Lilly retatrutide achieves 28% weight loss in Phase 3 trial
The triple-hormone drug helped patients lose an average of 70 pounds over 80 weeks, with Lilly seeking FDA approval this year in a blow to Novo Nordisk's competing ambitions.
May 21st 2026 · World
Eli Lilly announced Thursday that its next-generation weight loss drug retatrutide succeeded in a crucial late-stage trial, helping patients lose up to 28.3% of their body weight at the highest dose over 80 weeks. The Phase 3 trial of approximately 2,500 patients showed that those taking the highest dose lost an average of 70.3 pounds, with roughly 45% achieving at least 30% weight loss comparable to results typically seen with bariatric surgery. A lower 4-milligram dose demonstrated 19% weight loss with fewer side effects, leading Lilly to anticipate filing for Food and Drug Administration approval as early as this year. What sets retatrutide apart from existing treatments like Wegovy and Zepbound is its mechanism of action targeting three hormone pathways: GLP-1, GIP, and glucagon. This "triple G" approach appears to produce more potent effects on appetite and metabolism than drugs targeting only one or two hormones. Tirzepatide, the active ingredient in Lilly's Zepbound, mimics only GLP-1 and GIP, while Novo Nordisk's semaglutide targets only GLP-1. The most common side effects were gastrointestinal issues including nausea (42% at highest dose), diarrhea (32%), and constipation (26%), consistent with other GLP-1 medications. No cardiac or liver issues were observed, though a slightly higher rate of urinary tract infections was noted compared to placebo. The results position retatrutide as a potential next pillar in Lilly's obesity portfolio following Zepbound and the newly launched pill Foundayo. Analysts estimate the drug could generate $3.8 billion in sales by 2030 and help Lilly maintain its market lead in the booming weight loss segment projected to be worth $100 billion by the 2030s. Lilly currently holds 60.1% of the U.S. obesity and diabetes drug market compared to Novo's 39.4%, though Novo recently agreed to pay up to $2 billion for rights to a competing three-hormone drug from a Chinese company. That treatment, however, remains years away from reaching patients.