Novo Nordisk sues Eli Lilly over Zepbound and Mounjaro advertising

Novo Nordisk sued Eli Lilly and Lilly USA on July 21, 2026, in the U.S. District Court for the District of New Jersey. Novo says the companies' national commercials for the obesity drug Zepbound (tirzepatide) and the diabetes drug Mounjaro (tirzepatide) violate federal and state laws against false advertising and unfair competition, including the Lanham Act ^[5][7]. Lilly says the campaign is backed by its own head-to-head trial and that it will defend the case ^[5][6].

At issue is which doses the commercials put side by side. Novo's complaint says the spots match Lilly's highest injectable strengths against older, lower strengths of Wegovy (semaglutide) and Ozempic (semaglutide), and that they pass over the 7.2 milligram Wegovy dose the FDA cleared in March 2026 ^[5][7]. Novo says that strength produced an average weight loss of 19%, about 47 pounds, in its studies ^[7]. In clinical testing described by Healthcare Dive, the same dose was linked to roughly 19% weight loss, while Zepbound has been associated with up to 21% ^[6].

Novo's group general counsel, John Kuckelman, told Reuters the ads set about 50 pounds of weight loss on Zepbound against about 33 pounds on Wegovy, even though no trial has directly compared the strongest approved doses of the two medicines. Separate late-stage trials of those top doses showed averages of about 48 pounds for Zepbound and about 47 pounds for Wegovy, he said ^[5]. Novo's filing calls the advertising "maliciously and deceptively false" ^[5].

Lilly points to SURMOUNT-5, completed in 2024, which compared 10 mg or 15 mg of Zepbound with 1.7 mg or 2.4 mg of Wegovy ^[5]. A company statement said the ads are grounded in the best evidence available and that "the gold standard for comparing medicines is a robustly designed, well-conducted head-to-head clinical trial" ^[6]. A Lilly spokesperson said Novo is asking a court to block Lilly from sharing that trial's results, and that the company will "defend against this lawsuit vigorously" ^[5].

Novo says it sent a cease-and-desist letter in April 2026, after the 7.2 mg approval. Kuckelman said Lilly did not respond and instead added a disclaimer he considers inadequate ^[5]. By Novo's count, the ads have been shown to consumers more than 700 million times since Lilly revised them in late April, including during widely watched global sporting events and on TikTok and Facebook ^[5][6].

Novo is asking for an order pulling the ads and requiring a corrective campaign, plus damages that include Lilly's profits tied to the advertising. If Lilly does not remove the ads on its own, Novo said it will seek a preliminary injunction ^[5]. Alexandra Roberts of Northeastern University School of Law said damages "could be significant given the size of the market for these drugs," though she added that they may be limited by how long the disputed claims ran ^[5].

Lilly entered the dispute with the sales lead: Zepbound recorded $4 billion in the first quarter of 2026, compared with 18.2 billion kroner, about $2.7 billion, for Wegovy ^[6]. On the day of the filing, Novo's Copenhagen-listed shares fell 2% and Lilly's rose 0.5% ^[5]. The United States is one of only a handful of countries that let drugmakers advertise prescription medicines directly to consumers ^[5].

Why it matters for patients

This case is about advertising claims, not about whether these medicines work or are safe. No approval has changed, and no regulatory action against Zepbound, Mounjaro, Wegovy or Ozempic has been reported ^[5][6][7].

The two companies disagree about whether the numbers people see on television and social media reflect the doses patients are actually prescribed. Novo says the spots rely on comparisons that no longer hold up against its newer, higher dose; Lilly says it is presenting the only randomized head-to-head evidence directly comparing the two drugs ^[5][6]. Whether a trial has tested the highest approved doses of both medicines against each other has not been reported ^[5].

How the lawsuit could affect insurance coverage, list prices or access to either company's products has not been disclosed ^[5][6].

What happens next

No hearing date or court schedule has been reported. Novo has said it will seek a preliminary injunction if the ads keep running, and Lilly has said it will defend the suit ^[5]. Separately, the Wegovy 7.2 mg single-dose pen received approval from the European Medicines Agency in July 2026, based on STEP UP data showing up to 20.7% mean weight loss, with rollout across the European Union planned for the second half of 2026 ^[3].