Here, in a series of post-hoc analyses of data from a phase 2, randomized, placebo-controlled trial of mild-to-moderate AD (RCT; NCT03605667), we examined whether concentrations of plasma biomarkers (Aβ42/40 ratio, T-tau, P-tau181, NfL, and glial fibrillary acidic protein (GFAP)) at baseline predicted change in clinical, and neuroimaging outcomes. This evidence concerns the gene MAPT and Alzheimer disease.