What Is GLP3-R?

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.