Novo Nordisk has filed a lawsuit against Eli Lilly in a U.S. federal court in New Jersey, alleging that the Indianapolis-based drugmaker engaged in false advertising related to its weight-loss and diabetes medications. The Danish pharmaceutical company claims that Eli Lilly’s nationwide marketing campaigns for its obesity drug Zepbound and diabetes treatment Mounjaro used misleading comparisons that violate federal and state laws, including the Lanham Act.
According to the complaint, Eli Lilly’s advertisements highlight data from a clinical trial comparing the highest approved doses of Zepbound and Mounjaro to lower doses of Novo Nordisk’s drugs—Wegovy and Ozempic—while omitting newer, higher-dose formulations from Novo Nordisk that reportedly produce greater weight loss. Novo Nordisk argues this selective use of data creates a deceptive impression that Eli Lilly’s medicines are significantly more effective.
The ads in question promoted findings from a company-sponsored study showing that participants using tirzepatide (marketed as Zepbound) lost an average of 20.2% of their body weight, roughly 50 pounds, compared with 13.7%, about 33 pounds, for those taking semaglutide (marketed as Wegovy). Novo Nordisk contends the ads’ text disclaimer, noting that the higher-dose version of Wegovy was not included in the trial, is insufficient to offset the overall impression conveyed.
Novo Nordisk points to newer late-stage clinical data for the higher Wegovy dose, approved in March, which demonstrated an average weight loss of 19%—approximately 47 pounds—over 72 weeks, narrowing the difference between the two medications. However, there has been no head-to-head trial comparing this updated Wegovy dose with the highest dose of Zepbound.
John Kuckelman, Novo Nordisk’s senior vice president and group general counsel, said the ads could mislead patients into believing Eli Lilly’s drugs are vastly superior, influencing treatment decisions without considering the more current data. In addition to weight loss claims, Novo Nordisk alleges that Eli Lilly made similar misleading comparisons regarding blood-sugar reduction for Mounjaro versus Ozempic, as well as weight loss for its obesity pill.
Eli Lilly defended its advertising, stating the study cited is the most direct scientific evidence currently available. A company spokesperson described the trial as “robustly designed” and insisted on standing behind the ads. The spokesperson criticized Novo Nordisk for seeking legal intervention rather than competing on product merits.
Novo Nordisk has demanded Eli Lilly cease the disputed advertising campaigns. The lawsuit indicates that if Eli Lilly does not comply within two days, Novo Nordisk will pursue a court order to halt the ads and is also seeking financial damages. Eli Lilly has confirmed it will contest the lawsuit. This legal action marks a significant escalation in the ongoing competition between the two companies for dominance in the rapidly expanding weight-loss drug market, currently valued at nearly $80 billion.