Eisai and Biogen Release Long-Term Treatment Data for Lecanemab

Eisai (ESAIY) and Biogen (BIIB) announced that new real-world findings from an analysis of long-term treatment persistence and baseline characteristics among people receiving intravenou lecanemab, an anti-amyloid-beta protofibril antibody, showed that most patients continue with ongoing lecanemab therapy after the initial 18 months of treatment. The analysis was presented at the 20th International Conference on Alzheimer's and Parkinson's Diseases and Related Neurological Disorders in Copenhagen, Denmark, and online. In real-world clinical practice, patients with chronic diseases who stay on their treatments longer tend to experience better clinical outcomes and higher satisfaction. Ninety-four percent of patients who completed 18 months of lecanemab treatment in the Phase III Clarity AD study chose to continue maintenance treatment by enrolling in the subsequent open-label, long-term extension study. In the OLE of the Clarity AD study, patients continue to benefit from four years of lecanemab treatment compared with the natural course of Alzheimer's disease. Long-Term Persistence and Patient Characteristics for Lecanemab in Real-World Use in the United States: This analysis is the first time real-world lecanemab data on treatment persistence beyond 18 months has been reported. This study was a retrospective observational analysis using the PurpleLab CLEAR Claims database, a comprehensive dataset based on medical insurance claims across the United States and was conducted to evaluate the long-term treatment persistence of lecanemab in real-world clinical practice. The analysis population consisted of 10,763 individuals who met the requirement for continuous healthcare encounters, out of the 13,388 individuals recorded in the database who received at least one IV treatment with lecanemab between January 6, 2023 and November 30, 2025. At baseline, the mean age was 73.8 years and 56.5% were female. The most common comorbidities were dyslipidemia and hypertension. The mean follow-up duration was 350.9 days. The average number of administrations was 1.7 per month, and the mean dosing interval was 16.4 days, which was generally consistent with the recommended every two weeks dosing. The time-dependent proportion of patients who remained on lecanemab treatment was evaluated using the Kaplan-Meier method in a subgroup of 371 patients who initiated treatment in 2023 and had 20 months of continuous follow-up, thereby enabling assessment of long-term treatment persistence beyond 18 months. As a result, 78.4% of individuals continued lecanemab treatment at 18 months, 71.7% at 20 months, and 67.3% at 24 months. Of the 78.4% of patients who remained on lecanemab at 18 months, the majority of them continued treatment during the maintenance period beyond 18 months, confirming a high rate of treatment persistence with lecanemab in real-world clinical practice. The patient characteristics and dosing patterns observed in this claims-based analysis were generally similar to those reported in the Clarity AD study. Furthermore, the relatively high treatment adherence observed among individuals suggests that potential delays due to MRI monitoring requirements, adverse events, and other factors did not substantially affect lecanemab dosing.