Retatrutide (LY3437943): Research Reference
Research Use Only. This page is a technical reference for in-vitro laboratory research. Reserve Research compounds are not for human or veterinary use, and nothing here is guidance for administration of any kind.
In simple words
Retatrutide is a chain of 39 amino acids. It is made in a lab. Amino acids are the building blocks of proteins. It has a fatty tail too. The tail helps it last longer.
Cells have switches on the outside. Retatrutide can turn on three kinds of switches. Their names are glucagon, GIP and GLP-1. That is why it is called a triple agonist. Scientists use it in the lab to see how the three switches work together.
Reserve Research sells retatrutide only for lab research. See Retatrutide on our product page →
Retatrutide (development code LY3437943) is a synthetic, lipidated 39-amino-acid peptide that activates three class B G-protein-coupled receptors: the glucagon receptor (GCGR), the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R). That makes it a “triple agonist”. It was developed by Eli Lilly and Company on a GIP-based backbone that carries non-coded amino acids and a C20 fatty diacid. Its CAS number is 2381089-83-2, its formula is C221H342N46O68, and its molecular weight is about 4,731.3 g/mol.
Retatrutide key facts
| Name | Retatrutide |
|---|---|
| Development code | LY3437943 |
| Compound class | Synthetic lipidated peptide; triple GCGR / GIPR / GLP-1R agonist |
| Length | 39 amino acids |
| Modifications | Non-coded amino acids (α-aminoisobutyric acid and α-methyl-L-leucine) for protease resistance; C20 fatty diacid conjugated to a lysine side chain |
| CAS number | 2381089-83-2 |
| Molecular formula | C221H342N46O68 |
| Molecular weight | ≈4,731.3 g/mol |
| Receptor targets | GCGR, GIPR and GLP-1R (class B GPCRs, Gs/cAMP coupled) |
| Reported in-vitro potency | EC50 ≈ 0.064 nM (human GIPR), ≈ 0.78 nM (human GLP-1R), ≈ 5.8 nM (human GCGR) (vendor-reported cAMP assay data) |
| Appearance | White to off-white lyophilized powder |
| Storage (lyophilized) | −20 °C, dry, protected from light |
Structure
Retatrutide is a single 39-residue peptide, not a mixture or a fusion of separate hormones. Like tirzepatide, its sequence is based on GIP, and it is engineered so one molecule can engage three related receptors. The key structural features are:
- Non-coded amino acids. α-Aminoisobutyric acid (Aib) and α-methyl-L-leucine stabilize the helix and protect the N-terminus from DPP-4 cleavage.
- C20 fatty diacid. A lipid chain attached to a lysine side chain through a linker binds serum albumin, which prolongs the peptide’s persistence in experimental systems.
- Tuned receptor balance. Substitutions across the sequence adjust relative activity at GCGR, GIPR and GLP-1R.
Mechanism studied in research models
All three target receptors are class B GPCRs that signal mainly through Gs and raise intracellular cAMP. In the discovery work, retatrutide was more potent than native GIP at the human GIP receptor, and less potent than native glucagon and native GLP-1 at their receptors (Coskun et al., 2022). The glucagon-receptor component is what separates it from dual GIPR/GLP-1R agonists. It makes retatrutide a research tool for studying how glucagon-receptor signaling combines with incretin-receptor signaling in cell and tissue models.
Retatrutide vs. tirzepatide
| Retatrutide | Tirzepatide | |
|---|---|---|
| Code | LY3437943 | LY3298176 |
| Receptors | GCGR + GIPR + GLP-1R (triple) | GIPR + GLP-1R (dual) |
| Length | 39 aa | 39 aa |
| Formula | C221H342N46O68 | C225H348N48O68 |
| Molecular weight | ≈4,731.3 g/mol | ≈4,813.5 g/mol |
| CAS | 2381089-83-2 | 2023788-19-2 |
Laboratory handling and storage
- Lyophilized powder: store at −20 °C, sealed and dry, away from light. Let the vial reach room temperature before opening.
- Solvent: labs commonly reconstitute in sterile bacteriostatic water for multi-use stock solutions. Vendor data show aqueous solubility rising at mildly basic pH.
- Prepared solutions: keep at 2–8 °C, avoid vigorous shaking, and avoid repeated freeze–thaw cycles. Low-binding tubes reduce losses of lipidated peptide to plastic.
What a retatrutide certificate of analysis should show
- Identity: mass spectrometry consistent with ≈4,731.3 g/mol for the intact lipidated peptide.
- Purity: chromatographic purity reported for the specific batch.
- Batch traceability: a lot number that matches the vial label.
Every Reserve Research batch is tested by an independent lab. You can look up any batch number on our COA verification page.
Frequently asked questions
What is retatrutide?
Retatrutide (LY3437943) is a synthetic 39-amino-acid lipidated peptide that activates the glucagon, GIP and GLP-1 receptors. Laboratories use it to study triple-receptor signaling.
What is the CAS number for retatrutide?
2381089-83-2.
What is the molecular weight and formula of retatrutide?
C221H342N46O68, with a molecular weight of about 4,731.3 g/mol.
Why is retatrutide called a triple agonist?
One peptide activates three different receptors: the glucagon receptor (GCGR), the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R).
What is the difference between retatrutide and tirzepatide?
Both are lipidated 39-amino-acid peptides from Eli Lilly built on a GIP-based backbone. Tirzepatide activates GIPR and GLP-1R. Retatrutide also activates the glucagon receptor.
Is retatrutide a peptide?
Yes. It is a 39-amino-acid peptide that includes non-coded amino acids and a fatty-acid side chain.
How should retatrutide be stored?
Store the lyophilized powder at −20 °C, dry and protected from light. Keep reconstituted solutions at 2–8 °C and avoid repeated freeze–thaw cycles.
Is Reserve Research retatrutide sold for laboratory research only?
Yes. It is sold strictly for in-vitro laboratory research. It is not a drug or supplement, and it is not for human or veterinary use.
Research-grade retatrutide from Reserve Research
Retatrutide is supplied as a lyophilized powder in sealed vials, independently tested batch by batch, with the COA available through the product page and /verify. Related: tirzepatide reference, cagrilintide reference and bacteriostatic water.
References
- Coskun T, Urva S, Roell WC, et al. Cell Metabolism. 2022;34(9):1234–1247.e9. doi:10.1016/j.cmet.2022.07.013
- Coskun T, Sloop KW, Loghin C, et al. Molecular Metabolism. 2018;18:3–14. doi:10.1016/j.molmet.2018.09.009 (tirzepatide, for comparison)
- MedChemExpress retatrutide (HY-P3506) technical data: CAS, formula, molecular weight and receptor EC50 values.
Last reviewed: October 2026. This page summarizes published laboratory literature for reference. It makes no claims about the safety or effectiveness of any compound in humans or animals.