Novo Nordisk filed a lawsuit against Eli Lilly on July 21, 2026, in U.S. District Court in New Jersey. The lawsuit accuses Lilly of false and misleading advertising and unfair competition related to its obesity drug Zepbound and diabetes treatment Mounjaro [1, 2, 3].

The complaint alleges that Lilly’s ad campaign relies on outdated clinical trials. It claims Lilly compares the highest approved doses of its drugs to lower doses of Novo Nordisk’s Wegovy and Ozempic, without referencing Novo’s newer high-dose versions approved by the FDA in March 2026 [1, 2, 3].

Novo Nordisk’s general counsel John Kuckelman said: "The ads are maliciously and deceptively false because Lilly knowingly cites outdated clinical trials that compare the highest doses of the Lilly medicines to lower doses of Novo Nordisk’s medicines." He added, "That leaves them with the inevitable conclusion that Lilly's medicines are superior to Novo's, and that's not accurate." [1, 2]

Novo says Lilly’s advertising campaign has been served over 700 million times to consumers since its launch [1]. The company seeks a permanent court order to stop Lilly from running the ads and to require corrective advertising. It is prepared to seek a preliminary injunction if Lilly does not comply voluntarily [1, 2, 3].

Since the FDA approved Novo’s higher-dose Wegovy in March 2026, showing average weight loss around 19%, the competition between the two companies in the obesity and diabetes drug market has intensified [2, 3].

Shares of Eli Lilly fell 0.5% in pre-market trading on the day the lawsuit was announced, while Novo Nordisk shares dropped 1.7% in Copenhagen afternoon trading [1]. Lilly had not provided an immediate public comment on the lawsuit as of July 21, 2026 [1, 2, 3].

Prior to the lawsuit, Novo had sent a cease-and-desist letter in April 2026 requesting Lilly remove the allegedly false advertising [1, 2, 3]. The lawsuit follows Lilly’s refusal to comply.

The court will now review the claims, with Novo Nordisk seeking swift action to halt the disputed ads and correct the record in the coming weeks.