TOKYO and CAMBRIDGE, Mass., May 8, 2026
Eisai Co., Ltd. and Biogen Inc. announced that the U.S. Food and Drug Administration (FDA) has extended the review period for the supplemental Biologics License Application (sBLA) of LEQEMBI® IQLIK™ (lecanemab-irmb) subcutaneous injection as a starting dose therapy for patients with early Alzheimer’s disease. The FDA extended the Prescription Drug User Fee Act (PDUFA) target action date by three months to August 24, 2026, following the agency’s request for additional information during the ongoing review process.
The companies emphasized that the FDA has not raised concerns regarding the approvability of the treatment and stated that the additional submission constituted a “major amendment” requiring more time for comprehensive regulatory evaluation. Eisai and Biogen noted that the updated filing includes extensive clinical data supporting the use of a once-weekly subcutaneous formulation designed to provide greater flexibility for Alzheimer’s patients and healthcare providers.
Subcutaneous LEQEMBI Could Expand Alzheimer’s Treatment Access
The subcutaneous version of LEQEMBI represents an important advancement in the evolving Alzheimer’s disease treatment landscape. The therapy is intended for patients with mild cognitive impairment or mild dementia stage Alzheimer’s disease, the same patient population studied in clinical trials. Researchers believe the injectable formulation could simplify treatment administration compared with traditional intravenous infusions while potentially improving convenience and access for patients and caregivers.
Eisai and Biogen highlighted that LEQEMBI has already been approved by more than 50 regulatory authorities worldwide, demonstrating broad international confidence in the therapy as a treatment option for early Alzheimer’s disease. The companies stated that the FDA previously approved the subcutaneous maintenance dosing regimen in August 2025, and the latest review focuses specifically on expanding use as an initial starting-dose therapy.
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The companies added that ongoing discussions with regulators are expected to continue throughout the review period as they work toward delivering broader treatment flexibility for anti-amyloid therapies targeting Alzheimer’s disease progression.
Safety Monitoring Remains Central to FDA Review
The FDA update also reinforced the importance of monitoring safety risks associated with anti-amyloid monoclonal antibodies, particularly Amyloid-Related Imaging Abnormalities (ARIA). According to the prescribing information included in the announcement, LEQEMBI may cause ARIA with edema or hemosiderin deposition, which in rare cases can become serious or life-threatening.
Clinical trial data showed that symptomatic ARIA occurred in approximately 3% of patients, while ARIA overall was observed in 21% of LEQEMBI-treated patients compared with 9% in placebo groups. The risk appeared significantly higher in patients carrying the ApoE ε4 homozygous genotype, a known genetic risk factor associated with Alzheimer’s disease and cerebral amyloid angiopathy.
Regulators and clinicians continue to emphasize the importance of MRI monitoring during treatment, especially during the early stages of therapy. Despite the known safety considerations, experts believe anti-amyloid therapies such as LEQEMBI remain among the most significant scientific advances in Alzheimer’s treatment in recent years because they directly target amyloid-beta pathology linked to disease progression.
Alzheimer’s Drug Development Continues Accelerating
The extension of the FDA review comes amid rapidly increasing global investment in Alzheimer’s disease therapeutics, biomarker-driven neurology research, and neurodegenerative disease innovation. LEQEMBI, developed through collaborations between Eisai, Biogen, and BioArctic, is currently approved in multiple global markets including the United States, Europe, Japan, China, South Korea, and Saudi Arabia.
Industry analysts believe the availability of both intravenous and subcutaneous formulations could significantly influence the future commercial landscape of Alzheimer’s treatment by improving administration flexibility and supporting broader healthcare adoption. Researchers continue to study lecanemab across additional clinical programs designed to evaluate its role in preclinical Alzheimer’s disease and other neurodegenerative conditions.
Source: Eisai, Biogen press release
