Aβ (1-15) was used in a study investigating the presence of conformational epitope/s (mimotope/s) on fibrillar amyloid β-protein (1-42). The N-terminal Aβ fragments Aβ1-14, Aβ1-15, and Aβ1-16 are elevated in cell media and in CSF in response to γ-secretase inhibitor treatment. The fragments can serve as biomarkers in clinical studies of the effect of such inhibitors.