Increased risk of infusion‐related reactions switching between monoclonal antibodies for Alzheimer's disease: A case series

INTRODUCTION: Monoclonal antibodies (mAbs) targeting amyloid plaques are increasingly used in early Alzheimer's disease (AD). Infusion-related reactions (IRRs) are recognized class effects, yet little is known about their occurrence when switching between anti-amyloid agents. METHODS: We performed a retrospective case series of four patients who transitioned from aducanumab to lecanemab or donanemab. Clinical data included demographics, infusion dates, reaction characteristics, severity grading, interventions, and outcomes. RESULTS: We report four patients who developed IRRs during or shortly after their first lecanemab infusion. In subsequent infusions, pre-medication reduced recurrence in some cases. DISCUSSION: This case series suggests that prior exposure to mAbs may predispose some patients to more pronounced IRRs when switched to another agent in the class. Larger observational studies are needed to establish the incidence, mechanisms, and best practices for prevention and management.