Eli Lilly's Retatrutide Produces Up to 28.3% Weight Loss in Phase 3 Trial
Phase 3 TRIUMPH-1 found weekly retatrutide led to up to 28.3% average weight loss at 12mg over 80 weeks, with notable GI side effects and plans to seek approval.
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Overview
Eli Lilly said its phase 3 TRIUMPH-1 trial showed weekly retatrutide at 12mg produced an average 28.3% weight loss (70.3 pounds) over 80 weeks among participants who stayed on the drug.
The results matter because Lilly and outside experts said the losses exceed those seen with current GLP-1 drugs and are on par with bariatric surgery for some patients.
Ania Jastreboff, who led the study, said retatrutide yielded clinically meaningful weight reduction and cardiometabolic improvements, and Lilly reported no cardiac or liver issues observed in the trial.
Across roughly 2,300 to 2,500 participants, average weight loss was about 19.0% at 4mg, 25.9% at 9mg and 28.3% at 12mg, with roughly 65% on 12mg reducing BMI below 30 and about a third reporting nausea or diarrhea.
Lilly said it expects to file for FDA approval as early as this year and is conducting further studies, including a head-to-head comparison with tirzepatide with results expected toward the end of 2026 or beginning of 2027.
Analysis
Center-leaning sources frame coverage positively by foregrounding large efficacy numbers, market-upside projections, and company optimism through prominently placed trial results and analyst revenue estimates. Editorial choices downplay risks by relegating side-effect details later and using hedged language ("generally consistent", "most were mild"). source content includes direct company quotes and analyst estimates.