Multi-target-directed ligands for Alzheimer's disease: Discovery of chromone-based monoamine oxidase/cholinesterase inhibitors

There has been a substantial research effort to design multi-target ligands for the treatment of Alzheimer's disease (AD), an approach that is moved by the knowledge that AD is a complex and multifactorial disease affecting many linked to pathological pathways. Accordingly, we have devoted efforts to develop multi-target ligands based on the chromone scaffold. As a result, a small library of chromone derivatives was synthesized and screened towards human cholinesterases and monoamine oxidases. Compounds 2-(dimethylamino)ethyl (E)-3-(4-oxo-2-(p-methylphenlcarbamoyl)-4H-chromen-6-yl)acrylate (9a) and 2-(dimethylamino)ethyl (E)-3-(4-oxo-3-(phenylcarbamoyl)-4H-chromen-6-yl)acrylate (23a) were identified as the most promising multi-target inhibitors of the series. Compound 9a acted as a potent, selective and bifunctional AChEI (IC50 = 0.21 mM, Ki = 0.19 mM) and displayed dual hMAO inhibitory activity (hMAO-A IC50 = 0.94 mM, Ki = 0.057 mM and hMAO-B IC50 = 3.81 mM, Ki = 0.48 mM). Compound 23a acted as a selective IMAO-B (IC50 = 0.63 mM, Ki = 0.34 mM) while still displaying hChE inhibitory and bifunctional activity in the low micromolar range. Overall, these two compounds stand out as reversible multi-target inhibitors with favourable permeability, toxicological and drug-like profiles, thus being valid candidates for subsequent optimization and pre-clinical studies.