Japan has approved the subcutaneous autoinjector formulation of Leqembi (lecanemab) for the treatment of early Alzheimer's disease, becoming the third country globally to authorize the therapy in this format.
The Leqembi Pen enables patients or care partners to self-administer two injections totaling 500 mg once weekly at home, with each injection taking approximately 15 seconds. The subcutaneous dosing complements the existing intravenous formulation, which is administered every two weeks in hospital settings. Clinical data showed the once-weekly 500 mg subcutaneous formulation delivered similar exposure levels to the intravenous regimen given biweekly.
The approval rests on data from the Phase 3 Clarity AD study alongside multiple subcutaneous administration sub-studies. The overall safety profile was broadly consistent with the intravenous version, though systemic injection-related reactions occurred less frequently with the subcutaneous route at just 1.4%. Patients continue to require brain MRI monitoring before treatment initiation and at designated intervals thereafter, consistent with the requirements for the intravenous formulation.
The subcutaneous autoinjector had previously received approval in the United States, and China approved subcutaneous initiation treatment in September 2026. Leqembi is now approved in 53 countries, with regulatory review underway in six additional countries and regions.
The therapy is the product of a collaboration between Swedish biotech BioArctic AB and Japanese pharma giant Eisai, which has spanned since 2005. Eisai leads clinical development, market approval applications and global commercialization, while BioArctic retains commercialization rights in the Nordic region and is entitled to sales milestone payments and royalties on global sales without bearing development costs.
