GLP3-R 20mg

Overview

GLP3-R is the catalog designation for retatrutide (LY3437943), a synthetic peptide characterized in the peer-reviewed literature as a single-molecule agonist at three receptors: GIP, GLP-1, and glucagon.[1] Coskun and colleagues published the discovery-to-proof-of-concept characterization in Cell Metabolism, and Urva et al. reported the first multiple-ascending-dose clinical pharmacology study in The Lancet.[1][2]

What distinguishes this compound within the incretin literature is the third receptor. GLP-1-selective agonists engage one receptor and dual agonists such as tirzepatide engage GIP and GLP-1; retatrutide adds glucagon-receptor agonism to that pair.[1][8] Because the three receptors couple to overlapping but non-identical downstream pathways, the compound is used in research settings as the comparator that isolates the contribution of glucagon-receptor engagement. Hammoud and Drucker have reviewed the contrasting cardiometabolic actions of GIP and GLP-1 that motivate this class of comparison, and Samms et al. set out the mechanistic framework for combining incretin receptor activities.[9][10]

The published clinical record for retatrutide consists of phase 1 and phase 2 investigations of the pharmaceutical formulation: a phase 1b multiple-ascending-dose trial, a phase 2 trial in obesity, a phase 2 trial in type 2 diabetes, and a phase 2a trial in metabolic dysfunction-associated steatotic liver disease.[2][3][4][5] Urva et al. separately reported effects on gastric emptying, and Katsi et al. published a review of the compound in the obesity-pharmacotherapy literature.[6][7]

Retatrutide remains an investigational compound and is not approved by any regulatory authority. The studies cited above evaluated a pharmaceutical formulation under clinical trial conditions; the research-grade material supplied here is not that product and is intended for laboratory research use only.

Reported Mechanism

1. Triple Receptor Engagement

Retatrutide is described as engaging three class-B G-protein-coupled receptors with a single peptide sequence: the GIP receptor, the GLP-1 receptor, and the glucagon receptor.[1] This distinguishes it from dual GIP/GLP-1 agonism and from GLP-1-selective agonism, and it is the structural feature that defines the compound's research role.[8]

2. Incretin-Axis Signalling

GLP-1 and GIP receptor agonism act on the incretin axis, where insulinotropic activity is conditioned on ambient glucose. Hammoud and Drucker reviewed how the cardiometabolic actions of GIP and GLP-1 differ beyond the pancreas, and Samms et al. examined the mechanistic rationale for engaging GIP alongside GLP-1.[9][10]

3. Gastrointestinal Transit

Urva et al. reported that retatrutide delays gastric emptying, a pharmacodynamic readout shared across the incretin-agonist class and one of the standard endpoints used to characterize these compounds.[6]

4. Comparator Positioning

Coskun et al. previously characterized LY3298176 (tirzepatide) as the first unimolecular dual GIP/GLP-1 receptor agonist.[8] Placing the triple agonist alongside that dual agonist and a GLP-1-selective agonist gives investigators a graded series — one, two, or three receptors engaged by a single molecule — which is why this compound appears frequently as a reference arm in incretin pharmacology.[7]

Receptor-level and clinical findings summarized here were obtained with the pharmaceutical formulation under controlled study conditions. No conclusions about research-grade material are implied.

Research Applications

Published investigations of retatrutide fall into the following areas. All studies listed used the pharmaceutical formulation.

1. Receptor pharmacology and discovery characterization — Coskun et al. reported the discovery-to-proof-of-concept work defining triple GIP/GLP-1/glucagon agonism.[1]
2. Clinical pharmacology and dose-ranging — Urva et al. published a phase 1b multiple-ascending-dose trial in people with type 2 diabetes.[2]
3. Obesity research — Jastreboff et al. reported a phase 2 trial in The New England Journal of Medicine.[3]
4. Type 2 diabetes research — Rosenstock et al. reported a randomised, double-blind, placebo- and active-controlled phase 2 trial.[4]
5. Hepatic steatosis research — Sanyal et al. reported a randomized phase 2a trial in metabolic dysfunction-associated steatotic liver disease.[5]
6. Gastrointestinal pharmacodynamics — Urva et al. reported effects on gastric emptying.[6]
7. Comparative incretin pharmacology — the compound serves as the triple-agonist arm in comparisons against dual and selective agonists.[7][8]

Research Summary

Foundational Studies

Mechanistic Themes

• Triple receptor agonism - one peptide engages the GIP, GLP-1, and glucagon receptors
• Graded comparator series - selective, dual, and triple agonists allow receptor contributions to be separated
• Glucose-dependent incretin action - insulinotropic activity in this class is conditioned on ambient glucose
• Investigational status - no regulatory approval in any jurisdiction