Plasma P-tau217 for detecting amyloid clearance after donanemab in Alzheimer's disease.

INTRODUCTION: This analysis of the phase 3 TRAILBLAZER-ALZ 2 trial examined whether plasma tau protein phosphorylated at threonine 217 (p-tau217) level can reliably monitor treatment-related amyloid clearance (TRAC) after donanemab treatment in early symptomatic Alzheimer's disease (AD). METHODS: Amyloid positron emission tomography (PET) and plasma p-tau217 levels were assessed at baseline and longitudinally during study treatment. The diagnostic performance of p-tau217 in detecting post-treatment TRAC (< 24.1 Centiloids [CL]) was evaluated by receiver operating characteristic (ROC) analysis. RESULTS: Plasma p-tau217 showed suboptimal performance in detecting TRAC by PET in donanemab-treated participants (N = 830), with an area under the ROC curve of 0.61 at 52 weeks. DISCUSSION: Despite reductions in plasma p-tau217 with donanemab treatment, this biomarker cannot currently be used to accurately detect TRAC by PET (< 24.1 CL) in individuals with early symptomatic AD.