Retatrutide Explained: The GIP, GLP-1 and Glucagon Triple Agonist

Retatrutide has become one of the most searched incretin compounds because it targets three hormone receptors instead of one or two. This guide explains the pharmacology in plain English and covers its regulatory status.

What retatrutide is

Retatrutide (LY3437943) is a single synthetic peptide carrying a fatty-acid side chain that binds albumin and extends its half-life. It is an investigational drug in late-stage clinical trials. It is not a licensed medicine in the UK, and research-grade material is not for human use.

Three receptors, one molecule

Receptor	What it does in models
GLP-1 receptor	Glucose-dependent insulin release, reduced glucagon, slower gastric emptying, satiety signalling
GIP receptor	Insulin secretion and effects on fat-tissue metabolism
Glucagon receptor	Increased hepatic fat oxidation and energy expenditure

How it compares with related compounds:

• Semaglutide targets GLP-1 only.
• Tirzepatide targets GIP and GLP-1.
• Retatrutide adds glucagon-receptor activity, which is the main focus of research interest: whether glucagon-driven energy expenditure adds to the incretin effects.

What the research looks at

• Receptor balance. How strongly the molecule activates each receptor relative to the native hormones, which shapes its overall profile.
• Liver fat. Glucagon-receptor activity makes hepatic lipid metabolism a major research theme.
• Body composition. Researchers are studying how much of the weight change in trials is lean mass versus fat mass, as they are for all incretin drugs.
• Tolerability. Trial publications report gastrointestinal effects similar to other incretin agonists, along with heart-rate changes that are being studied.

Comparison with amylin analogues

Cagrilintide acts on a different hormone system (amylin). It is being studied in combination with GLP-1 drugs and is sometimes discussed alongside retatrutide. Our GLP-1 class overview sets out how the compounds relate.

Comparing retatrutide listings

1. Identity is critical. Retatrutide is a long, modified peptide that is harder to make than short peptides. Insist on mass-spec data that matches the expected molecular weight.
2. Compare on price per mg on our retatrutide comparison page.
3. Be cautious of very low prices. For complex peptides these can point to under-filled or mislabelled vials.

Summary

Retatrutide is an investigational triple agonist and an important research compound in metabolic pharmacology. It has no UK marketing authorisation. PeptideCompare provides no dosing or usage guidance, and nothing here is for human or veterinary use.