Novo Nordisk sues Eli Lilly over weight-loss drug advertising claims

Novo Nordisk has filed a lawsuit against Eli Lilly LLY in a US federal court, accusing its rival of running false and misleading advertising campaigns for its blockbuster diabetes and weight-loss drugs.

The lawsuit, filed Tuesday in the US District Court for the District of New Jersey, alleges that Eli Lilly and Lilly USA violated federal and state false advertising and unfair competition laws, including the Lanham Act.

According to Novo Nordisk, Lilly's nationwide direct-to-consumer advertising for Zepbound and Mounjaro misleads consumers by comparing Lilly's products with lower-dose versions of Novo's Wegovy and Ozempic while excluding information about higher-dose formulations that have since become available.

Novo alleges misleading efficacy claims

Novo Nordisk alleged that Lilly's advertising campaign falsely creates the impression that Zepbound is more effective than Wegovy for weight loss and that Mounjaro lowers blood sugar more effectively than Ozempic.

According to the complaint, Lilly's advertisements rely on outdated clinical trials that compare the highest doses of Zepbound with lower doses of Wegovy rather than the latest FDA-approved formulation.

Novo said the advertisements do not include its 7.2 mg injectable Wegovy dose, which the US Food and Drug Administration approved in March 2026 and which, according to the company, demonstrated an average body weight reduction of approximately 19%, or about 47 pounds.

The company also argued that no head-to-head clinical trial has compared the highest approved doses of Zepbound and Wegovy, making Lilly's broader product superiority claims misleading.

Regarding diabetes treatments, Novo alleged that Lilly compares the highest approved dose of Mounjaro, 15 mg, with Ozempic's 1 mg dose despite the FDA approving a 2 mg maintenance dose of Ozempic more than four years ago.

Novo said the advertising campaigns have appeared during widely viewed sporting broadcasts and on social media platforms including TikTok and Facebook, contributing to what it described as widespread consumer confusion.

Company seeks injunction and corrective advertising

Novo Nordisk said it is seeking a permanent injunction requiring Lilly to discontinue the advertisements across all platforms and conduct a corrective advertising campaign.

The company is also seeking damages, including "any and all of defendants' profits" that it alleges were generated through the advertising.

According to Novo, the legal action follows Lilly's refusal to withdraw or substantially revise the advertisements despite receiving a formal cease-and-desist request.

Novo also said it has informed Lilly that it intends to seek a preliminary injunction in the coming days if the company does not voluntarily remove the advertisements, arguing that consumers are being confused and misled.

“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 F. Kuckelman, senior vice president and Group General Counsel at Novo Nordisk, said in a statement.

“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,” Kuckelman added.

Lawsuit comes as obesity drug competition intensifies

The legal dispute marks the latest confrontation between Novo Nordisk and Eli Lilly, the two companies with approved products in the rapidly expanding obesity drug market.

Lilly currently leads Novo across the combined diabetes and obesity treatment markets.

However, Novo has gained ground with its oral Wegovy weight-loss pill, which launched in the United States in January before Lilly introduced its own oral treatment in April.