Eli Lilly is claiming another victory in a head-to-head trial comparing its weight-loss drug Zepbound to its main rival Wegovy from Novo Nordisk.
The full data from the 751-subject SURMOUNT-5 trial was published in the New England Journal of Medicine at the weekend and simultaneously presented at the European Congress on Obesity (ECO), building on top-line data reported last December.
In the results, dual GLP-1/GIP agonist Zepbound (tirzepatide) outperformed GLP-1 agonist Wegovy (semaglutide) on all weight-loss endpoints at 72 weeks among patients with obesity or who were overweight with at least one comorbidity, such as high blood pressure, elevated cholesterol, obstructive sleep apnoea, or cardiovascular disease, but without diabetes. They were asked to take the highest dose of the drugs they were able to tolerate.
The main result – reported earlier – was an overall weight reduction of 20.2% with Zepbound at 72 weeks, compared to 13.7% with Wegovy.
Now, Lilly has reinforced that finding with a strong of other measures, including that 32% of people taking Zepbound were able to lose a quarter of their body weight compared to 16% of the Wegovy group, while they also saw a greater reduction in waist circumference at 18.4cm compared to 13.0cm.
A larger waist circumference is associated with a higher risk of all-cause mortality and decreased life expectancy. Meanwhile, the group taking Zepbound (sold as Mounjaro for weight loss in some markets) also saw greater improvements in blood pressure, blood glucose, and cholesterol levels.
“These data confirm Zepbound as a leading treatment option for people living with obesity and equip healthcare providers with critical insights to make well-informed treatment decisions as part of a comprehensive obesity care plan,” said Leonard Glass, Lilly’s head of medical affairs.
The results of SURMOUNT-5 will be ammunition in a war for supremacy in the weight-loss category, which is currently dominated by the two once-weekly injectable drugs, which made $2.31 billion and $2.64 billion, respectively, in the first three months of 2025.
Lilly’s drug grew more than fourfold compared to the same period of 2024, however, while Wegovy fell 13%, a decline which has been attributed to competition as well as widespread compounding of the drug in the US, which has come to an end after it was removed from the FDA’s shortages list.
Both Lilly and Novo Nordisk rely on direct out-of-pocket sales of the medicines to drive growth, and Novo Nordisk recently ramped up its position in the US market with a string of supply agreements with major telehealth companies.
Meanwhile, the Danish drugmaker was also lifted by a decision by pharmacy benefit manager (PBM) CVS Health to remove Zepbound but retain Wegovy on its formulary of reimbursed medicines.
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