Eisai Co. Ltd. and Biogen Inc. announced that humanized anti- soluble aggregated amyloid-beta (Aß) monoclonal antibody LEQEMBI® Intravenous Infusion (200 mg, 500mg, lecanemab) has been approved in Japan as a treatment for slowing progression of mild cognitive impairment (MCI) and mild dementia due to Alzheimer?s disease (AD). LEQEMBI is a humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril*) and insoluble forms of Aß.

LEQEMBI is the first and only approved treatment shown to reduce the rate of disease progression and to slow cognitive and functional decline by selectively binding to and eliminating the most toxic Aß aggregates (protofibrils) that contribute to neurotoxicity in AD. In Japan, an application for marketing approval was filed and was designated for priority review in January 2023. Japan is the second country to grant approval, following the traditional approval in the U.S. in July 2023.

LEQEMBI?s approval is based on Phase 3 data from Eisai?s large, global Clarity AD clinical trial, in which LEQEMBI met its primary endpoint and all key secondary endpoints with statistically significant results and confirmed the clinical benefit of LEQEMBI. The primary endpoint was the global cognitive and functional scale, Clinical Dementia Rating Sum of Boxes (CDR-SB). In the Clarity AD clinical trial, treatment with LEQEMBI reduced clinical decline on CDR-SB by 27% at 18 months compared to placebo.

In addition, the secondary endpoint from the AD Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment (ADCS MCI-ADL), which measures information provided by people caring for patients with AD, noted a statistically significant benefit of 37% compared to placebo. The ADCS MCI-ADL assesses the ability of patients to function independently, including being able to dress, feed themselves and participate in community activities. The most common adverse events (>10%) in the LEQEMBI group were infusion reactions, ARIA-H (combined cerebral microhemorrhages, cerebral macrohemorrhages, and superficial siderosis), ARIA-E (edema/effusion), headache, and fall.

Full results of the Clarity AD study were presented at the Clinical Trials on Alzheimer's Disease (CTAD) 2022 conference and simultaneously published in the peer-reviewed medical journal The New England Journal of Medicine on November 29, 2022. Eisai will conduct a post-marketing special use results survey (all-case surveillance) in all patients who are administered LEQEMBI until data from a certain number of patients are accumulated after market launch, in accordance with an approval condition imposed by the Ministry of Health, Labour and Welfare. In addition, the appropriate use of LEQEMBI will be promoted in accordance with the package insert and training materials will be developed for healthcare professionals to assist the management and monitoring of amyloid-related imaging abnormalities (ARIA).

Eisai serves as the lead of LEQEMBI development and regulatory submissions globally with both Eisai and Biogen co-commercializing and co-promoting the product and Eisai having final decision-making authority. In Japan, Eisai and Biogen Japan will co-promote LEQEMBI, with Eisai distributing the product as the Marketing Authorization Holder.