Biogen and Eisai Fall Behind on Leqembi’s Subcutaneous BLA for Alzheimer’s

MRI Scans_iStock, Nur Ceren Demir

Pictured: Magnetic resonance imaging scans of the brain/iStock, Nur Ceren Demir

Biogen and Eisai on Monday announced that they have missed their March 2024 target of filling a Biologics License Application for a subcutaneous formulation of their Alzheimer’s disease therapy Leqembi (lecanemab), being proposed as a weekly maintenance regimen.

The companies initially planned to start a rolling Biologics License Application (BLA) last month under the existing Fast Track and Breakthrough Therapy designations for Leqembi. However, the regulator informed Eisai that they would need a Fast Track designation specifically for the subcutaneous formulation before they can launch their rolling application, according to Monday’s announcement.

Eisai has since submitted a request for the Fast Track designation and is set to receive a verdict within 60 days of its filing. If granted, the partners will launch their rolling BLA.

The companies also announced that they have filed a supplemental BLA (sBLA) proposing a monthly intravenous maintenance dosing schedule for Leqembi. If approved, this maintenance regimen will be available for patients who complete the biweekly intravenous initiation phase, though the exact duration for this is still under discussion with the FDA.

Currently, Leqembi is approved as an intravenous infusion given over approximately one hour, every two weeks, according to its label.

Leqembi’s monthly infusion schedule is designed to sustain effective drug levels in the body, enough to keep the toxic protofibrils at bay. In patients with Alzheimer’s disease, these protofibrils can still trigger neuronal damage and brain injury even amyloid-beta plaques have been removed, according to the companies.

Biogen and Leqembi are supporting the sBLA with modelling data from results of the Phase IIb Study 201 and its open-label extension phase, as well as the Phase III Clarity AD study and its open-label extension.

Leqembi is a humanized IgG1 monoclonal antibody that works by targeting aggregated soluble and insoluble amyloid-beta plaques. This mode of action helps clear these clumps from the brain, which would otherwise interfere with cognition and give rise to the hallmark symptoms of Alzheimer’s disease.

Based on data from Study 201, which showed that Leqembi could decrease the levels of amyloid-beta plaques in the brain, the FDA granted Leqembi accelerated approval in January 2023. In July 2023, the regulator converted its nod into a full approval, making Leqembi the first anti-amyloid antibody to earn this distinction.

Leqembi’s traditional approval was based on the Clarity AD, which demonstrated that the biomarker effects observed in Study 201 translated to clinical benefits. Patients treated with Leqembi saw a 27% reduction in clinical decline versus placebo, as defined by the Clinical Dementia Rating-Sum of Boxes test.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at or

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