The M4 mAChR is implicated in several CNS disorders and possesses an allosteric binding site for which ligands modulating the affinity and/or efficacy of ACh may be exploited for selective receptor targeting. We report the synthesis of a focused library of putative M4 PAMs derived from VU0152100 and VU10005. These compounds investigate the pharmacological effects of previously identified methoxy and fluoro substituents, providing useful estimates of affinity (KB), cooperativity (αβ), and direct agonist properties (τB).

The M4 mAChR is implicated in several CNS disorders and possesses an allosteric binding site for which ligands modulating the affinity and/or efficacy of ACh may be exploited for selective receptor targeting. We report the synthesis of a focused library of putative M4 PAMs derived from VU10004. These compounds investigate the pharmacological effects of target thieno[2,3-b]pyridines assembled from primary cycloalkanamines and cyclic secondary amines providing useful estimates of affinity (KB), cooperativity (αβ), and direct agonist properties (τB).

Positive allosteric modulators (PAMs) targeting the M4 muscarinic acetylcholine receptor (mAChR) offer greater sub-type selectivity and unique potential as central nervous system agents through their novel mode of action to traditional orthosteric ligands. In an attempt to elucidate the molecular determinants of allostery mediated by the exemplar thienopyridine M4 mAChR PAM, LY2033298, we report herein a systematic structure-activity relationship (SAR) study investigating different linkage points, halogen replacements to examine size and electronic effects, and different substitution combinations on the thienopyridine scaffold. We applied an operational model of allosterism to determine values of functional affinity (KB), cooperativity (αβ) and intrinsic agonism (τB) for all compounds.