Pharmacokinetic/pharmacodynamic analyses of plasma pathophysiology biomarkers in subjects with early Alzheimer's disease following lecanemab treatment.

INTRODUCTION: Lecanemab, a novel monoclonal antibody targeting both neurotoxic amyloid beta (Aβ) protofibrils and Aβ plaques, substantially reduces markers of amyloid and significantly slows clinical decline on multiple measures of cognition and function in early AD in Phase 2 (Study 201) and Phase 3 (Study 301; Clarity AD) studies. In these clinical studies, several plasma biomarkers showed improvements comparing lecanemab with placebo. Herein, we utilized modeling and simulation to evaluate the long-term effects of lecanemab on pathophysiology biomarkers in plasma. METHODS: Plasma Aβ42/40 ratio, tau phosphorylated at threonine 181 (p-tau181), and glial fibrillary acidic protein (GFAP) data were pooled from lecanemab Phase 2 and 3 studies. Individual serum lecanemab exposure estimated using a population pharmacokinetic model was correlated with plasma biomarker concentrations using indirect response pharmacokinetic/pharmacodynamic (PK/PD) models. Simulations were conducted to evaluate the effect of lecanemab (10 mg/kg IV every 2 weeks, LEC10-BW) after 4 years of continuous treatment, discontinuation after 18 months of treatment or transitioning to less frequent dosing at 18, 24, or 30 months. RESULTS: PK/PD models describing the change in plasma biomarker levels over time in response to lecanemab treatment were developed, and simulations demonstrated that plasma biomarkers reverted toward pretreatment baseline after cessation of lecanemab treatment, with an average re-accumulation half-life of approximately 1 to 1.5 years, which was faster than amyloid plaque re-accumulation measured by positron emission tomography. Simulations illustrated transitioning to a lecanemab monthly dosing regimen was sufficient to stabilize plasma biomarker concentrations at levels consistent with ongoing inhibition of amyloid pathology and neuroinflammation. DISCUSSION: PK/PD model simulations demonstrated that plasma biomarkers serve as early indicators of amyloid accumulation and downstream effects. Plasma biomarker simulations suggest the need for ongoing lecanemab treatment even after amyloid plaque clearance. Transition to a less frequent monthly IV regimen at 18 months was shown to maintain the changes in plasma biomarker levels consistent with lecanemab efficacy.