Since its enactment under the 2011 America Invents Act (AIA), inter partes review (IPR) has remained a pivotal tool for challenging the validity of patents. IPR was introduced under the AIA's initiative to improve the quality of the patent system and reduce the cost of challenging and invalidating bad patents. IPR is a trial proceeding held before the U.S. Patent and Trademark Office's (USPTO) Patent Trial and Appeals Board (PTAB) through which a third party can petition to challenge the validity of a patent.

IPR has become a standard tool for efficiently and effectively invalidating overly broad patents and has for over a decade been considered a critical weapon for defending against patent infringement charges. Still, from 2017 through 2023, IPR filings have been trending downwards, with 86 fewer petitions filed each year on average over that period. However, ex parte reexamination (EPR) filings—another patent invalidation process available long before IPR—have increased by approximately 28 more EPR filings each year over that period, and are on track to increase by over 100 new EPR filings this fiscal year. This article explores potential reasons for these surprising trends.