Retatrutide Research Hub (LY3437943) | Triple GLP-1R/GIPR/GCGR Agonist
Retatrutide (LY3437943) is Eli Lilly’s investigational triple G receptor agonist — the first compound to simultaneously activate GLP-1R, GIPR, and GCGR. Phase 2 data reported the largest weight reduction of any injectable drug in clinical trials at the time (24.2% at 48 weeks). This hub covers the mechanism, the clinical data, TRIUMPH Phase 3 status, and research protocols for in vitro and in vivo triple receptor agonism studies.
Triple G
GLP-1R + GIPR + GCGR
24.2%
Phase 2 weight reduction (48 wk)
TRIUMPH
Phase 3 program ongoing
≥99%
QSC purity — HPLC + MS
What Makes Retatrutide Different: The Triple Receptor Mechanism
The GLP-1 receptor agonist class began with selective GLP-1R agonists (semaglutide, liraglutide). Tirzepatide added GIPR co-agonism to produce the dual mechanism. Retatrutide extends this to a third receptor — the glucagon receptor (GCGR) — producing the first triple receptor agonist in advanced clinical development. Each receptor contributes distinct metabolic effects:
Core anti-hyperglycaemic and appetite-suppressing axis — shared with semaglutide and tirzepatide
GIPR
Insulin secretion (additive to GLP-1R), adipose lipolysis, energy expenditure, GLP-1R sensitisation in hypothalamus
Additive weight reduction beyond selective GLP-1R — shared with tirzepatide
GCGR
Hepatic glucose production, thermogenesis, fat oxidation, increased energy expenditure, ketogenesis
Third axis: increases total energy expenditure beyond GLP-1R+GIPR; the proposed driver of retatrutide’s weight reduction advantage over tirzepatide
The glucagon paradox in retatrutide
Glucagon at GCGR raises blood glucose — the opposite of insulin. Adding GCGR agonism to an insulin-stimulating, glucagon-suppressing GLP-1R agonist appears counterproductive. The clinical data suggests it is not: GLP-1R-mediated glucose-dependent insulin secretion compensates for GCGR-driven glucose production, while GCGR’s thermogenic and lipolytic effects add meaningfully to total weight reduction. The net glycaemic effect is neutral-to-beneficial in the Phase 2 data, though with modestly more glycaemic variability than dual agonism. This balance is an active mechanistic research question.
Phase 2 Clinical Data: Jastreboff et al. NEJM 2023
The pivotal Phase 2 trial enrolled 338 participants with obesity (BMI ≥30) without type 2 diabetes, randomised to retatrutide 1mg, 4mg, 8mg, or 12mg weekly, or placebo. Duration: 48 weeks. Primary endpoint: percentage change in body weight from baseline.
Dose
Mean weight reduction (48 wk)
≥5% reduction
≥10% reduction
≥15% reduction
≥20% reduction
Placebo
−2.1%
25%
7%
2%
0%
1mg weekly
−8.7%
75%
38%
22%
8%
4mg weekly
−17.3%
92%
75%
54%
30%
8mg weekly
−22.8%
100%
91%
75%
52%
12mg weekly
−24.2%
100%
93%
83%
60%
The 12mg dose achieving 24.2% mean weight reduction at 48 weeks was the headline finding — exceeding the ~22.5% reported for tirzepatide 15mg at 72 weeks in SURMOUNT-1, though direct comparison across trials is methodologically limited. Approximately 26% of participants on 12mg achieved ≥30% weight reduction. No plateau was apparent at 48 weeks — the weight loss trajectory was still descending — suggesting longer treatment would produce further reduction.
Glycaemic data (T2D subgroup and pre-diabetic participants)
In participants with prediabetes at baseline, retatrutide produced HbA1c reductions of 0.7–1.0% at the higher doses, with approximately 65% of prediabetic participants reverting to normoglycaemia. A separate Phase 2 trial in T2D (n=281, 24 weeks) showed retatrutide 12mg reducing HbA1c by 2.02% and body weight by 16.9% — establishing efficacy in the diabetic population ahead of the TRIUMPH-2 Phase 3 arm.
Cardiovascular and lipid effects
Phase 2 data showed retatrutide produced significant reductions in triglycerides (up to −36% at 12mg), LDL-cholesterol, and blood pressure, consistent with the GLP-1R agonist class cardiovascular benefit profile. Waist circumference reduction was substantial (−17–20cm at highest doses). TRIUMPH-3 will provide dedicated cardiovascular outcomes data.
Mechanism Research: What Each Receptor Pathway Contributes
GLP-1R pathway in retatrutide
GLP-1R activation provides the foundation: glucose-dependent insulin secretion from pancreatic beta cells, glucagon suppression from alpha cells, gastric emptying delay reducing postprandial glucose excursions, and hypothalamic appetite suppression via POMC/CART neuron stimulation and NPY/AgRP inhibition. These effects are well-characterised from the semaglutide and tirzepatide literature and are preserved in retatrutide’s GLP-1R component.
GIPR pathway in retatrutide
GIPR co-agonism adds insulin secretion amplification (particularly at low glucose concentrations where GLP-1R effects are minimal), direct adipose lipolysis, thermogenic effects in adipose tissue, and — critically — appears to potentiate GLP-1R signalling in hypothalamic appetite circuits. The GIPR contribution to weight reduction is the primary mechanism differentiating tirzepatide from selective GLP-1R agonists. Retatrutide inherits this GIPR contribution.
GCGR pathway: the retatrutide differentiator
Glucagon receptor agonism is the unique component. GCGR activation in the liver increases hepatic glucose production (via glycogenolysis and gluconeogenesis) — a hyperglycaemic signal that GLP-1R co-activation must compensate for. GCGR activation also stimulates brown adipose tissue thermogenesis, increases whole-body fat oxidation, promotes ketogenesis (increased fatty acid utilisation), and reduces appetite independently of GLP-1R via hypothalamic GCGR signalling. The thermogenic and lipolytic GCGR effects add an energy-expenditure-increasing mechanism absent in semaglutide and tirzepatide — which is the proposed driver of retatrutide’s weight reduction advantage. Research into the precise contribution of GCGR vs GLP-1R+GIPR can be conducted by comparing retatrutide with tirzepatide in parallel experimental arms at receptor-equivalent doses.
TRIUMPH Phase 3 Program: Current Status
Trial
Population
Primary endpoint
Status (2025)
TRIUMPH-1
Obesity (BMI ≥27), no T2D
% weight change at 48–72 weeks
Enrolling / ongoing
TRIUMPH-2
Type 2 diabetes + obesity
HbA1c reduction + weight
Enrolling / ongoing
TRIUMPH-3
Obesity + established CVD
MACE (cardiovascular outcomes)
Enrolling / ongoing
TRIUMPH-NASH
NASH/MASH + obesity
Liver biopsy resolution
Enrolling / ongoing
Research Protocols
Model
Suggested dose range
Route
Duration
Key endpoints
Diet-induced obesity (DIO) rodent — weight
0.1–3 mg/kg weekly
SC injection
8–16 weeks
Body weight, fat mass (MRI/DEXA), food intake, energy expenditure (metabolic cage)
QSC retatrutide is synthesised in-house at our Qingdao facility via Fmoc solid-phase peptide synthesis and verified to ≥99% purity by HPLC and mass spectrometry on every batch. The Janoshik-verified Certificate of Analysis — including full HPLC chromatogram and MS molecular weight confirmation — is published on the product page.
USA, EU, UK, Canada, Australia — domestic warehouse in each region
Recommended reconstitution
Bacteriostatic water — 1mg/mL stock at -20°C
Frequently Asked Questions
What is retatrutide?
Retatrutide (LY3437943) is a once-weekly injectable synthetic peptide developed by Eli Lilly that simultaneously activates three receptors: GLP-1R (glucagon-like peptide-1 receptor), GIPR (glucose-dependent insulinotropic polypeptide receptor), and GCGR (glucagon receptor). This triple receptor co-agonism — sometimes called a ‘triple G’ agonist — produces greater metabolic effects than dual GLP-1R/GIPR agonism (tirzepatide) in Phase 2 clinical data. Retatrutide Phase 3 trials (TRIUMPH program) are ongoing as of 2025.
How much weight loss does retatrutide cause?
Phase 2 trial data (Jastreboff et al., NEJM 2023) showed retatrutide 12mg produced a mean 24.2% body weight reduction at 48 weeks in obese participants without type 2 diabetes — the largest weight reduction reported for any GLP-1R agonist class drug in Phase 2 data at that time. Approximately 26% of participants achieved ≥30% weight reduction at 48 weeks on the highest dose. Phase 3 TRIUMPH trial results are anticipated 2025–2026.
How does retatrutide differ from tirzepatide?
Tirzepatide (Mounjaro/Zepbound) is a dual GLP-1R/GIPR agonist. Retatrutide adds a third receptor — the glucagon receptor (GCGR) — to the tirzepatide dual mechanism. GCGR activation increases hepatic glucose production, thermogenesis, fat oxidation, and energy expenditure. The addition of glucagon receptor agonism is the proposed mechanism behind retatrutide’s greater weight reduction vs tirzepatide in comparable Phase 2 data. The tradeoff is potential for greater blood glucose variability and more pronounced GI side effects with GCGR co-activation.
What is the TRIUMPH clinical trial program?
TRIUMPH is the Phase 3 clinical trial program for retatrutide, initiated by Eli Lilly in 2023–2024. It includes multiple arms: TRIUMPH-1 (obesity, non-T2D), TRIUMPH-2 (type 2 diabetes), TRIUMPH-3 (obesity + cardiovascular disease), and TRIUMPH-NASH (non-alcoholic steatohepatitis). Results from the TRIUMPH program will determine FDA approval status. Phase 3 initiation followed the strong Phase 2 data from the 338-participant Jastreboff 2023 NEJM trial.
Is retatrutide FDA approved?
As of 2025, retatrutide is not yet FDA approved. It is in Phase 3 clinical trials (TRIUMPH program). Eli Lilly has announced plans to file an NDA based on TRIUMPH results, with potential approval anticipated in 2026–2027 if Phase 3 data supports the Phase 2 findings. All retatrutide sold by QSC is for laboratory research use only, not for human consumption.
Research Use Only: All products sold on qsc-usa.com are intended strictly for laboratory research purposes only. They are not approved for human consumption, veterinary use, or any other application. Researchers are responsible for understanding and complying with local regulations in their jurisdiction.
