What were the topline results of Eli Lilly’s (NYSE:LLY) TRIUMPH-1 trial for retatrutide?

The Phase 3 TRIUMPH-1 trial showed that adults with obesity or overweight lost up to 30.3% of their body weight over 104 weeks at the highest 12-mg dose. Participants in the placebo group lost only 2.2% on average.

How effective was retatrutide at different doses?

At 12 mg, average weight loss reached 28.3% initially and 30.3% in a 104-week extension. The 9-mg dose yielded 25.9% weight loss, and the 4-mg dose achieved 19%, all significantly above placebo.

How many participants were included in the TRIUMPH-1 study?

The trial enrolled 2,339 adults without diabetes, providing a robust dataset for evaluating retatrutide’s efficacy and safety across multiple doses.

What metabolic hormones does retatrutide target?

Retatrutide is a first-in-class molecule that activates three metabolic hormones: GIP, GLP-1, and glucagon, helping regulate appetite, insulin response, and energy balance.

Did retatrutide show benefits beyond weight loss?

Yes. Participants also experienced improvements in cardiometabolic markers, including reduced waist circumference, lower blood pressure, and better cholesterol levels.

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Eli Lilly experimental obesity drug Retatrutide hits up to 30% weight loss in pivotal trial

Written by Liezl GambePublished May. 21 2026Last Updated May. 21 2026

Eli Lilly (NYSE:LLY) announced historic topline results from its Phase 3 TRIUMPH-1 clinical trial, showing that its next-generation investigational drug, retatrutide, helped adults with obesity or overweight lose an average of up to 30.3% of their body weight.

The 80-week primary trial evaluated the efficacy and safety of retatrutide—a first-in-class molecule that targets three different metabolic hormones: GIP, GLP-1, and glucagon—in 2,339 adults without diabetes.

At the highest dose of 12 milligrams, participants achieved an average weight loss of 28.3%, or 70.3 pounds, compared to just 2.2% for those in the placebo group.

Middle and lower doses also demonstrated significant efficacy, with the 9-milligram dose yielding a 25.9% reduction and the 4-milligram dose achieving a 19% reduction.

In a pre-specified 104-week study extension tracking individuals with a baseline body mass index (BMI) of 35 or higher, the weight loss trajectory continued, reaching an average reduction of 30.3%—equivalent to 85.0 pounds—at the 12-milligram dose.

The data marks a significant milestone in the competitive obesity market, as a high proportion of participants reached the threshold of losing 25% to 35% of their total body mass, effectively dropping their overall BMI below 30.

The treatment also led to broad improvements across key cardiometabolic risk markers, including waist circumference, blood pressure, and cholesterol levels.

Safety and tolerability findings were consistent with the broader class of incretin-based metabolic therapies.

Gastrointestinal events, such as nausea, diarrhea, vomiting, and constipation, were the most frequently reported adverse effects compared to the placebo.

Researchers also noted an increased frequency of certain sensory and urinary side effects among participants receiving the active treatment.

Indianapolis-based Eli Lilly, which already dominates the weight-management sector with its dual-agonist injection Zepbound, is positioning retatrutide as the vanguard of its next-generation metabolic pipeline.

Additional clinical readouts from the broader TRIUMPH clinical program are expected to continue later this year.