Novo Nordisk sues Eli Lilly in high-stakes GLP-1 advertising feud

Investing.com -- The clash between pharma titans Novo Nordisk and Eli Lilly just escalated from the pharmacy counter to the courtroom.

Novo Nordisk Inc. filed a lawsuit in the U.S. District Court for the District of New Jersey against Eli Lilly and Company and Lilly USA, LLC, alleging multiple violations of federal and state false advertising and unfair competition laws under the Lanham Act.

The lawsuit takes aim at Lilly’s aggressive direct-to-consumer (DTC) advertising campaigns for its blockbuster tirzepatide drugs, Zepbound and Mounjaro. Novo Nordisk claims the ads are false and misleading because they intentionally omit data regarding the most potent injectable doses of its own semaglutide drugs, Wegovy and Ozempic.

The legal action follows an unsuccessful attempt to resolve the issue out of court. According to Novo Nordisk’s legal team, the company sent a formal cease-and-desist letter in April. Rather than pulling the ads, Lilly added what Novo calls an inadequate "very small" disclaimer.

Lilly Has Yet to Respond: Eli Lilly has not yet filed a formal defense in court or issued a public statement regarding the lawsuit.

According to Novo Nordisk’s complaint, Lilly’s marketing blitz relies on outdated clinical studies that pit Lilly’s maximum doses against lower doses of Novo Nordisk’s treatments:

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  Zepbound vs. Wegovy: The campaign compares Zepbound’s highest dose (10/15 mg) against Wegovy’s lower 1.7/2.4 mg doses. Crucially, the ads omit the FDA-approved 7.2 mg highest dose of injectable Wegovy (approved in March 2026), which demonstrated an average 19% body weight reduction (~47 lbs) in clinical trials.

  
  


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  Mounjaro vs. Ozempic: Mounjaro’s ads compare its maximum 15 mg dose against a 1 mg dose of Ozempic, completely ignoring the higher 2 mg maintenance dose of Ozempic approved by the FDA over four years ago.

  
  

"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," said John F. Kuckelman, Senior Vice President and Group General Counsel at Novo Nordisk.

Novo Nordisk notes that no head-to-head clinical trial currently exists comparing the maximum doses of these competing weight-loss and diabetes drugs. Despite this, Lilly’s ad campaign has blanketed high-visibility platforms, airing during global sporting events and running heavily across TikTok and Facebook.

Novo Nordisk is demanding:

1. 
   

   A permanent injunction forcing Lilly to pull all comparative ads across all media platforms.

   
   


2. 
   

   Disgorgement of profits and a corrective advertising campaign to address pre-existing consumer impressions.

   
   


3. 
   

   A preliminary injunction to immediately freeze the ad blitz while the lawsuit proceeds, should Lilly refuse to pull them voluntarily.

   
   

This legal showdown reflects the astronomical stakes of the global obesity and diabetes market—a sector projected to surpass $100 billion by 2030. Eli Lilly’s tirzepatide (Zepbound/Mounjaro) and Novo Nordisk’s semaglutide (Wegovy/Ozempic) effectively control the GLP-1 landscape. With supply bottlenecks easing, market share is now being fought on the battleground of brand perception and clinical efficacy messaging.

Direct-to-consumer pharmaceutical advertising is heavily regulated in the U.S. By taking the fight to social media platforms like TikTok, both companies are competing directly for consumer mindshare before patients ever sit down with a prescribing doctor.

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