Eisai (TSE: 4523) and Biogen (NASDAQ: BIIB) Announced Wednesday August 26, 2026 That Once-Weekly Subcutaneous Lecanemab-Irmb (Brand Name Leqembi Iqlik) Is Now Commercially Available in the United States for Initiation Therapy in Adults With Early Alzheimer's Disease (Mild Cognitive Impairment or Mild Dementia Due to Alzheimer's Disease); The US Launch Represents the Anti-Amyloid Monoclonal Antibody Class's Substantive Transition From the Existing Twice-Monthly Intravenous Infusion Format to a Weekly Subcutaneous Injection That Substantially Improves Patient Accessibility and Reduces the Infrastructure Burden (Infusion Center Scheduling, Long Chair Time, IV Line Placement) That Has Constrained the Ongoing Global Leqembi Launch Since Initial 2023 FDA Approval
Eisai (TSE: 4523) and Biogen (NASDAQ: BIIB) announced Wednesday August 26, 2026 that once-weekly subcutaneous lecanemab-irmb (brand name Leqembi Iqlik) is now commercially available in the United States for initiation therapy in adults with early Alzheimer's disease (AD). Approved patient population: adults with mild cognitive impairment (MCI) or mild dementia due to AD, the same patient population that was approved for the IV formulation. Mechanism: lecanemab is a humanized IgG1 monoclonal antibody targeting soluble amyloid-beta protofibrils and preventing their aggregation into amyloid plaques that drive Alzheimer's pathology. Delivery format shift: the US launch represents the anti-amyloid class's substantive transition from the existing twice-monthly IV infusion format (requiring 1 hour of infusion time plus monitoring) to a weekly subcutaneous injection that substantially improves patient accessibility and reduces the infrastructure burden that has constrained the ongoing global Leqembi launch. Practical impact on Leqembi commercial trajectory: the SC format removes several barriers including infusion center scheduling constraints, long chair time per dose, and IV line placement complications. Eisai and Biogen have been struggling with slower-than-expected Leqembi launch since initial 2023 FDA approval due to reimbursement complexity, MRI monitoring requirements for amyloid-related imaging abnormalities (ARIA), and infrastructure requirements; the SC availability addresses one substantive barrier. Q2 2026 Leqembi worldwide sales reached roughly $340 million; the SC transition is expected to accelerate the commercial trajectory in Q4 2026 and into 2027.