Modified titration of donanemab reduces ARIA risk and maintains amyloid reduction

INTRODUCTION: TRAILBLAZER-ALZ 6 (NCT05738486) is a multicenter, double-blind, ongoing phase 3b study in early symptomatic Alzheimer's disease. METHODS: Participants (n = 843) were randomized 1:1:1:1 (standard + three alternative donanemab dosing arms). Primary outcome was relative risk reduction (RRR) of amyloid-related imaging abnormalities with edema/effusions (ARIA-E) at 24 weeks assessed with Bayesian logistic regression. Amyloid plaque levels by positron emission tomography and serum donanemab pharmacokinetics were measured. RESULTS: arms were 23.7%, 13.7%, 18.6%, and 18.3%, respectively, at 24 weeks and similar at 52 weeks: 24.2%, 15.6%, 18.6%, and 18.8%, respectively. Modified titration met the 24-week primary outcome with 94% probability of achieving ≥ 20% RRR versus the standard arm. Modified titration also had significantly lower ARIA-E severity, but similar cumulative exposure and mean amyloid reduction compared to the standard arm. DISCUSSION: Gradual up-titration of dose significantly reduced ARIA-E risk while demonstrating comparable pharmacokinetics/pharmacodynamics compared to standard dosing. HIGHLIGHTS: In TRAILBLAZER-ALZ 6, the amyloid-related imaging abnormalities-edema/effusions (ARIA-E) frequency was 13.7% in the modified titration arm compared to 23.7% in the standard arm at week 24. The modified titration arm met the primary endpoint of ARIA-E relative risk reduction at 24 weeks versus the standard arm. The modified titration versus standard arm at week 24 had comparable non-ARIA-E related safety profile, amyloid reduction, plasma phosphorylated tau217 reduction, cumulative exposure, and pharmacokinetics. Data at week 52 were consistent with week 24 results.