Clicked tacrine conjugates as acetylcholinesterase and beta-amyloid directed compounds

The multifaceted nature of Alzheimer's disease (AD) has led to the development of multi-targeted compounds based on the classical AD drug, tacrine, first known to inhibit the acetylcholine-degrading enzyme acetylcholinesterase (AChE). In the present work, we explore the potentiality of multimers of tacrine in this field. The synthesis using the so-called click chemistry and the in vitro study of the conjugates are described. Two or four copies of the tacrine molecule are clicked on a constrained cyclopeptide template proven to be a convenient tool for multimeric presentation. The multimers significantly inhibit self-induced amyloid fibril formation from A beta(40) at low inhibitor to A beta molar ratios at which the tacrine monomer is fully inactive (Thioflavin T assays and AFM observation). Moreover, they have the capacity to bind to A beta(40) fibrils (SPR assays) while retaining the AChE inhibitory activity of the parent tacrine.