Ozempic maker Novo Nordisk said on Tuesday it is suing arch US rival Eli Lilly over “false and materially misleading” adverts for its competing weight-loss and anti-diabetes treatments.

The Danish pharmaceuticals heavyweight complained that the US group – which makes rival weight-loss treatments Zepbound and Mounjaro – “intentionally selected outdated studies” that compared Lilly’s highest doses against lower doses of Novo Nordisk’s medicines.

Eli Lilly’s ads “deceptively (presented) those results as proof of broad, product-level superiority while burying or omitting critical clinical context”, Novo Nordisk said.

Novo Nordisk has developed a molecule called semaglutide, while Eli Lilly developed rival molecule tirzepatide.

The competing drugs are a financial windfall for each of the pharmaceutical companies.

“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, Novo Nordisk’s general counsel.

“Healthcare companies have a responsibility to keep their public claims accurate and current – ineffective, fine-print disclaimers do not fix the misleading impression created by major national campaigns.”

The target of the Danish group’s wrath is an advertising campaign that was “aired during recent, widely viewed global sporting broadcasts and on TikTok and Facebook, causing widespread confusion”, it said.

Eli Lilly responded to its rival’s accusations with a statement saying that the trial which underpins its advertising, known as Surmount-5, is “the only direct, head-to-head randomised clinical trial comparing tirzepatide and semaglutide in the context of weight management”.

An Eli Lilly spokesperson added that “rather than competing on the merits of its products, Novo is asking a court to prevent Lilly from communicating the results of this trial. We firmly stand by our advertising campaign.”

Anti-obesity treatments mimic a hormone secreted by the intestines, GLP-1.

They can be used for weight loss and/or to treat type 2 diabetes, the most common form of the disease.