Retatrutide (LY3437943): The Triple Agonist Explained

Retatrutide (Eli Lilly code LY3437943) is a single peptide that hits three metabolic receptors at once: GLP-1, GIP, and glucagon. That third target — glucagon — is what sets it apart from earlier incretin drugs and is why researchers often call it a "triple G" agonist. It's one of the most-watched compounds in metabolic research right now, largely because its phase 2 weight-loss numbers were the largest reported for any drug in this class to date.

Research Background

Retatrutide came out of Eli Lilly's incretin program as a follow-on to tirzepatide, the GIP/GLP-1 dual agonist. The idea was straightforward: if adding GIP to GLP-1 improved results, would adding glucagon-receptor activity on top do more? The discovery-to-proof-of-concept work was published by Coskun and colleagues in Cell Metabolism in 2022, which laid out the molecule's balanced three-receptor pharmacology and once-weekly profile. From there it moved into phase 2 trials across obesity, type 2 diabetes, and steatotic liver disease.

How It Works

Each receptor contributes something. The GLP-1 and GIP arms drive glucose-dependent insulin secretion and suppress appetite — the same appetite and glycemic effects seen with other incretin agents. The glucagon arm is the addition: glucagon-receptor signaling raises energy expenditure and pushes the liver toward fat oxidation and mobilization. In other words, GLP-1 and GIP pull intake down while glucagon nudges energy use up. Balancing glucagon's activity is the tricky part, because glucagon on its own can raise blood sugar — retatrutide is tuned so the GLP-1 component keeps glycemic control intact.

What the Research Shows

The trials to date are in humans and have been published in major journals:

• In the phase 2 obesity trial (Jastreboff et al., *NEJM*, 2023), participants on the 12 mg dose had a mean body-weight reduction of about 24% at 48 weeks, versus roughly 2% for placebo. At the top dose, around 83% of participants lost at least 15% of their body weight.
• In the phase 2 type 2 diabetes trial (Rosenstock et al., *The Lancet*, 2023), retatrutide produced substantial HbA1c reductions alongside meaningful weight loss over 24 weeks, with a safety profile consistent with the GLP-1/GIP incretin class.
• In a phase 2a trial in MASLD (metabolic dysfunction-associated steatotic liver disease; Sanyal et al., *Nature Medicine*, 2024), higher doses cut liver fat by roughly 80% or more at 24 weeks, with most participants reaching normal liver-fat levels by 48 weeks.

The most common adverse effects across these studies were gastrointestinal — nausea, diarrhea, vomiting — typical of the drug class and generally dose-related. All full citations are in the References section below. Retatrutide is now in phase 3 (the TRANSCEND program).

Storage & Handling

Retatrutide is supplied in lyophilized (freeze-dried) form. Store it at -20°C or below, protected from light and moisture. Reconstitute immediately before use with a sterile solvent appropriate to your protocol, and avoid repeated freeze-thaw cycles, which degrade the peptide.

Frequently Asked Questions

What makes retatrutide different from tirzepatide or semaglutide? Semaglutide targets one receptor (GLP-1); tirzepatide targets two (GIP and GLP-1); retatrutide targets three by adding glucagon-receptor activity, which brings in an energy-expenditure and hepatic-fat angle the others don't have.

Is retatrutide approved? As of this writing it is investigational — it has completed phase 2 and is in phase 3 trials. It is sold here strictly for research use only.

What purity does Dynamite Research Peptides provide? Our retatrutide is 99%+ purity with a Certificate of Analysis available for every batch, verified by HPLC and mass spectrometry.

All products are for research use only — not for human or animal consumption.