Retatrutide (GLP3): The Ultimate Guide to the Triple-Agonist Peptide
Written by: The BulkGLP Research Team Last Updated: July 30, 2025
Retatrutide, also known by its research code LY3437943 and informally referred to in research communities as "GLP3," "the triple agonist peptide," or simply "Reta," is a new investigational peptide at the forefront of metabolic research. This guide provides a comprehensive scientific overview of its mechanism, clinical trial data, and its place in the future of weight management therapies.
For Educational & Research Use Only: The information in this guide is for educational purposes. Retatrutide is an investigational compound not approved for human consumption. It should only be handled by qualified professionals in a laboratory setting.
What is Retatrutide?
Retatrutide (LY-3437943) is a unimolecular peptide therapeutic developed by Eli Lilly. At its core, it is an engineered chain of 39 amino acids based on a GIP peptide backbone, modified for enhanced stability and a long duration of action.
Why is it Called GLP3? The Triple-Agonist Mechanism Explained
The informal nickname "GLP3" arises from Retatrutide's groundbreaking mechanism as a triple-agonist. It is the first investigational peptide designed to activate three distinct hormone receptors involved in metabolism:
- GLP-1 (Glucagon-Like Peptide-1) Receptor: Promotes satiety and insulin secretion.
- GIP (Glucose-dependent Insulinotropic Polypeptide) Receptor: A powerful insulin stimulator that also influences fat metabolism.
- Glucagon (GCG) Receptor: This novel third target increases energy expenditure and promotes fat burning (lipolysis).
Sourcing Peptides for Your Research?
For researchers seeking high-purity Retatrutide (GLP3) for laboratory study, BulkGLP provides third-party tested products.
View Lab-Grade Retatrutide Here →Clinical Trial Results & Potential Benefits
Phase 2 clinical trial data published in The New England Journal of Medicine showed unprecedented efficacy. Participants on the highest dose achieved a mean body weight reduction of 24.2%. The ongoing Phase 3 TRIUMPH program is further evaluating benefits for weight loss, glycemic control, and cardiovascular health.
Known Side Effects in Research
Consistent with the incretin class, the most common side effects are gastrointestinal, including nausea, diarrhea, and vomiting. These are typically mild-to-moderate and managed with a slow dose-escalation schedule.
Dosage in Clinical Research
In clinical trials, Retatrutide was studied using a dose-titration protocol to improve tolerability. Participants typically started at a low dose (e.g., 2 mg) once weekly, which was gradually increased every 4 weeks to target maintenance doses of 4 mg, 8 mg, and 12 mg. This dose-escalation schedule is a key aspect of its research protocol.
Retatrutide vs. Semaglutide vs. Tirzepatide
A common question from researchers is how GLP3 (Retatrutide) differs from older GLP-1 peptides like Semaglutide or the dual-agonist Tirzepatide. The key difference lies in the number of metabolic pathways targeted.
| Feature | Retatrutide (GLP3) | Tirzepatide | Semaglutide |
|---|---|---|---|
| Mechanism | Tri-Agonist | Dual-Agonist | Mono-Agonist |
| Receptor Targets | GLP-1, GIP, Glucagon | GLP-1, GIP | GLP-1 |
| Mean Weight Loss | ~24.2% (at 48 wks) | ~20.9% (at 72 wks) | ~14.9% (at 68 wks) |
Retatrutide Price, Reviews, and Where to Buy for Research
Price for Research Use
As a research-grade chemical, the price of Retatrutide can vary based on factors like purity (e.g., >99%), quantity (mg), and the supplier's quality control standards. It is sold exclusively for in-vitro laboratory studies and not for human use.
Researcher Reviews
“Really easy to order and fast shipping to our lab. Peptide quality has been consistent—BulkGLP’s team helped us find the right format for our research.”
Where to Buy Retatrutide (GLP3)
For scientific institutions and individual researchers looking for a reliable source, it is crucial to choose a supplier that provides third-party testing documentation, such as HPLC and MS data, to verify purity and identity.
Frequently Asked Questions
When is the Retatrutide release date?
Retatrutide is not yet approved by the FDA. Depending on the results of its Phase 3 trials, an application for approval could be submitted in the 2026-2027 timeframe.
What is the difference between GLP1 and GLP3?
"GLP-1" refers to peptides that only target the GLP-1 receptor (like Semaglutide). "GLP3" is an informal name for Retatrutide, which targets three receptors: GLP-1, GIP, and Glucagon.
