Ex Parte Reexam vs Inter Partes Review: A 2025 Decision Framework

Two procedures sit at the center of the post-issuance patent challenge ecosystem: inter partes review (IPR) at the PTAB and ex parte reexamination (EPR) at the USPTO. Through most of the post-AIA era, IPR was the default for invalidity challenges. Through 2025, the calculus has shifted. This is a side-by-side framework for choosing between them given current procedural conditions.

Who can use each

112 rejections do not support an SNQ request in ex parte reexam, but the examiner may issue 112 rejections against new or amended claims introduced during the proceeding.

How challengers participate

IPR is adversarial. The petitioner participates throughout the proceeding, presents argument, examines witnesses, and receives a final written decision from a three-judge PTAB panel.

EPR is ex parte. After the request is filed and SNQ is granted, the third-party requester has no further substantive participation. The procedure runs between the USPTO and the patent owner. The challenger's role is front-loaded into the request itself.

For challengers who want active control of the procedure, IPR has a structural advantage. For challengers who want to put the prior art into the patent owner's hands at the USPTO and let the examiner work, EPR is sufficient.

Cost

IPR's higher cost reflects its adversarial structure: petitioner participation through deposition, oral hearing, and briefing across roughly an 18-month proceeding. EPR's lower cost reflects the front-loaded request and the absence of post-order petitioner participation.

Timing

EPR pendency averages 17.4 months across 4,500+ closed utility-patent reexaminations. That includes SNQ determination (within three months), patent owner statement, and the office action sequence. PTAB appeals when invoked add 12-18 months. CAFC review adds another year.

IPR has a statutory institution decision within six months of filing and a final written decision within 12 months of institution under 35 U.S.C. 316(a)(11), extendable up to 18 months for good cause. PTAB-to-CAFC adds another year. The headline IPR timeline is faster to final disposition, but the front-end uncertainty (institution risk) is materially higher in 2025 than it was pre-rescission.

Success rates

EPR outcomes across closed cases:

• Reexamination certificate issued: 94% of closed cases.
• SNQ denied at the gate: 5%.
• Other termination: approximately 1%.

A "certificate issued" outcome does not mean all original claims survived. Most certificates reflect amended or partially canceled claims.

IPR outcomes through FY2024 ran broadly as follows: institution rate of approximately 68% by petition (74% by patent), with the majority of instituted cases producing at least some claim found unpatentable. Among petitions reaching a final written decision, mixed-and-all-unpatentable outcomes have been the dominant pattern.

In 2025, the institution rate has come under pressure as the PTAB has applied discretionary denial more aggressively following the late-February rescission of the June 2022 Vidal Fintiv memo. Petitioners now face meaningfully higher institution-denial risk than they did through 2023-2024.

Estoppel

IPR estoppel under 35 U.S.C. 315(e) is the single largest doctrinal difference. (Deeper on estoppel in reexam.) After a final written decision, the petitioner cannot raise, in any subsequent USPTO proceeding, district court action, or ITC investigation, any ground that was raised or "reasonably could have been raised" during the IPR. The bar is broad.

EPR has no comparable statutory estoppel. A challenger who pursues an EPR can re-raise the same prior art in district court, with no procedural bar. The 2025 surge in third-party EPR filings is driven, in significant part, by this asymmetry.

When each makes sense

Choose IPR when:

• The challenger wants a final adjudicated decision with adversarial briefing.
• The challenger is willing to accept estoppel in exchange for a higher-confidence final outcome.
• The prior art is strong enough that institution risk is manageable under current PTAB practice.

Choose EPR when:

• The challenger wants to preserve litigation optionality.
• Budget is constrained.
• The challenger missed the one-year window from complaint service that restricts accused infringers from filing IPR.
• The prior art profile is closer to "raises a substantial new question" than "renders unpatentable beyond reasonable dispute."
• The challenger does not need direct procedural participation after the request is filed.

In 2025, the population choosing EPR has expanded significantly. Procedural shifts at the PTAB have moved cases that previously would have been IPR candidates into the EPR column. Whether the new equilibrium holds depends on whether PTAB discretionary denial practice continues to favor patent owners through 2026.