Patients receiving Eli Lilly’s diabetes medicine Mounjaro were “significantly more likely” to achieve clinically meaningful weight loss compared to those on Novo Nordisk’s Ozempic, according to a new study that could preview the results of a high-stakes, head-to-head trial of the compounds.
The study published Monday comes with significant caveats. It’s observational, meaning it looks backward using patient records instead of pitting the drugs head-to-head in a randomized trial. To try and remove some of the uncertainty inherent in real-world patient data, the researchers reviewed data from more than 40,000 recipients of the two drugs and matched 9,200 people on each drug to compare the reported weight loss effects.
The results showed that Lilly’s drug significantly outperformed Novo’s. At six months, patients receiving tirzepatide on average lost 10.1% of their body weight, compared with a 5.8% drop for patients receiving semaglutide. The gap widened by the one-year mark, with tirzepatide spurring a 15.3% drop in weight compared to a 8.3% reduction for semaglutide. The results were published in JAMA.
Discontinuations were prevalent on both products, however, with more than 50% of patients dropping out of each of the score-matched treatment arms.
There are huge commercial stakes at play in the battle between the companies, and against future entrants in the weight loss space. Lilly’s Mounjaro and Zepbound sold $2.3 billion in the first quarter, while Novo’s Ozempic and Wegovy sold more than 37.2 billion Danish kroner (nearly $5.4 billion).
A spokesperson for Novo Nordisk emphasized that the best way to compare the two treatments would be in a randomized, head-to-head trial. Lilly is running such an experiment, testing the two companies’ drugs in patients who are overweight or obese but without type 2 diabetes. That trial is expected to be completed by early November.
Along with the observational nature of the study, the Novo spokesperson emphasized other caveats, namely that the research assessed off-label use of type 2 diabetes treatments, rather than each company’s branded weight loss equivalents, Wegovy and Zepbound. Novo added that there weren’t adequate dosing data included in the published results.
“While lowering body weight is an important goal of obesity management, it is important to also consider other needs when choosing a treatment,” the company said.
A spokesperson for Lilly declined to comment on the results as the company did not sponsor the study.
Editor’s note: This story was updated to include a response from a Lilly spokesperson.