FDA Approves Monthly Maintenance Dosing for Biogen and Eisai's Alzheimer's Drug Leqembi

The U.S. Food and Drug Administration (FDA) has granted approval for a monthly maintenance dosing regimen of Leqembi (lecanemab), the Alzheimer's treatment developed by Biogen and Eisai. This new dosing schedule, announced on Sunday, offers patients a more convenient option following the initial 18-month treatment period and could potentially boost the drug's underwhelming sales performance.

New Dosing Regimen and Its Implications

Leqembi, an anti-amyloid therapy indicated for patients with mild Alzheimer's disease or mild cognitive impairment, was initially approved with a bi-weekly intravenous infusion schedule. The newly approved regimen allows patients to transition to a monthly 10 mg/kg dose after the first 18 months of treatment.

The approval was based on modeling data from Phase II and Phase III clinical trials, suggesting that the monthly maintenance schedule effectively sustains the clinical and biomarker benefits of treatment. Biogen and Eisai emphasized the importance of ongoing treatment, citing evidence that discontinuation leads to a reaccumulation of amyloid plaques and other disease biomarkers, with clinical decline reverting to placebo levels.

Dr. Michael Irizarry, Eisai's Senior Vice President of Clinical Research, stated, "Alzheimer's disease progression does not stop after plaque clearance," underscoring the need for continued treatment to maintain benefits and slow disease progression.

Market Challenges and Financial Outlook

Despite its groundbreaking potential, Leqembi has faced significant market challenges since its launch. In November 2024, Eisai downgraded its fiscal year 2024 sales forecast for Leqembi from $370 million to $280 million, reflecting slower-than-expected uptake.

The approval of the monthly maintenance regimen comes at a crucial time for Biogen and Eisai, as they grapple with disappointing sales figures and growing investor concerns. At the 2025 J.P. Morgan Healthcare Conference, Biogen reaffirmed its commitment to Leqembi and the broader Alzheimer's space, despite the drug's struggles with reimbursement barriers and the need for increased provider awareness.

Regulatory Challenges and Safety Concerns

Leqembi's journey has not been without controversy. In July 2024, the European Union's health regulatory agency initially issued a negative opinion on the drug, citing concerns that its benefits did not outweigh the risks of serious side effects, particularly amyloid-related imaging abnormalities. However, following a re-examination requested by Eisai, the agency later reversed its decision and issued a positive opinion.

As Biogen and Eisai navigate these challenges, the approval of the monthly maintenance dosing regimen represents a potential turning point for Leqembi. The companies hope that the more convenient dosing schedule will improve patient adherence and ultimately drive increased adoption of this innovative Alzheimer's treatment.