Retatrutide: What the Research Shows
Retatrutide is a triple hormone receptor agonist — a single molecule engineered to activate three separate receptor pathways simultaneously: GIP, GLP-1, and glucagon. It’s the first compound of its kind to reach late-stage human trials, building on the dual-agonist approach used by tirzepatide with the addition of glucagon receptor activity, which researchers believe may account for some of its distinctive effects on liver fat and energy expenditure.
Weight Management
The pivotal Phase 2 trial, published in the New England Journal of Medicine, tested retatrutide in adults with obesity over 48 weeks. Researchers found weight reductions of up to 24.2% at the highest dose tested — among the largest effect sizes reported for any pharmacological weight-management therapy at the time of publication. Participants also saw improvements in blood pressure, glycated hemoglobin, fasting glucose, insulin, and most lipid measures, and 72% of participants with prediabetes at baseline reverted to normal glucose regulation by the end of the trial (Jastreboff et al., Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial, NEJM, 2023).
Liver Fat Reduction
A related substudy examined retatrutide’s effect on liver fat specifically, in participants with metabolic dysfunction-associated steatotic liver disease (MASLD). Researchers found dose-dependent reductions in liver fat of up to 82.4% at 24 weeks — a substantially larger effect than has been reported for dual-agonist or single-agonist incretin therapies, which researchers attribute in part to the added glucagon receptor activity (Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized Phase 2a trial, Nature Medicine, 2024).
Emerging Phase 3 Data
More recently, Eli Lilly reported topline results from TRIUMPH-4, a Phase 3 trial evaluating retatrutide in adults with obesity and knee osteoarthritis. The trial reported average weight loss of up to 71.2 pounds at the highest doses tested, alongside improvements in osteoarthritis pain — the company’s first successful Phase 3 readout for the compound (Lilly’s triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial, Eli Lilly and Company, 2025).
Proposed Mechanism
Research attributes retatrutide’s effects to the combined action of its three receptor targets:
- GLP-1 and GIP receptor activation work similarly to how they function in dual-agonist therapies like tirzepatide — slowing gastric emptying and supporting glucose-dependent insulin secretion
- Glucagon receptor activation is the feature unique to retatrutide among approved and late-stage incretin therapies, and researchers believe it contributes to increased energy expenditure and the pronounced liver fat reduction observed in trials
- LDL cholesterol reduction of roughly 20% was observed in the Phase 2 trial, which researchers have hypothesized may relate to glucagon agonism’s effects on a protein called PCSK9, though this mechanism is not yet fully established
Regulatory Status
Unlike tirzepatide, semaglutide, and tesamorelin, retatrutide is not yet FDA-approved — it remains an investigational compound in active Phase 3 clinical development.
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View RetatrutideThis overview reflects published Phase 2 and emerging Phase 3 clinical trial research. Products offered by Core Molecular Solutions are intended for laboratory research purposes only and are not for human or veterinary use.