Novo Nordisk (NYSE: NVO) loses bid to halt Eli Lilly (NYSE: LLY) obesity drug adverts

A federal judge in Trenton, New Jersey, has refused Novo Nordisk's request for a preliminary injunction to stop Eli Lilly's advertising for its obesity and diabetes drugs. In a 25-page decision on 26 October, Judge Zahid Quraishi found that Novo had not shown that the adverts threatened its sales, damaged its goodwill or caused lasting harm to its clinical reputation, describing its case for irreparable harm as "inadequate to warrant the extraordinary relief it seeks".

Novo sued in July, alleging breaches of federal and state false-advertising and unfair-competition laws. Its central complaint is that Lilly's adverts compare higher doses of Zepbound and Mounjaro, both tirzepatide, with lower doses of Novo's semaglutide products, Wegovy and Ozempic. One advert carried a voiceover, with a written disclaimer, stating that people on Zepbound lost an average of 50 pounds against 33 pounds on Wegovy. Those figures closely match the results Lilly reported in May 2025 from SURMOUNT-5, a 72-week open-label head-to-head trial in 751 adults, in which participants lost 20.2% of body weight on tirzepatide and 13.7% on semaglutide, each at the maximum tolerated dose.

The judgment is narrower than the headlines suggest. Judge Quraishi did not rule on whether the adverts are false or misleading; he decided only that Novo had not cleared the high bar for interim relief on what he called a "very preliminary record". He found Novo's witnesses credible but concluded that Lilly's adverts had at most a negligible effect on the market between April and July, a period in which Novo's prescriptions were stable, and that money damages could compensate for any nontrivial harm. Novo said it was disappointed and that the litigation continues. Lilly denied wrongdoing and said it was pleased with the decision.

The substantive dispute concerns how comparative claims should be framed. SURMOUNT-5 was a genuine randomised comparison, which is more than much rival advertising rests on, but it was open-label, and Lilly's own release noted that the weight figures in pounds were not controlled for the trial's overall type 1 error rate. Whether quoting those figures to consumers, against products available at a range of doses, is fair will now be argued in the continuing case rather than on an emergency basis. The competing analyses both companies have promoted show how readily the same evidence can support rival messages.

The case lands in a tense regulatory climate for drug promotion. The United States is one of only a handful of countries that permit direct-to-consumer advertising of prescription medicines, and after a presidential memorandum in September 2025 the FDA sent thousands of warning letters and about 100 cease-and-desist letters to drugmakers and began rulemaking to require fuller risk information in broadcast adverts. Comparative efficacy claims aimed at patients sit squarely within that scrutiny. In the UK, where consumer promotion of prescription medicines is prohibited, Lilly has already lost an appeal over pre-licence promotion of an obesity drug.

The commercial stakes explain the litigation. Court papers put Novo's combined 2025 sales of its obesity medicines and Ozempic at about $32 billion, and the US market for injectable obesity drugs is projected to exceed $100 billion by the end of the decade. Novo is working to regain US share for its injectable obesity drugs, and advertising that frames the choice as a simple comparison of average weight loss works against that effort. The ruling removes the immediate threat to Lilly's campaign, but it does not rule out damages if Novo ultimately prevails on the merits.

For investors, the decision changes little in the near term: Lilly's campaign continues, and any remedy for Novo is now more likely to be financial than an order to pull the adverts. The more consequential question is regulatory. If the FDA's tougher stance on consumer advertising extends to how head-to-head data and dose comparisons are presented, both companies will need to frame comparative claims more cautiously, whatever the outcome in New Jersey.