Novo Nordisk (NVO) fell around 1.4% and Eli Lilly (LLY) dropped around 2.7% on Tuesday after Novo filed a lawsuit accusing Lilly of running misleading ads for its weight-loss drugs.
The suit was filed in the U.S. District Court for the District of New Jersey. Novo claims Lilly violated the Lanham Act, along with federal and state false advertising and unfair competition laws.
At the center of the case are nationwide TV and social media campaigns for Lilly’s obesity drug Zepbound and diabetes treatment Mounjaro.
Novo Nordisk $NVO just filed a lawsuit against Eli Lilly $LLY
Novo alleges that Eli Lilly's ads for its weight loss drugs are designed to "mislead consumers about their superior efficacy" relative to Novo Nordisk's injections – CNBC pic.twitter.com/mmgEU20L3B
— Evan (@StockMKTNewz) July 21, 2026
Novo says those ads use outdated clinical data to make Lilly’s drugs look better. One TV commercial, which has racked up over 700 million impressions since late April, tells viewers that patients on Zepbound lose 50 pounds on average versus 33 pounds on Wegovy.
The problem, according to Novo, is that the 33-pound figure comes from trials using lower doses of Wegovy — not the newer 7.2-milligram dose approved in March 2025.
Novo says its high-dose Wegovy showed average weight loss of around 47 pounds in recent trials. That’s close to Zepbound’s 48-pound figure from Lilly’s own most recent data.
“It leaves them with the inevitable conclusion that Lilly’s medicines are superior to Novo’s, and that’s not accurate,” said John Kuckelman, Novo’s group general counsel.
Novo says this isn’t new territory. The company sent Lilly a formal cease-and-desist letter back in April, shortly after the high-dose Wegovy approval.
Lilly did not pull the ads. Instead, Novo says, the company added what it called an “ambiguous, confusing, virtually illegible” footnote acknowledging the higher dose existed — but not making clear it was more effective.
Novo is now asking the court to permanently block the ads, force Lilly to run corrective advertising, and pay financial damages. If Lilly doesn’t voluntarily remove the ads, Novo says it will seek a preliminary injunction to pull them immediately while the case plays out.
Lilly did not respond to requests for comment.
The lawsuit doesn’t stop at Zepbound and Wegovy. Novo also alleges Lilly used the same tactic when comparing Mounjaro and Ozempic — withholding data on a higher dose of Ozempic that was approved over four years ago.
No head-to-head trials have compared the highest approved doses of Wegovy and Zepbound. Novo says that means Lilly has “no basis” to claim its drugs are more effective than Novo’s current lineup.
“While it may have been accurate to say that before 7.2 milligrams became available for Wegovy, it is no longer accurate to say that,” Kuckelman said.
The Zepbound TV commercial alone has been viewed over 700 million times since it started airing around the end of April.
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