The Magic of Crystal Structure-Based Inhibitor Optimization: Development of a Butyrylcholinesterase Inhibitor with Picomolar Affinity and in Vivo Activity

The enzymatic activity of butyrylcholinesterase (BChE) in the brain increases with the progression of Alzheimer's disease, thus classifying BChE as a promising drug target in advanced Alzheimer's disease. We used structure-based drug discovery approaches to develop potent, selective, and reversible human BChE inhibitors. The most potent, compound 3, had a picomolar inhibition constant versus BChE due to strong cation-pi interactions, as revealed by the solved crystal structure of its complex with human BChE. Additionally, compound 3 inhibits BChE ex vivo and is noncytotoxic. In vitro pharmacokinetic experiments show that compound 3 is highly protein bound, highly permeable, and metabolically stable. Finally, compound 3 crosses the blood-brain barrier, and it improves memory, cognitive functions, and learning abilities of mice in a scopolamine model of dementia. Compound 3 is thus a promising advanced lead compound for the development of drugs for alleviating symptoms of cholinergic hypofunction in patients with advanced Alzheimer's disease.