The weight-loss drug wars reached a new level of intensity Tuesday as Novo Nordisk sued Eli Lilly, accusing its arch-rival of misleading advertising.

The lawsuit, filed in federal court Tuesday, accuses Eli Lilly of using outdated data in advertising campaigns.

The lawsuit follows a cease-and-desist request and argues Lilly is using “deceptive” ads to claim its GLP-1 products are broadly superior to Novo’s medicines. Lilly countered that…