EISAI : TO PRESENT THE LATEST LECANEMAB DATA, INCLUDING ARIA-E AND SUBCUTANEOUS FORMULATION, AND OTHER ALZHEIMER’S DISEASE RESEARCH AT THE ALZHEIMER’S ASSOCIATION INTERNATIONAL CONFERENCE (AAIC) 2022

No.22-57	July 26 , 2022
Eisai Co., Ltd.

EISAI TO PRESENT THE LATEST LECANEMAB DATA, INCLUDING ARIA-E AND

SUBCUTANEOUS FORMULATION, AND OTHER ALZHEIMER'S DISEASE

RESEARCH AT THE ALZHEIMER'S ASSOCIATION INTERNATIONAL

CONFERENCE (AAIC) 2022

Eisai Co. Ltd (Headquarters: Toyoko, CEO: Haruo Naito, "Eisai") announced today that the company will present research from its Alzheimer's disease (AD) pipeline, including new data for lecanemab (BAN2401), an investigational anti-amyloid beta (Aβ) protofibril antibody for the treatment of mild cognitive impairment (MCI) due to Alzheimer's disease (AD) and mild AD (collectively known as early AD) with confirmed presence of amyloid pathology in the brain, at the Alzheimer's Association International Conference(AAIC) to be held in San Diego, CA and virtually from July 31 to August 4, 2022. Eisai will present data and research in three oral and 18 poster presentations at the meeting.

On July 5, 2022 (U.S), Eisai announced that the U.S. Food and Drug Administration (FDA) accepted the Biologics License Application (BLA) for lecanemab under the accelerated approval pathway and was granted priority review, with a Prescription Drug User Fee Act (PDUFA) action date of January 6, 2023. The readout of the primary endpoint data of Clarity AD will occur in the Fall of 2022. The FDA has agreed that the results of Clarity AD when completed, can serve as the confirmatory study to verify the clinical benefit of lecanemab.

Key Eisai AAIC Presentations

• Effect of Genotype on ARIA-E Incidence by Lecanemab: Results from a modeling simulation to evaluate the effect of APOE4 genotype on ARIA-Eincidence from study 201 Core and comparison to the observed incidence in the open-labelextension among those newly treated with lecanemab. (Virtual Developing Topics #69402)
• Lecanemab Subcutaneous Dosing:
• • Results from a study in healthy subjects to evaluate the absolute bioavailability, pharmacokinetics, safety, and immunogenicity of lecanemab following a single fixed 700 mg subcutaneous dose. (Poster/Abstract #69438)
  • Modeling and simulation analysis aimed at showing the equivalence of fixed weekly subcutaneous dose of lecanemab to body weight-based 10mg/kg biweekly intravenous dose. (Poster/Abstract #69429)
• Ethnic and Racial Diversity in Eisai Clinical Trials: An evaluation of US enrollment across lecanemab (Study 201 and Clarity AD) and elenbecestat MissionAD studies in early AD to assess racial and ethnic groups and the impact of eligibility criteria in the United States. (Poster/Abstract
  # 69198)
• β-AmyloidAssays Predict Brain β-Amyloid Pathology: Data from the Eisai and Sysmex collaboration reporting on the fully automated plasma Aβ40 and Aβ42 immunoassays and their performance for predicting brain Aβ pathology defined by amyloid PET. (Poster/Abstract # 68727)

• Comprehensive CSF Tau Profiling from Dominantly Inherited Alzheimer Network (DIAN): An oral presentation that shares results from a study in patients enrolled in Washington University School of Medicine's DIAN-observationalcohort that used Eisai's anti-microtubulebinding region (MTBR) antibody, E2814, to profile MTBR-tauand then assessed timing to MTBR-tauchanges in CSF and correlation to clinical, cognitive, and biomarker changes. (Oral Presentation # 65313)

"The lecanemab data Eisai will present at AAIC 2022 continues to build the body of knowledge about our investigational anti-amyloid beta protofibril antibody as we work toward the Phase 3 confirmatory Clarity AD readout this fall," said Michael Irizarry, M.D., Senior Vice President, Deputy Chief Clinical Officer, Alzheimer's Disease and Brain Health, Eisai Inc. "Additional research presented will highlight Eisai's efforts to improve ethnic and racial diversity in our early Alzheimer's disease clinical trials in the United States so that study populations mirror the U.S. Medicare population, as well as research from our collaboration with Sysmex on potential biomarkers that may contribute to early diagnosis of Alzheimer's disease."

AAIC 2022 Presentations Relating to Eisai's Key Compounds and Research

■ Eisai Oral Presentations

Asset in Development, Session,	Oral Presentation Number, Title, Presenter/Authors
Time (Pacific Time)
E2814	Oral Presentation # 65313
Session: Using Novel Data to Refine Future	Comprehensive CSF Tau Profiling Identifies Soluble Tau
Studies	Pathophysiological Stages in Dominantly Inherited Alzheimer Network
	(DIAN): Implications for the DIAN-TU Tau Next Generation Platform
Sun, July 31, 2022
Session Time: 2:15 - 3:30 pm	Presenter: K. Horie
Presentation Time: 2:15 - 2:25 pm	Authors: K. Horie, et al
Lecanemab	Virtual Developing Topics #69402
Session VDT-4-29: Developing Topics V	Modeled Impact of APOE4 Genotype on ARIA-E Incidence in Patients
	Treated with Lecanemab
Wed, Aug 3, 2022
Session Time: 8:00 - 8:45 am	Presenter: L Reyderman
Presentation Time: 8:14 - 8:21 am	Authors: L. Reyderman, et al
General AD	Oral Presentation # 66599
Session VO-5-12: Biomarkers (non-	Novel Peptide-Driven Global Proteomics Platform to Identify Unique
neuroimaging): Proteomics in AD and DLB	Peptide Profiles Linked to Alzheimer's Disease
Thu, Aug 4, 2022	Presenter: S. Saxena
Session Time: 9:45 - 11:00 am	Authors: S. Saxena, et al
Presentation Time: 10:25 - 10:35 am

■ Eisai Poster Presentations

Asset in Development, Session,	Abstract Number, Title, Authors
Time (Pacific Time)
Lecanemab	Abstract # 66289
Session P1-01	Lecanemab (BAN2401) Infusion Reactions and Immunogenicity:
	Results from Randomized Phase 2 Study and an Open-Label
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Extension (OLE)
	Authors: I. Landry, et al

Lecanemab	Abstract #68222
Session P1-13	Strategies for Diverse Participant Recruitment to a Preclinical
Alzheimer's Disease Prevention Trial: The AHEAD Study
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Authors: D. Molina-Henry, et al
Lecanemab	Abstract #69220
Session P1-16	Neuropathological Autopsy Findings in an Individual with Alzheimer's
Disease who Received Long-Term Treatment with Lecanemab
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Authors: L. Honig, et al
Lecanemab	Abstract # 69429
Session P1-16	Subcutaneous Dose Selection of Lecanemab for Treatment of
Subjects with Early Alzheimer's Disease
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Authors: S. Hayato, et al
Lecanemab	Abstract # 69438
Session P2-16	Absolute Bioavailability of a Single, Fixed Subcutaneous Dose of
Lecanemab in Healthy Subjects
Mon, Aug 1, 2022, 12:30 - 2:15 pm	Authors: S. Rawal, et al
Lecanemab	Abstract #65104
Session P3-02	Analysis of Interaction Characteristics Between Amyloid β and
Lecanemab by HDX-MS
Tue, Aug 2, 2022, 12:30 - 2:15 pm	Authors: E. Yamauchi, et al
Lecanemab	Abstract # 69405
Session P4-28	Lifetime Clinical Benefits of Lecanemab in Early Alzheimer's Disease
Using Simulation Modeling
Wed, Aug 3, 2022, 12:30 - 2:15 pm	Authors: A. Monfared, et al
Lecanemab/elenbecestat	Abstract # 69198
Session P1-16	Diversity in Phase 2 and Phase 3 Placebo-Controlled,Double-Blind
Lecanemab and Elenbecestat Early Alzheimer's Disease Studies
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Authors: J. Grill, et al
	Abstract # 62590
E2511
	E2511, A Novel Small Compound TrkA Biased Positive Allosteric
Virtual poster	Modulator, Reinnervates Cholinergic Neuron and Activates
	Cholinergic Functions in Non-Clinical Studies
Sun, Jul 31, 2022, 7:00 - 11:55 pm
	Authors: T. Tomioka, et al
	Abstract # 66208
E2511	First-in-Human (FIH), Single- and Multiple-Ascending-Dose
	(SAD/MAD) Studies in Healthy Subjects of E2511, a Novel
Virtual platform	Tropomyosin receptor kinase A (TrkA) Positive Allosteric Modulator
(on-demand)	(PAM)
	Authors: P. Aceves, et al
General AD	Abstract # 65661
Session P1-10	Healthcare Resource Utilization (HCRU) Among Veterans with
Alzheimer's Disease
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Authors: B. Aguilar, et al

General AD	Abstract # 67811
Session P1-06	Derivation and Evaluation of Signatures using Plasma Beta-Amyloid
and pTau-181 for Brain Amyloid-β Detection
Sun, Jul 31, 2022, 12:30 - 2:15 pm	Presenter: V. Devanarayan, et al
	Abstract # 65606
neral AD	Concordance and Disconcordance in Disease Severity Classification
Session P2-09	Between Clinician Judgments and Cognitive Testing Scores for
Alzheimer's Disease in the United States Veterans Affairs Healthcare
Mod, Aug 1, 2022, 12:30 - 2:15 pm	System
	Authors: M. Li, et al
General AD	Abstract # 68231
Session P2-07	Development and Validation of AI-Based Tools for Brain Amyloid-β
Detection using MRI
Mon, Aug 1, 2022, 12:30 - 2:15 pm	Authors: V. Devanarayan, et al
	Abstract # 59971
General AD
	Development of Clinical Trial Simulation Tools for Alzheimer's
Session P4-01	Disease through the Critical Path for Alzheimer's Disease (CPAD)
	Consortium
Wed, Aug 3, 2022, 12:30 - 2:15 pm
	Authors: S. Sivakumaran, et al
General AD	Abstract # 68154
Session P4-07	Baseline Regional Tau Distribution Predicts Fast Cognitive Decline in
Subjects with Mild Cognitive Impairment
Wed, Aug 3, 2022, 12:30 - 2:15 pm	Authors: A. Charil, et al
General AD	Abstract # 63148
Virtual platform	Understanding the Impact of Social Stigma on the Patient Journey in
Alzheimer's Disease through Social Media Narratives
(on-demand)
	Authors: A. Tahami Monfared, et al

• Sysmex and Eisai Collaboration Research Poster

Asset in Development, Session,	Abstract Number, Title, Authors
Time (Pacific Time)
General AD	Abstract # 68727
Session P4-21	Highly Specific Plasma β-Amyloid Assays on the Fully Automated
	Platform Predict Brain β-Amyloid Pathology Determined by a
Wed, Aug 3, 2022, 12:30 - 2:15 pm	Centiloid Threshold of Amyloid PET
	Authors: K. Yamashita, et al

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.

MEDIA CONTACT:

Eisai Co., Ltd.

Public Relations Department

TEL: [phone]

Eisai Inc. (U.S.) Libby Holman

+ 1-201-753-1945

[e-mail]

[Notes to editors]

1. About Lecanemab (BAN2401)

Lecanemab is an investigational humanized monoclonal antibody for Alzheimer's disease (AD) that is the result of a strategic research alliance between Eisai and BioArctic. Lecanemab selectively binds to neutralize and eliminate soluble, toxic amyloid-beta (Aβ) aggregates (protofibrils) that are thought to contribute to the neurodegenerative process in AD. As such, lecanemab may have the potential to have an effect on disease pathology and to slow down the progression of the disease. Currently, lecanemab is being developed as the only anti- Aβ antibody that can be used for the treatment of early AD without the need for titration. With regard to the results from pre-specified analysis at 18 months of treatment with lecanemab 10 mg/kg IV biweekly, Study 201 demonstrated reduction of brain Aβ accumulation (P<0.0001) and slowing of disease progression measured by ADCOMS* (P<0.05) in early AD patients. The study did not achieve its primary outcome measure** at 12 months of treatment. The Study 201 open-label extension was initiated after completion of the Core period and a Gap period off treatment of 9-59 months (average of 24 months, n=180 from core study enrolled) to evaluate safety and efficacy, and is underway.

Currently, lecanemab is being studied in a confirmatory Phase 3 clinical study in symptomatic early AD (Clarity-AD), following the outcome of the Phase 2 clinical study (Study 201). 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 Alzheimer's disease (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 in combination with E2814 MTBR- tau antibody or placebo. Furthermore, Eisai has initiated a lecanemab subcutaneous dosing Phase 1 study.

• Developed by Eisai, ADCOMS (AD Composite Score) combines items from the ADAS-Cog (Alzheimer's Disease Assessment Scale-cognitive subscale), CDR (Clinical Dementia Rating) and the MMSE (Mini- Mental State Examination) scales to enable a sensitive detection of changes in clinical functions of early AD symptoms and changes in memory. The ADCOMS scale ranges from a score of 0.00 to 1.97, with higher score indicating greater impairment.
• An 80% or higher estimated probability of demonstrating 25% or greater slowing in clinical decline at 12 months treatment measured by ADCOMS from baseline compared to placebo.

2. About E2814