Retatrutide Clinical Trials
A detailed look at the TRIUMPH trial programme - what the Phase 2 results showed and what Phase 3 trials are currently investigating.
~24%
Max Phase 2 weight loss
~340
Phase 2 participants
48 weeks
Phase 2 duration
Understanding Trial Data
Phase 2 trials are designed to test different doses and gather preliminary efficacy data. They use relatively small numbers of participants. Phase 3 trials are larger, longer, and required for regulatory approval. Results from Phase 2 may not be replicated in Phase 3.
Phase 2 Trial Results (TRIUMPH-2)
Published in the New England Journal of Medicine in June 2023. This was a 48-week, randomised, double-blind, placebo-controlled trial.
Participants
~340 adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related condition
Duration
48 weeks of treatment with dose escalation over first 20-36 weeks
Doses Tested
1mg, 4mg, 8mg, 12mg weekly injections vs placebo
Primary Endpoint
Percentage change in body weight from baseline
Weight Loss by Dose
| Dose | Weight Loss | ~Participants | Notes |
|---|---|---|---|
| 1 mg weekly | ~8% | ~70 | Lowest tested dose |
| 4 mg weekly | ~17% | ~70 | Middle dose range |
| 8 mg weekly | ~22% | ~70 | High efficacy dose |
| 12 mg weekly | ~24% | ~70 | Highest tested dose |
| Placebo | ~2% | ~70 | Control group |
Key findings: Weight loss was dose-dependent and continued throughout the 48-week period. Approximately 100% of participants on 8mg and 12mg doses achieved ≥5% weight loss. The majority of weight loss occurred during the first 24 weeks.
Read full study in NEJMCurrent Phase 3 Trials
The TRIUMPH Phase 3 programme includes multiple trials. These larger studies will determine whether retatrutide can be approved for use.
Participants
~1,800
Duration
52 weeks
Focus
Evaluating glycemic control and safety in adults with type 2 diabetes
Participants
~1,600
Duration
72 weeks
Focus
Evaluating weight loss efficacy and safety in adults with obesity
Participants
~1,800
Duration
52 weeks
Focus
Long-term weight maintenance and cardiovascular outcomes
Interested in Joining a Trial?
Some trials may have UK sites. Search for eligibility at ClinicalTrials.gov or speak with your GP about trial opportunities.
How Do These Results Compare?
Retatrutide vs Tirzepatide (Mounjaro)
In separate Phase 2 trials, retatrutide (~24% at highest dose) appeared to show greater weight loss than tirzepatide (~21% at highest dose). However, cross-trial comparisons are unreliable.
Retatrutide vs Semaglutide (Wegovy)
Semaglutide trials showed ~15-17% weight loss over similar timeframes. Retatrutide's Phase 2 results suggest potentially greater efficacy, but Phase 3 confirmation is needed.
Important Caveats
Cross-trial comparisons are problematic because trials have different patient populations, inclusion criteria, study designs, and endpoints. The only reliable comparison would be a head-to-head trial, which hasn't been conducted.
Trial Programme Timeline
Phase 1 Trials
Completed 2022Initial safety and dosing studies in healthy volunteers
Phase 2 Trials (TRIUMPH-2)
Completed 2023Dose-finding study showing up to 24% weight loss over 48 weeks
Phase 3 Trials (TRIUMPH 1, 3, 4)
Ongoing 2024-2026Large-scale trials for obesity and type 2 diabetes indications
Regulatory Submission
Expected 2026+FDA and MHRA submissions expected if Phase 3 trials succeed
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Medical Disclaimer
This information is for educational purposes only and does not constitute medical advice. Clinical trial data is preliminary and subject to change. Retatrutide is an investigational drug not approved by any regulatory authority. Individual results in trials varied significantly from averages presented. For advice about weight management treatments, consult a qualified healthcare provider.
Primary source: Jastreboff et al., NEJM 2023
Last updated: December 2025