Maple Research overview of retatrutide (LY3437943), a triple GIP/GLP-1/glucagon receptor agonist representing the next generation of multi-agonist incretin pharmacology. Covers tri-agonist mechanism, glucagon receptor contribution, phase 2 data, and comparison with dual agonists.
Molecular Profile
| Generic Name | Retatrutide (LY3437943) |
|---|---|
| Peptide Length | 39 amino acids |
| CAS Number | 2381089-83-2 |
| Classification | Triple GIP/GLP-1/glucagon receptor agonist |
| Structure Basis | Engineered from GIP sequence (similar backbone to tirzepatide) |
| Modification | C20 fatty acid moiety for albumin binding; glucagon receptor agonist activity engineered into sequence |
| Half-Life | ~6 days (once-weekly dosing) |
| Regulatory Status | Phase 3 clinical trials (as of 2024-2025) |
| Developer | Eli Lilly and Company |
Triple Agonism: The Mechanistic Rationale
Retatrutide extends the dual agonist approach of tirzepatide by adding glucagon receptor (GCGR) agonism as a third pharmacological axis. Each receptor contributes distinct metabolic effects:
Melson et al. (2024) positioned retatrutide within the broader pipeline of entero-pancreatic hormone-based obesity treatments, noting that the triple agonist approach has produced the largest weight reductions observed in obesity pharmacotherapy trials to date (DOI: 10.1038/s41366-024-01473-y).
The Glucagon Paradox
Adding glucagon receptor agonism to an anti-diabetic/anti-obesity agent appears counterintuitive, since glucagon raises blood glucose by stimulating hepatic glucose output. The resolution lies in the context of simultaneous GIP and GLP-1 receptor agonism: the incretin components provide sufficient insulin secretory drive and glucose-dependent insulin sensitization to offset glucagon’s glycemic effects, while the glucagon component’s energy expenditure and lipolytic actions are preserved.
This is analogous to how oxyntomodulin (a natural peptide with both GLP-1 and glucagon receptor activity) promotes weight loss in research settings without causing hyperglycemia, because the GLP-1 component dominates glycemic control while the glucagon component drives thermogenesis (Hong & Choi, 2024; DOI: 10.1097/MED.0000000000000859).
Phase 2 Clinical Data
The phase 2 trial of retatrutide in adults with obesity demonstrated dose-dependent weight reductions of up to 24.2% at 48 weeks at the highest dose (12 mg), exceeding weight loss observed with tirzepatide (~22.5%) and semaglutide (~15-17%) in their respective obesity trials. Approximately 26% of participants lost more than 30% of body weight. The adverse event profile was similar to other incretin-based agents (nausea, diarrhea, constipation), with dose-dependent gastrointestinal effects.
Comparison: Evolution of Incretin Agonists
| Parameter | Semaglutide (GLP-1 only) | Tirzepatide (GIP + GLP-1) | Retatrutide (GIP + GLP-1 + GCGR) |
|---|---|---|---|
| Receptor Count | 1 (selective) | 2 (dual) | 3 (triple) |
| Primary Weight Loss Mechanism | Appetite suppression, gastric slowing | Appetite suppression + adipose remodeling | Appetite suppression + adipose remodeling + energy expenditure |
| Glucagon Receptor | No activity | No activity | Agonist (drives thermogenesis) |
| Max Weight Loss (Trials) | ~15-17% | ~22.5% | ~24.2% (Phase 2) |
| Lean Mass Concern | ~10% of weight lost | ~10% of weight lost | Under investigation |
| Approval Status | FDA approved | FDA approved | Phase 3 |
| Available at MRL | No | Yes | Yes |
Research Product Specifications
Maple Research Labs – Retatrutide 10MG
Purity verified via third-party HPLC and mass spectrometry
Lyophilized, research-grade
Key Research Citations
| Citation | Focus | DOI |
|---|---|---|
| Melson et al., 2024 | Pipeline of obesity pharmacotherapies incl. retatrutide | 10.1038/s41366-024-01473-y |
| Hong & Choi, 2024 | Gut hormones and appetite regulation | 10.1097/MED.0000000000000859 |
| Locatelli et al., 2024 | Lean mass loss with incretin therapy | 10.2337/dci23-0100 |
| Willard et al., 2020 | Imbalanced dual agonism (tirzepatide, shared mechanism) | 10.1172/jci.insight.140532 |
Related Research Pages
GLP-1 & Incretin Pathway Overview | Broader incretin biology context
Tirzepatide (Dual GIP/GLP-1) | The dual agonist predecessor
Frequently Asked Questions
What is retatrutide and how does it differ from tirzepatide?
Retatrutide (LY3437943) is a triple agonist that activates three receptors: GIP, GLP-1, and glucagon. Tirzepatide is a dual agonist that activates only GIP and GLP-1. The key difference is the addition of glucagon receptor agonism in retatrutide, which is hypothesized to increase energy expenditure through hepatic fatty acid oxidation and thermogenesis. Both share a GIP peptide backbone and biased GLP-1 receptor signaling. Phase 2 data suggests the glucagon component may drive additional weight reduction beyond what dual agonism achieves.
Why does adding glucagon receptor agonism not cause hyperglycemia?
While glucagon promotes hepatic glucose output, the simultaneous GIP and GLP-1 receptor agonism provides sufficient insulin secretory drive and glucose-dependent insulin sensitization to offset the glycemic effects. This balance allows the energy expenditure and lipolytic benefits of glucagon receptor activation to be captured without compromising glucose control. The concept is supported by research on oxyntomodulin, a natural peptide with dual GLP-1/glucagon activity that promotes weight loss without hyperglycemia.
Where can I buy retatrutide for research in Canada?
Maple Research Labs supplies retatrutide as a research-grade reagent within Canada, with third-party purity verification via HPLC and mass spectrometry. All products include batch-specific Certificates of Analysis and ship same-day from Canadian facilities. Retatrutide is supplied exclusively for in-vitro and preclinical research, not for human consumption or therapeutic use.
Is retatrutide FDA approved?
As of 2025, retatrutide is not yet FDA approved. It is currently in phase 3 clinical trials for both type 2 diabetes and obesity. The phase 2 trial showed promising efficacy with weight reductions of up to 24.2% at 48 weeks. Phase 3 results are expected to determine whether the efficacy and safety profile supports regulatory approval.