Pillar reference for retatrutide, the synthetic triple GLP-1 / GIP / glucagon (GCGR) receptor agonist examined in the TRIUMPH trial programme. Covers mechanism, TRIUMPH-1 Phase 2 readouts, ongoing Phase 3 trials, and UK sourcing standards. For in-vitro and preclinical research use only.
What is retatrutide?
Retatrutide is a synthetic 39-amino-acid peptide engineered as a triple agonist at the GLP-1, GIP, and glucagon receptors. The molecule incorporates a fatty-acid moiety enabling albumin binding and a research half-life supporting once-weekly subcutaneous dosing. Retatrutide is currently an investigational compound — it is not authorised for human medicinal use by the MHRA, FDA, or EMA. Material supplied by Peptides Lab UK is for laboratory in-vitro and preclinical research only.
Mechanism — triple incretin + glucagon agonism
Retatrutide combines the established dual incretin profile (GLP-1 + GIP) with glucagon-receptor activity. The glucagon-receptor component contributes an additional energy-expenditure mechanism in research models — increasing hepatic energy use and lipolysis — which is hypothesised to drive the larger body-weight changes observed in TRIUMPH-1 versus tirzepatide and semaglutide.
- GLP-1 receptor — glucose-dependent insulinotropic, satiety, gastric emptying.
- GIP receptor — additional insulinotropic activity, adipose lipid handling.
- Glucagon (GCGR) receptor — increases hepatic energy expenditure and lipolysis; balanced against potential hyperglycaemic effect by the dominant incretin agonism.
TRIUMPH trial readouts
| Trial | Phase | Population | Headline result |
|---|---|---|---|
| TRIUMPH-1 | Phase 2 | Adults with obesity, no diabetes | ~ -24.2% body weight at 48 wk (12 mg dose) |
| TRIUMPH-2 | Phase 3 | Adults with obesity + T2D | Ongoing — 2026 readout pending |
| TRIUMPH-3 | Phase 3 | Adults with obesity + cardiovascular disease | Ongoing |
| TRIUMPH-4 | Phase 3 | Adults with obesity + osteoarthritis | Ongoing |
Side-effect signal (research observations)
TRIUMPH-1 reported gastrointestinal adverse events consistent with the GLP-1 class — nausea, vomiting, diarrhoea, constipation — predominantly mild-to-moderate and titration-related. Triple-agonism-specific signals (e.g., transient heart-rate increases, transient elevations in fasting glucose linked to glucagon agonism at higher doses) are under continued investigation in Phase 3.
Comparison vs other GLP-1-class research peptides
| Compound | Receptors | Best published BW reduction | Phase |
|---|---|---|---|
| Semaglutide | GLP-1 | ~ -14.9% (STEP-1, 2.4 mg, 68 wk) | Approved |
| Tirzepatide | GLP-1 + GIP | ~ -22.5% (SURMOUNT-1, 15 mg, 72 wk) | Approved |
| Retatrutide | GLP-1 + GIP + GCGR | ~ -24.2% (TRIUMPH-1, 12 mg, 48 wk) | Phase 3 |
Pharmacokinetics summary
| Parameter | Retatrutide |
|---|---|
| Molecular weight | ~4,731 Da |
| Route | Subcutaneous (research) |
| Tmax | ~24–48 hours |
| Steady-state | ~4–6 weeks |
| Half-life | ~6 days |
| Elimination | Peptide-backbone proteolysis; renal/biliary metabolite excretion |
Why triple agonism matters mechanistically
Retatrutide’s distinguishing feature versus the dual GLP-1/GIP class (tirzepatide) is the addition of glucagon-receptor agonism. Glucagon-receptor activation in research models drives hepatic energy expenditure and lipolysis — an additional weight-loss-relevant mechanism that is independent of the incretin pathway. The trade-off is the potential for transient hyperglycaemic effects from glucagon agonism at higher doses; the dominant incretin agonism (GLP-1 + GIP) maintains net glycaemic control in research participants based on TRIUMPH-1 endpoints.
Storage of lyophilised retatrutide is at -20 °C, protected from light. Reconstituted solution is stored at 2–8 °C and used within the manufacturer-stated stability window on the batch Certificate of Analysis. Avoid freeze-thaw cycles of reconstituted solution.
UK sourcing & analytical standards
Research-grade retatrutide must ship with batch-level HPLC purity, mass-spectrometry identity confirmation, and bacterial endotoxin quantification on an independent COA. Peptides Lab UK supplies retatrutide with Optima Labs (UK) certification, typical 99.0–99.7% HPLC, with same-day UK dispatch.
Available SKU
FAQs — retatrutide in UK research
What is retatrutide?
Retatrutide is a synthetic triple-receptor agonist with activity at GLP-1, GIP, and glucagon receptors. In published Phase 2 (TRIUMPH-1) and ongoing Phase 3 research, it is investigated for energy balance, hepatic lipid handling, and metabolic regulation.
Is retatrutide legal to buy in the UK?
Retatrutide is an experimental compound that has not been authorised by the UK MHRA for human medicinal use. It may be supplied for laboratory research use only and is not for human or veterinary consumption.
How does retatrutide differ from tirzepatide and semaglutide?
Semaglutide is a single GLP-1 agonist. Tirzepatide is dual GLP-1/GIP. Retatrutide adds glucagon-receptor activity for triple GLP-1/GIP/GCGR agonism — see tirzepatide vs semaglutide reference for the dual-vs-single comparison.
What’s the published weight-loss endpoint for retatrutide?
~24.2% mean body-weight reduction at 48 weeks at the 12 mg dose in TRIUMPH-1 Phase 2. Phase 3 confirmation pending.
Last updated: 26 April 2026. Reviewed by William, Lead Research Editor, Peptides Lab UK. For in-vitro and preclinical research use only.
