FDA Extends Review of Subcutaneous Starting Dose for Lecanemab in Early Alzheimer Disease

The FDA has extended its review of Eisai and Biogen’s supplemental biologics license application (sBLA) for a once-weekly subcutaneous autoinjector starting regimen of lecanemab-irmb (Leqembi Iqlik) in early Alzheimer disease (AD), pushing the Prescription Drug User Fee Act (PDUFA) action date to August 24, 2026.¹

According to the companies, the FDA requested additional information during its ongoing review and classified the submission as a “major amendment,” resulting in a standard 3-month extension to allow time for full evaluation of the updated materials. Importantly, Eisai and Biogen noted that the agency “has not raised any concerns to date regarding the approvability” of the subcutaneous starting-dose regimen.¹

If approved, the expanded indication would allow patients with mild cognitive impairment (MCI) or mild dementia due to AD to initiate treatment directly with a once-weekly subcutaneous autoinjector formulation rather than first receiving biweekly intravenous infusions. The proposed regimen builds on the FDA’s August 2025 approval of Leqembi Iqlik for maintenance dosing, which became the first at-home, self-administered antiamyloid treatment option for AD.²

Lecanemab, an antiamyloid monoclonal antibody targeting soluble and insoluble aggregated amyloid-beta species, is currently approved in more than 50 countries for patients with early-stage AD.¹ The therapy originally gained FDA approval based on findings from the pivotal phase 3 Clarity AD study (NCT03887455), which enrolled 1795 patients with confirmed amyloid pathology and demonstrated slowing of cognitive and functional decline over 18 months.³

The newer subcutaneous autoinjector formulation was developed to reduce treatment burden and improve flexibility for patients and caregivers. Under the currently approved maintenance indication, patients complete an 18-month induction course of intravenous lecanemab at 10 mg/kg every 2 weeks before transitioning to once-weekly 360-mg subcutaneous injections.² The pending sBLA seeks to eliminate the requirement for IV initiation altogether.

In prior analyses from the Clarity AD open-label extension, patients treated with subcutaneous lecanemab achieved pharmacokinetic exposure within accepted bioequivalence ranges while also demonstrating numerically greater amyloid plaque clearance relative to IV dosing.⁴ Previous data presented at the Clinical Trials on Alzheimer’s Disease (CTAD) conference showed approximately 14% greater amyloid reduction after 6 months among patients receiving the subcutaneous formulation.⁴

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Investigators have also explored the formulation’s potential effect on amyloid-related imaging abnormalities (ARIA), a key safety consideration for antiamyloid therapies. In the Clarity AD dataset, ARIA-edema occurred in 12.6% of patients receiving IV lecanemab compared with 16.7% among those on subcutaneous therapy, although interpretation was limited by smaller sample sizes in the SC cohort.²

The shift toward subcutaneous delivery has additionally generated interest because of potential economic and logistical advantages. A 2025 cost-comparison analysis published in Neurology and Therapy estimated that SC administration could save approximately $72,891 to $80,925 per patient over 4 years compared with IV infusion through reductions in treatment costs, administration burden, and caregiver quality-of-life impacts.⁵

“This shift to subcutaneous maintenance dosing is a crucial step toward making Leqembi more accessible for patients, similar to how diabetes and GLP-1 medications are delivered, and represents the first step towards the day when patients can bypass infusions altogether,” Howard Fillit, MD, cofounder and chief science officer of the Alzheimer’s Drug Discovery Foundation, previously said following the SC maintenance approval.

Maria C. Carrillo, PhD, chief science officer and medical affairs lead at the Alzheimer’s Association, also commented at the time of the SC maintenance authorization that the evolving delivery approaches for antiamyloid therapies reflect broader progress in the field. “We are seeing the evolution of amyloid targeting antibody treatments, including improvements in drug delivery and acknowledgment that this class of treatments continues to demonstrate clinical benefit beyond the 18-month clinical trial data,” she said.

The FDA’s review extension comes as the AD treatment landscape continues to evolve rapidly, with increasing focus on earlier intervention, home-based administration models, and therapies capable of reducing infusion-related barriers to access. Eisai and Biogen stated that they remain committed to working closely with regulators to potentially bring the expanded SC initiation option to patients “as quickly as possible.”¹

REFERENCES
1. Update on FDA Priority Review of LEQEMBI® IQLIK™ (lecanemab-irmb) Subcutaneous Injection as a Starting Dose for Early Alzheimer’s Disease. News release. Eisai and Biogen. May 8, 2026. Accessed May 8, 2026
2. FDA approves LEQEMBI® IQLIK™ subcutaneous injection for maintenance dosing for the treatment of early Alzheimer’s disease. News release. Eisai. August 29, 2025. Accessed May 8, 2026.
3. Van Dyck CH, Swanson CJ, Aisen P, et al. Lecanemab in early Alzheimer’s disease. N Engl J Med. 2023;388(1):9-21. doi:10.1056/NEJMoa2212948
4. Irizarry M, Li D, Dhadda S, Hersch S, Reyderman L, Kramer L. Preliminary update on lecanemab safety in Clarity AD open-label extension, including subcutaneous formulation. Presented at: Clinical Trials on Alzheimer’s Disease Conference; October 24-27, 2023; Boston, MA.
5. Monfared AAT, Barrows S, Fox L, et al. Societal costs and efficiency of subcutaneous versus intravenous lecanemab in early Alzheimer’s disease: a U.S. cost comparison model. Neurol Ther. 2025. Published online July 4, 2025. doi:10.1007/s40120-025-00790-2