Changes in Brain Volume with Bapineuzumab in Mild to Moderate Alzheimer's Disease

Background: Bapineuzumab, an anti-amyloid-beta monoclonal antibody, was evaluated in two placebo-controlled trials in APOE*epsilon 4 carriers and noncarriers, respectively, with Alzheimer's disease. Objectives: A volumetric magnetic resonance imaging substudy was performed to determine if bapineuzumab altered brain volume rate of change. Methods: Bapineuzumab dosages included 0.5 mg/kg in carriers and 0.5 or 1.0 mg/kg in noncarriers, every 13 weeks for 78 weeks. Volumetric outcomes included annualized brain, ventricular, and mean hippocampal boundary shift integrals (BBSI; VBSI; HBSI) up to Week 71. Treatment differences were estimated using mixed models for repeated measures. Results: For BBSI and HBSI, there were no significant treatment-related differences within either study, but, compared to pooled carriers and noncarriers receiving placebo, noncarriers receiving1.0 mg/kg bapineuzumab had greater increases in these measures. Bapineuzumab-treated patients showed significantly greater VBSI rates compared with placebo for 0.5 mg/kg in carriers and 1.0 mg/kg (but not 0.5 mg/kg) in noncarriers. Conclusions: Bapineuzumab produced an increase in ventricular volume compared with placebo. Etiology for this increase is unclear but may be related to amyloid-beta clearance or its consequences.