For much of the past decade, post grant patent practice in the United States was dominated by the post-grant proceedings formed as part of the 2013 America Invents Act (AIA), including inter partes review (IPR) and post-grant review (PGR) proceedings before the Patent Trial and Appeal Board (PTAB). Ex parte reexamination, a far older mechanism dating back to 1981, was often viewed as a secondary or even obsolete option, with patent challengers preferring the newer mechanisms that allow for their continued involvement in a litigationesque process. That perception has changed. Over the past several years—and accelerating recently—patent reexaminations have re-emerged as a central strategic tool in patent disputes.
This resurgence is not accidental. It reflects a convergence of procedural uncertainty at the PTAB, cost pressures in litigation, evolving USPTO policy, and renewed appreciation for the unique strategic advantages reexamination offers.
One of the most significant drivers of renewed interest in reexamination is the increasing unpredictability of IPR institution decisions. Although IPR was designed to be a streamlined, merits focused alternative to district court litigation, discretionary denials have become a defining feature of PTAB practice.
Recent USPTO policy changes and leadership decisions have expanded the reasons for which IPR petitions may be denied without reaching the merits. These include considerations related to parallel district court litigation, prior USPTO review, timing, prior enforceable lifespan of the challenged patent, and perceived serial challenges. Industry reports document a sharp rise in procedural denials at the PTAB and a corresponding decline in IPR filings, even as patent litigation itself has increased.
By contrast, ex parte reexamination is governed by a far lower threshold: whether the request raises a “substantial new question of patentability.” Institution rates for reexamination historically exceed those for IPR, and the decision to grant reexamination is largely insulated from the discretionary overlays that now characterize PTAB practice.
Cost is another major factor fueling the reexamination revival. IPR proceedings, while less expensive than full district court litigation, routinely cost hundreds of thousands of dollars in legal fees and expert costs. Reexamination, by contrast, is an examination style proceeding conducted between the patent owner and the USPTO’s Central Reexamination Unit (CRU), with no discovery, depositions, or oral hearings.
Empirical studies show that reexaminations generally conclude faster than IPRs and at a fraction of the cost, while still producing outcomes that materially affect claim scope and enforceability. In an era of heightened litigation budgets and increasing scrutiny of legal spend, this cost differential is difficult for parties to ignore.
Another critical distinction between reexamination and IPR lies in estoppel. A final written decision in an IPR can bar the petitioner from later raising in district court any invalidity grounds that were raised or reasonably could have been raised during the PTAB proceeding. That estoppel risk has grown more acute as PTAB practice has evolved.
Ex parte reexamination carries no comparable statutory estoppel against the requester. Indeed, ex parte reexaminations can be requested confidentially, preventing the USPTO or the patent owner from knowing the identity of the challenger. As a result, reexamination offers a way to challenge patent validity at the USPTO without foreclosing later defenses in court. This feature has made reexamination particularly attractive as a fallback option for parties who were denied IPR institution or who wish to preserve flexibility in parallel litigation.
Although reexamination lacks the adversarial features of IPR, it often produces outcomes that are just as consequential. Studies show that reexamination has a significantly higher rate of claim amendment than IPR, where surviving amended claims are comparatively rare.
From a challenger’s perspective, narrowing amendments can be nearly as valuable as outright claim cancellation, particularly in infringement disputes. From a patent owner’s perspective, reexamination can serve as a tool to strengthen claims, clarify scope, and build a more robust prosecution record—sometimes in anticipation of, or during, enforcement.
Reexamination also interacts differently with district court litigation than IPRs. Courts have long recognized their inherent authority to stay cases pending reexamination, particularly when the proceeding is instituted early and covers all asserted claims. Judges frequently cite the potential for claim cancellation or amendment, as well as judicial efficiency, in granting such stays.
Importantly, reexamination is not subject to the same timing bars as IPR. Requests for ex parte reexamination can be filed at virtually any point during a patent’s enforceable life, including well after litigation has begun. This flexibility allows defendants to deploy reexamination strategically in circumstances where IPR is unavailable or impractical.
Finally, the USPTO itself has acknowledged and responded to the increased volume of reexamination requests. The Central Reexamination Unit has become a focal point for post grant validity review, and the Office continues to publish updated statistics reflecting sustained use of the procedure.
In fact, USPTO Director Squires, recognizing the increase in requests for reexamination, recently enacted a new process allowing patent owners to submit a “pre-order paper” challenging a request for reexamination to assist the Central Reexamination Unit with making its determination as to whether a substantial new question of patentability exists. It is too early to understand what impact this new process will have on overall reexamination statistics.
Unlike the PTAB, where policy direction has shifted repeatedly in recent years, reexamination practice has remained comparatively stable. That institutional consistency has contributed to renewed confidence in the process.
The resurgence of patent reexamination is not a return to the past, but a recalibration of post grant strategy in response to modern realities. As PTAB practice becomes more discretionary and complex, and as litigation costs continue to rise, parties are rediscovering the value of a procedure that is predictable, cost effective, and strategically flexible.
Reexamination is no longer merely an alternative of last resort. For many litigants and patent owners, it has become a core component of a balanced post grant and litigation strategy—one that is likely to remain prominent as the patent landscape continues to evolve.
Reexaminations are examiner driven proceedings conducted under USPTO examination standards. Their success depends heavily on front loaded advocacy and effective examiner persuasion, with limited third party participation after institution. As a result, reexaminations are best handled by IP focused, prosecution centric firms with deep experience in USPTO examination and reexamination practice.
IPRs by contrast, are adversarial, trial like proceedings before PTAB judges and are best managed by patent litigation centric firms. IPRs require formal briefing, expert declarations, depositions, oral argument, and in some cases discovery, where procedural rigor and meticulous record development are critical.
Selecting the right firm is therefore essential in any patent litigation strategy. Clients benefit from counsel with both a deep prosecution bench capable of successfully handling ex parte reexaminations and a robust patent litigation bench experienced in IPR practice. Attorneys who bridge prosecution and patent litigation practices are particularly well positioned to evaluate whether an ex parte reexamination, an IPR, or a coordinated use of both offers the best path forward. A firm that can guide clients in choosing and executing the right process as part of an integrated litigation strategy delivers a decisive advantage.
