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Kuduk S.D.,Merck And Co. | Chang R.K.,Merck And Co. | Di Marco C.N.,Merck And Co. | Pitts D.R.,Merck And Co. | And 9 more authors.
Journal of Medicinal Chemistry | Year: 2011

One approach to ameliorate the cognitive decline in Alzheimer's disease (AD) has been to restore neuronal signaling from the basal forebrain cholinergic system via the activation of the M1 muscarinic receptor. A number of nonselective M1 muscarinic agonists have previously shown positive effects on cognitive behaviors in AD patients, but were limited due to cholinergic adverse events thought to be mediated by the activation of the M2 to M5 subtypes. One strategy to confer selectivity for M1 is the identification of positive allosteric modulators, which would target an allosteric site on the M1 receptor rather than the highly conserved orthosteric acetylcholine binding site. Quinoline carboxylic acids have been previously identified as highly selective M1 positive allosteric modulators with good pharmacokinetic and in vivo properties. Herein is described the optimization of a novel quinolizidinone carboxylic acid scaffold with 4-cyanopiperidines being a key discovery in terms of enhanced activity. In particular, modulator 4i gave high plasma free fractions, enhanced central nervous system (CNS) exposure, was efficacious in a rodent in vivo model of cognition, and afforded good physicochemical properties suitable for further preclinical evaluation. © 2011 American Chemical Society. Source

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