(Figure Presented) Alzheimer's disease (AD) is a progressive neurodegenerative disorder, affecting more than 20 million people world-wide. Only palliative therapies are available today. We identified a novel D-enantiomeric amino acid peptide "D3" with significant Aβ disaggregation and Aβ aggregation inhibiting properties in vitro an in vivo. It inhibits cytotoxicity in cell culture and reduces amyloid plaque load and cerebral damage of transgenic AD mouse models. D3 might be a tool for further research approaches on the origin of AD and might provide a novel basis for therapeutic and preventive approaches to AD. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.