2025 AMA Research Challenge – Member Premier Access

October 22, 2025

Virtual only, United States

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Abstract Title: Safety and Efficacy of CB1 Receptor Antagonists for Weight Reduction: A Meta-Analysis

Background: Obesity is a major public health issue that is linked to a variety of comorbidities and increasing healthcare costs. Several pharmacological agents, including cannabinoid type 1 (CB1) receptor antagonists, have been studied for weight management. CB1 receptor antagonists target the endocannabinoid system, which regulate appetite and metabolism, offering potential benefits for weight reduction. However, concerns about psychiatric side effects have limited their clinical use. This meta-analysis aims to evaluate the efficacy and safety of CB1 receptor antagonists in overweight and obese adults to inform the development of safer and more effective therapies.

Methods: We searched PubMed, Embase, CENTRAL, ClinicalTrials.gov, and other sources for randomized controlled trials comparing CB1 receptor antagonists with placebo. Eligible trials enrolled adults with a BMI of 25 kg/m² or higher and reported changes in weight, BMI, waist circumference, fasting glucose, LDL cholesterol, or adverse events. Data were analyzed using RevMan version 5.4, and risk of bias was assessed using the Cochrane RoB 2 tool.

Results: Sixteen randomized controlled trials involving 13,882 participants were included. CB1 receptor antagonists had significantly reduced body weight compared to placebo (MD = −3.05 kg; 95% CI = −3.34 to −2.76; p<0.00001; I² = 17%), and subgroup analysis showed similar effects in short- and long-term follow-up. Waist circumference also had a significant reduction (MD = −2.79 cm; 95% CI = −3.15 to −2.43; p<0.00001; I² = 0%). There was a small but statistically significant decrease in fasting plasma glucose (MD = −0.14 mmol/L; 95% CI = −0.26 to −0.01; p=0.03; I² = 60%), while LDL cholesterol had no change (MD = 0.01 mmol/L; 95% CI = −0.04 to 0.06; p=0.79; I² = 0%). The intervention group experienced a small increase in total adverse events (RR = 1.04; 95% CI = 1.03 to 1.06; p<0.00001; I² = 0%) and a marked increase in psychiatric-related discontinuation (RR = 2.26; 95% CI = 1.69 to 3.03; p<0.00001; I² = 0%). Risk of bias assessment indicated that although some studies were at low risk across all domains, a subset had high risk due to missing outcome data and concerns related to the selection of reported results.

Conclusion: CB1 receptor antagonists demonstrate moderate effectiveness for weight reduction and improvements in waist circumference and glycemic control. However, their clinical utility is limited by dose-dependent psychiatric side effects. Future therapies targeting peripheral CB1 receptors may offer safer alternatives.

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