Eisai Completes Rolling Submission to US FDA for LEQEMBI(R) IQLIK(TM) (lecanemabirmb) Supplemental Biologics License Application as a Subcutaneous Starting Dose for the Treatment of Early Alzheimer’s Disease Under Fast Track Status

TOKYO and CAMBRIDGE, Mass., Nov. 26, 2025 – (JCN Newswire via SeaPRwire.com) – Eisai Co., Ltd. (Headquarters: Tokyo, CEO: HaruoNaito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced today that Eisai has completed the rolling submission of the Supplemental Biologics License Application (sBLA) to the U.S. Food and Drug Administration (FDA) for lecanemab-irmb (U.S. brand name: LEQEMBI®) subcutaneous autoinjector(SC-AI), LEQEMBI IQLIK, as a weekly starting dose after the FDA granted Fast Track Status. LEQEMBI is indicated for the treatment of Alzheimer’s disease (AD) in patients with Mild Cognitive Impairment(MCI) or mild dementia stage of disease (collectively referred to as early AD). Upon acceptance of the sBLA, the FDA will set a Prescription Drug User Fee Act (PDUFA) action date (target date for review completion).

The sBLA is supported by data evaluating subcutaneous (SC) administration of lecanemab across arange of doses and as part of sub-studies within the Phase 3 Clarity AD open-label extension (OLE)following the 18-month core study in individuals with early AD. Data show that once-weekly administration of the 500 mg of SC-AI achieved equivalent exposure to once every two weeks intravenous (IV) administration and similar clinical and biomarker benefits. Subcutaneous administration demonstrated a safety profile similar to IV administration, with less than 2% incidence ofsystemic injection/infusion-related reactions.

Should the FDA approve the LEQEMBI IQLIK 500 mg SC dosing regimen (two 250 mg injections), the autoinjector could be used to administer a once- weekly starting dose, as an alternative to the current bi-weekly (every two weeks) intravenous (IV) dosing. This would enable patients and care partners to choose SC administration at home for both initial treatment and the currently approved maintenance therapy, offering the option of SC or IV administration throughout the entire treatment journey. The injection time for each LEQEMBI IQLIK autoinjector takes approximately 15 seconds. The SC formulation also has the potential to reduce healthcare resources associated with IV dosing, such as preparation for infusion and nurse monitoring, while streamlining the overall AD treatment pathway.

AD is a progressive, relentless disease, with amyloid beta (Aβ) and tau as hallmarks, that is caused by a continuous underlying neurotoxic process driven by protofibrils* that begins before amyloid plaqueaccumulation and continues after plaque removal.1,2,3 Only LEQEMBI fights AD in two ways – targetingboth protofibrils and amyloid plaque, which can impact tau downstream.

LEQEMBI is currently approved in 51 countries and regions and is under regulatory review in 9 countries. In August 2025, the US FDA approved LEQEMBI IQLIK 360 mg for weekly subcutaneous maintenance dosing after 18 months of IV treatment every two weeks.

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.

For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202581pdf.pdf