A Novel M1 PAM VU0486846 Exerts Efficacy in Cognition Models without Displaying Agonist Activity or Cholinergic Toxicity.

Abstract

Selective activation of the M1 subtype of muscarinic acetylcholine receptor, via positive allosteric modulation (PAM), is an exciting strategy to improve cognition in schizophrenia and Alzheimer's disease patients. However, highly potent M1 ago-PAMs, such as MK-7622, PF-06764427, and PF-06827443, can engender excessive activation of M1, leading to agonist actions in the prefrontal cortex (PFC) that impair cognitive function, induce behavioral convulsions, and result in other classic cholinergic adverse events (AEs). Here, we report a fundamentally new and highly selective M1 PAM, VU0486846. VU0486846 possesses only weak agonist activity in M1-expressing cell lines with high receptor reserve and is devoid of agonist actions in the PFC, unlike previously reported ago-PAMs MK-7622, PF-06764427, and PF-06827443. Moreover, VU0486846 shows no interaction with antagonist binding at the orthosteric acetylcholine (ACh) site (e.g., neither bitopic nor displaying negative cooperativity with [3H]-NMS binding at the orthosteric site), no seizure liability at high brain exposures, and no cholinergic AEs. However, as opposed to ago-PAMs, VU0486846 produces robust efficacy in the novel object recognition model of cognitive function. Importantly, we show for the first time that an M1 PAM can reverse the cognitive deficits induced by atypical antipsychotics, such as risperidone. These findings further strengthen the argument that compounds with modest in vitro M1 PAM activity (EC50 > 100 nM) and pure-PAM activity in native tissues display robust procognitive efficacy without AEs mediated by excessive activation of M1. Overall, the combination of compound assessment with recombinant in vitro assays (mindful of receptor reserve), native tissue systems (PFC), and phenotypic screens (behavioral convulsions) is essential to fully understand and evaluate lead compounds and enhance success in clinical development.

• Authors: Jerri M Rook, Jeanette L Bertron, Hyekyung P Cho, Pedro M Garcia-Barrantes, Sean P Moran, James T Maksymetz, Kellie D Nance, Jonathan W Dickerson, Daniel H Remke, Sichen Chang, Joel M Harp, Anna L Blobaum, Colleen M Niswender, Carrie K Jones, Shaun R Stauffer, P Jeffrey Conn, Craig W Lindsley
• Journal: ACS chemical neuroscience (ACS Chem Neurosci) Vol. 9 Issue 9 Pg. 2274-2285 (09 19 2018) ISSN: 1948-7193 [Electronic] United States
• PMID: 29701957 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Antipsychotic Agents
• Morpholines
• Pyrazoles
• VU0486846
• Risperidone

Topics

• Allosteric Regulation
• Animals
• Antipsychotic Agents (toxicity)
• CHO Cells
• Cognition (drug effects)
• Cognitive Dysfunction (chemically induced, physiopathology)
• Conditioning, Psychological (drug effects)
• Cricetulus
• Exploratory Behavior (drug effects)
• Fear
• Mice
• Morpholines (pharmacology, toxicity)
• Prefrontal Cortex (drug effects)
• Pyrazoles (pharmacology, toxicity)
• Rats
• Risperidone (toxicity)
• Seizures (chemically induced)