Novo Nordisk alleges their rival's advertising campaigns for its drugs are designed to mislead consumers about their superior efficacy
Novo Nordisk has filed a federal lawsuit against Eli Lilly, alleging that Lilly's direct-to-consumer advertising campaigns for its obesity and diabetes drugs mislead patients by relying on outdated clinical trial data to exaggerate the efficacy gap between the two companies' GLP-1 medications.
The complaint, filed July 21 in the U.S. District Court for the District of New Jersey, brings federal and state claims under the Lanham Act and unfair competition statutes. It targets nationwide TV and social media campaigns for Lilly's Zepbound and Mounjaro that Novo alleges cherry-pick dosage comparisons to make Lilly's drugs appear categorically superior to Wegovy and Ozempic, a framing the Danish drugmaker says no longer reflects current evidence.
That “leaves them with the inevitable conclusion that Lilly’s medicines are superior to Novo’s, and that’s not accurate,” said John Kuckelman, Novo’s group general counsel, in an interview Monday with CNBC.
Dosage comparisons at the heart of the dispute
At issue is how Lilly's ads present data from SURMOUNT-5, a phase 3b head-to-head trial published in The New England Journal of Medicine in May 2025. That study compared maximum doses of Zepbound (tirzepatide) to the 1.7-milligram and 2.4-milligram doses of Wegovy (semaglutide), finding Zepbound delivered 20.2 per cent average weight loss versus 13.7 per cent for Wegovy over 72 weeks, according to Eli Lilly.
Novo's suit points to a Zepbound TV commercial that tells viewers patients on the drug lose 50 pounds on average compared with 33 pounds on Wegovy — figures drawn from those SURMOUNT-5 results. But the complaint argues those comparisons are now materially misleading because they do not account for high-dose Wegovy, the 7.2-milligram formulation that entered the U.S. market in March 2026. Trial data for that higher dose showed average weight loss of approximately 19 per cent, which Novo calls "clinically consistent" with Zepbound's results in Lilly's most recent rigorous trial.
"As new and more effective treatment options become available, people deserve accurate information that reflects the latest scientific evidence and helps them make informed care decisions," said John F. Kuckelman, senior vice president and group general counsel at Novo Nordisk, in a press statement announcing the lawsuit.
Novo said Lilly acknowledges the higher dose of Wegovy in its ads only through a small footnote that the complaint describes as "ambiguous, confusing, virtually illegible, and wholly inadequate." The lawsuit also alleges Lilly takes the same approach in ads comparing Mounjaro and Ozempic, omitting newer data on a higher dose of Novo's diabetes drug that has been approved for more than four years.
Lilly stands behind the science
In a statement on Tuesday, as per CNBC, Lilly said it stands “firmly behind our advertising.” The company also said the “gold standard for comparing medicines is a robustly designed, well-conducted head-to-head clinical trial,” such as the one it uses in its ad campaigns to compare its obesity injection, Zepbound, to Wegovy. That remains the only study that directly pits those drugs against each other.
"It is truthful, it is transparent, and it is grounded in the most direct scientific evidence available — exactly what patients deserve," Lilly said. "We will continue to focus on the science and defend against this lawsuit vigorously."
Novo asked the court to permanently block the ads, require corrective advertising from Lilly, and award financial damages. The company has also signalled it may seek a preliminary injunction to pull the campaigns while the case proceeds. According to the suit, the Zepbound TV commercial alone has generated more than 700 million impressions since airing began around the end of April.
Market share fight intensifies
The lawsuit marks the latest escalation in an increasingly aggressive battle for dominance in the GLP-1 market, which analysts expect to generate approximately US$100 billion in annual sales within the next decade, according to Reuters. Lilly has gained significant ground: Zepbound posted roughly US$4.2 billion in first-quarter 2026 sales, an 80 per cent year-over-year increase.
Novo held an early lead through its first-mover advantage with Wegovy and Ozempic but has watched prescription share erode as providers and patients gravitated toward Lilly's products on the strength of the SURMOUNT-5 data. High-dose Wegovy, the oral obesity pill, and strategic price cuts are all part of Novo's counter-offensive.
