Retatrutide

Retatrutide is a first-in-class triple hormone receptor agonist that simultaneously activates three distinct metabolic receptors: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon. ⁽⁴⁾ Also known by its research designation LY3437943, Eli Lilly developed this novel metabolic compound and is currently the most advanced triple-receptor peptide in clinical development. Its triple-agonist mechanism distinguishes retatrutide from earlier single-agonist compounds like semaglutide (GLP-1 only) and dual-agonist compounds like tirzepatide (GIP/GLP-1), making it a next-generation investigational treatment that has drawn significant attention from the research community. ⁽⁸⁾

The peptide’s molecular architecture consists of a single continuous helical structure that enables it to bind all three receptor types. ⁽⁴⁾ Its pharmacological profile shows the highest potency at the human GIP receptor (EC50: 0.0643 nM), followed by the GLP-1 receptor (EC50: 0.775 nM), and the glucagon receptor (EC50: 5.79 nM). ⁽⁸⁾ This receptor binding hierarchy contributes to its distinctive metabolic profile. With a half-life of approximately 6 days, retatrutide supports once-weekly administration in clinical research protocols, delivered as a subcutaneous injection. ⁽⁵⁾

A common point of confusion in the research community is the informal term “GLP-3,” which has been used colloquially to describe retatrutide. There is no actual GLP-3 receptor in human physiology. The term is shorthand for the compound’s triple receptor activity and should not be confused with a novel receptor classification.

Retatrutide has generated exceptional research interest since Phase 2 trial results were published in the New England Journal of Medicine in 2023, demonstrating weight reductions that exceeded any previously reported pharmacological intervention. ⁽¹⁾ The compound has since progressed to an extensive Phase 3 clinical program (TRIUMPH) encompassing multiple indications beyond weight management, including type 2 diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD), obstructive sleep apnea, knee osteoarthritis, cardiovascular and renal outcomes, chronic low back pain, and Parkinson’s disease. ⁽⁶⁾

Healius supplies retatrutide as a lyophilized (also referred to as lyophilized in US research literature) powder in 5mg, 10mg, and 20mg vials, intended strictly for laboratory and research applications.

Retatrutide promotes weight reduction and metabolic improvement by engaging three complementary hormonal pathways simultaneously. ⁽⁴⁾ Each receptor component contributes distinct metabolic actions, and their combined activation produces effects greater than any single pathway can achieve alone. This triple-receptor approach represents the most advanced incretin-based mechanism currently under clinical investigation. ⁽⁸⁾

The GLP-1 receptor component is responsible for effects that are now well-characterized (also characterized in US literature) through approved GLP-1 agonists. Activation of this receptor suppresses appetite by acting on hypothalamic satiety centers, delays gastric emptying to promote fullness after meals, and enhances glucose-dependent insulin secretion from pancreatic beta cells. ⁽⁸⁾

The GIP receptor component, where retatrutide shows its highest potency, adds complementary metabolic actions. ⁽⁴⁾ GIP receptor activation enhances the insulin response to meals, influences fat metabolism in adipose tissue, and appears to contribute to improved lipid profiles. The success of tirzepatide, the first approved dual GIP/GLP-1 agonist, demonstrated that adding GIP agonism to GLP-1 activity produces substantially greater weight reduction and glycaemic (also spelled glycemic) improvement than GLP-1 alone.

The glucagon receptor component is the breakthrough element that sets retatrutide apart from all approved incretin therapies. ^(4,8) Traditionally viewed primarily as a counter-regulatory hormone that raises blood glucose, glucagon’s broader metabolic role is now recognized as considerably more complex. Glucagon receptor activation increases hepatic energy expenditure, promotes fat oxidation in the liver, enhances amino acid metabolism, and reduces hepatic lipid accumulation. ⁽³⁾ This last property is particularly relevant to the striking liver fat reductions observed in retatrutide trials. Glucagon agonism may also contribute to reductions in LDL cholesterol through effects on PCSK9 degradation, a mechanism distinct from statin-based pathways. ⁽¹⁾

The net result of this triple activation is a compound that simultaneously reduces caloric intake (GLP-1 and GIP), increases energy expenditure (glucagon), improves insulin sensitivity and glucose control (all three receptors), and promotes hepatic fat clearance (primarily glucagon). ⁽⁴⁾ Published research by Coskun et al. in Cell Metabolism ⁽²⁰²²⁾ provided the preclinical foundation demonstrating that this combination produced superior metabolic outcomes compared to single or dual receptor activation in animal models. ⁽⁴⁾

The weight management data for retatrutide represents the most striking clinical findings published for any investigational anti-obesity compound to date, with both short-term and long-term benefits documented across multiple trial phases. ^(1,7)

The Phase 2 trial, published by Jastreboff et al. in the New England Journal of Medicine ⁽²⁰²³⁾, enrolled 338 adults with obesity (BMI 30 or above) or overweight with at least one weight-related condition, but without type 2 diabetes. ⁽¹⁾ Participants received subcutaneous retatrutide at doses of 1mg, 4mg, 8mg, or 12mg, or placebo, once weekly for 48 weeks. The results were dose-dependent: at 48 weeks, mean percentage weight loss was 8.7% in the 1mg group, 17.1% in the 4mg group, 22.8% in the 8mg group, and 24.2% in the 12mg group, compared to 2.1% with placebo. ⁽¹⁾

At the highest dose, 100% of participants achieved at least 5% weight loss, 93% achieved at least 10%, and 83% achieved at least 15%. ⁽¹⁾ These response rates substantially exceeded those reported in pivotal trials for semaglutide and tirzepatide. Weight loss was accompanied by significant reductions in waist circumference, ranging from 6.5 to 19.6 cm across dose groups. ⁽¹⁾

Beyond body weight, the Phase 2 trial documented broad cardiometabolic improvements. Participants experienced reductions in systolic and diastolic blood pressure, fasting glucose, insulin levels, and hemoglobin A1c (also spelled hemoglobin), as well as multiple lipid parameters, including LDL cholesterol (approximately 20% reduction). ⁽¹⁾ Notably, 72% of participants who had prediabetes at baseline reverted to normoglycaemia during the trial, suggesting significant preventive potential for type 2 diabetes. ⁽¹⁾

The first Phase 3 results, from the TRIUMPH-4 trial announced by Eli Lilly in December 2025, evaluated retatrutide in adults with obesity and knee osteoarthritis over 68 weeks. ⁽⁶⁾ Participants receiving retatrutide 12mg lost an average of 28.7% of their body weight, equivalent to approximately 71.2 lbs. ⁽⁶⁾ The trial also demonstrated substantial reductions in osteoarthritis pain, with WOMAC pain scores decreasing by up to 75.8%. More than one in eight participants became completely free of knee pain by the end of the study. ⁽⁶⁾

Seven additional Phase 3 readouts from the TRIUMPH program are expected in 2026, providing the comprehensive efficacy and safety data required for regulatory submissions. ⁽⁶⁾

Beyond weight management, retatrutide has produced particularly compelling data in hepatic and metabolic research, areas where the glucagon receptor component appears to confer unique advantages over GLP-1-only or dual GIP/GLP-1 therapies. ⁽³⁾

A dedicated substudy of the Phase 2 obesity trial examined retatrutide’s effects on liver fat in 98 participants with metabolic dysfunction-associated steatotic liver disease (MASLD) and at least 10% liver fat at baseline. ⁽³⁾ Published by Sanyal et al. in Nature Medicine ⁽²⁰²⁴⁾, the results showed dramatic reductions: mean relative liver fat change at 24 weeks was -42.9% (1mg), -57.0% (4mg), -81.4% (8mg), and -82.4% (12mg), compared to +0.3% with placebo. All comparisons were statistically significant (p < 0.001). ⁽³⁾ At the highest doses, more than 90% of participants achieved complete normalization (also spelled normalization) of liver fat content.

These reductions in liver fat are the largest reported for any investigational therapy in MASLD, a condition for which no treatments are currently approved in the United States or Europe. ⁽³⁾ The glucagon receptor component is believed to be the primary driver, given glucagon’s well-documented role in hepatic lipid metabolism and fat oxidation. A dedicated Phase 3 MASLD trial is part of the TRIUMPH program. ⁽⁶⁾

In the type 2 diabetes Phase 2 trial, published by Rosenstock et al. in The Lancet ⁽²⁰²³⁾, 281 participants received retatrutide, dulaglutide (an active comparator), or placebo for 36 weeks. ⁽²⁾ HbA1c improved by up to 2.2% with retatrutide 12mg, with 77-82% of participants reaching euglycemia (HbA1c of 6.5% or below). ⁽²⁾ Weight loss in this population reached 16.9% at 36 weeks. Retatrutide demonstrated superiority over dulaglutide 1.5mg, a widely prescribed GLP-1 agonist, in both glycaemic control and weight reduction. ⁽²⁾

The TRIUMPH Phase 3 program also includes trials investigating cardiovascular and renal outcomes, as well as obstructive sleep apnea, reflecting the breadth of metabolic conditions in which triple receptor agonism may offer therapeutic value. ⁽⁶⁾ Separately, a clinical trial is evaluating retatrutide for Parkinson’s disease, driven by emerging evidence that GLP-1 class compounds may have neuroprotective properties.

1. Jastreboff AM, Kaplan LM, Frias JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526.

2. Rosenstock J, Frias J, Jastreboff AM, et al. Retatrutide, a GIP, GLP-1, and glucagon receptor agonist, for people with type 2 diabetes: a randomized, double-blind, placebo and active-controlled, parallel-group, phase 2 trial. Lancet. 2023;402(10401):529-544.

3. Sanyal AJ, Kaplan LM, Frias JP, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nature Medicine. 2024; 30:2037-2048.

4. Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: from discovery to clinical proof of concept. Cell Metabolism. 2022; 34:1234-1247.

5. Urva S, et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomized, multiple-ascending dose trial. Lancet. 2022; 400:1869-1881.

6. Eli Lilly and Company. Lilly’s triple agonist, retatrutide, delivered an average weight loss of up to 71.2 lbs, along with substantial relief from osteoarthritis pain, in the first successful Phase 3 trial. Press release. December 11, 2025.

7. Efficacy and safety of retatrutide, a novel GLP-1, GIP, and glucagon receptor agonist for obesity treatment: a systematic review and meta-analysis of randomized controlled trials. Baylor University Medical Center Proceedings. 2025.

8. Retatrutide — A Game Changer in Obesity Pharmacotherapy (review). Pharmaceuticals. 2025.

9. Triple Agonism-Based Therapies for Obesity (review). Current Cardiovascular Risk Reports. 2025.

10. Phase 2 trial results demonstrate benefits of retatrutide in obesity, type 2 diabetes, and NASH. ADA 83rd Scientific Sessions Meeting Report. 2023.

This product is sold strictly for laboratory and research use only. It is not intended for human or animal consumption. It is not a dietary supplement, food, drug, or cosmetic. It is not intended to diagnose, treat, cure, or prevent any disease or condition. The buyer assumes all responsibility for the lawful use of this product in accordance with all applicable local, state, national, and international laws and regulations. By purchasing this product, the buyer confirms that they are a qualified researcher or are purchasing on behalf of a research institution.