Retatrutide is an investigational compound under clinical development. It is not approved by Health Canada or the FDA for therapeutic use. All information on this page is provided for educational and research purposes only. Do not use this information as medical advice.
Overview
What Is Retatrutide?
Retatrutide (also known by its development designation LY3437943) is an investigational peptide developed by Eli Lilly and Company. It is classified as a triple incretin receptor agonist — meaning it is designed to simultaneously activate three distinct hormone receptors: the glucagon-like peptide-1 (GLP-1) receptor, the glucose-dependent insulinotropic polypeptide (GIP) receptor, and the glucagon receptor.
This triple-agonist mechanism distinguishes Retatrutide from earlier-generation compounds. Semaglutide (Ozempic/Wegovy) acts on the GLP-1 receptor alone; Tirzepatide (Mounjaro) acts on both GLP-1 and GIP receptors. Retatrutide adds glucagon receptor agonism to this combination — a mechanistic addition that appears, based on Phase 2 clinical data, to produce substantially greater weight reduction than dual-agonist compounds.
As of 2025, Retatrutide is advancing through clinical development and is the subject of significant research interest among investigators studying metabolic dysfunction, obesity, and related cardiometabolic conditions.
Pharmacology
Mechanism of Action
Understanding Retatrutide's mechanism requires understanding the three receptor systems it engages:
GLP-1 Receptor Agonism
GLP-1 (glucagon-like peptide-1) is an incretin hormone secreted by intestinal L-cells in response to food intake. GLP-1 receptor agonists produce several metabolic effects: they stimulate glucose-dependent insulin secretion, suppress glucagon release, slow gastric emptying, and act centrally to reduce appetite and food intake. These effects contribute meaningfully to both glycaemic control and body weight reduction.
GIP Receptor Agonism
GIP (glucose-dependent insulinotropic polypeptide) is another incretin hormone, secreted from intestinal K-cells. GIP receptor agonism amplifies insulin secretion in a glucose-dependent manner and also appears to have direct effects on adipose tissue and central appetite regulation. The addition of GIP agonism to GLP-1 agonism — as demonstrated with Tirzepatide — meaningfully increases the magnitude of weight loss observed in clinical trials.
Glucagon Receptor Agonism
Glucagon receptor agonism is the defining addition of Retatrutide relative to its predecessors. While glucagon is typically associated with raising blood glucose (counter-regulatory to insulin), glucagon also stimulates hepatic lipid oxidation, increases energy expenditure, and acts centrally to suppress appetite. In the context of triple agonism, glucagon receptor activation appears to contribute to greater lipolysis and thermogenesis, while the GLP-1 component counterbalances the hyperglycaemic effects.
GLP-1: ↓ appetite, ↑ insulin secretion, ↓ glucagon, slows gastric emptying
GIP: ↑ insulin secretion, direct adipose effects, ↓ appetite
Glucagon: ↑ hepatic lipid oxidation, ↑ energy expenditure, ↓ appetite centrally
Clinical Evidence
Phase 2 Clinical Trial Data
The primary clinical evidence for Retatrutide's efficacy in humans comes from a Phase 2 randomised controlled trial published in the New England Journal of Medicine (NEJM) in 2023. The study enrolled 338 adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related comorbidity, and evaluated multiple doses of Retatrutide versus placebo over 24 and 48 weeks.
Study Design
- Population: Adults with obesity or overweight with comorbidity
- Arms: Multiple Retatrutide dose groups (1 mg, 4 mg, 8 mg, 12 mg) vs. placebo
- Duration: 48 weeks of treatment
- Primary endpoint: Percent change in body weight from baseline
- Design: Double-blind, randomised, placebo-controlled
The results, particularly at the higher dose levels, were notable for producing weight-loss magnitudes that exceeded those observed in previous trials of GLP-1 and dual GLP-1/GIP agonists.
Key Data
Weight-Loss Results Table
The following table summarises the mean percent change in body weight from baseline reported across dose groups in the Phase 2 trial. Higher Retatrutide doses showed progressively greater weight reduction, with the 12 mg dose achieving results that have not previously been observed with approved pharmacological agents.
| Timepoint | Placebo | Retatrutide 1 mg | Retatrutide 4 mg | Retatrutide 8 mg | Retatrutide 12 mg |
|---|---|---|---|---|---|
| Week 4 | −0.4% | −1.6% | −3.1% | −4.2% | −4.9% |
| Week 8 | −0.7% | −2.3% | −5.2% | −6.8% | −7.8% |
| Week 12 | −1.2% | −2.8% | −7.0% | −9.5% | −11.2% |
| Week 24 | −1.6% | −3.5% | −10.4% | −14.4% | −17.3% |
| Week 48 | −2.1% | −4.2% | −13.0% | −19.2% | −24.2% |
Data adapted from Phase 2 clinical trial results. Values represent approximate mean percent change from baseline body weight. Individual responses vary. Study conducted in adults with obesity or overweight; results should not be extrapolated to all populations.
At the highest dose (12 mg), participants achieved approximately 24% mean body weight reduction over 48 weeks — a magnitude that exceeds previously reported results from approved GLP-1 and dual GLP-1/GIP agents in comparable trial designs.
Secondary Outcomes
Beyond primary weight endpoints, the Phase 2 trial also reported improvements in cardiometabolic markers at higher dose levels, including:
- Reduction in waist circumference
- Improvements in fasting blood glucose
- Reductions in systolic blood pressure
- Favourable changes in lipid profiles
Tolerability
The most common adverse events reported were gastrointestinal in nature — nausea, vomiting, and diarrhoea — consistent with the GLP-1 agonist class. These were generally more pronounced with dose escalation and in early treatment phases. Discontinuation rates due to adverse events were higher at higher dose levels, as is typical for this class of compounds.
Scientific Context
Research Context
Retatrutide represents a significant point of interest in metabolic research because its Phase 2 results suggest that adding glucagon receptor agonism to dual GLP-1/GIP agonism may produce substantially greater weight reduction than dual agonism alone. This raises important mechanistic questions about the additive or synergistic contributions of each receptor pathway to total body weight regulation.
The compound is also being studied for its potential effects on non-alcoholic fatty liver disease (NAFLD/NASH), metabolic dysfunction-associated liver disease, and its cardiovascular implications — research areas where the broader incretin class has shown considerable promise.
Phase 3 trials examining Retatrutide across multiple metabolic indications are ongoing or in planning as of mid-2025. Researchers studying incretin pharmacology, adipose biology, energy homeostasis, and related areas have a legitimate scientific interest in understanding this compound's mechanisms in preclinical and translational contexts.
Research Sourcing
Sourcing Retatrutide in Canada for Research
For researchers seeking research-grade Retatrutide within Canada, domestic sourcing offers practical advantages over international alternatives — primarily the elimination of customs risk and faster, temperature-controlled delivery.
NextEdge Peptides, our top-rated Canadian supplier, offers Retatrutide in its catalogue with the same quality documentation standards applied to its other products: third-party laboratory testing, publicly accessible Certificates of Analysis, and per-vial lot numbers for full traceability.
When sourcing any research peptide, including Retatrutide, it is important to verify that your supplier provides batch-specific analytical documentation. The COA should be from an independent laboratory and traceable to the specific lot number on the received vial.
See our full NextEdge Peptides review for a detailed assessment of their documentation practices and ordering process.
Academic Sources
References & Further Reading
The following published studies and resources are relevant to Retatrutide research:
- Jastreboff AM, et al. (2023). "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial." New England Journal of Medicine. nejm.org/doi/full/10.1056/NEJMoa2301972
- Rosenstock J, et al. (2023). "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial." The Lancet. thelancet.com
- Finan B, et al. (2015). "Unimolecular Dual Incretins Maximize Metabolic Benefits in Rodents, Monkeys, and Humans." Science Translational Medicine. (Foundational research on multi-agonist peptide pharmacology)
- ClinicalTrials.gov — Search "Retatrutide" for current and completed studies: clinicaltrials.gov/search?term=retatrutide
- PubMed — Peer-reviewed literature on incretin receptor agonists: pubmed.ncbi.nlm.nih.gov