The published Phase 2 results
The most-cited retatrutide data come from its Phase 2 trial, the weight-loss results of which were published in the New England Journal of Medicine (Jastreboff et al., 2023; DOI 10.1056/NEJMoa2301972). The trial studied multiple dose arms in adults with obesity.
The headline finding was that the highest dose arm reported approximately 24% mean body-weight reduction at 48 weeks — among the largest mean reductions reported for any incretin-class compound to date. Lower dose arms produced smaller, dose-ordered reductions, consistent with a clear dose-response relationship.
Verify before quoting
The ~24% figure is the rounded high-dose Phase 2 result at 48 weeks. The exact value (and the per-dose-arm breakdown) should be read directly from the NEJM paper before being used in any citation — do not treat the rounded number as the precise published figure.
Cross-trial context (not a head-to-head)
It is tempting to line retatrutide's Phase 2 figure up against the approved GLP-1 drugs, but doing so requires care. The numbers below come from different trials, with different durations and populations — they are a cross-trial comparison, not a head-to-head:
| Compound | Reported mean weight loss | Trial |
|---|---|---|
| Retatrutide (high dose) | ≈24% at 48 weeks | Phase 2 (NEJM 2023) |
| Tirzepatide (15 mg) | ≈20.9% at 72 weeks | SURMOUNT-1 (NEJM 2022) |
The retatrutide figure is numerically higher, but it was measured at 48 weeks in a Phase 2 trial, while the tirzepatide figure is a 72-week Phase 3 result. A larger, longer Phase 3 retatrutide read-out is the only fair basis for a direct comparison. For the full mechanism and data breakdown, see Retatrutide vs Tirzepatide.
Phase 3: the TRIUMPH programme
Retatrutide advanced into a Phase 3 clinical programme conducted under the TRIUMPH name. Phase 3 trials test efficacy and safety in larger and more diverse populations and form the evidence base a regulator reviews for marketing approval.
Because Phase 3 reporting evolves and topline results may be released ahead of full publication, this page deliberately does not quote specific TRIUMPH figures. The authoritative sources are the peer-reviewed TRIUMPH publications and Eli Lilly's own announcements — check those for the current Phase 3 outcomes rather than relying on secondary summaries.
How to read these numbers honestly
- Trial averages are not personal outcomes. A mean reduction across a study population does not predict any individual's result.
- Cross-trial numbers are not head-to-head. Different durations, doses and populations make direct 'X beats Y' claims unsupported without a comparative trial.
- Phase 2 is not the final word. Figures can move when larger Phase 3 data are published; treat early figures as provisional.
- These are research findings for a compound not approved for human use — this page summarises evidence, it does not recommend use.
Primary sources
- Jastreboff AM, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine, 2023. DOI 10.1056/NEJMoa2301972.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine, 2022 — referenced for the tirzepatide comparison figure.
- TRIUMPH Phase 3 programme publications and Eli Lilly announcements — consult for current Phase 3 outcomes.
Frequently asked questions
How much weight loss did retatrutide produce in trials?
In the published Phase 2 trial (Jastreboff et al., NEJM 2023), the highest dose arm reported approximately 24% mean body-weight reduction at 48 weeks. This is a single Phase 2 result and the exact figure should be confirmed against the primary publication.
Is retatrutide more effective than tirzepatide for weight loss?
The headline Phase 2 retatrutide figure (~24% at 48 weeks) is numerically higher than tirzepatide's SURMOUNT-1 result (~20.9% at 72 weeks). But these are separate trials with different durations and populations — it is a cross-trial comparison, not a head-to-head, so direct claims of superiority are not supported.
What is the TRIUMPH programme?
TRIUMPH is the name of retatrutide's Phase 3 clinical programme. Phase 3 trials test efficacy and safety in larger populations and are the basis for regulatory approval. TRIUMPH outcomes should be read from the primary publications and Eli Lilly's announcements.
Can I rely on the numbers on this page?
Treat every figure here as a pointer to the primary source, not a substitute for it. Trial figures can be updated or superseded as later analyses and Phase 3 data are published. Always verify against the original NEJM paper and current manufacturer/regulator announcements.
Round out the picture
Efficacy is only half the story — read the tolerability profile and the legal status.