Retatrutide Research, Specifications & Scientific Information

Introduction

Retatrutide is a synthetic peptide developed by Eli Lilly and Company under the development code LY3437943. What makes it unusual is arithmetic: where most peptides in the incretin field act at one receptor and the newer ones act at two, retatrutide is a single molecule that activates three — the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor, and the glucagon receptor ^[1]. That third arm, glucagon receptor agonism, is what separates it pharmacologically from the dual and single agonists already on the market, and it is the reason the compound attracted attention well before any late-stage result existed.

This page is a reference record. It sets out what has been published about retatrutide's structure, its receptor pharmacology, and the clinical and preclinical literature, with every source resolved against PubMed, Crossref or ClinicalTrials.gov at the time this page was built. It describes research. It does not describe use in people or animals, and it contains no guidance of any kind on handling the material.

What Is Retatrutide?

Retatrutide is an investigational synthetic peptide. It is not an approved medicine in the United States and has not been approved by the U.S. Food and Drug Administration for any indication.

Structurally it belongs to the glucagon–secretin peptide superfamily: the group that contains glucagon, GLP-1, GIP and their analogues. Functionally it is a triple receptor agonist, meaning one molecule binds and activates three distinct class B1 G protein-coupled receptors rather than the one or two that earlier compounds in this family engage ^[1].

The compound was first described in the peer-reviewed literature in 2022, in a paper that reported its discovery, its in vitro receptor profile, rodent studies, and a first-in-human single-administration study in one publication ^[1]. Clinical development followed quickly: a phase 1b study in type 2 diabetes later the same year ^[2], two phase 2 trials reported in 2023 ^{[3, 4]}, and a phase 3 programme that has since completed and begun reporting ^{[6, 7]}.

Development names persist in the literature and in supplier listings, so the same material is referred to as retatrutide, as LY3437943, and occasionally as the "GGG" tri-agonist after the three receptors it engages.

Retatrutide Specifications

The 39-residue backbone above is the sequence recorded for retatrutide in the FDA/NCATS Global Substance Registration System under UNII NOP2Y096GV, written in single-letter code. That register records the backbone only; it carries no structural modifications for this substance, so the single-letter string should not be read as the complete covalent structure. The molecule described in the discovery literature is a glucagon-family analogue built on a modified GIP backbone, stabilised at the positions most exposed to dipeptidyl peptidase-4 cleavage by non-standard residues, and acylated on a lysine side chain with a fatty diacid through a hydrophilic linker — the same class of albumin-binding modification that gives this family of peptides a once-weekly plasma half-life. The molecular formula and mass shown here are the values carried in the supplier catalog for the material offered as a laboratory reagent and correspond to the acylated, fully modified molecule rather than to the bare backbone; the register's calculated mass for the unmodified 39-residue chain is 4091.5 g/mol, and the difference between the two figures is the modification chemistry. Any figure on this page is a reference value: the certificate of analysis supplied with a laboratory order is the record for a given lot.

Values that a public register does not carry are shown as not publicly characterised rather than estimated. Identifiers are reference values; the certificate of analysis supplied with a laboratory order is the record for a given lot.

How Does Retatrutide Work?

All three of retatrutide's targets are class B1 G protein-coupled receptors, and all three couple through Gs to raise intracellular cyclic AMP. The pharmacological interest lies in the fact that the three receptors sit in different tissues and drive different processes, so activating them together is not the same as activating any one of them harder.

The GIP and GLP-1 receptor arms are the familiar incretin pharmacology: receptors expressed on pancreatic islet cells and in the central nervous system, whose activation modulates glucose-dependent insulin secretion and reduces calorie intake. The glucagon receptor arm is the departure. Glucagon receptor signalling in the liver and in adipose tissue raises whole-body metabolic rate — historically the reason glucagon agonism was avoided in diabetes work, since unopposed glucagon action raises blood glucose.

The design premise reported in the discovery paper is that combining the three lets the glucagon arm contribute an increase in metabolic rate while the incretin arms hold glucose in check, so that the glycaemic liability of glucagon agonism is offset within the same molecule ^[1].

Retatrutide Mechanism of Action

In vitro research

In cell-based receptor assays, retatrutide showed balanced activity at the glucagon and GLP-1 receptors and relatively greater activity at the GIP receptor ^[1]. That imbalance is deliberate rather than incidental: the relative potencies at the three receptors are the tunable parameters of a multi-agonist, and they are what distinguishes one tri-agonist from another far more than the backbone sequence does.

The molecule carries the structural modifications that this class of peptide has converged on. The backbone is stabilised against dipeptidyl peptidase-4, the enzyme that clears native incretins within minutes, and a fatty diacid is attached to a lysine side chain through a hydrophilic linker. That acylation binds the peptide reversibly to serum albumin, which is what converts a molecule with a half-life measured in minutes into one with a half-life measured in days ^[1].

Reported pharmacokinetics in early clinical study were approximately proportional to the amount administered, with a plasma half-life of roughly six days — the property that supports the once-weekly schedules used throughout the trial programme ^[2].

What Is Retatrutide Being Researched For?

Registered clinical research on retatrutide has covered, in order of how far each has progressed:

• Type 2 diabetes mellitus — phase 1b, phase 2 and phase 3 trials ^{[2, 4, 6]}.
• Obesity and overweight — phase 2 and a phase 3 registrational programme ^{[3, 7]}.
• Metabolic dysfunction-associated steatotic liver disease — a phase 2a substudy of the obesity trial ^[5].
• Osteoarthritis of the knee in the context of obesity — a phase 3 trial within the registrational programme ^[14].
• Cardiovascular disease in the context of obesity — a phase 3 trial within the registrational programme ^[13].
• Chronic kidney disease — registered phase 2 and phase 3 work.

Each of those is research into a pharmaceutical product candidate, conducted by its sponsor under a registered protocol. None of it is research into, or evidence about, research-grade material supplied for laboratory use.

Human Research on Retatrutide

Human clinical research

Results from pharmaceutical clinical trials describe the investigational material and populations used in those studies and should not be interpreted as establishing the effects of research-grade materials offered for laboratory use.

Phase 1b, multiple-ascending administration in type 2 diabetes

Population. 72 adults aged 20–70 with type 2 diabetes of at least three months' standing, HbA1c 7.0–10.5%, BMI 23–50 kg/m², recruited at four centres in the United States ^{[2, 8]}.

Endpoint and duration. The primary outcome was safety and tolerability over 12 weeks; pharmacokinetics and pharmacodynamics were secondary ^[2].

Result. Pharmacokinetics were proportional to the amount administered, with a half-life of approximately six days. At week 12, placebo-adjusted mean daily plasma glucose fell significantly in the three highest groups, and placebo-adjusted HbA1c fell by 1.2% to 1.6% in those groups. Placebo-adjusted body-weight reduction reached 8.96 kg in the highest group ^[2].

Adverse events. Treatment-emergent adverse events were reported by 63% of participants receiving retatrutide against 54% receiving placebo, gastrointestinal disorders being the most frequent ^[2].

Limitations. A small, short, early-phase study whose primary purpose was safety, not efficacy; 29 of 72 participants discontinued prematurely.

Phase 2 in obesity

Population. 338 adults with BMI ≥ 30, or BMI 27 to under 30 with at least one weight-related condition; 51.8% men ^{[3, 9]}.

Endpoint and duration. Primary endpoint the percentage change in body weight at 24 weeks, with 48-week change and responder thresholds as secondary endpoints. Randomised, double-blind, placebo-controlled, once-weekly subcutaneous administration for 48 weeks ^[3].

Result. At 24 weeks, least-squares mean change in body weight was −7.2% (1 mg), −12.9% (combined 4 mg), −17.3% (combined 8 mg) and −17.5% (12 mg), against −1.6% for placebo. At 48 weeks the corresponding figures were −8.7%, −17.1%, −22.8% and −24.2%, against −2.1% for placebo. At 48 weeks, reductions of 15% or more had occurred in 60% of the 4 mg group, 75% of the 8 mg group and 83% of the 12 mg group, against 2% for placebo ^[3].

Adverse events. The most common were gastrointestinal, graded with the amount administered, mostly mild to moderate, and partially mitigated by a lower starting amount. Increases in heart rate peaked at 24 weeks and declined thereafter ^[3].

Limitations. Phase 2, 338 participants, 48 weeks. It was designed to characterise the relationship between the amount administered and the response, not to establish long-term safety or outcomes.

Phase 2 in type 2 diabetes

Population. 281 adults aged 18–75 with type 2 diabetes, HbA1c 7.0–10.5%, BMI 25–50 kg/m², on diet and exercise alone or on stable metformin; recruited at 42 sites in the United States ^{[4, 10]}.

Endpoint and duration. Primary endpoint change in HbA1c at 24 weeks; secondary endpoints HbA1c and body weight at 36 weeks. Placebo-controlled and active-controlled against dulaglutide 1.5 mg ^[4].

Result. At 24 weeks, least-squares mean HbA1c change ranged from −0.43% in the lowest group to −2.02% in the 12 mg group, against −0.01% for placebo and −1.41% for dulaglutide. Reductions were significantly greater than placebo in every group but the lowest, and greater than dulaglutide in the 8 mg slow-escalation and 12 mg groups. Body weight at 36 weeks fell by 3.19% to 16.94% across the retatrutide groups, against 3.00% for placebo and 2.02% for dulaglutide ^[4].

Adverse events. Mild-to-moderate gastrointestinal events — nausea, diarrhoea, vomiting, constipation — in 35% of retatrutide participants against 13% on placebo and 35% on dulaglutide. No severe hypoglycaemia and no deaths during the study ^[4].

Limitations. 281 participants over 36 weeks, 84% of them White, with an active comparator at a mid-range amount rather than at its maximum.

Phase 2a substudy in metabolic dysfunction-associated steatotic liver disease

Population. 98 participants drawn from the phase 2 obesity trial who had metabolic dysfunction-associated steatotic liver disease and at least 10% liver fat ^[5].

Endpoint and duration. Mean relative change from baseline in liver fat at 24 weeks, within a 48-week randomised, double-blind, placebo-controlled design ^[5].

Result. Mean relative change in liver fat at 24 weeks was −42.9%, −57.0%, −81.4% and −82.4% across the four retatrutide groups against +0.3% for placebo, all p < 0.001. Normal liver fat, defined as under 5%, was reached by 27%, 52%, 79% and 86% of those groups against none on placebo. Liver-fat change was significantly related to change in body weight, abdominal fat, and measures associated with insulin sensitivity and lipid metabolism ^[5].

Limitations. A substudy of 98 people, with imaging rather than histology as the endpoint, and no measure of the fibrosis that determines outcome in liver disease.

Phase 3 monotherapy in type 2 diabetes (TRANSCEND-T2D-1)

Population. 537 adults with type 2 diabetes inadequately controlled by diet and exercise alone, HbA1c 7.0–9.5%, BMI ≥ 23 kg/m², at 48 sites in the United States, Mexico and India ^{[6, 15]}.

Endpoint and duration. Primary endpoint change in HbA1c from baseline to week 40; key secondary endpoint percentage change in body weight at week 40 ^[6].

Result. Mean HbA1c change was −1.69% (4 mg), −1.86% (9 mg) and −1.94% (12 mg) against −0.81% for placebo, giving treatment differences against placebo of −0.88%, −1.04% and −1.12%, all p < 0.0001. Mean percentage change in body weight was −11.5%, −13.9% and −15.3% against −2.6% for placebo ^[6].

Adverse events. Predominantly mild-to-moderate gastrointestinal events that subsided over time. Discontinuations for adverse events were 2–5% with retatrutide and 0% with placebo. No severe hypoglycaemia. Two deaths occurred, both in the 4 mg group, neither attributed to the study drug ^[6].

Limitations. Forty weeks, monotherapy, in a population with a mean diabetes duration of 2.5 years — early disease, and no active comparator.

Preclinical Research on Retatrutide

Animal research

The rodent work reported alongside the discovery of the compound is what established that the three receptor arms contribute differently, and it is the clearest illustration of why a tri-agonist is not simply a stronger incretin agonist.

In diet-induced obese mice, administration of the compound reduced body mass and improved glycaemic control. The authors attribute the body-mass reduction to two separable contributions: a reduction in calorie intake driven by the GIP and GLP-1 receptor arms, and an increase in whole-body metabolic rate driven by the glucagon receptor arm, added on top ^[1].

That decomposition matters more than the magnitude of any rodent figure. It is the mechanistic claim the whole tri-agonist programme rests on — that glucagon receptor agonism adds a route to metabolic change that incretin agonism alone does not reach — and it was demonstrated in mice before any human study existed.

Rodent models of diet-induced obesity are a standard preclinical tool and a poor predictor of human results in this field specifically. Findings described in this section were observed in animals, and nothing in them establishes anything about humans.

Other Areas of Retatrutide Research

Human clinical research

Results from pharmaceutical clinical trials describe the investigational material and populations used in those studies and should not be interpreted as establishing the effects of research-grade materials offered for laboratory use.

Beyond diabetes and obesity, the registrational programme has been extended into conditions where obesity is a driver rather than a comorbidity. The TRIUMPH trials were designed as a linked set covering obesity itself, obstructive sleep apnea, and osteoarthritis of the knee ^[7]. Of these, TRIUMPH-1 enrolled 2,335 participants without type 2 diabetes ^[11], TRIUMPH-2 enrolled 1,152 participants with type 2 diabetes ^[12], TRIUMPH-3 enrolled 1,946 participants with obesity and cardiovascular disease ^[13], and TRIUMPH-4 enrolled 445 participants with osteoarthritis of the knee ^[14]. All four have completed their primary phases.

Separate registered work covers chronic kidney disease and cardiovascular and kidney outcomes, and a phase 2b trial examined renal function in participants with overweight or obesity and chronic kidney disease.

The lipid biology has also been examined: circulating ANGPTL3/8 concentrations fell in parallel with serum lipids in treated participants, which is of mechanistic interest because that complex is a regulator of lipoprotein lipase activity.

Two points bound all of it. First, every one of these programmes studies pharmaceutical-grade investigational material manufactured to a regulatory standard, administered under a protocol, in a defined population, under clinical supervision. Second, none of them has produced an approval: the compound remains investigational.

Current Research Status

Status as of September 21, 2026. This block is rendered from maintained fields, not from prose, so it cannot go stale in one place and stay current in another.

Retatrutide vs Related Compounds

The distinction between retatrutide and the compounds it is usually set beside is the number of receptors each engages, and nothing else stated here.

Receptor agonism

Semaglutide — GLP-1R. Tirzepatide — GIPR and GLP-1R. Retatrutide — GIPR, GLP-1R and GCGR.

The added arm

Retatrutide's third target is the glucagon receptor. That is the pharmacological difference; it is also the reason the compound was harder to develop, since glucagon agonism alone raises blood glucose ^[1].

Regulatory position

Semaglutide and tirzepatide are approved medicines in the United States in defined indications. Retatrutide is not approved for anything. Approval is specific to a compound and an indication and does not extend across a pharmacological class.

Other triple agonists

Survodutide and mazdutide are also glucagon-containing multi-agonists in clinical development; cagrisema combines a GLP-1 receptor agonist with an amylin analogue. Comparative trials between these compounds are limited.

No comparison of effect between these compounds is made on this page. Where head-to-head trials exist they are registered, and their results belong to the papers that report them.

Chemical & Molecular Characteristics

Retatrutide is a modified 39-residue peptide. The backbone recorded in the FDA/NCATS Global Substance Registration System under UNII NOP2Y096GV is YAQGTFTSDYSILLDKKAQAAFIEYLLEGGPSSGAPPPS, and that register also carries CAS registry number 2381089-83-2.

Three cautions apply to those figures, and they are the reason this section exists separately from the specification table above.

The register's sequence is the backbone only. The GSRS record for retatrutide carries no structural modifications, so the single-letter string is not the complete covalent structure. The register's own calculated mass for that bare chain is 4091.5 g/mol, against the 4731.3 g/mol carried for the finished molecule — a difference of roughly 640 daltons, which is the modification chemistry rather than a discrepancy.

Single-letter code cannot express non-standard residues. Peptides in this family are routinely stabilised at the positions most exposed to dipeptidyl peptidase-4 by substituting residues that have no single-letter representation, and those substitutions are written out in the discovery literature rather than in the register ^[1]. Reading the string above as if every letter were a standard amino acid would be a mistake.

No PubChem compound identifier resolves. Queries to PubChem's PUG REST service for the name retatrutide and for LY3437943 return no compound identifier. The field is therefore published as unknown. It is left blank rather than filled with a plausible number, which is the general rule on these pages.

The molecular formula C221H342N46O68 and the molecular weight 4731.3 g/mol are the values carried in the supplier catalog for the material offered as a laboratory reagent, and they correspond to the acylated, fully modified molecule.

Analytical Specifications

Analytical figures are lot-specific. Fields the catalog does not carry for the current lot are omitted rather than filled with a typical value. The certificate of analysis and the safety data sheet for the exact lot supplied are provided with a laboratory order; no purity figure on this page is a substitute for that document.

Frequently Asked Questions

Scientific References

1. Coskun T, Urva S, Roell WC, 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 metabolism; 2022. PMID 35985340 doi:10.1016/j.cmet.2022.07.013
2. Urva S, Coskun T, Loh MT, 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 (London, England); 2022. PMID 36354040 doi:10.1016/S0140-6736(22)02033-5
3. Jastreboff AM, Kaplan LM, Frías JP, et al.. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial The New England journal of medicine; 2023. PMID 37366315 doi:10.1056/NEJMoa2301972
4. Rosenstock J, Frias J, Jastreboff AM, 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 (London, England); 2023. PMID 37385280 doi:10.1016/S0140-6736(23)01053-X
5. Sanyal AJ, Kaplan LM, Frias JP, et al.. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial Nature medicine; 2024. PMID 38858523 doi:10.1038/s41591-024-03018-2
6. Bajaj HS, Welch M, Shah P, 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 (London, England); 2026. PMID 42250575 doi:10.1016/S0140-6736(26)00967-0
7. Giblin K, Kaplan LM, Somers VK, et al.. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials Diabetes, obesity & metabolism; 2026. PMID 41090431 doi:10.1111/dom.70209
8. A Study of LY3437943 in Participants With Type 2 Diabetes Mellitus (T2DM) 2019. NCT04143802
9. A Study of LY3437943 in Participants Who Have Obesity or Are Overweight 2021. NCT04881760
10. A Study of LY3437943 in Participants With Type 2 Diabetes 2021. NCT04867785
11. A Study of Retatrutide (LY3437943) in Participants Who Have Obesity or Overweight 2023. NCT05929066
12. A Study of Retatrutide (LY3437943) in Participants With Type 2 Diabetes Mellitus Who Have Obesity or Overweight 2023. NCT05929079
13. A Study of Retatrutide (LY3437943) in Participants With Obesity and Cardiovascular Disease 2023. NCT05882045
14. A Study of Retatrutide (LY3437943) Once Weekly in Participants Who Have Obesity or Overweight and Osteoarthritis of the Knee 2023. NCT05931367
15. Effect of Retatrutide Compared With Placebo in Adult Participants With Type 2 Diabetes and Inadequate Glycemic Control With Diet and Exercise Alone (TRANSCEND-T2D-1) 2024. NCT06354660

Every identifier above is resolved against PubMed, Crossref or ClinicalTrials.gov at build time, and the title returned by the register is compared with the title stored here. A page does not publish if a reference fails to resolve.

Research-Use Information

For in vitro research use only. This material is a laboratory reagent. It is not a drug, food, dietary supplement, or cosmetic and is not for human or veterinary use, including ingestion, injection, or any other administration. No information on this page describes or implies any effect in humans or animals. Sold only to researchers under our Terms of Sale.

Related laboratory reagent: Retatrutide specifications and lot documentation