TOKYO and CAMBRIDGE, Mass., Nov 14, 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 humanized anti- soluble aggregated amyloid-beta (Aβ) monoclonal antibody “LEQEMBI®” (generic name: lecanemab) has been approved for once every four weeks intravenous (IV) maintenance dosing by the Medicines and Healthcare products Regulatory Agency (MHRA) in the United Kingdom.
In August 2024, LEQEMBI was approved 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 (ApoE ε4)* heterozygotes or non-carriers in the United Kingdom. With this latest approval for IV maintenance dosing, after 18 months of a dosing regimen of 10 mg/kg once every two weeks patients may be transitioned to the maintenance dosing regimen of 10 mg/kg once every four weeks, or the regimen of 10 mg/kg once every two weeks may be continued.
AD is a progressive, relentless disease characterized by formation of protein deposits known as plaques made of amyloid-beta aggregates and neurofibrillary tangles made of tau protein in the brains of people living with AD. It is caused by a continuous underlying neurotoxic process that begins before amyloid plaque accumulation and continues after plaque removal.1,2 The data show that amyloid-beta protofibrils and tau tangles play roles in the neurodegeneration process,2,3 and only LEQEMBI fights AD in two ways – targeting both amyloid plaque and protofibrils**, which can impact tau downstream.
Due to the reaccumulation of AD biomarkers and return to placebo rate of decline after therapy is stopped,3-5 continuing maintenance treatment after the initial 18-month therapy is essential to slow the progression of AD and extend the therapeutic benefits, helping patients maintain who they are for longer.
In the United Kingdom, it is estimated that 982,000 people are living with dementia,6 and AD is the cause in 60-70% of people with dementia.7 These numbers are expected to rise, as the population ages.6, 7
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 lipid 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).8
** Protofibrils are thought to be the most toxic Aβ species that contribute to brain damage in AD and play a major role in the cognitive decline of this progressive and devastating disease. Protofibrils can cause neuronal and synaptic damage in the brain, which can subsequently adversely affect cognitive function through multiple mechanisms.3 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 slowing the progression of AD.4
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Eisai
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Eisai Inc. (U.S.)
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Biogen Inc.
Madeleine Shin
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public.affairs@biogen.com
INVESTOR CONTACTS
Eisai Co., Ltd.
Investor Relations Department
TEL: +81 (0)3-3817-5122
Biogen Inc.
Tim Power
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IR@biogen.com
About LEQEMBI (generic name: lecanemab)
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 51 countries and is under regulatory review in 9 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 the United Kingdom, the U.S, China and others, and applications have been filed in 4 countries and regions.
LEQEMBI's approvals in these countries were 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 statistically significant results. The primary endpoint was the global cognitive and functional scale, Clinical Dementia Rating Sum of Boxes (CDR-SB).1 The U.S. FDA approved Eisai’s Biologics License Application (BLA) for subcutaneous maintenance dosing with LEQEMBI IQLIK in August 2025. In September 2025, the rolling sBLA application to the U.S. FDA for the subcutaneous initiation dosing with LEQEMBI IQLIK was also initiated.
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.
For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202579pdf.pdf