Confirmatory Phase 3 Clarity AD data to be evaluated by FDA in determining whether to convert accelerated approval of LEQEMBI to a traditional approval

Priority Review accelerates FDA review time with a Prescription Drug User Fee Act (PDUFA) target action on July 6, 2023

TOKYO and CAMBRIDGE, Mass., March 6, 2023 ¨C Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced today that the U.S. Food and Drug Administration (FDA) has accepted Eisai¡¯s supplemental Biologics License Application (sBLA) for LEQEMBI? (lecanemab-irmb) 100 mg/mL injection for intravenous use, supporting the conversion of the accelerated approval of LEQEMBI to a traditional approval. The LEQEMBI application has been granted Priority Review, with a Prescription Drug User Fee Act (PDUFA) action date of July 6, 2023. The FDA is currently planning to hold an Advisory Committee to discuss this application but has not yet publicly announced the date of the meeting.

LEQEMBI is a humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibrils*) and insoluble forms of amyloid beta (A¦Â), approved under the Accelerated Approval Pathway for the treatment of Alzheimer’s Disease (AD) on January 6, 2023. Treatment with LEQEMBI should only be initiated in patients with the mild cognitive impairment or mild dementia stage of disease and confirmed presence of A¦Â pathology. On the same day that LEQEMBI received its accelerated approval, Eisai submitted the sBLA to the FDA for approval under the traditional pathway.

The sBLA is based on the findings from Eisai¡¯s recently published large, global confirmatory Phase 3 clinical trial, Clarity AD. LEQEMBI met the primary endpoint and all key secondary endpoints with highly statistically significant results. In November 2022, results of the Clarity AD study were presented at the Clinical Trials on Alzheimer’s Disease (CTAD) conference and simultaneously published in the peer-reviewed medical journal, The New England Journal of Medicine.

LEQEMBI was approved under accelerated approval in the U.S. and ?was launched in the U.S. on January 18, 2023. The accelerated approval was based on Phase 2 data that demonstrated that LEQEMBI reduced the accumulation of A¦Â plaque in the brain, a defining feature of AD, and its continued approval may be contingent upon verification of LEQEMBI¡¯s clinical benefit in a confirmatory trial. The FDA has determined that the results of Clarity AD can serve as the confirmatory study to verify the clinical benefit of lecanemab.

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.