Tokyo and Cambridge, Mass. — November 28, 2025 — Leads & Copy — Eisai Co., Ltd. and Biogen Inc. have filed a new drug application with Japan’s Pharmaceuticals and Medical Devices Agency (PMDA) seeking approval for a subcutaneous formulation (SC-AI) of LEQEMBI® (lecanemab). The application pertains to a subcutaneous autoinjector (SC-AI) as a new route of administration for the drug.
The application is based on data from multiple subcutaneous (SC) administration sub-studies of lecanemab, which were conducted as part of the Phase 3 Clarity AD open-label extension (OLE). The studies followed an 18-month core study involving individuals with Mild Cognitive Impairment (MCI) due to Alzheimer’s disease (AD) or mild stage of AD dementia (collectively referred to as early AD). Weekly administration of SC-AI 500mg resulted in equivalent exposure to intravenous (IV) administration every two weeks and similar clinical and biomarker benefits. The subcutaneous administration demonstrated a safety profile similar to IV administration, with less than 2% incidence of systemic injection/infusion-related reactions.
If approved, the SC-AI of 500 mg (two 250 mg injections) could be used to administer a once-weekly dose at home from the start of treatment. This would serve as an alternative to the current IV administration every two weeks dose in a hospital setting. Each autoinjector (250mg injection) takes approximately 15 seconds to inject. The potential approval of SC-AI would expand the option for patients and care partners to receive LEQEMBI treatment at home.
The SC formulation also has the potential to reduce healthcare resources associated with IV dosing, including preparation for infusion and nurse monitoring, while streamlining the overall AD treatment care pathway. LEQEMBI targets both protofibrils and amyloid plaque, impacting tau downstream.
LEQEMBI is currently approved in 51 countries and regions, with regulatory review underway in nine others.
Eisai serves as the lead for lecanemab’s development and regulatory submissions globally. Eisai and Biogen co-commercialize and co-promote the product, with Eisai retaining final decision-making authority.
Protofibrils are considered the most toxic form of Aβ and believed to contribute to brain injury that occurs with AD, having a primary role in the cognitive decline associated with this progressive condition. They 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. The reduction of protofibrils may prevent the progression of AD by reducing damage to neurons in the brain and cognitive dysfunction.
Eisai Co., Ltd. Media Contacts:
Public Relations Department
TEL: +81 (0)3-3817-5120
Eisai Europe, Ltd. Media Contact:
EMEA Communications Department
+44 (0) 797 487 9419
Emea-comms@eisai.net
Eisai Inc. (U.S.) Media Contact:
Libby Holman
+1-201-753-1945
Libby_Holman@Eisai.com
Biogen Inc. Media Contact:
Madeleine Shin
+1-781-464-3260
public.affairs@biogen.com
Eisai Co., Ltd. Investor Relations Department:
TEL: +81 (0) 3-3817-5122
Biogen Inc. Investor Contact:
Tim Power
+ 1-781-464-2442
IR@biogen.com
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 regions including Japan, the United States, Europe, China, South Korea, Taiwan and Saudi Arabia, and is under regulatory review in 9 countries. It received manufacturing and marketing approval in Japan in September 2023 to treat slowing progression of mild cognitive impairment (MCI) and mild dementia due to Alzheimer’s disease (AD).
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. It 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.
Eisai and Biogen have been collaborating on the joint development and commercialization of AD treatments since 2014. Since 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 in December 2007. The development and commercialization agreement on the antibody lecanemab back-up was signed in May 2015.
Eisai’s Corporate Concept is “to give first thought to patients and people in the daily living domain, and to increase the benefits that health care provides.” Under this Concept (also known as human health care (hhc) Concept), we aim to effectively achieve social good in the form of relieving anxiety over health and reducing health disparities. With a global network of R&D facilities, manufacturing sites and marketing subsidiaries, we strive to create and deliver innovative products to target diseases with high unmet medical needs, with a particular focus in our strategic areas of Neurology and Oncology.
For more information about Eisai, please visit www.eisai.com.
Founded in 1978, Biogen is a leading biotechnology company that pioneers innovative science to deliver new medicines to transform patient’s lives and to create value for shareholders and our communities. We apply deep understanding of human biology and leverage different modalities to advance first-in-class treatments or therapies that deliver superior outcomes. Our approach is to take bold risks, balanced with return on investment to deliver long-term growth.
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This news release contains forward-looking statements, including about the potential clinical effects of lecanemab; the potential benefits, safety and efficacy of lecanemab; potential regulatory discussions, submissions and approvals and the timing thereof including for LEQEMBI (lecanemab) subcutaneous autoinjector (SC-AI); the potential to streamline the Alzheimer’s disease treatment pathway; the anticipated benefits and potential of Biogen’s collaboration arrangements with Eisai; the potential of Biogen’s commercial business and pipeline programs, including lecanemab; and risks and uncertainties associated with drug development and commercialization. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “forecast,” “goal,” “guidance,” “hope,” “intend,” “may,” “objective,” “outlook,” “plan,” “possible,” “potential,” “predict,” “project,” “prospect,” “should,” “target,” “will,” “would” or the negative of these words or other words and terms of similar meaning. Drug development and commercialization involve a high degree of risk, and only a small number of research and development programs result in commercialization of a product. Results in early-stage clinical trials may not be indicative of full results or results from later stage or larger scale clinical trials and do not ensure regulatory approval. You should not place undue reliance on these statements. Given their forward-looking nature, these statements involve substantial risks and uncertainties that may be based on inaccurate assumptions and could cause actual results to differ materially from those reflected in such statements.
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References
Amin L, Harris DA. Aβ 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-β 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.
Hampel H, Hardy J, Blennow K, et al. The amyloid pathway in Alzheimer’s disease. Mol Psychiatry. 2021;26(10):5481-5503.
Source: Eisai Co., Ltd.
