Research guide
Retatrutide (LY-3437943): a scientific overview
Retatrutide is an investigational once-weekly triple agonist targeting the GLP-1, GIP and glucagon receptors, developed by Eli Lilly and studied in Phase 2 and Phase 3 clinical trials for obesity and metabolic disease.
For laboratory research use only. Not for human consumption, diagnostic or therapeutic use.
What is Retatrutide?
Retatrutide (development code LY-3437943) is a synthetic 39-amino-acid peptide engineered as a balanced triple agonist of the glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon receptors. It is administered subcutaneously and, in clinical studies, dosed once weekly thanks to a fatty-acid side chain that extends its plasma half-life.
Mechanism of action
- GLP-1 agonism — enhances glucose-dependent insulin secretion, slows gastric emptying, and reduces appetite via central pathways.
- GIP agonism — modulates lipid metabolism and complements GLP-1's insulinotropic effect.
- Glucagon agonism — increases resting energy expenditure and hepatic lipid oxidation, a distinguishing feature versus dual GLP-1/GIP agonists such as tirzepatide.
Published trial data
In the Phase 2 obesity trial published in the New England Journal of Medicine (Jastreboff et al., 2023), adults with obesity treated with Retatrutide 12 mg once weekly for 48 weeks lost, on average, approximately 24% of body weight versus placebo. A parallel Phase 2 study in type 2 diabetes reported dose-dependent reductions in HbA1c and body weight. The Phase 3 TRIUMPH program is ongoing and evaluates Retatrutide across obesity, type 2 diabetes and MASLD populations.
Reconstitution & storage
Lyophilised Retatrutide is typically reconstituted with bacteriostatic water for injection. A common working concentration is 5 mg per 1 mL, adjusted according to the vial strength and the experimental protocol. Reconstituted peptide should be stored at 2–8 °C, protected from light, and used within 28 days. Unreconstituted vials remain stable long-term at −20 °C.
The information above is provided for laboratory handling reference only.
Quality & purity
Retatrutide supplied by XCE Peptide is synthesised in European partner facilities operating under GMP-inspired protocols. Each batch is analysed by reversed-phase HPLC and confirmed by mass spectrometry; only batches above 99% purity are released. Randomised samples are cross-verified by an independent, accredited European laboratory and a certificate of analysis accompanies every order.
Sourcing Retatrutide in Europe
XCE Peptide ships Retatrutide from within the European Union with insured, tracked delivery in 2–4 working days. Orders are dispatched within 24 hours of on-chain payment confirmation, in neutral tamper-evident packaging.
Frequently asked questions
How does Retatrutide differ from tirzepatide?
Tirzepatide is a dual GLP-1 / GIP agonist. Retatrutide adds a third component, glucagon receptor agonism, which appears to increase energy expenditure in addition to the appetite and glycemic effects shared with dual agonists.
Is Retatrutide approved as a medicine?
No. As of 2026, Retatrutide is an investigational compound and has not received marketing authorisation from the EMA or FDA. It is supplied strictly for laboratory research.
What purity should a research-grade Retatrutide vial reach?
Research use typically requires ≥ 98% HPLC purity. XCE Peptide's release threshold is 99% and every batch ships with a certificate of analysis.