Novo Nordisk is taking Eli Lilly to court in the United States, igniting a new front in the competition for the anti-obesity and diabetes drug market. At the center of the lawsuit are advertising campaigns dedicated to Zepbound and Mounjaro, which according to the Danish company spread misleading comparisons about the efficacy of the treatments compared to its Wegovy and Ozempic.
The clash comes at a decisive phase for the GLP-1 sector, which is estimated to exceed $100 billion in value by 2030.
THE LAWSUIT AGAINST ELI LILLY
Novo Nordisk filed the lawsuit in the Federal District Court of New Jersey, accusing Eli Lilly of violating federal and state laws on false advertising and unfair competition, including the Lanham Act. The company claims that the national campaigns dedicated to Zepbound and Mounjaro use outdated clinical data to make Eli Lilly’s products appear overall superior to Wegovy and Ozempic.
Novo Nordisk states that the ads compare the maximum approved doses of Eli Lilly’s drugs with the lower doses of competing medicines, without considering the latest high-dose versions. In the complaint, the company describes the advertisements as “maliciously and deceptively false,” claiming that Eli Lilly “knowingly cites outdated clinical studies” to support its superiority.
THE ISSUE OF CLINICAL STUDIES
The central point of contention concerns the 7.2 milligram Wegovy, approved by the Food and Drug Administration (FDA) last March. According to Novo Nordisk, this version allows an average weight loss of about 19%, approximately 21 kg, a result defined as “clinically consistent” with that observed for Zepbound in the most recent available studies.
Eli Lilly’s campaigns, however, refer to the head-to-head SURMOUNT-5 study, completed in 2024, which compared Zepbound at doses of 10 and 15 milligrams with Wegovy at doses of 1.7 and 2.4 milligrams. In that study, patients treated with Zepbound lost an average of about 22 kg, compared to 15 kg recorded with 2.4 milligram Wegovy. Novo Nordisk asserts that no clinical studies have directly compared the currently available maximum doses of the two drugs, rendering Eli Lilly’s claims of superiority unfounded.
THE ACCUSATIONS ON ADVERTISING
Novo Nordisk also claims that Eli Lilly continued to use the same promotional messages even after the approval of the new Wegovy dose. John Kuckelman, senior vice president and general counsel of the group, stated that the company had sent a cease-and-desist letter last April without receiving a response. According to the executive, Eli Lilly only added “a very small disclaimer,” insufficient to correct the main message.
The Danish company further claims that the ads were broadcast on television, on social networks such as TikTok and Facebook, and during major sporting events, reaching over 700 million views since late April. “People deserve updated and evidence-based information when making decisions about their health,” Novo Nordisk said, adding that the campaign created “widespread confusion” among consumers.
ELI LILLY’S DEFENSE
Eli Lilly completely rejects the accusations and maintains that its communication is based on the best available scientific evidence. “It is truthful, transparent, and based on the strongest direct scientific evidence available, exactly what patients deserve,” a company spokesperson said. The company believes the SURMOUNT-5 study represents “the gold standard” for comparing the drugs and accuses Novo Nordisk of trying to prevent the dissemination of the study’s results instead of competing “on the quality of their products.”
A CHALLENGE WORTH OVER $100 BILLION
The controversy falls within the competition for control of the GLP-1 drug market, which analysts estimate could exceed $100 billion in annual revenue by 2030. After being the first to launch Wegovy, USA Today writes that Novo Nordisk has lost ground to Eli Lilly, whose Zepbound sales reached nearly $4.2 billion in the first quarter of 2026, up 80% from the previous year.
In recent months, both companies have also expanded their offerings with oral formulations of their drugs, further increasing competition in a sector expected to grow thanks to the new Medicare GLP-1 Bridge program in the United States.
THE DEMANDS AND EXPERT ASSESSMENTS
Novo Nordisk is asking the court for a permanent injunction requiring Eli Lilly to withdraw the advertisements from all platforms, launch a corrective advertising campaign, and pay damages, including profits attributable to the contested campaigns. The company also announced that, if the ads are not voluntarily withdrawn, it will seek a preliminary injunction to immediately block their dissemination.
According to Alexandra Roberts, a professor at Northeastern University School of Law, “the damages could be significant” if Novo Nordisk manages to prove the additional profits obtained by Eli Lilly or the losses suffered due to the advertising campaign. However, the professor notes that compensation could be limited by the fact that the 7.2 milligram dose of Wegovy was only approved last March.
More cautious is the judgment of Evan Seigerman, an analyst at BMO Capital, who says disputes between large pharmaceutical companies generally concern patents rather than advertising campaigns. In his view, with this initiative “Novo Nordisk is trying to defend its turf,” although the outcome of the lawsuit could have a limited impact on the two companies, ending up “arguing over marginal details.”
