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Retatrutide Phase 3 Results: What the TRIUMPH Trials Found
When the phase 2 retatrutide data came out in 2023, the number everyone quoted was 24.2% weight reduction at 48 weeks. That trial had a few hundred participants. Since then the compound has moved into a full phase 3 program, and the dataset behind it is now much larger.
This covers what those trials reported. If you want the mechanism first, the retatrutide explainer walks through how one molecule ends up activating three receptors, and the GLP-1 background piece covers the class it came from.
What TRIUMPH actually is
TRIUMPH is the name of the phase 3 program Eli Lilly built around retatrutide. It is not one trial. It is a set of them, each pointed at a different population, which is the normal way a compound of this size gets studied.
Splitting it up matters for reading the results. A trial in adults with obesity and knee osteoarthritis is asking a different question than one in adults with obesity alone, so the numbers are not directly interchangeable. Two of the readouts have been reported publicly so far.
Where phase 2 left off
The 2023 phase 2 trial ran 48 weeks and tested four dose levels. Mean weight reduction came in at 8.7% for 1 mg, 17.1% for 4 mg, 22.8% for 8 mg and 24.2% for 12 mg. Placebo was 2.1%.
The detail that mattered most was not the headline figure. It was that the weight curve had not flattened when the trial ended. Participants were still losing at week 48, which meant 24.2% was wherever the study stopped, not where the compound stopped.
TRIUMPH-4, the first phase 3 readout
Reported in December 2025, this one enrolled adults with obesity who also had knee osteoarthritis. Average starting weight was 112.7 kg with a BMI of 40.4, so this was a heavier group than most obesity trials recruit.
At 68 weeks, the 12 mg dose produced a mean reduction of 28.7%, which worked out to 32.3 kg. The 9 mg dose gave 26.4%. Placebo was 2.1%. Close to half the participants on retatrutide lost at least a quarter of their body weight.
Knee pain scores improved alongside the weight, which is the result the trial was designed to look for.
TRIUMPH-1, the pivotal trial
This is the big one. Reported in May 2026, it randomized 2,339 adults with obesity or overweight into four equal groups: 4 mg, 9 mg, 12 mg or placebo, run double blind over 80 weeks.
Mean weight reduction was 19.0% at 4 mg, 25.9% at 9 mg and 28.3% at 12 mg. In the 12 mg group, 45.3% of participants lost at least 30% of their starting body weight.
That last figure is the one that changed how people talk about this compound. Losing 30% or more had generally been the territory of bariatric surgery, not injectables.
| Trial | Length | Dose | Mean weight reduction |
|---|---|---|---|
| Phase 2 | 48 weeks | 12 mg | 24.2% |
| TRIUMPH-4 | 68 weeks | 12 mg | 28.7% |
| TRIUMPH-1 | 80 weeks | 12 mg | 28.3% |
| TRIUMPH-1 | 80 weeks | 9 mg | 25.9% |
| TRIUMPH-1 | 80 weeks | 4 mg | 19.0% |
The dose response is clean and it holds across trials. Every step up in dose produced more weight loss, and the longer trials landed higher than the shorter one at the same dose.
What happened past 80 weeks
TRIUMPH-1 included an extension, and this is the part that answered the open question from phase 2.
Participants who started with a BMI of 35 or above and stayed in the extension kept losing weight, reaching a mean of 30.3% at 104 weeks. So the curve from phase 2 was not an artifact of a short trial. Given two years, the number kept climbing.
The measurements that were not weight
Weight is the headline, but the trials tracked a lot of other markers, and several moved.
In TRIUMPH-4, systolic blood pressure dropped by 14.0 mmHg on the 12 mg dose. Triglycerides, non-HDL cholesterol and high sensitivity C-reactive protein all improved. Lilly has also reported effects on A1C and on obstructive sleep apnea across the wider program.
Some of that follows from the weight loss itself. Some of it points back at the glucagon receptor arm, which acts on liver fat and energy expenditure rather than appetite. Retatrutide is the only compound in this class carrying that third receptor, and it is why tirzepatide and retatrutide behave differently despite sharing two of three targets.
What the trials recorded on tolerability
Gastrointestinal effects were the most commonly reported across the program, mainly nausea, diarrhea and vomiting, and they clustered around the points where doses were stepped up rather than spreading evenly through the trial. Heart rate increases were also recorded, which tracks with glucagon receptor activation raising metabolic rate.
Both patterns showed up in phase 2 and carried into phase 3 at the larger sample sizes.
Where the program stands
Retatrutide is an investigational compound. The TRIUMPH program is still running, with further readouts pending across the different populations it covers.
What has changed since 2023 is the weight of evidence behind it. A few hundred participants over 48 weeks became thousands over 80 and 104 weeks, and the effect held up as the trials got bigger and longer. That is the part worth paying attention to, because scale is usually where promising phase 2 results start to shrink.
Formats and handling
Retatrutide ships freeze dried and has to be reconstituted before use. Bring the vial to room temperature, run the diluent down the inside wall instead of straight into the powder, and leave it to dissolve without shaking. The reconstitution guide has the full sequence, storage becomes the limiting factor once it is in solution, and the concentration math is worth working out before you mix rather than after.
Stocked here in 5 mg, 10 mg, 20 mg, 30 mg, 40 mg and 60 mg vials.
Common questions
How much weight did retatrutide produce in phase 3?
At the 12 mg weekly dose, 28.3% mean reduction over 80 weeks in TRIUMPH-1 and 28.7% over 68 weeks in TRIUMPH-4. Participants with a BMI of 35 or above who continued into the TRIUMPH-1 extension reached 30.3% at 104 weeks.
Why is TRIUMPH-1 called the pivotal trial?
It is the largest of the readouts so far at 2,339 participants, it ran the longest at 80 weeks before the extension, and it tested the compound in the broad obesity population rather than a subgroup with a specific additional condition.
Did the higher dose always win?
Yes across every readout. 4 mg, 9 mg and 12 mg lined up in order in TRIUMPH-1, and the same ordering appeared in phase 2 and in TRIUMPH-4. A clean dose response like that is one of the things trial designers look for.
How does this compare to tirzepatide?
Retatrutide reported higher mean reductions, though the trials were separate and ran on different populations and timelines, so the figures are not a head to head result. The mechanistic difference is the glucagon receptor, which adds energy expenditure and liver fat metabolism to what the two incretin receptors already do.
TL;DR
Retatrutide moved from a 48 week phase 2 trial to a phase 3 program running 80 weeks and beyond. TRIUMPH-4 reported 28.7% mean weight reduction at 12 mg over 68 weeks. TRIUMPH-1, with 2,339 participants, reported 28.3% over 80 weeks, with 45.3% of that group losing 30% or more, and 30.3% at 104 weeks in the extension. Blood pressure, triglycerides and inflammatory markers moved alongside the weight. The compound remains investigational and the program is still running.
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