116.2 Discovery and Development of Novel M1 and M4 PAMs for the Treatment of Schizophrenia.

Abstract

Abstract Background: Multiple lines of evidence indicate that development of selective positive allosteric modulators (PAMs) of the M1 and M4 muscarinic acetylcholine receptor subtypes (mAChR) represent important novel therapeutic approaches for the complex symptoms associated schizophrenia. Over the last decade, Dr. Jones and colleagues at the Vanderbilt Center for Neuroscience Drug Discovery (VCNDD) have disclosed the discovery of several, selective mAChR PAMs, as represented by the M1 PAM VU6004256 and M4 PAM VU0467154. This presentation will focus on recent findings demonstrating the ability of M1 and M4 PAMs to reverse abnormalities in prefrontal cortical-mediated physiology, behaviors, and/or cognitive functions observed across preclinical models of N-methyl-D-aspartate subtype of the glutamate receptor (NMDAR) hypofunction, which are thought to underlie many of the symptoms observed in schizophrenia. Methods: Medicinal chemistry and high throughput screening methods were utilized to identify two different series of selective M1 and M4 PAMs, represented by VU6004256 and VU0467154. Disposition was determined in mouse and rat pharmacokinetic studies using LC/MS/MS quantitation. In vivo efficacy was determined across several mouse and rat models predictive of antipsychotic-like activity and enhancement of cognitive function, in particular using the genetic mouse model of global reduction in the NR1 subunit of the NMDAR (NR1 knockdown [KD]). Results: In vitro both VU6004256 and VU0467154 exhibit low nanomolar potency at M1 or M4, respectively, with no activity at the other mAChR subtypes up to 30 μM or significant off target activity at other GPRCs at 10 µM. These ligands are also highly brain penetrant with suitable pharmacokinetic properties for in vivo dosing. Both VU6004256 and VU0467154 produced dose-dependent reductions in preclinical models predictive of antipsychotic-like activity, including reversal of hyperlocomotion in the NR1 KD mice. In addition, the M1 PAM VU6004256 decreased excessive pyramidal neuron firing in layer V of the prefrontal cortex (PFC) in awake, freely moving NR1 KD mice, as well as reversed impairments in two PFC-mediated learning tasks observed in these mice. Interestingly, the M4 PAM VU0467154 also enhanced performance in preclinical models of associative learning and memory functions after acute and chronic dosing and induced state-dependent alterations in sleep architecture and arousal. Conclusion: Collectively, these findings indicate that VU6004256 and VU0467154 represent highly optimized M1 and M4 PAM tool compounds for the evaluation of the respective roles of these mAChR subtypes in vivo and provide further validation for the development of selective M1 and M4 PAMs for the treatment of the psychotic symptoms and cognitive impairments observed in schizophrenia.