By Maggie Fick and Michael Erman
LONDON, July 21 (Reuters) - Novo Nordisk sued rival Eli Lilly in a U.S. federal court on Tuesday, accusing the U.S. drugmaker of false advertising in claiming its weight-loss medicines outperform Novo's drugs.
The Danish company filed the lawsuit in U.S. District Court in New Jersey, alleging Lilly violated federal and state false advertising and unfair competition laws, including the Lanham Act, through nationwide advertising campaigns for obesity drug Zepbound and diabetes
treatment Mounjaro.
Novo alleges Lilly compared the highest approved doses of its medicines with lower doses of Novo's Wegovy and Ozempic while omitting newer, higher-dose versions that Novo says deliver greater weight loss.
"The ads are maliciously and deceptively false because Lilly knowingly cites outdated clinical trials that compare the highest doses of the Lilly medicines to lower doses of Novo Nordisk’s medicines," Novo wrote in its complaint.
But Indianapolis-based Eli Lilly said it stands firmly behind its ads, which are based on the results of its SURMOUNT-5 trial. That trial — completed in 2024 — compared patients on 10 mg or 15 mg of Lilly's Zepbound to patients on 1.7 mg or 2.4 mg doses of Wegovy. The FDA approved a 7.2 mg dose of Wegovy in March of this year.
"Rather than compete on the merits of its products, Novo is asking a court to stop Lilly from communicating the results of that trial," a Lilly spokesperson said in a statement. "We will continue to focus on the science and defend against this lawsuit vigorously."
Novo and Lilly are locked in a fierce battle for dominance in the U.S. obesity drug market, which analysts expect to be worth more than $100 billion by 2030.
The U.S. is one of only a handful of countries that allow pharmaceutical companies to advertise prescription medicines directly to consumers. Drugmakers spend billions of dollars every year on television and other advertising.
Novo was first to market with weight-loss injection Wegovy, but later lost the lead to Lilly's rival Zepbound. After replacing its CEO and issuing multiple profit warnings last year, Novo has landed a counterpunch with oral Wegovy, whose strong demand has held up despite the launch of Lilly's competing pill.
Novo said it is seeking a court order requiring Lilly to withdraw the advertisements and run a corrective advertising campaign. It added that it plans to seek a preliminary injunction if Lilly does not voluntarily remove the ads.
Pharmaceutical companies regularly sue each other over patent infringement claims. False advertising suits are less common.
Novo is also seeking damages, including Lilly's profits that can be attributed to the ads.
"Damages could be significant given the size of the market for these drugs if Novo can prove Lilly’s additional profits or its own lost profits tied to the deceptive ad campaign," Professor Alexandra Roberts of Northeastern University's School of Law said in an email. "But given the short time since approval of the higher dose of Wegovy in March 2026, damages may be limited by the duration that the deceptive claims were circulating," she said.
Copenhagen-listed Novo Nordisk shares dropped 2% in afternoon trading, while Lilly shares rose marginally, up 0.5%.
'INADEQUATE DISCLAIMER' IN ADS
Novo said it sent Lilly a cease-and-desist letter in April after the U.S. approved a 7.2-milligram dose of Wegovy. Lilly did not respond to the letter, Novo's general counsel John Kuckelman told Reuters, adding that the company instead inserted what he described as an inadequate disclaimer into the advertisements.
Novo says the scale of Lilly's campaign is massive. The ad campaign has been served up to consumers more than 700 million times just since Lilly modified its ad after Novo's letter in late April.
Kuckelman said Lilly's advertisements compare weight-loss results of about 50 pounds for Zepbound with about 33 pounds for Wegovy, even though no head-to-head trial has compared the highest approved doses of the medicines. He said separate late-stage trials of the highest doses showed average weight loss of about 48 pounds for Zepbound and 47 pounds for Wegovy.
(Reporting by Maggie Fick and Michael Erman; Additional reporting by Blake Brittain, Jonathan Stempel and Christy Santhosh; Editing by Caroline Humer, Nia Williams, Susan Fenton and Mark Porter)
