Retatrutide is Eli Lilly's investigational once-weekly injectable that activates three hormone receptors at once — GIP, GLP-1 and glucagon — which is why it's called a "triple agonist." In TRIUMPH-1, its pivotal Phase 3 obesity trial, participants on the highest dose lost an average of 28.3% of body weight at 80 weeks (12 mg, efficacy estimand), and 45.3% of that group lost 30% or more. [1] Five Phase 3 trials have now read out positive, and Lilly plans to submit retatrutide to the FDA in Q1 2027. [7]
Retatrutide is not FDA-approved and cannot be prescribed. Per Lilly, it is "available only to participants in Lilly's clinical trials" [5] — plus, since August 2026, a physician-requested expanded access program. [6] Anything sold online as "research" or compounded retatrutide is not legitimate retatrutide.
How it works
Semaglutide (Ozempic, Wegovy) activates one receptor: GLP-1. Tirzepatide (Mounjaro, Zepbound) activates two: GLP-1 and GIP. Retatrutide adds a third mechanism — the glucagon receptor — which is thought to increase energy expenditure alongside the appetite effects of the other two pathways.
You'll sometimes see retatrutide nicknamed "GLP-3" online. That isn't a drug class or a medical term — and the same nickname is used as a code name by sellers of illegitimate products, which is a reason to be careful anywhere you see it.
The Phase 3 results so far
| Trial | Population | Headline result | Readout |
|---|---|---|---|
| TRIUMPH-1 | Obesity/overweight without diabetes (n=2,339) | 28.3% at 80 wk (12 mg); 25.9% (9 mg); 19.0% (4 mg) — efficacy estimand | May 21, 2026 [1] |
| TRIUMPH-2 | Obesity + type 2 diabetes | 20.8% at 80 wk (12 mg); A1C −up to 1.6 pts | Jul 23, 2026 [2] |
| TRIUMPH-3 | Severe obesity + established CVD (n=1,949) | 22.6% (12 mg) vs 3.2% placebo | Jul 23, 2026 [2] |
| TRIUMPH-4 | Obesity + knee osteoarthritis | 28.7% at 68 wk (12 mg); WOMAC pain −up to 75.8% | Dec 11, 2025 [3] |
In a TRIUMPH-1 extension among participants with BMI ≥35, average weight loss reached 30.3% at 104 weeks. [1] The Phase 2 trial published in NEJM in 2023 — about 24.2% at 48 weeks on the highest dose — is now historical context rather than the headline. [4]
On safety: the most common adverse events are gastrointestinal (nausea, diarrhea, constipation, decreased appetite, vomiting). A newer signal not seen in Phase 2 is dysesthesia — abnormal skin sensation — reported in 12.3–12.5% of participants on the higher TRIUMPH-1 doses versus 0.9% on placebo; Lilly says events were generally mild to moderate and mostly resolved. [1] [8]
Where it stands
- ConfirmedFive Phase 3 trials have read out positive; Lilly says TRIUMPH-2 and TRIUMPH-3 complete the data package for global submissions. [2]
- ConfirmedAn expanded access program opened Aug 3, 2026 — for patients who meet medical criteria and can't join a trial; the treating physician must apply. [6]
- ProjectedU.S. FDA submission planned for Q1 2027 (pushed back from "by end of 2026" to finish the manufacturing/quality package). [7]
There is no brand name, no price and no approval date. The live record is on our FDA approval tracker.