TRIUMPH-1 Phase 3: Retatrutide 80-Week Obesity Trial Data (2026)
TL;DR: TRIUMPH-1 (n=2,339, 80 wks) reported 28.3% body-weight reduction on retatrutide 12mg vs 2.2% placebo; Lilly targets NDA filing Q4 2026.
What is TRIUMPH-1?
TRIUMPH-1 is the pivotal Phase 3 clinical trial evaluating retatrutide (LY3437943, Eli Lilly) in adults with obesity or overweight without type 2 diabetes. It is the primary obesity-focused arm of Lilly's broader TRIUMPH Phase 3 programme, which also includes trials in type 2 diabetes (TRANSCEND-T2D-1), knee osteoarthritis (TRIUMPH-4), and cardiovascular outcomes (TRIUMPH-3).[1]
Topline results from TRIUMPH-1 were announced by Eli Lilly on 21 May 2026. Full data were presented at the American Diabetes Association (ADA) 86th Scientific Sessions in New Orleans on 6 June 2026, alongside companion data from TRANSCEND-T2D-1 (type 2 diabetes) and pre-specified subgroup analyses covering obstructive sleep apnea and knee osteoarthritis.[2] Peer-reviewed publication is expected to follow, consistent with the precedent set by Phase 2 data appearing in the New England Journal of Medicine in 2023.
Everything in this document summarises what the trial reported. It is third-party scientific reference only — not a description of any effect of Velox Peptides products, which are supplied as research reagents for in vitro laboratory use.
Who Did TRIUMPH-1 Enrol?
TRIUMPH-1 enrolled 2,339 adults with obesity (BMI ≥30 kg/m²) or overweight (BMI 27–30 kg/m²) plus at least one weight-related comorbidity (such as hypertension, dyslipidaemia, or obstructive sleep apnea), and without type 2 diabetes.[1][2] The exclusion of type 2 diabetes is an important design feature: glycaemic effects in a non-diabetic cohort are a separate research question from those studied in TRANSCEND-T2D-1.
Participants were randomised 1:1:1:1 to receive once-weekly subcutaneous injections of retatrutide 4 mg, 9 mg, 12 mg, or placebo. The dose figures are stated here only as facts of the trial design — not as guidance. A 104-week extension subgroup continued for additional follow-up after the primary 80-week assessment, with data reported for participants with a baseline BMI of ≥35 kg/m².[3]
The trial was designed and sponsored by Eli Lilly and Company. The TRIUMPH programme rationale and design were published in Diabetes, Obesity and Metabolism (Giblin et al., 2026), providing the pre-specified statistical framework against which these topline results are assessed.[1]
What Did the Primary Endpoint Measure?
The primary endpoint of TRIUMPH-1 was mean percentage change in body weight from baseline at 80 weeks. This is the standard endpoint used in regulatory obesity trials, also used in the semaglutide STEP programme and the tirzepatide SURMOUNT programme, enabling broad cross-programme comparison in the published literature (though direct cross-trial comparison is limited by different participant populations and timepoints).
Key secondary endpoints included: the proportion of participants achieving ≥5%, ≥10%, ≥15%, and ≥20% body-weight reduction; and changes in cardiometabolic risk biomarkers including triglycerides, non-HDL cholesterol, systolic blood pressure, and waist circumference. Pre-specified subgroup analyses covered participants with moderate-to-severe obstructive sleep apnea and those with knee osteoarthritis, reported as separate analyses at ADA 2026 and detailed in companion guides linked below.[2]
What Did TRIUMPH-1 Report for Body-Weight Reduction?
At 80 weeks, TRIUMPH-1 reported the following mean body-weight reductions by dose arm versus placebo:[2][3]
| Dose arm | Mean body-weight reduction (80 wks) | vs Placebo (−2.2%) |
|---|---|---|
| Retatrutide 4 mg | −19.0% | +16.8 pp |
| Retatrutide 9 mg | −25.9% | +23.7 pp |
| Retatrutide 12 mg | −28.3% | +26.1 pp |
| Placebo | −2.2% | — |
All three active dose arms met both the primary and key secondary endpoints for weight reduction at 80 weeks.[2] For context, the Phase 2 trial (Jastreboff et al., NEJM, 2023) had reported up to ~24% weight reduction at 48 weeks in a 338-participant trial — TRIUMPH-1 extends that observation across a larger, longer, more definitive Phase 3 design.[4]
What Secondary Endpoints Did TRIUMPH-1 Report?
Beyond the primary weight endpoint, TRIUMPH-1 reported a range of cardiometabolic secondary endpoints at 80 weeks on the 12 mg dose. These are presented here as published trial findings, for research reference only. They are not claims about Velox Peptides products or any expected outcome.[2]
| Secondary Endpoint | Retatrutide 12mg (reported change) |
|---|---|
| Triglycerides | −41.0% |
| Non-HDL cholesterol | −24.2% |
| Systolic blood pressure | −12.3 mmHg |
| Waist circumference | −9.5 in (−24.1 cm) |
| High-sensitivity CRP (hsCRP) | Significant reduction reported |
| AHI (OSA subgroup, 12mg) | −60.6% (−36.1 events/h) |
The cardiometabolic biomarker findings align with the expected profile of significant weight reduction combined with glucagon receptor agonism, which in animal models has been associated with increased hepatic fat oxidation and energy expenditure independently of weight loss. TRIUMPH-3, the dedicated cardiovascular outcomes trial, is designed to assess hard cardiovascular endpoints and is reporting later in 2026.[1]
The sleep apnea subgroup data (AHI reduction of 60.6% at 80 weeks on 12mg) was presented separately at ADA 2026 and is examined in detail in our companion guide: Retatrutide & Obstructive Sleep Apnea: TRIUMPH-1 Phase 3 Subgroup Data.
What Did the 104-Week Extension Report?
A pre-specified extension of TRIUMPH-1 continued follow-up to 104 weeks in a subgroup of participants with a baseline BMI of ≥35 kg/m². In this subgroup, those receiving retatrutide 12 mg reported an average body-weight reduction of 30.3%, equivalent to an average of approximately 85 lbs (38.6 kg).[3]
The 104-week result is notable for two reasons as a research observation: first, it suggests the weight-reduction trajectory had not yet plateaued at 80 weeks, which is a different kinetic profile from some earlier GLP-1 class compounds; second, the 30.3% figure approaches the range typically associated with bariatric surgical interventions in published registry data — a comparison that is frequently made in the clinical research literature for context, not as a treatment claim.[3]
Peer-reviewed publication of these data (full methods, per-protocol analysis, and confidence intervals) is pending and will provide more granular insight into response distribution and subgroup effects.
How Does TRIUMPH-1 Fit Into the Wider Research Programme?
TRIUMPH-1 is the obesity-only (non-diabetic) arm of the programme. The table below places it in the context of the other published or ongoing TRIUMPH and TRANSCEND programme trials, all reported as factual descriptions of trial design and announced outcomes for research reference only.
| Trial | Population | Duration | Key reported result | Status |
|---|---|---|---|---|
| TRIUMPH-1 | Obesity / overweight, no T2D (n=2,339) | 80 wks (104 ext.) | −28.3% BW (12mg, 80 wks) | Results announced; peer review pending |
| TRIUMPH-4 | Obesity + knee OA (n=445) | 68 wks | −28.7% BW; WOMAC pain −75.8% | Published Dec 2025 |
| TRIUMPH-3 | Obesity + established CVD | Ongoing | Hard CV endpoints (MACE) | Results expected late 2026 |
| TRANSCEND-T2D-1 | Type 2 diabetes (n=537) | 40 wks | −1.94% A1C; −16.8% BW (12mg) | Published in The Lancet, June 2026 |
The breadth of the programme — spanning obesity, type 2 diabetes, osteoarthritis, obstructive sleep apnea, and cardiovascular outcomes — reflects retatrutide's pharmacological profile as a triple GIP/GLP-1/glucagon receptor agonist, in which the glucagon pathway specifically adds energy expenditure signalling and potential hepatic lipid effects not present in dual agonists such as tirzepatide. For background on the receptor mechanism, see our retatrutide clinical research overview.
What Were the Tolerability Findings in TRIUMPH-1?
Eli Lilly's topline announcement and ADA 2026 presentation characterised the tolerability profile of retatrutide in TRIUMPH-1 as broadly consistent with the GLP-1 receptor agonist class. The findings summarised below are from that publicly reported trial data, for research reference only.[2]
Gastrointestinal adverse events — primarily nausea, vomiting, and diarrhoea — were the most commonly reported events across all active dose arms. These events were predominantly mild-to-moderate in severity and occurred most frequently during the dose-escalation period. Serious adverse events and adverse-event-related discontinuations were reported but specific rates are pending full peer-reviewed publication. The tolerability profile described was broadly consistent with the profile observed in the Phase 2 trial (Jastreboff et al., NEJM, 2023), and with published GLP-1 class compounds more broadly. A dedicated cardiovascular safety signal was not identified at Phase 3 dose levels, though TRIUMPH-3 (the cardiovascular outcomes trial) will provide a definitive safety dataset against hard endpoints.
Source: Eli Lilly press release, 21 May 2026 [PR Newswire]; ADA 2026 Scientific Sessions, 6 June 2026 [PR Newswire]
What Are the Next Steps in the TRIUMPH Programme?
As of June 2026, the regulatory and publication pipeline for retatrutide includes several near-term milestones, reported here as factual announcements from Eli Lilly.
For the broader context of how retatrutide compares to tirzepatide and semaglutide across all published trial data, see our comparison guide: Retatrutide vs Tirzepatide vs Semaglutide.
Velox Peptides Supply Information
Retatrutide is supplied as a research reagent only. It is not a medicine, and it has not been approved by the MHRA or FDA. Not for human or veterinary use. See our Research Use Policy and MHRA Statement.
References
- Giblin CR et al. Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: rationale and design of the TRIUMPH registrational clinical trials. Diabetes Obes Metab. 2026. doi:10.1111/dom.70209
- Eli Lilly and Company. Lilly’s triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial. Press release, 21 May 2026. PR Newswire
- Eli Lilly and Company. Lilly’s triple agonist, retatrutide, drove substantial improvements in weight, A1C, knee osteoarthritis pain, and obstructive sleep apnea, demonstrating its remarkable potential to treat obesity and its complications. ADA 2026 press release, 6 June 2026. PR Newswire
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389(6):514–526. PMID: 37366315
- Coskun T, Urva S, Roell WC, et al. LY3437943, a novel triple GIP, GLP-1 and glucagon receptor agonist for glycemic control and weight loss: characterisation of its molecular and cellular kinetics. Cell Metab. 2022;34(6):882–898.e6. PMID: 35108511
- Urva S, Coskun T, Loh MT, et al. LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a Phase 1b study. Lancet. 2022;400(10366):1869–1881. PMID: 36356631
Frequently Asked Questions
What is TRIUMPH-1?
TRIUMPH-1 is a Phase 3, double-blind, placebo-controlled clinical trial evaluating retatrutide (LY3437943) in 2,339 adults with obesity or overweight without type 2 diabetes. It is the pivotal obesity arm of Eli Lilly’s TRIUMPH programme. Topline results were announced 21 May 2026; data were presented at the ADA 2026 Scientific Sessions. All results reported here are for scientific reference only.
What did TRIUMPH-1 report as its primary endpoint at 80 weeks?
TRIUMPH-1 reported average body-weight reductions of 28.3% on retatrutide 12mg, 25.9% on 9mg, and 19.0% on 4mg, compared with 2.2% on placebo. All doses met the primary and key secondary endpoints. A 104-week extension subgroup (BMI ≥35) reported up to 30.3% reduction on 12mg. These are findings from a published clinical trial, not claims about Velox Peptides products.
What secondary endpoints did TRIUMPH-1 report?
At 80 weeks, retatrutide 12mg was reported to reduce triglycerides by 41.0%, non-HDL cholesterol by 24.2%, systolic blood pressure by 12.3 mmHg, and waist circumference by 9.5 in (24.1 cm). A pre-specified OSA subgroup reported a 60.6% reduction in apnea-hypopnea index. High-sensitivity CRP was also significantly reduced. These are secondary endpoint findings from the TRIUMPH-1 trial, reported for scientific reference only.
How does TRIUMPH-1 compare to TRIUMPH-4 and TRANSCEND-T2D-1?
TRIUMPH-1 studied 2,339 adults with obesity without diabetes for 80 weeks (primary weight endpoint). TRIUMPH-4 studied 445 adults with obesity and knee osteoarthritis for 68 weeks, reporting 28.7% weight loss and 75.8% reduction in WOMAC pain. TRANSCEND-T2D-1 studied 537 adults with type 2 diabetes for 40 weeks, reporting A1C reduction of up to 1.94 percentage points and 16.8% weight loss. All are separate trials within the same Phase 3 programme, reported for scientific reference only.
When might retatrutide receive regulatory approval?
Retatrutide is not approved by the MHRA or FDA as of June 2026. Eli Lilly has stated a target to file a New Drug Application (NDA) for Q4 2026. Any approved product would be the licensed pharmaceutical, which is distinct from the research reagent supplied by Velox Peptides for in vitro research use only.
Is retatrutide legal to buy in the UK for research?
Yes. Retatrutide is legal to purchase in the UK for in vitro research purposes. It is not licensed as a medicine and is not approved for human use. Velox Peptides supplies retatrutide as an HPLC-verified (≥99% purity) lyophilised research reagent, dispatched from Northern Ireland, in accordance with our Research Use Policy.
