Eisai and Biogen are advancing efforts to enhance the administration of their Alzheimer's disease therapy, Leqembi (lecanemab), with a subcutaneous formulation delivered via autoinjector. The companies have completed their rolling biologics license application (BLA) in the US, seeking approval for this new formulation, which promises to reduce the burden of treatment for patients.
The subcutaneous formulation of Leqembi is designed for once-weekly administration via autoinjector, following an initial biweekly intravenous induction course. This approach aims to eliminate the need for hour-long clinic visits required by the current intravenous version. If approved, patients could administer the treatment at home or in medical facilities, potentially accelerating the adoption of Leqembi, which has seen relatively slow uptake compared to expectations.
The FDA has granted fast-track status to the subcutaneous Leqembi application. However, the agency has not yet indicated a timeline for completing its review. Eisai and Biogen initially planned to leverage the existing fast-track designation for intravenous Leqembi but were advised to submit a separate application for the subcutaneous formulation.
Strategic Implications and Competition
The availability of a less burdensome subcutaneous formulation could provide a competitive edge against rivals such as Eli Lilly's recently approved Kisunla (donanemab). While Lilly is developing subcutaneous forms of its follow-up amyloid drug remternetug, it has not yet announced plans for a subcutaneous version of Kisunla. Biogen's CEO, Chris Viehbacher, suggested that extending the use of the subcutaneous injector into the induction phase of treatment could be a "game changer," with potential approval for that indication targeted in the first quarter of 2026.
Label Extension for Maintenance Dosing
Eisai and Biogen have also filed to extend Leqembi's label to include a new maintenance dosing regimen. This regimen would reduce the frequency of intravenous infusions to once per month, further streamlining the treatment process.
Market Performance and Regulatory Landscape
Leqembi is currently approved for treating Alzheimer's patients with mild cognitive impairment or mild dementia in several regions, including the US, Japan, China, South Korea, Hong Kong, Israel, UAE, and GB. However, recent regulatory decisions in the EU and Australia have not favored approval, with the EU currently re-examining the drug. Biogen reported Leqembi sales of $67 million in the third quarter, including $39 million in the US, which fell short of expectations. The company anticipates that an expanded salesforce and the potential launch of monthly IV and subcutaneous doses for maintenance next year could boost sales.
