Novo Nordisk Sues Eli Lilly, Alleging False Advertising for Weight-Loss Drugs

Novo Nordisk announced Tuesday it has filed a lawsuit against rival Eli Lilly in a U.S. federal court, accusing the American pharmaceutical giant of false advertising in the fiercely competitive weight-loss drug market. The suit alleges that Lilly's marketing campaigns for its popular treatments create a misleading impression of superior efficacy compared to Novo's products.

The Core Allegations

The lawsuit, filed in the U.S. District Court in New Jersey, claims that Eli Lilly has violated federal and state false advertising and unfair competition laws, including the Lanham Act. Novo Nordisk contends that nationwide advertising for Lilly's obesity drug Zepbound and diabetes treatment Mounjaro unfairly compares the highest approved doses of those medicines with lower, less effective doses of its own drugs, Wegovy and Ozempic.

According to Novo Nordisk, the ads omit newer, higher-dose versions of its treatments that it says deliver greater weight loss, thereby skewing the comparison. John Kuckelman, Novo's general counsel, told Reuters the company sent a cease-and-desist letter to Lilly in April, which went unanswered.

A Dispute Over Data

The central issue is the data used in Lilly's promotional materials. Novo Nordisk highlights a specific discrepancy in the advertised weight-loss figures:

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• Lilly's ads compare weight loss of about 50 pounds for Zepbound with about 33 pounds for Wegovy, according to the lawsuit.
• Novo Nordisk argues that separate late-stage trials of the highest approved doses of both drugs show much more comparable results: average weight loss of about 48 pounds for Zepbound and 47 pounds for Wegovy.

Kuckelman noted that no head-to-head clinical trial has directly compared the highest approved doses of the two medicines.

Legal Action and Market Context

Novo Nordisk is seeking a court order that would require Eli Lilly to withdraw the advertisements and fund a corrective advertising campaign. The company also stated it intends to seek a preliminary injunction if Lilly does not voluntarily remove the ads.

The legal battle underscores the intense rivalry between the two dominant players in the rapidly growing global market for GLP-1 agonist drugs. The success of these treatments for obesity and diabetes has propelled both companies to become two of the most valuable in the world, and market share is aggressively contested through both research and marketing.