By Dominic Chopping

Eli Lilly said its Zepbound obesity drug helped patients reduce their waist size by an extra two inches compared to those on Novo Nordisk's Wegovy in a head-to-head study of the two drugs.

Zepbound achieved an average weight reduction of 20.2% compared to 13.7% with Wegovy after 72 weeks, it said.

The study, announced late Sunday and published in The New England Journal of Medicine, was funded by Lilly.

Although patients using both drugs demonstrated significant weight-loss, researchers in the study said it might be the slight variations in how the two drugs work that explains the difference in effectiveness.

Novo Nordisk's Wegovy works by mimicking a gut hormone to control blood sugar and suppress appetite, while Lilly's Zepbound takes a dual-target approach by also mimicking a second gut hormone that is believed to enhance the treatment's effectiveness.

Lilly's study showed that more patients treated with Zepbound had reductions in body weight of at least 10%, 15%, 20%, and 25% than those treated with Wegovy, while they also achieved a greater average waist circumference reduction of 7.2 inches versus the 5.1 inches achieved by those on Wegovy.

The reduction in waist size is a metric watched by physicians as it is thought that abdominal fat can lead to a higher risk of life threatening diseases.

Around 750 obese patients, with an average weight of 113 kilograms and without diabetes took part in the study. They were asked to take the highest dose they could tolerate of one of the two drugs.

Novo Nordisk said the results of the study aren't consistent with what it has seen in its own studies and in real world evidence studies of Wegovy.

"We have clear and consistent evidence of a 17% weight loss and about a third of people losing 20% or more," it said in a statement. "We are unclear about how their methodology would show less weight loss than what is in our approved labels."

The Danish company also said that the Lilly trial evaluated 10 milligram or 15 milligram doses of Zepbound compared to 1.7 milligram or 2.4 milligram doses of Wegovy.

Write to Dominic Chopping at dominic.chopping@wsj.com

(END) Dow Jones Newswires

May 12, 2025 09:02 ET (13:02 GMT)

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