (hazard ratio [HR] = 0.72; 95% CI: 0.59, 0.87) in ApoE ε4 non-carrier or heterozygote patients.

In the Clarity AD core clinical trial in the European Union (EU) and United Kingdom (UK) indicated population, the most common adverse reactions in the ApoE ε4 non-carrier or heterozygote population (n=757) were infusion-related reaction (26%), amyloid-related imaging abnormalities with haemosiderin deposition (small spots of bleeding) (ARIA-H^§) (13%), fall (11%), headache (11%) and amyloid-related imaging abnormalities with cerebral oedema (build-up of fluid) (ARIA-E^‖) (9%).

“These findings increase our understanding of the potential benefits of lecanemab in eligible patients. With a progressive, chronic condition like Alzheimer’s, robust, long-term data is essential to improve knowledge of how to appropriately manage early Alzheimer’s disease patients over time,” said Robert Sands, MD, VP, Head of Medical Affairs, Eisai EMEA. “Eisai is committed to investing in research and innovation, with the aim of being a part of the solution for a better future for those impacted by this disease.”

“Together with Eisai, we are committed to advancing research for people living with early Alzheimer’s disease,” said Mihaela Vlaicu, MD, Head of Medical, Europe at Biogen. “These findings show that early and continuous treatment with lecanemab over three years can slow disease progression.”

Lecanemab is an amyloid-beta (Aβ) monoclonal antibody that preferentially binds and clears toxic Aβ protofibrils^¶ (soluble Aβ aggregates), in addition to targeting and reducing Aβ plaques (insoluble Aβ aggregates).Aβ protofibrils are a key toxic form of Aβ that accumulate in the brain and cause neuronal injury.

In the EU and UK, lecanemab is indicated for the treatment of adult patients with a clinical diagnosis of MCI and mild dementia due to AD (early AD) who are ApoE ε4 non-carriers or heterozygotes with confirmed amyloid pathology.

Eisai serves as the lead for lecanemab’s development and regulatory submissions globally, with both Eisai and Biogen co-commercialising and co-promoting the product, and Eisai having final decision-making authority. In the EU and UK (excluding the Nordic countries), Eisai and Biogen will co-promote the medicine, with Eisai distributing the product as the Marketing Authorisation (MA) Holder. In the Nordic countries, Eisai and BioArctic will co-promote the medicine, with Eisai distributing the product as the MA Holder.

About the Collaboration between Eisai and Biogen for AD

Eisai and Biogen have been collaborating on the joint development and commercialisation of AD treatments since 2014. Eisai serves as the lead of lecanemab development and regulatory submissions globally with both companies co-commercialising and co-promoting the product and Eisai having final decision-making authority.

About the Collaboration between Eisai and BioArctic for AD

Since 2005, Eisai and BioArctic have had a long-term collaboration regarding the development and commercialisation of AD treatments. Eisai obtained the global rights to study, develop, manufacture and market lecanemab for the treatment of AD pursuant to an agreement with BioArctic in December 2007. The development and commercialisation agreement on the antibody back-up was signed in May 2015.

About Eisai EMEA
At Eisai, we give our first thought to patients, their care partners and to society, to increase the benefits health care provides them – we call this human health care (hhc). We focus beyond the realm of health to the value we bring to society. Through the power of collaboration and by using insights to guide our work, we can make a meaningful contribution to people and society, and to improve outcomes and services for all. In EMEA, we are the European hub of Tokyo-based Eisai Co. Ltd., forming part of a multinational team working across a global network of R&D facilities, manufacturing sites and marketing subsidiaries. Our collective passion and dedication to patient care is the driving force behind our efforts to discover and develop innovative medicines in a variety of therapeutic areas where a high unmet medical need remains, including oncology and neurology. Our mission is clear; we strive to make a significant long-lasting contribution to society in an ethical, compliant, and sustainable way by embodying hhc in everything we do. For more information about Eisai in the EMEA region please visit www.eisai.eu.

About Biogen
Founded in 1978, Biogen is a leading biotechnology company that pioneers innovative science to deliver new medicines to transform patient’s lives and to create value for shareholders and our communities. We apply deep understanding of human biology and leverage different modalities with aspirations to advance first-in-class treatments or therapies that deliver superior outcomes. Our approach is to take bold risks, balanced with return on investment to deliver long-term growth. Biogen routinely post information that may be important to investors on its website. Visit: www.biogen.com.