Eli Lilly’s retatrutide clinical trials have produced significant new findings in 2026, including Phase 3 results involving obesity, type 2 diabetes, knee osteoarthritis, and obstructive sleep apnea. The most recent peer-reviewed study, published on November 8, 2026, reported additional evidence from the TRIUMPH-4 and TRIUMPH-1-OA trials, examining changes in knee pain and body weight.
Retatrutide, also identified as LY3437943, is an investigational peptide developed by Eli Lilly. It activates three hormone receptors: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon.
This triple-receptor mechanism distinguishes retatrutide from many other compounds investigated in metabolic research.
Earlier Phase 2 investigations reported mean body-weight reductions of up to 24.2% over 48 weeks. More recent Phase 3 studies have expanded the evidence base, including research examining metabolic outcomes, cardiovascular risk factors, and obesity-related complications.
However, retatrutide remains investigational and is not FDA-approved as of November 10, 2026.
This article reviews the latest Eli Lilly retatrutide trials, their reported findings, research limitations, and ongoing studies, with direct links to published scientific papers and official trial registrations.
Latest Retatrutide Study: November 8, 2026
TRIUMPH-4 and TRIUMPH-1-OA — Knee Osteoarthritis and Obesity
Study published: November 8, 2026
Journal: New England Journal of Medicine
Study title: Retatrutide Once Weekly in Adults with Knee Osteoarthritis Pain and Obesity
Study link: https://doi.org/10.1056/NEJMoa2610676
The newest peer-reviewed publication reports findings from two Phase 3 trials investigating retatrutide in adults with obesity or overweight and symptomatic knee osteoarthritis.
Researchers evaluated both body-weight changes and knee pain using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
The two studies included:
- TRIUMPH-4: 445 randomized participants.
- TRIUMPH-1-OA: 574 randomized participants.
In TRIUMPH-4, researchers assessed outcomes at 68 weeks.
The study reported mean changes in the WOMAC pain score of approximately:
| Study group | Change in WOMAC pain score |
|---|---|
| Retatrutide 9 mg | −3.96 points |
| Retatrutide 12 mg | −3.74 points |
| Placebo | −2.12 points |
Both retatrutide groups demonstrated statistically greater reductions in reported pain than the placebo group.
The publication also reported significant reductions in body weight.
These findings add to the understanding of retatrutide’s effects in people with obesity-related complications. However, the results do not establish whether observed knee-pain improvements arise primarily from weight reduction or additional biological mechanisms.
Original publication: NEJM — Retatrutide and Knee Osteoarthritis, November 2026
Clinical trial: TRIUMPH-4 — NCT05931367
October 28, 2026: Retatrutide Compared With Semaglutide
TRANSCEND-T2D-2 Phase 3 Trial
On October 28, 2026, Eli Lilly announced results from TRANSCEND-T2D-2, a Phase 3 study comparing investigational retatrutide with injectable semaglutide 2 mg, marketed as Ozempic.
The study enrolled 1,298 adults with type 2 diabetes.
At 80 weeks, the company reported the following results:
| Outcome | Retatrutide 9 mg | Retatrutide 12 mg | Semaglutide 2 mg |
|---|---|---|---|
| Mean A1C reduction | 2.2 percentage points | 2.2 percentage points | 1.8 percentage points |
| Mean body-weight reduction | 19.5% | 20.9% | 9.4% |
These were results under the trial’s efficacy estimand, which estimates outcomes under specified treatment-continuation conditions.
Retatrutide achieved statistically greater improvements on several measured outcomes, including changes in body weight.
The company also reported gastrointestinal adverse events, including diarrhea, nausea, constipation, and vomiting.
Importantly, these findings were announced in a company press release. As of November 10, 2026, the detailed peer-reviewed results had not yet been published.
Official announcement: Eli Lilly — TRANSCEND-T2D-2 Results, October 28, 2026
Clinical trial: TRANSCEND-T2D-2 — NCT06260722
October 2026: Retatrutide and Obstructive Sleep Apnea
A peer-reviewed study published online in October 2026 examined retatrutide in adults with moderate-to-severe obstructive sleep apnea and obesity or overweight.
The research included two Phase 3 populations:
- TRIUMPH-1-OSA: 243 randomized participants without type 2 diabetes.
- TRIUMPH-2-OSA: 448 randomized participants with type 2 diabetes.
Researchers measured changes in the apnea–hypopnea index, or AHI, which represents the frequency of breathing interruptions during sleep.
Across both trials, retatrutide groups showed significantly greater reductions in AHI than placebo groups at 80 weeks.
For example, in TRIUMPH-1-OSA, the reported mean AHI reduction was 34.3 events per hour in the 9 mg retatrutide group, compared with 9.9 events per hour in the placebo group.
The researchers also observed substantial body-weight reductions.
These results expand the clinical evidence involving metabolic health and obesity-associated conditions.
Published study: NEJM — Retatrutide for Obstructive Sleep Apnea
Trial registrations: TRIUMPH-1 and TRIUMPH-2
TRIUMPH-1: Phase 3 Retatrutide Obesity Trial
Published online: September 29, 2026
Journal: New England Journal of Medicine
TRIUMPH-1 is one of Eli Lilly’s central Phase 3 studies investigating retatrutide in adults with obesity without diabetes.
The randomized, double-blind trial evaluated retatrutide over 80 weeks.
According to results presented by Eli Lilly in June 2026, participants assigned to the 12 mg group experienced an average body-weight reduction of approximately 28.3% under the reported efficacy analysis.
The peer-reviewed publication subsequently provided detailed information about the study’s endpoints, statistical methods, and safety findings.
These results represent a longer observation period than the original 48-week Phase 2 obesity trial.
The reported reductions in weight are clinically notable, but interpretation depends on the trial population, endpoint definitions, and follow-up period.
Published study: NEJM — TRIUMPH-1 Phase 3 Obesity Trial
Registration: NCT05929066
TRIUMPH-2: Retatrutide in Adults With Obesity and Type 2 Diabetes
Published online: September 29, 2026
Journal: The Lancet
TRIUMPH-2 evaluated retatrutide in adults with obesity or overweight and type 2 diabetes.
The study investigated both changes in body weight and glycemic measurements.
Eli Lilly reported mean weight reductions after 80 weeks of approximately:
- 12.7% in the 4 mg group.
- 19.1% in the 9 mg group.
- 20.8% in the 12 mg group.
The company also reported mean A1C reductions of up to 1.6 percentage points.
These results are relevant because researchers have been evaluating whether triple-receptor agonism produces distinct metabolic effects in populations with type 2 diabetes.
The peer-reviewed publication discusses the study design, statistical evaluation, and adverse-event profile.
Published study: The Lancet — TRIUMPH-2 Phase 3 Trial
PubMed: https://pubmed.ncbi.nlm.nih.gov/42810372/
Registration: NCT05929079
The Original 2023 Retatrutide Phase 2 Trial
The Study That Established Early Clinical Interest
Before the Phase 3 TRIUMPH program, Eli Lilly conducted a Phase 2 obesity trial involving 338 randomized adults.
The findings were published in the New England Journal of Medicine in June 2023.
The study evaluated changes in body weight over 48 weeks.
The highest investigated group reported a mean body-weight reduction of 24.2% at 48 weeks, compared with approximately 2.1% in the placebo group.
The results generated considerable scientific interest in the pharmacology of simultaneous GIP, GLP-1, and glucagon receptor activation.
Researchers also identified adverse events, particularly gastrointestinal symptoms, and observed dose-related changes in heart rate.
These early findings provided the foundation for larger Phase 3 trials.
Published study: NEJM — Triple-Hormone-Receptor Agonist Retatrutide for Obesity
Registration: NCT04881760
2023 Phase 2 Trial: Retatrutide and Type 2 Diabetes
Eli Lilly also investigated retatrutide in adults with type 2 diabetes through a randomized Phase 2 study.
Published in The Lancet in 2023, the research evaluated glycemic responses, weight-related outcomes, and safety.
The study compared investigational retatrutide groups with placebo and an active comparator.
Researchers observed improvements in measures of glycemic control and body weight across selected treatment groups.
The findings supported further investigation in adults with type 2 diabetes.
However, Phase 2 evidence alone is not sufficient to establish long-term safety or regulatory approval.
Published study: The Lancet — Retatrutide in Type 2 Diabetes
PubMed: https://pubmed.ncbi.nlm.nih.gov/37385280/
2024 Retatrutide Trial: Liver Fat and Metabolic Research
Another important study examined retatrutide in participants with metabolic dysfunction-associated steatotic liver disease (MASLD).
Published in Nature Medicine in June 2024, the Phase 2a substudy included 98 randomized participants.
Researchers used imaging-based measurements to evaluate changes in liver fat.
At 24 weeks, the study reported mean relative liver-fat reductions of 81.4% and 82.4% in the 8 mg and 12 mg groups, respectively, compared with an approximately 0.3% increase in the placebo group.
These findings concerned relative changes in liver-fat measurements, not the proportion of participants cured of liver disease.
The study provided an early indication that retatrutide’s metabolic effects may extend beyond body-weight regulation.
Additional investigation is necessary to understand long-term liver outcomes and clinical significance.
Published study: Nature Medicine — Retatrutide and Liver Fat Research
Registration: NCT04881760
What Are the Side Effects Reported in Eli Lilly Retatrutide Trials?
Across Phase 2 and Phase 3 investigations, the most frequently observed adverse events have generally involved the gastrointestinal system.
Reported events include nausea, diarrhea, vomiting, constipation, and reduced appetite.
Other findings being studied include changes in heart rate, dysesthesia or unusual skin sensations, and cardiovascular or metabolic safety parameters.
The frequency of adverse events varies across trials and populations.
For example, the October 2026 TRANSCEND-T2D-2 announcement reported diarrhea in 28.3% and 32.7% of participants assigned to the two retatrutide groups, compared with 26.4% in the semaglutide group.
Discontinuation due to adverse events occurred in 4.8% and 7.9% of participants receiving retatrutide, compared with 2.7% receiving semaglutide.
These results should not be generalized to all patients or research settings.
For additional information, read our article on Reta Peptide Side Effects.
What Retatrutide Trials Are Still Ongoing in 2026?
Eli Lilly continues investigating retatrutide across several indications.
Important registered studies include:
| Trial | Research focus | ClinicalTrials.gov |
|---|---|---|
| TRIUMPH-3 | Obesity and cardiovascular disease | NCT05882045 |
| TRIUMPH-5 | Comparison with tirzepatide | NCT06662383 |
| TRIUMPH-6 | Maintenance of weight reduction | NCT06859268 |
| TRIUMPH-7 | Obesity and chronic low back pain | NCT07035093 |
| TRIUMPH-8 | Additional obesity research | NCT07232719 |
| TRIUMPH-9 | Long-term obesity research | NCT07357415 |
| TRIUMPH-OUTCOMES | Cardiovascular and kidney outcomes | NCT06383390 |
| TRANSCEND-T2D-3 | Diabetes and kidney impairment | NCT06297603 |
Individual study statuses can change, and investigators may update trial records as recruitment, follow-up, and analysis progress.
Researchers should consult the linked ClinicalTrials.gov pages for the latest official status.
When Will Eli Lilly Retatrutide Receive FDA Approval?
As of November 10, 2026, retatrutide is not FDA-approved.
In July 2026, Eli Lilly announced plans to submit a regulatory application to the FDA in the first quarter of 2027.
This reflects the company’s stated development intentions, not an FDA approval decision or a guaranteed submission date.
Regulatory review will depend on the evidence submitted, the proposed indication, manufacturing information, and applicable regulatory requirements.
Even positive Phase 3 trial results do not automatically establish that a medicine will be approved.
Source: Eli Lilly — July 2026 Phase 3 and Regulatory Update
Retatrutide Research and Neuro Peptide
At Neuro Peptide, our educational resources examine the molecular and biological properties of peptides studied in scientific research.
Retatrutide is particularly relevant to investigations of receptor signaling, metabolic pathways, peptide structure, and molecular pharmacology.
Researchers can explore our Retatrutide research compound information and educational guides.
It is important to distinguish laboratory research materials from the pharmaceutical investigational product supplied to participants in Eli Lilly’s clinical trials.
Commercial research compounds are not demonstrated to be equivalent to Eli Lilly’s investigational formulations, and the clinical results described here cannot be assumed to apply to research-grade products from other suppliers.
Neuro Peptide products are intended strictly for lawful laboratory research and are not for human or veterinary use.
Frequently Asked Questions
What is the latest Eli Lilly retatrutide trial?
The most recent peer-reviewed retatrutide study identified as of November 10, 2026, was published on November 8, 2026, in the New England Journal of Medicine. It reported findings from Phase 3 trials involving knee osteoarthritis and obesity.
What are the latest retatrutide Phase 3 results?
Recent findings include the November 2026 knee osteoarthritis publication, October 2026 obstructive sleep apnea research, and Eli Lilly’s October 28 announcement comparing retatrutide with semaglutide in adults with type 2 diabetes.
How much weight loss occurred in retatrutide clinical trials?
Results differ by population, follow-up period, and statistical approach. In the Phase 2 obesity trial, the highest investigated group reported an average reduction of 24.2% at 48 weeks. Eli Lilly later reported average reductions as high as 28.3% in the Phase 3 TRIUMPH-1 trial under its efficacy analysis.
Is retatrutide better than semaglutide?
In the specific TRANSCEND-T2D-2 trial, Eli Lilly reported greater mean A1C and body-weight reductions with retatrutide than with semaglutide 2 mg at 80 weeks. These findings do not establish overall superiority for every clinical outcome or patient population.
Is retatrutide FDA-approved?
No. Retatrutide remains investigational as of November 2026. It has not received FDA approval for human use.
Where can researchers find official retatrutide studies?
Published results are available through journals such as the New England Journal of Medicine, The Lancet, and Nature Medicine. Registered studies can also be found through ClinicalTrials.gov by searching for retatrutide or LY3437943.
Conclusion: What Eli Lilly’s Retatrutide Trials Reveal in 2026
Eli Lilly’s retatrutide clinical development program has progressed significantly from its early Phase 2 studies to multiple large Phase 3 trials.
The latest publications provide evidence involving body-weight reduction, glycemic control, knee osteoarthritis pain, and obstructive sleep apnea.
The November 8, 2026 study is particularly important because it adds peer-reviewed findings concerning obesity and knee osteoarthritis.
However, important questions remain regarding long-term safety, cardiovascular outcomes, and the implications of sustained triple-receptor activation.
Future peer-reviewed publications, ongoing clinical trials, and regulatory decisions will help clarify the potential clinical role of retatrutide.
For more educational information about peptide structure, molecular mechanisms, and laboratory research, explore Neuro Peptide.
Scientific disclaimer: This article is intended for educational and research-information purposes only. Retatrutide remains an investigational drug and is not approved for human use. Clinical-trial results concern investigational pharmaceutical formulations and do not establish the safety, effectiveness, or equivalence of commercially available research compounds. This content does not provide medical advice or dosing recommendations.