Written by [author]. Reviewed by [reviewer].
Updated . How we research and review.
Short answer
Retatrutide is a synthetic 39-amino-acid peptide that activates three hormone receptors: GIP, GLP-1 and glucagon. [1] Eli Lilly and Company develops it under the code LY3437943. Its published human trials run from phase 1 to one phase 3 trial, TRANSCEND-T2D-1, which appeared in June 2026. [2] The TGA has not approved it, and the Poisons Standard has no entry for it. [3][4]
What is retatrutide?
Retatrutide is a triple hormone receptor agonist: a single synthetic peptide that activates the glucagon receptor, the GIP receptor and the GLP-1 receptor. Lilly researchers first described it in Cell Metabolism in 2022 as LY3437943. [1] Sport Integrity Australia lists "Reta" as another name in circulation. [3]
The molecule has no natural counterpart. A 2026 pharmacology paper calls it "a not endogenously occurring peptide". [11] Its three target hormones are associated with glucose regulation, insulin secretion and hunger. [3]
Retatrutide is still investigational. The 2026 TRANSCEND-T2D-1 paper describes it as under clinical development for type 2 diabetes, obesity and related complications. [2] Sport Integrity Australia states that no regulator, the TGA included, has approved it for therapeutic use. [3] Research-grade retatrutide in 10mg and 20mg vials is sold for laboratory research use only, with a certificate for each batch.
How does retatrutide work?
Retatrutide works by binding and activating three receptors at once: the glucagon, GIP and GLP-1 receptors. In Lilly's cell assays it showed balanced glucagon and GLP-1 receptor activity and more GIP receptor activity. [1] In cell cultures, stimulation of all three receptors raised adenylyl cyclase activity and cyclic AMP levels. [11]
The glucagon arm is what sets retatrutide apart from earlier incretin peptides. In obese mice, the 2022 discovery paper attributed part of the body weight effect to glucagon receptor-mediated increases in energy expenditure, added to the reduced calorie intake driven by the GIP and GLP-1 receptors. [1] That is a mouse finding. It is the hypothesis the human programme was built to test.
Two isolated-tissue studies looked at the heart. In right atrial tissue taken from patients during open heart surgery, retatrutide increased the force of contraction from 10 nM up to 100 nM, and antagonists at each of its three receptors reduced that effect. [11] In mouse right atria, retatrutide raised the beating rate through the glucagon receptor, cyclic AMP and protein kinase A. [12] Neither study measured anything in living people. They give researchers a cellular lead on the heart rate rise seen in trials.
Retatrutide stays in circulation for days. The phase 1b trial in adults with type 2 diabetes reported a half-life of approximately 6 days. [7]
What is the structure of retatrutide?
Retatrutide is a 39-residue linear peptide with three non-coded amino acids, a C20 fatty diacid side chain on lysine 17 and an amidated C-terminus. We decoded the structure from the systematic name on PubChem substance record 471328801 on 29 September 2026. [6]
| Field | Value | Source |
|---|---|---|
| CAS number | 2381089-83-2 | PubChem substance record |
| PubChem CID | 171390338 | PubChem |
| Molecular formula | C221H342N46O68 | PubChem |
| Molar mass | 4731 g/mol | PubChem |
| Length | 39 amino acids | PubChem systematic name |
| One-letter sequence | YXQGTFTSDYSIXLDKKAQXAFIEYLLEGGPSSGAPPPS | Decoded from the systematic name |
| X residues | Aib (alpha-aminoisobutyric acid) at 2 and 20; alpha-methyl-leucine at 13 | PubChem systematic name |
| Side chain | C20 fatty diacid on Lys17, through a gamma-glutamate and one AEEA spacer | PubChem systematic name |
| C-terminus | Serine amide | PubChem systematic name |
| Codes and synonyms | LY3437943; Triple G (PubChem record title) | PubChem |
The formula and mass come from PubChem's compound record [5] and the sequence detail from the substance record. [6] Two details matter when you check a certificate. PubChem's name search for "retatrutide" does not resolve directly; depositor records standardise to CID 171390338, and a separate CID, 171934787, is labelled as the sodium salt. A salt form has a different mass, so know which form a lab is reporting.
Our guide on how to read a peptide certificate of analysis shows where the mass spectrometry result sits on the report. For retatrutide it should correspond to a peptide of about 4731 g/mol.
What has research on retatrutide examined?
Retatrutide has been examined in cell assays, obese mice, isolated heart tissue and randomised human trials in adults with type 2 diabetes, obesity or fatty liver disease. The human trials are recent: the first appeared in 2022 and the only published phase 3 trial in June 2026. [7][2]
| Year | Study (PMID) | Model | Who was studied | Reported finding |
|---|---|---|---|---|
| 2022 | Discovery (35985340) | Cells, mice, phase 1 in people | Receptor assays, obese mice, a single ascending study | Balanced glucagon and GLP-1 activity, more GIP activity; lower body weight and better glycaemic control in obese mice [1] |
| 2022 | Phase 1b (36354040) | Human, randomised | 72 adults with type 2 diabetes, 12 weeks | Half-life approximately 6 days; placebo-adjusted body weight change up to -8.96 kg in the highest group [7] |
| 2023 | Phase 2, obesity (37366315) | Human, randomised | 338 adults with obesity or overweight, 48 weeks | Mean body weight change of -8.7% to -24.2% against -2.1% with placebo [8] |
| 2023 | Phase 2, type 2 diabetes (37385280) | Human, randomised, placebo and dulaglutide controlled | 281 adults with type 2 diabetes at 42 US centres, 36 weeks | HbA1c change at 24 weeks of -0.43% to -2.02% against -0.01% with placebo and -1.41% with dulaglutide [9] |
| 2024 | Liver fat substudy (38858523) | Human, phase 2a | 98 adults with metabolic dysfunction-associated steatotic liver disease and at least 10% liver fat | Relative liver fat change at 24 weeks of -42.9% to -82.4% against +0.3% with placebo [13] |
| 2025 | Body composition substudy (40609566) | Human, phase 2 | 189 adults from the type 2 diabetes trial, DXA scans | Total fat mass reduction of 4.9% to 26.1% against 4.5% with placebo [14] |
| 2026 | TRANSCEND-T2D-1 (42250575) | Human, phase 3 | 537 adults with type 2 diabetes at 48 sites in the USA, Mexico and India, 40 weeks | HbA1c change of -1.69% to -1.94% against -0.81%; body weight change of -11.5% to -15.3% against -2.6% [2] |
| 2026 | Atrial tissue (40613938) | Isolated human tissue | Right atrial samples from heart surgery | Force of contraction rose from 10 nM [11] |
The ranges span several trial groups, each assigned a different strength of the sponsor's investigational product. Every row describes what one study reported for its own population under trial conditions.
More trials are registered and running. The TRIUMPH programme consists of four phase 3 trials in over 5,800 participants covering obesity, obstructive sleep apnoea and knee osteoarthritis. [15] TRANSCEND-CKD, a phase 2b trial, randomised 146 adults with overweight or obesity and chronic kidney disease, with measured kidney filtration at week 24 as its primary endpoint. [16] On 29 September 2026 both appeared in PubMed as design papers only.
What does the retatrutide evidence not show?
The retatrutide evidence does not show long-term effects, independent replication or anything about research-grade material. Five limits stand out.
- One sponsor. Eli Lilly funded every published human trial in the table. [7][8][9][2] No independent group has published a randomised trial.
- Short follow-up. The longest published trial ran 48 weeks. [8] Sport Integrity Australia notes that the long-term safety profile has not been fully investigated. [3]
- One published phase 3 trial. TRANSCEND-T2D-1 studied type 2 diabetes. Phase 3 obesity results have been reported through a company news release, [17] and on 29 September 2026 they were not in the peer-reviewed record we searched.
- No published head-to-head trial with tirzepatide. The comparison section below covers what the indirect data allow.
- No trial used research-grade material. Every participant received the sponsor's product. A 2026 case report on an online-bought product marketed as retatrutide notes that the composition and purity of such products may be uncertain. [18] For a research vial, the batch certificate is what answers identity and purity.
What adverse events have studies of retatrutide reported?
Gastrointestinal events were the most common adverse events in every published retatrutide trial, and most were rated mild to moderate. Rates differ by trial, population and study group, so each figure below belongs to its own trial.
| Study (PMID) | Population | Reported adverse events |
|---|---|---|
| Phase 1b (36354040) | 72 adults with type 2 diabetes, 12 weeks | Treatment-emergent adverse events in 63% on retatrutide, 60% on dulaglutide and 54% on placebo; gastrointestinal disorders most frequent [7] |
| Phase 2, obesity (37366315) | 338 adults, 48 weeks | Gastrointestinal events mostly mild to moderate and larger in higher-strength groups; heart rate increases peaked at 24 weeks and declined thereafter [8] |
| Phase 2, type 2 diabetes (37385280) | 281 adults, 36 weeks | Gastrointestinal events in 35% on retatrutide, 13% on placebo and 35% on dulaglutide; no severe hypoglycaemia and no deaths [9] |
| Body composition substudy (40609566) | 189 adults with type 2 diabetes | Serious adverse events in 7% on placebo and 0% to 9% across retatrutide groups; no deaths [14] |
| TRANSCEND-T2D-1 (42250575) | 537 adults with type 2 diabetes, 40 weeks | Gastrointestinal events generally mild to moderate and subsided over time; discontinuation for adverse events in 2% to 5% against 0% on placebo; no severe hypoglycaemia; two deaths in one retatrutide group, reported as unrelated [2] |
The phase 2 obesity trial also reported that gastrointestinal events were partly reduced in groups that started at a lower strength. [8]
Reports from outside trials concern products sold online. A 2026 case report describes a man in his mid-30s with type 1 diabetes who developed severe vomiting, diarrhoea, hyperglycaemia, ketonaemia and acute kidney injury after using an online-purchased product marketed as retatrutide. His stool culture grew Shigella, and the authors state that causation cannot be established. [18] Healthy Male reports that a Victorian Government health warning linked products sold as retatrutide to six cases of acute liver injury. [17] The TGA lists adverse events it has received for unapproved peptide products as a group, including severe allergic reactions requiring hospitalisation and systemic inflammatory response syndrome. [10]
Is retatrutide approved or scheduled in Australia?
Retatrutide is not a registered medicine in Australia, and it is not named in the Poisons Standard. Sport Integrity Australia states that the TGA has not approved it as a registered medicine. [3] The June 2026 Poisons Standard instrument (F2026L00633), which commenced on 1 June 2026, has no entry for retatrutide. [4]
"Not named in the Poisons Standard" is a narrow statement about one instrument's text. The TGA's position on unapproved peptide products goes further. Its 2026 safety alert [17] names retatrutide among examples of unapproved peptide products and states that these products have not been evaluated by the TGA for safety, quality or effectiveness. The same alert states that a "research use only" disclaimer does not change a product's regulatory status, does not permit importation and does not remove advertising or supply obligations. It adds that state and territory laws may impose further controls. [10] Our guide to Australian peptide law and the Poisons Standard explains how the schedules and these rules fit together.
For sport, retatrutide is not named on the WADA 2026 Prohibited List, effective 1 January 2026. [19] Sport Integrity Australia's retatrutide page states that it is not listed on the Prohibited List. [3] The List's S0 class prohibits at all times any pharmacological substance not addressed elsewhere and without current governmental approval for human therapeutic use, including drugs under clinical development. [19] We have not confirmed whether S0 applies to retatrutide, so athletes should check with Sport Integrity Australia. Sport Integrity Australia also warns that peptides sold online may be contaminated with prohibited substances. [3]
How does retatrutide compare with tirzepatide and semaglutide?
Retatrutide adds a third receptor target to a class that started with one. Semaglutide acts only at the GLP-1 receptor, [17] tirzepatide acts at the GIP and GLP-1 receptors, and retatrutide adds the glucagon receptor. [1]
| Feature | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Receptor targets | GLP-1 | GIP and GLP-1 | GIP, GLP-1 and glucagon |
| Poisons Standard, June 2026 | Schedule 4 | Schedule 4 | No entry |
| WADA 2026 List | Not named | Not named | Not named |
| WADA Monitoring Program | Markers listed | Markers listed | Not stated |
The scheduling row comes from the June 2026 instrument [4] and the monitoring row from Sport Integrity Australia. [3] Our tirzepatide vs retatrutide comparison lines up the two sequences position by position. All three compounds sit in our metabolic research peptides range.
How is retatrutide stored and handled in the lab?
No published study covers the storage or stability of retatrutide. We checked all 194 PubMed records for retatrutide on 29 September 2026 and found none, and every human trial used the sponsor's own formulation.
Research retatrutide ships as lyophilised powder. Keep sealed vials cold, dry and away from light until use. After reconstitution, label each vial with the solvent, the concentration in mg per mL and the date, and keep the solution refrigerated. Our peptide storage guide covers temperatures, freeze-thaw and labelling for lyophilised and reconstituted peptides.
No published source names a reconstitution solvent for research retatrutide either. Published chemistry work describes how the peptide is made: synthesis relies mainly on solid-phase peptide synthesis, and a 2026 paper describes a liquid-phase alternative. [20] For laboratory reconstitution we stock BAC Water and acetic acid, each in 3ml vials for A$8. The peptide reconstitution guide explains how to choose between them and how to calculate a concentration.
Where can researchers buy retatrutide in Australia?
Peptides Collective sells retatrutide for laboratory research use only, in 10mg vials for A$128 and 20mg vials for A$228. That works out at A$12.80 per mg for the 10mg vial and A$11.40 per mg for the 20mg vial. Stock ships from Western Australia with tracking.
An independent lab tests every batch before it goes on sale. The certificate reports purity by HPLC and identity by mass spectrometry, and it is published under the batch number printed on the vial. Search the certificate of analysis library by that number and check the identity result against the molar mass in the structure table, about 4731 g/mol. The retatrutide product page lists both strengths.
Read the legal section above before you order. The TGA's alert on unapproved peptide products applies to retatrutide by name. [10]
Bottom line
Retatrutide is an investigational 39-amino-acid peptide that activates the GIP, GLP-1 and glucagon receptors, with a half-life of about 6 days. Its human evidence is recent, short and funded by its developer, with one published phase 3 trial. In Australia it is unregistered, absent from the Poisons Standard and named in a TGA alert, and WADA's 2026 List does not name it. For a research vial, the batch certificate is the evidence of what the vial contains.
Questions
What has research on retatrutide examined?
Research on retatrutide has examined cell assays, obese mice, isolated heart tissue and randomised human trials. Four published trials enrolled 1,228 adults with type 2 diabetes or obesity, from a 12-week phase 1b study to the 40-week TRANSCEND-T2D-1 phase 3 trial. Substudies examined liver fat and body composition.
Can I buy retatrutide in Australia?
Peptides Collective sells retatrutide for laboratory research use only, from A$128 for a 10mg vial, with a certificate for every batch. Retatrutide is not a registered medicine in Australia. The TGA names it in a 2026 alert on unapproved peptide products and states that a research-use disclaimer does not change a product's regulatory status.
What adverse events have studies of retatrutide reported?
Gastrointestinal events, mostly mild to moderate, were the most common adverse events in every published trial. In the phase 2 type 2 diabetes trial they occurred in 35% on retatrutide against 13% on placebo. The phase 2 obesity trial reported heart rate increases that peaked at 24 weeks. In the phase 3 trial, 2% to 5% stopped for adverse events against 0% on placebo.
Is retatrutide a prescription medicine in Australia?
No. Retatrutide is not a registered medicine in Australia and has no entry in the June 2026 Poisons Standard, so it holds no Schedule 4 listing. Sport Integrity Australia states that no regulator, the TGA included, has approved it for therapeutic use. It remains in clinical development.
Is retatrutide banned in sport?
Retatrutide is not named on the WADA 2026 Prohibited List, and Sport Integrity Australia states it is not listed. Class S0 prohibits substances with no current governmental approval for human therapeutic use, including drugs under clinical development. We have not confirmed whether S0 applies, so athletes should check with Sport Integrity Australia.
What is the half-life of retatrutide?
The half-life of retatrutide was approximately 6 days in its phase 1b trial in 72 adults with type 2 diabetes. The figure comes from a sponsor trial of the investigational product.
What is the molecular weight of retatrutide?
PubChem lists the molar mass of retatrutide as 4731 g/mol for the formula C221H342N46O68. That is the free peptide. PubChem holds a separate record for a sodium salt, so check which form a lab used before you compare a mass spectrometry result with the published value.
How should retatrutide be stored?
No published study covers retatrutide storage or stability. Keep sealed lyophilised vials cold, dry and away from light. After reconstitution, refrigerate the solution and label it with the solvent, concentration and date. The peptide storage guide covers freeze-thaw and labelling in detail.
Which solvent is used to reconstitute retatrutide?
No published source names a reconstitution solvent for research retatrutide, because every trial used the sponsor's own formulation. For laboratory reconstitution, Peptides Collective stocks BAC Water and acetic acid, each in 3ml vials for A$8. Record the solvent and the mg per mL concentration on the vial label.
Where does the retatrutide sequence come from?
The retatrutide sequence is a synthetic design with no natural counterpart; a 2026 paper calls it "a not endogenously occurring peptide". PubChem's systematic name gives the 39 residues, with Aib at positions 2 and 20, alpha-methyl-leucine at 13 and a C20 fatty diacid on lysine 17.
Who discovered retatrutide?
Researchers at Eli Lilly and Company discovered retatrutide. The first full description appeared in Cell Metabolism in 2022 under the code LY3437943, with Coskun and colleagues as authors. Lilly continues to develop it and funded the published human trials.
Is retatrutide a peptide or a small molecule?
Retatrutide is a peptide. It is a 39-amino-acid chain with a C20 fatty diacid side chain and a molar mass of 4731 g/mol, which makes it a lipidated peptide of about 4.7 kDa.
What is the CAS number for retatrutide?
The CAS number for retatrutide is 2381089-83-2. It appears on the PubChem substance record deposited by ChemIDplus, alongside the development code LY3437943. The matching PubChem compound record is CID 171390338.
How is retatrutide made?
Retatrutide is made by chemical peptide synthesis. A 2026 paper in Organic Letters states that its synthesis relies mainly on solid-phase peptide synthesis, and it describes a hydrophobic tag-assisted liquid-phase method as an alternative. The fatty diacid side chain is attached to lysine 17 during manufacture.
Sources
- 1. 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.
- 2. Bajaj HS et al. Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. Lancet, 2026.
- 3. Sport Integrity Australia (Australian Government)
- 4. Federal Register of Legislation, Australian Government (excerpt captured by sibling worker 2026-09-29)
- 5. PubChem, National Center for Biotechnology Information
- 6. PubChem substance record deposited by ChemIDplus
- 7. Urva S et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. Lancet, 2022.
- 8. Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med, 2023.
- 9. 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.
- 10. Therapeutic Goods Administration (Australian Government)
- 11. Neumann J et al. Inotropic effects of retatrutide in isolated human atrial preparations. Naunyn Schmiedebergs Arch Pharmacol, 2026.
- 12. Neumann J et al. Contractile effects of retatrutide in isolated mouse atrial preparations. Naunyn Schmiedebergs Arch Pharmacol, 2025.
- 13. Sanyal AJ et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nat Med, 2024.
- 14. 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.
- 15. Giblin K et al. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials. Diabetes Obes Metab, 2026.
- 16. Heerspink HJL et al. Rationale, design and baseline characteristics of the TRANSCEND-CKD trial of retatrutide in patients with chronic kidney disease. Nephrol Dial Transplant, 2026.
- 17. Healthy Male (Andrology Australia), 12 May 2026
- 18. Branine N et al. Online-Sourced Retatrutide Complicating Impending Diabetic Ketoacidosis in a Patient With Type 1 Diabetes and Concurrent Shigella Gastroenteritis. Cureus, 2026.
- 19. World Anti-Doping Agency, 2026 Prohibited List (excerpt captured by sibling worker 2026-09-29)
- 20. Mao CY et al. A Hydrophobic Tag-Assisted Liquid-Phase Strategy for the Synthesis of Retatrutide. Org Lett, 2026.
