Palmetto Peptides Complete Guide to the Research Peptide Retatrutide
Palmetto Peptides Complete Guide to the Research Peptide Retatrutide
Last Updated: March 19, 2026 | Reading Time: ~18 minutes
Legal Disclaimer: All information in this article is provided for educational and informational purposes only. Retatrutide (LY3437943) is an investigational research peptide. It has not been approved by the U.S. Food and Drug Administration (FDA) or any other regulatory authority for therapeutic, diagnostic, or preventive use in humans or animals. Products sold by Palmetto Peptides are intended exclusively for in vitro laboratory research by qualified scientific professionals. Nothing in this article constitutes medical advice, and no information here should be interpreted as a recommendation to use, administer, or obtain any compound for personal use. Always consult a licensed healthcare provider for medical guidance.
What Is Retatrutide? (Direct Answer)
Retatrutide, also designated LY3437943, is a synthetic 39-amino-acid peptide that simultaneously activates three hormone receptors central to metabolic regulation: the glucose-dependent insulinotropic polypeptide receptor (GIPR), the glucagon-like peptide-1 receptor (GLP-1R), and the glucagon receptor (GCGR). This makes it the first-in-class triple incretin receptor agonist to reach advanced clinical development, with Phase 3 trials currently ongoing under Eli Lilly's TRIUMPH program.
From a research standpoint, retatrutide is significant because it extends beyond the single-receptor approach of compounds like semaglutide and the dual-receptor approach of tirzepatide by adding glucagon receptor agonism, a mechanism associated with increased hepatic fat oxidation and energy expenditure. It is currently investigational and not approved for any human or veterinary therapeutic use.
Palmetto Peptides supplies retatrutide as a research-grade peptide for qualified laboratory use. If you are looking to explore this compound for in vitro work, you can find it on our Retatrutide product page. For related compounds of research interest, see our GLP-1 Peptide Research Collection and Metabolic Research Peptides.
Table of Contents
- Background and Research Context
- Molecular Structure and Chemical Properties
- Mechanism of Action: How the Triple Agonism Works
- Summary of Published Clinical Research
- Phase 2 Obesity Trial Results at a Glance (Table)
- Retatrutide vs. Other Incretin-Based Research Peptides
- Safety and Tolerability Profile in Published Trials
- Ongoing Phase 3 Research: The TRIUMPH Program
- Retatrutide in Liver and Cardiometabolic Research
- Regulatory Status and FDA Compliance Notes
- How to Handle and Store Retatrutide for Research
- Related Research Peptides
- Frequently Asked Questions
- Peer-Reviewed Citations
1. Background and Research Context
The last decade of metabolic research has been shaped by incretin-based peptide pharmacology. Compounds designed to activate gut-derived hormone receptors have become central tools in understanding how the body regulates energy intake, insulin secretion, glucagon suppression, and lipid metabolism. Semaglutide demonstrated that sustained GLP-1 receptor activation could produce meaningful changes in glycemic markers and body composition. Tirzepatide expanded on that foundation by combining GLP-1 and GIP receptor activity in a single molecule, introducing the dual agonist concept to Phase 3 and regulatory approval.
Retatrutide represents the next logical step in this progression. Developed by Eli Lilly and Company and first described in a landmark 2022 Cell Metabolism paper by Coskun et al., retatrutide was engineered to simultaneously engage all three receptors through careful backbone design rooted in a GIP receptor agonist scaffold with strategic substitutions to gain GLP-1 and glucagon receptor activity. The premise behind adding glucagon agonism is that glucagon, long understood primarily as an insulin antagonist, has additional actions at the liver that could amplify fat oxidation and energy expenditure beyond what GLP-1 or GIP agonism alone can accomplish.
For research scientists, this makes retatrutide a compelling tool. It offers a way to study what happens when all three of these pathways are activated simultaneously, which has implications for understanding not just metabolic disease, but also fatty liver disease, cardiovascular risk markers, and the interplay between energy sensing hormones.
2. Molecular Structure and Chemical Properties
Understanding retatrutide begins at the molecular level. This is not a simple peptide. It is a precisely engineered synthetic molecule with several deliberate structural features that distinguish it from its natural hormone counterparts and from other research peptides in this class.
2.1 Basic Identification
| Property | Value |
|---|---|
| Common Name | Retatrutide |
| Research Designation | LY3437943 |
| CAS Number | 2381089-83-2 |
| Amino Acid Count | 39 |
| Molecular Weight | ~4,731 Da (free base) |
| Backbone Scaffold | GIP receptor agonist-derived |
| Route of Administration (Preclinical/Clinical Research) | Subcutaneous injection |
| Storage (Research Grade) | Lyophilized; at or below -20°C |
2.2 Amino Acid Sequence and Key Modifications
Retatrutide carries the following amino acid sequence:
Y-Aib-QGTFTSDYSI-MeL-LDKK(fatty acid chain)-AQAib-AFIEYLLEGGPSSGAPPPS-NH2
Several residues differ from native hormones, and these differences are intentional:
Aib substitutions (positions 2 and 20): Alpha-aminoisobutyric acid (Aib) replaces natural alanine at these positions. Aib is a well-established strategy for protecting the N-terminal region against cleavage by dipeptidyl peptidase-4 (DPP-4), the enzyme that rapidly inactivates endogenous GLP-1 in circulation. This modification is what gives retatrutide its extended half-life suitable for once-weekly dosing.
Alpha-methyl leucine (position 13): A methylated leucine is introduced mid-chain to impose conformational rigidity, which stabilizes the active binding conformation and may contribute to the peptide's balanced receptor activation profile.
C20 fatty diacid conjugation (position 26/Lys side chain): Perhaps the most pharmacokinetically significant modification. A C20 fatty diacid moiety is attached via a chemical linker (AEEA spacer and gamma-glutamate) to a lysine side chain. This fatty acid chain binds reversibly to serum albumin in circulation, effectively creating a depot that extends the plasma half-life to approximately one week, enabling once-weekly subcutaneous dosing in clinical studies.
C-terminal amide: The carboxylic acid group at the C-terminus is replaced with a carboxamide (L-serinamide), which improves proteolytic stability at the tail of the peptide.
2.3 Receptor Binding Potency
In published in vitro assays, retatrutide demonstrates the following receptor activity (EC50 values):
| Receptor | EC50 (human) | Relative Potency |
|---|---|---|
| GIPR | ~0.064 nM | Highest |
| GLP-1R | ~0.775 nM | High |
| GCGR | ~5.79 nM | Moderate |
This potency profile is notable because it demonstrates enhanced activity at the GIP receptor relative to native GIP itself, while maintaining meaningful activity at both the GLP-1 and glucagon receptors. Compared to tirzepatide, which lacks clinically significant glucagon receptor activity, retatrutide's GCGR engagement is a defining pharmacological characteristic.
3. Mechanism of Action: How the Triple Agonism Works
To appreciate why retatrutide is generating so much interest in the research community, it helps to understand what each receptor does individually and what happens when all three are activated simultaneously.
3.1 GLP-1 Receptor Agonism
The GLP-1 receptor is expressed primarily in pancreatic beta cells, the brain, the gut, and the cardiovascular system. GLP-1 receptor activation promotes glucose-dependent insulin secretion, suppresses glucagon release after meals, slows gastric emptying, and produces satiety signals in the hypothalamus. These combined effects reduce caloric intake and improve postprandial glycemic control. This is the most studied and best-characterized pathway in the incretin class.
3.2 GIP Receptor Agonism
GIP (glucose-dependent insulinotropic polypeptide) was originally characterized as an incretin hormone, but its role in fat tissue and the brain has drawn increasing research attention. GIP receptor activation appears to potentiate insulin secretion in a glucose-dependent manner and may also modulate energy storage in adipose tissue and reduce some of the nausea associated with GLP-1 receptor activation. Tirzepatide's clinical profile relative to semaglutide has been partly attributed to its GIP receptor activity, though the precise mechanisms remain an active area of investigation.
3.3 Glucagon Receptor Agonism
This is the component that truly distinguishes retatrutide from everything that came before it. Glucagon receptor activation at the liver promotes glycogenolysis, fatty acid oxidation, and lipolysis. Crucially, it increases hepatic energy expenditure. In a metabolic disease context, this has implications for hepatic fat accumulation, which is a hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD). By driving the liver to oxidize fat rather than store it, glucagon agonism adds a mechanism that neither GLP-1 nor GIP receptor activation provides.
There is also evidence from preclinical studies that glucagon receptor activation can reduce appetite through direct hypothalamic signaling pathways, though the full extent of this central effect in humans is still being characterized.
3.4 The Synergistic Effect
What makes the triple agonist concept compelling from a research perspective is not just the additive contribution of each pathway, but the potential for synergy. Activating all three receptors simultaneously may produce downstream effects that exceed what any two pathways achieve in combination. Preclinical models have consistently shown that the triple agonist approach outperforms dual agonists on measures of weight reduction, liver fat reduction, and improvement in lipid parameters. Whether this translates to a meaningfully superior clinical profile is exactly what the Phase 3 TRIUMPH trials are designed to answer.
4. Summary of Published Clinical Research
The clinical research on retatrutide has moved unusually quickly for an investigational peptide. Phase 1 data established tolerability and provided a pharmacokinetic profile. Phase 2 trials in two distinct populations (obesity without type 2 diabetes, and obesity with type 2 diabetes) were published simultaneously in the New England Journal of Medicine and The Lancet in 2023, providing the first substantial human efficacy and safety data. A Nature Medicine paper in 2024 extended findings to liver fat outcomes.
Below is a summary of the key published studies to date.
4.1 Phase 1 Discovery Paper
Coskun T, et al. Cell Metabolism, 2022. This paper described the discovery and preclinical development of LY3437943, covering its receptor binding profile, pharmacokinetic properties, and efficacy in rodent models. It demonstrated that the compound reduced body weight and improved glycemic control in diabetic mouse models and provided the mechanistic rationale for human investigation.
4.2 Phase 2 Obesity Trial (Without Type 2 Diabetes)
Jastreboff AM, et al. New England Journal of Medicine, 2023. This was a multicenter, double-blind, randomized, placebo-controlled Phase 2 trial conducted in the United States. It enrolled 338 adults with a BMI of 30 or higher (or BMI 27 or higher with at least one weight-related comorbidity) but without type 2 diabetes. Participants received once-weekly subcutaneous injections of retatrutide at doses of 1 mg, 4 mg, 8 mg, or 12 mg, or placebo, for 48 weeks.
The primary endpoint was percentage change in body weight from baseline to 24 weeks. Secondary endpoints included weight change at 48 weeks and proportion of participants achieving clinically significant weight reduction thresholds.
4.3 Phase 2 Type 2 Diabetes Trial
Rosenstock J, et al. The Lancet, 2023. This was a randomized, double-blind, placebo-controlled and active comparator-controlled Phase 2 trial enrolling 281 adults with type 2 diabetes and BMI of 25 to 50 kg/m². Participants received retatrutide at doses of 0.5 mg, 4 mg, 8 mg, or 12 mg weekly, 1.5 mg dulaglutide, or placebo for 36 weeks.
This trial examined both glycemic control (HbA1c) and body weight as co-primary endpoints, providing data on retatrutide's potential utility in the type 2 diabetes research context.
4.4 Phase 2 Liver Fat Substudy
Sanyal AJ, et al. Nature Medicine, 2024. This was a pre-specified substudy of the Phase 2 obesity trial, focusing specifically on participants with metabolic dysfunction-associated steatotic liver disease (MASLD) and baseline liver fat content at or above 10%. The primary endpoint was relative change in liver fat content from baseline to 24 weeks.
4.5 Phase 3 TRIUMPH-4 (Topline Data)
Eli Lilly press release, 2025. Eli Lilly announced positive topline results from the Phase 3 TRIUMPH-4 trial evaluating retatrutide in adults with obesity or overweight and knee osteoarthritis. The data demonstrated substantial weight reduction alongside significant improvement in osteoarthritis pain scores, representing the first successful Phase 3 readout for the compound.
5. Phase 2 Obesity Trial Results at a Glance
The table below summarizes the key efficacy findings from the Phase 2 obesity trial (Jastreboff et al., 2023, NEJM) across dose groups.
| Dose Group | Mean Weight Change at 24 Weeks | Mean Weight Change at 48 Weeks | % Achieving ≥10% Weight Loss at 48 Weeks | % Achieving ≥15% Weight Loss at 48 Weeks |
|---|---|---|---|---|
| Placebo | -1.6% | -2.1% | 9% | 2% |
| 1 mg | -7.2% | -8.7% | — | — |
| 4 mg | -12.9% | -17.1% | 75% | 60% |
| 8 mg | -17.3% | -22.8% | 91% | 75% |
| 12 mg | -17.5% | -24.2% | 93% | 83% |
Source: Jastreboff AM et al., N Engl J Med. 2023;389:514-526. All data from published Phase 2 research. Results are from a clinical trial population and do not predict outcomes in any individual or non-research setting.
A few data points from the Phase 2 diabetes trial are also worth noting for researchers studying glycemic endpoints. At the 12 mg dose over 36 weeks, participants achieved approximately 16.9% body weight reduction compared to 3.0% with placebo. HbA1c was reduced by approximately 2.2%, and 77 to 82% of participants on the highest retatrutide dose achieved HbA1c at or below 6.5% by the end of the trial period.
6. Retatrutide vs. Other Incretin-Based Research Peptides
For researchers deciding which peptide tools best suit their study design, the distinctions between these compounds matter. Here is a comparative overview:
Retatrutide vs. Semaglutide
Semaglutide is a single GLP-1 receptor agonist. Its mechanism is well-characterized, making it a useful research standard or comparator. Retatrutide adds GIPR and GCGR activity. In published Phase 2 data, the magnitude of body weight reduction observed with retatrutide at the higher doses exceeded what semaglutide achieved in its own clinical program. However, these are different trials, different populations, and different timepoints, so direct comparisons must be approached carefully.
The key structural difference is that retatrutide's His1 N-terminal histidine is preserved and available for glucagon receptor engagement, whereas semaglutide lacks this interaction entirely.
Retatrutide vs. Tirzepatide
Tirzepatide is the FDA-approved dual GIP/GLP-1 receptor agonist. Like retatrutide, it is built on a GIP scaffold. The critical distinction is glucagon receptor activity. Retatrutide's design preserved the N-terminal histidine and introduced mid-sequence modifications that enable GCGR engagement; tirzepatide, while also a dual agonist, does not have meaningful glucagon receptor activity.
From a research perspective, the contrast between tirzepatide and retatrutide offers an opportunity to isolate the incremental contribution of glucagon receptor agonism to outcomes like liver fat reduction and energy expenditure.
For researchers working with these compounds in parallel, see our Tirzepatide Research Peptide page and Semaglutide Research Peptide page.
Retatrutide vs. Cotadutide
Cotadutide is a GLP-1/glucagon dual agonist that lacks GIP receptor activity. Comparing it to retatrutide allows researchers to examine the specific contribution of GIP receptor engagement to the overall triple agonist profile. Both compounds activate the glucagon receptor, making them useful for studying the hepatic and energy expenditure effects of glucagon agonism, but their appetite and insulin secretion profiles differ.
7. Safety and Tolerability Profile in Published Trials
Honest reporting of safety findings is essential to good science. The Phase 2 trials provided a clear picture of what the research community can expect from retatrutide's tolerability profile.
7.1 Most Common Adverse Events
In the Phase 2 obesity trial, adverse events were reported in 73 to 94% of participants across retatrutide dose groups (compared to 70% in the placebo group). The events that occurred more frequently in the retatrutide groups than in placebo were predominantly gastrointestinal, including nausea, diarrhea, vomiting, and constipation. These are consistent with the adverse event profile observed across the incretin class.
Importantly, gastrointestinal events were dose-dependent: they occurred more often in the higher-dose groups (8 mg and 12 mg) and were generally described as mild to moderate in severity. The Phase 2 trial design included dose-escalation regimens that varied starting dose (2 mg vs. 4 mg), and the lower starting dose was associated with improved tolerability.
7.2 Discontinuations
Adverse events leading to study drug discontinuation occurred in 6 to 16% of participants in the retatrutide groups, compared to none in the placebo group. The discontinuation rate increased at higher doses, consistent with the dose-dependent nature of gastrointestinal effects.
7.3 Serious Adverse Events
The incidence of serious adverse events was 4% in the placebo group and ranged from 0 to 6% in the retatrutide groups. No single serious adverse event appeared at a notably elevated rate in the retatrutide groups compared to placebo in Phase 2 data, though the studies were not powered for low-frequency event detection.
7.4 Areas Requiring Further Investigation
Researchers and reviewers have noted that, given retatrutide's glucagon receptor activity and the magnitude of weight loss it produces, longer-term studies are needed to characterize risks for biliary events (gallstones), pancreatitis, and hepatic effects. The Phase 3 TRIUMPH trials are designed with these endpoints in mind. This is an active and unresolved area of the research literature.
Research Note: The safety data summarized above comes from clinical trials in human subjects conducted under rigorous FDA oversight. It is provided here for scientific information purposes only and does not apply to, or predict outcomes from, any non-clinical or unauthorized use of the compound.
8. Ongoing Phase 3 Research: The TRIUMPH Program
The TRIUMPH (TRIple hormone receptor agonist for Metabolic and obesity-related diseases in a Unified Phase 3 program in Humans) clinical trial series represents the most comprehensive clinical evaluation of any triple agonist peptide to date. As of early 2026, multiple Phase 3 trials are ongoing or reporting results.
The TRIUMPH program includes studies across the following therapeutic research areas:
Obesity and overweight (without diabetes): Evaluating long-term efficacy and safety at the highest investigational doses, with cardiovascular outcomes as a key endpoint.
Type 2 diabetes: Examining glycemic control, weight, and cardiorenal outcomes in a diabetic population over 52 or more weeks.
Knee osteoarthritis: The TRIUMPH-4 trial reported positive topline data in 2025, showing up to 71.2 lbs (approximately 24% of body weight) average reduction alongside significant improvement in WOMAC pain scores.
Metabolic dysfunction-associated steatotic liver disease (MASLD/MASH): A dedicated study examining histological endpoints including MASH resolution and fibrosis improvement, areas where the triple agonist's hepatic glucagon effects are particularly relevant.
Obstructive sleep apnea: Evaluating whether retatrutide's metabolic effects translate to improvement in apnea-hypopnea index.
Chronic low back pain: Assessing musculoskeletal benefits potentially mediated by weight reduction and anti-inflammatory pathways.
Cardiovascular and renal outcomes: A longer-term outcomes trial examining mortality, major adverse cardiovascular events, and renal function endpoints.
This breadth of investigation reflects the scientific community's assessment that retatrutide's mechanism of action may have implications beyond weight management, extending into cardiometabolic, musculoskeletal, and hepatic disease.
9. Retatrutide in Liver and Cardiometabolic Research
One of the most striking findings in the retatrutide research literature involves liver fat reduction. The 2024 Nature Medicine substudy by Sanyal et al. examined participants from the Phase 2 obesity trial who had baseline MASLD with liver fat content at or above 10%.
9.1 Liver Fat Reduction
The mean relative change from baseline in liver fat content at 24 weeks was:
| Dose | Mean Relative Change in Liver Fat (Week 24) |
|---|---|
| Placebo | +0.3% |
| 1 mg | -42.9% |
| 4 mg | -57.0% |
| 8 mg | -81.4% |
| 12 mg | -82.4% |
All retatrutide doses achieved statistically significant reductions relative to placebo (P less than 0.001). At the two highest doses, more than 90% of participants with baseline NAFLD/MASLD achieved liver fat normalization based on MRI-PDFF assessments.
This magnitude of liver fat reduction is exceptional compared to other compounds studied in MASLD to date and is hypothesized to reflect the combined contribution of weight loss, reduced hepatic lipogenesis, and direct glucagon-receptor-mediated increases in hepatic fat oxidation.
9.2 Cardiometabolic Markers
The Phase 2 type 2 diabetes trial also reported meaningful improvements in lipid parameters. Reductions in triglycerides and non-HDL cholesterol were observed alongside the glycemic and weight outcomes. Systolic blood pressure improvements were noted as well, consistent with findings observed across the incretin class.
These cardiometabolic effects are the subject of ongoing investigation in the TRIUMPH outcomes trials.
10. Regulatory Status and FDA Compliance Notes
Retatrutide is an investigational compound. It has not been approved by the U.S. Food and Drug Administration (FDA) or by the European Medicines Agency (EMA) for any therapeutic indication.
Eli Lilly holds an active Investigational New Drug (IND) application for retatrutide and is conducting clinical trials under this authorization as part of the TRIUMPH Phase 3 program.
Palmetto Peptides supplies retatrutide as a research chemical for in vitro and laboratory research purposes only. Our products are:
- Not for human use
- Not for veterinary use
- Not for diagnostic purposes
- Not for therapeutic or cosmetic applications
- Intended exclusively for qualified researchers conducting legitimate in vitro studies in a laboratory setting
All Palmetto Peptides products are manufactured to research-grade specifications and are accompanied by certificates of analysis confirming purity. We do not provide any guidance on, or support for, administration of any peptide in any non-research context.
Researchers purchasing retatrutide for laboratory use should ensure they are operating within applicable federal, state, and local regulations governing the acquisition, handling, and use of research chemicals.
11. How to Handle and Store Retatrutide for Research
Proper handling is critical to maintaining the integrity of peptide research materials. Retatrutide, like most synthetic peptides, is sensitive to degradation under improper conditions.
11.1 Storage Recommendations
Retatrutide should be stored lyophilized (freeze-dried) at or below -20°C in a dry, dark environment. The powder form is significantly more stable than reconstituted solution. Once reconstituted, solutions should be aliquoted promptly to avoid repeated freeze-thaw cycles, which can accelerate degradation.
For reconstitution in laboratory settings, sterile diluents compatible with the research application should be selected. Researchers should refer to the certificate of analysis and product-specific documentation provided with each lot.
11.2 Handling Precautions
When working with any synthetic peptide research material, standard laboratory safety practices apply. Use appropriate personal protective equipment. Avoid prolonged exposure to moisture and heat during handling. Dispose of materials in accordance with institutional and regulatory guidelines.
11.3 Stability Considerations
The lipid chain conjugation (C20 fatty diacid) in retatrutide makes it somewhat more hydrophobic than simpler linear peptides. This should be considered when selecting solvents and formulating solutions for in vitro assays.
Palmetto Peptides provides detailed handling documentation with each order. Contact our research support team with any technical questions specific to your research application.
12. Related Research Peptides
Researchers studying metabolic hormone receptors, obesity mechanisms, or liver disease may find several other peptides in our catalog relevant to their work. These compounds represent related or complementary tools for comparative or mechanistic studies.
GLP-1 Receptor Agonist Peptides: For studies focusing specifically on the GLP-1 pathway without the added complexity of GIP or glucagon receptor activity. See our GLP-1 Research Peptide Collection.
GIP Receptor Research Tools: For isolating GIP receptor-specific mechanisms in metabolic and adipose tissue research. See our GIP Peptide products.
Tirzepatide (Research Grade): Useful as a dual GIP/GLP-1 agonist comparator when studying the incremental effect of glucagon receptor addition in triple agonist research. See our Tirzepatide Research Peptide page.
Semaglutide (Research Grade): The single-receptor GLP-1 agonist benchmark for incretin research comparisons. See our Semaglutide Research Peptide page.
Glucagon Peptide: Native glucagon for use as a reference standard or positive control in GCGR assays. See our Glucagon Research Peptide page.
Cotadutide (Research Grade): A GLP-1/glucagon dual agonist (without GIP activity) useful for dissecting the GIP contribution in triple agonist models. See our Cotadutide product page.
Palmetto Peptides also publishes supporting research articles on retatrutide. Explore the full cluster below:
- What Is Retatrutide Research Peptide?
- How Retatrutide Works: The Triple-Action Mechanism
- Retatrutide Animal Studies and Research Updates
- Retatrutide vs Tirzepatide: Research Peptide Comparison
- Retatrutide vs Semaglutide: Research Peptide Comparison
- How to Reconstitute Retatrutide Research Peptide
- How to Store Retatrutide Research Peptide
- Retatrutide Research Dosages in Published Studies
- How to Check Purity When Buying Retatrutide
- Where to Buy Retatrutide Research Peptide in 2026
- Retatrutide Research Peptide Cost Guide
- Before Ordering Retatrutide Research Peptide Online
13. Frequently Asked Questions
Q: What is retatrutide? Retatrutide (LY3437943) is a synthetic 39-amino-acid peptide that functions as a simultaneous agonist of three hormone receptors: GIPR, GLP-1R, and GCGR. It is the first triple incretin receptor agonist to advance through Phase 2 and into Phase 3 clinical trials. It remains investigational and is not approved for any therapeutic use.
Q: Is retatrutide FDA approved? No. As of March 2026, retatrutide is not FDA approved. It is being evaluated in Phase 3 clinical trials under Eli Lilly's TRIUMPH program. It is available for licensed laboratory research use only.
Q: How does retatrutide differ from semaglutide and tirzepatide? Semaglutide activates one receptor (GLP-1R). Tirzepatide activates two (GIP and GLP-1). Retatrutide activates all three, adding glucagon receptor engagement, which is hypothesized to increase hepatic fat oxidation and energy expenditure beyond what dual agonism achieves.
Q: What clinical data exists for retatrutide? Published Phase 2 data appears in the New England Journal of Medicine (2023), The Lancet (2023), and Nature Medicine (2024). Phase 3 trial data began emerging in 2025 with positive topline results from the TRIUMPH-4 knee osteoarthritis study.
Q: What does retatrutide's receptor binding profile look like? In published in vitro assays, retatrutide binds human GIPR with an EC50 of approximately 0.064 nM, GLP-1R at approximately 0.775 nM, and GCGR at approximately 5.79 nM.
Q: What were the Phase 2 weight loss results? In the Phase 2 obesity trial, the 12 mg dose produced a mean 24.2% reduction in body weight at 48 weeks, compared to 2.1% with placebo. At the 8 mg dose, mean weight reduction was 22.8% at 48 weeks. These were Phase 2 findings in a controlled research population and should not be extrapolated as predictive of outcomes outside that context.
Q: What were the liver fat findings? In a Phase 2 substudy published in Nature Medicine (2024), retatrutide at 8 mg and 12 mg doses produced approximately 81 to 82% relative reductions in liver fat content at 24 weeks in participants with MASLD.
Q: Can researchers buy retatrutide from Palmetto Peptides? Yes, Palmetto Peptides supplies retatrutide as a research-grade peptide for qualified researchers conducting in vitro laboratory studies. It is sold strictly for research purposes and not for human or veterinary use. Visit our Retatrutide product page for current availability and specifications.
Q: What is the molecular weight of retatrutide? Retatrutide has a molecular weight of approximately 4,731 Da (free base form), with the CAS registry number 2381089-83-2.
Q: What adverse events were observed in Phase 2 trials? The most common adverse events were gastrointestinal, including nausea, diarrhea, vomiting, and constipation. These were dose-dependent and generally mild to moderate. Discontinuations due to adverse events ranged from 6 to 16% across dose groups.
14. Peer-Reviewed Citations
The following peer-reviewed and primary sources were referenced in the preparation of this article. Researchers are encouraged to consult original publications for complete methodological detail.
-
Coskun T, Urva S, Roell WC, Qu H, Loghin C, Moyers JS, 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;34(9):1234-1247.e9. https://doi.org/10.1016/j.cmet.2022.08.007
-
Jastreboff AM, Kaplan LM, Frías JP, Wu Q, Du Y, Gurbuz S, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity -- A Phase 2 Trial. New England Journal of Medicine. 2023;389(6):514-526. https://doi.org/10.1056/NEJMoa2301972
-
Rosenstock J, Frias J, Jastreboff AM, Du Y, Lou J, Gurbuz S, 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;402(10401):529-544. https://doi.org/10.1016/S0140-6736(23)01053-X
-
Sanyal AJ, Bedossa P, Fraessdorf M, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nature Medicine. 2024;30:2037-2048. https://doi.org/10.1038/s41591-024-03018-2
-
Urva S, Coskun T, Loh MT, Du Y, Thomas MK, Gurbuz S, et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. The Lancet. 2022;399(10326):1869-1881. https://doi.org/10.1016/S0140-6736(22)00682-3
-
Rajagopal S, Bhardwaj G, Jain A, Bhardwaj V, Siddiqui SA, Ahlawat A. Efficacy and safety of retatrutide, a novel GLP-1, GIP, and glucagon receptor agonist for obesity treatment: a systematic review and meta-analysis of randomized controlled trials. Baylor University Medical Center Proceedings. 2025;38(3):291-303. https://doi.org/10.1080/08998280.2025.2456441
-
Liu Q, Yang D, Zhuang Y, Croll TI, Cai X, Dai A, et al. Structural insights into the triple agonism at GLP-1R, GIPR and GCGR manifested by retatrutide. Cell Discovery. 2024;10:72. https://doi.org/10.1038/s41421-024-00700-0
-
Lautenbach A, Gonnermann A, Blüher M. Triple Agonism Based Therapies for Obesity. Current Cardiovascular Risk Reports. 2025. https://doi.org/10.1007/s12170-025-00770-z
-
Eli Lilly and Company. Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial. Investor Relations Press Release. 2025. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average
Disclaimer (Repeated for Compliance): Retatrutide is an investigational research peptide. It is not approved by the FDA or any other regulatory authority for therapeutic use in humans or animals. All products offered by Palmetto Peptides are for in vitro laboratory research only. Nothing in this article constitutes medical advice, a treatment recommendation, or an endorsement of self-administration. Researchers are responsible for ensuring their use of research chemicals complies with all applicable laws and institutional regulations.
Article prepared by the Palmetto Peptides Research Team.**
Last Updated: March 19, 2026