Retatrutide 10 mg --- Research Product Overview

**Disclaimer:** This article is provided for educational and research purposes only. [Retatrutide](/catalog/retatrutide-10) research material sold by Viking Labs is intended for laboratory research use only. It is not approved by the FDA or any other regulatory authority for human therapeutic use, and nothing in this article constitutes medical advice or a recommendation for self-administration.

Overview

Retatrutide (LY3437943) is an investigational triple agonist peptide developed by Eli Lilly that activates three incretin- and energy-balance-related receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR). It is the most clinically advanced "tri-agonist" in this class and represents a deliberate effort to combine the appetite- and insulin-related effects of GLP-1/GIP coactivation with the energy-expenditure effects of glucagon receptor agonism. Readers new to the underlying receptor class should start with our GLP-1 peptide revolution primer.

The Viking Labs 10 mg vial is a lyophilized presentation intended for laboratory reconstitution and is suited to in vitro receptor pharmacology, rodent dosing studies, and comparative pharmacology experiments where moderate working stocks are required.

Sequence and Structural Notes

Retatrutide is a 39-amino acid synthetic peptide based on a glucagon/GLP-1 chimeric backbone with an Aib substitution at position 2 (DPP-4 resistance) and a C20 fatty diacid moiety attached via a gamma-Glu/AEEA-AEEA linker for albumin binding and extended half-life. The molecular weight is approximately 4731 Da. The peptide is engineered with balanced potency at GLP-1R, GIPR, and GCGR, with reported in vitro receptor activity ratios biased modestly in favor of GIPR and GCGR relative to native ligands.

Coskun et al. (2022) described the discovery and structural rationale for retatrutide, including the iterative tuning of receptor selectivity through specific residue substitutions in the central and C-terminal regions.

Mechanism of Action

GLP-1R activation drives glucose-dependent insulin secretion, glucagon suppression, slowed gastric emptying, and central appetite reduction. GIPR activation modulates insulin secretion in synergy with GLP-1R and influences adipocyte function. GCGR activation, classically associated with hepatic glucose production, also stimulates energy expenditure, lipolysis, and hepatic fatty acid oxidation. The combined receptor profile is hypothesized to produce greater effects on body weight and metabolic parameters than mono- or dual-agonist peptides, while GLP-1R-driven insulin sensitization compensates for glucagon's hyperglycemic potential. For a focused mechanistic write-up, see our retatrutide triple agonist explainer.

Comparator Peptides --- Retatrutide vs. Tirzepatide vs. Semaglutide

Retatrutide sits at the apex of the current generation of long-acting incretin research peptides; comparing its receptor and efficacy profile to its predecessors clarifies what each additional receptor "buys" in preclinical models. Our deep-dive retatrutide vs. semaglutide vs. tirzepatide analysis covers this in detail.

Receptor breadth. Semaglutide is a GLP-1R mono-agonist (see what is semaglutide). Tirzepatide is a GLP-1R/GIPR dual agonist with reported balanced potency that engages incretin co-signaling at the somatotroph and adipocyte (see tirzepatide dual agonist overview). Retatrutide adds GCGR engagement, which differentiates it pharmacologically by recruiting hepatic and adipose lipid-oxidation pathways under glucagon control --- producing energy-expenditure effects that neither mono- nor dual-incretin agonists achieve alone.

In vitro potency. Coskun et al. (2022) reported retatrutide EC50 values in the low picomolar range at GLP-1R, low picomolar at GIPR, and single-digit picomolar at GCGR (cAMP accumulation in cells expressing recombinant human receptors). Tirzepatide is roughly equipotent at GLP-1R and GIPR but inactive at GCGR. Semaglutide is potent at GLP-1R only.

Preclinical efficacy on body weight and lipid handling. In matched DIO mouse studies, retatrutide produces 22-25% body-weight reduction over 28 days at the high dose, compared to roughly 15% for tirzepatide and 8-12% for semaglutide. The retatrutide-specific contribution above tirzepatide tracks an increase in resting energy expenditure that is consistent with GCGR-driven hepatic and adipose lipid oxidation. Hepatic triglyceride content also drops more sharply on retatrutide than on the dual-agonist comparator, supporting use in NAFLD/NASH research models.

Deeper Preclinical Breakdown

Coskun et al. (2022) --- Discovery and characterization in Cell Metabolism. The paper described the discovery program that identified LY3437943 from a screen of glucagon/GLP-1 chimeric backbones. Methodology: in vitro receptor potency was measured via cAMP accumulation in HEK293 cells expressing each human receptor; in vivo efficacy was assessed in DIO mice (60% kcal high-fat diet for 16+ weeks) dosed subcutaneously every 3 days for 28 days at 0.1, 1, and 10 nmol/kg. Key results: at the high dose, retatrutide produced 22% body-weight reduction, 38% hepatic triglyceride reduction, and improved oral glucose tolerance test (OGTT) responses. Limitation: the dose-response was modeled in young adult mice; aged metabolic models were not characterized in this initial paper.

Jastreboff et al. (2023) --- Phase 2 trial (NEJM, PMID 37235529). While clinical, the phase 2 trial anchors the translational interpretation of preclinical retatrutide work. Methodology: 338 adults with obesity randomized to 1, 4, 8, or 12 mg weekly subcutaneous retatrutide or placebo for 48 weeks; primary endpoint was percent change in body weight. Key result: dose-dependent body-weight reduction reaching -24.2% at the 12 mg dose --- the largest mean reduction reported in the modern incretin trial program at the time of publication. Limitation: 48-week follow-up; durability and weight regain after discontinuation were not characterized in the primary report.

Rosenstock et al. (2023) --- Phase 2 in type 2 diabetes (Lancet). A parallel phase 2 trial in adults with T2D evaluated retatrutide's effects on HbA1c and body weight. Methodology: 281 adults with T2D randomized across multiple dose arms vs. dulaglutide and placebo. Key result: HbA1c reduction of -2.02% at the high dose vs. -1.41% for dulaglutide, with concurrent body-weight reduction of -16.9%. Limitation: comparator was dulaglutide rather than tirzepatide, leaving the dual-vs.-triple agonist head-to-head pending later studies.

Common Research Applications

• Receptor functional assays (cAMP, beta-arrestin) at human GLP-1R, GIPR, and GCGR
• Comparative pharmacology against semaglutide (mono) and tirzepatide (dual) in rodent obesity models
• Hepatic lipid handling studies in NAFLD/NASH models
• Indirect calorimetry studies of energy expenditure and substrate utilization
• Investigation of GCGR-driven hepatic fatty acid oxidation pathways
• Studies probing the mTOR pathway peptides interface with incretin signaling

Formulation Considerations

Lyophilized retatrutide is typically supplied as a white-to-off-white amorphous cake from acetate-buffered solution at pH 7.0-7.5. Recommended diluent for laboratory reconstitution is sterile bacteriostatic water at 1-5 mg/mL; sterile saline or PBS pH 7.0-7.4 is also acceptable for short-term solution work. As with semaglutide, the C20 lipid tail makes the peptide mildly surface-active and prone to foaming if vortexed --- gentle inversion is the preferred reconstitution protocol.

Reconstituted retatrutide in glass at 2-8 degrees C retains greater than 95% main-peak purity for 28-42 days under aseptic conditions. Working stocks below 100 microgram/mL benefit from low-binding tubes and optional 0.1% BSA carrier to reduce surface adsorption. Common COA impurities include des-amidation at internal Asn/Gln residues (typically less than 0.5% combined) and acylation-related synthesis byproducts visible as discrete peaks in the 0.1-1.0% RT range relative to the main retatrutide peak. Light-driven oxidation of the Trp residue is detectable after 7+ days at room temperature; amber vials and refrigerated storage mitigate this risk. For broader formulation context, see our peptide solubility guide.

Research-Context Dosing Ranges

In published preclinical literature, retatrutide doses in DIO mice have ranged from 0.1 to 10 nmol/kg subcutaneously administered every 3 days (Coskun et al., 2022). In Zucker diabetic fatty (ZDF) rats, comparable nmol/kg ranges with adjusted dose intervals have been reported. In cynomolgus monkey pharmacokinetic studies, doses of approximately 0.4-3 nmol/kg/week have been used. These dose ranges are provided strictly as references to the published rodent and non-human primate research literature and are not recommendations for human use; retatrutide research material sold by Viking Labs is for laboratory research only.

Handling, Reconstitution, and Storage

Lyophilized retatrutide should be stored at -20 degrees C and is typically stable for 24+ months when sealed. Reconstitute with sterile bacteriostatic water for laboratory use; the lipidated structure recommends gentle inversion rather than vortexing. Reconstituted solutions are typically stored at 2-8 degrees C and used within 28-42 days based on aseptic conditions and buffer. Like semaglutide, retatrutide is somewhat hydrophobic; carrier protein (e.g., 0.1% BSA) may be appropriate for very dilute working stocks to minimize surface losses. See our peptide storage and stability reference for further detail.

HPLC Purity and Lab Specifications

• HPLC purity: greater than or equal to 98.0% (RP-HPLC, 214 nm)
• Identity: ESI-MS or MALDI-TOF matching theoretical mass within 1 Da
• Counterion content (acetate/TFA) reported on COA
• Endotoxin: less than 5 EU/mg
• Water content: typically less than 5% by Karl Fischer titration

For interpretive guidance on third-party COA documents, see How to read a peptide COA.

Cross-References --- Related Viking Labs Research

For continued reading on retatrutide and the broader incretin research peptide class:

• Semaglutide GLP-1 research overview
• Retatrutide 20 mg vial
• Retatrutide vs. semaglutide vs. tirzepatide
• Tirzepatide dual agonist overview
• Understanding peptide purity
• WADA prohibited list 2026 --- regulatory context for incretin research

*Provided for laboratory research purposes only. Not for human or veterinary use.*