Novo Nordisk has filed a lawsuit against Eli Lilly, accusing the rival drugmaker of running misleading advertisements for Zepbound and Mounjaro.
The lawsuit was filed July 21 in the U.S. District Court for the District of New Jersey.
Novo Nordisk claims Eli Lilly’s national ads compare the highest doses of Zepbound and Mounjaro against lower doses of Novo’s Wegovy and Ozempic, without including newer, FDA-approved high-dose data. Novo points specifically to Wegovy’s 7.2-milligram dose, approved in March, which showed average weight loss of 19%, or about 47 pounds, in company trials.
The lawsuit also alleges Lilly’s Mounjaro ads omit a higher-dose version of Ozempic that the FDA approved more than four years ago. Novo contends that these ad campaigns violate federal and state false advertising and unfair competition laws.
“As new and more effective treatment options become available, people deserve accurate information that reflects the latest scientific evidence and helps them make informed care decisions,” John Kuckelman, senior vice president and group general counsel of Novo Nordisk, said in a July 21 news release. “Healthcare companies have a responsibility to keep their public claims accurate and current — ineffective, fine-print disclaimers do not fix the misleading impression created by major national campaigns.”
The drugmaker said it sent Lilly a cease-and-desist letter before filing the lawsuit, and that Lilly declined to pull or substantively revise the ads.
A Lilly spokesperson told Becker’s July 21 that the company stands behind its advertising, which cites findings from a clinical trial comparing Zepbound and Wegovy that was published in The New England Journal of Medicine in 2025.
“Rather than compete on the merits of its products, Novo is asking a court to stop Lilly from communicating the results of that trial,” the spokesperson said. “We stand firmly behind our advertising. It is truthful, it is transparent, and it is grounded in the most direct scientific evidence available — exactly what patients deserve. We will continue to focus on the science and defend against this lawsuit vigorously.”
Novo is seeking a permanent injunction barring the ads and ordering Lilly to run a corrective advertising campaign. The company said it will seek a preliminary injunction in the coming days if Lilly does not act voluntarily.
The lawsuit escalates a rivalry between two of the largest players in the GLP-1 weight loss and diabetes drug market, where advertising claims increasingly shape which therapy millions of patients choose.
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