Novo Nordisk filed a false advertising lawsuit against Eli Lilly on July 21, 2026, alleging that Lilly's ads for Zepbound and Mounjaro unfairly compare highest doses of its drugs to lower doses of Novo's Wegovy and Ozempic. Lilly defends the ads as based on its SURMOUNT-5 trial results.
Novo Nordisk took legal action against rival Eli Lilly on Tuesday, July 21, 2026, filing a lawsuit in federal court that accuses the U.S. drugmaker of false advertising in marketing its weight-loss medications. The Danish company claims that Lilly's promotional campaigns mislead consumers by selectively comparing doses.
Novo Nordisk submitted its complaint in the U.S. District Court in New Jersey, alleging violations of both federal and state false advertising and unfair competition laws, including the Lanham Act. The lawsuit targets Lilly's nationwide advertising campaigns for the obesity drug Zepbound and the diabetes treatment Mounjaro.
According to Novo, Lilly's advertisements compare the highest approved doses of its own medicines with lower doses of Novo's Wegovy and Ozempic. Novo argues that Lilly intentionally omitted newer, higher-dose versions of Wegovy that the Danish company says deliver greater weight loss. Specifically, the U.S. Food and Drug Administration approved a 7.2 milligram dose of Wegovy in March of this year, a version that Novo claims outperforms the lower doses used in Lilly's comparisons.
Novo wrote in its complaint: “The ads are maliciously and deceptively false because Lilly knowingly cites outdated clinical trials that compare the highest doses of the Lilly medicines to lower doses of Novo Nordisk’s medicines.”
Indianapolis-based Eli Lilly pushed back against the allegations, stating it stands firmly behind its advertising. The company said its ads rely on results from the SURMOUNT-5 trial, which was completed in 2024. That trial compared patients taking 10 or 15 milligrams of Lilly's Zepbound to patients taking 1.7 or 2.4 milligram doses of Wegovy.
A Lilly spokesperson issued a statement defending the campaign: “Rather than compete on the merits of its products, Novo is asking a court to stop Lilly from communicating the results of that trial. We will continue to focus on the science and defend against this lawsuit vigorously.”
Novo and Lilly are locked in an intense battle for dominance in the U.S. obesity drug market, which analysts project will be worth more than $100 billion by 2030. The United States is one of only a handful of countries that permit pharmaceutical companies to advertise prescription medicines directly to consumers, and drugmakers spend billions of dollars annually on television and other advertising.
Novo Nordisk was first to market with its weight-loss injection Wegovy but later lost the lead to Lilly’s Zepbound. After replacing its CEO and issuing multiple profit warnings last year, Novo has landed a counterpunch with an oral version of Wegovy, which has maintained strong demand despite the launch of Lilly’s competing pill.
Pharmaceutical companies frequently sue each other over patent infringement claims, but false advertising lawsuits are less common. In this case, Novo is also seeking damages, including Lilly’s profits that can be attributed to the allegedly deceptive ads.
The financial impact was visible on the stock market. Copenhagen-listed Novo Nordisk shares dropped 2% in afternoon trading, while Lilly shares rose marginally, up 0.5%.
Novo contends that the scale of Lilly’s campaign is massive. According to the complaint, the ad campaign has been served to consumers more than 700 million times since Lilly modified its advertisements after receiving a letter from Novo in late April.
Peptides referenced: Semaglutide, Tirzepatide.
Related reading: Novo Nordisk Sues Eli Lilly Over 'Misleading' GLP-1 Drug Ads, Novo Nordisk sues Lilly over misleading GLP-1 advertising campaigns, Novo Nordisk sues Eli Lilly over ads in GLP-1 market, Wegovy Maker Files Suit Against Eli Lilly Over False GLP-1 Ads.