Retatrutide
Triple GIP/GLP-1/glucagon receptor agonist
A triple agonist (GLP-1/GIP/glucagon) representing the newest class in GLP-axis research.
Also referenced as: GLP-R3
Overview
An investigational peptide developed by Eli Lilly as a single molecule targeting three receptors: GIP, GLP-1, and glucagon. It has been evaluated in clinical trials in the 2020s.
At a glance
What Retatrutide does
Retatrutide is a triple agonist — sometimes called a 'triple-G' — that activates the GIP, GLP-1, and glucagon receptors from one synthetic peptide. The first two arms deliver the familiar incretin actions (glucose-dependent insulin secretion, glucagon-gated blood-sugar lowering, delayed gastric emptying, and central appetite suppression), while the added glucagon-receptor agonism is the novel element. Glucagon-receptor activation raises energy expenditure and promotes hepatic fat mobilization and lipolysis, so retatrutide is designed to burn energy as well as reduce intake — a mechanistic distinction from the dual and mono agonists. The glucagon arm is balanced against the GLP-1 arm so its glucose-raising tendency is offset by incretin-driven insulin secretion.
In phase 2 trials this combination produced the steepest weight-loss curve yet seen in the class. In the phase 2 obesity study (2023), the 12 mg weekly dose produced roughly 24% mean body-weight reduction at 48 weeks, and curves had not clearly plateaued, suggesting further loss was possible. A parallel phase 2 diabetes trial showed large HbA1c reductions, and an early study reported striking reductions in liver fat, with a high proportion of participants reaching near-complete resolution of hepatic steatosis — consistent with the glucagon-driven fat-mobilizing mechanism. Retatrutide is investigational: the evidence is human phase 2 with phase 3 programs underway, so long-term efficacy and safety are not yet established. Its distinguishing story is the addition of energy-expenditure and hepatic-lipid effects on top of appetite and glycemic control.
Effects reported in research
- Triple activation of GIP, GLP-1, and glucagon receptors from a single peptide (human clinical, phase 2).
- ~24% mean body-weight reduction at 12 mg weekly over 48 weeks in the phase 2 obesity trial, with curves not fully plateaued (human clinical).
- Increased energy expenditure via glucagon-receptor agonism, adding a 'burn' component on top of appetite suppression (mechanistic / human phase 2).
- Large reductions in liver fat, with a high proportion of participants reaching near-resolution of hepatic steatosis in an early trial (human clinical).
- Substantial HbA1c reductions in phase 2 type-2-diabetes participants (human clinical).
- Glucose-dependent insulin secretion and glucagon-gated glycemic lowering via the incretin arms (human clinical).
- Reduced appetite and food intake through GLP-1 central satiety pathways (human clinical).
- Long-term efficacy and cardiovascular/renal outcomes remain unestablished — phase 3 trials ongoing (investigational).
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
Retatrutide is a synthetic peptide agonist designed to activate the GIP, GLP-1, and glucagon receptors simultaneously. GIP and GLP-1 agonism support glucose-dependent insulin secretion, glucagon suppression, delayed gastric emptying, and appetite reduction, while glucagon-receptor agonism is proposed to increase energy expenditure. The combined activity is being studied for its effects on body weight and metabolic parameters.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which Retatrutide appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Investigational 'triple agonist' engineered to activate GIP, GLP-1, and glucagon receptors with one molecule
- Adds glucagon-receptor agonism, which is hypothesized to raise energy expenditure alongside appetite suppression
- Administered once weekly by subcutaneous injection in reported trials
- Evaluated in mid-stage (Phase 2) and later clinical programs for obesity and type-2 diabetes
- Represents an escalation in receptor breadth beyond dual GIP/GLP-1 agonism
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. Retatrutide is a research compound.
In the clinical literature retatrutide is administered once weekly with a stepwise escalation over several weeks. These are reference figures describing published research/protocols, not dosing guidance for humans.
- Phase 2 weekly escalation reference: 1 mg -> 2 mg -> 4 mg -> 8 mg -> 12 mg (each step ~4 weeks)
- Phase 3 (TRIUMPH) escalation reference: 1 -> 2 -> 4 -> 6 -> 9 -> 12 mg once weekly
- Common maintenance references in the literature: 4-12 mg once weekly
Half-life ~6 days drives the once-weekly schedule and multi-week escalation/washout. Investigational compound. Reference figures for research context only.
How it compares
Retatrutide differs from tirzepatide and semaglutide by adding a third target, the glucagon receptor, making it a triple agonist rather than a single or dual agonist.
Commonly studied alongside
Compounds frequently researched together with Retatrutide in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
Retatrutide sits in the GLP-1 Family area of the PeptiDex library.
- Entry type: Research compound reference
- Browse the full library →
- Glossary of terms →
Where researchers source Retatrutide
For researchers studying Retatrutide, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is retatrutide and what makes it a 'triple agonist'?
Retatrutide (LY3437943) is a single-molecule triple agonist that activates the GLP-1, GIP, and glucagon receptors. The added glucagon-receptor activity — associated in research with increased energy expenditure — is what distinguishes it from GLP-1 mono-agonists and GLP-1/GIP dual agonists. It is studied in models of obesity and metabolic regulation.
What is retatrutide's half-life and how does it shape study design?
Retatrutide has a reported half-life of approximately 6 days, which supports once-weekly administration in the published trials. Steady-state levels are generally reached after about 4-5 weeks of weekly dosing at a given dose, so protocols use a multi-week escalation before any maintenance readout. The long half-life implies a multi-week washout after stopping.
How is retatrutide dose-escalated in the clinical literature?
Phase 2 protocols escalated weekly in steps such as 1, 2, 4, 8, and up to 12 mg, each held about 4 weeks; later phase 3 (TRIUMPH) protocols used steps like 1 -> 2 -> 4 -> 6 -> 9 -> 12 mg. In the reported data, gradual escalation to the same maintenance dose produced fewer gastrointestinal events than jumping straight to it. These are reference figures for research context only, not human dosing guidance.
How does retatrutide differ from tirzepatide?
Tirzepatide is a dual GLP-1/GIP agonist, while retatrutide adds a third arm — glucagon-receptor agonism. In the reported obesity models this triple mechanism is associated with larger mean body-weight reductions at the higher doses. Retatrutide is earlier in the clinical pipeline and less extensively characterized than tirzepatide.
Is retatrutide an approved drug?
No — as of the current literature retatrutide is an investigational compound still in clinical trials (including the phase 3 TRIUMPH program) and is not an approved medicine. It should be handled strictly as a research chemical, not for human use.
What documentation should be expected for research-grade retatrutide?
Because it is a complex acylated peptide, a third-party COA with HPLC purity (commonly greater than or equal to 98%) and mass-spec identity confirmation is the standard reference to expect. Lyophilized material is stored cold and reconstituted with bacteriostatic water for research handling; freeze-thaw cycles and light exposure are avoided.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.