The FDA’s extension will give reviewers more time to review a major amendment to Biogen and Eisai’s application for a subcutaneous induction formulation of Alzheimer’s therapy Leqembi. The new target action date is on Aug. 24.
Biogen and Eisai may have to wait three more months to learn the FDA’s verdict on their bid to start patients on an under-the-skin formulation of their anti-amyloid Alzheimer’s disease therapy.
As part of the ongoing drug review process, the FDA has requested additional information regarding the proposed use of subcutaneous Leqembi for treatment initiation, the pharma partners announced Friday. The regulator then deemed the companies’ submission as a major amendment to the application and pushed back the target action date.
The FDA’s original deadline for a decision was May 24. Now, Biogen and Eisai are expecting a verdict on or before August 24.
Analysts at RBC Capital Markets expect the impact of this delay to be “limited,” according to a Friday morning note to investors, given that with either decision date, reimbursements for the drug “would not have kicked in until 2027.”
The delay “pushes out a catalyst we believe the Street had been keying in on to provide visibility on medium-term Leqembi growth acceleration and adds incremental risk” to Biogen, RBC added, “but should still ultimately get resolved.”
Leqembi was first approved in January 2023 under the FDA’s accelerated pathway and in July that year became the first anti-amyloid antibody for Alzheimer’s to win the agency’s full approval. Leqembi is administered intravenously over one hour every two weeks.
In September 2025, the FDA cleared a new formulation of Leqembi, Leqembi Iqlik, that allowed the drug to be administered via an under-the-skin injection—a more convenient route of administration that also opened the option of at-home treatments. This approval, however, only applied to maintenance treatments. New patients would still have to undergo an 18-month induction period.
Biogen and Eisai are now proposing to use this subcutaneous formulation to initiate patients, completely eliminating the need for intravenous infusions. To back their application, the partners submitted data showing that Leqembi Iqlik, given weekly, achieved bioequivalent drug exposure to the intravenous version given once every two weeks, according to a January 2026 news release.
Both formulations of Leqembi had similar safety profiles, the companies added.
If approved, Leqembi Iqlik would be the first anti-amyloid therapy that offers patients at-home, subcutaneous dosing for the entirety of their treatment journey, Biogen and Eisai said in January. A nod would also allow them to better compete with Eli Lilly’s Kisunla on the convenience front.
An approval is “going to be extremely important,” Chris Viehbacher, Biogen’s CEO, said at the J.P. Morgan Healthcare Conference in January. Kisunla offers once-monthly infusion compared to Leqembi’s biweekly infusion. Kisunla’s convenience edge “is going to go away once we have a subcutaneous formulation,” Viehbacher said.
A subcutaneous, at-home treatment option also plays into Biogen’s strategy of catching patients who have finished treatment with Kisunla and are looking to transition to another Alzheimer’s therapy.
The first batch of Kisunla-treated patients are set to end their 18-month treatment period, Alisha Alaimo, Biogen’s head of North America, said during the company’s Q1 call on April 29. “Physicians are asking, what do we do? Patients in general, who are on either of the products, want to stay on product. There is a fear of coming off and having a decline in their cognition.”
