Landmark Trial Results Published for Retatrutide
Eli Lilly's experimental drug retatrutide helped people with type 2 diabetes lose up to 60 pounds — roughly 23% of their body weight — according to late-stage trial results published Tuesday in The Lancet. The findings, presented simultaneously at the European Association for the Study of Diabetes annual meeting in Milan, mark the most weight loss ever recorded in a medication trial for diabetes patients, a population that typically struggles more with weight reduction.
The phase 3 TRIUMPH-2 trial followed more than 1,100 adults with type 2 diabetes and overweight or obesity across eight countries. Participants, who had an average starting weight of about 234 pounds and a BMI of roughly 38, were randomly assigned to receive weekly injections of retatrutide at 4 mg, 9 mg, or 12 mg, or a placebo, for 80 weeks. Those on the highest dose lost an average of 18.8% of their body weight, while nearly half (47%) lost at least 20% and almost a third (31%) shed 25% or more. The placebo group lost 5.1%.
"Retatrutide is truly an advance in diabetes care," said Dr. Susan Spratt, an endocrinologist at Duke Health who was not involved in the trial. "It rivals gastric bypass surgery without the surgery."
What Sets Retatrutide Apart
Retatrutide is a triple agonist, meaning it mimics three hormones: GLP-1, GIP, and glucagon. Existing drugs like semaglutide (Wegovy, Ozempic) target one receptor, while tirzepatide (Zepbound, Mounjaro) targets two. The addition of glucagon is believed to increase energy expenditure, potentially explaining the enhanced weight loss. The drug has been nicknamed the "Godzilla" of weight-loss drugs.
In a separate trial published in the New England Journal of Medicine — the TRIUMPH-1 study — retatrutide helped patients without type 2 diabetes who had obesity or were overweight lose up to 70 pounds, or 25% of their body weight on average, after 80 weeks. Among those with severe obesity, weight loss reached up to 85 pounds, or 30% of body weight, after 104 weeks — results on par with bariatric surgery.
Broader Health Benefits Emerge
Beyond weight loss, the TRIUMPH-1 trial revealed significant improvements in obesity-related conditions. Patients with knee osteoarthritis experienced greater reductions in pain compared to placebo, with statistically significant differences at week 80. Those with obstructive sleep apnea saw marked reductions in apnea-hypopnea events — decreases of roughly 23 to 34 events per hour on retatrutide, versus about 10 on placebo.
Researchers also reported improvements in blood sugar control, cardiometabolic risk factors, and reduced inflammation. "Retatrutide demonstrated substantial reduction in body weight alongside glycaemic control and cardiometabolic risk factors," the authors wrote in The Lancet, noting a safety profile generally similar to other GLP-1 receptor agonists.
Adverse events were predominantly mild to moderate gastrointestinal effects, such as nausea and diarrhea. Dose-dependent hypotension symptoms were more frequent in patients taking concurrent antihypertensive medications. Eli Lilly has not yet submitted retatrutide for FDA approval but plans to file early next year.
The Stakes for Diabetes and Obesity Treatment
These results arrive amid soaring demand for effective weight-loss treatments. Unauthorized, copycat versions of retatrutide are already circulating, underscoring both the hype and the risks of unregulated products. For people with type 2 diabetes, the new data could reshape expectations: previous trials of semaglutide and tirzepatide showed weight losses of up to 10% and 15%, respectively, in this population.
"People with type 2 diabetes have historically lost less weight on obesity medications than people without diabetes," said Dr. Gitanjali Srivastava, an obesity medicine specialist at Vanderbilt University Medical Center. "These are impressive results, and what makes them notable is the population."
If approved, retatrutide could become the most potent obesity medication on the market, offering an alternative to surgery for some patients. However, questions remain about long-term safety, cost, and access — challenges that have plagued earlier GLP-1 drugs.
What This Changes
Retatrutide's trial results signal a new frontier in metabolic medicine, where drugs target multiple hormonal pathways to achieve unprecedented weight loss and tackle related conditions like sleep apnea and arthritis. As Eli Lilly prepares its regulatory submission, the findings are likely to intensify competition in the booming obesity drug market and raise hopes for patients who have struggled with existing options.
Still, experts caution that these results are from controlled trials and may not reflect real-world outcomes. The medical community will be watching closely as retatrutide moves toward potential approval — and as researchers explore whether its triple-agonist mechanism offers benefits beyond the scale.
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