Experimental Lilly Drug Produces Large Weight Loss in Type 2 Diabetes Patients

An experimental weekly injection from Eli Lilly helped people with Type 2 diabetes lose roughly a fifth of their body weight and sharply lowered their blood sugar in a large late-stage trial, results that suggest a new and more powerful generation of obesity drugs is on the way.

The drug, retatrutide, was tested in more than 1,100 adults with Type 2 diabetes who also had obesity or were overweight. Participants were randomly assigned to one of three weekly doses or a placebo for 80 weeks. They started at an average weight of about 234 pounds. The findings were presented at the annual meeting of the European Association for the Study of Diabetes in Milan and published in The Lancet.

According to Lilly, people on the highest dose lost about 21 percent of their body weight on average, or nearly 50 pounds, compared with 4 percent for those on placebo. Among participants who started with a body mass index of 35 or more, the highest dose produced average losses of about 23 percent, or roughly 60 pounds. Blood sugar, measured by the A1C test, fell by up to 1.6 percentage points, against 0.2 points on placebo, and up to about 40 percent of patients reached levels below the threshold used to diagnose prediabetes.

Retatrutide belongs to the same family as semaglutide, sold as Ozempic and Wegovy, and tirzepatide, sold as Mounjaro and Zepbound. Those drugs mimic one or two gut hormones that regulate appetite and blood sugar. Retatrutide acts on three, adding glucagon to the GLP-1 and GIP hormones. In earlier diabetes trials, semaglutide produced weight loss of up to about 10 percent and tirzepatide up to about 15 percent, though the studies were not head-to-head comparisons.

The side effects resembled those of the existing drugs: mainly diarrhea, nausea, constipation and vomiting, which Lilly described as generally mild to moderate. About 8 percent of people on the highest dose stopped treatment because of side effects, compared with about 5 percent on placebo. Nausea was reported by about 28 percent of people on the top dose.

Outside doctors were impressed but cautious. A Duke Health physician who was not involved in the trial told NBC News that the results rival gastric bypass surgery, while another Duke physician said the drug may be too strong for some patients, such as those with mild diabetes or only modestly elevated weight, who might do better on existing medications.

The strongest argument for caution is that these are company-reported results from a trial that lasted under two years, and the long-term effects of losing so much weight with a three-hormone drug are not yet known. Lilly says additional results from its broader program, which has enrolled more than 5,800 people across four registration trials, are due over the next year.

Retatrutide is not approved for sale. Lilly said it plans to apply to the Food and Drug Administration in the first quarter of 2027. Unauthorized copies are already being sold online and through some med spas and compounding pharmacies, often labeled for research use only, and Lilly has sued sellers of unapproved versions.