Four Phase 3 TRIUMPH trials of retatrutide have reported. TRIUMPH-4, in obesity with knee osteoarthritis, showed 28.7% average weight loss at 68 weeks on 12 mg. TRIUMPH-1, in obesity without diabetes, showed 28.3% at 80 weeks and 30.3% at 104 weeks in the higher-BMI extension. TRIUMPH-2, in type 2 diabetes, showed 20.8% alongside A1C reductions up to 1.6%. TRIUMPH-3, in severe obesity with established cardiovascular disease, showed 22.6%. The consistent pattern is that weight loss is largest in people without diabetes, and that discontinuation from side effects rises steeply with dose. Eli Lilly plans to submit a Biologics License Application to the FDA in Q1 2027.
Four Phase 3 trials of retatrutide have now reported, and the pattern across them is consistent: the largest weight loss in this drug class so far, and discontinuation rates that climb steeply at the top dose. The topline range is 20.8% to 28.7% average weight loss depending on the population, reaching 30.3% in a 104-week extension. Eli Lilly plans to file its Biologics License Application with the FDA in Q1 2027.
Retatrutide is not approved anywhere. Everything below is trial data, and the gap between "worked in a registrational trial" and "available on prescription" is currently at least eighteen months.
What is the TRIUMPH program?
TRIUMPH is Eli Lilly's Phase 3 development programme for retatrutide, a triple agonist of the GLP-1, GIP and glucagon receptors. The trials differ by population rather than by drug, which is what makes reading them together useful: the same doses run against different patients.
| Trial | Population | Participants | Doses | Duration | Reported |
|---|---|---|---|---|---|
| TRIUMPH-4 | obesity/overweight + knee osteoarthritis, no diabetes | 445 | 9, 12 mg | 68 weeks | 11 Dec 2025 |
| TRIUMPH-1 | obesity/overweight + ≥1 comorbidity, no diabetes | 2,339 (+532 extension) | 4, 9, 12 mg | 80 weeks (+24-week extension) | 21 May 2026 |
| TRIUMPH-2 | type 2 diabetes + obesity/overweight | 1,152 | 4, 9, 12 mg | 80 weeks | 23 Jul 2026 |
| TRIUMPH-3 | severe obesity (BMI ≥35) + established cardiovascular disease | 1,949 | 9, 12 mg | 80 weeks | 23 Jul 2026 |
TRIUMPH-4 read out first, in December 2025, and Lilly described it at the time as the first successful Phase 3 trial of the programme with seven further Phase 3 trials expected to complete during 2026.
What did each trial show?
| Trial | Top dose | Average weight loss | Other primary result |
|---|---|---|---|
| TRIUMPH-4 | 12 mg | 28.7% (71.2 lbs) | WOMAC knee pain -74.3% vs -40.3% placebo |
| TRIUMPH-1 | 12 mg | 28.3% (70.3 lbs) at 80 weeks | 30.3% (85.0 lbs) at 104 weeks, BMI ≥35 extension |
| TRIUMPH-2 | 12 mg | 20.8% (49.6 lbs) | A1C reduction up to an average of 1.6% |
| TRIUMPH-3 | 12 mg | 22.6% (55.8 lbs) | primary endpoint met |
TRIUMPH-1 dose response at 80 weeks, on the efficacy estimand: 19.0% at 4 mg, 25.9% at 9 mg, 28.3% at 12 mg, against 2.2% on placebo. On the more conservative treatment-regimen estimand the same arms read 17.6%, 23.7% and 25.0% against 3.9%. Which estimand a source quotes explains most of the apparent disagreement between headlines about this trial.
TRIUMPH-2 dose response: 12.7% (29.8 lbs), 19.1% (45.4 lbs) and 20.8% (49.6 lbs) across 4, 9 and 12 mg.
Why is weight loss lower in the diabetes trial?
This is the most useful comparison the programme offers, because TRIUMPH-1 and TRIUMPH-2 ran the same doses for the same 80 weeks and differ mainly by whether participants had type 2 diabetes.
Weight loss at 12 mg: 28.3% without diabetes, 20.8% with. A gap of roughly seven and a half percentage points.
That direction is not new. Semaglutide and tirzepatide both produce less weight loss in people with type 2 diabetes than in people without, and the usual explanations involve differences in baseline metabolic state and concurrent glucose-lowering therapy. Retatrutide behaving the same way is a consistency finding rather than a surprise, and it means quoting a single headline percentage for this drug without naming the population is misleading.
What about the side effects?
Gastrointestinal, dose-dependent, and the reason the top dose is not automatically the right dose.
TRIUMPH-1 adverse event rates across the dose arms: nausea 28.6% to 42.4%, diarrhea 25.2% to 34.1%, constipation 23.8% to 26.1%, vomiting 10.6% to 25.3%.
The number that carries more information than any of those is discontinuation:
| Trial | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| TRIUMPH-1 | 4.1% | 6.9% | 11.3% | 4.9% |
| TRIUMPH-3 | n/a | 9.8% | 13.5% | 4.8% |
At 12 mg, roughly one participant in eight left the trial because of side effects, against one in twenty on placebo. In TRIUMPH-3, in a sicker population, it was closer to one in seven. Tolerability, not efficacy, is what separates the 9 mg and 12 mg arms in practice, and the 4 mg arm in TRIUMPH-1 still delivered 19.0% weight loss with a discontinuation rate below placebo-adjacent levels.
Our retatrutide side effects page covers the reported profile in more detail, and the published dose ladder is in retatrutide dosing protocols.
When could retatrutide actually be approved?
Lilly stated in its July 2026 announcement that it plans to submit a Biologics License Application to the FDA in Q1 2027, following completion of chemistry, manufacturing and controls data requirements.
Working forward from that: a Q1 2027 filing under standard review puts an FDA decision in late 2027 or 2028. Priority review would compress that but is not indicated. Any published timeline claiming a 2026 approval, or a 2026 submission, is out of date.
Until then there is no legal prescription channel. Retatrutide is not in FDA-confirmed shortage and is not eligible for compounding under 503A, which we explain in the 503A and PCAC piece. The only medically supervised access route is trial enrolment. Everything sold online is research-grade material of unverified provenance, which is the subject of where to buy retatrutide.
What the programme has not answered
No head-to-head trial against tirzepatide or semaglutide. Every comparison being made, including ours in retatrutide vs tirzepatide, is cross-trial and therefore unreliable. Different populations, different baselines, different durations.
No cardiovascular outcomes result. TRIUMPH-3 enrolled participants with established cardiovascular disease and met its weight endpoint, but that is not the same as a MACE outcomes trial demonstrating cardiovascular benefit.
Body composition is not in the topline releases. How much of the loss is fat versus lean mass is the open question for a drug producing 28% total weight reduction. Our muscle loss on GLP-1s piece covers what is known for the class.
Nothing beyond 104 weeks. The longest data is the TRIUMPH-1 extension. What happens on discontinuation, and whether the loss holds, is unstudied.
Correction, 6 August 2026
The earlier version of this article was wrong in ways worth stating plainly.
It reported TRIUMPH-4 as showing 24% weight loss at 48 weeks in an obesity-plus-comorbidities population enriched for cardiovascular risk. TRIUMPH-4 ran 68 weeks, in obesity with knee osteoarthritis, and showed 28.7% at 12 mg. The article had TRIUMPH-3 and TRIUMPH-4 populations transposed: TRIUMPH-3 is the severe-obesity-plus-cardiovascular-disease trial.
It also listed all of TRIUMPH-1 through TRIUMPH-4 as published as of May 2026. TRIUMPH-2 and TRIUMPH-3 did not report until 23 July 2026. And it described a "2026 FDA submission target," which Lilly has since specified as a Q1 2027 BLA.
The programme roster in the earlier version, showing five trials with a TRIUMPH-5 cardiovascular outcomes study, could not be verified against Lilly's own announcements and has been removed rather than rewritten. Logged in our corrections record.
Sources
- Lilly - retatrutide successful in two additional Phase 3 obesity trials (TRIUMPH-2, TRIUMPH-3) - 23 July 2026, includes the Q1 2027 BLA statement
- Lilly - retatrutide delivered powerful weight loss in pivotal Phase 3 obesity trial (TRIUMPH-1) - 21 May 2026
- Lilly - retatrutide weight loss up to 71.2 lbs with osteoarthritis pain relief (TRIUMPH-4) - 11 December 2025
- Triple-Hormone-Receptor Agonist Retatrutide for Obesity - NEJM Phase 2
- Internal: retatrutide dosing protocols, retatrutide side effects, retatrutide vs tirzepatide, where to buy retatrutide
Frequently asked
What were the TRIUMPH-4 retatrutide results?
TRIUMPH-4 enrolled 445 adults with obesity or overweight and knee osteoarthritis, without diabetes, and ran 68 weeks. Average weight loss was 26.4% (64.2 lbs) on 9 mg and 28.7% (71.2 lbs) on 12 mg, against 2.1% on placebo. WOMAC knee pain scores fell 74.3% on 12 mg versus 40.3% on placebo. Results were announced on 11 December 2025.
How much weight did people lose on retatrutide in Phase 3?
It depends on the population. In obesity without diabetes (TRIUMPH-1), 28.3% at 80 weeks on 12 mg, rising to 30.3% at 104 weeks in the higher-BMI extension. In obesity with knee osteoarthritis (TRIUMPH-4), 28.7% at 68 weeks. In type 2 diabetes (TRIUMPH-2), 20.8%. In severe obesity with cardiovascular disease (TRIUMPH-3), 22.6%.
When will retatrutide be FDA approved?
No approval date exists. Eli Lilly stated in July 2026 that it plans to submit a Biologics License Application to the FDA in Q1 2027, following completion of chemistry, manufacturing and controls requirements. A standard review after a Q1 2027 filing would place a decision in late 2027 or 2028. Retatrutide is not approved anywhere today.
Does retatrutide work as well in people with type 2 diabetes?
Less well for weight, which matches the pattern seen with other incretin drugs. TRIUMPH-2 participants with type 2 diabetes lost up to 20.8% at 80 weeks, against 28.3% for participants without diabetes in TRIUMPH-1 over the same duration and dose range. TRIUMPH-2 also showed A1C reductions of up to an average of 1.6%.
What are the side effects of retatrutide in the Phase 3 trials?
Gastrointestinal effects dominate. TRIUMPH-1 reported nausea in 28.6% to 42.4% of participants, diarrhea in 25.2% to 34.1%, constipation in 23.8% to 26.1%, and vomiting in 10.6% to 25.3%. Discontinuation due to adverse events rose with dose, from 4.1% at 4 mg to 11.3% at 12 mg, against 4.9% on placebo.
Is retatrutide better than tirzepatide?
On weight loss in trials, the retatrutide numbers are larger, but no head-to-head trial has been run, so cross-trial comparison is the only tool available and it is unreliable. Retatrutide adds glucagon-receptor agonism to tirzepatide's GLP-1 and GIP mechanism, which is the proposed source of both the larger effect and the higher discontinuation rates.