This treatment is in clinical trials and has not been approved by the FDA or any regulatory authority. It is not available for prescription. Current stage: Phase 3 (TRIUMPH programme) — first Phase 3 result published 2026. Estimated approval: 2027 (estimated — not confirmed) — subject to change.
Retatrutide
Eli Lilly · Code: LY3437943
A triple GIP, GLP-1, and glucagon receptor agonist. The first Phase 3 result (TRIUMPH-4, 2026) showed 28.7% average weight loss at 68 weeks — the highest weight loss ever recorded in a Phase 3 randomised controlled trial. The addition of glucagon receptor agonism on top of GIP and GLP-1 may further boost metabolic rate and fat burning beyond what dual agonists achieve.
Quick read · 4 min
- •Retatrutide is an investigational drug — it has not yet been approved by any regulatory authority
- •Best trial result so far: up to 28.7% average weight loss
- •Current stage: Phase 3 (TRIUMPH programme) — first Phase 3 result published 2026
- •Expected approval: 2027 (estimated — not confirmed) — this is an estimate and not confirmed
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026
How it works
Activates three receptors simultaneously: GIP (reduces appetite, enhances fat storage signalling), GLP-1 (reduces appetite, slows gastric emptying), and glucagon (increases metabolic rate and fat burning). The triple mechanism may produce synergistic weight loss beyond what dual agonists achieve.
Phase 2 trial data by dose
In the Phase 2 trial (where people were randomly assigned to different doses or a dummy pill), participants on different doses lost the following amounts of weight. Phase 3 data is pending.
| Dose | At 24 weeks | At 48 weeks |
|---|---|---|
| 1 mg | –7.2% | –8.7% |
| 4 mg | –12.9% | –17.1% |
| 8 mg | –17.3% | –22.8% |
| 12 mg | –17.5% | –24.2% |
| Placebo | –1.6% | –2.1% |
Phase 3 trial results
In the following Phase 3 trials, participants were randomly assigned to Retatrutide or a dummy pill.
In the TRIUMPH-4 trial, participants lost an average of 28.7% of their body weight at the 12 mg dose (about 71.2 lbs / 32.3 kg on average) — alongside a 75.8% reduction in knee pain. At the 9 mg dose, average weight loss was 26.4%. Placebo: 2.1% weight loss.
Phase 3 programme
- ◆TRIUMPH-4 (published 2026): Adults with obesity and knee osteoarthritis — 28.7% weight loss at 68 weeks
- ◆TRIUMPH-1: Adults with obesity, no type 2 diabetes — data expected 2026
- ◆TRIUMPH-2: Adults with obesity and type 2 diabetes — data expected 2026
- ◆TRIUMPH-3: Adults with Class II/III obesity and established cardiovascular disease — data expected 2026
Side effects (early-stage data)
Frequencies from Phase 2 trial data. Final Phase 3 safety profile may differ.
Notable findings
- ✓28.7% average weight loss at 68 weeks (TRIUMPH-4 Phase 3) — highest ever in a Phase 3 RCT
- ✓75.8% reduction in knee osteoarthritis pain alongside weight loss (TRIUMPH-4)
- ✓Cardiometabolic improvements across blood pressure, lipids, and blood sugar (Phase 2 + Phase 3)
- ✓100% of participants at 8 mg and 12 mg achieved ≥5% weight loss in Phase 2
Community insights
These are personal experiences shared in public online communities — not medical advice.
“Phase 2 participants described losing weight faster than with Wegovy or Zepbound at similar timepoints — but this is very early data and Phase 3 will give the real picture.”
Sources & references
- [1]Phase 2 randomised controlled trial (NEJM 2023)338 adults with obesity, no type 2 diabetes · 48 weeksAt 12 mg dose: 24.2% mean weight loss at 48 weeks — weight had not plateaued. 100% achieved ≥5% loss; 93% ≥10%; 83% ≥15%. GI side effects consistent with incretin class. Discontinuation: 6–16% across doses.New England Journal of Medicine (2023) ↗
- [2]TRIUMPH-4 Phase 3 trial (published 2026)Adults with obesity and knee osteoarthritis (average BMI 40.4, baseline weight ~112.7 kg) · 68 weeks28.7% mean weight loss at 12 mg dose (about 71.2 lbs average). 26.4% at 9 mg. Knee pain (WOMAC) reduced by 75.8% vs 40.3% placebo. Cardiometabolic improvements including reduced blood pressure and cholesterol. First successful Phase 3 trial.Eli Lilly press release / investor.lilly.com (2026) ↗