Eli Lilly has announced that its new weight-loss drug, retatrutide, has led to an average weight loss of up to 28.3% in a phase three trial, outperforming existing obesity medications. The once-weekly injection, a triple hormone receptor agonist, helped participants on the highest dose lose an average of 70.3lb over 80 weeks.
The trial involved 2,339 adults with obesity or overweight and at least one weight-related comorbidity, but without diabetes. Participants received doses of 4mg, 9mg, 12mg, or a placebo. Those on 9mg lost an average of 25.9% of body weight, while the 4mg group lost 19.0%.
Dr Susan Spratt of Duke Health called it the largest weight loss seen in any medication trial. The drug also helped 65.3% of participants on the 12mg dose reduce their BMI below 30, including 37.5% of those who started with a BMI of 40 or higher.
Retatrutide targets GLP-1, GIP, and glucagon receptors, a combination not found in other drugs like Zepbound or Wegovy. Common side effects included nausea, diarrhoea, and constipation, with nausea affecting up to 42.4% of those on the highest dose versus 14.8% on placebo.
Lead researcher Ania Jastreboff noted that every dose resulted in clinically meaningful weight reduction and improvements in cardio-metabolic health. The findings suggest retatrutide could offer significant benefits beyond weight loss.
