Retatrutide (LY3437943) is an investigational synthetic peptide that activates GIP, GLP-1, and glucagon receptors in one molecule. Its research value comes from testing whether coordinated incretin and glucagon-receptor signaling can change glycemic, adipose, hepatic, and energy-balance endpoints without reducing the mechanism to a stronger version of a single- or dual-receptor agonist or treating separate trial outcomes as interchangeable evidence.
Retatrutide has moved quickly from receptor-engineering work to a large clinical research program. The strongest peer-reviewed record still begins with the molecule’s discovery, its phase 2 obesity and type 2 diabetes trials, and later analyses of liver fat, receptor structure, and body composition.[1][2][3]
This refresh also records the July 23, 2026 Phase 3 status without presenting sponsor topline results as peer-reviewed evidence. It contains no clinical dosing, administration, mixing, reconstitution, or personal-use instructions. The GLP-1 and metabolic research hub owns family navigation; this page owns the Retatrutide entity.
- Retatrutide is a single GIPR/GLP-1R/GCGR triple agonist, not a three-compound mixture.
- The glucagon-receptor component distinguishes it from tirzepatide and semaglutide.
- Peer-reviewed Phase 2 publications support mechanism and endpoint interpretation; 2026 Phase 3 announcements remain sponsor-reported topline evidence until full publication.
- Lilly continued to describe Retatrutide as investigational on July 23, 2026 and said it planned a U.S. BLA submission in the first quarter of 2027.
- A research reagent is not a Lilly clinical-trial material or an approved pharmaceutical product.
Retatrutide Technical Identity
Retatrutide is the adopted name for LY3437943, a synthetic peptide engineered to agonize three class B G-protein-coupled receptors: the glucose-dependent insulinotropic polypeptide receptor (GIPR), glucagon-like peptide-1 receptor (GLP-1R), and glucagon receptor (GCGR). The discovery paper reported balanced GCGR and GLP-1R activity with greater GIPR activity in the study’s in-vitro systems. The same report described decreased body weight and improved glycemic control in obese mice, and a body-weight reduction persisting up to 43 days after a single dose in the human phase 1 study.[1]
The receptor triad is the identity anchor. “GLP-3” is an informal media label, not a receptor or accepted scientific class. “Triple agonist” is more precise because it names the coordinated receptor architecture without inventing a third GLP hormone.
LY3437943 is also a development-code identity, not a commercial formulation name. A useful Retatrutide record should preserve the exact molecule, source, lot, and study context rather than treating every material advertised with the common name as equivalent to Lilly’s investigational product. The discovery program optimized one peptide for activity across three receptors and for extended exposure; those design properties belong to the reported molecule and test systems, not automatically to an unlabeled powder or an unsupported analog.
Reagent identity record
| Identity field | Recorded value | Source |
|---|---|---|
| Name and development code | Retatrutide / LY3437943 | Coskun 2022, PMID 35985340 |
| CAS Registry Number | 2381089-83-2 | Apex catalog record; confirm on the lot COA |
| Molecular formula | C221H342N46O68 | Apex catalog record; confirm on the lot COA |
| Average molecular mass | 4,731.4 g/mol calculated from that formula; the catalog record states 4,731.33 Da | Formula-derived and catalog values; reconcile the 0.09 Da difference against the lot COA |
| Peptide length | 39 residues; no full sequence in the records cited here | Apex catalog record |
| Regulatory status | Investigational; no FDA, EMA, NMPA, MHRA, PMDA, or other national marketing approval in any jurisdiction | Status check July 24, 2026 |
These are registry and catalog fields, not trial results.
How Triple-Receptor Agonism Is Interpreted
Retatrutide should be read as coordinated pharmacology, not as three independent effects stacked together. GIPR and GLP-1R provide incretin-family signaling. GCGR adds a distinct pathway connected to hepatic substrate handling and energy-expenditure hypotheses. The research question is whether the three components produce a useful integrated state while the incretin components constrain the glycemic liability that isolated glucagon-receptor activation can create.
Cryo-electron microscopy work published in 2024 examined Retatrutide-bound GIPR, GLP-1R, and GCGR complexes, providing structural context for how one peptide can engage all three receptors.[4] That research letter’s indexed record carries no abstract and reports no quantitative endpoint, so it is cited for receptor-occupancy context only. Structural occupancy does not by itself establish whole-organism efficacy, durability, safety, or comparative superiority. Those questions require properly designed studies at their own evidence level.
GIP receptor contribution
GIPR belongs to the incretin side of the design. In an assay, its contribution may be evaluated through receptor activation, cyclic-AMP signaling, insulin-secretory context, or interaction with the other agonist components. A result at GIPR cannot be summarized accurately without the species, receptor construct, comparator, and assay format because potency values are not portable across laboratories by default.
GLP-1 receptor contribution
GLP-1R provides the best-established pharmacology in the architecture, but Retatrutide is not simply a GLP-1 analog with two decorative labels. Appetite-related, gastric, pancreatic, and glycemic endpoints integrate across tissues and time. Cell-signaling data therefore should not be used alone to predict a body-weight result, and a clinical body-weight result does not identify how much of the effect came from GLP-1R.
Glucagon receptor contribution
GCGR is the distinguishing third receptor. It creates research interest around hepatic substrate handling, energy expenditure, and liver-fat endpoints while also requiring attention to glycemic balance. The triple-agonist hypothesis is that simultaneous GIPR and GLP-1R activity can produce a different integrated state than isolated glucagon signaling. That hypothesis must be tested rather than assumed from the receptor list.
Peer-Reviewed Phase 2 Evidence
Obesity trial
The 2023 phase 2 obesity trial randomized 338 adults with obesity, or overweight plus a weight-related condition, and followed them for 48 weeks. The publication reported dose-dependent body-weight change, with a least-squares mean change of -24.2% in the highest studied group at week 48 versus -2.1% with placebo.[2] Gastrointestinal adverse events were the most frequent events and dose-dependent heart-rate increases were also reported. These are trial findings, not use instructions.
Type 2 diabetes trial
A separate 2023 phase 2 trial in adults with type 2 diabetes reported reductions in HbA1c and body weight across studied Retatrutide groups relative to placebo, with dulaglutide included as an active comparator.[3] This study is central to the triple-agonist thesis because glycemic improvement was observed in a molecule that also activates GCGR. It does not establish that every exposure pattern or material will reproduce those results.
Liver fat and body composition
A phase 2a substudy measured relative liver fat in participants with metabolic dysfunction-associated steatotic liver disease.[5] A later DXA substudy measured total fat mass and reported that the proportion of lean-mass loss to total weight loss was similar to other obesity treatments despite greater overall weight loss.[6] Both endpoint sets are tabulated below with their populations and timepoints.
Reported endpoints with population, timepoint, and source
Each row is one endpoint from one trial; rows are not comparable to each other.
| Trial and population | Endpoint and timepoint | Reported result | Source |
|---|---|---|---|
| Phase 2 obesity; 338 adults with obesity, or overweight plus a weight-related condition | Least-squares mean body-weight change, week 24 | -7.2% (1 mg) to -17.5% (12 mg) vs -1.6% placebo | Jastreboff 2023, PMID 37366315 |
| Phase 2 type 2 diabetes; 281 adults randomized | HbA1c week 24; bodyweight week 36 | HbA1c -2.02 percentage points (12 mg escalation) vs -0.01 placebo and -1.41 dulaglutide 1.5 mg; bodyweight -16.94% vs -3.00% placebo and -2.02% dulaglutide | Rosenstock 2023, PMID 37385280 |
| Phase 2a MASLD substudy; 98 adults with at least 10% liver fat | Mean relative liver-fat change and normalization, week 24 | -42.9% (1 mg), -57.0% (4 mg), -81.4% (8 mg), -82.4% (12 mg) vs +0.3% placebo; liver fat below 5% in 79% (8 mg) and 86% (12 mg) vs 0% placebo | Sanyal 2024, PMID 38858523 |
| DXA body-composition substudy; 189 adults with type 2 diabetes, 103 with paired week-36 scans | Total fat-mass reduction, week 36, on-treatment data before study-drug discontinuation | 26.1% (8 mg pooled) and 23.2% (12 mg) vs 4.5% placebo and 2.6% dulaglutide | Coskun 2025, PMID 40609566 |
How to read the endpoint set
The endpoint pattern matters more than a single headline percentage. The obesity trial establishes a body-weight response in its enrolled population. The diabetes trial asks whether glycemic improvement can coexist with GCGR agonism. The liver-fat substudy provides a hepatic endpoint tied more closely to the glucagon-receptor rationale, while the DXA substudy separates total mass from fat and lean compartments. Together they support a multi-endpoint research model; they do not make every endpoint interchangeable or establish an approved indication.
Limitations and tolerability remain part of the evidence
The phase 2 obesity publication reported gastrointestinal adverse events as the most common events and described dose-dependent heart-rate increases that peaked during the study before declining.[2] The type 2 diabetes trial also reported gastrointestinal events in its Retatrutide groups.[3] These observations belong beside efficacy endpoints because a larger endpoint change does not erase tolerability, discontinuation, estimand, missing-data, or follow-up questions.
The phase 2 results are published peer-reviewed records. The July 2026 TRIUMPH-2 and TRIUMPH-3 figures were sponsor-reported topline results when this article was updated; detailed peer-reviewed reports had not yet been published.
Phase 3 Status as of July 23, 2026
Lilly announced positive topline results from TRIUMPH-2 and TRIUMPH-3 on July 23, 2026. TRIUMPH-2 studied adults with type 2 diabetes and obesity or overweight. TRIUMPH-3 studied adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes. Lilly reported that both trials met their primary endpoints and said the available Phase 3 package supported planned global submissions; the company specifically stated that it planned a U.S. Biologics License Application in the first quarter of 2027.
The announcement did not convert Retatrutide into an approved product. As of the July 24, 2026 check, Retatrutide held no marketing approval from the FDA, EMA, NMPA, or any other national regulator anywhere globally; a planned application is neither a submission nor an approval. Lilly continued to call the molecule investigational and said detailed results would be presented at future meetings and published in peer-reviewed journals. The TRIUMPH-1 Phase 3 results guide owns the detailed interpretation of the earlier TRIUMPH-1 program and its limitations.
Retatrutide, Tirzepatide, and Semaglutide
| Compound | Receptor architecture | Interpretation boundary |
|---|---|---|
| Semaglutide | GLP-1R agonist | A single-receptor benchmark; not a direct substitute for multi-agonist evidence. |
| Tirzepatide | GIPR/GLP-1R dual agonist | Adds GIPR signaling but not GCGR agonism. |
| Retatrutide | GIPR/GLP-1R/GCGR triple agonist | Investigational; head-to-head superiority cannot be inferred from separate trials. |
The single-receptor benchmark there is semaglutide’s STEP 1 trial, which studied once-weekly semaglutide 2.4 mg in adults with overweight or obesity and without diabetes (Wilding 2021, PMID 33567185). Its weight-change figures stay with the dedicated Semaglutide research guide; a different trial, population, and estimand is not a Retatrutide comparator.
The Retatrutide versus Tirzepatide comparison owns the symmetric decision framework. This entity guide does not compare headline percentages from different populations, protocols, estimands, durations, or evidence maturities as though they came from one trial.
Verification of a Retatrutide Research Material
A research material must be evaluated as its own record. The declared analyte, lot, expected mass, chromatographic method, and mass-spectrometry result should agree. HPLC can describe a chromatographic profile under a stated method, while mass spectrometry can support mass identity when the reported ion or deconvoluted mass is interpretable. Neither method alone proves receptor activity, sterility, clinical safety, efficacy, or equivalence to Lilly’s investigational material. A lot record should carry a numeric threshold, for example ≥99% by reversed-phase HPLC under a named method, rather than an unquantified purity badge.
The peptide COA guide, HPLC guide, and mass-spectrometry guide explain how to read a current lot record without treating a badge or image as evidence.
Retatrutide research-material record
The product page can document current availability and lot-specific commercial records. It cannot transfer Lilly trial results, regulatory status, safety, or efficacy to a separate research reagent. Recheck the current page and current lot documentation before relying on a specification.
Frequently Asked Questions About Retatrutide
What is Retatrutide?
Retatrutide, also called LY3437943, is an investigational synthetic peptide designed to activate GIP, GLP-1, and glucagon receptors in one molecule. It is therefore described as a triple hormone-receptor agonist rather than a GLP-1-only or dual GIP/GLP-1 agonist.
Is Retatrutide the same as tirzepatide?
No. Tirzepatide activates GIP and GLP-1 receptors. Retatrutide activates those two receptors and also the glucagon receptor. Results from separate trials cannot establish a head-to-head difference between them.
What did the Retatrutide Phase 2 trials show?
Peer-reviewed Phase 2 trials reported dose-dependent changes in body weight, glycemic measures, liver fat, and body composition in defined study populations. They also reported tolerability findings, including gastrointestinal adverse events. The results are trial-specific and are not use instructions.
What changed in the Phase 3 program in July 2026?
On July 23, 2026, Lilly announced positive topline results from TRIUMPH-2 and TRIUMPH-3 and said it planned a U.S. Biologics License Application in the first quarter of 2027. Detailed results were still awaiting future presentation and peer-reviewed publication.
Is Retatrutide FDA approved?
No. Lilly described Retatrutide as investigational on July 23, 2026 and stated that a U.S. application was planned, not approved. A separate research-grade reagent is also not an approved pharmaceutical or a therapeutic equivalent.
What can HPLC and mass spectrometry verify?
HPLC can report a chromatographic profile under a stated method, and mass spectrometry can support mass identity with an interpretable result. Neither method alone establishes receptor function, sterility, clinical safety, efficacy, or equivalence to a clinical-trial material.
References and Current Official Sources
- Coskun T, 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 Metab. 2022;34(9):1234-1247.e9. PMID: 35985340.
- Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity – A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PMID: 37366315.
- Rosenstock J, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA. Lancet. 2023;402(10401):529-544. PMID: 37385280.
- Li W, et al. Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide. Cell Discov. 2024;10(1):77. PMID: 39019866.
- Sanyal AJ, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med. 2024;30(7):2037-2048. PMID: 38858523.
- Coskun T, et al. Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial. Lancet Diabetes Endocrinol. 2025;13(8):674-684. PMID: 40609566.
- Eli Lilly and Company. TRIUMPH-2 and TRIUMPH-3 topline announcement. July 23, 2026.
- ClinicalTrials.gov. TRIUMPH-2, NCT05929079. Current source check July 24, 2026.
- ClinicalTrials.gov. TRIUMPH-3, NCT05882045. Current source check July 24, 2026.
