Overview
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In plain language
Retatrutide is an experimental weight-loss medicine from Eli Lilly. It acts on three hormone receptors at once (GIP, GLP-1 and glucagon), which is why it is called a "triple agonist."
In a mid-stage trial, people lost a large amount of weight on average. It is still being tested in large Phase 3 trials and is not FDA-approved. Products sold online as "retatrutide" are not regulated.
For students
Retatrutide (LY3437943, about 4,731 Da) is a single 39-residue peptide with a fatty diacid side chain for once-weekly dosing. It activates GIP, GLP-1 and glucagon receptors. GLP-1 and GIP activity reduce appetite and improve glucose control, while glucagon receptor activity is intended to increase energy expenditure and liver fat oxidation.
In a 48-week Phase 2 trial in adults with obesity (published in 2023), the highest dose produced mean weight loss of about 24%.
For researchers and instructors
Clinical program. Phase 3 TRIUMPH trials are evaluating obesity, type 2 diabetes, knee osteoarthritis, sleep apnea and cardiovascular and kidney outcomes.
Safety. Gastrointestinal effects were most common in Phase 2; dose-related increases in heart rate were observed. Long-term safety is not established.
Regulatory. Investigational and not FDA-approved. "Research" products sold online have unknown identity, purity and dose.
Molecular identity
- Amino acids
- 39 (modified)
- Molecular weight
- ~4,731.4 Da
- Formula
- C₂₂₁H₃₄₂N₄₆O₆₈
- Sequence
- Modified 39-residue peptide with a fatty diacid chain
Origin and history
Retatrutide is Eli Lilly’s next step after tirzepatide: a single molecule that activates three hormone receptors, GIP, GLP-1 and glucagon. Adding glucagon was meant to increase energy burning.
A Phase 2 trial in 2023 reported 24% average weight loss at 48 weeks. In May 2026 the first Phase 3 trial, TRIUMPH-1, reported average weight loss of 28.3% at 80 weeks on the highest dose. It remains investigational and is not approved.
Key people
- Eli LillyDeveloper
- Ania JastreboffLead author of the 2023 Phase 2 trial
Timeline
- 2022
First human (Phase 1) results
- 2023
Phase 2: 24% weight loss at 48 weeks
- 2026
Phase 3 TRIUMPH-1: 28.3% weight loss at 80 weeks
See every peptide on one history timeline.
Human evidence
Phase 3 trials are under way for obesity, type 2 diabetes and related conditions. Results to date are from clinical trials, not approved use.
Registration and enrollment are not proof of benefit; check study results directly.
Explore original publications and distinguish preclinical findings from controlled human evidence.
Safety and regulatory status
See every compound on the regulatory tracker.
Investigational and not FDA-approved. Products sold online as “retatrutide” are unregulated and are not the investigational drug.
This profile is educational and does not provide treatment, dosing or sourcing guidance.
Sources
- PubMed literature search: Retatrutide
- PubChem compound search: Retatrutide
- Jastreboff et al. 2023, NEJM
- AJMC: TRIUMPH-1 results (2026)
- ClinicalTrials.gov search: Retatrutide
Hernandez Gener, E. (2026, November 7). Retatrutide: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/retatrutide.html
APA style · Last reviewed November 7, 2026 · Our editorial standardsLast reviewed November 7, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy