THE PARTIES Plaintiff: Ironburg Inventions Ltd. Plaintiff’s Firm: Manatt, Phelps, & Phillips Defendant: Valve Corporation Defendant’s Firm: Shook, Hardy & Bacon THE BIG PICTURE IPRs are powerful tools in combatting patent infringement, but they can negatively impact your litigation strategy. Here, Valve was unable to effectively argue invalidity at trial due to IPR estoppel.