Retatrutide [Peptide]

Description

What is Retatrutide?

Retatrutide (LY3437943) is a synthetic 39-amino-acid peptide developed by Eli Lilly and Company, classified as a triple hormone receptor agonist. Its sequence is based on a modified glucose-dependent insulinotropic polypeptide (GIP) backbone: Tyr-Aib-Gln-Gly-Thr-Phe-Thr-Ser-Asp-Tyr-Ser-Ile-αMeLeu-Leu-Asp-Lys-[C20 diacid linker]-Lys-Ala-Gln-Aib-Ala-Phe-Ile-Glu-Tyr-Leu-Leu-Glu-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2. The sequence incorporates three non-coded residues to enhance pharmacological stability: 2-aminoisobutyric acid (Aib) at positions 2 and 20 to resist enzymatic degradation, and alpha-methyl-leucine (α-Me-Leu) at position 13 to optimise receptor binding geometry. A C20 fatty diacid moiety attached at position 17 via a gamma-glutamic acid and aminoethoxyethoxyacetic acid (AEEA) linker extends systemic half-life by promoting albumin binding and slowing renal clearance.

Retatrutide is investigated in preclinical and clinical research contexts for its simultaneous agonism at three G protein-coupled receptors: the glucagon receptor (GCGR), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon-like peptide-1 receptor (GLP-1R). In the human receptor binding EC50 assay, Retatrutide binds GIPR with the highest potency (EC50: 0.0643 nM), followed by GLP-1R (EC50: 0.775 nM) and GCGR (EC50: 5.79 nM). 

Phase 3 clinical trials across obesity, type 2 diabetes, and MASLD indications have begun reporting. TRIUMPH-4 (December 2025) demonstrated 28.7% weight loss at 68 weeks in adults with obesity and knee osteoarthritis. TRANSCEND-T2D-1 (March 2026) demonstrated HbA1c reductions of 1.7–2.0 percentage points and weight loss of 11.5–16.8% in type 2 diabetes patients at 40 weeks. TRIUMPH-1 (May 2026) demonstrated 28.3% mean weight loss at 80 weeks in the pivotal general obesity population (2,339 participants). Eli Lilly has communicated NDA submission guidance for late 2026 to Q1 2027. Additional Phase 3 readouts are anticipated through 2026. [Topline data – peer-reviewed publications pending for TRIUMPH-1 and TRANSCEND-T2D-1] 

Retatrutide is not yet approved by the Food and Drug Administration for any indication. It is not a dietary supplement and is not intended for human consumption or therapeutic self-administration outside of approved clinical trial protocols. All RCDbio research compounds are supplied strictly for laboratory and research purposes only.

Chemical Properties

Property	Detail
Product Type	Synthetic Triple Receptor Agonist Peptide (GLP-1R / GIPR / GCGR)
Product Name	Retatrutide
Application	Scientific / Research Use Only
CAS Number	2381089-83-2
Molar Mass	~4,731 g/mol (free base); salt forms vary
Chemical Formula	C221H342N46O68 (free base)
Amino Acid Count	39 amino acids (GIP-backbone derived, C-terminal amide)
Non-Coded Residues	Aib at positions 2 and 20; α-Me-Leu at position 13
Lipid Conjugate	C20 fatty diacid via γ-Glu-AEEA linker at Lys17 (albumin-binding moiety)
Receptor Targets	GLP-1R (EC50: 0.775 nM); GIPR (EC50: 0.0643 nM); GCGR (EC50: 5.79 nM)
Synonyms	LY3437943; LY-3437943; Retaglutide
Physical Form	Lyophilized white to off-white powder
Solubility	Soluble in sterile water and dilute acetic acid; PBS compatible
Storage (Lyophilized)	−20°C; sealed container; protected from light and moisture
Storage (Reconstituted)	4°C; use within 48–72 hours; avoid repeated freeze-thaw cycles
PubChem CID	Not yet assigned as of June 2026; ChEMBL: ChEMBL5095485; UNII: NOP2Y096GV
Purity	≥98% (HPLC verified, independent third-party laboratory analysis; COA available per batch)
WADA Status	Prohibited under S0 (Non-Approved Substances) and S2 (Peptide Hormones, Growth Factors and Related Substances) of the 2026 WADA Prohibited List. Researchers in sport-adjacent studies must verify the current status at GlobalDRO.com before use.

How Does Retatrutide Work?

Retatrutide’s pharmacological profile is defined by its simultaneous engagement of three G protein-coupled receptor systems, each mediating distinct but complementary metabolic signalling cascades. The compound’s triple agonism is considered structurally enabled by the GIP-backbone sequence combined with the fatty acid conjugation that extends tissue exposure time.

GLP-1 Receptor (GLP-1R) Pathway

Retatrutide binds GLP-1R with an EC50 of 0.775 nM in human receptor assay systems. GLP-1R activation initiates Gαs-coupled signalling leading to elevated intracellular cyclic AMP (cAMP) levels and subsequent protein kinase A (PKA) activation in pancreatic beta cells, stimulating glucose-dependent insulin secretion. In isolated cell and preclinical rodent models, GLP-1R engagement is associated with delayed gastric emptying, reduced food intake signalling through hypothalamic appetite-regulatory circuits, and modulation of hepatic glucose output. These observations are consistent across multiple GLP-1R agonist class members and are well-characterised in peer-reviewed literature [Jastreboff et al., 2023].

GIP Receptor (GIPR) Pathway

Retatrutide exhibits its highest potency at GIPR (EC50: 0.0643 nM in human receptor systems), representing approximately 8.9-fold greater potency than the endogenous GIP hormone at this receptor. GIPR activation is associated with enhanced insulin secretion in a glucose-dependent manner, and in preclinical models has been linked to complementary effects on adipose tissue lipid metabolism and energy partitioning alongside GLP-1R co-activation. The additive or synergistic interaction between GIPR and GLP-1R agonism has been characterised as a driver of the enhanced weight loss observed with dual and triple agonist compounds compared to GLP-1R monotherapy in preclinical and clinical models [Jastreboff et al., 2023].

Glucagon Receptor (GCGR) Pathway

Retatrutide’s engagement of GCGR (EC50: 5.79 nM) distinguishes it mechanistically from dual GLP-1R/GIPR agonists, including tirzepatide. In preclinical rodent models, GCGR agonism is associated with increased hepatic glucose production and, at the whole-body level, with elevated energy expenditure through thermogenic and lipolytic mechanisms. In the context of triple agonism, GCGR-mediated energy expenditure enhancement has been proposed as the mechanistic basis for the superior weight loss observed with Retatrutide versus tirzepatide in head-to-head preclinical model comparisons, where Retatrutide induced greater adipose tissue reduction by increasing total energy expenditure rather than reducing intake alone [Sanyal et al., 2024].

Albumin Binding and Extended Half-Life

The C20 fatty diacid moiety at Lys17 non-covalently binds circulating albumin, dramatically reducing renal filtration and extending Retatrutide’s effective half-life to approximately 6 days in clinical pharmacokinetic studies, enabling once-weekly subcutaneous dosing in clinical trial protocols.

Key Research Findings

In preclinical, in vitro, and clinical research contexts, Retatrutide has been associated with the following observations:

• Triple receptor engagement: Simultaneous GLP-1R, GIPR, and GCGR agonism characterised by cryo-EM structural studies; receptor binding confirmed with EC50 values of 0.775, 0.0643, and 5.79 nM, respectively, at human receptors.
• Phase 2 weight reduction: In the Phase 2 obesity trial (NEJM, 2023), participants receiving 12 mg weekly Retatrutide demonstrated a mean weight reduction of 17.5% at 24 weeks and 24.2% at 48 weeks – the largest recorded for any incretin-class agent in a randomised controlled trial at the time of publication [Jastreboff et al., 2023].
• Liver fat reduction: In a Phase 2 MASLD substudy, Retatrutide 8 mg and 12 mg weekly were associated with 81.4% and 82.4% mean relative reductions in liver fat at 24 weeks in participants with baseline liver fat ≥10% [Sanyal et al., 2024].
• Glycaemic control: Phase 2 data in type 2 diabetes demonstrated dose-dependent HbA1c reductions alongside significant weight loss, with a safety profile comparable to approved GLP-1R agonists [Rosenstock et al., 2023].
• Energy expenditure mechanism: In preclinical rodent models, superior adipose tissue reduction compared to tirzepatide was attributed to GCGR-mediated increased energy expenditure rather than intake reduction alone.

All findings listed above are derived from preclinical, in vitro, and clinical trial data. Retatrutide is not approved by the FDA for any indication. These observations do not constitute evidence of safety or efficacy for any non-approved use. Phase 3 trials are ongoing, and findings may change.

What are the Potential Research Applications of Retatrutide?

In controlled laboratory and clinical research environments, Retatrutide has been investigated for the following research applications. These observations are from preclinical and clinical trial contexts and do not constitute claims of efficacy or safety outside approved trial protocols.

Triple Receptor Agonism Pharmacology Studies. Retatrutide serves as the primary research tool for characterising simultaneous GLP-1R, GIPR, and GCGR engagement in cell-based assay systems. It is employed in receptor binding assays, cAMP pathway reporter systems, and cryo-EM structural studies to investigate the molecular basis of triple agonism and ligand-induced receptor conformational changes.

Obesity and Energy Expenditure Pathway Research. In preclinical rodent models and human Phase 2 clinical trials, Retatrutide is investigated for its coordinated effects on body weight reduction, adipose tissue metabolism, and total energy expenditure. Research focuses on the respective contributions of GLP-1R, GIPR, and GCGR pathways to observed weight loss, with particular interest in the GCGR-mediated thermogenic component that differentiates it from dual agonists.

Metabolic Dysfunction-Associated Liver Disease Models. Retatrutide is investigated for its effects on hepatic fat content, liver enzyme normalisation, and steatohepatitis markers in preclinical fatty liver models and the Phase 2a MASLD substudy. Research examines GCGR-mediated hepatic fat oxidation alongside incretin-mediated insulin sensitisation as complementary liver-protective mechanisms.

Type 2 Diabetes and Glycaemic Control Research. In Phase 2 clinical trials and cell-based assay systems, Retatrutide is investigated for glucose-dependent insulin secretion modulation, HbA1c pathway interactions, and insulin sensitivity improvements. Research examines the relative contributions of each receptor pathway to glycaemic outcomes in isolation and combination.

Comparative Incretin Pharmacology. Retatrutide is employed as a triple agonist reference compound in comparative studies against GLP-1R monotherapy (semaglutide) and dual GLP-1R/GIPR agonism (tirzepatide) to characterise how additional receptor engagement alters metabolic outcomes, receptor cross-talk, and downstream signalling profiles in experimental systems.

What are the Potential Side Effects of Retatrutide?

The following observations are derived from Phase 2 clinical trial data and preclinical models. Long-term safety data for Retatrutide remain under investigation in ongoing Phase 3 trials, and no regulatory approval has been granted.

• Gastrointestinal adverse events – nausea, vomiting, diarrhoea, and constipation – were the most frequently reported adverse events in Phase 2 trials; dose-dependent in frequency and predominantly mild-to-moderate in severity; consistent with GLP-1R agonist class effects
• Hypersensitivity reactions were reported at low frequency in Phase 2 clinical trial populations; injection site reactions were noted at low incidence with subcutaneous administration
• Transient heart rate increases observed in Phase 2 clinical data, consistent with GLP-1R agonist class pharmacology; mechanism not fully characterised for the triple agonist combination
• Theoretical cardiovascular risk from GCGR agonism has been proposed based on glucagon’s known effects on cardiac function; no adverse cardiovascular signals were observed in the Phase 2 trial populations, but long-term cardiac safety data are not yet available
• Pancreatitis risk cannot be excluded; GLP-1R agonist class members have been associated with pancreatitis reports; participants with a clinically significant pancreatitis history were excluded from Phase 2 trials
• Renal pharmacokinetic variability noted; participants with severe renal impairment were excluded from Phase 2 trials; pharmacokinetic data in this population are limited.

No long-term human safety data has been established for Retatrutide. Phase 3 trial safety data are pending. These observations should not be extrapolated beyond the clinical trial contexts in which they were recorded.

Risk & Handling

Handling Precautions

Retatrutide should only be handled by trained laboratory personnel with experience in research-grade peptide compounds and investigational pharmacological agents. Appropriate personal protective equipment is required: nitrile gloves, a laboratory coat, and eye protection at a minimum. When working with lyophilized powder, use within a laminar flow cabinet or clean area to avoid inhalation. Avoid aerosol generation during reconstitution. The fatty acid conjugate component increases the compound’s amphiphilic character; avoid prolonged contact with surfaces that may adsorb lipophilic molecules.

Exposure Risks

Risk Tier: MODERATE

Retatrutide is a potent triple receptor agonist with well-characterised pharmacological activity at GLP-1R, GIPR, and GCGR. Accidental exposure at research-relevant concentrations may engage these receptors in tissues expressing them, including pancreatic beta cells, gastrointestinal smooth muscle, hypothalamic appetite circuits, and hepatic cells. Gastrointestinal effects, including nausea and altered motility, are the primary expected acute effects consistent with GLP-1R agonist class pharmacology. Long-term safety data from completed trials are not yet available. No human safety data has been established for research-grade Retatrutide outside approved clinical trial protocols.

Storage

• Lyophilized form: Store at −20°C in original sealed, light-protected container with desiccant
• Reconstituted form: Store at 4°C; use within 48–72 hours of reconstitution
• Do not subject to repeated freeze-thaw cycles; peptide and fatty acid conjugate integrity may both be affected
• Protect from prolonged light and heat exposure; the C20 fatty diacid conjugate may degrade under oxidative conditions
• Store away from strong acids, bases, and oxidising agents

Frequently Asked Questions

Q: What is Retatrutide, and what is it investigated for in research? 

A: Retatrutide (LY3437943) is a synthetic 39-amino-acid peptide that simultaneously agonises three G protein-coupled receptors – GLP-1R, GIPR, and GCGR – making it the first triple receptor agonist in its class to reach Phase 3 clinical development. It is investigated in preclinical and clinical research contexts for obesity pathway pharmacology, metabolic signalling, hepatic fat reduction, and type 2 diabetes glycaemic control. It is not approved by the FDA and is intended for research purposes only.

Q: How does Retatrutide differ from tirzepatide? 

A: Tirzepatide is a dual GLP-1R/GIPR agonist. Retatrutide adds glucagon receptor (GCGR) agonism as a third mechanism. In preclinical models, GCGR activation is associated with increased energy expenditure through thermogenic and lipolytic pathways – an effect not produced by GLP-1R or GIPR engagement alone. This mechanistic difference is proposed as the basis for Retatrutide’s superior weight loss versus tirzepatide in head-to-head preclinical comparisons and Phase 2 data.

Q: Is Retatrutide approved by the FDA? 

A: No. As of June 2026, Retatrutide is not approved by the FDA for any indication. It is an investigational compound in Phase 3 clinical development under the TRIUMPH (obesity), TRANSCEND (type 2 diabetes), and REDEFINE (MASLD) programmes. Phase 3 primary endpoint data are anticipated in 2026–2027.

Q: What is the half-life of Retatrutide? 

A: In Phase 2 clinical pharmacokinetic studies, Retatrutide demonstrated an approximate half-life of 6 days following subcutaneous administration, enabling once-weekly dosing. This extended half-life is achieved through the C20 fatty diacid moiety at Lys17, which promotes non-covalent albumin binding and reduces renal clearance. These figures are derived from clinical trial data and apply to the pharmaceutical formulation used in trials, not to research-grade material.

Q: What were the key findings from the Phase 2 obesity trial? 

A: In the Phase 2 double-blind, randomised, placebo-controlled trial (Jastreboff et al., 2023, NEJM), participants receiving the 12 mg weekly dose demonstrated mean weight reductions of 17.5% at 24 weeks and 24.2% at 48 weeks – the largest weight loss recorded for any incretin-class agent in a randomised controlled trial at that time. Gastrointestinal adverse events were the most common finding and were dose-dependent. These data are from a Phase 2 trial and do not constitute final approval-enabling safety or efficacy data.

Q: How should research-grade Retatrutide be stored? 

A: Lyophilized Retatrutide should be stored at −20°C in a sealed, light-protected container with desiccant. Once reconstituted, solutions should be stored at 4°C and used within 48–72 hours. Repeated freeze-thaw cycles must be avoided as they may degrade the peptide backbone and disrupt the fatty acid conjugate. Protect from oxidative conditions.

Q: What is Retatrutide’s WADA status? 

A: Retatrutide is prohibited under the 2026 WADA Prohibited List under S0 (Non-Approved Substances – any pharmacologically active substance not approved for human therapeutic use) and S2 (Peptide Hormones, Growth Factors, and Related Substances, which includes GLP-1 receptor agonists). Researchers in sport-adjacent studies must verify the current status at GlobalDRO.com before use.

Related Research Compounds

Researchers investigating Retatrutide may also be interested in the following compounds currently available for laboratory research at RCDbio:

• Tirzepatide – A dual GLP-1R/GIPR agonist peptide (Eli Lilly’s Mounjaro/Zepbound active ingredient) investigated in preclinical and clinical models; the primary mechanistic comparator for Retatrutide research, lacking the GCGR component.
• Semaglutide – A GLP-1R monoagonist investigated in preclinical metabolic models; the foundational reference compound for incretin-class receptor pharmacology research.

All products listed are for laboratory and research purposes only.

References

1. Jastreboff, A. M., Kaplan, L. M., Frías, J. P., Wu, Q., Du, Y., Gurbuz, S., Coskun, T., Haupt, A., Milicevic, Z., & Hartman, M. L. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity – A Phase 2 Trial. New England Journal of Medicine, 389(6), 514–526. https://pubmed.ncbi.nlm.nih.gov/37366315/
2. Sanyal, A. J., Kaplan, L. M., Frias, J. P., Brouwers, B., Wu, Q., Thomas, M. K., Harris, C., Schloot, N. C., Du, Y., Mather, K. J., Haupt, A., & Hartman, M. L. (2024). Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nature Medicine, 30(8), 2037–2048. https://pubmed.ncbi.nlm.nih.gov/38886561/
3. Coskun, T., Urva, S., Roell, W. C., Qu, H., Loghin, C., Moyers, J. S., O’Farrell, L. S., Briere, D. A., Sloop, K. W., Thomas, M. K., Haupt, A., Benson, C. T., & Milicevic, Z. (2022). 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, 34(9), 1234–1247. https://pubmed.ncbi.nlm.nih.gov/35985343/
4. Rosenstock, J., Frias, J., Jastreboff, A. M., Du, Y., Lou, J., Gurbuz, S., Thomas, M. K., Hartman, M. L., Haupt, A., Milicevic, Z., & Coskun, T. (2023). 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. The Lancet, 402(10401), 529–544. https://pubmed.ncbi.nlm.nih.gov/37385278/

Disclaimer

Retatrutide is exclusively for laboratory research purposes. RCDbio products are not intended to diagnose, prevent, treat, or cure any disease or medical condition.

The Food and Drug Administration has not approved Retatrutide for any indication. This product is not approved for human or veterinary use. Researchers must comply with all applicable local, state, and federal laws and regulations governing the purchase and use of research compounds. By purchasing, you agree to our Terms and Conditions. RCDbio reserves the right to refuse sales to unauthorized individuals.

ATTENTION: All RCDbio products are strictly for LABORATORY AND RESEARCH PURPOSES ONLY. They are not intended for human consumption, veterinary use, or any other non-research application. For queries, complaints, or support, contact support@rcdbio.co