America Invents Act post-grant reviews at the US Patent and Trademark Office (USPTO) have garnered attention, if only because of a seemingly high number of patent claims being impacted as a result. This update looks at three reasons why inter partes reviews may represent a paradigm shift in the fight over IP rights: 1. The statutorily mandated short inter partes review timeframe may result in more frequent stays of litigation, thus effectively transferring validity defense adjudications from district courts to the USPTO. 2. Challengers have a lower burden of proof to meet in cancelling patent claims in the USPTO when compared with proving invalidity during patent infringement litigation in federal courts. However, a favorable outcome may significantly benefit the patent owner, as the challenger’s failure to meet a low bar of proving invalidity may render validity challenges in subsequent (or co-pending) litigation much more difficult. 3. In regard to specific lawsuits, subsequent determinations of invalidity by the USPTO can trump prior Article III courts’ determinations of validity and liability, provided that any issue – even if unrelated to either validity of infringement – of the case is on appeal. However, challengers are estopped from raising the same arguments or arguments that “could have been raised” against a challenged claim in all subsequent litigation.