• In the European Union (EU), lecanemab is indicated for the treatment of adult patients with a clinical diagnosis of mild cognitive impairment and mild dementia due to Alzheimer’s disease (early AD) who are apolipoprotein E ε4 (ApoE ε4^*) non-carriers or heterozygotes with confirmed amyloid pathology
• Lecanemab is the first therapy that targets an underlying cause of the disease to be authorized in the EU for eligible people with early AD

TOKYO and CAMBRIDGE, Mass., April 15, 2025 (GLOBE NEWSWIRE) -- Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced today that the European Commission (EC) has granted the amyloid-beta (Aβ) monoclonal antibody Leqembi^® (lecanemab) Marketing Authorization (MA) in the European Union (EU). This makes the medicine the first therapy that targets an underlying cause of Alzheimer’s disease (AD) to be granted a MA in the EU.^1,2

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 apolipoprotein E ε4 (ApoE ε4^*) non-carriers or heterozygotes with confirmed amyloid pathology.¹ The lecanemab MA applies to all 27 EU Member States as well as Iceland, Liechtenstein, and Norway.³

Lecanemab is the only approved Aβ monoclonal antibody that preferentially binds and clears toxic protofibrils^** (soluble Aβ aggregates), in addition to targeting and reducing Aβ plaques (insoluble Aβ aggregates).^1,2,4-7 Protofibrils are a key toxic form of Aβ that accumulate in the brain and cause neuronal injury.^4-10

MCI due to AD and AD dementia currently affects an estimated 15.2 million and 6.9 million people in Europe, respectively.¹¹ AD progresses in stages that increase in severity over time, and each stage of the disease presents different challenges for those living with AD and their care partners. There is a significant unmet need for new treatment options that slow down the progression of AD from its early stage and reduce the overall burden on people affected by AD and society.

“Today’s decision makes lecanemab the first treatment option in the EU that can slow the progression of early Alzheimer's disease. We are proud that our about 40-year heritage in dementia has led to this important milestone, as we aim to be part of the solution for a better future for those impacted by this disease globally,” said Haruo Naito, Chief Executive Officer at Eisai. “Eisai is working collaboratively with national reimbursement authorities and healthcare providers to support access for those eligible for lecanemab as soon as possible, aiming to make an impact not only on patients but also on their caregiving families and society in the EU.”

“The approval of lecanemab by the European Commission marks the thirteenth approval of this important medicine, which has already benefitted thousands of patients in the United States, Japan and other regions of the world,” said Christopher A. Viehbacher, President and Chief Executive Officer at Biogen. “Lecanemab is the first treatment which showed that the reduction of the Aβ plaques in the brain is associated with the slowing of cognitive decline in patients at the early stage of the disease. This is a landmark advancement in a field where there has been no or little innovation in the past 20 years.”

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

^* Apolipoprotein E is a protein involved in the metabolism of lipid in humans. It is implicated in AD. People with only one (heterozygous) or no copy (non-carriers) of the ApoE ε4 gene are less likely to experience ARIA than people with two ApoE ε4 copies (homozygous).² ARIA is a recognized important side effect with lecanemab that involves swelling and potential bleeding in the brain.^1,2
** Protofibrils are believed to contribute to the brain injury that occurs with AD and are considered to be the most toxic form of Aβ, having a primary role in the cognitive decline of this progressive, debilitating condition.⁷ Protofibrils cause injury to neurons in the brain which, in turn, can negatively impact cognitive function via multiple mechanisms,⁷ not only increasing the development of insoluble Aβ plaques but also increasing direct damage to brain cell membranes and the connections that transmit signals between nerve cells or nerve cells and other cells.⁸ It is believed the reduction of protofibrils may slow the progression of AD by reducing damage to neurons in the brain and cognitive dysfunction.⁸

∇: This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. If you have any side effects, talk to your healthcare professional. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via your national reporting system. By reporting side effects, you can help provide more information on the safety of this medicine.

Notes to Editors

1. About lecanemab (generic name, brand name: Leqembi^®)
   
   Lecanemab is the result of a strategic research alliance between Eisai and BioArctic. It is a humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril) and insoluble forms of amyloid-beta (Aβ).^1,2
   
   The EC’s authorization was primarily based on Phase 3 data from Eisai’s global Clarity AD clinical trial, in which it met its primary endpoint and all key secondary endpoints with statistically significant results.^1,2 Clarity AD was a Phase 3 global, placebo-controlled, double-blind, parallel-group, randomized study in 1,795 patients with early AD (MCI or mild dementia due to AD, with confirmed presence of amyloid pathology). Of the total number of patients randomized, 1,521 were in the EU indicated population (ApoE ε4 non-carriers or heterozygotes).² The treatment group was administered lecanemab 10 mg/kg bi-weekly, with participants allocated in a 1:1 ratio to receive either placebo or lecanemab for 18 months.²
   
   The primary endpoint was the global cognitive and functional scale, CDR-SB (n=764).² In the Clarity AD clinical trial, treatment with lecanemab (n=757), in the EU indicated population (ApoE ε4 non-carriers or heterozygotes, measured by controlled-based multiple imputation^†), reduced clinical decline on CDR-SB by 31% at 18 months compared to placebo.¹ The mean CDR-SB score at baseline was approximately 3.2 in both groups.¹ The adjusted least-squares mean change from baseline at 18 months was 1.217 with lecanemab and 1.752 with placebo (difference, −0.535; 95% confidence interval [CI], −0.778 to −0.293).¹ CDR-SB 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.¹²
   
   In addition, the secondary endpoint from the AD Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment (ADCS MCI-ADL), which measures information provided by people caring for patients with AD, noted 33% less decline compared to placebo at 18 months.¹ The adjusted mean change from baseline at 18 months in the ADCS MCI-ADL score was −3.873 in the lecanemab group and −5.809 in the placebo group (difference, 1.936; 95% CI, 1.029 to 2.844).¹ The ADCS MCI-ADL assesses the ability of patients to function independently, including being able to dress, feed themselves and participate in community activities. ¹³
   
   In the EU indicated population (ApoE ε4 non-carriers or heterozygotes) (n=757), the most common adverse reactions were infusion-related reaction (26%), ARIA-H (13%), headache (11%) and ARIA-E (9%).¹
   
   Lecanemab has been approved in the U.S.,¹⁴ Japan,¹⁵ China,¹⁶ South Korea,¹⁷ Hong Kong,¹⁸ Israel,¹⁹ the United Arab Emirates,²⁰ the United Kingdom²¹, Mexico,²² Macau, Oman, Taiwan and the EU,¹ and is under regulatory review in 14 countries and regions. In January 2025, the supplemental Biologics License Application (sBLA) for intravenous (IV) maintenance dosing of the treatment was approved in the U.S. After an 18 months initiation phase with once every two weeks of dosing, a transition to the maintenance dosing regimen of 10 mg/kg once every four weeks or continuing 10 mg/kg once every two weeks may be considered. Additionally, the U.S. Food and Drug Administration (FDA) accepted Eisai’s Biologics License Application (BLA) for the LEQEMBI subcutaneous autoinjector for weekly maintenance dosing in January 2025 and set a PDUFA action date for August 31, 2025.
   
   Since July 2020 the Phase 3 clinical study (AHEAD 3-45) for individuals with preclinical AD, meaning they are clinically normal and have intermediate or elevated levels of amyloid in their brains, is ongoing. AHEAD 3-45 is conducted as a public-private partnership between the Alzheimer's Clinical Trial Consortium that provides the infrastructure for academic clinical trials in AD and related dementias in the U.S, funded by the National Institute on Aging, part of the National Institutes of Health, Eisai and Biogen. Since January 2022, the Tau NexGen clinical study for Dominantly Inherited AD (DIAD), that is conducted by Dominantly Inherited Alzheimer Network Trials Unit (DIAN-TU), led by Washington University School of Medicine in St. Louis, is ongoing and includes lecanemab as the backbone anti-amyloid therapy.
   
   ^†As requested by the regulatory authority, efficacy analyses were conducted for ApoE ε4 non-carriers or heterozygotes participants using control-based multiple imputation method, in which all missing values were imputed with copy-increments (change between visits) using the actual value in placebo group.²³ This methodology differs from that used in the Clarity AD primary analysis which used mixed-model repeat measures (MMRM) with missing at random assumption.²
   
   
2. About the Collaboration between Eisai and Biogen for AD
   
   Eisai and Biogen have been collaborating on the joint development and commercialization of AD treatments since 2014. Eisai serves as the lead of lecanemab development and regulatory submissions globally with both companies co-commercializing and co-promoting the product and Eisai having final decision-making authority.
   
   
3. About the Collaboration between Eisai and BioArctic for AD
   
   Since 2005, Eisai and BioArctic have had a long-term collaboration regarding the development and commercialization 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 commercialization agreement on the antibody lecanemab back-up was signed in May 2015.
   
   
4. About Eisai Co., Ltd.
   
   Eisai's Corporate Concept is "to give first thought to patients and people in the daily living domain, and to increase the benefits that health care provides." Under this Concept (also known as human health care (hhc) Concept), we aim to effectively achieve social good in the form of relieving anxiety over health and reducing health disparities. With a global network of R&D facilities, manufacturing sites and marketing subsidiaries, we strive to create and deliver innovative products to target diseases with high unmet medical needs, with a particular focus in our strategic areas of Neurology and Oncology.
   
   In addition, we demonstrate our commitment to the elimination of neglected tropical diseases (NTDs), which is a target (3.3) of the United Nations Sustainable Development Goals (SDGs), by working on various activities together with global partners.
   
   For more information about Eisai, please visit www.eisai.com (for global headquarters: Eisai Co., Ltd.), and connect with us on X, LinkedIn and Facebook. The website and social media channels are intended for audiences outside of the UK and Europe. For audiences based in the UK and Europe, please visit www.eisai.eu and Eisai EMEA LinkedIn.
   
   
5. 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 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.
   
   The company routinely posts information that may be important to investors on its website at www.biogen.com. Follow Biogen on social media – Facebook, LinkedIn, X, YouTube.

Biogen Safe Harbor

This news release contains forward-looking statements, including about the potential clinical effects of lecanemab; the potential benefits, safety and efficacy of lecanemab; potential regulatory discussions, submissions and approvals and the timing thereof; the treatment of Alzheimer's disease; the anticipated benefits and potential of Biogen's collaboration arrangements with Eisai; the potential of Biogen's commercial business and pipeline programs, including lecanemab; and risks and uncertainties associated with drug development and commercialization. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “forecast,” “goal,” “guidance,” “hope,” “intend,” “may,” “objective,” “plan,” “possible,” “potential,” “predict,” “project,” “prospect,” “should,” “target,” “will,” “would,” and other words and terms of similar meaning. Drug development and commercialization involve a high degree of risk, and only a small number of research and development programs result in commercialization of a product. Results in early-stage clinical trials may not be indicative of full results or results from later stage or larger scale clinical trials and do not ensure regulatory approval. You should not place undue reliance on these statements. Given their forward-looking nature, these statements involve substantial risks and uncertainties that may be based on inaccurate assumptions and could cause actual results to differ materially from those reflected in such statements. These forward-looking statements are based on management's current beliefs and assumptions and on information currently available to management. Given their nature, we cannot assure that any outcome expressed in these forward-looking statements will be realized in whole or in part. We caution that these statements are subject to risks and uncertainties, many of which are outside of our control and could cause future events or results to be materially different from those stated or implied in this document, including, among others, uncertainty of long-term success in developing, licensing, or acquiring other product candidates or additional indications for existing products; expectations, plans and prospects relating to product approvals, approvals of additional indications for our existing products, sales, pricing, growth, reimbursement and launch of our marketed and pipeline products; our ability to effectively implement our corporate strategy; the successful execution of our strategic and growth initiatives, including acquisitions; the risk that positive results in a clinical trial may not be replicated in subsequent or confirmatory trials or success in early stage clinical trials may not be predictive of results in later stage or large scale clinical trials or trials in other potential indications; risks associated with clinical trials, including our ability to adequately manage clinical activities, unexpected concerns that may arise from additional data or analysis obtained during clinical trials, regulatory authorities may require additional information or further studies, or may fail to approve or may delay approval of our drug candidates; the occurrence of adverse safety events, restrictions on use with our products, or product liability claims; and any other risks and uncertainties that are described in other reports we have filed with the U.S. Securities and Exchange Commission.

These statements speak only as of the date of this press release and are based on information and estimates available to us at this time. Should known or unknown risks or uncertainties materialize or should underlying assumptions prove inaccurate, actual results could vary materially from past results and those anticipated, estimated or projected. Investors are cautioned not to put undue reliance on forward-looking statements. A further list and description of risks, uncertainties and other matters can be found in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024 and in our subsequent reports on Form 10-Q and Form 10-K, in each case including in the sections thereof captioned “Note Regarding Forward-Looking Statements” and “Item 1A. Risk Factors,” and in our subsequent reports on Form 8-K. Except as required by law, we do not undertake any obligation to publicly update any forward-looking statements whether as a result of any new information, future events, changed circumstances or otherwise.

References

1. European Medicines Agency Summary of Product Characteristics （SmPC）
2. van Dyck, C.H., et al. Lecanemab in Early Alzheimer’s Disease. New England Journal of Medicine. 2023;388:9-21. https://www.nejm.org/doi/full/10.1056/NEJMoa2212948.
3. European Medicines Agency. Authorisation of medicines. Available at: https://www.ema.europa.eu/en/about-us/what-we-do/authorisation-medicines. Last accessed: April 2025.
4. Johannesson, M., et al. Lecanemab demonstrates highly selective binding to Aβ protofibrils isolated from Alzheimer's disease brains. Molecular and Cellular Neuroscience. 2024;130:103949. https://linkinghub.elsevier.com/retrieve/pii/S1044743124000344.
5. Sehlin, D., et al. Large aggregates are the major soluble Aβ species in AD brain fractionated with density gradient ultracentrifugation. PLoS One. 2012;7(2):e32014. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0032014.
6. Söderberg, L., et al. Lecanemab, Aducanumab, and Gantenerumab — Binding Profiles to Different Forms of Amyloid-Beta Might Explain Efficacy and Side Effects in Clinical Trials for Alzheimer’s Disease. Neurotherapeutics. 2022;20(1):195-206. https://linkinghub.elsevier.com/retrieve/pii/S1878747923001150.
7. Selkoe, D. Does the Current Evidence for Lecanemab Mechanism Support a Rationale for Continued Lecanemab Dosing? Presented at Alzheimer's Association International Conference, 2024.
8. Amin, L., Harris, D.A. Aβ receptors specifically recognize molecular features displayed by fibril ends and neurotoxic oligomers. Nature Communications. 2021;12:3451. doi:10.1038/s41467-021-23507-z.
9. Ono, K., Tsuji, M. Protofibrils of Amyloid-β are Important Targets of a Disease-Modifying Approach for Alzheimer's Disease. International Journal of Molecular Sciences. 2020;21(3):952. https://www.mdpi.com/1422-0067/21/3/952
10. Noguchi‐Shinohara, M. and Shuta, K, et al. Lecanemab-Associated Amyloid-β Protofibril in Cerebrospinal Fluid Correlates with Biomarkers of Neurodegeneration in Alzheimer's Disease. Annals of Neurology. 2025; in press. https://onlinelibrary.wiley.com/doi/10.1002/ana.27175. 
11. Gustavsson, A., et al. Global estimates on the number of persons across the Alzheimer's disease continuum. Alzheimer’s & Dementia. 2023;19:658-670.
    https://alz-journals.onlinelibrary.wiley.com/doi/full/10.1002/alz.12694.
12. Morris, J.C. The Clinical Dementia Rating (CDR): current version and scoring rules. Neurology. 1993;43:2412-2414.
13. Pedrosa, H., et al. Functional evaluation distinguishes MCI patients from healthy elderly people–the ADCS/MCI/ADL scale. The Journal of Nutrition, Health and Aging. 2010;14(8):703–9.
14. U.S. Food and Drug Administration. 2023. FDA Converts Novel Alzheimer’s Disease Treatment to Traditional Approval. Last accessed: April 2025.
15. Reuters. 2023. Japan approves Alzheimer's treatment Leqembi by Eisai and Biogen. Last accessed: April 2025.
16. The Pharma Letter. 2024. Brief - Alzheimer drug Leqembi now approved in China. Last accessed: April 2025.
17. Pharmaceutical Technology. 2024. South Korea’s MFDS approves Eisai-Biogen’s LEQEMBI for Alzheimer’s. Last accessed: April 2025.
18. Pharmaceutical Technology. 2024. Hong Kong approves Leqembi for Alzheimer’s treatment. Last accessed: April 2025.
19. Pharmaceutical Business Review. 2024. Leqembi gains approval for Alzheimer’s treatment in Israel. Last accessed: April 2025.
20. United Arab Emirates Ministry of Health & Prevention. 2024. Registered Medical Product Directory. Leqembi. Last accessed: April 2025.
21. Lecanemab United Kingdom Summary of Product Characteristics. Available at: /emc/product/15908/smpc. Last accessed: April 2025.
22. The PharmaLetter. 2024. BRIEF-Mexican approval for Alzheimer’s drug Leqembi. Available at: https://www.thepharmaletter.com/brief-mexican-approval-for-alzheimers-drug-leqembi. Last accessed: April 2025.
23. Froelich L., et al. Lecanemab for treatment of individuals with early Alzheimer’s disease (AD) who are apolipoprotein E E4 (ApoE e4) non-carriers of heterozygotes. Poster presented at German Association for Psychiatry, Psychotherapy and Psychosomatics (DGPPN) conference, November 2024