TOKYO and CAMBRIDGE, Mass., Mar 23, 2026 - (JCN Newswire via SeaPRwire.com) - Eisai Co., Ltd. and Biogen Inc. announced today that new real‑world findings from an analysis of long‑term treatment persistence and baseline characteristics among people receiving intravenous (IV) lecanemab (generic name, brand name LEQEMBI®), an anti‑amyloid‑β (Aβ) protofibril antibody, showed that most patients continue with ongoing lecanemab therapy after the initial 18 months of treatment. The analysis was presented at the 20th International Conference on Alzheimer’s and Parkinson’s Diseases and Related Neurological Disorders (AD/PD™ 2026) in Copenhagen, Denmark, and online.In real‑world clinical practice, patients with chronic diseases who stay on their treatments longer tend to experience better clinical outcomes and higher satisfaction.1,2 Ninety-four percent of patients who completed 18 months of lecanemab treatment in the Phase III Clarity AD chose to continue maintenance treatment by enrolling in the subsequent open-label, long-term extension (OLE) study. In the OLE of Clarity AD study, patients continue to benefit from four years of lecanemab treatment compared with the natural course of Alzheimer’s disease (Alzheimer’s Disease Neuroimaging Initiative: ADNI*).Long-Term Persistence and Patient Characteristics for Lecanemab in Real-World Use in the United States (Presentation: March 20, 17:05 CET)This analysis is the first time real-world lecanemab data on treatment persistence beyond 18 months has been reported.This study was a retrospective observational analysis using the PurpleLab® CLEAR Claims database, a comprehensive dataset based on medical insurance claims across the United States and was conducted to evaluate the long‑term treatment persistence of lecanemab in real‑world clinical practice.Patient background and dosing The analysis population consisted of 10,763 individuals who met the requirement for continuous healthcare encounters, out of the 13,388 individuals recorded in the database who received at least one intravenous treatment with lecanemab between January 6, 2023 and November 30, 2025. At baseline, the mean age was 73.8 years and 56.5% were female. The most common comorbidities were dyslipidemia (42.2%) and hypertension (36.9%). The mean follow-up duration was 350.9 days. The average number of administrations was 1.7 per month, and the mean dosing interval was 16.4 days (median 14 days), which was generally consistent with the recommended every two weeks dosing.Long-Term persistence results The time-dependent proportion of patients who remained on lecanemab treatment was evaluated, using the Kaplan–Meier method in a subgroup of 371 patients who initiated treatment in 2023 and had 20 months of continuous follow-up, thereby enabling assessment of long-term treatment persistence beyond 18 months. As a result, 78.4% of individuals continued lecanemab treatment at 18 months, 71.7% at 20 months, and 67.3% at 24 months. Of the 78.4% of patients who remained on lecanemab at 18 months, the majority of them continued treatment during the maintenance period beyond 18 months, confirming a high rate of treatment persistence with lecanemab in real-world clinical practice. The patient characteristics and dosing patterns observed in this claims-based analysis were generally similar to those reported in the Clarity AD. Furthermore, the relatively high treatment adherence observed among individuals suggests that potential delays due to MRI monitoring requirements, adverse events, and other factors did not substantially affect lecanemab dosing.Eisai serves as the lead for lecanemab’s development and regulatory submissions globally with Eisai and Biogen co-commercializing and co-promoting the product and Eisai having final decision-making authority.* ADNI is a clinical research project launched in 2005 to develop methods to predict the onset and progression of AD and to confirm the effectiveness of treatments. The project involves a multi-year longitudinal observation targeting healthy elderly individuals as well as patients with mild cognitive impairment (MCI) and early stages of AD.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 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril) and insoluble forms of amyloid-beta (Aβ).Lecanemab has been approved in 53 countries and regions including Japan, the United States, China, Europe, South Korea, Taiwan, and Saudi Arabia, and is under regulatory review in 6 countries. Following the initial phase with treatment every two weeks for 18 months, intravenous (IV) maintenance dosing with treatment every four weeks was approved in 7 countries including the U.S., China, the UK, and others, and applications have been filed in 10 countries and regions. The U.S. FDA approved Eisai’s Biologics License Application (BLA) for subcutaneous maintenance dosing with LEQEMBI IQLIK in August 2025. A Supplemental Biologics License Application (sBLA) for initiation treatment was accepted in January 2026. The sBLA has been granted Priority Review, with a Prescription Drug User Fee Act (PDUFA) action date of May 24, 2026. In November 2025, an application for a subcutaneous injectable formulation in Japan was submitted. In January 2026, the Biologics License Application (BLA) for the subcutaneous formulation was accepted in China. In December 2025, Lecanemab (IV) has been included in the “Commercial Insurance Innovative Drug List”, recently introduced by the National Healthcare Security Administration (NHSA) of China.In the global Phase 3 placebo-controlled, double-blind, parallel-group, randomized 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.3,4Over three years of treatment, including both the core study and the OLE, data showed lecanemab demonstrated a 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 benchmarked 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.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.** BioFINDER subjects are similar to Study 301 and ADNI subjects, except all BioFINDER subjects are in the MCI stage and no mild AD subjects are included, and their baseline CDR-SB is lower. BioFINDER is a largescale, long-term prospective study led by Lund University in Sweden, aiming to establish early. diagnosis and elucidate pathophysiology of neurodegenerative diseases. In addition to AD, the study also focuses on conditions including Parkinson's Disease. Individuals participating in the study undergo regular clinical assessments, cognitive function tests, brain imaging (MRI, Aβ PET, Tau PET), and collection of biomarkers from blood and cerebrospinal fluid (CSF).About ProtofibrilsProtofibrils are believed to contribute to the brain injury that occurs with AD and are considered to be the most toxic form of soluble Aβ, having a primary role in the cognitive decline associated with this progressive, debilitating condition.3 Protofibrils cause injury to neurons in the brain, which in turn, can negatively impact cognitive function via multiple mechanisms, 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. It is believed the reduction of protofibrils may prevent the progression of AD by reducing damage to neurons in the brain and cognitive dysfunction.4About the Collaboration between Eisai and Biogen for ADEisai 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.About the Collaboration between Eisai and BioArctic for ADSince 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.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.About BiogenFounded 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, YouTubeMEDIA CONTACTSEisai Co., Ltd.Public Relations DepartmentTEL: +81 (0)3-3817-5120Eisai Europe, Ltd.(Europe, Australia, New Zealand and Russia)EMEA Communications Department+44 (0) 7739-600-678EMEA-comms@eisai.netEisai Inc. (U.S.)Libby Holman+1-201-753-1945Libby_Holman@Eisai.comBiogen Inc.Madeleine Shin+1-781-464-3260public.affairs@biogen.comINVESTOR CONTACTSEisai Co., Ltd.Investor Relations DepartmentTEL: +81 (0) 3-3817-5122Biogen Inc.Tim Power+ 1-781-464-2442IR@biogen.comBiogen Safe HarborThis news release contains forward-looking statements, including about the potential clinical effects of lecanemab (marketed as LEQEMBI); the potential benefits, safety and efficacy of lecanemab; potential regulatory discussions, submissions and approvals and the timing thereof including for LEQEMBI (lecanemab) subcutaneous autoinjector (SC-AI); the potential to expand options and reduce healthcare resources by treating Alzheimer's disease at home; 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. 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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.Digital Media DisclosureFrom time to time, we have used, or expect in the future to use, our investor relations website (investors.biogen.com), the Biogen LinkedIn account (linkedin.com/company/biogen-) and the Biogen X account (https://x.com/biogen) as a means of disclosing information to the public in a broad, non-exclusionary manner, including for purposes of the SEC’s Regulation Fair Disclosure (Reg FD). Accordingly, investors should monitor our investor relations website and these social media channels in addition to our press releases, SEC filings, public conference calls and websites, as the information posted on them could be material to investors.References(1) Guerci B et al. Lack of treatment persistence and treatment nonadherence as barriers to glycaemic control in patients with type 2 diabetes. Diabetes Therapy, 2019; 10(2), 437-449.(2) Menditto E et al. Persistence as a robust indicator of medication adherence-related quality and performance. International journal of environmental research and public health, 2021; 18(9), 4872.(3) Cohen S., et al. J Prev Alzheimers Dis.2022;9(3):507-522.(4) Morris JC. Neurology. 1993;43(11):2412-4.(5) Amin L, Harris DA. Aβ receptors specifically recognize molecular features displayed by fibril ends and neurotoxic oligomers. Nat Commun. 2021; 12:3451. doi:10.1038/s41467-021-23507-z(6) Ono K, Tsuji M. Protofibrils of Amyloid-β are Important Targets of a Disease-Modifying Approach for Alzheimer's Disease. Int J Mol Sci. 2020;21(3):952. doi: 10.3390/ijms21030952. PMID: 32023927; PMCID: PMC7037706. Copyright 2026 JCN Newswire via SeaPRwire.com. All rights reserved. www.jcnnewswire.com