Novo Nordisk is suing Eli Lilly over ads it says mislead consumers on weight loss drug efficacy

Novo Nordisk filed a lawsuit against Eli Lilly $LLY on Tuesday, alleging that advertising campaigns for Lilly's obesity drug Zepbound and diabetes drug Mounjaro mislead consumers by using outdated clinical data to suggest those treatments are more effective than Novo's rival injections.

The suit, filed in the U.S. District Court for the District of New Jersey, seeks a permanent court order prohibiting the ads and compelling Lilly to issue corrective advertising. Novo is additionally pursuing financial damages. On July 24, it filed a motion for a preliminary injunction asking the court to halt the ads while the case proceeds. Lilly did not initially respond to a request for comment, but it has since denied any wrongdoing and said it stands behind its advertising and will defend itself vigorously, according to Reuters.

Novo's specific complaint centers on ads that compare the highest doses of Lilly's drugs to lower doses of Novo's treatments, without accounting for newer data on Novo's products. One TV commercial, which the suit says has received more than 700 million impressions since airing around the end of April, states that patients on Zepbound lose 50 pounds on average compared to 33 pounds on the 2.4-milligram dose of Wegovy. Novo argues that its recently approved 7.2-milligram high-dose version of Wegovy, which entered the market in March, showed average weight loss of 47 pounds — a result the company describes as comparable to Zepbound's performance in Lilly's most recent trial. Novo's complaint extends the same allegation to Lilly's diabetes advertising, arguing that ads comparing Mounjaro with Ozempic similarly omit more recent data from a higher-dose version of Novo's drug.

"While it may have been accurate to say that before 7.2 milligrams became available for Wegovy, it is no longer accurate to say that," John Kuckelman, Novo's group general counsel, told CNBC. He added that the lawsuit comes after Lilly declined to pull or amend the ads in response to a formal cease-and-desist letter Novo sent in April.

In a statement announcing the motion, Kuckelman said: “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that selectively compare lower doses of Novo Nordisk’s medicines against higher doses of Lilly’s medicines, based on outdated studies, leave patients with the mistaken impression that Lilly’s drugs are vastly superior, and that is simply not true.” Novo said Lilly has not removed the campaigns since the suit was filed.

Novo's legal claims invoke the Lanham Act alongside a range of federal and state statutes governing unfair competition and false advertising.

The lawsuit arrives as Novo works to recover ground it has lost to Lilly in the weight loss drug market. Though Novo entered the market first with Wegovy, Lilly has since overtaken it in sales, seizing the commercial lead across the category. Novo has been rolling out a weight loss pill that surpassed 3 million U.S. prescriptions, along with strategic price cuts, as part of its effort to claw back market share. The global obesity drug market is on track to reach $120 billion a year by 2030, according to Bloomberg.