A multimeric quinacrine conjugate as a potential inhibitor of Alzheimer's beta-amyloid fibril formation

Amyloid formation and accumulation of the amyloid beta-peptide (Abeta) in the brain is associated with Alzheimer's disease (AD) pathogenesis. Therefore, among the therapeutic approaches in development to fight the disease, the direct inhibition of the Abeta self-assembly process is currently widely investigated and is one of the most promising approaches. In this study we investigated the potential of a multimeric display of quinacrine derivatives, as compared to the monomer quinacrine, as a design principal for a novel class of inhibitors against Abeta fibril formation. The presented multimeric conjugate exhibits a cluster of four quinacrine derivatives on a rigid cyclopeptidic scaffold. Herein is reported the synthesis of the conjugate, together with the in vitro inhibitory evaluation of Abeta(1-40) fibrils using the thioflavin T fluorescence assay, and imaging with atomic force microscopy. Our data show that the multimeric compound inhibits Abeta(1-40) fibril formation with an IC(50) value of 20+/-10 microM, which contrasts with the nonactive monomeric analogue. This work suggests that assembling multiple copies of acridine moieties to a central scaffold, for multiple interactions, is a promising strategy for the engineering of inhibitors against Abeta fibril formation.