Novo Nordisk (NVO) Takes Legal Action Against Eli Lilly Over Misleading Weight-Loss Drug Advertisements

Key Points

• Novo Nordisk initiated legal proceedings against Eli Lilly in New Jersey’s U.S. District Court this Tuesday
• The lawsuit alleges Eli Lilly’s marketing materials for Zepbound and Mounjaro rely on obsolete clinical data to suggest superiority
• Eli Lilly’s advertising campaigns compare maximum-strength versions of its medications against lower-strength formulations of Wegovy and Ozempic
• According to Novo, the 7.2mg Wegovy formulation delivers approximately 47 pounds of weight reduction, nearly matching Zepbound’s ~48-pound result
• The pharmaceutical giant requests judicial intervention to remove advertisements, mandate corrective messaging, and obtain monetary compensation

Shares of Novo Nordisk (NVO) declined approximately 1.4% while Eli Lilly (LLY) experienced a roughly 2.7% decrease on Tuesday following Novo’s legal action alleging deceptive marketing practices in Lilly’s weight-loss medication campaigns.

Novo Nordisk A/S, NVO

The legal complaint was submitted to the U.S. District Court for the District of New Jersey. Novo’s allegations include violations of the Lanham Act, as well as federal and state regulations governing false advertising and unfair business practices.

The dispute centers on extensive television and digital media advertising initiatives promoting Lilly’s weight management medication Zepbound and diabetes treatment Mounjaro.

According to Novo’s complaint, these promotional materials rely on obsolete clinical trial information to create a misleading impression of superiority. A particular television advertisement, which has garnered more than 700 million views since late April, claims Zepbound patients achieve 50-pound average weight loss compared to just 33 pounds with Wegovy.

Novo contends the 33-pound comparison figure derives from studies utilizing lower-strength Wegovy formulations — specifically excluding the recently approved 7.2-milligram dosage that received regulatory clearance in March 2025.

According to Novo’s data, the higher-strength Wegovy formulation demonstrated average weight reduction of approximately 47 pounds in contemporary clinical studies. This figure closely approximates Zepbound’s 48-pound outcome based on Lilly’s most current trial results.

“It 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.

Lilly’s Response to Cease-and-Desist Request

Novo maintains this conflict has been brewing for months. The company dispatched a formal cease-and-desist notification to Lilly in April, immediately following regulatory approval of the enhanced-dose Wegovy formulation.

Lilly chose not to withdraw its advertising materials. According to Novo’s allegations, the company instead incorporated what Novo characterizes as an “ambiguous, confusing, virtually illegible” footnote referencing the higher dosage’s existence — without clearly communicating its improved effectiveness.

Novo’s legal demands include permanent injunctive relief blocking the advertisements, mandatory corrective advertising campaigns, and monetary damages. Should Lilly refuse voluntary removal, Novo intends to pursue emergency preliminary injunction relief to halt the campaigns during litigation.

Lilly did not respond to requests for comment.

Diabetes Medication Comparison Also Challenged

The legal action extends beyond Zepbound and Wegovy comparisons. Novo additionally accuses Lilly of employing identical misleading tactics when marketing Mounjaro against Ozempic — specifically omitting performance data for a higher-strength Ozempic formulation approved more than four years ago.

Direct comparative clinical trials between maximum-approved dosages of Wegovy and Zepbound have never been conducted. Novo argues this absence of head-to-head data means Lilly lacks legitimate grounds to assert superiority over Novo’s current medication portfolio.

“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,” Kuckelman said.

The Zepbound television commercial alone has been viewed over 700 million times since it started airing around the end of April.

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