Retatrutide Hits 28.3% Weight Loss in TRIUMPH-1
Eli Lilly's TRIUMPH-1 Phase 3 trial showed retatrutide at 12 mg cut average body weight by 28.3% over 80 weeks — topping every approved GLP-1 drug on the market.
May 21, 2026 · 2 min read
Eli Lilly today released topline results from TRIUMPH-1, the first pivotal Phase 3 trial of retatrutide for obesity, showing that the highest dose group lost an average of 28.3% of body weight — 70.3 pounds — over 80 weeks. The result exceeds any weight loss achieved in trials for currently approved GLP-1 drugs.
What happened
TRIUMPH-1 enrolled adults with obesity or overweight without type 2 diabetes and randomized them to once-weekly injectable retatrutide at three dose levels or placebo over 80 weeks.
Key results by dose group:
| Dose | Mean weight loss | Mean lbs lost |
|---|---|---|
| 12 mg | 28.3% | 70.3 lbs |
| 4 mg | 19.0% | 47.2 lbs |
| Placebo | ~3% | — |
At the 12 mg dose, 45.3% of participants achieved ≥30% weight loss — a threshold that approaches or exceeds typical surgical outcomes. In an extension cohort of participants with baseline BMI ≥ 35, mean weight loss reached 30.3% at 104 weeks.
The trial met its primary endpoint and Lilly indicated it plans to include TRIUMPH-1 data in a planned NDA submission.
Why it matters
The 28.3% result at the highest dose clears a bar no approved injectable GLP-1 has reached. For context:
- Tirzepatide (SURMOUNT-1): ~22.5% at 15 mg over 72 weeks
- Semaglutide (STEP-1): ~14.9% at 2.4 mg over 68 weeks
The additional margin comes from retatrutide's third receptor target: glucagon. Where tirzepatide activates GLP-1 and GIP, retatrutide adds glucagon receptor agonism — which increases resting energy expenditure and fat mobilization on top of appetite suppression. The TRIUMPH-1 data suggests that mechanism produces real, clinically meaningful additional weight loss rather than just a marginal gain.
For patients who have had inadequate response to tirzepatide — estimated at 20–30% of users — retatrutide could represent the next meaningful step.
What to watch
Lilly has indicated an NDA submission is planned, with an FDA review window that could lead to approval in 2027. Results from TRIUMPH-2 (obesity with type 2 diabetes) and TRIUMPH-3 (obesity with established cardiovascular disease) are expected later in 2026 and will shape the full label.
The cardiovascular outcomes data from TRIUMPH-3 is particularly consequential: whether retatrutide can replicate the 20% MACE reduction seen with semaglutide in SELECT will determine whether it earns a cardioprotective indication alongside its weight loss label.
Sources
- Lilly press release — TRIUMPH-1 topline results
- CNBC: Eli Lilly weight loss drug retatrutide clears obesity trial
What is retatrutide? — how the triple-agonist mechanism differs from approved GLP-1s Retatrutide vs tirzepatide efficacy — how trial data compares
Sources