Quantifying Short-Term Functional Changes After Lecanemab Treatment in Early Alzheimer's Disease: An Exploratory...

Lecanemab is a monoclonal antibody targeting amyloid-β (Aβ) and is currently used in clinical practice for the treatment of early Alzheimer's disease (AD). However, noninvasive biomarkers reflecting its early efficacy are still unclear. This exploratory case report aims to investigate the combination of eye movement and gait analysis to quantitatively monitor shortterm functional changes during lecanemab treatment.

Two male patients, both diagnosed with mild Alzheimer's disease through amyloid- PET and both with the APOE ε3/ε3 genotype, received intravenous lecanemab (10 mg/kg, every two weeks) for three months. Cognitive assessments (Montreal Cognitive Assessment, Mini- Mental State Examination, Clinical Dementia Rating), eye movement tests (smooth pursuit, overlapping saccades, anti-saccades), and gait analysis under single-task and dual-task conditions were conducted at baseline and follow-up. Patient 1 (79 years old) showed stable cognitive function, significant improvement in multiple eye movement parameters, and partial improvement in gait under single-task conditions. Patient 2 (60 years old) did not follow up on cognitive function tests as scheduled and showed inconsistent changes in eye movement parameters, but improved selected gait measures under dual-task conditions, particularly a shorter turning time. Neither patient experienced Amyloid-Related Imaging Abnormalities or infusion-related adverse events during the infusion process.

This exploratory case report suggests that eye movement and gait analysis may be sensitive to short-term functional changes following lecanemab treatment, which were not consistently captured by traditional cognitive scales. These findings are hypothesis-generating and warrant further investigation in larger studies. Multimodal functional assessment may hold promise as a tool for monitoring early treatment effects in Alzheimer's disease.