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Vanderbilt Addiction Center

Selective M1 mAChR allosteric modulators for the treatment of schizophrenia

Over 50 years ago, antimuscarinic agents were shown to induce a psychotic state in humans similar to schizophrenia and exacerbate existing symptoms in schizophrenic patients. At about this time, muscarinic agonists were shown to be moderately effective as neuroleptic agents, which gave rise a cholinergic hypothesis of schizophrenia, decades before the now prevalent hyperdopaminergic hypothesis. Recent preclinical and Phase III clinical data further strengthens the cholinergic hypothesis by demonstrating that muscarinic acetylcholine receptor (mAChR) agonists, such as the pan-muscarinic agonist xanomeline, are effective in improving cognition and reducing psychotic symptoms in schizophrenic and Alzheimer's disease (AD) patients. However, the clinical utility of of mAChR agonists has been limited due to intolerable side effects resulting from a lack of mAChR subtype selectivity. The development of subtype selective muscarinic agonists has been difficult to the highly conserved orthosteric binding site for acetylcholine (ACh) among the five muscarinic receptor subtypes (M1-M5). We have identified and plan to develop novel, selective allosteric agonists and potentiators of the M1 mAChR that activate the receptor through an allosteric binding site that is topologically distinct from the orthosteric binding site. Since mounting evidence suggests that the cognitive, antipsychotic and Ab lowering effects of cholinergic agents are mediated by the M1 mAChR subtype, we have performed a high throughput screen to identify M1 potentiators and allosteric agonists. This effort afforded small molecule M1 potentiators and M1 allosteric agonist leads representing multiple new chemotypes. While a significant accomplishment, these screening leads will require several rounds of chemical lead optimization in order to produce M1 allosteric agonists and M1 potentiators suitable as proof of concept tools to study in vivo. In addition, we have made significant progress in the evaluation of TBPB, a highly selective and potent M1 allosteric agonist in vivo, which further supports our strategy of pursuing selective M1 activation as a treatment for schizophrenia. This research has direct relevance to the mission of NIMH and has the potential to impact human health directly. Our goal for this project is to develop, in parallel, selective M1 allosteric agonists and M1 positive allosteric modulators with acceptable profiles for preclinical and ultimately clinical development that may lead to a new drug for the treatment of the positive, negative and cognitive symptoms of schizophrenia. PUBLIC HEALTH RELEVANCE: Recent preclinical and Phase III clinical data has shown that muscarinic acetylcholine receptor (mAChR) agonists, such as the pan-muscarinic agonist xanomeline, are effective in improving cognition and reducing psychotic symptoms in schizophrenic and Alzheimer's disease (AD) patients. We have completed a high throughput screen, identified and plan to develop novel, selective allosteric agonists and potentiators of the M1 mAChR that activate the receptor through a novel binding site which affords complete, unprecedented selectivity for M1 versus M2-M5. Our goal for this project is to develop, in parallel, selective M1 allosteric agonists and M1 positive allosteric modulators with acceptable profiles for preclinical and ultimately clinical development that may lead to a new drug for the treatment of the positive, negative and cognitive symptoms of schizophrenia.

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