Retatrutide
Also known as: LY3437943, Reta
Investigational Compound. This compound is currently in clinical development and has not received regulatory approval. No established commercial regimen exists. Consult a qualified clinician for the latest information on clinical trial availability.
Overview
Clinical Summary
Retatrutide is a triple agonist targeting GLP-1, GIP, and glucagon receptors. It represents a next-generation incretin-based therapy currently in Phase 3 clinical development by Eli Lilly. In Phase 2 trials, participants achieved mean body weight reductions of up to 24.2% at 48 weeks, surpassing results observed with dual agonists. The glucagon receptor component may provide additional metabolic benefits including improved hepatic lipid metabolism.
Plain Language Summary
Retatrutide is an investigational weight loss medication that works on three different hormone pathways at once. In clinical trials, people lost an average of about 24% of their body weight over 48 weeks, which is more than currently available medications achieve. It is still being studied and has not yet been approved by the FDA.
Mechanism of Action
Retatrutide is a single-molecule triple agonist that simultaneously activates three receptors: GLP-1R (glucagon-like peptide-1 receptor), GIPR (glucose-dependent insulinotropic polypeptide receptor), and GCGR (glucagon receptor). GLP-1R activation reduces appetite, slows gastric emptying, and enhances glucose-dependent insulin secretion. GIPR activation complements GLP-1R effects on insulin secretion and may improve lipid metabolism. GCGR activation increases energy expenditure, promotes hepatic lipid oxidation, and may reduce hepatic steatosis. The triagonist approach aims to leverage synergistic metabolic effects beyond what dual agonism provides.
Evidence Summary
The TRIUMPH Phase 2 trial (Jastreboff et al., NEJM 2023) enrolled 338 adults with obesity. At 48 weeks, participants receiving the highest dose (12 mg) achieved a mean weight reduction of 24.2% vs. 2.1% for placebo. Secondary endpoints showed improvements in waist circumference, blood pressure, fasting glucose, HbA1c, and lipid parameters. Phase 3 trials are ongoing across multiple indications including obesity and type 2 diabetes. No Phase 3 efficacy data have been published as of the last review date.
Safety Profile
The safety profile in Phase 2 was broadly consistent with the GLP-1RA class. Gastrointestinal adverse events (nausea, diarrhea, vomiting, constipation) were the most common and generally mild to moderate. Dose-dependent increases in heart rate were observed. No pancreatitis or medullary thyroid carcinoma cases were reported in Phase 2, though the glucagon component warrants ongoing hepatic and cardiovascular monitoring. Long-term safety data are not yet available.
Contraindications
- Personal or family history of medullary thyroid carcinoma
- Multiple endocrine neoplasia type 2
- Known hypersensitivity to the active substance
- Pregnancy and breastfeeding (insufficient safety data)
Adverse Events
- Nausea (most common, dose-dependent)
- Diarrhea
- Vomiting
- Constipation
- Decreased appetite
- Injection site reactions
- Increased heart rate
Interactions
- May delay absorption of oral medications due to gastric slowing
- Caution with insulin or sulfonylureas (hypoglycemia risk)
- No formal drug interaction studies completed
Active Safety Signals
Retatrutide is not approved for commercial sale. Grey-market versions are not manufactured under GMP conditions and may contain incorrect quantities, impurities, or degradation products. No regulatory oversight of these products exists.
Regulatory Notes
Retatrutide is currently in Phase 3 clinical development under Eli Lilly. It has not received FDA or EMA approval. It does not have breakthrough therapy designation at this time. Versions of this compound circulate in the grey market, but these are not manufactured under GMP conditions and carry significant quality and purity risks.
Monitoring Considerations
Clinicians may consider monitoring hepatic function given the glucagon receptor component. Standard metabolic panel, HbA1c, lipid panel, and heart rate should be assessed. GI tolerability should be evaluated during dose escalation. Thyroid monitoring should be considered given the GLP-1RA class labeling.
These are general considerations for clinical awareness and do not constitute prescriptive monitoring recommendations for any individual patient.
Stability and Handling Notes
Investigational product. Stability data are not publicly available. Grey-market versions lack standardized stability testing.
References
- 1RCT
Triple-Hormone-Receptor Agonist Retatrutide for Obesity
Jastreboff AM, Kaplan LM, Frias JP, et al. (2023). New England Journal of Medicine
Key findings: Phase 2 RCT in 338 adults with obesity. Mean body weight reduction of 24.2% at 48 weeks with 12 mg dose vs 2.1% placebo. Improvements in cardiometabolic parameters.
Limitations: Phase 2 study with limited sample size. 48-week duration. Predominantly White participants. No long-term safety data.
View source - 2RCT
Retatrutide Phase 2 Trial in Type 2 Diabetes
Rosenstock J, Frias JP, Jastreboff AM, et al. (2023). New England Journal of Medicine
Key findings: Phase 2 trial in adults with T2D. HbA1c reduction up to 2.02% and weight loss up to 16.9% at 36 weeks.
Limitations: Phase 2, moderate sample size. Patients on metformin background therapy only.
View source - 3review
GLP-1/GIP/Glucagon Receptor Triple Agonism: Retatrutide Clinical Development
Urva S, Coskun T, Loh MT, et al. (2024). Cell Metabolism
Key findings: Review of retatrutide pharmacology and clinical data. Discusses the rationale for triple agonism and the contribution of each receptor pathway.
Limitations: Narrative review with authors affiliated with Eli Lilly.
Last reviewed: 2024-12-15 | Version: 1 | Status: Published