Alzheimer's disease (AD) is the leading cause of dementia worldwide, but current therapies provide only symptomatic relief. Multi-target directed ligands (MTDLs) represent a promising approach to address AD pathology by modulating multiple targets with a single molecule. Here we describe quinuclidine carbamates that act simultaneously on butyrylcholinesterase (BChE) and the cholinergic α7 nicotinic receptor (α7 nAChR), thereby approaching cholinergic dysfunction at two levels: by modulating acetylcholine degradation and by direct agonism at this receptor. Starting with the α7 nAChR agonist bradanicline, its amide group was replaced by a carbamate moiety to enhance BChE inhibition while retaining receptor agonism. These quinuclidine carbamates inhibited BChE in the submicromolar range with the desired selectivity over acetylcholinesterase (AChE). In a calcium-flux assay on recombinant HEK293T cells expressing the α7 nAChR, all compounds were agonists of the α7 nAChR in the nanomolar range. Importantly, compound 6b displayed balanced, submicromolar activity against both targets. The crystal structures confirmed non-covalent binding to the active site of human BChE, and the 6b-hBChE complex also revealed an unprecedented flip of Tyr440, representing the first described example of backdoor opening for hBChE. Taken together, these results demonstrate that quinuclidine carbamates are promising dual modulators of hBChE and α7 nAChR, supporting their potential as MTDLs for AD therapy and highlighting this underexplored dual-target strategy as a promising approach in cholinergic drug discovery.
Keywords: Acetylcholine receptor; Alzheimer's disease; Butyrylcholinesterase; Cholinergic receptor; Human α7 nicotinic receptor (α7 nAChR); Multi-target-directed ligands; Quinuclidine carbamates.
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