Retatrutide Research
Retatrutide, also known as LY3437943, is an investigational peptide drug from Eli Lilly. It is not FDA-approved yet. It is being studied mainly for obesity, type 2 diabetes, fatty liver disease/MASLD-MASH, sleep apnea, osteoarthritis pain, and cardiometabolic risk.
Its main feature is that it activates three metabolic hormone receptors:
| Receptor | Main Research Role |
|---|---|
| GLP-1 | Appetite reduction, slower gastric emptying, improved insulin signaling |
| GIP | Insulin support, metabolic regulation, fat-cell signaling |
| Glucagon | Increased energy expenditure, liver fat metabolism, possible greater weight-loss effect |
This makes Retatrutide a triple hormone receptor agonist, different from semaglutide, which is GLP-1 only, and tirzepatide, which is GLP-1 + GIP. (New England Journal of Medicine)
Key Human Trial Results
1. Obesity — Phase 2 Trial
A 2023 New England Journal of Medicine phase 2 study tested Retatrutide in adults with obesity or overweight plus at least one weight-related condition. At higher doses, Retatrutide produced very large body-weight reductions over 48 weeks. The 12 mg group reached roughly 24% average body-weight loss in the phase 2 trial. (New England Journal of Medicine)
2. Obesity — Phase 3 TRIUMPH-1
In May 2026, Lilly reported topline phase 3 TRIUMPH-1 data. Participants on 12 mg retatrutide lost an average of 70.3 lb, or 28.3% body weight, over 80 weeks. 45.3% achieved at least 30% weight loss. In a higher-BMI extension group, average weight loss reached 85 lb, or 30.3%, at 104 weeks. (Eli Lilly and Company)
At the 4 mg dose, participants lost an average of 47.2 lb, or 19.0%, at 80 weeks. Lilly stated that discontinuation from adverse events at this dose was lower than placebo in observed data. (Eli Lilly and Company)
3. Type 2 Diabetes
In June 2026, Lilly reported phase 3 TRANSCEND-T2D-1 results. Retatrutide produced A1C reductions up to 2.0% and weight loss up to 36.6 lb, or 16.8%, at 40 weeks. Up to 46% of participants achieved normal A1C. (Eli Lilly and Company)
4. Fatty Liver Disease / MASLD
A phase 2a study in Nature Medicine evaluated Retatrutide in metabolic dysfunction-associated steatotic liver disease. The study supports interest in Retatrutide for reducing liver fat and improving metabolic liver markers, likely due to combined weight loss, glucagon receptor activity, and improved insulin sensitivity. (PubMed)
Safety Signals
The main side effects reported are similar to GLP-1/GIP drugs:
| Side Effect Category | Examples |
|---|---|
| Gastrointestinal | Nausea, vomiting, diarrhea, constipation |
| Appetite/weight-related | Reduced appetite, rapid weight loss |
| Sensory | Dysesthesia/abnormal skin sensations reported in trials |
| Cardiometabolic monitoring | Heart rate, blood pressure, glucose, lipids |
| Gallbladder/pancreas caution | Class-related concern with rapid weight loss and incretin drugs |
Lilly’s 2026 phase 3 release described the safety profile as generally consistent with incretin-based therapies, with GI events being the most common. (Eli Lilly and Company)
Why Retatrutide Is Important
Retatrutide may become one of the strongest obesity drugs studied so far because it targets:
- Appetite control
- Insulin and glucose regulation
- Energy expenditure
- Liver fat metabolism
- Weight-related complications
Its reported 28–30% average weight-loss range approaches outcomes historically associated with bariatric surgery, though surgery and medication are not directly interchangeable. (Eli Lilly and Company)
Research Classification
For catalog or product organization, retatrutide would fit under:
Metabolic Research Peptide / Triple Incretin Receptor Agonist
Better category wording:
Metabolic Research Peptides
More specific:
GLP-1 / GIP / Glucagon Receptor Agonist Research Compound
Clean Research Description
Retatrutide is an investigational triple hormone receptor agonist studied for metabolic research applications. It activates GLP-1, GIP, and glucagon receptors, making it distinct from single- or dual-incretin compounds. Current research focuses on obesity, body-weight regulation, glucose metabolism, insulin sensitivity, liver fat reduction, and cardiometabolic risk markers. Clinical trials have shown substantial weight-loss and metabolic effects, with gastrointestinal events being the most common safety findings. Retatrutide remains investigational and is intended for controlled research use only.