Educational Reference · Research-Use-Only
Retatrutide: Mechanism, Research, and Regulatory Status
Listed in the Veridian catalog as GLP-3 RT.
A research-grade overview of Retatrutide: what it is, how it works at the molecular level, what published studies have shown, and answers to the questions researchers ask most.
Last reviewed 2026-07-28
What is Retatrutide?
GLP-3(RT) (LY3437943) is a synthetic unimolecular triple agonist: a single molecule that switches on three receptors at once. Those receptors are the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GcgR). GLP-1R agonism suppresses appetite via hypothalamic satiety signaling, slows gastric emptying (how quickly the stomach empties), and potentiates glucose-stimulated insulin secretion.
GIPR agonism augments incretin-mediated insulin release. It may also directly potentiate the appetite-suppressing (anorectic) effects of GLP-1 through central and peripheral synergy. The third arm, glucagon receptor agonism, is what distinguishes GLP-3(RT) from dual GLP-1/GIP agents.
GcgR activation increases hepatic glucose output, elevates resting energy expenditure via brown adipose tissue thermogenesis (heat production in brown fat), promotes hepatic lipid oxidation, and suppresses appetite through independent CNS circuits. Preclinical data in diet-induced obese rodents showed that the triple agonist combination produced substantially greater weight reduction than any dual-agonist pair, which suggests the three arms contribute in non-redundant ways. The compound is currently in Phase 3 (TRIUMPH program) following its Phase 2 results.
One molecule, three receptors
GLP-3 (RT) is a triple agonist. That means a single molecule switches on three different receptors at once, and each one does a different job. Tap a receptor to see what it does.
GLP-1R
Glucagon-like peptide-1 receptor
- Reduces appetite through satiety signalling in the hypothalamus
- Slows how quickly the stomach empties
- Increases insulin release when glucose is already elevated
Research highlights
What published peer-reviewed research and preclinical studies have established about Retatrutide:
- 01Triple agonist targeting GLP-1, GIP, and glucagon receptors at the same time. This is a mechanistically distinct approach from existing approved agents
- 02Phase 2 TRIUMPH-2 trial (NEJM 2023, n=338, 48 weeks): high-dose arm (12 mg) achieved mean 17.5% body weight reduction vs 1.6% with placebo
- 03Lancet 2023 T2D trial (n=281, 36 weeks): GLP-3(RT) 12 mg reduced HbA1c by −2.02% vs −0.54% placebo; 26% of participants achieved normoglycemia
- 04Glucagon receptor activation drives energy expenditure and hepatic lipid oxidation. These effects are not observed with GLP-1 monotherapy
- 05Phase 3 TRIUMPH program (ongoing): large RCTs evaluating weight loss, T2D outcomes, obesity with cardiovascular disease, and NASH/metabolic-associated steatohepatitis
- 06Animal data show dose-dependent reductions in liver fat, triglycerides, and visceral adipose tissue beyond what dual agonists produce
- 07Approximately 26% of participants in the Phase 2 obesity trial achieved ≥20% weight loss. That threshold is rarely seen with any pharmacotherapy
Published clinical and preclinical research
TRIUMPH-2 (Obesity)
Phase 2 RCT · 202312 mg dose: −17.5% body weight vs −1.6% placebo (p<0.001); 4 mg: −8.7%; 8 mg: −12.9%
TRIUMPH T2D (Lancet)
Phase 2 RCT · 202312 mg: HbA1c −2.02% vs −0.54% placebo; fasting glucose −3.8 mmol/L; 26% achieved normoglycemia
Preclinical triple agonist discovery
Preclinical · 2022LY3437943 produced ~50% greater fat mass reduction vs matched dual GLP-1/GIP agonist in DIO mice; restored normoglycemia
Frequently asked questions about Retatrutide
How does GLP-3(RT) differ from tirzepatide (Mounjaro)?+
Tirzepatide activates GLP-1 and GIP receptors (dual agonist). GLP-3(RT) adds glucagon receptor agonism as a third arm, which may drive greater energy expenditure and hepatic fat clearance. In Phase 2, GLP-3(RT)'s top dose achieved ~17.5% weight loss vs tirzepatide's ~20–22.5% at 72 weeks (SURMOUNT-1), though direct head-to-head comparisons don't yet exist. GLP-3(RT) remains investigational; tirzepatide is FDA-approved.
What is the reconstitution protocol for research use?+
Reconstitute lyophilized GLP-3(RT) with bacteriostatic water (benzyl alcohol 0.9%). Add diluent slowly down the vial wall and do not shake. Gently invert or roll instead. The reconstituted solution should be clear and colorless. Store reconstituted peptide at 2–8°C and use within 28 days. Avoid freeze-thaw cycles after reconstitution.
How should lyophilized GLP-3(RT) be stored?+
Unopened lyophilized vials: −20°C in a light-proof container, away from moisture. Under ideal conditions, lyophilized peptides maintain integrity for 24+ months. Allow vials to equilibrate to room temperature before opening to prevent condensation. Do not store near desiccant packs that could absorb moisture from adjacent vials.
What Phase 3 trials are currently underway?+
The TRIUMPH Phase 3 program includes trials in: (1) obesity without diabetes (TRIUMPH-1), (2) type 2 diabetes (TRIUMPH-3, 4), (3) obesity with established cardiovascular disease (TRIUMPH-CVOT), and (4) metabolic-associated steatohepatitis / NASH. Eli Lilly has not published primary Phase 3 results as of early 2026; interim data are expected through 2026–2027.
Is GLP-3(RT) legal to purchase for research?+
GLP-3(RT) is an investigational compound not approved for therapeutic use in any jurisdiction. In many countries, purchase of unscheduled research peptides for legitimate laboratory research is not explicitly prohibited, but regulations vary by country and state. Researchers should review local regulations and institutional policies. GLP-3(RT) is prohibited in competitive sport by WADA (S2 classification).
Are there cardiovascular risks to consider in research models?+
Glucagon receptor agonism raises heart rate and cardiac output. In Phase 2, mean heart rate increased ~5–7 bpm in high-dose groups, similar to or slightly greater than GLP-1 monotherapy. Dedicated CVOT data are pending. Preclinical models do not suggest direct cardiotoxicity, but researchers studying cardiovascular endpoints should account for these hemodynamic effects.
Can GLP-3(RT) be stacked with other GLP-1 agonists in research?+
Co-administration with other GLP-1 or GIP receptor agonists is not recommended in research protocols due to additive GI side effects and risk of receptor desensitization. GLP-3(RT) already covers all three receptor axes relevant to incretin-based obesity research. Combination with SGLT-2 inhibitors or metformin has been used in T2D protocols, but the research context should guide design.
What endpoints are most relevant when studying GLP-3(RT) in vitro?+
Relevant in vitro endpoints include: cAMP accumulation in GLP-1R-, GIPR-, and GcgR-expressing cell lines; insulin secretion in MIN6 or INS-1 pancreatic beta cells; lipolysis in 3T3-L1 adipocytes; and fatty acid oxidation rates in primary hepatocytes. Binding affinity assays (radioligand displacement) at all three receptor subtypes provide important mechanistic characterization data.
References & sources
Every citation below was resolved against its primary source before publication. Each PMID was checked against its PubMed record and each DOI through doi.org. Follow any link to read the paper at the publisher rather than taking our summary on trust.
- [1]Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial. New England Journal of Medicine. 2023. PMID: 37351564 DOI: 10.1056/NEJMoa2301972
- [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 randomised, double-blind, placebo and active-comparator-controlled, parallel-group, phase 2 trial. The Lancet. 2023. PMID: 37385280 DOI: 10.1016/S0140-6736(23)01053-X
- [3]Coskun T, Urva S, Roell WC, 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. PMID: 35985340 DOI: 10.1016/j.cmet.2022.07.013
- [4]Müller TD, Blüher M, Tschöp MH, DiMarchi RD. Anti-obesity drug discovery: advances and challenges. Nature Reviews Drug Discovery. 2022. PMID: 34815532 DOI: 10.1038/s41573-021-00337-8
- [5]Finan B, Yang B, Ottaway N, et al. A rationally designed monomeric peptide triagonist corrects obesity and diabetes in rodents. Nature Medicine. 2015. PMID: 25485909 DOI: 10.1038/nm.3761
- [6]Drucker DJ. The biology of incretin hormones. Cell Metabolism. 2006. PMID: 16490548 DOI: 10.1016/j.cmet.2006.01.004
Where this data comes from
- Citations & trial data: PubMed (NCBI, U.S. National Library of Medicine), Crossref and ClinicalTrials.gov.
- Chemical identity: PubChem and UniProt. Where sources conflicted, the disputed value is omitted rather than guessed.
- Regulatory status: U.S. FDA publications and, where applicable, the WADA Prohibited List. Compounding status changes often, so check FDA directly before relying on it.
- Purity, form and storage are handling and supplier conventions, not literature-derived values. Confirm against the lot-specific certificate of analysis.
Content last reviewed 2026-07-28. Compiled by Veridian Research from the primary literature. This page is an educational reference for laboratory researchers. It is not medical advice, and it describes no human use.
Regulatory status
GLP-3(RT) (LY3437943) is an investigational compound currently in Phase 3 clinical trials. It has not been approved by the FDA or any regulatory agency for therapeutic use in humans. It is classified as a prohibited substance under WADA S2 (Peptide Hormones, Growth Factors, Related Substances). For research purposes only.
Research-Use-Only Material
Specifications and certificate of analysis
Retatrutide is stocked as a research reagent. The most recent batch (2026-03) was analysed by Janoshik Analytical at 99.58% purity; the signed certificate is published in full.