A federal appeals court ruled that Praxair could not have infringed on five Mallinckrodt patents for inhaled nitric oxide because the patents were invalid.

Mallinckrodt, the name-brand manufacturer of INOmax (nitric oxide gas), sued Praxair in 2015 for alleged patent infringement by its generic product Noxivent. The complaint in the U.S. District Court of Delaware claimed that Praxair’s generic infringed on its patents for a heart failure treatment and that the delivery mechanism infringed on several device patents.

In a 2017 trial, the judge ruled that Mallinckrodt’s patents for the drug were invalid, and that Praxair had not infringed on the device patents.