LEQEMBI (lecanemab-irmb) is the Eisai and Biogen humanized IgG1 monoclonal antibody targeting soluble and insoluble amyloid-beta protofibrils. It is FDA-approved for the treatment of early Alzheimer's disease (mild cognitive impairment or mild dementia) in patients with confirmed amyloid pathology. Approval came under accelerated approval in January 2023 and traditional approval in July 2023 following the Phase 3 CLARITY-AD readout.
The formulation and administration landscape has expanded meaningfully across 2025-2026. The original intravenous (IV) infusion (once every two weeks) remains the reference. LEQEMBI IQLIK is the subcutaneous autoinjector formulation: FDA-approved for maintenance dosing in 2025 and expanded to at-home initiation dosing on July 29, 2026 (announced on the Biogen Q2 2026 earnings call), providing patient-friendly SC autoinjector dosing throughout the full treatment course rather than only during the maintenance phase.
Real-world evidence continues to accumulate. The Eisai-Biogen LEADER study presented at AAIC 2026 in London (Tuesday July 14) documented 17-month real-world outcomes across a large multi-site LEQEMBI-treated cohort. ARIA-E (amyloid-related imaging abnormalities with edema) rates are one of the key monitoring points; the modified titration regimens developed for LEQEMBI and Eli Lilly's Kisunla (donanemab-azbt, the second FDA-approved anti-amyloid mAb) are actively studied.
Stories here cover LEQEMBI trial readouts, formulation approvals, real-world data, and the broader anti-amyloid disease-modifying Alzheimer's therapy landscape. See [[lecanemab]], [[biogen]], [[eisai]], and [[alzheimers-disease]] for adjacent threads.
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.
Biogen (NASDAQ: BIIB) reported Q2 2026 earnings before market open Wednesday July 29, 2026 with total revenue of $2.74 billion (+3% year-over-year), GAAP diluted EPS of $0.66, and non-GAAP diluted EPS of $3.60, beating Wall Street consensus. Growth-portfolio drugs (LEQEMBI, SKYCLARYS, SYFOVRE, and EMPAVELI) delivered year-over-year growth and, in aggregate, growth-portfolio revenue exceeded $1 billion for the quarter, surpassing Biogen's legacy multiple sclerosis franchise. Two major pipeline milestones anchored the earnings call: the FDA approved LEQEMBI IQLIK (lecanemab-irmb, a subcutaneous autoinjector formulation) for at-home initiation dosing (following the earlier approval of LEQEMBI IQLIK for maintenance dosing), providing patient-friendly dosing throughout the treatment course; and the Apellis acquisition that closed May 14, 2026 contributed $128 million in combined SYFOVRE (pegcetacoplan intravitreal, for geographic atrophy) and EMPAVELI (pegcetacoplan subcutaneous, for paroxysmal nocturnal hemoglobinuria and C3 glomerulopathy) revenue in the partial quarter. Biogen expects approximately 0.85 EPS dilution from the Apellis acquisition in 2026 with accretion in 2027 and estimated run-rate synergies of at least $250 million exiting 2027. 2026 revenue guidance raised to mid-single-digit growth with non-GAAP EPS guidance of $12-13.
Eisai and Biogen announced Tuesday July 14, 2026 that data from the real-world Lecanemab in Early Alzheimer's Disease (LEADER) Study, presented at AAIC 2026 in London during the Developing Topics Session '#3-33-DEV-A: Lecanemab Three Years Post-Approval: A Comprehensive Multicenter, Real-World, Retrospective Study (LEADER) in Diverse US Clinical Settings,' documented durable clinical outcomes with LEQEMBI in early Alzheimer's disease. The analysis included 432 early Alzheimer's disease patients from diverse US clinical settings who had received at least seven LEQEMBI infusions as of May 2026. Over an average of 17 months of treatment, 75.9% of patients remained clinically stable and 6.6% improved (moving from mild Alzheimer's disease dementia to mild cognitive impairment due to Alzheimer's disease). 87% of patients chose to remain on LEQEMBI treatment. Results were consistent across sex, race, ethnicity, and APOE genotype, supporting long-term benefits of continuous treatment outside of a controlled clinical trial setting.
Eisai and Biogen announced Sunday July 12, 2026 that new clinical data presented at AAIC 2026 in London support that the LEQEMBI (lecanemab) subcutaneous autoinjector (SC-AI) formulation offers efficacy and safety comparable to intravenous (IV) administration in people with early Alzheimer's disease. Data were featured during the Developing Topics Session titled 'Lecanemab Subcutaneous Formulation in Early Alzheimer's Disease: Emerging Clinical Evidence and Practical Use Considerations,' covering the SC formulation, long-term use across diverse patient groups, maintenance dosing, and at-home administration. The findings support a fully subcutaneous treatment pathway from initiation through maintenance treatment, offering greater convenience and flexibility for patients and care partners. The FDA approved Eisai's Biologics License Application (BLA) for subcutaneous maintenance dosing with LEQEMBI IQLIK in August 2025; the SC autoinjector data at AAIC 2026 extends that framework to initial treatment and long-term dosing. Lecanemab is a humanized IgG1 monoclonal antibody selective for amyloid protofibrils; the July 12 dataset is peptide-adjacent to the broader biologic-CNS delivery coverage.