In the shifting landscape of U.S. patent law, Inter Partes Review (IPR) has long been regarded as the gold standard for challenging patent validity. That landscape, however, is no longer what it once was. Since the USPTO’s policy realignment in 2025, institution decisions have become increasingly discretionary and policy-driven. Petitioners now confront procedural considerations that extend well beyond the merits of their prior art. New discretionary denial frameworks, formalized in the March 24, 2025 Boalick Memorandum [1] and the March 26, 2025 Steward Memorandum [2], have prompted many patent stakeholders to reconsider their approach and to look more closely at Ex Parte Reexamination (EPRx) and Post-Grant Review (PGR) as dependable strategic alternatives.
Whether the objective is to challenge a competitor’s patent or to reinforce one’s own portfolio in anticipation of future disputes, a clear understanding of reexamination has become essential.

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Why Reexamination Is Gaining Momentum

As IPR filings have encountered increasing headwinds, driven by expanded discretionary denials and more restrictive institution practices, requests for Ex Parte Reexamination have climbed to record levels. This shift is not coincidental. Two features of the reexamination framework, in particular, have made it increasingly attractive.
First, reexamination operates under a different institutional framework than IPR, one that is less influenced by policy-based considerations. Unlike IPR, where institution may be affected by factors such as parallel district court proceedings under the Fintiv framework  or concerns regarding “settled expectations,” reexamination must be ordered once a Substantial New Question (SNQ) of patentability is established. The SNQ standard, however, is not merely procedural: requests relying on cumulative art, recycled arguments, or marginal reinterpretations are regularly denied. Nonetheless, the analysis remains centered on the prior art and the substance of the challenge rather than on broader discretionary factors, making outcomes more closely tied to the quality of the request. [3] 
Second, reexamination involves a different estoppel profile than IPR. A third-party requester is generally not barred from raising the same invalidity positions in subsequent district court litigation, in contrast to the statutory estoppel that follows a final written decision in IPR. At the same time, it is recognized that reexamination may still have litigation consequences, including claim amendments, examiner reasoning, and prosecution history that can influence claim construction, equivalents, or preclusion arguments. Even so, the absence of formal IPR estoppel can provide additional flexibility for parties assessing longer-term litigation strategy.³

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Key Features of Ex Parte Reexamination

Who may file. Any party may request reexamination, including the patent owner, a third-party competitor, or even the USPTO Director. When a request is submitted through counsel, the requester may remain anonymous as a procedural matter; in parallel litigation, however, discovery or circumstantial evidence may reveal the real party in interest, particularly where strategy or counsel overlaps.
Timing. A request may be filed at any point during the period of enforceability of the patent, typically the patent term plus any applicable extensions.
The governing standard. To initiate the process, the requester must demonstrate an SNQ of Patentability. This requires presenting prior art or a new interpretation of existing art that was not previously considered, or was not previously considered in the manner now advanced.
Permissible grounds. Reexamination is limited to challenges based on patents and printed publications. Other bases for invalidity, such as public use, on-sale activity, or subject-matter eligibility, fall outside the scope of the proceeding.​

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How the Process Unfolds

The request. The proceeding begins with the submission of the statutory fee and a detailed statement identifying the specific claims to be reconsidered and explaining how the cited prior art raises a substantial new question of patentability.
USPTO determination. Within three months, the Office must decide whether an SNQ exists. This initial determination governs whether the proceeding will move forward.
Order for reexamination. If the Office finds that the statutory standard has been satisfied, it issues an order granting reexamination.
Patent owner statement. The patent owner is given two months to respond to the order. If a patent owner statement is filed, the third-party requester is afforded a single opportunity to reply. After that point, the requester is generally excluded from further participation—a material procedural limitation for challengers, who cannot respond to later claim amendments, examiner errors, or evolving arguments as they can in IPR.
Examination on the merits. The patent then undergoes a renewed examination by the Central Reexamination Unit. During this phase, the owner may amend or cancel claims to address the cited art, though any amendment must narrow rather than broaden the scope of the claims.
Reexamination certificate. The proceeding concludes with the issuance of a reexamination certificate, which confirms, amends, or cancels the affected claims.

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Procedural Flow of a USPTO Ex Parte Reexamination

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