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

Eisai presents 4-year Leqembi (lecanemab) open-label extension data from post-hoc sub-group analysis at German neurology congress

November 12, 2025 – Clinical Trials, Other, Pharmaceutical – Alzheimer's Disease, Alzheimer's Disease and Dementia, Biogen, Eisai, clinical trials

Clarity AD open-label extension data show that after four years of continuous lecanemab treatment in apolipoprotein E ε4 (ApoE ε4*) non-carriers and heterozygotes, 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 32% (95% CI: 0.57, 0.82) over 48 months compared to the ADNI cohort as measured by CDR-SB.

12 November 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 slow disease progression as measured by CDR-SB compared to matched controls from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). The 48-month data was presented at the 98th Congress of the German Society of Neurology (DGN), 2025 in Berlin, Germany.

Clarity AD was a global Phase 3 placebo-controlled, double-blind, parallel-group, randomised study. 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, 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.

Participants who received treatment from the start through to 48 months (n=409) as part of the OLE study continued to accrue benefit over time with continued separation through 48 months, relative to the ADNI cohort (n=79), with a 1.53 difference in CDR-SB Adjusted Mean Change from Baseline. Post-hoc slope analysis of CDR-SB results at 48 months presented at the congress showed that the lecanemab cohort had delayed disease progression compared to those in the ADNI cohort (n=79) by 9.8 months.

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, 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 48 months showed treatment with the medicine reduced the risk of progression to next stage of the disease by 32% vs ADNI, hazard ratio [HR] = 95% CI: 0.57, 0.82) in ApoE ε4 non-carrier or heterozygote patients.

In the Clarity AD core clinical trial in the EU and 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 brain bleeding) (ARIA-H¶) (13%), fall (11%), headache (11%) and amyloid-related imaging abnormalities with cerebral oedema (build-up of fluid in the brain) (ARIA-E#) (9%).

No new safety findings have been observed with continuous treatment with lecanemab over 48 months in the ApoE ε4 non-carrier and heterozygote population. The summary of adverse events by 12-month intervals in the UK/EU population is as follows:

Figure 1	<12 months (n=1,366)		12-24 months (n=1,095)		24-36 months (n=850)		36-48 months (n=549)
Adverse Event (AE)	1115	81.6%	794	72.5%	582	68.5%	320	58.3%
Serious Adverse Event (SAE)	150	11.0%	99	9.0%	64	7.5%	36	6.6%
Death (Includes all post-treatment events)	7	0.5%	8	0.7%	4	0.5%	1	0.2%
AE’s Leading to Study Drug Withdrawal	67	4.9%	36	3.3%	14	1.6%	4	0.7%
ARIA-E	132	9.7%	27	2.5%	9	1.1%	6	1.1%
ARIA-H	154	11.3%	125	11.4%	66	7.8%	47	8.6%
Isolated ARIA-H	67	4.9%	79	7.2%	52	6.1%	35	6.4%
Headache	102	7.5%	58	5.3%	26	3.1%	19	3.5%
Infusion-Related Reaction	309	22.6%	50	4.6%	24	2.8%	11	2.0%

Figure 1: As of 31 March 2025

“The presentation of these findings adds to the growing body of evidence demonstrating the potential benefits of lecanemab for eligible patients. As Alzheimer’s disease is a progressive and chronic condition, it is crucial to continue generating and analysing long-term data as it deepens our understanding of continuous treatment 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.”

“These data show the sustained clinical benefits of lecanemab over four years of treatment, demonstrating the potential to help people living with mild cognitive impairment and mild dementia due to Alzheimer’s disease”, said Mihaela Vlaicu, Head of Medical, Europe at Biogen. “The findings offer valuable insights to guide evidence-based discussions on the long-term management of early Alzheimer’s disease, aiming to slow disease progression.”

Lecanemab is an amyloid-beta (Aβ) monoclonal antibody that preferentially binds and clears toxic 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 the UK, lecanemab is indicated for the treatment of adult patients with a clinical diagnosis of mild cognitive impairment (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 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. Visit: www.biogen.com.