Buy Retatrutide: Triple Agonist Peptide for Research
Retatrutide (LY-3437943) in research-grade quality. EU shipping, batch certificates of analysis. Everything about the GLP-1/GIP/glucagon triple agonist.
Retatrutide (LY-3437943) is an investigational unimolecular peptide that activates three receptors at once: GLP-1, GIP and glucagon. That sets it apart from semaglutide, which acts only on GLP-1, and tirzepatide, which combines GLP-1 and GIP. It is one of the most-watched compounds in current metabolic peptide research.
First-ever triple-action weight management peptide targeting three receptors at once: GLP-1, GIP, and glucagon. Shown exceptional results in Phase 2 trials - up to 24% weight reduction. The most advanced metabolic peptide available.
A first-in-class dual GIP and GLP-1 receptor agonist, and one of the most extensively studied compounds in modern metabolic and weight-regulation research. Supplied as a lyophilised research peptide with a per-batch certificate of analysis, for laboratory and in-vitro use only.
As of June 2026: the current Phase 3 picture
TRIUMPH-1 (ADA, June 2026): Lilly reported that participants assigned to 12 mg in the TRIUMPH-1 obesity trial had a mean 28.3% weight reduction at 80 weeks. Details in the article Retatrutide TRIUMPH-1. TRANSCEND-T2D-1 (Lancet, June 2026): The first Phase 3 trial in type 2 diabetes lowered HbA1c by up to roughly 2.0 points as monotherapy, with up to 16.8% weight loss. Details in the article Retatrutide in type 2 diabetes. Approval: still none. The Phase 3 program reads out over the course of 2026, and any possible approval would come in 2027 at the earliest. Until then, Retatrutide has no marketing authorisation and is not an approved medicine.
What is Retatrutide?
Retatrutide is a synthetic peptide from Eli Lilly, currently in clinical trials. What makes it special: it is a so-called triple agonist - a single molecule that binds to three different receptors.
GLP-1 (Glucagon-like Peptide-1) controls insulin secretion and appetite regulation. This receptor is also activated by semaglutide and tirzepatide.
GIP (Glucose-dependent Insulinotropic Polypeptide) influences insulin sensitivity and fat metabolism. Tirzepatide also uses this pathway; semaglutide does not.
Glucagon receptor activity is studied for effects on energy expenditure, lipolysis and thermogenesis. This third receptor is addressed only by retatrutide among the currently prominent peptides, which is its distinguishing feature.
Glucagon as the Key
Glucagon was long regarded as a pure antagonist of insulin. Current research paints a more nuanced picture: investigators hypothesise that controlled glucagon receptor activation may increase energy expenditure alongside the glucose-lowering effect of concurrent GLP-1 activity. This is an effect under study, not an established human outcome.
Research Data on Retatrutide
Clinical Trials
Phase 2 Results (NEJM, 2023)
338 participants, randomised, double-blind, placebo-controlled, over 48 weeks. The highest dose group reported a mean weight reduction of about 24% of body weight. Separate trials of semaglutide and tirzepatide reported roughly 15% and 21%; those are different trials with different populations, not a head-to-head comparison. The most common side effects were gastrointestinal (nausea, diarrhoea, vomiting), similar to other GLP-1 agonists.
Phase 3 Results: TRIUMPH-4 (December 2025)
In December 2025, Eli Lilly reported topline TRIUMPH-4 results. In participants with obesity and knee osteoarthritis, the 12 mg arm showed a mean weight reduction of up to 32.3 kg (71.2 lbs) at 68 weeks, alongside reduced WOMAC knee-pain scores and improved cardiovascular risk markers such as non-HDL cholesterol and systolic blood pressure. These are sponsor-reported topline figures, not a peer-reviewed publication. The TRIUMPH programme includes over 5,800 participants across four Phase 3 studies, and further results are expected in 2026.
Single-, Dual- and Triple-Receptor Agonists
These peptides differ by how many receptors they target. Semaglutide (Ozempic/Wegovy) targets the GLP-1 receptor and reported roughly 15% weight reduction in its trials. Tirzepatide (Mounjaro/Zepbound) targets GLP-1 and GIP and reported around 21%. Retatrutide targets all three, GLP-1, GIP and glucagon, and reported approximately 24% in its own trial. These percentages come from separate trials with different populations and durations, so they cannot be ranked against each other without a head-to-head study.
Further Research Directions
Weight research is only one aspect. Retatrutide is also being investigated in metabolic dysfunction-associated steatotic liver disease (MASLD) and its more severe form MASH (formerly NASH). Early data reported reductions in measured liver fat content. Further studies address improvement of glycaemic control in type 2 diabetes, cardiovascular markers such as blood pressure and lipid profile, and exploratory investigations into sleep apnoea.
Why Buy Retatrutide at PeptidesDirect?
Published Certificates of Analysis
Each batch of retatrutide has a published Certificate of Analysis. Depending on the batch this is a manufacturer-sourced Janoshik report or a community-submitted report, labelled by source on our lab reports page, each with a verification link so the result can be checked against the testing lab rather than against us. We do not commission these reports ourselves and do not operate a laboratory. The certificate confirms identity by mass spectrometry and reports the measured HPLC purity for that specific batch.
EU Shipping without Customs
PeptidesDirect ships from within the European Union. Intra-community delivery means no import duties within the EU. Delivery time to most EU countries is two to three business days, with tracking and in discreet, neutral packaging.
First-ever triple-action weight management peptide targeting three receptors at once: GLP-1, GIP, and glucagon. Shown exceptional results in Phase 2 trials - up to 24% weight reduction. The most advanced metabolic peptide available.
Retatrutide in Comparison
Triple-receptor agonism (GLP-1, GIP, glucagon)
Amylin pathway & combination research
Compared to Tirzepatide
The approved drug tirzepatide (Mounjaro/Zepbound) activates two receptors, GLP-1 and GIP. Retatrutide adds the glucagon receptor. This third signalling pathway could increase energy expenditure more strongly than the dual approach alone. In their separate trials, retatrutide reported roughly 24% and tirzepatide roughly 21% weight reduction. Because the trials differ in population and duration and no head-to-head trial has compared them, these figures cannot be read as a ranking of one against the other.
Compared to Semaglutide
The approved drug semaglutide (Ozempic/Wegovy) is the best-known GLP-1 agonist and acts exclusively on GLP-1 receptors. Retatrutide has a broader spectrum of action. The advantage of semaglutide lies in its considerably longer clinical experience and existing approval. Retatrutide is still in Phase 3 studies.
Further GLP-1 Peptides
The research landscape is evolving rapidly.
Practical Research Notes
Reconstitution
Retatrutide is a lyophilised powder.
Prepare bacteriostatic water
Use bacteriostatic water for reconstitution - not regular water or sterile saline.
Add water slowly
Inject the water slowly along the glass wall of the vial. Do not aim directly at the lyophilised powder.
Swirl gently
Swirl gently rather than shaking. The solution should be completely clear before use.
Store cool
After reconstitution, store in the refrigerator at 2-8 °C and follow the batch-specific stability information rather than a fixed duration.
Storage
Before reconstitution, store at -20 °C in the freezer. Always protect from light and moisture. More detailed guidance is available in the Peptide Storage Guide.
USP-grade sterile water with 0.9% benzyl alcohol (near-neutral, ~pH 6) - the standard solvent for reconstituting lyophilized peptides. Essential accessory for any peptide research. Each vial is sealed and ready to use.
Frequently Asked Questions about Retatrutide
Conclusion
Retatrutide is an investigational triple agonist that unites GLP-1, GIP and glucagon in a single molecule. Its trials reported weight-reduction figures in the low-to-mid 20 percent range; because the trials differ, these cannot be ranked against other agents without a head-to-head study. For metabolic research it is studied as a distinct tool from mono- and dual agonists.
First-ever triple-action weight management peptide targeting three receptors at once: GLP-1, GIP, and glucagon. Shown exceptional results in Phase 2 trials - up to 24% weight reduction. The most advanced metabolic peptide available.
Research context for English-speaking buyers
Most of our English-speaking customers ship to the UK, Ireland, Malta or other English-as-second-language EU territories. The regulatory picture differs per country.
- Relevant authorities
- MHRA (UK, post-Brexit), HPRA (Ireland, EU-aligned), FDA Section 503A bulks list (US, restricted Cat 2 status of several peptides as of 2026)
- Customs and VAT
- EU shipments include 19% VAT; UK shipments after Brexit are now extra-EU and may attract UK VAT plus a handling fee at import
- Typical shipping window
- EU 2-4 working days, UK 4-7 working days, other international 7-14 working days, depending on customs
Research-grade peptides shipped from our EU warehouse are sold for laboratory use only and are not authorised for human or veterinary therapeutic application in any of the destination jurisdictions. US customers should be aware that the FDA Section 503A bulks list classification (and the April 2026 reclassification of twelve compounds) only governs compounding pharmacies, not direct-to-researcher imports for non-clinical work. UK buyers should declare the consignment on import and may be asked for a research justification by HMRC. We provide a CoA per batch identified by colour code rather than serial number; customs sometimes asks for this document when clearing the parcel.