Novel Cannabinoid Receptor 1 Inverse Agonist CRB-913 Enhances Efficacy of Tirzepatide, Semaglutide, and Liraglutide in the Diet-induced Obesity Mouse Model

Objective: Incretin receptor agonists are now standard of care in treating obesity. Their efficacy and tolerability might be further improved by combining them with compounds that offer orthogonal mechanisms of action. The cannabinoid type 1 receptor (CB1R) is a clinically validated therapeutic target in obesity, and several experimental CB1R inverse agonists have been shown to induce weight loss. Methods: This study characterizes a novel CB1R inverse agonist (CRB-913) with similar preclinical potency to rimonabant but markedly reduced brain penetration. CRB-913 was tested as monotherapy and in combination with tirzepatide, semaglutide, or liraglutide in the diet-induced obesity (DIO) mouse model for body weight reduction. Results: CRB-913 demonstrated enhanced plasma exposure (3.8-fold larger area under the curvelast) and reduced brain levels (9.5-fold lower area under the curvelast) than rimonabant. CRB-913 monotherapy yielded a dose-dependent decrease in body weight in DIO mice reaching _22% within 18 days. In further DIO studies in combination with tirzepatide, semaglutide, or liraglutide, CRB-913 (2.5 mg/kg) resulted in -32.6%, -28.8%, and -16.8% decreases in body weight on Day 18, respectively, with concomitant improvements in body fat content, liver triglycerides, and liver fat deposits. Conclusions: CRB-913 in combination with incretin analogues could deliver meaningful improvements over current standards of care for obesity and related conditions.