Two new studies published in separate journals show that an experimental drug developed by Eli Lilly leads to meaningful weight loss.
One study, published in the Lancetand presented at the European Association for the Study of Diabetes, tested the drug retatrutide in people who were overweight or obese and had Type 2 diabetes: a population in which weight-loss medications have historically been less effective. People who took the highest dose lost about 18.8% of their starting body weight, while people who took a placebo lost 5.1%. About a third of the people in the study who took the highest dose of retatrutide lost at least 25% of their body weight, compared to 3% of those on placebo over the study period of 1.5 years.
“This is the most potent drug, showing the greatest percent weight loss in people with Type 2 diabetes with a pharmacological agent, shown to date,” says Dr. Juan Pablo Frias, medical director at the Los Angeles Institute for Metabolic Research and one of the Lancet study authors.
People in the study also showed improvement in their diabetes control. Of those who took the highest dose, 63% lowered their A1C to less than 6.5%—the threshold for diabetes—and lost at least 10% of their body weight.
In another study published in the New England Journal of Medicine, researchers reported similar weight-loss benefits in people who were overweight or obese but who did not have diabetes. In that study, people who took the highest dose of retatrutide lost about 25% of their starting body weight, while just 3.9% of people who took a placebo did the same. People taking the drug were also studied for other benefits; those with osteoarthritis in the knee reported lower pain scores than those on placebo, while people with obstructive sleep apnea also reported fewer apnea episodes than those taking placebo.
Retatrutide targets three weight-related hormones: GLP-1, GIP, and glucagon. Since each has specific receptors in the body and brain, targeting all three may be contributing to the more potent effects on weight for people with diabetes than drugs that target GLP-1 alone, like Ozempic and Wegovy (semaglutide), or GLP-1 and GIP together, as Mounjaro and Zepbound (tirzepatide) do. Zepbound is approved to not only control weight but to also treat obstructive sleep apnea, and Wegovy and Ozempic are approved to reduce the risk of heart disease.
In both studies, the side effects among people taking retatrutide were similar to those that have been reported with other GLP-1 medications, including GI issues such as abdominal cramps, nausea, vomiting, and diarrhea.
Eli Lilly says it plans to submit a request in early 2027 to the U.S. Food and Drug Administration to approve retatrutide based on these results.
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