Eisai Co Ltd (OTC:ESALY) (OTC:ESALF) and Biogen Inc (NASDAQ:BIIB) announced that humanized anti-soluble aggregated amyloid-beta (Aβ) monoclonal antibody Leqembi Intravenous Infusion (200 mg, 500mg, lecanemab) has been approved in Japan as a treatment for slowing progression of mild cognitive impairment 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 Aβ. 

Leqembi is the first and only approved treatment shown to reduce the disease progression rate and slow cognitive and functional decline by selectively binding to and eliminating the most toxic Aβ aggregates (protofibrils) that contribute to neurotoxicity in AD. 

Leqembi's approval is based on Phase 3 data from the 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.

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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, which measures information provided by people caring for patients with AD, noted a statistically significant benefit of 37% compared to placebo. 

In July, the FDA granted traditional approval to Leqembi following a confirmatory trial that verified its clinical benefit.

Eisai will conduct a post-marketing special use results survey (all-case surveillance) in all patients administered Leqembi until data from a certain number of patients are accumulated after the market launch.

Price Action: BIIB shares are down 2.19% at $252.03 on the last check Monday.