RETATRUTIDE 5 mg

Retatrutide (LY3437943) 5 mg — triple agonist research reagent

Retatrutide (LY3437943), informally referred to as “Triple G”, is a synthetic peptide supplied here as a high-purity reference reagent for laboratory research. It is a GLP-1/GIP/glucagon triple agonist (GLP-1R/GIPR/GCGR) from the incretin class, presented as a lyophilized powder at 5 mg per vial with ≥98% HPLC purity and a batch-specific COA. Offered exclusively as a Research Use Only reference reagent for laboratory research; not for human consumption, therapeutic, or diagnostic use.

The informal shorthand used for retatrutide in online searches is explained in a separate entry: “reta”: where the name comes from.

This page summarises the chemical identity, analytical specification, neutral receptor pharmacology and published clinical-trial literature describing the investigational molecule. All trial figures below are reported in the past tense, with attribution, and describe the molecule studied in human research — not properties of the research reagent supplied from this catalog.

Chemical identity and analytical specification

Retatrutide is a synthetic peptide composed of 39 amino acids, engineered on the framework of the natural GIP scaffold with fatty-acid acylation and stabilising substitutions that extend its half-life. It is classified as a GLP-1R/GIPR/GCGR triple agonist (Eli Lilly internal designation LY3437943). The research reagent from this catalog is supplied as a lyophilized powder and is characterised by a per-batch certificate of analysis (COA). Offered exclusively as a Research Use Only reference reagent for laboratory research; not for human consumption, therapeutic, or diagnostic use.

Key molecular parameters

Analytical specification (research reagent)

Retatrutide as a research reagent from this catalog meets the following quality criteria. Each vial is marked with a batch number associated with a certificate of analysis (COA).

Stability and storage

• Lyophilisate: store at -20°C.
• Solution after reconstitution: store refrigerated at 2–8°C; reconstitute according to standard laboratory procedure.
• Freeze/thaw: aliquoting is recommended to limit repeated freeze/thaw cycles.

Classification & quality

This is a Research Use Only reference reagent — not a medicine or supplement — which is exactly why every batch ships with HPLC/MS COA and full traceability. The analytical documentation (RP-HPLC purity, ESI-MS identity, Karl Fischer moisture, LAL endotoxin testing) accompanies each batch so that laboratories can confirm identity and purity before use. Offered exclusively as a Research Use Only reference reagent for laboratory research; not for human consumption, therapeutic, or diagnostic use.

How retatrutide works — three receptors, one molecule

Retatrutide is a triple agonist that simultaneously stimulates three incretin-axis receptor types: GLP-1, GIP and glucagon (GLP-1R/GIPR/GCGR). Each of these three receptors has a distinct function in the regulation of metabolism, appetite-regulating circuits and energy management, and the coordinated activation of all three in a single molecule is the defining feature of this compound. The following sections describe the receptor pharmacology as a neutral mechanistic overview.

GLP-1 receptor

The GLP-1 (glucagon-like peptide 1) receptor is a well-characterised target in metabolic research. Its activation slows gastric emptying, increases the feeling of satiety after a meal, stimulates glucose-dependent insulin secretion, and modulates appetite-regulating pathways via hunger centres in the brain. This is the action on GLP-1 that characterises compounds such as semaglutide.
Retatrutide shows slightly lower activity towards this receptor compared with native GLP-1. Moderate GLP-1 activation combined with strong effects on the other two receptors produces a balanced pharmacological profile that has been characterised in the literature.

GIP receptor

The GIP (glucose-dependent insulinotropic polypeptide) receptor is the second component. GIP is an incretin hormone secreted after a meal that cooperates with GLP-1 to regulate glucose levels. It stimulates insulin secretion from pancreatic beta cells and acts on adipose tissue and the nervous system. The literature indicates that GIP also participates in appetite-regulating pathways.
Retatrutide has particularly strong activity towards the GIP receptor — stronger than towards the natural hormone. This pronounced GIP stimulation combined with GLP-1 activation is associated with pronounced activity on glucose-regulation and satiety signaling in the cited studies.

Glucagon receptor

The third element of the triple mechanism is activation of the glucagon receptor (GCGR). Glucagon is classically associated with regulating blood glucose — it stimulates the liver to release glucose between meals — but its pharmacological role extends further.
In published work, glucagon-receptor activation has been associated with reduced lipogenesis, increased lipolysis, increased fatty-acid oxidation in the liver, reduced gastrointestinal motility, and, in animal studies, stimulation of thermogenesis in brown adipose tissue as a studied mechanism of increased energy expenditure. The addition of the glucagon component is the pharmacological feature that distinguishes retatrutide from earlier incretin compounds: glucagon-receptor activation represents a third pharmacological axis, and preclinical work associates it with increased thermogenesis and energy expenditure as a studied mechanism.

What phase 2 trials reported

The following figures review published research on the investigational molecule. They describe retatrutide studied in human trials and are not properties of the reference reagent supplied from this catalogue. Offered exclusively as a Research Use Only reference reagent for laboratory research; not for human consumption, therapeutic, or diagnostic use.

The most extensively described retatrutide study remains the 48-week phase 2 trial in adults with obesity (Jastreboff et al., 2023). At week 48, the mean body-weight change was −24.2% in the highest investigated group, compared with −2.1% with placebo; the intermediate groups showed changes of −8.7%, −17.1% and −22.8%, respectively. The placebo arm is essential for interpreting these figures.

A separate phase 2 study included people with type 2 diabetes, with both placebo and an active comparator, over a 36-week protocol (Rosenstock et al., 2023).

All figures above come from phase 2 trials. The phase III programme design has been described in a peer-reviewed publication; the manufacturer announced topline results separately in 2026, without peer-reviewed publication of those results.

Phase 3 registrational programme — what is being studied

Retatrutide is being evaluated in the TRIUMPH registrational programme, which comprises four phase 3 trials and more than 5,800 participants in total (Giblin et al., 2026). The programme covers body-weight management (TRIUMPH-1 and TRIUMPH-2, with nested obstructive sleep apnoea and osteoarthritis protocols), a population with cardiovascular disease (TRIUMPH-3), and a standalone knee-osteoarthritis study (TRIUMPH-4).

The programme’s four core trials have completed. Results from TRIUMPH-1, -2 and -3 are available as manufacturer-reported topline readouts (table below), not peer-reviewed results. The figures in the phase 2 section above come from published, peer-reviewed trials.

Source: Eli Lilly topline announcements dated 21 May 2026 and 23 July 2026. Manufacturer announcements, not peer-reviewed publications. The treatment-regimen estimand gives lower magnitudes of weight reduction.

Retatrutide and liver fat — the MASLD substudy

A substudy of the 48-week phase 2 obesity trial assessed liver-fat changes in 98 participants with metabolic dysfunction-associated steatotic liver disease (MASLD) and baseline liver fat of at least 10% (Sanyal et al., 2024).

At week 24, the reported relative liver-fat change ranged from −42.9% in the lowest investigated group to −82.4% in the highest, compared with +0.3% with placebo. Normal liver-fat content (<5%) was reported in 27% to 86% of participants across the investigated groups, compared with 0% in the placebo group.

The authors reported associations with changes in body weight and abdominal adipose tissue. These are phase 2 findings in a study population, not registrational data.

Retatrutide in type 2 diabetes — what phase 2 reported

Retatrutide has also been investigated in the context of type 2 diabetes. A 36-week phase 2 trial used placebo and an active comparator to assess glycaemic control and body-weight change (Rosenstock et al., 2023).

In the highest investigated group, the authors reported an HbA1c change of −2.02 percentage points at week 24 and a body-weight change of −16.94% at week 36. These findings come from a single phase 2 trial and are not registrational results.

Comparison of incretin agonist classes

The three agonist classes — single, dual and triple — placed side by side, using each compound’s landmark obesity trial:

⚠️ These figures come from clinical trials of approved or investigational medicines. They describe the molecules studied in human research — not outcomes of any research reagent, which is sold for laboratory use only. Sources: Wilding JPH et al., N Engl J Med 2021 (10.1056/NEJMoa2032183); Jastreboff AM et al., N Engl J Med 2022 (10.1056/NEJMoa2206038); Jastreboff AM et al., N Engl J Med 2023 (10.1056/NEJMoa2301972).

Adverse events reported in phase 2 trials

In the published phase 2 trials, the most frequently reported adverse events were gastrointestinal. Their frequency varied between investigated groups, and a lower starting level partially reduced the severity of some events (Jastreboff et al., 2023; Rosenstock et al., 2023).

Phase 2 data do not establish the molecule’s complete safety profile. The published TRIUMPH paper describes the phase 3 trial design and does not provide efficacy or safety outcomes from that programme.

Research directions covered by peer-reviewed literature

The peer-reviewed literature cited on this page covers phase 2 studies in obesity and type 2 diabetes, the MASLD substudy, and the rationale and design of the phase 3 TRIUMPH programme. These are study populations and research endpoints, not approved indications.

The catalogue product is offered exclusively as a Research Use Only reference reagent for analytical and laboratory work. Clinical-trial findings describe the investigational molecule and must not be interpreted as properties or directions for use of the supplied reagent.

Frequently asked questions about retatrutide

Related research compound in this catalogue: tirzepatide 5 mg, a dual GLP-1R/GIPR agonist reference reagent supplied with HPLC certification and batch documentation.

Research background: For a broader context on this compound class, see the GLP-1 and incretin research overview; for retatrutide specifically, see the retatrutide research overview.