Retatrutide (LY3437943) is an investigational triple hormone receptor agonist developed by Eli Lilly and Company. It represents the next generation of incretin-based therapies, simultaneously targeting three key metabolic receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon receptors.
This "triple G" approach distinguishes retatrutide from dual agonists like tirzepatide (Mounjaro/Zepbound), potentially offering enhanced metabolic benefits through the additional glucagon receptor activation, which may increase energy expenditure and promote fat oxidation.
In Phase 2 clinical trials, retatrutide demonstrated unprecedented weight loss results, with participants achieving up to 24.2% body weight reduction at 48 weeks - surpassing outcomes observed with existing GLP-1 and dual agonist therapies.
Slows gastric emptying, reduces appetite, enhances insulin secretion in a glucose-dependent manner, and promotes satiety through central nervous system signaling.
Potentiates insulin secretion, may improve lipid metabolism, and works synergistically with GLP-1 to enhance glycemic control and weight management.
Increases hepatic glucose production acutely but chronically promotes energy expenditure, fat oxidation, and may contribute to appetite suppression.
| Trial | Phase | Population | Key Finding |
|---|---|---|---|
| LY3437943 Phase 2 Obesity | Phase 2 | 338 adults with obesity | Up to 24.2% weight loss at 48 weeks (12mg dose) |
| LY3437943 Phase 2 T2D | Phase 2 | 281 adults with T2D | HbA1c reduction up to 2.2%; 16.9% weight loss |
| TRIUMPH-1 | Phase 3 | Adults with obesity | Ongoing - primary endpoint: % weight change |
| TRIUMPH-2 | Phase 3 | T2D with obesity | Ongoing - evaluating glycemic and weight outcomes |
| TRIUMPH-3 (MASH) | Phase 3 | MASH with fibrosis | Ongoing - liver histology endpoints |
The Phase 2 obesity trial demonstrated dose-dependent weight reductions that exceeded all previously approved anti-obesity medications. At the highest dose (12mg weekly), participants achieved a mean weight loss of 24.2% at 48 weeks, with some individuals losing over 30% of their body weight.
For context, semaglutide (Wegovy) typically achieves approximately 15-17% weight loss, while tirzepatide (Zepbound) achieves approximately 20-22% weight loss. Retatrutide's 24.2% result suggests the additional glucagon receptor activity may provide incremental metabolic benefits.
Primary indication with unprecedented weight loss efficacy in clinical trials.
Significant HbA1c reductions with concurrent weight loss benefits.
Liver fat reduction suggests potential for metabolic liver disease treatment.
Comprehensive metabolic improvements across multiple parameters.
Most adverse events were mild to moderate in severity and decreased over time as participants adjusted to treatment.
Nausea, diarrhea, vomiting, and constipation were the most common adverse events, consistent with GLP-1 receptor agonist class effects.
Higher doses were associated with more frequent GI side effects, particularly during the dose-escalation period.
Long-term safety data from Phase 3 trials will be essential for full characterization of the benefit-risk profile.
Retatrutide is an investigational compound that has not been approved by the FDA or any other regulatory agency. The information presented here is for educational and research purposes only. All clinical data referenced is from published peer-reviewed research and official Eli Lilly communications. This compound is not intended for human use outside of approved clinical trials. Always consult qualified healthcare professionals and refer to official clinical trial registries for the most current information.
Phase 3 trials are currently ongoing as part of the TRIUMPH clinical development program. Eli Lilly is conducting multiple large-scale studies across different patient populations:
Based on current timelines, Eli Lilly could potentially submit regulatory applications in 2025, with possible FDA approval in 2025-2026 if Phase 3 results are favorable. The compound has received significant attention from the medical community given its unprecedented Phase 2 efficacy data.
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