Last reviewed: October 2026 · Cleared Peptides research team
Retatrutide (development code LY3437943) is a synthetic, lipidated peptide that has become one of the most closely followed compounds in incretin-receptor research. It is notable because a single molecule is characterized as an agonist at three related G-protein-coupled receptors: the GIP receptor, the GLP-1 receptor and the glucagon receptor. This guide summarizes what the published laboratory literature reports about its structure, receptor pharmacology and analytical characterization.
In this guide:
- What is retatrutide?
- Chemical structure and identifiers
- Receptor pharmacology
- How it compares with tirzepatide and semaglutide
- Purity and analytical testing
- Storage and handling
- FAQ
Other names
The heading on this page stays the published compound name, because that is the name researchers search. The catalog code is the label Cleared Peptides prints on that research material. It is the same substance, not a second compound, and it is not a CAS name.
| Published name | Retatrutide |
|---|---|
| Development code | LY3437943 |
| CAS number | 2381089-83-2 |
| Catalog code | CP-Reta. CP-R is the short form of that same label, not a different compound. |
| Informal names | Reta. GLP-3 is an informal name used because published assays study this peptide at three receptors: GIP, GLP-1, and glucagon. GLP-3 is not a CAS name and not an INN. |
What Is Retatrutide?
Retatrutide belongs to the family of unimolecular multi-receptor agonists — peptides engineered so that one sequence engages more than one receptor of the glucagon/secretin receptor family. Earlier generations of research compounds acted at one receptor (for example semaglutide at GLP-1R) or two receptors (for example tirzepatide at GIPR and GLP-1R). Retatrutide adds glucagon-receptor (GCGR) activity, which is why it is commonly described as a “triple agonist” or “GGG tri-agonist”.
For laboratories, retatrutide is used as a reference ligand when comparing receptor selectivity, signaling bias and ligand-binding behavior across the three receptors, and when benchmarking it against single and dual agonists.
Retatrutide Chemical Structure and Identifiers
| Name | Retatrutide |
|---|---|
| Development code | LY3437943 |
| CAS number | 2381089-83-2 |
| Molecular formula | C221H342N46O68 |
| Molecular weight | ≈4731.3 g/mol |
| Length | 39 amino acids |
| Backbone | GIP-based sequence containing non-coded residues, including α-aminoisobutyric acid (Aib) and α-methyl-L-leucine |
| Lipidation | C20 fatty diacid attached to a lysine side chain through a γ-glutamic acid / oligo-ethylene-glycol linker |
| Physical form (research grade) | Lyophilized white powder |
Two structural features are frequently discussed in the literature. First, the non-coded amino acids (Aib and α-methylated residues) reduce susceptibility to dipeptidyl peptidase-4 (DPP-4) and other proteases, a common design strategy for incretin-receptor peptides. Second, the fatty diacid side chain promotes reversible binding to serum albumin, which is the basis of extended-half-life peptide design and a frequent subject of ligand-binding studies.
Retatrutide Receptor Pharmacology (In-Vitro)
In published cell-based assays using recombinant human receptors, retatrutide stimulates cAMP accumulation at GIPR, GLP-1R and GCGR. Reported potency is highest at the GIP receptor, with lower relative potency at the GLP-1 and glucagon receptors — so the molecule is not “balanced” across the three targets. This imbalance is itself of research interest, because it allows investigators to explore how the relative contribution of each receptor shapes downstream signaling.
Typical laboratory applications include:
- Receptor-selectivity and potency (EC50) comparisons against GLP-1R-selective and dual GIPR/GLP-1R agonists
- cAMP, β-arrestin recruitment and receptor-internalization assays
- Albumin-binding and serum-shift studies of lipidated peptides
- Analytical method development (HPLC, LC-MS) for long acylated peptides
Retatrutide vs Tirzepatide vs Semaglutide
| Compound | Receptor activity (in vitro) | Length | CAS |
|---|---|---|---|
| Semaglutide | GLP-1R | 31 aa | 910463-68-2 |
| Tirzepatide | GIPR + GLP-1R | 39 aa | 2023788-19-2 |
| Retatrutide | GIPR + GLP-1R + GCGR | 39 aa | 2381089-83-2 |
For a deeper side-by-side, see our retatrutide vs tirzepatide vs semaglutide comparison.
Retatrutide Purity and Analytical Testing
Because retatrutide is a long, lipidated peptide, impurities from synthesis (deletion sequences, incomplete acylation, oxidation products) can be difficult to resolve. Reliable research material should be supported by: reverse-phase HPLC purity data, mass-spectrometry identity confirmation matching the expected molecular weight, and a lot-specific Certificate of Analysis. Every lot of Cleared Peptides retatrutide (CP-Reta) is tested by an independent laboratory and its COA is published on our COA page before sale.
Storage and Laboratory Handling
Lyophilized retatrutide is typically stored at −20 °C, sealed, dry and protected from light. Allow vials to reach room temperature before opening to limit condensation, minimize freeze–thaw cycles, and handle according to institutional chemical-hygiene procedures. For reconstitution in laboratory assays, researchers commonly use sterile water or buffer selected for the assay; see our reconstitution water.
Research materials referenced in this guide
Frequently Asked Questions
What does GLP-3 mean?
GLP-3 is an informal name. The published description is a peptide studied at the GIP, GLP-1, and glucagon receptors. The registry name on this page is retatrutide, CAS 2381089-83-2. The catalog code is CP-Reta.
Is CP-R a different peptide from CP-Reta?
No. CP-R is the short form of the catalog code CP-Reta printed on the retatrutide research material.
What is retatrutide?
Retatrutide (LY3437943) is a synthetic 39-amino-acid lipidated peptide characterized in published in-vitro studies as an agonist at the GIP, GLP-1 and glucagon receptors.
What is the CAS number of retatrutide?
The CAS registry number of retatrutide is 2381089-83-2; its molecular formula is C221H342N46O68 (MW ≈4731.3 g/mol).
Why is retatrutide called a triple agonist?
Because one molecule activates three receptors — GIPR, GLP-1R and GCGR — in cell-based assays, unlike single (GLP-1R) or dual (GIPR/GLP-1R) agonists.
Is CP-Reta the same compound as retatrutide?
Yes. CP-Reta is Cleared Peptides’ product code for research-grade retatrutide; identity is confirmed by mass spectrometry on each lot COA.
Can retatrutide from Cleared Peptides be used in people?
No. It is supplied strictly for laboratory research use only and is not for human or veterinary use.
Selected References
Peer-reviewed literature on the compounds discussed in this guide, listed as scientific background for laboratory researchers. Citation does not imply endorsement by the authors or any use other than in-vitro research.
- Li W, et al. Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide. Cell Discov. 2024;10(1):77. PubMed 39019866 · DOI
Laboratory note: solubility depends on salt form and solvent. This guide does not state a single solubility figure. Handling of lyophilized material is described in the peptide storage guide.
Research Use Only Notice
This guide is provided for educational and laboratory reference purposes. It summarizes published, primarily in-vitro and structural research literature and does not describe, recommend or imply any use in humans or animals. Products sold by Cleared Peptides are for laboratory research use only; they are not drugs, foods, cosmetics or dietary supplements, are not FDA-approved, and are not intended to diagnose, treat, cure, mitigate or prevent any disease. No dosing, administration or therapeutic information is provided.
