GLP-1 Fight: Novo Sues Eli Lilly Over Nationwide “Deceptive Advertising” Campaign

Novo Nordisk wrote in a press release that it is suing GLP-1 rival Eli Lilly in federal court in New Jersey, alleging nationwide “deceptive advertising” for Zepbound and Mounjaro. The company claims Lilly misleads consumers by comparing Lilly’s highest doses with lower doses of Novo’s Wegovy and Ozempic.

Novo claims Lilly’s Zepbound advertising campaign relies on outdated studies that exclude the 7.2-milligram dose of Wegovy, approved in March 2026, which produced an average weight loss of about 19%. Novo also stated that there has been no head-to-head trial comparing the highest approved doses of the two drugs.

“A lawsuit, filed today in federal court, challenges a nationwide pattern of deceptive advertising which confuses consumers by using outdated studies to compare the highest injectable doses of Lilly’s medicines against lower doses of Novo Nordisk’s injectable medicines for obesity and type 2 diabetes,” Novo wrote in the release.

What Novo seeks:

Through this action, Novo Nordisk is seeking a permanent injunction requiring Lilly to pull its misleading comparative advertising across all platforms and to conduct a corrective advertising campaign. We have also communicated to Lilly that if they do not voluntarily pull these ads, Novo Nordisk intends to file a formal motion with the Court in the coming days seeking a preliminary injunction to immediately block them, with evidence that consumers are being confused and misled by Lilly’s ads.

The lawsuit comes as Novo and Lilly battle for share of a global GLP-1 market projected to exceed $120 billion by 2030, according to Bloomberg Intelligence. Novo entered the obesity market first with Wegovy, but Lilly has since overtaken its rival with Zepbound and now leads in sales.

The divergence is reflected in their share prices: Novo’s stock is flat this year and trading at lows last seen in 2021, while Lilly is at record highs.

Novo is pursuing a turnaround under its new CEO, expanding partnerships with telehealth companies and rolling out a new oral weight-loss drug. Will that be enough to reverse the stock?