Eisai, Biogen say Leqembi data suggests potential to delay disease progression

Eisai (ESALY) and Biogen (BIIB) announced that the latest findings on time savings with continued treatment with humanized anti-soluble aggregated amyloid-beta monoclonal antibody lecanemab were presented at the 18th Clinical Trials on Alzheimer’s Disease Conference. Additionally, a scientific symposium was held on the subcutaneous formulation, which was approved for maintenance treatment in the United States in August 2025, and the rolling supplemental Biologics License Application for initiation treatment was completed in November 2025. The application for a subcutaneous injectable formulation in Japan was submitted in November 2025. This analysis used data from the Clarity AD open-label extension 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” compared to natural decline based on ADNI data, using Clinical Dementia Rating – Sum of Boxes. 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. These findings indicate that earlier initiation of LEQEMBI treatment may provide a greater delay in disease progression. Furthermore, each additional year on LEQEMBI could further delay disease progression compared to stopping treatment, even long after plaque is expected to have been cleared.