Retatrutide TRIUMPH-1: 28% Weight Loss at 80 Weeks
TRIUMPH-1 Phase 3: retatrutide 12 mg delivered an average 28.3% weight loss at 80 weeks, setting a new benchmark for drug-based obesity treatment.
May 29, 2026 · 3 min read
Eli Lilly reported topline results from TRIUMPH-1, the pivotal Phase 3 trial of retatrutide in adults with obesity or overweight without diabetes, showing weight loss that exceeds any drug-based obesity therapy previously reported in a Phase 3 trial. At 80 weeks, the 12 mg dose produced a mean weight loss of 28.3% of baseline body weight — or approximately 70.3 pounds. All three doses tested (4 mg, 9 mg, and 12 mg) met both the primary and key secondary endpoints.
The numbers
| Dose | Mean weight loss (%) | Mean weight loss (lbs) |
|---|---|---|
| 12 mg | 28.3% at 80 weeks | ~70.3 lbs |
| 9 mg | 25.9% at 80 weeks | ~64.4 lbs |
| 4 mg | ~19% at 80 weeks | ~47.2 lbs |
| Placebo | ~2.2% at 80 weeks | — |
At 104 weeks, the 12 mg group reached an average weight loss of up to 30.3%, with 45.3% of participants achieving ≥30% total body weight reduction. Lilly described the tolerability of the lower 4 mg dose as exceeding the company's expectations, a detail that matters for patients who can't tolerate the maximum dose.
Why it matters
The SURMOUNT-1 trial for tirzepatide — the current most-effective approved GLP-1 drug — showed roughly 22.5% weight loss over 72 weeks at the highest dose. TRIUMPH-1's 12 mg arm exceeds that at 80 weeks, and reaches bariatric-surgery-level outcomes for a meaningful share of participants (the ≥30% responders).
Retatrutide's triple mechanism — GLP-1, GIP, and glucagon receptor agonism — has been theorized to produce greater weight loss than dual agonists because the glucagon component increases resting energy expenditure in addition to reducing appetite. The TRIUMPH-1 data supports that hypothesis at the Phase 3 level.
Lilly has indicated it expects to file an NDA with the FDA, with analysts watching for a submission in the second half of 2026. Seven additional TRIUMPH Phase 3 readouts are expected in 2026, including TRIUMPH-2 (type 2 diabetes) and TRIUMPH-3 (established cardiovascular disease).
Retatrutide's AE profile tracked the class: predominantly GI adverse events (nausea, vomiting, diarrhea), dose-dependent, and largely resolving with continued use. The safety profile is being monitored closely by analysts given the glucagon component's novel contribution, and long-term cardiovascular outcomes data is still pending from TRIUMPH-3.
What to watch
The ADA 86th Scientific Sessions (June 5–8, New Orleans) will include a Phase 3 retatrutide symposium where additional data from TRIUMPH-1 and other readouts will be presented. Full data publications in peer-reviewed journals, required before FDA submission, are expected later this year. For patients and clinicians following the pipeline, the NDA submission date and FDA review timeline will be the key milestones to track.
For background on where retatrutide fits relative to tirzepatide and semaglutide, see our retatrutide vs tirzepatide comparison and the retatrutide FDA approval timeline.
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