Novo Nordisk is escalating its legal battle against Eli Lilly over its GLP-1 drug marketing, notifying a federal court that it plans to seek a preliminary injunction that would stop its obesity rival from running certain ads while the case proceeds.
Days after filing a lawsuit in New Jersey accusing Lilly of using “deliberately false” messages to compare the companies’ drugs, the Danish drugmaker notified the court that it plans to file a motion for a preliminary injunction Aug. 17. Novo says it will seek an order that would bar Lilly from disseminating allegedly “false and misleading” direct-to-consumer ads for its GLP-1 weight loss and diabetes drugs.
Novo contends that Lilly’s advertising campaigns are “deceiving millions of Americans” by claiming its products are more effective than Novo’s. The two promotions at issue claim that Lilly’s obesity drug Zepbound produces “significantly more” weight loss than Novo’s Wegovy and that the diabetes drug Mounjaro reduces A1C “significantly more” than Novo’s Ozempic.
Each statement, according to Novo, “knowingly uses outdated clinical trials” to claim superior efficacy because the studies were conducted before Novo introduced higher-dose versions of its products, which the company describes as the “most effective” doses.
The trials in question are Surmount-5 and Surpass-2. The first was a study that pitted Zepbound at doses of 10 mg and 15 mg against Wegovy at doses of 1.7 mg and 2.4 mg. A higher, 7.2-mg dose of Wegovy was approved in March 2026, rendering Surmount-5 “outdated,” Novo said in its filing.
The second trial, Surpass-2, compared Mounjaro’s highest dose of 15 mg with a 1-mg dose of Ozempic. The study was conducted in 2021, a year before the FDA cleared a 2-mg dose of Ozempic.
Novo claims it is suffering “obvious and irreparable” harm from Lilly’s use of the trial data in its marketing. The Zepbound campaign, which refers to Surmount-5 as a “head-to-head” comparison, has recently expanded to social media and generated about 700 million impressions since April 2026, Novo said.
Citing consumer survey evidence, Novo said more than 30% of people who saw the Zepbound ad came away with the message that Zepbound produces significantly more weight loss than Wegovy. The company cited similar findings from a survey involving the Mounjaro ad.
“Every day Lilly’s campaigns run, they divert patients to Zepbound and Mounjaro, entrench false impressions of Wegovy’s and Ozempic’s inferiority, and erode goodwill Novo Nordisk has spent decades building,” Novo said in court papers. “Money damages cannot undo that harm.”
Lilly continues to stand “behind the science and our advertising” and will “oppose this motion vigorously,” a spokesperson told Fierce Pharma in an email.
“Head-to-head clinical trials are the strongest evidence for comparing medicines. SURMOUNT-5 and SURPASS-2 are the only head-to-head, randomized clinical trials directly comparing tirzepatide and semaglutide — and Novo Nordisk wants to stop Lilly from sharing their results,” the spokesperson added. “Novo Nordisk has never tested its highest doses of semaglutide against Lilly's tirzepatide medicines in any clinical trial; instead, it is using a lawsuit to advance comparisons it has never put to the test.”
The preliminary injunction Novo plans to seek would apply only to Lilly ads that make the disputed comparative claims. Novo said it sent Lilly a cease-and-desist letter in April demanding that the company withdraw the ads. Lilly refused, leaving Novo with “no choice but to seek judicial relief,” according to the filing.
Lilly did add a disclosure in small print to its Zepbound ad noting that a higher dose of Wegovy has “since been approved.” Still, Novo maintains that the promotions amount to false advertising and could influence consumers’ perceptions of the competing drugs.
“We welcome competition grounded in honest, up-to-date science, but we cannot stand by as advertising continues to withhold the information patients need and deserve when making decisions about their health," Novo’s general counsel John F. Kuckelman said in an emailed statement.
"Millions of Americans living with obesity and type 2 diabetes rely on these medicines. Misleading advertisements that selectively compare lower doses of Novo Nordisk's medicines against higher doses of Lilly’s medicines, based on outdated studies, leave patients with the mistaken impression that Lilly's drugs are vastly superior, and that is simply not true," Kuckelman continued.
Novo’s planned motion opens a new front in the companies’ long-running battle for dominance of the GLP-1 drug market. Despite Novo’s first-to-market advantage, Lilly has caught up and overtaken its rival, with Mounjaro sales reaching $8.7 billion in the first quarter, compared with 27.8 billion Danish kroner, or about $4.2 billion, for Ozempic.
Zepbound also outsold Wegovy during the period. In the second quarter, Zepbound ranked fourth among brands in estimated national linear television ad spending, at $67.8 million, according to iSpot data.