FOR GLOBAL MEDIA AND JOURNALISTS OUTSIDE THE EMEA REGION
Leqembi®

(lecanemab) Authorized for Early Alzheimer’s Disease in Great Britain

In Great Britain, lecanemab is indicated for the treatment of mild cognitive impairment and mild
dementia due to Alzheimer’s disease (AD) in adult patients that are apolipoprotein E ε4 (ApoE ε4)*
heterozygotes or non-carriers 1
Great Britain becomes the first country in Europe to authorize the medicine, which targets anunderlying cause of AD1
TOKYO and CAMBRIDGE, Mass., August 22, 2024 – 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 humanizedamyloid-beta (Aβ) monoclonal antibody “Leqembi®” (brand name, generic name: lecanemab) has been
granted a Marketing Authorization by the Medicines and Healthcare products Regulatory Agency(MHRA) in Great Britain.1 Lecanemab is indicated for the treatment of mild cognitive impairment (MCI)
and mild dementia due to Alzheimer’s disease (AD) in adult patients that are apolipoprotein E ε4 (ApoEε4)* heterozygotes or non-carriers.1 Lecanemab becomes the first treatment for early AD (MCI and mild
dementia due to AD) 2 that targets an underlying cause of the disease, to be authorized in a country inEurope.1
Lecanemab selectively binds to Aβ aggregate species, with preferential activity for toxic Aβ protofibrils**(as well as fibrils, which are a major component of Aβ plaques).2,3,4 It binds to these aggregate Aβ
species to neutralize and clear them from the brain.2,3,4
The approval was primarily based on Phase 3 data from Eisai’s global, placebo-controlled, double-blind,parallel-group, randomized Clarity AD clinical trial, in which the medicine met its primary endpoint(change from baseline in the Clinical Dementia Rating Sum of Boxes [CDR-SB]† at 18 months) and all
key secondary endpoints with statistically significant results.2 In the indicated population in Great Britain,
the most common adverse reactions were infusion-related reaction, amyloid-related imaging
abnormalities with hemorrhage (small spots of bleeding) (ARIA-H)‡, fall, headache and amyloid-related
imaging abnormalities with cerebral edema (build-up of fluid) (ARIA-E)‡‡.1
In the United Kingdom, it is estimated that 982,000 people are living with dementia, 5 and AD is thecause in 60-70% of people with dementia. 6 These numbers are expected to rise, as the population
ages.5,6
Eisai is working collaboratively with the National Institute for Health and Care Excellence (NICE), theScottish Medicines Consortium (SMC) and the National Health Service (NHS) to make this medicine
available to eligible people living with early AD as soon as possible.
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. In Great Britain, Eisai and Biogen will co-promote the medicine, with Eisai distributing the
product as the Marketing Authorization holder.

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*Apolipoprotein E is a protein involved in the metabolism of fats in humans. It is implicated in AD.
**Protofibrils are thought to be the most toxic Aβ species that contribute to brain damage in AD and play a majorrole in the cognitive decline of this progressive and devastating disease. Protofibrils can cause neuronal damage
in the brain, which can subsequently adversely affect cognitive function through multiple mechanisms. 7 The
mechanism by which this occurs has been reported not only by increasing the formation of insoluble Aβ plaques,but also by directly damaging signaling between neurons and other cells. It is believed that reducing protofibrils
may reduce neuronal damage and cognitive impairment, potentially preventing the progression of AD. 8†CDR-SB is a commonly used diagnostic tool, which can help to stage dementia due to AD. 9 It is a global cognitiveand functional scale that measures six domains of functioning, including memory, orientation, judgement andproblem solving, community affairs, home and hobbies, and personal care.9‡ARIA-H: amyloid-related imaging abnormalities with hemorrhage (microhemorrhages, and superficial siderosis).
‡‡ARIA-E: amyloid-related imaging abnormalities with oedema (edema/effusion).

More information can be found in the Summary of Product Characteristics and Patient Information
leaflets which will be published on the MHRA Products website within 7 days of approval.
MEDIA CONTACTS
Eisai Co., Ltd.
Public Relations Department
TEL: +81 (0)3-3817-5120

Biogen Inc.
Jack Cox+ 1-781-464-3260
public.affairs@biogen.com

Eisai Europe, Ltd.
EMEA Communications Department+44 (0) 7974-879-419
Emea-comms@eisai.net
Eisai Inc. (U.S.)
Libby Holman
1-201-753-1945
Libby_Holman@eisai.com
INVESTOR CONTACTS
Eisai Co., Ltd.
Investor Relations Department
TEL: +81 (0) 3-3817-5122

Biogen Inc.
Chuck Triano+ 1-781-464-2442
IR@biogen.com

Notes to Editors:
1. About lecanemab (Leqembi®)
Lecanemab is the result of a strategic research alliance between Eisai and BioArctic. It is a humanizedimmunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril)and insoluble forms of amyloid-beta (Aβ).2,3
Lecanemab’s approval in Great Britain 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 statisticallysignificant 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 confirmed2presence of amyloid pathology), of which 1,521 were in the indicated population in the label in GreatBritain (ApoE ε4 heterozygotes or non-carriers).1 Of the total number of patients randomized 31% werenon-carriers, 53% were heterozygotes and 16% were homozygotes.1 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.1
The primary endpoint was the global cognitive and functional scale, CDR-SB.1 In the Clarity AD clinical
trial, treatment with lecanemab, in the indicated population in Great Britain (ApoE ε4 heterozygotes or
non-carriers), reduced clinical decline on CDR-SB by 33% 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 1.15 with lecanemab and 1.73 with placebo (difference,−0.58; 95% confidence interval [CI], −0.81 to −0.34; P<0.00001).1 CDR-SB is a global cognitive andfunctional scale that measures six domains of functioning, including memory, orientation, judgement
and problem solving, community affairs, home and hobbies, and personal care.9
In addition, the secondary endpoint from the AD Cooperative Study-Activities of Daily Living Scale forMild Cognitive Impairment (ADCS-MCI-ADL), which measures information provided by people caring
for patients with AD, noted 39% less decline compared to placebo at 18 months.1 The adjusted meanchange from baseline at 18 months in the ADCS-MCI-ADL score was −3.5 in the lecanemab group and−5.7 in the placebo group (difference, 2.2; 95% CI, 1.3 to 3.1; P<0.00001).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.
In the indicated population (ApoE ε4 heterozygotes or non-carriers), the most common adverse
reactions were infusion-related reaction (26%), ARIA-H (13%), fall (11%), headache (11%) and ARIAE (9%).1
Lecanemab is licensed in the U.S., 10 Japan, 11 China, 12 South Korea, 13 Hong Kong, 14 Israel, 15 theUnited Arab Emirates 16 and Great Britain1 and marketed in the U.S., Japan and China. Eisai has also
submitted applications for approval of lecanemab in 10 countries and regions, including the European
Union.
: This medicine is subject to additional monitoring. This will allow quick identification of new safety
information.
2. About NHS, NICE and SMC
The NHS is a public healthcare system with the principle of providing free medical services to citizens.
The NICE and the SMC are independent bodies that carry out assessments on the status of all newly
licensed medicines, all new formulations of existing medicines and new indications for establishedproducts regarding their health benefits and price justification as advisory boards to the NHS about
whether or not a newly licensed drug should be accepted for use under national health insurance.
3. 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.
4. About the Collaboration between Eisai and BioArctic for AD
Since 2005, Eisai and BioArctic have had a long-term collaboration regarding the development andcommercialization 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 back-up was signed in May
2015.

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5. About Eisai Co., Ltd.
Eisai's Corporate Concept is "to give first thought to patients and people in the daily living domain, andto increase the benefits that health care provides." Under this Concept (also known as human healthcare (hhc) Concept), we aim to effectively achieve social good in the form of relieving anxiety overhealth and reducing health disparities. With a global network of R&D facilities, manufacturing sites andmarketing subsidiaries, we strive to create and deliver innovative products to target diseases with highunmet 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.
6. About Biogen
Founded in 1978, Biogen is a leading biotechnology company that pioneers innovative science todeliver new medicines to transform patient’s lives and to create value for shareholders and ourcommunities. We apply deep understanding of human biology and leverage different modalities toadvance first-in-class treatments or therapies that deliver superior outcomes. Our approach is to takebold 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. The website
and social media channels are intended for audiences outside of the UK and Europe.
Biogen Safe Harbor
This news release contains forward-looking statements, about the potential clinical effects oflecanemab; 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 anticipatedbenefits and potential of Biogen's collaboration arrangements with Eisai; the potential of Biogen'scommercial business and pipeline programs; including lecanemab; and risks and uncertainties
associated with drug development and commercialization. These statements may be identified bywords such as "aim," "anticipate," "believe," "could," "estimate," "expect," "forecast," "intend," "may,""plan," "possible," "potential," "will," "would" and other words and terms of similar meaning. Drugdevelopment and commercialization involve a high degree of risk, and only a small number of researchand development programs result in commercialization of a product. Results in early-stage clinicalstudies may not be indicative of full results or results from later stage or larger scale clinical studies anddo not ensure regulatory approval. You should not place undue reliance on these statements.
These statements involve risks and uncertainties that could cause actual results to differ materially fromthose reflected in such statements, including without limitation unexpected concerns that may arise
from additional data, analysis or results obtained during clinical studies; the occurrence of adverse
safety events; risks of unexpected costs or delays; the risk of other unexpected hurdles; regulatory
submissions may take longer or be more difficult to complete than expected; regulatory authorities may
require additional information or further studies, or may fail or refuse to approve or may delay approvalof Biogen's drug candidates; including lecanemab; actual timing and content of submissions to anddecisions made by the regulatory authorities regarding lecanemab; uncertainty of success in thedevelopment and potential commercialization of the medicine; failure to protect and enforce Biogen's
data, intellectual property and other proprietary rights and uncertainties relating to intellectual property
claims and challenges; product liability claims; and third party collaboration risks, results of operations

4and financial condition. The foregoing sets forth many, but not all, of the factors that could cause actual
results to differ from Biogen's expectations in any forward-looking statement. Investors should consider
this cautionary statement as well as the risk factors identified in Biogen's most recent annual or quarterly
report and in other reports Biogen has filed with the U.S. Securities and Exchange Commission. Thesestatements speak only as of the date of this news release. Biogen does not undertake any obligation to
publicly update any forward-looking statements.

References
1 Lecanemab Great Britain Summary of Product Characteristics

2 van Dyck, 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 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://doi.org/10.1016/j.mcn.2024.103949.
4 Sehlin, D., et al. Large aggregates are the major soluble Aβ species in AD brain fractionated withdensity gradient ultracentrifugation. PLoS One. 2012;7(2):e32014.
https://doi.org/10.1371/journal.pone.0032014.
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accessed: August 2024.
6 World Health Organization. 2023. Dementia. Available at: https://www.who.int/news-room/factsheets/detail/dementia. Last accessed: August 2024
7 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.
8 Ono, K., Tsuji, M. Protofibrils of Amyloid-β are Important Targets of a Disease-Modifying Approachfor Alzheimer's Disease. International Journal of Molecular Sciences. 2020;21(3):952. doi:
10.3390/ijms21030952. PMID: 32023927; PMCID: PMC7037706.
9 Morris, J.C. The Clinical Dementia Rating (CDR): current version and scoring rules. Neurology.
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accessed: August 2024.
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August 2024.
13 Pharmaceutical Technology. 2024. South Korea’s MFDS approves Eisai-Biogen’s LEQEMBI for
Alzheimer’s. Last accessed: August 2024.
14 Pharmaceutical Technology. 2024. Hong Kong approves Leqembi for Alzheimer’s treatment. Last
accessed: August 2024.
15 BioSpace. 2024. Leqembi approved for the treatment of Alzheimer’s disease in Israel. Last
accessed: August 2024.
16 United Arab Emirates Ministry of Health & Prevention. 2024. Registered Medical Product Directory.
Leqembi. Last accessed: August 2024.

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