Eli Lilly’s retatrutide drug achieved up to 28.3 percent weight loss in the Phase 3 TRIUMPH-1 clinical trial.
The results, presented in May 2026, position retatrutide as the most effective obesity drug tested to date.
What the Retatrutide TRIUMPH-1 Weight Loss Trial Found
Participants on the highest 12 mg dose of retatrutide lost an average of 28.3 percent of body weight over 80 weeks.
That is equivalent to roughly 70 pounds for someone starting at 247 pounds, based on trial participant averages.
More than 45 percent of participants lost at least 30 percent of their body weight during the study period.
A weight loss of 30 percent is a level typically associated with bariatric surgery rather than medication alone.
Full trial details are published at BioPharm International retatrutide trial results in BioPharm International for medical and research audiences.
How Retatrutide Differs From Other Weight Loss Drug Options
Retatrutide targets three receptors simultaneously: GIP, GLP-1, and glucagon, making it a triple-acting obesity drug.
Existing drugs like semaglutide, sold as Ozempic and Wegovy by Novo Nordisk, target only the GLP-1 receptor.
Tirzepatide, sold as Mounjaro and Zepbound by Eli Lilly, targets both GIP and GLP-1 but not the glucagon receptor.
Adding the glucagon target appears to deliver additional fat burning and metabolic benefits beyond dual-agonist drugs.
Retatrutide is a once-weekly injectable taken the same way as other GLP-1 class medications on the market.
Extended Retatrutide Results and Lilly Drug Pipeline
A prespecified blinded extension of the TRIUMPH-1 trial showed even greater results by week 104 of the study.
Participants on 12 mg retatrutide reached an average of 85 pounds of weight loss, equivalent to 30.3 percent.
Cardiometabolic improvements accompanied the weight loss, including a 24 centimeter reduction in average waist size.
Favorable changes were also seen in non-HDL cholesterol, triglycerides, systolic blood pressure, and inflammation markers.
Full extended data from the TRIUMPH-1 trial is covered at AJMC coverage of TRIUMPH-1 trial data with detailed analysis of the results.
What Retatrutide Means for the Future of Obesity Treatment
Retatrutide could reshape the obesity treatment landscape if approved by the FDA following regulatory review.
It may offer an option for patients who have not achieved their weight goals on semaglutide or tirzepatide alone.
Eli Lilly is expected to submit retatrutide for FDA review in late 2026 or early 2027, pending final data.
The drug joins a pipeline of next-generation obesity treatments that go beyond the original GLP-1 class.
Weight loss trials show retatrutide may also reduce liver fat and improve insulin sensitivity in diabetic patients.
Analysts predict retatrutide could generate over $10 billion annually if approved and priced similarly to Zepbound.
To understand the broader health impact of GLP-1 drugs, read our piece on GLP-1 drugs and their broader health benefits.
For those researching weight loss science, our post on AI tools for health science research and study shares AI tools for health topics.
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