TOKYO and CAMBRIDGE, Mass., Sept. 24, 2025 - (JCN 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 Therapeutic Goods Administration (TGA)of Australia has approved the humanized anti-soluble aggregated amyloid-beta (Aβ) monoclonal antibody “LEQEMBI®” (brand name, generic name: lecanemab) for mild cognitive impairment (MCI) or mild dementia due to Alzheimer's disease (AD) (collectively referred to as early AD) in adults who are either ApoEε4* non-carriers or heterozygous carriers.

In response to February 2025 TGA decision not to approve lecanemab as a treatment for people with early AD, in March 2025, Eisai requested a review by the Administrative Review Tribunal. As a result of discussions during this process, the TGA and Eisai reached an agreement that led to the approval of LEQEMBI. 

In Australia, the number of people living with dementia was estimated to be approximately 425,000 in 2024, and is reported to increase to nearly 1,100,000 by 2065.1 AD is considered the most common cause of dementia, typically accounting for 60-70% of cases.2 AD is a progressive, relentless disease with amyloid beta (Aβ) and tau as hallmarks that is caused by a continuous underlying neurotoxic process that begins before amyloid plaque removal and continues afterward.3,4,5 Only LEQEMBI fights AD in two ways– targeting both the toxic protofibrils** and amyloid plaque 2, which can impact tau downstream. 

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.

* Apolipoprotein E is a protein involved in the metabolism of fats 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.6,7

** 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 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.4

MEDIA CONTACTS

Eisai Co., Ltd.
Public Relations Department
+81 (0)3-3817-5120

Eisai Europe, Ltd.
(UK, Europe, Australia, New Zealand and Russia)
EMEA Communications Department
+44 (0) 7739 600678
EMEA-comms@eisai.net

Eisai Inc. (U.S.)
Libby Holman
+ 1-201-753-1945
Libby_Holman@eisai.com

Biogen Inc.
Madeleine Shin
+ 1-781-464-3260
public.affairs@biogen.com

INVESTOR CONTACTS

Eisai Co., Ltd.
Investor Relations Department
+81 (0) 3-3817-5122

Biogen Inc.
Tim Power
+ 1-781-464-2442
IR@biogen.com

For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202566pdf.pdf

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