New peripherally-restricted CB1 receptor antagonists, PMG-505–010 and −013 ameliorate obesity-associated NAFLD and fibrosis

Abstract

The endocannabinoid system plays a crucial role in metabolic regulation, prompting the investigation of cannabinoid type 1 receptor (CB1R) antagonists for obesity and its complications like non-alcoholic fatty liver disease (NAFLD). Concerns over psychiatric side effects led to the development of peripheral CB1R antagonists that circumvent the blood-brain barrier (BBB). In this study, we synthesized PMG-505–010 and PMG-505–013 as peripherally restricted CB1 receptor antagonists by modifying rimonabant to minimize BBB penetration. Physicochemical analysis confirmed their reduced lipophilicity and increased polarity compared to rimonabant, indicating limited brain exposure. Molecular docking studies revealed similar binding modes to rimonabant at CB1R, characterized by robust hydrophobic interactions. Functionally, they acted as CB1R antagonists and inverse agonists, effectively reversing CP55,940-induced cAMP inhibition. In a murine model of obesity-related NAFLD, PMG-505–010 and −013 improved metabolic profiles, including fasting blood glucose levels and dyslipidemia. They also ameliorated hepatic injury, steatosis, and inflammation, evidenced by reduced liver enzymes, lipid peroxidation, hepatic lipid levels, and inflammatory cytokine levels. Notably, these compounds inhibited hepatic fibrosis by reducing extracellular matrix (ECM) deposition and altering fibrosis-related gene and protein expressions. In conclusion, PMG-505–010 and PMG-505–013 hold promise for treating obesity-related liver diseases, including NAFLD and fibrosis, through selective peripheral CB1R targeting, potentially avoiding CNS-related side effects seen with earlier CB1R antagonists.

Keywords

• Cannabinoid type 1 receptor (CB1R) antagonists
• peripheral CB1R targeting
• nonalcoholic fatty liver disease (NAFLD)
• hepatic fibrosis
• Endocannabinoid system