The science of GLP3

One molecule, three receptors

Retatrutide (GLP-3, LY3437943) is a next-generation research peptide that engages three metabolic receptors at once. Here is what that means and why it matters.

What retatrutide is

Retatrutide is a synthetic, 39-amino-acid peptide designed as a triple agonist: a single molecule that activates the receptors for GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon. Developed by Eli Lilly under the code name LY3437943, it is known to researchers as GLP-3 and has become one of the most intensively studied compounds in metabolic research.

Incretin agonists progressed from a single receptor (GLP-1) to two (GLP-1 and GIP). Retatrutide is the three-receptor step, which is the origin of the GLP-3 (GLP3) name.

The three targets

GLP-1

incretin signaling and appetite pathways

GIP

incretin response and metabolic signaling

glucagon

energy regulation and substrate metabolism

single-molecule triple agonist

GLP-1 receptor

The most studied incretin pathway. In research models, GLP-1 receptor activation is associated with glucose-dependent insulin signaling and effects on appetite-regulating circuits.

GIP receptor

The other major incretin receptor. Combined GLP-1/GIP activation is a central theme of current dual-agonist literature, and retatrutide builds on that foundation.

Glucagon receptor

The third target and the distinguishing feature of retatrutide. In research settings, glucagon-receptor engagement is studied for its role in energy expenditure and hepatic lipid metabolism.

Why researchers choose retatrutide

As the first triple agonist to reach clinical study, retatrutide produced some of the largest metabolic effect sizes reported for the incretin class in early-phase trials, exceeding single (GLP-1) and dual (GLP-1/GIP) agonists. That combination of GLP-1, GIP, and glucagon activity is why GLP-3 has become one of the most sought-after compounds in current metabolic research.

Every lot we supply is manufactured to one specification and batch-tested, so a 10 mg vial holds the same material as a 40 mg vial at ≥ 99% purity. Only the fill quantity changes.

Handling in the lab

Retatrutide ships as a lyophilized (freeze-dried) powder for reconstitution. Store vials at room temperature away from light, reconstitute with an appropriate sterile diluent, refrigerate at 2 °C to 8 °C after reconstitution, and refer to the batch certificate of analysis for concentration and stability guidance. Full handling notes are on the product page.

A note on sourcing: This page is an educational overview for researchers and is not medical advice. Nothing here describes or endorses human use. See our research disclaimer.