Retatrutide: a triple receptor agonist in clinical development

Abstract bar chart and line graph in blue tones

Prepared by: Research Desk. Sources are linked for verification.

Published 19 October 2026

At a glance

Type: synthetic peptide, single molecule acting on three receptors
Developer: Eli Lilly and Company (code name LY3437943)
Research stage: phase 3 clinical trials (the TRIUMPH programme)
Regulatory status: investigational; not approved by FDA or any other regulator as of 19 October 2026

What retatrutide is

Retatrutide is an investigational peptide designed to activate three hormone receptors: the glucose-dependent insulinotropic polypeptide receptor (GIPR), the glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR). Because it acts on all three, it is often called a "triple agonist" or "triple hormone receptor agonist". The molecule is built on a chain of 39 amino acids with a fatty-acid side chain that extends how long it stays in circulation.

Research history

Retatrutide follows earlier incretin research. GLP-1 receptor agonists were developed first, and dual GIP/GLP-1 receptor agonists followed. Adding glucagon receptor activity was intended to add an effect on energy expenditure on top of the appetite-related effects of the incretin receptors.

The first major publication was a 2022 paper in Cell Metabolism by Coskun et al., which reported laboratory, mouse and early human data under the code name LY3437943.

Mechanisms studied in preclinical work

Receptor activity. In cell assays, Coskun et al. (2022) reported balanced activity at the glucagon and GLP-1 receptors and greater activity at the GIP receptor.
Energy balance in mice. In obese mice, the compound lowered body weight and blood glucose. The authors attributed part of the body-weight effect to increased energy expenditure through the glucagon receptor, on top of lower calorie intake through the GIP and GLP-1 receptors.
Early human pharmacology. The same paper included a phase 1 single-exposure study reporting a safety and tolerability profile similar to other incretin-based compounds, and a long half-life in circulation.

The published research landscape

Retatrutide has a larger human evidence base than most compounds on this site, because it is in formal pharmaceutical development.

Phase 2, obesity. Jastreboff et al. (2023) in the New England Journal of Medicine reported a 48-week randomised, double-blind, placebo-controlled trial in 338 adults with obesity, or with overweight plus a weight-related condition. Mean body weight fell by up to 24.2% at 48 weeks in the retatrutide groups, compared with 2.1% in the placebo group. Gastrointestinal adverse events were the most common.
Phase 2, type 2 diabetes. Rosenstock et al. (2023) in The Lancet reported a randomised phase 2 trial in adults with type 2 diabetes, with glycated haemoglobin and body weight as outcomes, including an active comparator arm.
Phase 3. Lilly's TRIUMPH programme is testing retatrutide in larger populations. In July 2026 the company announced topline results from TRIUMPH-2 and TRIUMPH-3 in a press release. Full peer-reviewed results for these trials were not yet published when this page was prepared. Ongoing studies are listed on ClinicalTrials.gov.

Regulatory status

United States. Retatrutide is not FDA-approved. Lilly has said it plans to submit an application in the first quarter of 2027. FDA and Lilly have been in a dispute over whether the molecule should be classified as a drug or as a biologic; as of October 2026, FDA's position is that it is a drug.
Other regions. We found no marketing authorisation in the EU, UK or elsewhere as of 19 October 2026.
Research-grade material. Material sold as a laboratory reagent is not the investigational product used in Lilly's trials and has not been assessed by any regulator.

Key terms

Agonist. A molecule that binds a receptor and activates it.
Incretins. Gut hormones, including GLP-1 and GIP, that are released after eating and affect insulin secretion.
Glucagon receptor. The receptor for glucagon, a pancreatic hormone involved in glucose release and energy expenditure.
Topline results. The first summary of a trial's main outcomes, released by a sponsor before full peer-reviewed publication.

Limitations of the evidence

Published efficacy and safety data come from trials sponsored by the developer.
Phase 3 results announced by press release have not yet been through peer review.
Trial results apply to the trial product under trial conditions and say nothing about the identity or purity of research-grade material.

Where researchers source it

Purita is a store that lists Retatrutide for laboratory research use only. Its product page carries the label "For Research Use Only. Not for human or animal administration."

Purita product page

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