What is Retatrutide?
Retatrutide in one paragraph
Retatrutide (LY3437943) is a synthetic peptide of 39 amino acids developed by Eli Lilly. It is a triple agonist: one peptide chain that binds three receptors, GIP, GLP-1 and glucagon, which is why the market also calls it "GLP-3". The chain is built on the GIP sequence and carries three non-coded amino acids, a C20 fatty diacid joined to a lysine side chain through a linker, and a C-terminal amide. This guide sets out its structure and the sources behind each fact. It makes no claims about use in people.
Where to find the sequence
Retatrutide is a chain of 39 amino acids built on the human GIP sequence. The residue-by-residue listing, in one-letter and three-letter code, is held on the NCATS GSRS record (UNII NOP2Y096GV, the parent substance) and on the supplier datasheet MedChemExpress HY-P3506. We point to those records rather than retype a 39-letter string here, so that the sequence you read is the one the registry holds.
| Feature | Retatrutide |
|---|---|
| Developer code | LY3437943 |
| Length | 39 amino acids |
| Built on | Human GIP |
| C-terminus | Amide |
| Non-coded residues | 3 (two Aib, one α-methyl-leucine) |
Non-coded amino acids: Aib and α-methyl-leucine
"Non-coded" means an amino acid that the genetic code does not specify. Retatrutide has two α-aminoisobutyric acid residues (Aib) and one α-methyl-leucine. Tirzepatide and Semaglutide also carry Aib; our comparison of the three sets them side by side.
The fatty diacid side chain and linker
A C20 fatty diacid is joined to a lysine side chain through a linker. The diacid and linker are why the molecule is larger than its 39-residue chain alone would be, and they are part of the formula below.
Formula, molar mass, CAS number
| Property | Value |
|---|---|
| Molecular formula | C221H342N46O68 |
| Molar mass | about 4,731 g/mol |
| CAS number | 2381089-83-2 |
Three receptors: GIP, GLP-1 and glucagon
Retatrutide binds three receptors: the GIP receptor, the GLP-1 receptor and the glucagon receptor. A peptide that binds one receptor is a single agonist, two a dual agonist and three a triple agonist. Retatrutide is the triple agonist among the compounds we list; Tirzepatide binds two and Semaglutide binds one. All three are compared on our GLP-1 research peptides page.
Research history: LY3437943 from discovery to the TRIUMPH phase 3 programme
Retatrutide was developed by Eli Lilly under the code LY3437943. It was described by Coskun and colleagues in Cell Metabolism in 2022 (doi:10.1016/j.cmet.2022.07.013). The TRIUMPH phase 3 programme is registered on ClinicalTrials.gov. This guide names the programme and quotes no outcome figures from it: for those, read the registrations and the published papers themselves.
Structural studies (cryo-EM, 2024)
A 2024 paper by Li and colleagues in Cell Discovery (PMC11255275) reports cryo-electron microscopy structures. It is the place to look for how the peptide sits against its receptor.
How it is supplied: pens and powder
Our Retatrutide comes as Retatrutide 40mg in a pre-filled 3 ml pen: 13.3 mg/ml by the label, 99% purity, with 4 pen needle tips in the box. The peptide is already in solution, so there is no powder to measure out. Store at 2–8°C and refrigerate on arrival. Some UK shops sell GLP-1 compounds as vials of lyophilised powder; see peptide pen vs vial for the difference.
Our lab report
An R3vive Retatrutide pen was tested blind by Janoshik Analytical (report #230680): HPLC purity 99.334%. The full report is on our lab reports page.
Sources
- NCATS GSRS, UNII NOP2Y096GV (parent).
- Coskun et al., Cell Metabolism, 2022, doi:10.1016/j.cmet.2022.07.013.
- Li et al., Cell Discovery, 2024, PMC11255275.
- MedChemExpress datasheet HY-P3506.
- ClinicalTrials.gov: the TRIUMPH registrations.
- Janoshik Analytical report #230680.
Products in this guide
All products are supplied for research purposes only.