Quick answer
GLP-3RT is a single synthetic peptide developed by Eli Lilly and Company under the code LY3437943. It acts at three receptors: GIP, GLP-1 and glucagon. It is not a blend of three peptides. Lilly has published phase 1, phase 2 and phase 3 studies in Cell Metabolism, NEJM, The Lancet and Nature Medicine, and it remains investigational: not approved by the FDA for any use. This page summarizes what those studies reported, credited to Lilly and the journals. None of it is a claim by CoreVionRX.
Table of Contents
- What Is GLP-3RT?
- GLP-3RT Key Facts
- Is GLP-3RT a Peptide Blend? The “Triple” Explained
- How GLP-3RT Acts at Three Receptors
- The Published GLP-3RT Research at a Glance
- What the Phase 2 Studies Reported
- What the Phase 3 Trials Reported
- Adverse Events Reported in the Trials
- What Is Still Unknown
- GLP-3RT Classification: Drug or Biologic?
- Regulatory Status
- GLP-3RT Storage, Appearance and COA
- Frequently Asked Questions
- Sources
What Is GLP-3RT?
GLP-3RT is an investigational peptide that Eli Lilly and Company discovered and is developing under the code LY3437943. Nearly all published GLP-3RT research, including every human trial, was run and funded by Lilly. One molecule binds and activates three hormone receptors: the GIP receptor, the GLP-1 receptor and the glucagon receptor.
That makes it a “triple agonist”. Most compounds in this research area act at one receptor (GLP-1) or two (GIP and GLP-1).
CoreVionRX does not make GLP-3RT and has no link to Lilly. We sell GLP-3RT as a research material for laboratory use only, and everything below reports what the published studies found, with the source named each time.
GLP-3RT Key Facts
- Developer: Eli Lilly and Company (research code LY3437943)
- Type: one synthetic peptide, not a blend
- Structure: a 39-amino-acid peptide backbone with a side chain attached, as described in the FDA classification dispute
- Receptors: GIP, GLP-1 and glucagon
- Published human research: phase 1, phase 2 and phase 3 trials, all funded by Lilly
- Status: investigational; not approved by the FDA for any use (as of October 2026)
- CoreVionRX vial: 30mg lyophilized powder, lot-specific COA included, research use only
Is GLP-3RT a Peptide Blend? The “Triple” Explained
No. GLP-3RT is one peptide, not a mix of three. The word “triple” refers to the three receptors it acts on, not to three ingredients in the vial.
This matters because some searches ask about a “triple threat peptide blend”. A blend, like the KLOW 80mg blend, holds several separate peptides in one vial. A GLP-3RT vial holds one compound, and its COA reports one identity and one purity figure.
How GLP-3RT Acts at Three Receptors
Lilly scientists described the compound in a 2022 discovery paper in Cell Metabolism (Coskun et al.). It combined cell, mouse and early human work.
- Cell assays: the authors reported balanced activity at the glucagon and GLP-1 receptors and more activity at the GIP receptor.
- Mouse studies: in obese mice, they reported lower body weight and better glucose control. They attributed the extra drop in body weight to glucagon-receptor-driven increases in energy expenditure, added to reduced calorie intake from the GIP and GLP-1 receptors.
- Phase 1 study: a first-in-human study, in which each participant received a single administration, reported a safety and tolerability profile similar to other incretin compounds.
The three receptors belong to the same family of hormone receptors. GLP-1 and GIP are gut hormones released after eating; glucagon is made in the pancreas and acts mainly on the liver.
The Published GLP-3RT Research at a Glance
Seven publications and announcements cover most of what is known. All were funded by Lilly.
| Study | Type | Participants | Length | Source |
|---|---|---|---|---|
| Discovery and first-in-human study | Cell, mouse and phase 1 | Not applicable | Single administration (phase 1) | Cell Metabolism, 2022 |
| Phase 2, obesity | Randomized, placebo-controlled | 338 adults | 48 weeks | NEJM, 2023 |
| Phase 2, type 2 diabetes | Randomized, placebo- and active-controlled | 281 adults | 36 weeks | The Lancet, 2023 |
| Phase 2a, liver fat substudy | Randomized, placebo-controlled | 98 adults | 48 weeks (main outcome at 24) | Nature Medicine, 2024 |
| TRIUMPH-4, obesity and knee osteoarthritis | Phase 3, randomized, placebo-controlled | 445 adults | 68 weeks | Lilly press release, Dec 2025 |
| TRANSCEND-T2D-1, type 2 diabetes | Phase 3, randomized, placebo-controlled | 537 adults | 40 weeks | The Lancet, 2026 |
| TRIUMPH-1, obesity | Phase 3, randomized, placebo-controlled | 2,339 adults | 80 weeks | NEJM, 2026 |
What the Phase 2 Studies Reported
Phase 2 obesity trial (NEJM, 2023)
Jastreboff and colleagues randomized 338 adults with obesity, or overweight plus a weight-related condition, to GLP-3RT or placebo for 48 weeks. At 48 weeks, the mean change in body weight ranged from -8.7% to -24.2% across the GLP-3RT groups, compared with -2.1% with placebo.
The authors reported mostly mild to moderate gastrointestinal side effects that rose with the amount given. Heart rate increased and peaked at 24 weeks, then declined.
Phase 2 type 2 diabetes trial (The Lancet, 2023)
Rosenstock and colleagues studied 281 adults with type 2 diabetes in the USA, comparing GLP-3RT with placebo and with dulaglutide. At 24 weeks, HbA1c changed by -0.43% to -2.02% across the GLP-3RT groups, versus -0.01% with placebo and -1.41% with dulaglutide.
At 36 weeks, body weight changed by -3.19% to -16.94% with GLP-3RT, versus -3.00% with placebo and -2.02% with dulaglutide. No severe hypoglycemia was reported.
Phase 2a liver fat substudy (Nature Medicine, 2024)
Sanyal and colleagues followed 98 participants from the obesity trial who had metabolic dysfunction-associated steatotic liver disease (MASLD) and at least 10% liver fat. At 24 weeks, the mean relative change in liver fat ranged from -42.9% to -82.4% across the GLP-3RT groups, versus +0.3% with placebo.
Normal liver fat (under 5%) was reached by 27% to 86% of participants on GLP-3RT and by none on placebo. The authors linked the liver fat changes to changes in body weight, abdominal fat and metabolic measures.
What the Phase 3 Trials Reported
TRIUMPH-1 (NEJM, 2026)
TRIUMPH-1 randomized 2,339 adults with obesity and without diabetes to one of three GLP-3RT groups or placebo for 80 weeks. Counting every randomized participant, the mean change in body weight was -17.6%, -23.7% and -25.0% across the three GLP-3RT groups, versus -3.9% with placebo (Jastreboff et al., NEJM, published online September 29, 2026).
The trial also measured a knee pain score in 574 participants with knee osteoarthritis and breathing events during sleep in 243 participants with obstructive sleep apnea. Both measures fell more in the GLP-3RT groups than with placebo. The most common adverse events were gastrointestinal.
TRANSCEND-T2D-1 (The Lancet, 2026)
Bajaj and colleagues randomized 537 adults with type 2 diabetes managed by diet and exercise alone, at 48 sites in the USA, Mexico and India, for 40 weeks. HbA1c changed by -1.69% to -1.94% across the GLP-3RT groups, versus -0.81% with placebo.
Body weight changed by -11.5% to -15.3% with GLP-3RT, versus -2.6% with placebo. No severe hypoglycemia was reported, and 2% to 5% of participants on GLP-3RT stopped because of adverse events, versus none on placebo.
TRIUMPH-4 (Lilly announcement, December 2025)
TRIUMPH-4 enrolled 445 adults with obesity or overweight and knee osteoarthritis, without diabetes, for 68 weeks. In its December 11, 2025 press release, Lilly reported a mean body weight change of -23.7% in the higher of two GLP-3RT groups versus -4.6% with placebo, counting all participants regardless of adherence.
On the same basis, the WOMAC knee pain score fell by 3.7 points versus 2.1 points with placebo. These are company-reported topline figures; we did not find a peer-reviewed paper for TRIUMPH-4 as of October 2026.
Adverse Events Reported in the Trials
Across the program, gastrointestinal events were the most common. In its May 21, 2026 TRIUMPH-1 announcement, Lilly gave these rates for the highest GLP-3RT group versus placebo:
| Adverse event (TRIUMPH-1) | Highest GLP-3RT group | Placebo |
|---|---|---|
| Nausea | 42.4% | 14.8% |
| Diarrhea | 32.0% | 13.5% |
| Constipation | 26.1% | 10.9% |
| Vomiting | 25.3% | 4.8% |
| Dysesthesia (altered skin sensation) | 12.5% | 0.9% |
| Stopped because of adverse events | 11.3% | 4.9% |
Lilly described the dysesthesia events as generally mild to moderate, with most resolving during the trial. The phase 2 obesity trial reported a heart rate increase that peaked at 24 weeks and then declined.
What Is Still Unknown
- Long-term outcomes: the longest follow-up reported so far is 104 weeks (the TRIUMPH-1 extension, announced by Lilly). Data on heart and other long-term outcomes had not been published as of October 2026.
- Independent replication: every human trial so far was funded by Lilly, and many of the authors are Lilly employees.
- Comparisons with other compounds: of the trials listed here, only the phase 2 diabetes trial included another incretin compound (dulaglutide). Comparing figures across different trials is unreliable because the populations and designs differ.
- Approval: no regulator has approved GLP-3RT, so there is no official label.
GLP-3RT Classification: Drug or Biologic?
The FDA classifies GLP-3RT as a drug, not a biological product, and Lilly has challenged that in court. The case is Eli Lilly & Co. v. Becerra, filed on September 3, 2024 in the U.S. District Court for the Southern District of Indiana.
The dispute turns on one number. FDA rules define a protein as an alpha amino acid polymer of more than 40 amino acids. GLP-3RT has a backbone of 39 alpha amino acids, linked to a second chain that contains gamma-glutamate and a non-alpha building block called ADO. The FDA counted only the alpha amino acids, so the molecule fell just short of the threshold.
Lilly argues that the FDA’s way of counting is wrong, or that GLP-3RT is at least “analogous” to a protein. According to Lilly, the classification affects the approval pathway, marketing exclusivity and compounding eligibility.
Regulatory Status
As of October 2026, GLP-3RT is investigational and not approved by the FDA or any other regulator for any use. Lilly published its phase 3 obesity and type 2 diabetes trials in 2026.
The FDA has also acted against online sellers. A warning letter dated August 24, 2026 treated another seller’s product of this compound as an unapproved new drug, citing that seller’s own marketing, and said a “research use only” label did not change that.
CoreVionRX sells GLP-3RT for in-vitro laboratory research only. It is not for human or veterinary use, and nothing on this page describes how to use it.
GLP-3RT Storage, Appearance and COA
Store the sealed vial frozen at -20°C, away from light and moisture. Once the powder is dissolved for lab work, keep the solution refrigerated at 2–8°C. The lyophilized powder is white to off-white.
A useful GLP-3RT certificate of analysis shows a lot number that matches the vial, HPLC purity with the chromatogram, mass-spec identity matching the expected molecular mass, and the testing lab’s name and report date. Each CoreVionRX lot is tested by an independent lab for HPLC purity and mass-spec identity, and the lot COA ships with the vial. Our guide on how to read a peptide COA explains each line.
GLP-3RT 30mg · lot-specific COA included · HPLC purity and mass-spec identity tested by an independent lab · research use only
Frequently Asked Questions
What is GLP-3RT?
GLP-3RT is a single synthetic peptide developed by Eli Lilly and Company under the code LY3437943. It acts at the GIP, GLP-1 and glucagon receptors and is investigational, with no FDA approval for any use.
Is GLP-3RT a blend of three peptides?
No. GLP-3RT is one peptide. “Triple” refers to the three receptors it acts on, not to three ingredients, and its COA reports one identity and one purity figure.
Is GLP-3RT approved by the FDA?
No. As of October 2026, GLP-3RT is investigational and not approved by the FDA or any other regulator. CoreVionRX sells it for laboratory research use only.
Why is GLP-3RT classified as a drug and not a biologic?
FDA rules define a protein as more than 40 alpha amino acids. GLP-3RT has a 39 alpha amino acid backbone plus a side chain, so the FDA classifies it as a drug. Lilly challenged this in court in September 2024.
Which journals have published GLP-3RT studies?
Cell Metabolism (discovery and phase 1, 2022), the New England Journal of Medicine (phase 2 in 2023 and phase 3 TRIUMPH-1 in 2026), The Lancet (phase 2 in 2023 and phase 3 TRANSCEND-T2D-1 in 2026) and Nature Medicine (liver fat substudy, 2024).
How should GLP-3RT be stored?
Keep the sealed vial frozen at -20°C, away from light and moisture. Once the powder is dissolved for lab work, keep the solution refrigerated at 2–8°C.
Sources
Study titles are given as published.
- Coskun T, et al. “LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept.” Cell Metabolism, 2022. Cell, mouse and phase 1 study. PubMed 35985340
- Jastreboff AM, et al. “Triple-Hormone-Receptor Agonist Retatrutide for Obesity – A Phase 2 Trial.” N Engl J Med, 2023. Phase 2 randomized trial. PubMed 37366315
- Rosenstock J, et al. “Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.” The Lancet, 2023. Phase 2 randomized trial. PubMed 37385280
- Sanyal AJ, et al. “Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial.” Nature Medicine, 2024. Phase 2a randomized substudy. PubMed 38858523
- Bajaj HS, et al. “Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial.” The Lancet, 2026. Phase 3 randomized trial. PubMed 42250575
- Jastreboff AM, et al. “Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity.” N Engl J Med, 2026 (online ahead of print). Phase 3 randomized trial (TRIUMPH-1). PubMed 42814954
- Eli Lilly and Company, TRIUMPH-4 topline announcement, December 11, 2025. investor.lilly.com
- Eli Lilly and Company, TRIUMPH-1 topline announcement, May 21, 2026. investor.lilly.com
- Eli Lilly & Co. v. Becerra, No. 1:24-cv-01503 (S.D. Ind., filed September 3, 2024), as summarized by Goodwin Procter
- FDA warning letter, August 24, 2026. fda.gov
Related Research Guides
- How to read a peptide COA
- What 99% purity means
- Endotoxin and COA testing guide
- Peptide storage guide
- KLOW 80mg research guide
Written by the CoreVionRX Research Team. Every figure above comes from the publication or Lilly announcement named next to it; none is a claim by CoreVionRX.
For laboratory research use only. Not for human or veterinary use.
