FDA Approves Subcutaneous Lecanemab-irmb (LEQEMBI) for Early Alzheimer Disease

On August 29, 2025, Biogen announced that the US Food and Drug Administration (FDA) approved Eisai’s Biologics License Application (sBLA) for once weekly subcutaneous lecanemab-irmb (LEQEMBI) subcutaneous to treat patients with early Alzheimer Disease, including those with mild cognitive impairment or mild dementia.1 Manufacturers plan to launch the product in the US on October 6, 2025.

“LEQEMBI IQLIK is the first and only anti-amyloid treatment to offer an at-home injection to help patients and care partners continue to treat this progressive, relentless disease after initial treatment of 18 months,” Biogen wrote in a statement.1

Lecanemab-irmb is a subcutaneous autoinjector containing 360 mg/1.8 mL (200 mg/mL that clinicians can administer in approximately 15 seconds. Lecanemab targets both amyloid plaque and protofibrils, which can influence downstream tau pathology.

The approval relied on subcutaneous sub-studies from the Phase 3 Clarity AD open-label extension trial. Researchers found that switching to weekly subcutaneous dosing maintains clinical and biomarker benefits at levels comparable to continued intravenous administration. Investigators evaluated safety in over 600 patients across multiple subcutaneous doses, including 49 patients receiving the 360 mg weekly dose, none of whom experienced injection-related adverse events.

Patients experienced systemic reactions in fewer than 1% of cases, compared with approximately 26% of intravenous patients. Mild-to-moderate local injection-site reactions affected roughly 11% of patients and did not interrupt treatment. Clinicians observed that rates of amyloid-related imaging abnormalities were similar to intravenous maintenance therapy and matched background rates in untreated patients, with most events occurring early in therapy.

In the Clarity AD core study, intravenous lecanemab reduced cognitive decline by 27% at 18 months on the Clinical Dementia Rating-Sum of Boxes compared with placebo. Follow-up data through 48 months showed that treatment continued to slow cognitive decline relative to expected trajectories in external cohorts.

Human factors and tolerability studies confirmed that patients and care partners can safely use the autoinjector at home. Clinicians noted that subcutaneous administration reduces the time and resources required for intravenous infusion while enabling patients who respond to therapy to maintain treatment.

Subcutaneous lecanemab shares the safety profile of intravenous treatment, including the potential for amyloid-related imaging abnormalities, infusion- or injection-related reactions, and hypersensitivity. Clinicians should perform baseline and periodic brain imaging and monitor patients closely during the first 14 weeks. They should also evaluate risk factors such as ApoE ε4 status, cerebral amyloid angiopathy, and concomitant antithrombotic therapy when initiating treatment.

The FDA had previously approved lecanemab-irmb administered via an intravenous injection on January 26, 2025.2 Now after 18 months of lecanemab-irmb (10 mg/kg) injections every 2 weeks, patients can either continue IV infusions at same dose every 4 weeks or start the new weekly 360 mg subcutaneous injection.1

“From the perspective of patients and care partners, benefits included the ability to use the device at home, shortening treatment time and to continue treatment without having to worry about visiting an infusion center,” Biogen wrote in a statement.1 “Healthcare providers reported that the device has the potential to provide a new option for patients who are responding well to LEQEMBI and should continue treatment.”

References

1. FDA Approves LEQEMBI® IQLIKTM (lecanemab-irmb) Subcutaneous Injection for Maintenance Dosing for the Treatment of Early Alzheimer’s Disease | Biogen. Biogen. Published 2025. Accessed August 29, 2025. https://investors.biogen.com/news-releases/news-release-details/fda-approves-leqembir-iqliktm-lecanemab-irmb-subcutaneous

2. Biogen. FDA Approves LEQEMBI® (lecanemab-irmb) IV Maintenance Dosing for the Treatment of Early Alzheimer’s Disease | Biogen. Biogen. Published 2025. https://investors.biogen.com/news-releases/news-release-details/fda-approves-leqembir-lecanemab-irmb-iv-maintenance-dosing