Retatrutide is an investigational peptide that activates three hormone receptors at once: the GIP receptor, the GLP-1 receptor and the glucagon receptor. Developed by Eli Lilly under the code name LY3437943, it is being evaluated in late-stage clinical trials for metabolic conditions and is not yet an approved medicine. This guide explains what retatrutide is, the mechanism researchers are studying, and how the compound is handled in the lab.
What is retatrutide?
Retatrutide belongs to the incretin-based class of peptides, the same broad family that includes semaglutide and tirzepatide. What sets it apart is the number of receptors it targets. Semaglutide acts on the GLP-1 receptor, tirzepatide acts on the GIP and GLP-1 receptors, and retatrutide adds the glucagon receptor to make a single-molecule triple agonist.
Structurally, retatrutide is one engineered peptide chain rather than a mix of separate hormones. It includes non-natural amino acids that help resist enzymatic breakdown and a fatty-acid side chain that allows it to bind albumin in the blood. Albumin binding is a common strategy in this class for extending how long a peptide stays in circulation.
Retatrutide is investigational. It has not been approved by the FDA, and its clinical program is ongoing. PRIME supplies retatrutide under the store name GLP-3 RT as a research compound for laboratory use only.
How retatrutide works: mechanism studied in research
Each of the three receptors retatrutide targets has a distinct role in metabolic signaling, and research interest centers on how they act in combination.
- GLP-1 receptor: activation is associated with glucose-dependent insulin release, slower gastric emptying and appetite-related signaling in the brain. This is the pathway targeted by approved GLP-1 medicines.
- GIP receptor: GIP is the other major incretin hormone. Its receptor is involved in insulin secretion and has been studied for effects on adipose tissue and on the tolerability of GLP-1 signaling.
- Glucagon receptor: glucagon raises blood glucose on its own, but in research settings its receptor is also studied for roles in energy expenditure and fat metabolism in the liver.
The rationale behind a triple agonist is that the glucose-raising effect of glucagon receptor activation can be balanced by the incretin receptors, while the combined signaling may act on body weight, glucose control and liver fat through several routes at once. The relative potency at each receptor is a deliberate part of the molecule's design, and the exact balance is one of the main questions in current research.
For researchers, this makes retatrutide a useful tool for separating the contribution of each receptor. Comparing it side by side with a GLP-1 receptor agonist and a GIP and GLP-1 dual agonist allows a study to ask what the added glucagon receptor activity changes in a given model, whether in liver lipid handling, energy expenditure or glucose regulation. Receptor-specific antagonists and knockout models are commonly used alongside such comparisons to attribute an observed effect to a particular pathway.
Areas of retatrutide research
Retatrutide is being investigated in clinical trials and has also been characterized in preclinical studies. Research areas include:
- Obesity and body-weight regulation in clinical trials
- Glycemic control in type 2 diabetes
- Liver fat and metabolic dysfunction-associated fatty liver disease
- Cardiometabolic markers such as lipids and blood pressure
- Energy expenditure and receptor pharmacology in animal models
- Comparative studies against single and dual incretin agonists
Because retatrutide is still investigational, published findings describe what has been measured in trials and models rather than established clinical use. Anyone following the field should watch for regulatory decisions rather than drawing conclusions from early data.
Retatrutide key facts
| Property | Detail |
|---|---|
| Class | Incretin-based peptide; GIP, GLP-1 and glucagon receptor triple agonist |
| Code name | LY3437943 |
| Structure | Single engineered peptide chain with non-natural amino acids and a fatty-acid side chain for albumin binding |
| Developer | Eli Lilly |
| Form supplied | Lyophilized powder in a sealed vial |
| Research status | Investigational; in late-stage clinical trials; not FDA-approved |
| Store name | GLP-3 RT |
| Storage | Lyophilized: cold, dry and dark. Reconstituted: refrigerated and protected from light |
Handling and storage of retatrutide in the lab
Retatrutide is supplied as a lyophilized powder, which is the most stable form for transport and storage. Keep unopened vials cold and away from light, and avoid leaving them at room temperature for long periods. Lipidated peptides can be prone to sticking to surfaces and forming aggregates in solution, so gentle handling matters.
For experiments that require a solution, researchers commonly reconstitute with bacteriostatic water using sterile technique:
- Allow the vial to reach room temperature before opening.
- Swab the stopper with alcohol.
- Add diluent slowly along the inside wall of the vial.
- Swirl or roll gently until the powder dissolves; do not shake hard.
- Label with the date and concentration used in your experiment, then refrigerate and protect from light.
Cloudiness or visible particles after reconstitution can indicate aggregation or contamination and are a reason to check the material before it is used. Avoid repeated freeze-thaw cycles of solutions.
Quality and lab results
For a large, modified peptide like retatrutide, identity testing is essential because small synthesis errors can change the molecule. Every PRIME batch has a published certificate of analysis, and you can review the COA for each batch on our lab results page. A COA usually confirms identity by mass spectrometry and reports purity by HPLC. Check that the lot number on your vial matches the report before starting work.
Related research
Retatrutide is easiest to understand next to the incretin drugs that came before it. See tirzepatide vs retatrutide for the dual versus triple agonist comparison and semaglutide vs retatrutide for the single versus triple view. The tirzepatide research guide covers the approved dual agonist in depth, and PRIME also carries GLP-2 TZ for comparative work.
Retatrutide FAQ
Is retatrutide FDA approved?
No. Retatrutide is investigational and is being evaluated in late-stage clinical trials. It has not been approved by the FDA. PRIME sells it for laboratory research use only.
How is retatrutide different from tirzepatide?
Tirzepatide activates the GIP and GLP-1 receptors. Retatrutide activates those two plus the glucagon receptor. Tirzepatide is FDA-approved as Mounjaro and Zepbound, while retatrutide remains investigational.
Why is retatrutide called a triple agonist?
Because a single molecule activates three receptors: GIP, GLP-1 and glucagon. Researchers are studying how the combined signaling affects body weight, glucose control and liver fat compared with single and dual agonists.
What is GLP-3 RT?
GLP-3 RT is the PRIME store name for retatrutide supplied as a lyophilized research compound. GLP-3 is an informal shorthand for the triple agonist, not a separate hormone.
How should retatrutide be stored?
Keep lyophilized retatrutide cold, dry and protected from light. After reconstitution for lab use, keep solutions refrigerated, protected from light, and use them within the period set by your lab's procedures.
For laboratory research use only. Not for human consumption. Not a drug, food or cosmetic.