Retatrutide
unknown riskAlso: LY3437943 · Triple agonist
Retatrutide is Eli Lilly's triple receptor agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Phase 2 data showed up to 24.2% body weight reduction — among the highest pharmacological weight loss efficacy ever recorded.
Reported Benefits
Weight Loss
Phase 2: 24.2% body weight reduction at highest dose over 48 weeks.
Glycemic Control
Phase 2 data shows robust HbA1c reduction in T2DM subjects.
Lipid Improvement
Significant improvement in triglycerides and liver fat.
Mechanism of Action
Retatrutide activates three receptors simultaneously: GLP-1 receptor (appetite suppression, insulin secretion), GIP receptor (insulin sensitivity, adipose remodeling), and glucagon receptor (hepatic glucose output, thermogenesis, lipolysis). The glucagon component is unique — glucagon receptor agonism increases energy expenditure and hepatic fat mobilization.
Key Clinical Studies
Jastreboff AM et al. (2023)
Phase 2 RCT · 338 adults with obesity
24.2% weight loss at 12mg dose over 48 weeks
Overview
Retatrutide (LY3437943) is Eli Lilly’s attempt to achieve the maximum pharmacological weight loss efficacy possible from incretin pathway agonism. By adding glucagon receptor agonism to the dual GIP/GLP-1 mechanism of tirzepatide, it achieves a triple-receptor mechanism with additive metabolic effects.
The Glucagon Paradox
Conventionally, glucagon is considered “bad” for diabetes — it raises blood sugar. However, glucagon receptor activation also increases thermogenesis (energy expenditure) and promotes hepatic fat oxidation. In the context of a GLP-1 co-agonist that controls insulin secretion, selective glucagon receptor stimulation becomes net beneficial — a counterintuitive pharmacological insight.
Phase 2 Landmark Data
The Phase 2 data published in NEJM (2023) showed 24.2% body weight reduction at 12mg — a result that, if replicated in Phase 3, would set a new record for pharmacological weight loss. Phase 3 TRIUMPH trials are ongoing.
Safety Considerations
The glucagon component raises theoretical concerns about cardiovascular effects (glucagon increases heart rate and may affect cardiac function) that require careful Phase 3 monitoring. The triple mechanism also raises questions about hypoglycemia risk in diabetic patients.
Regulatory Status
Research OnlyPhase 3 clinical trials active; FDA Fast Track designation; no approval as of 2025
Safety Profile
Side Effects
- •Nausea
- •Diarrhea
- •Vomiting
- •Decreased appetite
- •Potential elevated heart rate
Contraindications
- •History of MTC or MEN2
- •Pregnancy
- •Active pancreatitis
Drug Interactions
- •Insulin
- •Oral hypoglycemics
Primary Uses
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Weekly Briefing
Regulatory updates + new study breakdowns.
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