Retatrutide Phase 3: 28.3% mean weight loss at 80 weeks, 11.3% quit the top dose
Lilly's May 21, 2026 topline release for TRIUMPH-1 reports all three doses met primary and key secondary endpoints. The same release reports discontinuation for adverse events rising with dose.
Published October 3, 2026 · Twenty Residues editorial
What the record establishes
- TRIUMPH-1 (NCT05929066) is an 80-week, randomized, double-blind, placebo-controlled Phase 3 trial in adults with obesity or overweight plus at least one weight-related comorbidity, without diabetes.
- Efficacy-estimand mean weight change at 80 weeks: −19.0% (4 mg), −25.9% (9 mg), −28.3% (12 mg), −2.2% (placebo). The treatment-regimen estimand, which counts people who stopped, reads −17.6%, −23.7%, −25.0%, and −3.9%.
- 45.3% of the 12 mg group lost at least 30% of body weight, versus 0.5% on placebo. In a pre-specified extension of 532 participants with BMI ≥35, the 12 mg-to-maximum-tolerated-dose arm reached −30.3% at 104 weeks.
- Most common adverse events at 12 mg vs placebo: nausea 42.4% vs 14.8%, diarrhea 32.0% vs 13.5%, vomiting 25.3% vs 4.8%. Dysesthesia 12.5% vs 0.9%. Discontinuation due to adverse events: 4.1%, 6.9%, 11.3% across doses vs 4.9% on placebo.
- Results are topline, from a company release. Lilly says full results will be presented at medical meetings and published in peer-reviewed journals.
What it does not establish
- Topline means the sponsor's summary. The trial has not been peer-reviewed, and the full adverse-event tables, dropout patterns, and subgroup results are not public.
- Weight loss at 80 weeks says nothing yet about what happens after stopping, cardiovascular outcomes, or safety over years. Those are separate trials (TRIUMPH-2, -3, and an outcomes study).
- Retatrutide is not approved anywhere. Anything sold under that name today is outside this trial and outside this evidence.
What would change this
Peer-reviewed publication of TRIUMPH-1, topline results from TRIUMPH-2 and -3, or a regulatory submission.
The open question
The 12 mg arm produced surgery-level weight loss and more than one in ten participants stopped because of side effects. Is the right dose the one that works best or the one most people can stay on? The 4 mg arm, with a lower dropout rate than placebo, is the quiet half of this release.
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Sources
- [1]
- [2]NCT05929066 — TRIUMPH-1 (ClinicalTrials.gov)
primaryTrial registry
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