According to Eli Lilly, Zepbound results in more weight loss than Wegovy in the study

People who took Eli Lilly’s weight-loss drug Zepbound lost more pounds in a head-to-head clinical trial than those who took Novo Nordisk’s Wegovy, Lilly said in a news release Wednesday.

The study, funded by Lilly, is the first randomized, controlled clinical trial comparing the two competing weight loss drugs. Previous studies have shown that Zepbound outperforms Wegovy for weight loss. However, these were not considered true comparisons because they were based on looking back at existing data.

According to Lilly’s study results, patients who received weekly Zepbound injections lost an average of 20.2% of their body weight, or 50.3 pounds, after 72 weeks, compared to an average of 13.7% of their body weight, or 33.1 pounds, for those who received Wegovy received.

This means, says Lilly, that Zepbound provides 47% more weight loss than Wegovy.

Dr. Susan Spratt, an endocrinologist and chief medical director of the Population Health Management Office at Duke Health in North Carolina, said that while Zepbound resulted in more weight loss than Wegovy, both drugs were highly effective.

“The amount of weight loss with both is amazing,” Spratt said.

Wednesday’s results were announced in a press release and were not yet available for peer review. Lilly plans to present the results at a medical meeting next year.

Novo Nordisk did not immediately respond to a request for comment.

The results were based on 751 adults in the U.S., including Puerto Rico, who were randomly assigned to receive one of the two highest doses of Zepbound or Wegovy. People were either overweight or suffering from obesity.

Eli Lilly said the most commonly reported side effects of Zepound and Wegovy were gastrointestinal side effects and were “generally mild to moderate in severity.”

Dr. Christopher McGowan, a gastroenterologist who runs a weight-loss clinic in North Carolina, said the side effects of Zepbound and Wegovy are generally comparable, although his patients tend to say they feel better with Zepbound.

Side effects of the medication may include gastrointestinal problems such as abdominal pain, nausea, and vomiting.

Zepbound contains the active ingredient tirzepatide, the same active ingredient used in Lilly’s diabetes drug Mounjaro. Wegovy contains semaglutide, the active ingredient that is also contained in Novo Nordisk’s diabetes drug Ozempic.

Both work in a similar way: The GLP-1 drugs mimic a hormone that helps reduce food intake and appetite.

However, tirzepatide also mimics a second hormone called GIP, which is thought to not only reduce appetite but also improve the way the body breaks down sugar and fat.

Spratt said she would like to see more data comparing the drugs to health outcomes beyond weight loss.

Wegovy, for example, has been proven to reduce the risk of heart disease in people who are overweight or obese. Zepbound has been shown to be a possible treatment for obstructive sleep apnea.

“I don’t think that was the goal of this study, but it will be important which drug we recommend,” Spratt said.

McGowan said weight loss isn’t the only factor patients consider.

“Most patients who want to receive GLP-1 treatment choose whatever treatment is available to them based on cost, availability and insurance coverage,” he said. “Right now, very few patients can be picky.”