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Eli Lilly dropped topline results for the TRIUMPH-1 Phase 3 trial yesterday, May 21, 2026. The numbers are hard to ignore.
Retatrutide (LY3437943) is a triple hormone receptor agonist. It hits GLP-1, GIP, and glucagon receptors at the same time. That glucagon piece is what makes it different from tirzepatide (Zepbound), which only targets GLP-1 and GIP.
The Trial
Weight Loss Results (placebo-adjusted)
At 12 mg, over 62% of participants lost 25% or more of their body weight. Nearly 1 in 3 lost 35% or more. That's the kind of result you'd expect from bariatric surgery, not a weekly injection.
To put that in perspective:
Side effects were mostly the usual GLP-1 stuff: nausea, diarrhea, constipation, vomiting. One signal worth paying attention to is dysesthesia (abnormal skin sensations), which showed up in 5-12% of participants. That's probably coming from the glucagon agonism. Discontinuation at 12 mg was around 11%.
What comes next:
If you want to get your hands on it in Australia, @Prymal carries reta along with a solid range of other peptides. His intro thread is worth a read: Prymal Peptides Intro Thread
ClinicalTrials reference: NCT05929066
Retatrutide (LY3437943) is a triple hormone receptor agonist. It hits GLP-1, GIP, and glucagon receptors at the same time. That glucagon piece is what makes it different from tirzepatide (Zepbound), which only targets GLP-1 and GIP.
The Trial
- 2,339 participants, obese or overweight, no T2D
- 80 weeks, once-weekly subcutaneous injection
- Doses tested: 4 mg, 9 mg, 12 mg vs placebo
- Mean starting weight: ~112.7 kg, BMI ~40
Weight Loss Results (placebo-adjusted)
- 4 mg: ~19% body weight lost (~21 kg)
- 9 mg: ~23-25% (~26-28 kg)
- 12 mg: ~28.3% (~32 kg)
- Extended cohort at max tolerated dose: 30.3%
At 12 mg, over 62% of participants lost 25% or more of their body weight. Nearly 1 in 3 lost 35% or more. That's the kind of result you'd expect from bariatric surgery, not a weekly injection.
To put that in perspective:
- Semaglutide (Wegovy) tops out around 15%
- Tirzepatide (Zepbound) tops out around 21%
- Retatrutide just hit 30.3%
Side effects were mostly the usual GLP-1 stuff: nausea, diarrhea, constipation, vomiting. One signal worth paying attention to is dysesthesia (abnormal skin sensations), which showed up in 5-12% of participants. That's probably coming from the glucagon agonism. Discontinuation at 12 mg was around 11%.
What comes next:
- Full data presented at ADA Scientific Sessions, June 2026
- TRIUMPH-2 (T2D) and TRIUMPH-3 (CVD) readouts later this year
- FDA approval projected for 2027
If you want to get your hands on it in Australia, @Prymal carries reta along with a solid range of other peptides. His intro thread is worth a read: Prymal Peptides Intro Thread
ClinicalTrials reference: NCT05929066
