The lawsuit is the result of an Abbreviated New Drug Application (ANDA) filed by Mylan with the Food and Drug Administration (FDA) concerning its intent to market a generic omeprazole product in the US. The antisecretory drug omeprazole is marketed in the US by AstraZeneca, L.P. under the brand name Prilosec® and is marketed internationally by AstraZeneca as Losec®.

The basis for AstraZeneca's complaint is that the action by Mylan infringes upon several patents relating to Prilosec®, which provide protection to the year 2014. These patents include coverage for formulations and for methods of using Prilosec®. The substance patent, which expires in 2001, has not been challenged by Mylan.

AstraZeneca intends to fully enforce its patent rights and is steadfast in its belief that all of the patents are valid.