Retatrutide
The first-in-class triple receptor agonist demonstrating up to 24.2% weight loss in Phase 2 trials. Currently in Phase 3 development by Eli Lilly. Not yet approved for any use.
22 min read · Last updated March 2026 · 24 research citations
INVESTIGATIONAL COMPOUND - NOT FDA APPROVED
Retatrutide is an investigational peptide in Phase 3 clinical trials. It has NOT been approved by the FDA or any regulatory agency. It is not available for prescription or purchase. All information is for educational purposes only.
Key Takeaways
Overview
What is Retatrutide?
Retatrutide (LY3437943) is an investigational peptide being developed by Eli Lilly and Company for the treatment of obesity and type 2 diabetes. It represents a novel class of therapeutic peptides called triple hormone receptor agonists or "triagonists."
Unlike semaglutide (Ozempic, Wegovy) which targets only GLP-1 receptors, or tirzepatide (Mounjaro, Zepbound) which targets GLP-1 and GIP, retatrutide simultaneously activates three distinct metabolic hormone receptors:
GLP-1 Receptor
Appetite suppression, insulin secretion, gastric slowing
GIP Receptor
Insulin sensitivity, lipid metabolism, beta cell health
Glucagon Receptor
Energy expenditure, liver fat oxidation, thermogenesis
Development Timeline
Innovation
Why Triple Agonist Matters
Single Agonists
GLP-1 only (Semaglutide)
- • ~15-17% weight loss max
- • Appetite suppression primary
- • Weight loss plateaus common
Dual Agonists
GLP-1 + GIP (Tirzepatide)
- • ~20-22% weight loss max
- • Enhanced insulin sensitivity
- • Improved lipid handling
Triple Agonist
GLP-1 + GIP + Glucagon (Retatrutide)
- • ~24% weight loss (Phase 2)
- • Added energy expenditure
- • Superior liver fat reduction
- • May prevent metabolic plateau
Chemistry
Molecular Structure
Receptor Binding Profile
| Receptor | Activity | Primary Contribution |
|---|---|---|
| GLP-1 | High | Appetite reduction, insulin secretion |
| GIP | High | Insulin sensitization, lipid metabolism |
| Glucagon | Moderate | Energy expenditure, hepatic fat oxidation |
The moderate glucagon activity is intentional - sufficient to enhance energy expenditure while avoiding excessive glucose elevation (balanced by GLP-1 and GIP effects).
Mechanism
How Retatrutide Works
Triple agonism creates a coordinated metabolic response that addresses multiple pathways simultaneously.
Reduced Energy Intake
GLP-1 and GIP act on brain satiety centers to reduce hunger and food cravings
Increased Energy Expenditure
Glucagon boosts resting metabolic rate and hepatic substrate cycling
Improved Glucose Handling
All three receptors contribute to better insulin secretion and sensitivity
Enhanced Fat Oxidation
Glucagon drives hepatic fat burning, dramatically reducing liver fat
Preserved Metabolic Rate
Glucagon may prevent the metabolic adaptation that causes weight loss plateaus
Better Body Composition
Combination may promote preferential fat loss while preserving lean mass
Evidence
Clinical Trial Research
Phase 2 results published in the New England Journal of Medicine, June 2023
Phase 2 Trial Results (48 Weeks)
n=338| Dose Group | 24 Weeks | 48 Weeks |
|---|---|---|
| Placebo | -2.1% | -2.1% |
| 1 mg | -7.2% | -8.7% |
| 4 mg | -12.9% | -17.1% |
| 8 mg | -17.3% | -22.8% |
| 12 mg | -17.5% | -24.2% |
Response Rates at 12 mg Dose
Efficacy
Weight Loss Efficacy
Comparison to Bariatric Surgery
Note: Weight loss trajectory at 48 weeks had not yet plateaued, suggesting longer treatment may produce even greater results.
Comparison
Retatrutide vs Approved Medications
| Characteristic | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Developer | Novo Nordisk | Eli Lilly | Eli Lilly |
| Receptor Targets | GLP-1 only | GLP-1 + GIP | GLP-1 + GIP + Glucagon |
| FDA Status | Approved | Approved | Investigational |
| Max Weight Loss | ~17% | ~22% | ~24% (Ph2) |
| Liver Fat Reduction | 30-40% | 50-60% | >80% |
| Dosing | Weekly | Weekly | Weekly |
* Retatrutide data is from Phase 2 trials and requires Phase 3 confirmation. Cross-trial comparisons have limitations.
Safety
Side Effects from Trials
Common Side Effects (Phase 2)
Most GI side effects occurred during dose escalation and improved over time.
Notable Observations
Mean increase of 10-15 bpm at higher doses (likely glucagon-related). Clinical significance being evaluated.
4-6% discontinued due to adverse events (similar to tirzepatide).
Theoretical risks of thyroid C-cell tumors, pancreatitis, and gallbladder disease apply.
Timeline
When Will Retatrutide Be Available?
TRIUMPH program trials report initial results
If Phase 3 results are positive
Timeline depends on trial results and regulatory review
IMPORTANT: Not Currently Available
Retatrutide is ONLY available through clinical trial participation. Any product marketed as retatrutide for sale outside of clinical trials is not legitimate and may be dangerous. Do not purchase from unregulated sources.
FAQ
Frequently Asked Questions
References
- Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity - a phase 2 trial. N Engl J Med. 2023;389(6):514-526.
- Rosenstock J, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes. Lancet. 2023;402(10401):529-544.
- Coskun T, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist. Cell Metab. 2022;34(9):1234-1247.
- Eli Lilly and Company. Lilly's retatrutide delivered up to 24.2% body weight loss. Press release. June 26, 2023.
- Nauck MA, et al. GLP-1 receptor agonists in the treatment of type 2 diabetes. Mol Metab. 2021;46:101102.
- Finan B, et al. Reappraisal of GIP pharmacology for metabolic diseases. Trends Mol Med. 2016;22(5):359-376.
- Habegger KM, et al. The metabolic actions of glucagon revisited. Nat Rev Endocrinol. 2010;6(12):689-697.
- Finan B, et al. A rationally designed monomeric peptide triagonist corrects obesity and diabetes in rodents. Nat Med. 2015;21(1):27-36.
Important Disclaimer: Retatrutide is an investigational compound that has NOT been approved by the FDA or any regulatory agency. It is not available for prescription or purchase. All information presented is for educational purposes only. Do not attempt to obtain this compound outside of clinical trials.
Last updated: March 2026 · Reviewed by: Scientific Aminos Editorial Board
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