EISAI TO PRESENT FOUR-YEAR EFFICACY AND SAFETY DATA ON CONTINUOUS TREATMENT WITH LECANEMAB AT THE ALZHEIMER’S ASSOCIATION INTERNATIONAL CONFERENCE 2025

Latest findings from Eisai's robust Alzheimer's disease (AD) pipeline include results from lecanemab long-term data, an immunoassay for measuring amyloid-B protofibrils in cerebrospinal fluid, and a subcutaneous form of lecanemab for continued treatment of AD

AD is a progressive, relentless disease caused by a continuous underlying neurotoxic process that begins before and continues after plaque deposition

Eisai Inc. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) announced today that the company will present the latest findings from its robust Alzheimer's disease (AD) pipeline and research, including our dual-acting, anti-amyloid beta (AB) protofibril* antibody for the treatment of AD, lecanemab (generic name, U.S. brand name: LEQEMBI®), and anti-MTBR (microtubule binding region) tau antibody, etalanetug (E2814), at the Alzheimer's Association International Conference (AAIC), being held in Toronto and virtually from July 27 – 31. Eisai will present 21 oral presentations, 24 posters, three (3) symposia and two (2) lecanemab product theaters.

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Key Oral Lecanemab Presentations

— Four-year Data: On Wednesday, July 30, as part of the “Developing Topics Session: Innovative Therapeutic Approaches” (8:00 – 8:45 AM EDT), initial four-year findings will be presented on lecanemab from the Phase 3 Clarity AD Open-Label Extension in Early Alzheimer's Disease trial.

— Subcutaneous Maintenance Dosing: A Featured Research Session on Wednesday, July 30 (9:00 – 10:30 AM EDT) will include data on the potential of a new and convenient option for ongoing lecanemab treatment, the subcutaneous formulation for maintenance dosing.

— Real World Case Studies: A Developing Topics Session on Sunday, July 27 (9:00 – 10:30 AM EDT) will include data on real-world case studies and patient pathway learnings from diverse U.S. clinical settings two years post-approval of lecanemab.

Key Lecanemab Poster Presentation

— A Poster Presentation on Monday, July 28 (viewing available from 7:30 AM – 4:15 PM EDT) will share findings on cerebrospinal fluid (CSF) samples collected from the Clarity AD trial and analyzed using the novel, sensitive immunoassay developed to measure AB protofibrils in CSF.

Key Oral E2814 Presentation

— A Featured Research Session on Wednesday, July 30 (4:15 – 5:45 PM EDT) will include findings from the Anti-Tau Etalanetug (E2814) with Lecanemab Therapy in Individuals with Dominantly Inherited Alzheimer's Disease: A First Look at Baseline Characteristics and Impact of 6-Month Lecanemab Treatment on Amyloid PET and Safety in the DIAN-TU-001 NexGen Trial.

“The data presented at AAIC 2025 will highlight long-term findings from lecanemab's open-label extension trial, real-world lecanemab case studies as well as results on a subcutaneous formulation and dosing regimen that may offer patients more flexibility to continue treatment to fight Alzheimer's disease,” said Lynn D. Kramer, M.D., FAAN, Chief Clinical Officer, Deep Human Biology Learning (DHBL), Eisai. “We will also share preliminary results from the DIAN-TU-001 NexGen Trial, exploring etalanetug with background lecanemab therapy to slow or prevent the progression of Alzheimer's disease. As we gain more experience using dual-acting lecanemab in different clinical settings and continue to explore new avenues to improve the diagnosis and treatment of Alzheimer's disease, we are hopeful about the future. We remain committed to patients and their loved ones who are impacted by this progressive, relentless disease, caused by a continuous underlying neurotoxic process that begins before and continues after plaque is removed from the brain.”

Key Featured Research Sessions

Featured Research Session (FRS), #1-31-FRS-A: Anti-Amyloid Therapies in Clinical Practice: Real World Evidence and Implementation Consideration

4:15 – 5:45 PM EDT, Sunday, July 27

Session ProgramIndirect Treatment Comparison of ARIA Outcomes for Lecanemab ComparedtoDonanemab Based on Reported Results (Abstract ID 103048)

Featured Research Session, #4-13-FRS-C: Lecanemab Subcutaneous Formulation for Maintenance Dosing: The Potential of a New and Convenient Option for Ongoing Treatment in Early Alzheimer's Disease

9:00 – 10:30 AM EDT, Wednesday, July 30

Session ProgramDevelopment of Subcutaneous Lecanemab: Establishing the Comparability ofSubcutaneous and IntravenousLecanemab Formulations (Abstract ID104694)Lecanemab Subcutaneous Formulation for Maintenance Dosing in EarlyAlzheimer's Disease (Abstract ID 104693)Clinical and Pharmacologic Profile of a Subcutaneous LecanemabFormulation (Abstract ID 104691)Subcutaneous Lecanemab: Potential Benefits and Place in Therapy (AbstractID 104695)

Featured Research Session, #4-31-FRS-B: Anti-Tau Etalanetug (E2814) with Lecanemab Therapy in Individuals with Dominantly Inherited Alzheimer's Disease: A First Look at Baseline Characteristics and Impact of 6-Month Lecanemab Treatment on Amyloid PET and Safety in the DIAN-TU-001 NexGen Trial

4:15 – 5:45 PM EDT, Wednesday, July 30

Session ProgramDIAN-TU-001 Trial (Tau NexGen) Rationale and Enrollment Experience(Abstract ID 105298)Baseline Participant Clinical Characteristics in the DIAN-TU-001 Trial(Abstract ID 105299)Baseline Imaging Characteristics of Participants in the Phase II/III DIAN-TU-001 TauNexGen Trial for Dominantly Inherited Alzheimer's Disease (AbstractID 105301)Lecanemab in DIAD: 6-Month Amyloid PET Results from the DIAN-TU-001Trial (Abstract ID 105303)Safety of Lecanemab After 6-Month Treatment in the DIAN-TU-001 Trial(Abstract ID 105304)

Key Developing Topics Sessions

Developing Topics On Real-World Data

8:00 – 8:45 AM EDT on Sunday, July 27

Session ProgramPatient, Care Partner, and Health Care Professional Opinion of theLecanemab Autoinjector for Subcutaneous Delivery in Early Alzheimer'sDisease Patients (Abstract ID 108809)

Lecanemab Two Years Post-Approval: Real-World Case Series and Patient Pathway Learnings from Diverse US Clinical Settings

9:00 – 10:30 AM EDT on Sunday, July 27

Session ProgramReal-World Use of Lecanemab in Patients with Early Alzheimer's Diseasein the United States: A Case Series Review (Abstract ID 108599)Real-World Use of Lecanemab with Consideration of Race, Ethnicity andGeographical Diversity (Abstract ID 108602)Real-World Use of Lecanemab in APOE 4 Homozygotes and in Patients onAntithrombotic Therapy (Abstract ID 108603)Physician Satisfaction with Lecanemab in Early Alzheimer's Disease: Real-World Insights from Prescribers in the United States (Abstract ID 108605)Real-World Insights on the Lecanemab Patient Pathway in Early Alzheimer'sDisease in the United States (Abstract ID 108606)Blood-Based Biomarkers in the Lecanemab Patient Pathway for EarlyAlzheimer's Disease in the United States (Abstract ID 108607)

Developing Topics On Innovative Therapeutic Approaches

8:00 – 8:45 AM EDT, Wednesday, July 30

Session ProgramThe Lecanemab Clarity AD Open-Label Extension in Early Alzheimer'sDisease: Initial Findings from the 48-Month Analysis (Abstract ID 108905)

Additional Featured Research and Developing Topics Sessions

Biomarkers Featured Research Session, #2-17-FRS-A: Sex Specific Risk And ProtectiveJuly 28 (Mon.) Factors in Alzheimer's Disease9:00 – 10:30 AM EDT Sex-Stratified GWAS Meta-Analyses Reveal Novel Sex-Specific Association withCSF Biomarkers of Alzheimer's Disease (Abstract ID 102560)Lecanemab Developing Topics Session: Developing Topics On Tau BiomarkersJuly 29 (Tues.) Variations in Plasma p-Tau217 by Sociodemographic Factors Across World2:00 – 3:30 PM EDT Regions in a Preclinical AD Clinical Trials Program: The AHEAD 3-45 Study (Abstract ID 108909)Clinical Trials Featured Research Session, #4-26-FRS-A: Innovative Use of StatisticalJuly 30 (Weds.) Models and Machine Learning to Enhance AD Clinical Trials2:00 – 3:30 PM EDT Baseline Predictions of PACC Progression Trajectories in Preclinical AD Improve the Precision and Power of Treatment Effect Assessments (Abstract ID 99560)

Poster Presentations

Asset/Project, Title, Abstract NumberPresentation Dateand Time**Lecanemab Results from a Human Factor Study Supporting Safe and Effective Use of theJuly 27 (Sun.) Lecanemab Subcutaneous Autoinjector (Abstract ID 106273)Lecanemab Delphi Consensus for Implementation of Anti-Amyloid mAb Initiation in PrivateJuly 27 (Sun.) Practice Neurology: Preliminary Recommendations from Experienced Providers (Abstract ID 108789)Lecanemab Target Engagement of Lecanemab on CSF AB Protofibril Toxic Species inJuly 28 (Mon.) Clarity AD (Abstract ID 108918)Lecanemab Understanding Real-World Clinical Experience with Lecanemab: Capturing theJuly 28 (Mon.) Patient and Care Partner Voice Through Social Media Listening (Abstract ID 102018)Lecanemab Patient and Care Partner Expectations and Emotional Experiences ofJuly 29 (Tues.) Lecanemab: A Social Media Listening Study (Abstract ID 101001)Lecanemab Lecanemab Real-World Use Perspectives from a New England Alzheimer'sJuly 29 (Tues.) Disease Center: A Retrospective Chart Review (Abstract ID 101388)Lecanemab Transitioning from Clinical Trial to Clinical Practice for Long-Term LecanemabJuly 30 (Weds.) Treatment in Early Alzheimer's Disease: Perspectives from an Alzheimer's Disease Treatment Center (Abstract ID 101400)E2025 Quantification of EphA4 Turnover Rate and Subsequent Validation of TargetJuly 29 (Tues.) Engagement for E2025, a Novel Anti-EphA4 Antibody, in Human Neural Cells (Abstract ID 96834)E2814 E2814 Mitigates Tau Pathology: Inhibiting Tau Uptake and Promoting MTBR-July 30 (Weds.) Tau Clearance Through Microglial Pathways in vitro (Abstract ID 102696)Biomarkers and Imaging External Validation of Joint Propagation Model-Based Tau PET CenTauR UnitsJuly 27 (Sun.) (Abstract ID 106362)Biomarkers and Imaging Identifying Differentially Expressed Proteins Between Amyloid Positive andJuly 28 (Mon.) Amyloid Negative Subjects Based on Alamar Multiplex Assay Data Using MissionAD Samples (Abstract ID 107031)Biomarkers and Imaging Influence of Demographics and Scan Time on MK6240 Off-Target Signal andJuly 29 (Tues.) Reference Region Selection (Abstract ID 100424)Biomarkers Observational Study Evaluating Blood-Based Biomarker Use for ConfirmatoryJuly 27 (Sun.) Alzheimer's Disease Diagnosis in Real-World Clinical Practice Within the United States (Abstract ID 99857)Biomarkers A De Novo-Assisted Strategy to Identify Novel IncRNA-Encoded Peptides inJuly 28 (Mon.) Cerebrospinal Fluid of Demented Subjects With or WithoutAmyloid Positivity (Abstract ID 106893)Biomarkers Impact of Blood-Based Biomarkers on Access to Alzheimer's DiseaseJuly 28 (Mon.) Treatments: A Simulation Study in Japan (Abstract ID 102553)Biomarkers Implementation Science Study Evaluating the Real-World Use of Blood-BasedJuly 29 (Tues.) Biomarkers as Confirmatory Diagnostic Tools for Alzheimer's Disease in the United States (Abstract ID 99804)Biomarkers Characterization of Lewy Body Copathology in Early AD Clinical TrialJuly 29 (Tues.) Population Demonstrates Similarities and Differences Compared to Natural History Studies in Alzheimer's Disease Patients (Abstract ID 107102)Biomarkers Value of Blood-Based Biomarker Testing to Diagnose, Identify and MonitorJuly 30 (Weds.) Patients with Alzheimer's Disease: A Structured Literature Review (Abstract ID 99842)Biomarkers Alzheimer's Disease Molecular Subtypes in a Clinical Trial Cohort (Abstract IDJuly 30 (Weds.) 105257)General AD Operational Consideration and Best Practices for Implementation of an EarlyJuly 27 (Sun.) Alzheimer's Disease Patient Care Pathway (Abstract ID 108093)General AD Estimating Clinical Transitions in Patients with Alzheimer's Using InstrumentalJuly 27 (Sun.) Activities of Daily Living (IADL) (Abstract ID 107058)General AD Staging Alzheimer's Disease Using the Functional Assessment Screening ToolJuly 28 (Mon.) (FAST): A Crosswalk with the Montreal Cognitive Assessment (MoCA) (Abstract ID 107045)General AD Time to Alzheimer's Disease Diagnosis in Japan: A RetrospectiveJuly 29 (Tues.) Observational Study (Abstract ID 97026)General AD Alzheimer's Disease Staging by Instrumental Activities of Daily Living (IADL):July 30 (Weds.) A Crosswalk with the Montreal Cognitive Assessment (MoCA) (Abstract ID 107009)

**Poster viewing time is set from 7:30 AM – 4:15 PM EDT on the date of presentation

Eisai-Sponsored Symposia

Asset/Project, TitlePresentation Dateand TimeGeneral AD Smoldering Alzheimer's Disease: The Ongoing Benefit of Addressing MultipleJuly 28 (Mon.) Pathologies6:00 – 7:30 PM EDTGeneral AD Unlock Your Brain: Exploring Alzheimer's Disease from the Inside OutJuly 30 (Weds.)6:15 – 7:45 AM EDTGeneral AD Brain Health Navigator-Ensuring Efficient and Effective Alzheimer's DiseaseJuly 30 (Weds.) Diagnostic and Clinical Care Pathways6:00 – 7:30 PM EDT

Eisai-Sponsored Product Theaters

Asset/Project, TitlePresentation Dateand TimeLecanemab Early Diagnosis, Early Treatment: Identifying Patients for Greater Benefit inJuly 27 (Sun.) Mild Cognitive Impairment Due to Alzheimer's Disease12:25 – 1:05 PM EDTLecanemab Best Practices in Early Alzheimer's Disease Care: Creating a Plan fromJuly 28 (Mon.) Screening Through Long-Term Treatment12:25 – 1:05 PM EDT

Product theaters will feature presentations based on real-world clinical experience with lecanemab – providing attendees with an opportunity to hear best practices and expert guidance on using this therapy.

This release discusses investigational uses of agents in development and is not intended to convey conclusions about efficacy or safety. There is no guarantee that such investigational agents will successfully complete clinical development or gain health authority approval.

* Protofibrils are believed to contribute to the brain injury that occurs with AD and are considered to be the most toxic form of AB, having a primary role in the cognitive decline associated with this progressive, debilitating condition.1Protofibrils 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 AB 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.2

MEDIA CONTACTSEisai Inc. (U.S.)Julie Edelman+1-862-213-5915Julie_Edelman@Eisai.com

[Notes to editors]

— About lecanemab (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 (AB). Lecanemab is approved and being marketed in the U.S.,3Japan,4China,5South Korea,6Hong Kong,7Israel,8theUnited Arab Emirates,9theUnited Kingdom,10Mexico,11Macau,12 Oman, Taiwan,13 European Union,14 Qatar, Singapore15 and Thailand16 for the treatment of Alzheimer's disease (AD) in patients with Mild Cognitive Impairment (MCI) or mild dementia stage of disease (collectively referred to as early AD). Eisai has submitted applications for approval of lecanemab in 11 countries and regions.

SinceJuly 2020the 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. SinceJanuary 2022, the Tau NexGen clinical study for Dominantly Inherited AD (DIAD), that is conducted by Dominantly Inherited Alzheimer Network Trials Unit (DIAN-TU), led byWashington UniversitySchool of Medicine inSt. Louis, is ongoing and includes lecanemab as the backbone anti-amyloid therapy.

— About the Collaboration betweenEisai 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 betweenEisai 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 inDecember 2007. The development and commercialization agreement on the antibody lecanemab back-up was signed in May 2015.

References

— Amin L, Harris DA. AB receptors specifically recognize molecular features displayed by fibril ends and neurotoxic oligomers. Nat Commun. 2021;12:3451. doi: 10.1038/s41467-021-23507-z.

— Ono K, Tsuji M.Protofibrils of Amyloid-B 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.

— U.S. Food and Drug Administration. 2023. FDA Converts Novel Alzheimer's Disease Treatment to Traditional Approval. Last accessed: July 2025.

— Reuters. 2023. Japan approves Alzheimer's treatment Leqembi by Eisai and Biogen. Last accessed:July 2025.

— ThePharma Letter. 2024. Brief – Alzheimer drug Leqembi now approved inChina. Last accessed:July 2025.

— Pharmaceutical Technology. 2024. South Korea'sMFDS approves Eisai-Biogen's LEQEMBI for Alzheimer's. Last accessed:July 2025.

— Pharmaceutical Technology. 2024. Hong Kong approves Leqembi for Alzheimer's treatment. Last accessed:July 2025.

— Israel Ministry of Health. TheIsraeli Drug Registry. Leqembi. Last accessed: July 2025.

— United Arab Emirates Ministry of Health & Prevention. 2024. Registered Medical Product Directory.Leqembi. Last accessed:July 2025.

— BioSpace. 2024. Leqembi authorized for early Alzheimer's disease inGreat Britain. Last accessed:July 2025.

— COFEPRIS authorizes innovative treatment for Alzheimer's patients. Available at:https://bit.ly/3OKks6Y. Last accessed:July 2025.

— Macau Special Administrative Region Drug Search. ssm.gov.mo/dafweb/. Last accessed: July 2025.

— Taiwan Food and Drug Administration Assessment Report.http://bit.ly/454Oawe. Last accessed: July 2025.

— European Medicines Agency.Leqembi | European Medicines Agency (EMA). Last accessed: July 2025.

— Health Sciences Authority. https://www.hsa.gov.sg/announcements/new-drug-approval/new-drug-approvals—may-2025. Last accessed: July 2025.

— Thailand Food and Drug Administration, Ministry of Public Health. pertento.fda.moph.go.th/FDA_INFORMATION_DRUG/Home/Phar_Product_Inform_Page?Newcode=U1DR1C1072680001311C. Last accessed: July 2025.

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