Long-term LEQEMBI treatment suggests potential to delay disease progression from Mild Cognitive Impairment (MCI) to moderate Alzheimer’s disease by up to 8.3 years in low-amyloid group who started treatment at an early stage
New safety and efficacy data presented at scientific symposium on subcutaneous formulation for LEQEMBI initiation treatment, which is under regulatory review in the United States
TOKYO and CAMBRIDGE, Mass., Dec. 3, 2025 /PRNewswire/ — Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A. Viehbacher, “Biogen”) announced today that the latest findings on time savings with continued treatment with humanized anti-soluble aggregated amyloid-beta (Aβ) monoclonal antibody lecanemab (generic name, U.S. brand name LEQEMBI®) were presented at the 18th Clinical Trials on Alzheimer’s Disease (CTAD) Conference. Additionally, a scientific symposium was held on the subcutaneous formulation (SC-AI), which was approved for maintenance treatment in the United States in August 2025, and the rolling supplemental Biologics License Application (sBLA) for initiation treatment was completed in November 2025. The application for a subcutaneous injectable formulation in Japan was submitted in November 2025.
Alzheimer’s disease (AD) is a progressive, relentless disease with Aβ and tau as hallmarks, that is caused by a continuous underlying neurotoxic process driven by protofibrils* (PF) that begins before amyloid plaque removal and continues afterward.1,2,3 Only LEQEMBI fights AD in two ways – targeting both PF and amyloid plaque, which can impact tau downstream.
Estimating the 10-Year Time-Savings Benefits of Lecanemab Treatment (Presentation: December 3, 2:40 PM PT)
This analysis used data from the Clarity AD open-label extension (OLE) and 16 clinical studies of monoclonal antibodies for AD to estimate long-term AD progression over 10 years and the slowing effect of continued lecanemab treatment. The analysis evaluated estimated “time savings” (slowing of disease progression) compared to natural decline based on ADNI** (Alzheimer’s Disease Neuroimaging Initiative) data (untreated group), using Clinical Dementia Rating – Sum of Boxes (CDR-SB). These results suggest that early initiation and long-term lecanemab treatment may continue to slow AD progression and help maintain cognitive function over a longer period.
Findings from each group:
Time Savings from Mild Cognitive Impairment (MCI) Due to AD to Mild AD
The time to progression from MCI due to AD to mild AD was 7.2 years in the untreated group, whereas with continued LEQEMBI treatment to the onset of moderate AD, progression to mild AD took 9.7 years, indicating a time savings of 2.5 years.
In the low-amyloid group (patients who started treatment at an early stage: amyloid PET