Retatrutide Phase 3 (TRIUMPH) Program: What Has Been Reported as of September 2026

What is the TRIUMPH program?

TRIUMPH is Eli Lilly's phase 3 clinical program for retatrutide (LY3437943), the GIP, GLP-1, and glucagon receptor triple agonist, in adults with obesity or overweight. As of September 2026, four TRIUMPH trials have reported topline results: TRIUMPH-4 in December 2025, TRIUMPH-1 in May 2026, and TRIUMPH-2 and TRIUMPH-3 together on July 23, 2026. A parallel program, TRANSCEND, covers type 2 diabetes as the primary indication. This article summarizes what the company and the trade press have reported from the four readouts and is dated to the first week of September 2026. Every figure below is a topline number from a press release or conference presentation, not a peer-reviewed publication, unless stated otherwise. The earlier phase 2 trial breakdown and the trial landscape overview cover the program's design and the studies still running.

What did TRIUMPH-4 report?

TRIUMPH-4 was the first phase 3 retatrutide trial to read out, in December 2025, in adults with obesity and knee osteoarthritis. At 68 weeks, participants in the highest dose arm showed a mean body weight reduction of 28.7% per the company's topline release. The trial's osteoarthritis endpoints were the distinguishing feature: WOMAC pain scores fell by up to a mean of 4.5 points, reported as a 75.8% reduction, and more than one in eight retatrutide-treated participants reported being free of knee pain at the end of the study. Physical function measures improved alongside. The combination of a body weight endpoint and a joint pain endpoint made TRIUMPH-4 the first phase 3 evidence that the compound's effects extended to a weight-related comorbidity, and it was the source of the widely quoted figure of roughly 71 pounds mean weight reduction.

What did TRIUMPH-1 report?

TRIUMPH-1, the pivotal obesity trial, reported topline results in May 2026. It enrolled 2,339 adults with obesity or overweight without type 2 diabetes and randomized them across three retatrutide dose arms and placebo, with 80 weeks of treatment. Mean body weight reductions at 80 weeks were 17.6%, 23.7%, and 25.0% across the low, middle, and high dose arms respectively, against 3.9% on placebo. Some outlets reported a higher headline figure for the top arm under an alternate statistical estimand that excludes the effect of treatment discontinuation; the treatment-regimen figures above are the conservative ones. TRIUMPH-1 is the trial that will anchor the regulatory submission, and its 80-week duration is longer than the 48-week phase 2 study, which matters for the comparison below.

What did TRIUMPH-2 and TRIUMPH-3 report?

TRIUMPH-2 and TRIUMPH-3 reported together on July 23, 2026. TRIUMPH-2 enrolled adults with obesity or overweight and type 2 diabetes. Across the three dose arms at 80 weeks, mean body weight reductions were 12.7%, 19.1%, and 20.8%, and hemoglobin A1C fell by up to a mean of 1.6 percentage points. The smaller weight effect relative to TRIUMPH-1 is consistent with the pattern seen across the incretin class, where participants with type 2 diabetes show attenuated weight response.

TRIUMPH-3 enrolled adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes, and tested two dose arms. Mean body weight reduction reached up to 22.6% at 80 weeks. The trial also tracked major adverse cardiovascular events (MACE), and the company stated that MACE occurred less frequently than anticipated in both the retatrutide and placebo arms, which limits what can be concluded about cardiovascular outcomes from this study alone. A dedicated cardiovascular outcomes trial remains the standard for that question.

How do the phase 3 results compare with the phase 2 report?

The phase 2 study published in 2023 reported a mean body weight reduction of 24.2% at 48 weeks in the highest dose arm, with the curves not yet plateaued. TRIUMPH-1 at 80 weeks reported 25.0% in the corresponding arm. The near-identical figure across a longer duration and a much larger population is the headline comparison: the phase 3 program confirmed the magnitude of the phase 2 effect rather than exceeding it. Two caveats apply. The phase 2 top arm was smaller and the study shorter, so the 48-week figure reflected a curve still descending, and the 80-week phase 3 figure reflects a curve closer to plateau. And the phase 3 program's dose arms were not identical to phase 2's. The comparison against tirzepatide and semaglutide discusses where these figures sit relative to the approved dual and single agonists.

What safety and tolerability findings were reported?

The company's releases described the safety profile across the four trials as consistent with the incretin class, with gastrointestinal adverse events (nausea, diarrhea, vomiting, constipation) the most common and predominantly mild to moderate, occurring mainly during dose escalation. Discontinuation rates due to adverse events were reported by arm in each release; readers should consult the individual press releases for the per-arm figures, since they vary by trial and population. Two signals that were discussed after the phase 2 publication, a modest increase in heart rate during early treatment and a reported effect on dysesthesia and skin sensitivity, were tracked in phase 3 but the topline releases did not add detail beyond describing the overall profile as consistent with prior studies. Full safety data will appear with the peer-reviewed publications.

What is still pending?

As of September 2026, several items remain. The peer-reviewed publications of TRIUMPH-1 through TRIUMPH-4 have not all appeared; TRIUMPH-4 and TRIUMPH-1 data were presented at scientific meetings during 2026 and manuscripts are expected to follow. The TRANSCEND type 2 diabetes program has additional readouts pending. Cardiovascular and renal outcomes trials are ongoing with completion dates beyond 2026. And the regulatory submission has not been made: Lilly has stated it plans to submit a Biologics License Application to the FDA in the first quarter of 2027. Approval, if granted, would follow standard review timelines from that point. Nothing about the compound's regulatory status has changed as of this article's date; retatrutide remains an investigational drug.

How should the topline figures be read?

Topline releases report the primary endpoint and selected secondaries with the statistical framing the sponsor chooses. The efficacy estimand (participants who stayed on treatment) and the treatment-regimen estimand (all randomized participants regardless of adherence) can differ by several percentage points, and press coverage does not always specify which is quoted. The figures in this article are treatment-regimen figures where the source made the distinction clear. Comparisons across trials with different populations, durations, and dose arms are approximate. The peer-reviewed publications will be the definitive source, and this article will be updated as they appear.

Retatrutide is an investigational compound. This article reports published and company-released clinical trial data for educational purposes and does not describe or endorse any use of the compound. It is not medical advice.