To report the initial findings up to 36 months from the ongoing Clarity AD open-label extension (OLE) study.

In the 18-month, phase 3 Clarity AD study, lecanemab, an amyloid-beta (Aβ) antibody, demonstrated amyloid reduction and slowing cognition and function decline in early symptomatic Alzheimer’s disease (AD). An OLE of Clarity AD is evaluating long-term safety and efficacy of lecanemab.

Clarity AD is an 18-month, randomized study (core) followed by and open-label OLE in phase individuals with early AD. Clinical (CDR-SB, ADAS-Cog14, and ADCS-MCI-ADL) and biomarker (PET, Aβ42/40 ratio, and ptau181) outcomes were evaluated overall as well as by examining ‘delayed start’ (core:placebo followed by OLE:lecanemab) and ‘early start’ (core:lecanemab followed by OLE:lecanemab) cohorts. Analyses by core baseline tau PET levels were conducted from the tau PET sub-study.

Overall, 1385 participants enrolled in the OLE. Across clinical endpoints, lecanemab-treated participants continued to benefit through 24 months. Separation between early and delayed start was maintained between 18 and 36 months (p<0.05), with a similar disease trajectory when all participants received lecanemab. Biomarker changes continued to improve and were seen in as early as 3 months in newly-treated lecanemab participants. Across assessments, consistent rates of clinical stability or improvements were observed regardless of baseline tau levels, with the highest rates of improvements observed for the low tau group at 36 months (no decline:59%; improvement:51%). No new safety signals were observed ARIA rates are low (similar to ARIA rates on placebo) after 6 months. A time to worsening CDR-SB analysis demonstrated that ARIA is not associated with accelerated long-term progression.

In Clarity AD, maintenance of treatment difference with ongoing lecanemab treatment through 36 months versus newly treated lecanemab participants is consistent with a disease-modifying effect. Delayed start and lower pathology group results support early initiation of lecanemab treatment.