Eli Lilly says retatrutide cut weight 20.8% over 80 weeks at top dose

The company plans to file for approval of the triple-hormone drug in the first quarter of 2027

Eli Lilly says its experimental drug retatrutide, given at a 12mg dose, produced average weight loss of 49.6 lb, or 20.8%, over 80 weeks in a clinical trial. Participants who started with a BMI of at least 35 lost 60.8 lb, or 23.4%, and 59.5% of those on the 12mg dose no longer met the BMI threshold for obesity by the end of the trial. The company also reported that retatrutide lowered A1C, a measure of blood sugar control, in participants who had both obesity and type 2 diabetes.

Retatrutide is a triple agonist, meaning it targets three separate hormone receptors involved in appetite and metabolism. Eli Lilly plans to file a biologics licence application for the drug in the first quarter of 2027, putting it several years behind Zepbound, the company's approved obesity drug, in the regulatory process.

The result extends a pattern in which Eli Lilly's obesity drugs have outperformed Novo Nordisk's in head-to-head comparisons. Zepbound showed 20.2% weight loss against 13.7% for Novo Nordisk's Wegovy over 72 weeks. Novo Nordisk has pointed to other data in response: a real-world study presented at the European Association for the Study of Diabetes found its semaglutide, dosed at 2mg, linked to a 6% lower risk of serious cardiovascular events than Eli Lilly's tirzepatide in adults with type 2 diabetes.

Because retatrutide is still years from approval, the new figures are a pipeline update rather than an immediate business catalyst. But they add to a run of trial results that have favoured Eli Lilly over Novo Nordisk in the obesity and metabolic drug market, an area where Eli Lilly already holds about 70% of new prescriptions among older GLP-1 patients. A third-generation candidate with this level of efficacy would give the company a way to extend that lead once Zepbound's current run in the market matures.