Donanemab exposure‐response in early symptomatic Alzheimer's disease

INTRODUCTION: These analyses aimed to identify factors impacting donanemab exposure, amyloid plaque, and clinical efficacy in early symptomatic Alzheimer's disease using a population pharmacokinetic/pharmacodynamic (PK/PD) approach. METHODS: Analyses included donanemab trial participants (NCT02624778; NCT03367403; NCT04640077; NCT04437511). Dose- and exposure-response relationships were characterized relative to amyloid plaque lowering using indirect response PK/PD and disease progression models. RESULTS: Donanemab population PK was described by a biphasic distribution with an estimated terminal elimination half-life of approximately 12.1 days for a typical participant (72 kg body weight, 1:2560 maximum antidrug antibody ADA titer). Amyloid reduction was associated with maintaining median serum donanemab concentrations over 15 µg/mL (95% confidence interval: 8.54, 18.0). After completing active treatment, simulations showed an estimated plaque reaccumulation rate (median, 95% confidence interval) of 2.8 (2.16, 3.11) Centiloids/year. The donanemab disease progression model showed a clear treatment effect. DISCUSSION: These donanemab models can inform dosing strategies in future clinical trials. HIGHLIGHTS: Weight-based and flat dosing had similar exposure metrics; flat dosing was adopted. Donanemab exposure was influenced by weight and titer (not clinically relevant). 2.8 Centiloids/year amyloid reaccumulation rate observed upon donanemab treatment completion. Around 30% reduction in disease progression rate on treatment for integrated Alzheimer's Disease Rating Scale (iADRS) and Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB).