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Brandt AL, Garai S, Zagzoog A, Hurst DP, Stevenson LA, Pertwee RG, Imler GH, Reggio PH, Thakur GA, Laprairie RB. Pharmacological evaluation of enantiomerically separated positive allosteric modulators of cannabinoid 1 receptor, GAT591 and GAT593. Front Pharmacol 2022; 13:919605. [PMID: 36386195 PMCID: PMC9640980 DOI: 10.3389/fphar.2022.919605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 10/07/2022] [Indexed: 11/09/2023] Open
Abstract
Positive allosteric modulation of the type 1 cannabinoid receptor (CB1R) has substantial potential to treat both neurological and immune disorders. To date, a few studies have evaluated the structure-activity relationship (SAR) for CB1R positive allosteric modulators (PAMs). In this study, we separated the enantiomers of the previously characterized two potent CB1R ago-PAMs GAT591 and GAT593 to determine their biochemical activity at CB1R. Separating the enantiomers showed that the R-enantiomers (GAT1665 and GAT1667) displayed mixed allosteric agonist-PAM activity at CB1R while the S-enantiomers (GAT1664 and GAT1666) showed moderate activity. Furthermore, we observed that the R and S-enantiomers had distinct binding sites on CB1R, which led to their distinct behavior both in vitro and in vivo. The R-enantiomers (GAT1665 and GAT1667) produced ago-PAM effects in vitro, and PAM effects in the in vivo behavioral triad, indicating that the in vivo activity of these ligands may occur via PAM rather than agonist-based mechanisms. Overall, this study provides mechanistic insight into enantiospecific interaction of 2-phenylindole class of CB1R allosteric modulators, which have shown therapeutic potential in the treatment of pain, epilepsy, glaucoma, and Huntington's disease.
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Affiliation(s)
- Asher L. Brandt
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
| | - Sumanta Garai
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Boston, MA, United States
| | - Ayat Zagzoog
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
| | - Dow P. Hurst
- Center for Drug Discovery, University of North Carolina Greensboro, Greensboro, NC, United States
| | - Lesley A. Stevenson
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
| | - Roger G. Pertwee
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
| | - Gregory H. Imler
- Centre for Biomolecular Science and Engineering, Naval Research Laboratory, Washington, DC, United States
| | - Patricia H. Reggio
- Center for Drug Discovery, University of North Carolina Greensboro, Greensboro, NC, United States
| | - Ganesh A. Thakur
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Boston, MA, United States
| | - Robert B. Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
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Abstract
Allosteric modulation of the type 1 cannabinoid receptor (CB1R) holds great therapeutic potential. This is because allosteric modulators do not possess intrinsic efficacy, but instead augment (positive allosteric modulation) or diminish (negative allosteric modulation) the receptor's response to endogenous ligand. Consequently, CB1R allosteric modulators have an effect ceiling which allows for the tempering of CB1R signaling without the desensitization, tolerance, dependence, and psychoactivity associated with orthosteric compounds. Pain, movement disorders, epilepsy, obesity are all potential therapeutic targets for CB1R allosteric modulation. Several challenges exist for the development of CB1R allosteric modulators, such as receptor subtype specificity, translation to in vivo systems, and mixed allosteric/agonist/inverse agonist activity. Despite these challenges, elucidation of crystal structures of CB1R and compound design based on structure-activity relationships will advance the field. In this review, we will cover recent progress for CB1R allosteric modulators and discuss the future promise of this research.
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Affiliation(s)
- Mariam Alaverdashvili
- a College of Pharmacy and Nutrition , University of Saskatchewan , Saskatoon , Canada
| | - Robert B Laprairie
- a College of Pharmacy and Nutrition , University of Saskatchewan , Saskatoon , Canada
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