Retatrutide Just Hit 30.3% Weight Loss With No Plateau — Every TRIUMPH-1 Number
⚡ Key Takeaway
TRIUMPH-1 delivered: 28.3% average weight loss at 12 mg over 80 weeks. 45.3% of participants lost ≥30% of body weight. In the 104-week extension, those with BMI ≥35 hit 30.3% loss (averaging 85 lbs) — with no plateau. This is the largest weight loss ever recorded in a Phase 3 obesity trial.
On May 21, 2026, Eli Lilly announced topline results from TRIUMPH-1, the pivotal Phase 3 obesity trial for retatrutide. The numbers aren’t just good — they redefine the pharmacologic ceiling for weight loss. Here’s every number that matters.
The Headline Numbers
| Dose | Weight Loss (80 wk) | Avg Lbs Lost | ≥5% Threshold | ≥30% Threshold |
|---|---|---|---|---|
| 12 mg | 28.3% | ~70.3 lbs | >90% | 45.3% |
| 9 mg | 25.9% | ~64 lbs | >90% | — |
| 4 mg | 19.0% | ~47 lbs | >85% | — |
| Placebo | 2.2% | ~5.5 lbs | — | — |
The trial enrolled 2,339 adults with obesity or overweight plus at least one weight-related comorbidity (hypertension, dyslipidemia, sleep apnea, or knee osteoarthritis), without type 2 diabetes. All three active doses met primary and key secondary endpoints versus placebo.
The No-Plateau Finding
This is the number that changes the conversation. In a prespecified blinded extension, participants with baseline BMI ≥35 who completed the 80-week main trial and tolerated their medication continued to 104 weeks. The 12 mg group hit 30.3% average body weight reduction — an average of approximately 85 pounds.
The weight-loss curve was still descending at 104 weeks. No plateau. For context, semaglutide weight loss typically plateaus around 60–68 weeks. Tirzepatide shows similar flattening in the 72-week range. Retatrutide at 104 weeks showed no sign of the metabolic adaptation that limits every other pharmacologic intervention.
Whether this reflects the glucagon receptor component (which drives energy expenditure through thermogenesis and hepatic lipid oxidation, mechanisms absent in GLP-1-only or GLP-1/GIP-dual agents) or some other aspect of triple agonism isn’t yet clear. But the functional result is unprecedented: patients lost more weight the longer they took retatrutide, with no ceiling in sight at two years.
How TRIUMPH-1 Compares
| Trial | Drug | Duration | Max Weight Loss |
|---|---|---|---|
| TRIUMPH-1 | Retatrutide 12 mg | 80 wk (104 ext) | 28.3% (30.3% ext) |
| SURMOUNT-1 | Tirzepatide 15 mg | 72 wk | 22.5% |
| STEP-1 | Semaglutide 2.4 mg | 68 wk | 14.9% |
| TRIUMPH-4 | Retatrutide 12 mg | 68 wk | 28.7% (OA subpop) |
The 28.3% result at 80 weeks beats tirzepatide’s best by roughly 5.8 percentage points and semaglutide by 13.4 points. The 30.3% figure at 104 weeks exceeds anything previously seen outside bariatric surgery.
Safety Profile
The GI side-effect profile follows the class pattern but at higher rates:
| Side Effect | 12 mg Rate | 9 mg Rate | 4 mg Rate | Placebo |
|---|---|---|---|---|
| Nausea | 42.4% | — | — | — |
| Diarrhea | 32.0% | — | — | — |
| Constipation | 26.1% | — | — | — |
| Vomiting | 25.3% | — | — | — |
The most notable non-GI finding: dysesthesia (abnormal skin sensations — tingling, numbness, prickling) was reported in approximately 1 in 10 participants at the highest doses. Most cases were mild to moderate, and the majority resolved during treatment while participants continued taking retatrutide. We cover this signal in depth in our dedicated dysesthesia analysis.
The 4 mg dose-escalation arm showed a discontinuation rate lower than placebo, suggesting the slow titration protocol is well-tolerated enough that some patients found the experience better than receiving no treatment.
The NDA Timeline
TRIUMPH-1 is one of eight trials in the retatrutide Phase 3 program. With two successful readouts (TRIUMPH-1 and TRIUMPH-4), Lilly is positioned to file a New Drug Application:
- Q3–Q4 2026: Additional TRIUMPH readouts for type 2 diabetes (TRIUMPH-2), cardiovascular disease (TRIUMPH-3), and other indications. Lilly has seven more readouts expected this year.
- Late 2026 to early 2027: Most likely NDA filing window
- 2027–2028: Potential FDA approval and market launch
Retatrutide remains investigational. It is not approved for any indication, anywhere in the world. All current access is research-use-only.
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At 80 weeks, the 12 mg dose produced 28.3% average weight loss (~70.3 lbs). In the 104-week extension for participants with BMI 35+, the 12 mg group reached 30.3% loss (~85 lbs). The 9 mg dose hit 25.9% and the 4 mg dose hit 19.0%.
In matched-duration Phase 3 trials, retatrutide 12 mg produced 28.3% weight loss vs tirzepatide’s 22.5% (SURMOUNT-1) and semaglutide’s 14.9% (STEP-1). No head-to-head trial exists yet; TRIUMPH-5 is the closest active-comparator trial.
Retatrutide is investigational and not approved anywhere. Lilly is expected to file an NDA in late 2026 to early 2027. Potential FDA approval and market launch would follow in 2027-2028.
Common side effects at 12 mg: nausea (42.4%), diarrhea (32.0%), constipation (26.1%), vomiting (25.3%). Dysesthesia (abnormal skin sensations) was reported in about 1 in 10 participants at the highest doses.
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