Novo Nordisk, maker of Ozempic, has filed a lawsuit against US rival Eli Lilly, accusing it of running "false and materially misleading" adverts for its competing weight-loss and diabetes drugs. The Danish pharmaceutical giant alleges that Lilly used outdated and selectively chosen trial data to make its products, Zepbound and Mounjaro, appear superior, in a dispute that highlights the increasingly fierce and lucrative rivalry between the two firms in the booming GLP-1 weight-loss drug market.

Novo Nordisk claims Lilly compared its own highest drug doses against lower doses of Novo's medicines, then presented the results as proof of overall superiority while omitting important clinical context. The complaint centres on adverts shown during major sporting broadcasts and on TikTok and Facebook, which Novo says caused "widespread confusion". Eli Lilly has rejected the accusations, standing by its campaign and pointing to its Surmount-5 trial as the only direct head-to-head study comparing the two companies' drug molecules, tirzepatide and semaglutide.