Retatrutide research now includes published randomized human trials, including phase 3 results released in September 2026. Understanding those findings means matching the exact investigational material, participant population, endpoint and statistical analysis. Results from a clinical trial do not authenticate a catalog vial or establish its suitability for human use.
Scope: This guide summarizes selected original trial publications and official trial records. It is an evidence-reading guide, not a systematic review or a preparation, injection or personal-use protocol. Sources and United States regulatory information were checked on October 10, 2026.
What is retatrutide, and what does “GLP-3” mean?
Retatrutide, also identified as LY3437943, is a single investigational peptide that acts at three receptor systems: GIP, GLP-1 and glucagon. It is different from the naturally occurring GLP-1 hormone and from tirzepatide. A three-receptor mechanism does not mean it is a mixture of three peptides. The original obesity trial describes its identity and receptor targets.
Some catalog entries on this site use “GLP-3 (Retatrutide)” as a product label. When searching the scientific literature, use retatrutide or LY3437943 and match the study’s actual material. The catalog label does not establish an official hormone class, pharmaceutical equivalence or regulatory approval.
What the published human trials found
The numbers below describe specific trial groups and analyses. They are not predictions for an individual, comparisons of sellers, or dosing recommendations. “12 mg study arm” identifies the reported experimental group; it does not turn a vial’s total labeled quantity into a treatment schedule.
| Trial and population | Design and endpoint | Selected reported result |
|---|---|---|
| 2023 obesity phase 2 trial: 338 adults with obesity or overweight and a related condition; diabetes excluded | Randomized, blinded, placebo-controlled. Weight change at 24 weeks was the primary endpoint; 48-week weight change was secondary. | At 48 weeks, the 12 mg study arm had an estimated mean weight change of −24.2%, compared with −2.1% for placebo. These were least-squares means from the specified analysis. |
| 2023 type 2 diabetes phase 2 trial: 281 randomized participants | Blinded trial with placebo and an active dulaglutide comparator. The primary endpoint was HbA1c change at 24 weeks. | The 12 mg study arm’s estimated HbA1c change was −2.02 percentage points, compared with −0.01 for placebo and −1.41 for the specified dulaglutide group. This glucose-control endpoint differs from a weight endpoint. |
| TRIUMPH-1, published September 2026: the paper reports 2,339 randomized adults with obesity without diabetes | Phase 3, randomized, blinded, placebo-controlled; 80 weeks. Weight outcomes used a treatment-regimen, intention-to-treat approach. | Mean weight change was −25.0% in the 12 mg study arm and −3.9% with placebo. The paper also reports knee-pain and sleep-apnea outcomes in defined subgroups. |
| TRIUMPH-2, published September 2026: 1,152 adults with obesity or overweight and type 2 diabetes | Phase 3, randomized, blinded, placebo-controlled; 80-week weight endpoint using a treatment-regimen estimand and missing-data imputation. | Mean weight change was −18.8% in the 12 mg study arm and −5.1% with placebo. The population and background diabetes treatment differ from TRIUMPH-1. |
What does the newer retatrutide sleep apnea paper add?
Primary abstract checked October 22, 2026; this is an abstract-level update.
Grunstein and colleagues' October 2026 sleep-apnea report describes two randomized, blinded, placebo-controlled groups nested within the larger TRIUMPH trials. Participants had moderate-to-severe obstructive sleep apnea and a body-mass index of at least 27.
| Group | Randomized participants | Registry identifier |
|---|---|---|
| TRIUMPH-1-OSA, without type 2 diabetes | 243 | NCT05929066 |
| TRIUMPH-2-OSA, with type 2 diabetes | 448 | NCT05929079 |
The primary outcome was change in the apnea–hypopnea index, measured in events per hour, at 80 weeks. The authors report greater reductions with retatrutide than placebo and report both hybrid-treatment and intention-to-treat analyses. Those analyses should remain distinct. Gastrointestinal events were the most common adverse events reported in the abstract.
A new publication is not automatically a new independent trial. These registry identifiers also appear in the broader TRIUMPH publications above. Keep a publication's DOI separate from its trial identifier and participant group; do not count the same nested participants twice when describing the evidence base.
For a reusable reading record, note trial identifier → participant group → endpoint and timeframe → analysis → publication. A missing registry results table and a missing journal paper are different questions: see Why can't I find results for a peptide clinical trial? The regulatory-status section remains separate from study findings, which do not authenticate a catalog product.
How to compare the results without overstating them
Keep the population beside the percentage. An obesity trial excluding diabetes and a trial enrolling people with type 2 diabetes answer different questions. Neither is a randomized comparison between those populations. A larger percentage in one paper does not show that every person, formulation or setting will produce that result.
Read the analysis, not only the headline. An estimand defines which treatment effect the researchers are trying to estimate, including how they handle events such as treatment discontinuation. TRIUMPH-1 reports an intention-to-treat approach for weight outcomes and a different hybrid approach for certain subgroup outcomes. Percentages obtained under different analyses should not be exchanged as if they were the same number. Read the published TRIUMPH-1 methods and results.
Compare outcomes in their own units. Percentage change in body weight, percentage-point change in HbA1c, a knee-pain score and apnea events per hour measure different things. Positive findings for one endpoint do not establish improvement in every outcome. This guide uses the published abstract results; the full papers and supplements provide fuller details on eligibility, missing data and adverse events.
Safety findings are part of the evidence
The 2023 obesity trial reported gastrointestinal adverse events and dose-related heart-rate increases. The original phase 2 paper should be read alongside its weight results, rather than treating weight reduction as a complete safety assessment.
In TRIUMPH-2, gastrointestinal events were more frequent with retatrutide than placebo. The publication also reports hypotension, altered sensation described as dysesthesia, and treatment discontinuations. Read the trial’s safety findings and denominators. A selected trial with monitored participants cannot settle every uncommon or longer-term risk.
Does this establish superiority over tirzepatide?
Comparing percentages from separate trials cannot establish head-to-head superiority. Participant selection, follow-up, comparator treatment and handling of missing data may differ. The registered TRIUMPH-5 trial, NCT06662383, directly compares retatrutide with tirzepatide in adults with obesity. At our October 10, 2026 check, the registry listed it as active but not recruiting, with no results posted. That dated registry status is not a comparative result.
Registry results and journal publications update independently. TRIUMPH-1 and TRIUMPH-2 already have the published papers linked above; the absence of a results table on a registry page does not mean no paper exists. Match the trial identifier and the publication before drawing a conclusion.
United States regulatory status
At the October 10, 2026 source check, the FDA’s current guidance states that retatrutide is not a component of an FDA-approved drug and cannot be used in compounding under federal law. Published trial results and an FDA approval are separate milestones. A research-only label does not turn a material into an approved medicine.
What a catalog label or laboratory report can establish
A clinical trial uses the investigational material, manufacturing controls, formulation and study procedures specified in its protocol. A similarly named laboratory-research product is not automatically that clinical material. The trial papers do not test, endorse or verify Peptide Serum inventory.
For product-document review, connect the exact product and lot to the available report, identify the submitted sample, and read the methods and units. Identity, a chromatographic purity percentage, measured quantity, sterility and endotoxin address different questions. A result for one test should not be treated as an answer to all of them.
See how to read a peptide certificate of analysis and available laboratory documentation. Store products are intended for in-vitro laboratory research only, not human or veterinary use.
Original publications and trial records
All four selected trial publications disclose Eli Lilly funding. This guide links original reports and official records so readers can inspect the underlying findings and their scope.
- Jastreboff and colleagues, 2023 obesity phase 2 trial. PubMed 37366315; original journal paper; NCT04881760.
- 2023 type 2 diabetes phase 2 trial. PubMed 37385280; original journal paper.
- TRIUMPH-1, published September 29, 2026. PubMed 42814954; original journal paper; NCT05929066.
- TRIUMPH-2, published September 29, 2026. PubMed 42810372; original journal paper; NCT05929079.
- Retatrutide versus tirzepatide comparison: TRIUMPH-5, NCT06662383, registry checked October 10, 2026.
Continue reading
Use the peptide research library, metabolic and weight-loss research guide, tirzepatide evidence profile, and preclinical versus human evidence guide to compare research questions, materials and study designs.