Triple Agonism Based Therapies for Obesity.

Abstract

Glucagon-like peptide 1 (GLP-1) receptor agonists (RA) have transformed obesity and type 2 diabetes (T2D) management. Tirzepatide, the first dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) RA approved for both conditions, has paved the way for next-generation incretin-based therapies. Among these, triple agonists targeting GLP-1, GIP, and glucagon receptors represent a promising next step. This review outlines the rationale for their development and summarizes clinical trial data, focusing on retatrutide, the most advanced candidate. Retatrutide is the first triple agonist (acting on GLP-1/GIP/glucagon receptors) with published phase 2 data in people with obesity as well as in people with T2D. Retatrutide achieved up to 24.2% mean weight loss after 48 weeks in individuals with obesity and 16.9% in those with T2D after 36 weeks. In the T2D study, HbA1c improved by 2.2%, with 82% of participants reaching HbA1c ≤ 6.5%. Retatrutide also improved multiple cardiometabolic parameters, including blood pressure, lipids, waist circumference, and liver fat (82% reduction in hepatic steatosis). Gastrointestinal symptoms were the most common side effects; no major safety concerns were observed. A comprehensive phase 3 program is ongoing to evaluate efficacy, safety, and cardiovascular/renal outcomes in people with obesity and/or T2D. Other unimolecular triple agonists and combination regimens involving tirzepatide with additional mono agonists are also in development. Retatrutide, a triple agonist now in phase 3 trials, has the potential to become the most effective pharmacological treatment for obesity while also offering substantial benefits in T2D management and other cardiometabolic risk factors.