RETATRUTIDE

Retatrutide, also known as LY3437943, is an investigational once-weekly peptide designed to activate three hormone receptors involved in metabolic regulation: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon. This combination gives retatrutide a distinct mechanism from currently available single- and dual-receptor metabolic therapies.

How does Retatrutide work?

Retatrutide simultaneously activates the GIP, GLP-1, and glucagon receptors. GIP and GLP-1 signaling can influence appetite, glucose-dependent insulin secretion, and energy intake, while glucagon receptor activation is associated with increased energy expenditure and changes in substrate utilization. By combining these three pathways in a single molecule, retatrutide is being investigated for its potential to produce substantial changes in body weight and metabolic health.

How is Retatrutide Used?

Retatrutide is currently being investigated in clinical trials as a once-weekly subcutaneous treatment. Phase 2 research evaluated several dose levels in adults with obesity or overweight accompanied by a weight-related condition. More recent Phase 3 studies have expanded investigation into obesity, type 2 diabetes, cardiovascular disease, obstructive sleep apnea, knee osteoarthritis, and other metabolic conditions.

Benefits:

Weight-Loss Research: Retatrutide has demonstrated substantial reductions in body weight in clinical trials. In the Phase 2 obesity study, participants receiving the highest studied dose experienced an average weight reduction of 24.2% after 48 weeks, compared with 2.1% with placebo.

Appetite & Metabolic Regulation: Through simultaneous GIP, GLP-1, and glucagon receptor activation, retatrutide is being investigated for its effects on appetite regulation, energy intake, energy expenditure, and metabolic signaling.

Glucose Control: Clinical research has demonstrated improvements in fasting glucose, insulin, and glycated hemoglobin alongside weight reduction. In the Phase 2 study, metabolic improvements were observed across several retatrutide treatment groups.

Body Composition: Research has examined retatrutide’s effects on body weight, waist circumference, and other measures of body composition. Ongoing Phase 3 studies are providing additional information about its longer-term effects.

Cardiometabolic Research: Retatrutide is being investigated beyond weight reduction, including its potential effects on cardiometabolic risk factors and complications associated with obesity. Recent Phase 3 studies have evaluated populations with type 2 diabetes and established cardiovascular disease.

Research Considerations:

Retatrutide remains an investigational medication and has not yet received FDA approval. Although clinical evidence has progressed substantially, its safety and effectiveness are still being evaluated through ongoing Phase 3 studies. Lilly states that retatrutide is currently available only to participants in its clinical trials.

In the Phase 2 trial, gastrointestinal adverse events were the most commonly reported side effects and were generally mild to moderate. Their frequency increased with higher doses and was more pronounced during dose escalation. Dose-dependent increases in heart rate were also observed, peaking around 24 weeks before declining later in the study.

Dosage:

There is currently no FDA-approved dosage for retatrutide. Clinical trials have evaluated different once-weekly doses and dose-escalation schedules, but investigational trial protocols should not be presented as established recommendations for general human use.

Conclusions:

Retatrutide is a promising next-generation metabolic peptide that combines GIP, GLP-1, and glucagon receptor activity in a single molecule. Clinical research has demonstrated substantial effects on body weight, waist circumference, and several metabolic measures, while ongoing Phase 3 studies continue to evaluate its potential applications across obesity and related cardiometabolic conditions.

With Phase 3 results continuing to emerge, retatrutide represents one of the most closely studied investigational therapies in the next generation of obesity and metabolic treatments. Lilly announced in July 2026 that it plans to submit a Biologics License Application to the FDA in the first quarter of 2027.

Retatrutide is intended for research purposes and is not currently an FDA-approved treatment.