FDA’s extended review of a subcutaneous formulation of lecanemab highlights ongoing regulatory evaluation of alternative anti-amyloid delivery approaches for early Alzheimer’s disease.
Eisai and Biogen announced on May 8, 2026 that FDA has
The revised Prescription Drug User Fee Act action date is now Aug. 24, 2026, a three-month extension from the original review timeline. According to the companies, the agency requested additional information during the review process and classified the submission as a major amendment, requiring additional time for evaluation.
The companies stated that FDA has not raised concerns regarding the approvability of the application to date. Lecanemab is currently approved to treat AD in patients with mild cognitive impairment or mild dementia stages of disease. The therapy is available as both intravenous infusion and subcutaneous injection formulations.
Eisai and Biogen indicated that the review extension is linked to additional information submitted to the agency as part of the ongoing evaluation of the subcutaneous starting-dose regimen.
“[FDA] has not raised any concerns to date regarding the approvability of [Leqembi Iqlik] as a starting dose,” the companies stated in a press release.1
According to Biogen and Eisai, the clinical data package supporting subcutaneous administration across multiple studies and dosing regimens supports the biologic’s use as an initiation therapy option for AD. The subcutaneous maintenance dosing regimen for lecanemab previously received FDA approval in August 2025.
The companies will continue discussions with FDA during the review process and remain focused on expanding treatment flexibility for patients and caregivers.
If approved, the once-weekly subcutaneous autoinjector formulation could provide an alternative to intravenous administration in healthcare settings. According to the companies, the subcutaneous formulation may support home-based administration and reduce healthcare resource utilization associated with infusion-based dosing.
The companies noted that each 250-mg autoinjector injection requires approximately 15 seconds to administer. The proposed regimen includes two 250-mg injections to achieve a 500-mg weekly dose.2 Subcutaneous administration could streamline treatment pathways by reducing infusion preparation requirements and nurse monitoring associated with intravenous delivery.
“Eisai and Biogen look forward to ongoing discussions with [FDA] as the review progresses and are committed to bringing this important advancement to patients and care partners as quickly as possible to provide greater flexibility and choice in how anti-amyloid treatment is delivered,” the companies stated in the release.1
In February 2026, Eisai and Biogen announced that China’s National Medical Products Administration designated the BLA for the subcutaneous autoinjector formulation of lecanemab for priority review.2
The designation is intended to accelerate development and review of medicines with significant clinical value. If approved in China, the once-weekly subcutaneous formulation could be administered at home from treatment initiation as an alternative to biweekly intravenous dosing.
Eisai estimates that approximately 17 million patients in China were living with mild cognitive impairment or mild dementia due to AD in 2024.2,3 Lecanemab was launched in China in June 2024 and was later included in the country’s Commercial Insurance Innovative Drug List, which took effect in January 2026.2
Globally, lecanemab has received approvals from more than 50 regulatory authorities, according to the companies. Eisai leads global development and regulatory submissions for the therapy, while Eisai and Biogen co-commercialize and co-promote the product.2
