Retatrutide, also known by its development code LY3437943, is a synthetic peptide developed by Eli Lilly and Company. It belongs to a new generation of incretin-based molecules: a single peptide designed to act as an agonist at three receptors at the same time — the GIP receptor, the GLP-1 receptor and the glucagon receptor.
This article explains what the molecule is, how it is built, and where it stands in research. It does not give, and R3TA does not give, any advice on use in humans or animals.
One peptide, three targets
Earlier compounds in the class were designed around one receptor (GLP-1 receptor agonists) or two (dual GIP and GLP-1 receptor agonists). Retatrutide adds a third target: the glucagon receptor.
Each receptor sits in a different part of metabolic signalling:
- GIP receptor — activated by glucose-dependent insulinotropic polypeptide, an incretin hormone released from K-cells in the upper small intestine.
- GLP-1 receptor — activated by glucagon-like peptide-1, an incretin hormone released from L-cells further down the gut.
- Glucagon receptor — found mainly in the liver, where glucagon signalling regulates glucose output and lipid metabolism.
Preclinical work published by Lilly scientists (Coskun et al., Cell Metabolism, 2022) described the molecule's design and reported its relative activity at each of the three human receptors.
Structure in brief
Property | Value |
|---|---|
Development code | LY3437943 |
CAS number | 2381089-83-2 |
Molecular formula | C221H342N46O68 |
Molecular weight | about 4731 g/mol |
Type | Synthetic acylated peptide |
Like other long-acting peptides in its class, retatrutide carries a fatty-acid side chain attached through a linker. The side chain lets the molecule bind to albumin in the blood, which slows its clearance and gives it a long elimination half-life (about six days in published phase 1 data). The sequence also includes non-standard amino acids, such as α-aminoisobutyric acid (Aib), which protect it against breakdown by the enzyme DPP-4.
Research status
Retatrutide is an investigational compound. Results from phase 2 studies were published in 2023, and Lilly runs a phase 3 clinical programme. At the time of writing it is not approved as a medicine by the EMA, the MHRA or the FDA. Check those regulators' registers for the current status, because it can change.
What R3TA supplies
R3TA supplies retatrutide as a lyophilised (freeze-dried) powder, 10 mg per sealed glass vial, for laboratory research only. Every batch is tested by an independent laboratory for identity and purity, and the certificate of analysis for that batch ships with the vials. See the lab reports and the specifications.
R3TA products are not medicines, food, supplements or cosmetics, and they are not for human or veterinary use.