Phase 3 TRIUMPH · Eli Lilly

Retatrutide Phase 3: 28.3% Body Weight Loss at 80 Weeks

📄 1 PubMed citation

Eli Lilly's TRIUMPH Phase 3 trial of retatrutide (LY3437943) reported the largest weight-loss effect ever observed in a late-stage obesity pharmaceutical study. Average 70 lbs lost. 45% of participants lost 30%+ of body weight. 65% on the top dose were no longer clinically obese. Here is what the full readout actually showed.

📊 Numbers reflect the Eli Lilly Phase 3 TRIUMPH-1 obesity readout (mean BW loss at the 12mg dose, 80 weeks). Phase 3 obesity-osteoarthritis cohort (TRIUMPH-4) data covered separately on retatrutide-results.
0
Mean body weight loss
(12mg, 80 weeks)
0
Lost ≥30% of body weight
(top dose)
0
No longer clinically obese
(BMI < 30)
📋 On this page
  1. What TRIUMPH Actually Showed
  2. Weight Loss by Dose
  3. Response Rate Thresholds
  4. vs Tirzepatide vs Semaglutide
  5. Safety & Dropouts
  6. FDA Approval Timeline
  7. Study Details
  8. Key Takeaways
  9. FAQ
  10. 🛒 Recommended Products
  11. 📚 Related HighPeptides Research
Why This Matters

What TRIUMPH Actually Showed

Phase 2 retatrutide already produced the largest weight-loss numbers ever recorded in an anti-obesity drug trial — 24.2% body weight loss at 48 weeks. Phase 3 TRIUMPH ran longer (80 weeks), in a larger and more diverse population, and the numbers got bigger.

⚖️
28.3% Mean Body Weight Loss

At the 12mg dose over 80 weeks, the mean body weight reduction was 28.3% — exceeding the Phase 2 result (24.2% at 48 weeks) and setting a new ceiling for any obesity drug at any phase of clinical development. Mean absolute weight loss was approximately 70 lbs.

🎯
45% Lost ≥30% of Body Weight

Nearly half of participants on the top dose lost 30% or more of their starting body weight — a category-shifting result. For comparison, the same threshold (≥30%) was achieved by roughly 25% of tirzepatide responders at 15mg and approximately 7% of semaglutide responders at 2.4mg.

📉
65% No Longer Clinically Obese

Two-thirds of participants on the 12mg dose reduced their BMI below 30 at trial end — they no longer met the medical definition of obesity. This is the strongest BMI-category-shift signal ever reported in an anti-obesity pharmaceutical trial.

🧬
Triple Agonist Mechanism

Retatrutide activates GLP-1, GIP, and glucagon receptors. Semaglutide hits GLP-1 only. Tirzepatide hits GLP-1 and GIP. The glucagon component appears to drive higher resting energy expenditure and direct hepatic fat oxidation — the mechanism behind the incremental weight-loss advantage.

Phase 3 Primary Data

Weight Loss by Dose

Mean percentage body weight change from baseline at week 80, by assigned dose group. The dose-response relationship is preserved at Phase 3 scale, with the 12mg dose producing the largest effect.

4 mg
Low dose
−19%
Mean body weight change, 80 weeks
Dropout rate below placebo — strong tolerability-to-efficacy ratio. Still produces weight loss greater than the maximum dose of semaglutide.
8 mg
Mid dose
~24%
Mean body weight change, 80 weeks
Interpolated estimate from the dose-response curve. Sits between the 4mg and 12mg groups; tolerability is closer to tirzepatide than to the 12mg arm.
12 mg
Top dose
−28.3%
Mean body weight change, 80 weeks
Highest weight-loss number ever reported in a Phase 3 obesity trial. 11.3% treatment discontinuation due to adverse events. Average absolute loss: ~70 lbs.

All values are mean change from baseline body weight in the intent-to-treat population. Completer analyses ran slightly higher (28.3% mean ≈ 30%+ in completers at 12mg).

Response Rate Thresholds

How Many People Hit Major Loss Thresholds

Mean weight loss tells you the average — these numbers tell you how many participants actually hit clinically meaningful thresholds on the 12mg dose.

≥5%
Nearly all participants
≥95% of participants on 12mg lost at least 5% of body weight — the FDA's minimum threshold for clinically meaningful weight loss. This is the trivial threshold; most participants exceeded it within the first 20 weeks.
≥15%
≈85% of participants
Roughly 85% of participants on the 12mg dose exceeded 15% body weight loss — the threshold semaglutide barely achieves on average. At this dose, what semaglutide considers exceptional, retatrutide considers typical.
≥25%
≈60% of participants
Approximately 60% of participants on the top dose lost a quarter or more of their starting body weight. To put this in scale: a 250lb participant losing 25% is now 187lb.
≥30%
45% of participants
45% lost 30% or more of body weight — this is the bariatric-surgery comparison zone. Roux-en-Y gastric bypass averages around 30% total body weight loss at 1 year. Retatrutide reaches this threshold pharmacologically in nearly half of users.
Head-to-Head Comparison

vs Tirzepatide vs Semaglutide

A cross-trial comparison of the three landmark anti-obesity Phase 3 readouts. Different durations, different populations — but the receptor coverage and weight-loss ceiling map cleanly.

Semaglutide
(STEP-1)
Tirzepatide
(SURMOUNT-1)
Retatrutide
(TRIUMPH)
Receptor agonismMechanism of action
GLP-1
GLP-1 + GIP
GLP-1 + GIP + Glucagon
Top doseMax studied weekly dose
2.4 mg
15 mg
12 mg
Trial durationPrimary endpoint window
68 wks
72 wks
80 wks
Mean body weight lossTop dose, ITT
~15%
~22%
28.3%
≥30% body weight lossApproximate response rate
~7%
~25%
45%
Treatment discontinuationDue to adverse events, top dose
~7%
~6%
11.3%
Regulatory statusAs of May 2026
FDA approved
FDA approved
NDA expected
Cross-trial comparison caveat: STEP-1, SURMOUNT-1, and TRIUMPH used different patient populations, baseline BMIs, titration protocols, and durations. Head-to-head trials between these compounds have not been published. The numbers are directionally accurate but should not be read as a perfect apples-to-apples comparison.
Tolerability

Safety and Dropout Profile

The efficacy ceiling came with a tolerability tradeoff — GI adverse events ran higher than tirzepatide at the equivalent dose. Dropout rates, by contrast, are dose-dependent in a useful way.

Treatment discontinuation: 12mg dose
Dropped out due to adverse events — higher than tirzepatide (~6% in SURMOUNT-1)
11.3%
Treatment discontinuation: 4mg dose
Dropout rate lower than placebo — best tolerability-to-efficacy ratio of any GLP-1 trial
< placebo
Nausea (any grade, 12mg)
Most common GI adverse event — typically peaks during dose escalation
~65%
Vomiting (any grade, 12mg)
Higher rate than tirzepatide at 15mg in cross-trial comparison
~30%
Diarrhea (any grade, 12mg)
Most events were mild-to-moderate; resolved with slower titration in observational data
~28%
📊 The 4mg dose is the underrated story

19% body weight loss with a dropout rate below placebo is a result no other GLP-1-class drug has matched at any dose. For people who can't tolerate the GI side effects of the 12mg arm, the 4mg dose still delivers a result that exceeds the maximum dose of semaglutide and approximates tirzepatide at 10mg. The dose-response curve here is unusually friendly.

Regulatory

FDA Approval Timeline

With the TRIUMPH Phase 3 readout in hand, Eli Lilly is positioned to file a New Drug Application (NDA) with the FDA. Based on the typical anti-obesity drug review path — standard 10-month review, occasionally accelerated by FDA priority review for severe-obesity populations — industry analysts expect:

  • 📝 2026: NDA submission to FDA, EMA filings in Europe
  • ⏳ Late 2026 – 2027: Potential FDA approval window for obesity indication
  • 💊 2027–2028: Likely launch as a follow-on to Zepbound (tirzepatide), with diabetes and cardiovascular outcomes trials running in parallel
  • ⚠️ Caveat: Manufacturing capacity for GLP-1-class drugs has been a bottleneck. Even after approval, market availability and pricing may be constrained for the first 12–18 months.

Currently retatrutide is not FDA approved for any indication. Any compound sold under the name "retatrutide" outside of an Eli Lilly clinical trial is a research-grade compound, not a prescription drug.

Citation

Study Details

Phase 3 TRIUMPH Program — Retatrutide for Obesity

Eli Lilly's Phase 3 TRIUMPH program evaluated retatrutide (LY3437943), a once-weekly GLP-1 / GIP / glucagon triple receptor agonist, in adults with obesity or overweight with related conditions. The primary endpoint was percent change in body weight at week 80.

Sponsor
Eli Lilly and Company
Compound
Retatrutide (LY3437943)
Mechanism
Triple agonist: GLP-1 + GIP + glucagon receptor
Phase
Phase 3, randomized, double-blind, placebo-controlled
Duration
80 weeks
Doses
4 mg, 8 mg, 12 mg, placebo (once-weekly subcutaneous)
Primary endpoint
Percent change in body weight from baseline at week 80
Headline result
28.3% mean body weight loss at 12 mg
Readout
Eli Lilly investor disclosure, 2026
NCT identifier
NCT05298618 (TRIUMPH-1, obesity)
Bottom Line

Key Takeaways

What the Phase 3 TRIUMPH readout confirmed — and what still needs to be established before retatrutide reaches the market.

✅ What We Know
  • Retatrutide at 12mg produces mean 28.3% body weight loss over 80 weeks — the largest effect ever seen in a Phase 3 obesity trial.
  • 45% of participants on the top dose lost 30%+ of their body weight, approaching the result range typically associated with bariatric surgery.
  • 65% of participants on 12mg reduced their BMI below 30 — they no longer met the clinical definition of obesity at trial end.
  • The 4mg dose produced 19% mean weight loss with a dropout rate lower than placebo — the most favorable tolerability-to-efficacy ratio of any GLP-1 class trial.
  • Dose-response is preserved at Phase 3 scale: 4mg → 19%, 12mg → 28.3%, with the 8mg arm interpolating between them.
  • The triple-agonist mechanism (GLP-1 + GIP + glucagon) drives the incremental weight-loss advantage over tirzepatide and semaglutide.
⚠️ What We Don't Know
  • Long-term safety beyond 80 weeks has not yet been established in published data.
  • Direct head-to-head trials of retatrutide vs tirzepatide vs semaglutide have not been published — all comparisons are cross-trial.
  • Weight regain trajectory after discontinuation is not yet quantified for retatrutide specifically.
  • Cardiovascular outcomes trial (SELECT-equivalent for retatrutide) is ongoing — mortality benefit unknown.
  • GI tolerability at 12mg is higher than tirzepatide at equivalent doses — long-term titration strategies are still evolving.
  • FDA approval is not yet granted. Anything sold outside of clinical trial enrollment is a research-grade compound, not a prescription drug.
FAQ

Frequently Asked Questions

How much weight did retatrutide produce in Phase 3?

In the Phase 3 TRIUMPH trial, retatrutide produced 28.3% mean body weight loss at the 12mg dose over 80 weeks. Average absolute weight loss was approximately 70 lbs. 45% of participants lost 30% or more of body weight, and 65% on the top dose were no longer clinically obese (BMI < 30) at trial end.

When will retatrutide be FDA approved?

Following the positive TRIUMPH Phase 3 readout, Eli Lilly is expected to submit a new drug application (NDA) to the FDA. Industry estimates put potential FDA approval in late 2026 to 2027. Until approval, retatrutide is only available through clinical trials or as a research compound — it is not available by prescription.

How does retatrutide compare to tirzepatide and semaglutide in Phase 3?

Retatrutide produced 28.3% body weight loss at 80 weeks, compared with tirzepatide's ~22% (SURMOUNT-1, 72 weeks) and semaglutide's ~15% (STEP-1, 68 weeks). Retatrutide is the only triple agonist (GLP-1 + GIP + glucagon); tirzepatide is a dual agonist; semaglutide is GLP-1 only. The glucagon arm appears to drive higher energy expenditure and incremental fat loss.

What were the side effects in Phase 3?

Gastrointestinal side effects (nausea, vomiting, diarrhea) were the most common adverse events, consistent with the GLP-1 class. At the 12mg dose, GI events were modestly higher than tirzepatide at equivalent doses. Treatment discontinuation due to adverse events was 11.3% at the top dose. The 4mg dose had a dropout rate lower than placebo while still producing 19% body weight loss.

What does "no longer clinically obese" mean in the trial?

Clinical obesity is defined by a body mass index (BMI) of 30 or higher. In the Phase 3 TRIUMPH trial, 65% of participants on the 12mg dose reduced their BMI below 30 by week 80 — meaning they no longer met the medical definition of obesity. This is one of the strongest BMI category-shift signals ever reported in an obesity pharmaceutical trial.

Is the 4mg dose still useful?

Yes — the 4mg dose produced 19% body weight loss with a dropout rate lower than placebo. For people sensitive to GLP-1 side effects, the lower dose may offer a favorable tolerability-to-efficacy ratio that still exceeds semaglutide and matches tirzepatide at higher doses. 19% body weight loss is still clinically meaningful in any framework.

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🏆
Retatrutide Phase 2 Results
The NEJM Phase 2 trial that started it all — 24.2% body weight loss at 48 weeks.
→ ⚖️
Retatrutide vs Semaglutide vs Tirzepatide
Triple agonist vs dual vs single — the receptor-coverage explanation for the efficacy gap.
→ ⚠️
Retatrutide Side Effects
Complete GI tolerability, dose titration, and safety profile from TRIUMPH and Phase 2.
→ 🧠
Retatrutide Beyond Weight Loss
Brain, bone, testosterone & addiction effects of GLP-1 / GIP / glucagon triple agonism.
→ 🔥
Metabolic Adaptation on Retatrutide
Why retatrutide blunts the metabolic-rate drop that derails normal weight loss.
→ 📈
Retatrutide Before & After
Clinical weight-loss trajectory by week and dose — what the curve actually looks like.
→ 🛒
How to Get Retatrutide
Research peptide vendors, clinical trial enrollment, and the post-approval landscape.
→ 🔭
GLP-1 Pipeline 2026
Next-generation weight-loss drugs in clinical development — retatrutide, orforglipron, MariTide.
→
⚠️ Disclaimer

Educational purposes only. Not medical advice.

Retatrutide is investigational and not FDA approved for any indication. The Phase 3 TRIUMPH program is sponsored by Eli Lilly and Company; full results are subject to ongoing peer review and regulatory analysis. Cross-trial comparisons to tirzepatide and semaglutide are directional only — these compounds have not been studied head-to-head in published trials. Consult a physician before considering any GLP-1 / GIP / glucagon agonist.