At a glance
- The 80-week TRIUMPH-2 study enrolled 1,152 adults.
- The published treatment-regimen analysis found 18.8% average weight loss with the highest dose.
- Gastrointestinal adverse events were more common than with placebo.
Retatrutide produced substantial weight loss in adults with obesity and type 2 diabetes in the phase 3 TRIUMPH-2 trial, published online in The Lancet September 29. The highest-dose group lost an average 18.8% of body weight over 80 weeks in the treatment-regimen analysis, compared with 5.1% for placebo. [1]
What was tested
The randomized, double-blind trial enrolled 1,152 adults at 92 centers across eight countries. Participants received weekly placebo or retatrutide injections at 4, 9 or 12 milligrams. They had a body mass index of at least 27 and type 2 diabetes. [1]
Retatrutide targets three hormone receptors: GIP, GLP-1 and glucagon. Lilly’s September 29 announcement describes it as investigational and says the findings were presented at the European Association for the Study of Diabetes meeting in Milan. The company is studying the molecule for several metabolic conditions, rather than marketing it as an approved treatment. [2]
Why different weight-loss figures appear
Lilly’s release highlights 20.8% average weight loss with 12 milligrams using its efficacy analysis. The release defines that approach as estimating outcomes had participants remained on treatment without prohibited weight-management interventions. The published trial’s 18.8% figure uses a treatment-regimen analysis. These are different analyses of the same study, not two separate trials. [2] [1]
Adverse events and the next step
The published abstract reports more diarrhea and nausea with retatrutide than placebo. Discontinuation because of adverse events or death was more frequent in the 9- and 12-milligram groups than with placebo. Lilly funded the study, with company employees among the authors. [1]
Lilly says it plans to submit a Biologics License Application to the US Food and Drug Administration in the first quarter of 2027. Its announcement says retatrutide cannot legally be sold or marketed for human use. The reported benefits therefore remain clinical-trial evidence, while the planned filing is a future regulatory step rather than an approval or a date when patients can obtain the drug. [2]