Eli Lilly's obesity drug Zepbound performed significantly better in a head-to-head study than competitor Wegovy from Novo Nordisk. After 72 weeks, patients using Zepbound achieved an average weight reduction of 20.2 percent, while Wegovy only achieved 13.7 percent. The study, funded by Lilly, was published Sunday evening in the New England Journal of Medicine.

Notable is not only the difference in body weight, but also in waist circumference.

Nearly 750 obese individuals without diabetes, with an average starting weight of 113 kilograms, participated in the study. They received the highest dose of medication they could tolerate: 10 mg or 15 mg of Zepbound compared to 1.7 mg or 2.4 mg of Wegovy.

Zepbound follows a dual mode of action: It mimics both the GLP-1 and GIP hormones, while Wegovy relies only on GLP-1. The dual mechanism appears to provide an explanation for the higher efficacy, according to study authors.

Zepbound also consistently performed better in terms of weight loss thresholds: More patients achieved weight losses of 10%, 15%, 20%, or even 25%.

Novo Nordisk reacted cautiously to the results. The Danish company pointed to differing data from its own studies and real-world evidence, emphasizing that one-third of Wegovy users lose 20% or more of their weight. Additionally, the company criticized the methodology of the Lilly study, particularly the dosage differences.

The direct confrontation of two blockbuster drugs is rare – and all the more significant in a billion-dollar market marked by chronic diseases. The numbers currently favor Lilly.