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Retatrutide: A Research Guide to the Triple GLP-1 / GIP / Glucagon Agonist
Short answer: retatrutide (LY3437943) is a 39-amino-acid synthetic peptide developed by Eli Lilly - the first investigational triple-receptor agonist to reach late-stage clinical trials. It simultaneously activates the GLP-1, GIP and glucagon receptors. Phase 2 data (NEJM, 2023) reported mean body-weight reduction of ~24% over 48 weeks at the 12 mg weekly dose - the largest incretin-class effect on record. It is currently in the Phase 3 TRIUMPH programme and has no marketing authorisation anywhere in the world . New-U catalogues research-grade retatrutide as Retatrutide - lyophilised reference peptide, sealed vials, per-batch CoA, research use only.
Retatrutide is the most-searched unapproved peptide on the internet - roughly 673,000 monthly Google searches in the United States alone , third only behind tirzepatide and semaglutide, both of which are FDA-approved. The asymmetry tells you something interesting: search demand is running ahead of clinical availability. This guide is the science-side companion to our country-specific sourcing piece Where to Buy Retatrutide in the UK. Here we cover the molecule, the mechanism, the Phase 2 evidence, and how research-grade retatrutide sits on the New-U catalogue as Retatrutide. For where it sits in the broader regulatory map of approved-vs-investigational peptides, see Peptides & the FDA.
Plain-English summary. Retatrutide is an unapproved investigational peptide. The FDA, MHRA, EMA and TGA have not authorised it as a medicine. Research-grade retatrutide is a separate, lawful category - sold as a lyophilised reference reagent labelled research use only, not for human consumption . New-U sells only the research reagent. This page is general information, not legal or medical advice; do not use unapproved peptides on people.
What retatrutide actually is
Retatrutide, developmental code LY3437943 , is a 39-amino-acid synthetic peptide engineered for simultaneous agonism at three receptors. Structurally it shares the broad lipidated-peptide architecture of tirzepatide - a long peptide backbone with a fatty acid moiety conjugated to a lysine via a γ-Glu-2xOEG linker - but the residue choices at the receptor-binding interfaces are tuned to balance affinity at all three targets simultaneously rather than two.
The half-life is approximately 6 days , supporting once-weekly subcutaneous dosing in the clinical-trial programme. The full molecular description is published in the original Phase 1 / Phase 2 papers indexed under PubMed: retatrutide / LY3437943.
Why triple agonism is mechanistically different
The three receptors retatrutide activates do non-overlapping things:
This is why retatrutide’s mean body-weight reduction is materially larger than tirzepatide’s at comparable timepoints. It is not just GLP-1 amplified; it is GLP-1 plus a second incretin plus a metabolic-rate lever pulled from a different physiological direction.
The Phase 2 evidence: the 24% number
The pivotal Phase 2 obesity trial (Jastreboff et al., NEJM, 2023) enrolled 338 adults with obesity without type-2 diabetes and reported the following mean body-weight reductions over 48 weeks vs placebo:
For context: tirzepatide’s SURMOUNT-1 endpoint at 15 mg over 72 weeks was −20.9%. Retatrutide’s 12 mg arm exceeded that mark at 48 weeks. The Phase 2 cohort also did not appear to plateau by 48 weeks - the weight-reduction curve was still descending at trial end - which is one reason Phase 3 endpoints will be watched closely.
Phase 3: the TRIUMPH programme
Retatrutide is now in the TRIUMPH Phase 3 programme. The current registered trials cover:
All TRIUMPH trials are listed on the public registry - ClinicalTrials.gov: retatrutide. Topline readouts and any FDA submission timeline are subject to change; refer to Eli Lilly investor disclosures for the current schedule.
Retatrutide vs tirzepatide vs semaglutide, side by side
Retatrutide is the only one of the three that is unlicensed. The mechanistic and pharmacokinetic comparison is closest to tirzepatide; the differentiator is the glucagon arm.
Retatrutide as a research compound
On the New-U catalogue, the research-grade reference peptide is listed as Retatrutide . Same 39-amino-acid sequence, same triple-agonist mechanism, same molecule Eli Lilly studies as LY3437943. The product is a sealed glass vial of lyophilised peptide for laboratory use only.
For the country-specific sourcing walkthrough of how UK researchers can lawfully purchase retatrutide given the MHRA framing, see Where to Buy Retatrutide in the UK.
How to verify retatrutide purity
The purity test for a 39-amino-acid lipidated peptide is the same as for tirzepatide:
Full walkthrough: How to Read a Certificate of Analysis.
Red flags on retatrutide listings
Because there is no licensed retatrutide product anywhere in the world, every listing should be evaluated as research compound or treated with extreme caution. Walk away from any retatrutide listing that:
Frequently Asked Questions
What is retatrutide? A 39-amino-acid synthetic peptide developed by Eli Lilly (developmental code LY3437943). It is the first triple agonist to reach late-stage clinical trials, simultaneously activating the GLP-1, GIP and glucagon receptors.
Is retatrutide approved? No. As of 2026 it has no marketing authorisation anywhere in the world. It is currently in the Phase 3 TRIUMPH programme.
What did the Phase 2 trial show? Mean body-weight reduction of ~24.2% over 48 weeks at the 12 mg weekly dose (NEJM, 2023) - the largest incretin-class effect on record at the time of publication.
How is retatrutide different from tirzepatide? Tirzepatide is dual GLP-1 + GIP. Retatrutide adds a third receptor - glucagon - producing hepatic thermogenesis and additional energy expenditure.
Is retatrutide a research compound on this site? Yes. New-U catalogues research-grade retatrutide as Retatrutide, lyophilised reference peptide with a per-batch Certificate of Analysis. Sold research use only, not for human consumption.
Where can I buy retatrutide for research? Retatrutide is unlicensed, so no pharmacy or clinic can sell it - laboratories source it from research-compound suppliers that publish a per-batch CoA and label material research use only. New-U ships research-grade retatrutide, catalogued as Retatrutide, in sealed 10-vial packs verified to >99% HPLC purity by Janoshik and Freedom Diagnostics, tracked worldwide. Research use only.
How much does research retatrutide cost? It is priced per vial in USD and scales by mg per vial from 5 mg up to 60 mg, so the per-mg cost drops on larger vials. Every tier ships in sealed 10-vial packs at >99% HPLC purity with a per-batch CoA; free shipping over $300, card and crypto accepted. See the retatrutide product page for current per-vial pricing.
Related Reading
Primary sources & further reading
External links are provided for research reference only; New-U is not affiliated with the cited organisations and links carry no endorsement either way.
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Lab-Verified Research Retatrutide
New-U Research Compounds catalogues retatrutide as Retatrutide - sealed 10-vial packs of lyophilised reference peptide, independently verified by Janoshik and Freedom Diagnostics for >99% HPLC purity, with a per-batch Certificate of Analysis. Tracked worldwide delivery. Research use only - not for human consumption.
Research-grade · >99% HPLC purity · COA per lot
Buy Retatrutide from New-U Research Compounds
Lab-verified by Janoshik Analytical (RP-HPLC + ESI-MS), sealed vials, discreet tracked worldwide shipping. For laboratory research use only — not for human consumption.
Premium research peptides at >99% HPLC-verified purity, third-party tested by Janoshik Analytical with a Certificate of Analysis on every lot. Shipped lab-direct, discreet and cold-chain, worldwide. For laboratory research use only.
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