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01 / OVERVIEW

What is Retatrutide?

Retatrutide, also known by the development code LY3437943, is an investigational synthetic peptide designed to activate three hormone receptors: GIPR, GLP-1R and GCGR.

These receptors participate in interconnected biological systems involved in nutrient sensing, glucose regulation, appetite-related signalling and energy balance. Retatrutide is scientifically notable because a single peptide molecule has activity across all three targets.

This page explains the underlying biology as a research topic. It does not describe a treatment, recommend use, or make claims about individual outcomes.

LY3437943Development code
3Receptor targets
39Amino-acid residues
2023Phase 2 publication

02 / BIOLOGICAL MECHANISM


One peptide.
Three receptor pathways.


Retatrutide is described in the scientific literature as a triple agonist. The three receptor systems have distinct biological roles, while also interacting within broader metabolic networks.


✳ Why study three pathways together? Combining receptor activities in one molecular design provides a way to investigate how incretin and glucagon signalling interact. The biological response depends on receptor distribution, tissue context and experimental conditions.

01 · INCRETIN PATHWAY

GIPR

Glucose-dependent insulinotropic polypeptide receptor

GIPR is part of the incretin system activated in response to nutrient intake. Research explores its role in glucose-dependent insulin secretion, adipose-tissue biology and communication among the gut, pancreas and other metabolic tissues.

Nutrient-responsive signalling

02 · INCRETIN PATHWAY

GLP-1R

Glucagon-like peptide-1 receptor

GLP-1R signalling is studied in glucose-dependent insulin secretion, gastric emptying and neural circuits involved in food intake and satiety. These interconnected pathways are relevant to metabolic biology research.

Glucose and appetite-related signalling

03 · GLUCAGON PATHWAY

GCGR

Glucagon receptor

GCGR signalling is involved in hepatic glucose output, glycogen metabolism and nutrient-substrate regulation. In multi-receptor research, investigators examine how glucagon-pathway activity interacts with incretin signalling and whole-system energy balance.

Hepatic and energy-substrate signalling

LY3437943PEPTIDE STRUCTURE · SCHEMATIC

03 / MOLECULAR PROFILE

A closer look at
the molecule

Retatrutide (LY3437943) is a 39-residue, GIP-based synthetic peptide. Its engineered sequence includes non-proteinogenic amino-acid substitutions and a lipid side chain attached at Lys17. The design combines receptor pharmacology with molecular modifications intended to influence stability and pharmacokinetic behaviour.

Research nameRetatrutide
Development codeLY3437943
CAS Registry Number2381089-83-2
Molecular formulaC₂₂₁H₃₄₂N₄₆O₆₈
Approx. molecular weight4,731.4 g/mol
Peptide backboneGIP-based · 39 residues
Sequence modificationsAib² · α-MeLeu¹³ · Aib²⁰
Lipid conjugationC20 fatty diacid at Lys17
Receptor profileGIPR · GLP-1R · GCGR

Reference identity values are literature descriptors and may vary by salt form or analytical convention. They do not verify the identity, purity, biological activity or quality of any specific sample. Confirm chemical identity using appropriate orthogonal analytical methods.

04 / MOLECULAR DESIGN


How the peptide
is engineered


Sequence engineering and lipid conjugation are central to the molecule's design. The schematic below is an explanatory summary, not a synthesis protocol or a complete structural representation.


Interpretation note “39 amino acids” describes the peptide backbone length; it does not mean the entire conjugated molecule contains only 39 simple amino-acid units. Linker and lipid components also contribute to the molecular formula and mass.

01 · PEPTIDE SCAFFOLD

GIP-based 39-residue backbone

The peptide is based on a glucose-dependent insulinotropic polypeptide (GIP) sequence framework. Its single-chain architecture is engineered to engage three related class B G-protein-coupled receptors.

02 · NON-CANONICAL RESIDUES

Aib and α-methyl-leucine

Published structural descriptions identify Aib substitutions at positions 2 and 20 and α-methyl-L-leucine at position 13. Such substitutions are used in peptide design to tune stability and receptor activity; effects depend on the full molecular context.

03 · LIPID CONJUGATION

C20 fatty-diacid side chain

A C20 fatty diacid is linked to the Lys17 side chain through a spacer/linker architecture. Reversible albumin association is part of the reported design rationale for modifying circulation and exposure characteristics.

05 / METABOLIC RESEARCH

Why these pathways
matter together


Obesity and metabolic regulation are multi-organ phenomena. The three receptor systems are studied as connected signals, not as three independent switches.


This is a simplified conceptual map. It does not predict a clinical outcome or imply that receptor activation produces a uniform response across species, tissues or experimental models.

GUT & NUTRIENT SENSING

GIPR / GLP-1R

Incretin signalling links nutrient intake with pancreatic hormone responses and other tissue-specific processes.

HEPATIC SUBSTRATE CONTROL

GCGR

Glucagon signalling contributes to hepatic glucose production and the regulation of circulating energy substrates.

INTEGRATED SYSTEM

Metabolic network

Research examines how these pathways interact across tissues, including glucose homeostasis, nutrient handling and energy balance.

06 / PHARMACOLOGY

Understanding
receptor activity

Retatrutide has been characterised as a unimolecular agonist with activity at GIPR, GLP-1R and GCGR. Published studies compare its activity with the endogenous ligands, but numerical potency depends on the receptor construct, assay platform, species and endpoint.

For that reason, this guide does not reproduce unverified EC50 values as universal constants. A meaningful comparison should cite the original assay, receptor species, cell system, readout and experimental conditions.

GIPRGIP-related incretin receptor
GLP-1RGLP-1-related incretin receptor
GCGRGlucagon receptor
Potency is assay-dependent · Compare like with like

07 / RESEARCH CONTEXT

From receptor biology
to research questions

Published work has examined retatrutide as an investigational multi-receptor agonist. The following themes provide context for scientific reading, not instructions for use.

A / 01

Receptor pharmacology

How does activity at GIP, GLP-1 and glucagon receptors differ, and how are those activities characterised in experimental systems?

A / 02

Metabolic signalling

How do incretin and glucagon pathways intersect in studies of nutrient handling, glucose homeostasis and energy-substrate regulation?

A / 03

Molecular design

How do peptide sequence modifications and lipid conjugation influence molecular properties and receptor pharmacology?

↗
SELECTED PUBLICATION

Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial

Jastreboff AM et al. New England Journal of Medicine (2023). DOI: 10.1056/NEJMoa2301972.

Read publication ↗

Further scientific reading

08 / RESEARCH NOTES

Frequently asked
questions

A concise guide to terminology and research context.

Is retatrutide an approved medicine?

Retatrutide has been described by its developer as an investigational medicine. Its research status and regulatory position may change; consult current regulator and developer information for updates.

Why is it called a triple agonist?

Because it has agonist activity at three receptor targets: the glucose-dependent insulinotropic polypeptide receptor (GIPR), glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR).

Does this page provide medical or dosing guidance?

No. This is an educational overview of published scientific concepts. It does not provide dosage, administration, treatment, diagnostic or medical advice.

What does a molecular formula tell a researcher?

A molecular formula describes the elemental composition of a defined chemical entity. It does not by itself establish identity, purity, biological activity or the quality of a specific sample.

What does the C20 fatty-diacid modification do?

The lipid side chain is part of the molecular design and is associated with reversible albumin binding. It is discussed in the literature as a way to influence exposure and pharmacokinetic properties, rather than as a stand-alone measure of biological potency.

Are EC50 values interchangeable between studies?

No. EC50 values depend on assay design, receptor species and expression, cell background, endpoint and analysis method. Values should only be compared when the experimental systems are sufficiently aligned.

What is the current research status?

As of the latest developer information reviewed for this page (October 2026), retatrutide remains investigational and has not been approved by the FDA or other regulatory agencies. Regulatory status can change; check official sources for current information.

Does this page describe human use or supply suitability?

No. This page is scientific education only. It does not recommend human or veterinary use, establish a product's suitability for research, or verify any supplier, batch, quality system or regulatory status.

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