What Is Retatrutide (GLP-3)? The Triple-Agonist Research Guide 2026
Retatrutide — also called GLP-3, LY-3437943, and NOP2Y096GV — is a synthetic peptide research compound developed by Eli Lilly that simultaneously activates three receptors: the glucagon-like peptide-1 receptor (GLP-1R), the glucose-dependent insulinotropic polypeptide receptor (GIPR), and the glucagon receptor (GCGR). This triple-agonist profile places retatrutide in a category of its own — a step beyond dual agonists like tirzepatide (GLP-1R + GIPR) and well beyond single GLP-1 agonists like semaglutide. As of 2026, retatrutide is one of the most searched research compounds in the peptide space, with year-over-year search growth exceeding 500%.
The GLP Receptor Triad: What Each Target Does
Understanding retatrutide starts with understanding why each of its three receptor targets was chosen. The GLP-1 receptor is the most familiar — it mediates insulin secretion, glucagon suppression, gastric emptying delay, and central satiety signaling. This is the same receptor activated by semaglutide (Ozempic, Wegovy) and the GLP-1 component of tirzepatide (Mounjaro, Zepbound).
The GIP receptor (GIPR) is the second target, shared with tirzepatide. GIP is secreted by intestinal K-cells and enhances insulin secretion in a glucose-dependent manner. It also plays a role in fat metabolism and adipocyte signaling. Adding GIPR activity to GLP-1R activity produces synergistic metabolic effects beyond what GLP-1R agonism alone can achieve.
The third target — the glucagon receptor (GCGR) — is what makes retatrutide genuinely novel. Glucagon typically raises blood glucose and stimulates hepatic glucose output. In the context of triple agonism, controlled GCGR activation drives increased energy expenditure and fatty acid oxidation, particularly in the liver and adipose tissue. The net metabolic effect of GCGR co-activation is catabolic — working alongside GLP-1R and GIPR to produce a broader metabolic response than dual agonism alone achieves.
Retatrutide in Phase 3: What the Trial Data Shows
Eli Lilly’s Phase 2 dose-ranging study published in The New England Journal of Medicine (2023) was the research community’s first major window into retatrutide’s clinical profile. At the highest dose (12 mg weekly), participants showed mean body weight reductions exceeding 17% at 24 weeks and approaching 24% at 48 weeks — outcomes that outpaced both semaglutide 2.4 mg and tirzepatide 15 mg in direct timeline comparisons, though head-to-head trial data is not yet available.
Retatrutide’s Phase 3 program (TRIUMPH trials) enrolled tens of thousands of participants across metabolic, cardiovascular, and liver disease indications. The TRIUMPH-1 trial focuses on body weight outcomes; TRIUMPH-3 assesses cardiovascular risk reduction; other arms investigate metabolic-associated steatohepatitis (MASH) and chronic kidney disease. Results from TRIUMPH-1 are expected in 2025–2026, with regulatory submission to follow. Retatrutide has no regulatory approval as of 2026 and remains a research compound.
Retatrutide vs. Semaglutide vs. Tirzepatide: A Research Comparison
| Compound | Receptors | Developer | Half-Life | Phase 2 Weight Change (peak dose) | Approval Status |
|---|---|---|---|---|---|
| Retatrutide (GLP-3) | GLP-1R + GIPR + GCGR | Eli Lilly | ~6 days | ~24% at 48 wk | Phase 3 (research only) |
| Tirzepatide | GLP-1R + GIPR | Eli Lilly | ~5 days | ~20% at 72 wk | FDA-approved (Mounjaro/Zepbound) |
| Semaglutide 2.4 mg | GLP-1R | Novo Nordisk | ~7 days | ~15% at 68 wk | FDA-approved (Wegovy) |
Molecular Identity of Retatrutide (GLP-3)
Retatrutide carries CAS number 2381089-83-2. It is a 36-amino acid acylated peptide with a C18 fatty diacid albumin-binding chain that confers its approximately 6-day plasma half-life, supporting weekly research dosing protocols. The compound is also tracked under ChEMBL5095485 and PubChem identifiers. In the research community it is frequently referred to interchangeably as GLP-3, retatrutide, and LY-3437943 — all designations for the same compound.
Why Retatrutide Is the Most-Watched Compound in Peptide Research
The +500% year-over-year growth in retatrutide searches reflects a broader shift in metabolic research interest. After semaglutide established GLP-1R agonism as a transformative mechanism and tirzepatide demonstrated that adding GIPR synergizes the effect, the logical research question became: what does the third receptor add? Retatrutide is the most advanced answer to that question currently in the clinical pipeline. For research purposes, it represents the most biologically complex GLP peptide available, enabling investigation of triple-receptor co-activation that no prior compound has made accessible.
Frequently Asked Questions — Retatrutide (GLP-3)
Is retatrutide the same as GLP-3?
Yes. “GLP-3” is the informal research community designation for retatrutide (LY-3437943). It reflects the compound’s position as a triple agonist that expands on the GLP-1 and GLP-1/GIP dual agonist frameworks.
How does retatrutide differ from tirzepatide?
Tirzepatide is a dual agonist targeting GLP-1R and GIPR. Retatrutide adds glucagon receptor (GCGR) activation, which drives additional energy expenditure through hepatic fatty acid oxidation and thermogenic pathways — a mechanism not accessible via dual agonism alone.
Is retatrutide FDA-approved?
No. As of 2026, retatrutide is in Phase 3 clinical trials. It is not approved by the FDA, EMA, or any regulatory agency for therapeutic use. It is available strictly as a research compound.
What sizes does Combat Research offer for GLP-3/Retatrutide?
Combat Research supplies retatrutide in 10 mg (pilot/validation protocols), 15 mg (extended research runs), and 30 mg (high-throughput / best-value) vials, all at ≥99% HPLC purity.
→ Browse Combat Research GLP-3 (Retatrutide) Research Peptide
