Quantile regression to characterize solanezumab effects in Alzheimer's disease trials

INTRODUCTION: In two solanezumab trials for mild-to-moderate Alzheimer's disease (AD) dementia, 27% of patients had biomarker confirmation of amyloid status. Of these, approximately 25% of mild patients and approximately 10% of moderate patients were amyloid negative and, as a group, did not exhibit clinical progression typical of AD. This post-hoc analysis describes a statistical surrogate for amyloid status. METHODS: Quantile regression was used to examine solanezumab treatment effects at fixed percentiles of varying degrees of clinical progression, with lowest percentiles (minimal progression atypical of AD) and higher percentiles acting as surrogates for amyloid negativity or positivity, respectively. RESULTS: In mild patients, solanezumab treatment effect was greater in higher percentiles of progression and less in lowest percentiles (AD-atypical). In moderate patients, solanezumab did not show effects across most percentiles. DISCUSSION: Results are compatible with design of the ongoing solanezumab EXPEDITION 3 trial that limits patients to those with mild AD dementia and evidence of amyloid pathology.