Novo Nordisk sues Eli Lilly, citing 19% weight loss data in ad dispute

Novo Nordisk sued Eli Lilly on Monday, alleging its GLP-1 drug ads omit data showing Wegovy's higher-dose efficacy of 19% weight loss.

"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," John F. Kuckelman, senior vice president and group general counsel at Novo Nordisk, said in a statement.

The lawsuit, filed in the US District Court for the District of New Jersey, claims Lilly's direct-to-consumer advertising for Zepbound and Mounjaro (tirzepatide) intentionally selected outdated studies comparing Lilly's highest doses against lower doses of Novo Nordisk's medicines. Novo Nordisk alleges the ads deceptively present those results as proof of broad, product-level superiority while burying or omitting critical clinical context. The company is seeking a permanent injunction requiring Lilly to pull the ads and conduct a corrective advertising campaign.

The legal battle escalates an already fierce rivalry in the $100 billion-plus GLP-1 market. Novo Nordisk's STEP UP trial showed Wegovy 7.2 mg produced mean weight loss of about 19%, or roughly 47 pounds, at 72 weeks, compared with 3.9% for placebo. Lilly's Zepbound, approved for obesity, generated average weight loss of about 22.5% at its highest dose in a separate trial. The dispute centers on how those figures are presented to consumers.

The lawsuit follows a broader crackdown on GLP-1 marketing and distribution. Nearly four times as many Americans are taking a GLP-1 drug compared with two years ago, according to a Gallup survey, while about 20% still use non-FDA-approved compounded versions. The FDA in May proposed excluding semaglutide, tirzepatide and liraglutide from the 503B Bulks List, a move that could curb large-scale compounding. Novo Nordisk previously sued telehealth company Hims & Hers over compounded alternatives, a case that ended with the company agreeing to offer Wegovy through its platform.

Novo Nordisk said it intends to file a motion for a preliminary injunction to immediately block the ads, with evidence that consumers are being confused and misled. The court will next consider Novo Nordisk's request for a temporary restraining order. A hearing date has not yet been set.

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