Retatrutide
Retatrutide (LY3437943) is an investigational once-weekly triple GIP/GLP-1/glucagon receptor agonist peptide developed by Eli Lilly and studied in Phase 3 trials for obesity and type 2 diabetes; it is not approved by any regulator.
Retatrutide, also known by its development code LY3437943, is a synthetic 39-amino-acid peptide developed by Eli Lilly. It is described in the peer-reviewed literature as a single peptide that acts as a triple agonist at three metabolic hormone receptors at once: the receptors for glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon — earning it the informal nickname "Triple G."
Structurally, retatrutide is built on a GIP-based peptide backbone that incorporates several non-coded amino acid residues (including aminoisobutyric acid (Aib) substitutions and an alpha-methyl-leucine) to resist enzymatic degradation, plus a C20 fatty-diacid side chain attached via a lysine-linked linker. This lipidation lets the molecule bind serum albumin, extending its half-life to approximately 6 days and supporting once-weekly subcutaneous dosing in trials. The peptide is C-terminally amidated.
Clinically, retatrutide has been studied in a Phase 2 obesity trial published in the New England Journal of Medicine (2023) and a Phase 2a trial for metabolic dysfunction-associated steatotic liver disease (MASLD) published in Nature Medicine (2024). It is currently the subject of Eli Lilly's late-stage Phase 3 programs — TRIUMPH (obesity) and TRANSCEND-T2D (type 2 diabetes).
Retatrutide is an investigational compound and is not approved by the FDA, EMA, MHRA, or any other regulator as of 2026. It is not a licensed medicine, has no approved label or dosing guidance, and material offered by research-chemical suppliers is not pharmaceutical-grade or quality-assured for human or veterinary use.
Retatrutide is a single synthetic 39-residue peptide that simultaneously activates the receptors for glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon, making it a "triple" (Triple G) hormone-receptor agonist. It is engineered with non-coded residues (e.g. Aib substitutions, an alpha-methyl-leucine) and a C20 fatty-diacid side chain that binds serum albumin to extend its half-life to roughly 6 days, supporting once-weekly subcutaneous dosing in clinical studies.
- Human evidence
- Phase 3 clinical trials ongoing; not approved
- Regulatory status
- Investigational compound developed by Eli Lilly. In Phase 3 clinical trials (e.g. TRIUMPH obesity program, TRANSCEND-T2D type 2 diabetes program). NOT approved by the FDA, EMA, MHRA, or any regulator as of 2026; not a licensed medicine.
- Studied in published clinical research as an investigational treatment for obesity and overweight (e.g. Phase 2 NEJM trial; Phase 3 TRIUMPH program).
- Investigated for type 2 diabetes glycemic control in Phase 3 trials (TRANSCEND-T2D).
- Examined in Phase 2a research for metabolic dysfunction-associated steatotic liver disease (MASLD) and reported in cardiometabolic outcome studies.
- Used as a reference triple GIP/GLP-1/glucagon agonist in mechanistic and incretin-pharmacology research.
- Clinical trials report dose-dependent gastrointestinal adverse events (nausea, vomiting, diarrhea, constipation, abdominal discomfort) as the most common side effects, generally mild-to-moderate and more frequent at higher doses (Nature Medicine 2024, PMC11271400; NEJM 2023).
- Modest dose-related increases in heart rate have been observed in trials, consistent with the incretin/glucagon-agonist class.
- An investigational agent that has not completed regulatory review; long-term safety in humans is not established and no approved label or dosing guidance exists.
- Material sold by research-chemical suppliers is not a pharmaceutical-grade medicine and is not quality-assured for human or veterinary use.
- [1]PubChem CID 171390338 — Retatrutide (C221H342N46O68)PubChem
- [2]Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial (NEJM 2023)New England Journal of Medicine
- [3]Triple hormone receptor agonist retatrutide for MASLD: a randomized phase 2a trial (PMC11271400)PMC / Nature Medicine
- [4]Retatrutide — overview, mechanism and development statusWikipedia