6-Phenylpyrimidin-4-ones as Positive Allosteric Modulators at the M1 mAChR: The Determinants of Allosteric Activity

Manuela Therese Jorg, Emma T van der Westhuizen, Elham Khajehali, Wessel Alexander Christian Burger, Jonathan White, Kwok Ho Christopher Choy, Andrew B. Tobin, Patrick Michael Sexton, Celine Valant, Benvenuto Capuano, Arthur Christopoulos, Peter John Scammells

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Targeting allosteric sites of the M 1 muscarinic acetylcholine receptor (mAChR) is an enticing approach to overcome the lack of receptor subtype selectivity observed with orthosteric ligands. This is a promising strategy for obtaining novel therapeutics to treat cognitive deficits observed in Alzheimer's disease and schizophrenia, while reducing the peripheral side effects such as seen in the current treatment regimes, which are non-subtype selective. We previously described compound 2, the first positive allosteric modulator (PAM) of the M 1 mAChR based on a 6-phenylpyrimidin-4-one scaffold, which has been further developed in this study. Herein, we present the synthesis, characterization, and pharmacological evaluation of a series of 6-phenylpyrimidin-4-ones with modifications to the 4-(1-methylpyrazol-4-yl)benzyl pendant. Selected compounds, BQCA, 1, 2, 9i, 13, 14b, 15c, and 15d, were further profiled in terms of their allosteric affinity, cooperativity with acetylcholine (ACh), and intrinsic efficacy. Additionally, 2 and 9i were tested in mouse primary cortical neurons, displaying various degrees of intrinsic agonism and potentiation of the acetylcholine response. Overall, the results suggest that the pendant moiety is important for allosteric binding affinity and the direct agonistic efficacy of the 6-phenylpyrimidin-4-one based M 1 mAChR PAMs.

Original languageEnglish
Pages (from-to)1099-1114
Number of pages16
JournalACS Chemical Neuroscience
Issue number3
Publication statusPublished - 20 Mar 2019


  • Alzheimer's disease
  • BQCA
  • M muscarinic acetylcholine receptor
  • positive allosteric modulator
  • pyrimidinones
  • schizophrenia

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