Eisai Submits sBLA for Weekly Subcutaneous Lecanemab as Starting Dose

According to a new announcement, Eisai and Biogen have begun a rolling submission to the FDA for its subcutaneous autoinjector formulation (SC-AI) of lecanemab-irmb (Leqembi) that would introduce a once-weekly starting dose for patients with early Alzheimer disease (AD).¹

If approved by the FDA, the Leqembi Iqlik 500 mg subcutaneous regimen–which comes in two 250 mg injections–would allow for a once-weekly starting dose as an alternative to the current biweekly intravenous (IV) dosing. This option would give patients and caregivers greater flexibility, enabling treatment to begin and continue at home while offering a choice between IV and subcutaneous administration.

Thus far, Leqembi Iqlik has gained fast track status from the FDA, with a decision expected to come sometime in the early Spring of 2026. The latest supplemental biologics license application (sBLA) comes days after the FDA approved the SC-AI formulation of lecanemab, making it the first-ever at-home, self-administered option for ongoing AD treatment.²

The anti-amyloid treatment, indicated for patients with mild cognitive impairment or mild dementia stage of disease, is currently approved in 48 countries and is under regulatory review in 10 countries. Lecanemab’s SC-AI formulation is considered more convenient, lasting approximately 15 seconds to administer. Under the conditions of the recent approval, patients would undergo an 18-month course of lecanemab IV at 10 mg/kg every 2 weeks, followed by the option to either continue with IV treatment or begin the new weekly 360-mg SC-AI. The latest sBLA aims to eliminate that wait time for SC-AI, allowing patients to start weekly treatment at the onset of their prescription.

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Lecanemab and its SC-AI were approved based on data from the phase 3 Clarity AD trial (NCT03887455), a 1795-patient study testing the effects of the drug over an 18-month. While the study primarily focused on the IV formulation, a separate subgroup of patients received the SC-AI formulation, with outcomes that appeared more promising than the original formulation.³

After 6 months of treatment, those on SC-AI lecanemab achieved 14% greater amyloid plaque clearance compared with the IV dosing cohort. In addition, use of this SC-AI led to improved amyloid-related imaging abnormality (ARIA) rates. In Clarity AD, ARIA-edema, ARIA-hemorrhage, and ARIA-H occurred in 12.6%, 17.3%, and 8.9% of patients on IV lecanemab versus 16.7%, 22.2%, and 8.3% on SC-AI, though interpretation was limited by smaller sample size.

IV therapies often impose significant burdens on costs, providers, patients, and caregivers; however, a U.S. cost comparison model study published in Neurology and Therapy suggested that SC-AI administration may deliver meaningful societal savings by lowering treatment costs, reducing time demands, and easing quality-of-life burdens. The analysis, conducted over four years from a societal perspective, included both per-patient comparisons and population-level assessments that accounted for treatment rates and SC uptake.⁴

Overall, SC-AI was estimated to yield per-patient savings of $72,891 to $80,925 over four years compared with IV administration, translating to annual savings of $18,223 to $20,231 at willingness-to-pay thresholds of $150,000 and $200,000 per quality-adjusted life-year gained. The projected savings with SC-AI lecanemab were driven by reductions of $40,638 in treatment costs, $8151 in administration time, and $24,102–$32,136 in QOL related expenses per patient.

REFERENCES
1. Eisai Initiated Rolling Supplemental Biologics License Application to the U.S. FDA for LEQEMBI® IQLIKTM (lecanemab-irmb) as a Subcutaneous Starting Dose for the Treatment of Early Alzheimer’s Disease Under Fast Track Status. News release. Eisai. September 3, 2025. Accessed September 3, 2025.
2. FDA Approves LEQEMBI® IQLIK™ (lecanemab-irmb) Subcutaneous Injection for Maintenance Dosing for the Treatment of Early Alzheimer's Disease. News release. August 29, 2025. Accessed September 3, 2025. https://www.prnewswire.com/news-releases/fda-approves-leqembi-iqlik-lecanemab-irmb-subcutaneous-injection-for-maintenance-dosing-for-the-treatment-of-early-alzheimers-disease-302542371.html
3. 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: CTAD conference; October 24-27, 2023; Presentation 4.
4. 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. Neurology & Therapy. Published online July 4, 2025. doi:10.1007/s40120-025-00790-2