Ex parte Reexamination as a Litigation Counterpart: A Quietly Powerful Tool in the Right Case

From: https://ptacts.uspto.gov/ptacts/public-informations/petitions/1558437/download-documents?artifactId=1oJJCXPzzZe2QRxRpqsfSzUWEB9EHWoDV4Uy_l9QvaGjmz6asezl1ZI

Patent litigation often forces accused infringers into a familiar set of strategic choices: defend validity head-on in district court, pursue AIA post-grant proceedings at the USPTO, or attempt some combination of both. In recent years, inter partes review (IPR) has dominated that conversation. But in the shadow of IPR’s increasingly selective institution rates (a specific policy choice made by the new Director), ex parte reexamination may again offer a surprisingly effective counterpart to active litigation.

A recent order from the Western District of Texas provides a useful reminder that ex parte reexamination is not merely a relic of pre-AIA practice. Wenyong Yue, et al. v. Reaction Labs, LLC, No. 1:24-CV-1125-RP, slip op. (W.D. Tex. Jan. 20, 2026). Instead, when deployed thoughtfully, ex parte reexamination can materially shift the balance in a live infringement dispute, including at the preliminary injunction stage. 

Ex Parte Reexamination vs. Inter Partes Review: The Institution Gap Matters More Than Ever

The strategic resurgence of ex parte reexamination starts with a simple reality: institution rates matter. While inter partes review remains a powerful mechanism, it is no longer the near-automatic gatekeeper it once was. Following Director Squires’ decision to consolidate decision-making within the Director’s office, IPR institution rates have fallen to historic lows. For accused infringers facing tight timelines or early injunctive risk, the uncertainty of IPR institution can be a serious liability.

Ex parte reexamination operates under a very different standard. Institution turns on whether the request raises a “substantial new question of patentability,” a threshold materially lower than the new heightened standards for IPR the Director applies. As a practical matter, that difference translates into significantly higher institution rates (approximately 93% for ex parte versus a recent rate of 4% or less and a historical rate of roughly 67% for IPRs). While institution alone does not determine outcome, it is a critical first step in challenging a patent.

In litigation, that distinction can be decisive. Even a non-final Office Action can alter how a court views claim vulnerability, particularly when assessing validity under the relatively forgiving standards applicable at the preliminary injunction stage.

How Ex Parte Reexamination Can Shift Leverage During Active Patent Litigation

Ex parte reexamination is often criticized for its limitations. The requester has no right to participate after filing, no ability to respond to patent owner arguments, and no estoppel protection from future assertions. Those critiques are fair—but incomplete. In litigation, the value of ex parte reexamination does not lie in procedural parity with IPR. It lies in evidentiary leverage.

Courts evaluating preliminary injunctions do not require clear and convincing proof of invalidity. Instead, they ask whether the accused infringer has raised a substantial question regarding validity, i.e., whether the patent realistically appears “vulnerable.” In that context, a detailed examiner rejection can carry real weight, even if it is non-final and may ultimately be overcome.

The Reaction Labs order illustrates this dynamic well. There, the court initially entered a preliminary injunction after concluding that the accused infringers had failed to raise a persuasive validity challenge. That calculus changed once the USPTO instituted ex parte reexamination and issued a non-final Office Action rejecting all claims of the asserted patent. The court treated that Office Action as a meaningful change in circumstances, sufficient to revisit—and ultimately vacate—the injunction

Importantly, the court did not treat the examiner’s rejection as dispositive proof of invalidity. Instead, it focused on the correct question for that stage of the case: whether the patent holder could still show a likelihood of success on the merits in light of the USPTO’s analysis. The answer for this court, at least on the existing record, was no.

Timing, Flexibility, and Procedural Advantages of Ex Parte Reexamination

Historically, ex parte reexamination was rarely an effective litigation tool because it was simply unlikely to reach a conclusion in advance of the scheduled trial date. But in recent years, the Patent Office has addressed the backlog of pending reexaminations, and the current average pendency is little more than a year. Additionally, requests can be prepared and filed quickly, without the extensive front-loaded expert work that often accompanies IPR petitions. That can be critical when an accused infringer is facing an early preliminary injunction motion or a fast-moving district court schedule.

Additionally, because ex parte reexamination does not carry the same real-party-in-interest concerns or estoppel consequences as IPR, it offers challengers greater flexibility. Parties can pursue reexamination without the real party in interest limitations of IPR proceedings and without foreclosing later invalidity arguments in court. That flexibility is particularly attractive in cases with multiple potential defendants, where claim construction is still evolving, or where the full prior art landscape has not yet been tested.

Of course, that flexibility cuts both ways. Patent owners retain broad ability to amend claims, introduce new arguments, and reshape the patent during reexamination. But even that reality can benefit accused infringers in litigation. Amended claims may complicate infringement theories, narrow damages exposure, or undermine earlier injunction findings.

The Right Tool for the Right Moment: Choosing Between Ex Parte Reexamination and IPR in High-Stakes Patent Disputes

None of this is to suggest that ex parte reexamination should replace IPR as a default strategy. IPR remains the superior mechanism for obtaining binding, adversarial determinations of unpatentability with meaningful estoppel. But litigation doesn’t proceed in a vacuum, and strategic choices should reflect the procedural moment, the forum, and the relief at stake.

When early injunctive relief is in play, when institution risk is unacceptable, or when a rapid examiner record could materially affect how a court views validity, ex parte reexamination deserves serious consideration. The Reaction Labs decision underscores that courts are willing to engage with the substance of reexamination outcomes—particularly when those outcomes bear directly on the equitable calculus governing extraordinary remedies.