FDA extended its review of a supplemental biologics license application (sBLA)for a once-weekly subcutaneous starting dose of Leqembi (lecanemab-irmb) by three months.

The decision pushes the new action date to August 24, 2026, after requesting additional information from Eisai and Biogen.

Why was Leqembi’s sBLA extended?

Eisai and Biogen initially submitted the sBLA for Leqembi Iqlik, a once-weekly subcutaneous injection formulation intended to serve as a starting dose for patients with early Alzheimer's disease, back in January 2025. The agency then approved the application in September 2025, based off of data from the Phase III Clarity AD trial.

Then on January 26, 2026, FDA began its priority review of Leqembi Iqlkik.² During its review of the application, FDA requested additional information which constituted a major amendment to the application and also triggered the standard three-month extension in order to allow sufficient time for a full review of the new materials.¹

However, both Eisai and Biogen noted that FDA has no yet raised any concerns regarding the approval of Leqembi Iqlik as a starting dose, and that the extension is procedural rather than a signal of safety or efficacy concerns.¹

What is already approved and what does the new sBLA add?

Leqembi is currently approved as an intravenous infusion for the treatment of early Alzheimer's disease, indicated for patients with mild cognitive impairment or mild dementia, along with a subcutaneous maintenance dosing regimen, which received FDA approval on August 26, 2025. Following the approvals, Leqembi is approved by more than 50 regulatory authorities worldwide.¹

The pending application for Leqembi Iqlik is expected to add a subcutaneous starting dose option, completing a fully subcutaneous treatment pathway and giving patients and physicians greater flexibility in how anti-amyloid therapy is initiated and maintained.¹

What are the key safety considerations?

Leqembi carries a boxed warning for amyloid-related imaging abnormalities (ARIA), a class effect associated with anti-amyloid monoclonal antibodies.¹ ARIA can present as brain edema or microhemorrhages and is usually asymptomatic, though serious and life-threatening events including seizure and fatal intracerebral hemorrhage have been observed.

ARIA occurred in 21% of Leqembi -treated patients versus 9% on placebo in clinical trials, with symptomatic ARIA in 3% and serious symptoms in 0.7%.¹ Infusion-related reactions occurred in 26% of patients receiving intravenous Leqembi, mostly with the first infusion and predominantly mild to moderate in severity. The safety profile of the subcutaneous maintenance formulation remained similar to the intravenous version, with localized and less frequent systemic injection-related reactions reported as mild to moderate.¹

Sources

1. Update on FDA Priority Review of LEQEMBI® IQLIK™ (lecanemab-irmb) Subcutaneous Injection as a Starting Dose for Early Alzheimer's Disease Eisai Co. Biogen May 8, 2026 https://www.prnewswire.com/news-releases/update-on-fda-priority-review-of-leqembi-iqlik-lecanemab-irmb-subcutaneous-injection-as-a-starting-dose-for-early-alzheimers-disease-302766585.html
2. FDA Accepts LEQEMBI® IQLIKTM (lecanemab-irmb) Supplemental Biologics License Application as a Subcutaneous Starting Dose for the Treatment of Early Alzheimer's Disease under Priority Review. News release. Eisai and Biogen. January 25, 2026. Accessed January 26, 2026. https://www.eisai.com/news/2026/pdf/enews202605pdf.pdf