Novo Nordisk Sues Eli Lilly in Federal Court on Tuesday July 21 Alleging 'Deceptive' Advertising Practices in GLP-1 Drug Marketing (Per STAT News Reporting); The Complaint Targets Advertising Claims That Novo Says Make Eli Lilly's Zepbound (Tirzepatide) and Mounjaro (Tirzepatide) Franchises Appear More Effective Than the Underlying Clinical Data Support Versus Novo's Wegovy (Semaglutide) and Ozempic (Semaglutide) Franchises
Novo Nordisk (NYSE: NVO) filed a federal lawsuit Tuesday July 21, 2026 against Eli Lilly (NYSE: LLY) alleging that Lilly has run 'deceptive' advertising campaigns for its GLP-1 drugs Zepbound and Mounjaro (both tirzepatide), per STAT News reporting. The Novo complaint reportedly targets marketing claims that make Lilly's tirzepatide franchise appear more effective than the underlying clinical data support relative to Novo's Wegovy and Ozempic (both semaglutide). The lawsuit arrives against a competitive backdrop where Lilly has been extending its US commercial lead in the obesity market: Q1 2026 sales showed Mounjaro at $8.7 billion (up 125% year-over-year) and Zepbound at $4.2 billion (up 80%), while Novo Nordisk faced flat-to-declining semaglutide revenue after March 2026 price cuts, and Lilly overtook Novo in US GLP-1 market share. The SURMOUNT-5 head-to-head Phase 3 trial published earlier in 2026 showed superior efficacy for tirzepatide over semaglutide on weight loss endpoints; Novo's complaint appears to focus on how Lilly extrapolates the SURMOUNT-5 comparative data into consumer-facing advertising. The dispute frames the GLP-1 marketing battlefield ahead of Q2 earnings reports (Lilly August 5, Novo August 6).