Stockholm, Sweden, November 13, 2026
Eisai Co., Ltd. and Biogen Inc., in collaboration with BioArctic AB, have announced the launch of LEQEMBI® Pen (lecanemab) in Japan, introducing a once-weekly subcutaneous treatment option for patients with early Alzheimer’s disease. The new formulation uses an autoinjector designed to enable administration at home following appropriate training and under physician supervision. Japan is the second country, after the United States, to launch the subcutaneous formulation of LEQEMBI. The product received approval in Japan on September 16, 2026, and its inclusion in the country’s National Health Insurance (NHI) Drug Price List has enabled its commercial availability. The launch provides an alternative to the existing intravenous (IV) formulation, which is administered every two weeks at a medical facility. The new option is expected to offer greater flexibility for patients and caregivers while potentially reducing the practical burden associated with repeated hospital or clinic visits.
LEQEMBI Pen Introduces Once-Weekly At-Home Treatment
LEQEMBI Pen is a subcutaneous formulation of lecanemab, a humanized immunoglobulin G1 (IgG1) monoclonal antibody developed to target aggregated forms of amyloid-beta (Aβ), including soluble protofibrils and insoluble amyloid plaques. The newly launched formulation is administered using an autoinjector, with a recommended dose of 500 mg once weekly through two pens. This provides an alternative route of administration to the existing IV treatment schedule of every two weeks in a healthcare facility. Following appropriate education and training, patients may administer the treatment themselves or receive assistance from a family member or care partner. Such administration must take place under the management and guidance of a physician. The subcutaneous injection takes approximately 15 seconds per pen, offering a shorter administration process compared with an IV infusion. The availability of an at-home option may help patients incorporate treatment into their daily routines and reduce travel requirements for regular medical appointments. It may also provide greater flexibility for patients who need to travel or have difficulty attending frequent clinic visits. However, the new formulation does not eliminate the need for regular medical supervision, treatment assessments or safety monitoring.
Lecanemab Targets Amyloid-Beta in Early Alzheimer’s Disease
Lecanemab is designed to bind to aggregated soluble and insoluble forms of amyloid-beta, including protofibrils, which are believed to contribute to neuronal and synaptic damage in Alzheimer’s disease. By targeting these amyloid-beta aggregates, the treatment is intended to reduce amyloid pathology and slow the progression of cognitive and functional impairment in eligible patients with early Alzheimer’s disease. The medicine is indicated in Japan for slowing the progression of mild cognitive impairment (MCI) due to Alzheimer’s disease and mild dementia due to Alzheimer’s disease. The clinical development program supporting lecanemab includes the Phase 3 Clarity AD study, which evaluated the treatment in people with early Alzheimer’s disease. The Japanese approval of the subcutaneous formulation was supported by integrated data from the 18-month core study of Clarity AD, together with data from subcutaneous administration sub-studies in its long-term extension. The formulation provides a different way to administer the same active medicine rather than introducing a new drug or a new therapeutic mechanism. Importantly, LEQEMBI is intended to slow disease progression and is not a cure for Alzheimer’s disease. Patients and caregivers should discuss the expected benefits, risks and suitability of treatment with their healthcare professionals.
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Eisai and Biogen Expand Global Alzheimer’s Treatment Access
The Japan launch represents another milestone in the global commercialization strategy of Eisai and Biogen, which have collaborated on the development and commercialization of Alzheimer’s disease treatments since 2014. Eisai leads the global clinical development, regulatory submissions and commercialization strategy for lecanemab, while the two companies jointly commercialize and promote the treatment. BioArctic, which originally developed the antibody, has maintained a long-term research and development collaboration with Eisai since 2005. LEQEMBI has received marketing authorization in multiple countries and regions, and the introduction of the subcutaneous formulation is expanding the available administration options. The treatment is also associated with important safety considerations, particularly amyloid-related imaging abnormalities (ARIA), which can include brain swelling and small areas of bleeding. As with IV administration, patients receiving the subcutaneous formulation require brain magnetic resonance imaging (MRI) before starting treatment and at specified intervals afterward to monitor for ARIA. Appropriate patient selection, medical supervision and adherence to monitoring requirements remain essential. The launch of LEQEMBI Pen in Japan highlights the pharmaceutical industry’s continuing efforts to improve treatment delivery for neurodegenerative diseases. By offering a once-weekly at-home administration option, Eisai and Biogen aim to provide additional flexibility for eligible patients while maintaining the clinical oversight required for anti-amyloid therapy.
Source: Eisai, Biogen, BioArctic press release
