Official New‑U reference · Reviewed 24 September 2026

Retatrutide (LY3437943): Scientific Research Reference

Retatrutide is an investigational triple-receptor agonist targeting GLP-1, GIP and glucagon receptors, and is not approved as a medicine anywhere. Explore its molecular characteristics, published research findings, clinical trial programme and laboratory analytical information.

For laboratory and research use only — not for human or veterinary use. 21+.

One molecule, three receptors: the triple-agonist profile characterised in published receptor studies.

Retatrutide at a glance

Research code

LY3437943

Compound class

Triple GLP-1R / GIPR / GCGR agonist — a "GGG" tri-agonist

Structure

Engineered 39-amino-acid peptide, 4,894.6 Da, carrying a C20 fatty-diacid chain

Clinical stage

Phase 3 (the TRIUMPH programme)

Regulatory status

Investigational — not approved as a medicine in any jurisdiction

Reported half-life

Approximately 6 days (external pharmacokinetic research)

New-U catalogue identifier

GLP1-RC-RT ("Reta")

GLP1-RC-RT batch analysis

>99% purity by RP-HPLC; identity confirmed by mass spectrometry

What is retatrutide?

Retatrutide — research code LY3437943 — is an engineered 39-amino-acid peptide designed to act on three hormone receptors at once: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the glucagon receptor (GCGR). Because each target belongs to a different hormone, the literature files it among triple agonists, often shortened to "GGG".

It is investigational. Its clinical programme is sponsored by Eli Lilly and Company, and no regulator has approved retatrutide as a medicine. What is known comes from three kinds of evidence: in-vitro receptor pharmacology, pharmacokinetic characterisation and registered clinical trials. This page condenses each of them, keeping every figure attached to the study that produced it.

In research communities the compound is simply "Reta". Online it is also searched as "GLP-3", which is a nickname rather than a science term: there is no hormone called GLP-3. The label counts receptors — retatrutide adds glucagon-receptor activity to the two incretin receptors the dual-agonist class already covers.

How retatrutide works: three receptors, one molecule

Receptor assays report agonist activity at all three targets, strongest at GIPR. The values below are half-maximal effective concentrations (EC50): the lower the number, the less peptide the assay needed to reach half of its maximal receptor response.

Receptor Reported EC50 What the research looks at GLP-1R 0.775 nM The receptor single- and dual-agonist compounds also target; glucose-dependent insulin secretion and gastric emptying are measured experimentally. GIPR 0.0643 nM Potency reported as 8.9-fold that of native GIP — the most potent of the three arms in these assays. GCGR 5.79 nM The arm that separates a triple agonist from the dual class; hepatic energy-expenditure endpoints are studied in relation to it.

Investigators recorded transient glucose elevations attributed to the GCGR arm and monitored glycaemic endpoints under the study protocols.

Molecular structure and design

The backbone is derived from GIP and the finished molecule weighs 4,894.6 Da. Four deliberate changes to it each answer a specific stability or exposure question the research investigates:

α-aminoisobutyric acid (Aib) at positions 2 and 20 — studied for resistance to DPP-IV cleavage.

α-methyl-leucine at position 13 — studied for stability against protease cleavage.

A C20 fatty diacid attached to lysine 17 through an AEEA–γGlu spacer — studied as an albumin-binding element that prolongs systemic exposure.

An amidated C-terminus.

Published sequence notation

Pharmacokinetics reported in published research

The albumin-binding fatty-diacid chain is the reason the reported half-life runs to days rather than minutes. The parameters below come from external pharmacokinetic studies of the investigational compound under their own protocols.

Parameter Reported value Apparent elimination half-life Approximately 6 days Time to peak concentration (Tmax) 12–72 h Exposure Dose-proportional (linear) across the investigated range Steady state Reached after 3–4 weeks under the investigated protocols Metabolism Hepatic proteolysis plus β-oxidation of the C20 fatty-diacid chain Interactions No CYP-mediated interaction reported

These are observations about the investigational compound in study populations, not handling or use information for laboratory research material.

The clinical trial programme

Retatrutide moved from Phase 2 into a Phase 3 programme named TRIUMPH. The headline findings are listed with their study, arm, timepoint and publication status. Figures from different studies are not a head-to-head comparison: the populations, durations and protocols differ.

Study Design Reported finding Status Phase 2 obesity trial — Jastreboff et al., N Engl J Med 2023 (PMID 37385275) Randomised Phase 2; obesity population; 48 weeks 12 mg arm: mean change from baseline in body weight of −24.2% at week 48; more than 90% of that arm reached a ≥10% reduction Peer-reviewed Phase 2a MASLD trial — Sanyal et al., Nat Med 2024 Randomised Phase 2a; metabolic dysfunction-associated steatotic liver disease; liver fat by MRI-PDFF Relative reduction in hepatic fat fraction of up to 82.4% at the protocol-defined timepoint; steatosis resolution reported in more than 90% of the 12 mg arm Peer-reviewed TRIUMPH-1 — Phase 3 (NCT05929066) — Jastreboff et al., N Engl J Med 2026 (PMID 42814954) Randomised against placebo; adults with obesity without diabetes; 80 weeks 12 mg arm: mean change from baseline in body weight of −25.0% at week 80, against −3.9% with placebo (treatment-regimen estimand) Peer-reviewed TRIUMPH-2 — Phase 3 (NCT05929079) — Bellido et al., Lancet 2026 (PMID 42810372) Randomised against placebo; adults with obesity and type 2 diabetes; 80 weeks 12 mg arm: mean change from baseline in body weight of −18.8% at week 80, against −5.1% with placebo Peer-reviewed TRANSCEND-T2D-1 — Phase 3 (NCT06354660) — Bajaj et al., Lancet 2026 (PMID 42250575) Randomised against placebo; type 2 diabetes on diet and exercise; 40 weeks 12 mg arm: HbA1c change of −1.94% at week 40, against −0.81% with placebo Peer-reviewed TRIUMPH-4 (NCT05931367) Dedicated knee-osteoarthritis study within the programme Not summarised on this page — see the registry record Registered (ClinicalTrials.gov) Further TRIUMPH and TRANSCEND studies Cardiovascular and kidney outcomes Not summarised on this page Registered

Published clinical findings summarised on this page relate to the investigational materials and protocols used in those external studies. They do not establish the safety, efficacy, intended use or clinical equivalence of New-U GLP1-RC-RT research material. The trial figures describe the investigational compound under trial protocols; none of them is a property of GLP1-RC-RT or of any other research material.

Read the Phase 3 TRIUMPH programme explainer on new-u.io

Adverse events recorded in the trials

Investigators recorded the events below in the published and sponsor-reported trials. No regulator has established the safety of retatrutide. These events describe those study populations under those protocols; they are not a prediction of, or guidance about, anything a reader may experience.

Gastrointestinal events — nausea (the most frequently reported), diarrhoea, vomiting and constipation — were most frequent early in the trials and attenuated later, per investigators.

Decreased appetite, recorded as an adverse event.

Transient increases in resting heart rate.

Transient glucose elevation attributed to the glucagon-receptor arm, monitored under the study protocols.

Discontinuation due to adverse events in TRIUMPH-1 (sponsor topline, ADA 2026): 4.1% (4 mg arm), 6.9% (9 mg arm) and 11.3% (12 mg arm), against 4.9% on placebo.

Permanent discontinuation due to adverse events or death in TRIUMPH-2 (Lancet 2026): 4% (4 mg arm), 12% (9 mg arm) and 8% (12 mg arm), against 5% on placebo.

Retatrutide safety research guide on new-u.io

GLP1-RC-RT: the retatrutide research material New-U supplies

New-U Research Compounds supplies retatrutide under the catalogue identifier GLP1-RC-RT ("Reta"), as laboratory research material. The identifier keeps two things apart on purpose: retatrutide, the scientific subject of everything above, and the lyophilised research material New-U supplies, documented by published batch analysis of tested samples — not by clinical trials.

Specification Detail Catalogue identifier GLP1-RC-RT Scientific subject Retatrutide (LY3437943) Form Lyophilised powder in sealed vials Formats Single-vial sample or 10-vial research pack Purity >99% by RP-HPLC area normalisation Identity Stated on the published Certificate of Analysis where the report includes an identity test Testing laboratories Janoshik Analytical and Freedom Diagnostics Certificates of Analysis Certificates of Analysis are published on the website — on each product page and at /coa — rather than packed with orders. Laboratory storage Lyophilised powder: store in freezer (−20 °C). Reconstituted: refrigerate 1–6 °C, away from sunlight. Use within the validated stability window for the specific batch and formulation. Intended use Laboratory research material. Not for human or veterinary use.

Batch analysis reports identity and purity for the sample tested. It does not establish sterility, endotoxin or heavy-metal status, pharmaceutical equivalence, or any clinical property.

Orders, accounts and payment complete on new-u.io, the official New-U store; purchasers must be 21 or older. US orders ship from the USA or China depending on stock and fulfilment; all other destinations ship from China, direct from the manufacturer. Lyophilised peptides are stable through the tracked transit window. Delivery takes approximately 6–14 business days worldwide.

Open the GLP1-RC-RT product page on new-u.io

How to check a retatrutide batch certificate

A certificate is only as useful as the reading it gets. Five checks separate a real analytical record from a decorative one:

Match the subject. The certificate should name retatrutide or GLP1-RC-RT — not a neighbouring product or an unnamed "peptide".

Read the method, not only the number. A purity figure such as >99% should state RP-HPLC area normalisation: the target peak as a share of the total integrated peak area for the tested sample.

Look for identity confirmation. Mass spectrometry shows the tested material is the expected molecule; a purity figure alone cannot.

Check who tested it and when. The laboratory, report number and test date should all be present — New-U certificates record each of them.

Know the limits. HPLC and mass spectrometry establish identity and purity only; they say nothing about sterility, endotoxin, heavy metals or any clinical property.

New-U certificates are published on new-u.io, readable before ordering.

View the retatrutide batch certificates on new-u.io

Frequently asked questions

What is retatrutide?

Retatrutide (LY3437943) is an investigational engineered peptide that activates three hormone receptors — GLP-1, GIP and glucagon — within one molecule. It is being studied in registered clinical trials, including the Phase 3 TRIUMPH programme, and is not approved as a medicine in any jurisdiction.

Is retatrutide the same thing as "GLP-3"?

"GLP-3" is online shorthand for retatrutide, not a science term. No hormone or drug class called GLP-3 exists; the nickname reflects that retatrutide adds a third receptor target, glucagon, to the GLP-1 and GIP receptors.

Why is retatrutide called a triple agonist?

An agonist switches a receptor on. In-vitro studies report retatrutide doing that at three receptors — GLP-1R (EC50 0.775 nM), GIPR (EC50 0.0643 nM) and GCGR (EC50 5.79 nM) — so it is classed as a triple, or "GGG", agonist.

Is retatrutide approved by the FDA or any other regulator?

No. Retatrutide remains investigational: no regulator has approved it as a medicine. Phase 3 results have been published for TRIUMPH-1, TRIUMPH-2 and TRANSCEND-T2D-1 (2026), and cardiovascular and kidney outcome studies are still registered.

What half-life has been reported for retatrutide?

Published pharmacokinetic research reports an apparent elimination half-life of approximately 6 days, attributed to the albumin-binding C20 fatty-diacid chain, with steady-state exposure reached after 3–4 weeks under the investigated protocols.

What is GLP1-RC-RT?

GLP1-RC-RT is New-U's catalogue identifier for the retatrutide laboratory research material it supplies — "Reta" for short. It is lyophilised material whose identity and purity are verified by an independent laboratory. It is not a medicine and is not offered for human or veterinary use.

Where can I see the certificate for New-U's retatrutide?

On new-u.io: the current batch certificate is on the GLP1-RC-RT product page and in the certificate bank at new-u.io/coa/retatrutide, readable before you order rather than packed with the parcel.

How should lyophilised retatrutide be stored in a laboratory?

Keep the lyophilised powder frozen at −20 °C. Once a laboratory protocol puts it into solution, hold the solution at 1–6 °C away from light and avoid repeated freeze–thaw cycles, which can degrade the fatty-acid modification.

Do the clinical trial figures apply to research material?

No. Trial figures describe the investigational compound and the protocols of the studies that produced them. Batch analysis of GLP1-RC-RT establishes the identity and purity of the tested sample and nothing clinical — pairing a certificate with a trial paper does not amount to clinical validation.

Is reta.lol an official New-U website?

Yes. reta.lol is a retatrutide reference operated by Hilxera Distribution Services LLC for New-U Research Compounds. Orders, accounts and payment complete only on new-u.io, and every official New-U domain is listed at new-u.io/official-domains.

Next step: open the GLP1-RC-RT product page for the current batch certificate, formats and ordering. Research use only.