Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced that the U.S. Food and Drug Administration (FDA) has approved the Supplemental Biologics License Application (sBLA) for once every four weeks lecanemab-irmb (U.S. brand name: LEQEMBI^®) intravenous (IV) maintenance dosing. 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) in the U.S. After 18 months of once every two weeks initiation phase, a transition to the maintenance dosing regimen of 10 mg/kg once every four weeks may be considered or the regimen of 10 mg/kg once every two weeks may be continued.

The sBLA is based on modeling of observed data from the Phase 2 study (Study 201) and its long-term extension (LTE) as well as the Clarity AD study (Study 301) and its LTE study. Modeling simulations predict that transitioning to once every four weeks maintenance dosing after 18 months of once every two weeks treatment will maintain clinical and biomarker benefits of therapy. AD is a progressive, relentless disease caused by a continuous underlying neurotoxic process that begins before and continues after plaque removal.^1,2,3 Only LEQEMBI works to fight AD in two ways: continuously clearing protofibrils and rapidly clearing plaque. This is important because with continuous administration, LEQEMBI clears highly toxic protofibrils* which can continue to cause neuronal injury even after the amyloid-beta (Aβ) plaque has been cleared from the brain.

LEQEMBI is approved in the U.S., Japan, China, South Korea, Hong Kong, Israel, UAE, Great Britain, Mexico and Macau. In November 2024, the treatment received a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) recommending approval. Eisai has submitted applications for approval of lecanemab in 17 countries and regions. Additionally, the FDA accepted Eisai’s Supplemental Biologics License (BLA) for the LEQEMBI subcutaneous autoinjector for weekly maintenance dosing in January 2025 and set a PDUFA action date for August 31, 2025.

Eisai serves as the lead for lecanemab’s development and regulatory submissions globally with both Eisai and Biogen co-commercializing and co-promoting the product and Eisai having final decision-making authority.

*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.⁵ 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.