What is Inter Partes Review?
Who can file and when, the grounds allowed, the one-year bar after being sued, the 18-month timeline, what institution and final decisions look like, and the estoppel that follows.
Definition
Inter partes review (IPR) is a trial proceeding before the Patent Trial and Appeal Board (PTAB) in which anyone other than the patent owner petitions to cancel one or more claims of an issued patent as anticipated or obvious over prior art consisting of patents and printed publications. Created by the America Invents Act, it is the most common way to challenge patent validity in the United States.
Key Facts
- Statute: 35 U.S.C. §§ 311 to 319; procedure in 37 C.F.R. Part 42
- Grounds: Only § 102 anticipation and § 103 obviousness, and only on patents and printed publications; not § 101, § 112, on-sale bars, or public use
- When: Any time after 9 months from grant for AIA patents (immediately for pre-AIA), but a petitioner sued for infringement must file within 1 year of service of the complaint
- Threshold: The Board institutes if there is a reasonable likelihood the petitioner would prevail on at least one claim; if instituted, all challenged claims and grounds are reviewed
- Timeline: Institution decision about 6 months after filing; final written decision within 12 months of institution, so roughly 18 months end to end
- Standard: Preponderance of the evidence, with claims construed under the Phillips standard used in court
- Estoppel: After a final decision the petitioner cannot assert in court or at the USPTO any ground it raised or reasonably could have raised
- Cost: Six figures in USPTO fees and attorney time through final decision, a fraction of district court invalidity litigation
How an IPR Proceeds
- Petition: The challenger files with claim charts mapping each challenged claim to the prior art, usually with an expert declaration
- Preliminary response: The patent owner may argue against institution, including on discretionary grounds such as parallel litigation timing
- Institution decision: Within about 6 months; discretionary denials and the Board's institution rate have shifted with each USPTO administration
- Trial: Limited discovery, the patent owner's response, an optional motion to amend claims, the petitioner's reply, and an oral hearing
- Final written decision: Within 12 months of institution, appealable to the Federal Circuit
- Settlement: Permitted at any stage, and common once institution is granted
IPR in Litigation Strategy
A defendant sued on a patent typically files an IPR within the year, then moves to stay the district court case pending the Board's decision. Stays are granted more often when the IPR is filed early and covers all asserted claims. Because the Board has historically cancelled at least some claims in a majority of instituted trials, the filing itself changes settlement dynamics, which is why IPR is the standard first response to a patent assertion entity suit.
For patent owners, IPR risk is a portfolio quality question: claims that survive an IPR are worth far more, and claims with thin prosecution records over the closest art are the ones that get challenged. ArcPrime's patent invalidation tooling runs the same prior art search a petitioner would, on either side of the table.
Frequently Asked Questions
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Who can file an inter partes review?
Anyone who is not the patent owner, including competitors, defendants in infringement suits, and organizations that challenge patents on behalf of members. The petitioner must identify all real parties in interest, and a petitioner served with an infringement complaint on the patent must file within one year of service.
What grounds can be raised in an IPR?
Only anticipation under § 102 and obviousness under § 103, and only based on prior art patents and printed publications. Challenges based on subject matter eligibility, indefiniteness, written description, enablement, public use, or sales must be brought in court or, in some cases, in post-grant review within nine months of grant.
How long does an IPR take?
About 18 months. The Board decides whether to institute roughly six months after the petition is filed, and if it institutes, must issue a final written decision within 12 months, extendable by up to six months for good cause. Appeals to the Federal Circuit add another year or more.
What is IPR estoppel?
After a final written decision, the petitioner and its privies cannot assert in district court, at the ITC, or before the USPTO that a claim is invalid on any ground the petitioner raised or reasonably could have raised in the IPR. Because the estoppel covers grounds that could have been raised, petitioners search thoroughly before filing.
What is the difference between IPR and post-grant review?
Post-grant review (PGR) must be filed within nine months of grant and permits any ground of invalidity, including § 101 and § 112. IPR is available after that window closes and is limited to anticipation and obviousness over patents and printed publications. Both are decided by the PTAB on a similar timeline.
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