Once a United States patent has issued, it can be challenged at the USPTO by filing a request for ex parte reexamination of the patent, or by initiating an inter partes dispute such as a request for post-grant review, inter partes review, or (for certain kinds of patents) a covered business method patent review.

Additionally, a patent owner may request that the USPTO “consider, reconsider, or correct information believed to be relevant” to the patent owner’s patent via supplemental examination.

Ex Parte Reexamination:
Any person (including the patent owner) can request ex parte reexamination (EPR) of a patent at any time during the period of enforceability of the patent (generally, six years from the date on which the patent expires). The requester must submit prior art (patents or printed publications) and establish that this prior art raises a “substantial new question” of patentability (SNQ). If the USPTO orders reexamination, the proceeding is ex parte in nature — the requester is precluded from participating — and it is based on all or some of the art submitted. The proceeding will be conducted to its conclusion, with the issuance of a reexamination certificate.

Post-Grant Review:
Post-grant review (PGR) is an adversarial proceeding before the Patent Trial and Appeal Board (PTAB) to review one or more claims of a patent. Importantly, the challenged claims must have issued from an application that was subject to the first-inventor-to-file provisions of the America Invents Act (AIA).

Claims may be challenged for any grounds that could be raised under 35 U.S.C. § 282(b) or (3), including subject matter eligibility, anticipation, obviousness, enablement, written description, public use, on-sale activity, or other public disclosures.

The PGR process begins with a third-party petition that is filed (a) before that party files a declaratory judgment action alleging invalidity of a claim of the patent, and (b) within 9 months after the patent is granted (or reissued).

The petition must establish that it is “more likely than not” that at least one challenged claim is unpatentable, or raise a novel or unsettled legal question that is important to other patents or applications. If the proceeding is instituted and not dismissed (e.g., by consent of the parties), a final determination by the PTAB will be issued within 1 year (extendable for good cause by 6 months).

PGR proceedings also permit litigation-like procedures, including limited discovery, protective orders, and settlement.

Importantly, PGR produces legal estoppel for the petitioner that applies to (a) any ground that the petitioner “raised or reasonably could have raised” during the proceeding, and (b) all USPTO, International Trade Commission (ITC), and district court (litigation) proceedings. Estoppel arising from a PGR proceeding attaches upon the final written determination of the PTAB, and may preclude the petitioner from raising nearly all invalidity defenses during litigation because the grounds for challenging a patent under PGR are so broad.

Inter Partes Review:
Inter partes review (IPR) is an adversarial proceeding before the Patent Trial and Appeal Board (PTAB) to review one or more claims of a patent only on a ground that could be raised under 35 U.S.C. §§ 102 or 103 (patents and publications raising issues of novelty and obviousness, respectively).

IPR is available against any patent, regardless of its filing date, but certain considerations pertain to patents issued from an application that was subject to the first-inventor-to-file provisions of the America Invents Act (first-inventor-to-file patents). For first-inventor-to-file patents, the IPR process begins with a third-party petition that is filed after the later of either (a) 9 months after the patent is granted (or reissued), or (b) if a PGR is instituted, termination of the PGR. These deadlines do not apply to first-to-invent patents.

The petition for IPR must be filed before the petitioner files any declaratory judgment action alleging invalidity of a claim of the patent. Alternatively, if a third party is served with an infringement complaint by a patentee, the third party has one year to file a petition for IPR.

The petition must establish a “reasonable likelihood” that the petitioner will prevail on at least one claim. If the proceeding is instituted and not dismissed (e.g., by consent of the parties), a final determination by the PTAB will be issued within 1 year (extendable for good cause by 6 months).

IPR proceedings, like PGR proceedings, also permit litigation-like procedures, including limited discovery, protective orders, and settlement.

Importantly, IPR produces legal estoppel for the petitioner that applies to (a) any ground that the petitioner “raised or reasonably could have raised” during the proceeding, and (b) all USPTO, International Trade Commission (ITC), and district court (litigation) proceedings. Estoppel arising from a IPR proceeding attaches once all appeals are exhausted, and applies to invalidity defenses based on patents and printed publications that were or could have been raised during IPR.

Supplemental Examination:
Supplemental examination is a procedure by which a patent owner may request that the USPTO “consider, reconsider, or correct information believed to be relevant” to the patent owner’s patent. The “information” may include any information, including patents, journal articles, evidence of on-sale activity, etc., and may involve any ground of patentability (e.g., subject matter eligibility, anticipation, public use or sale, obviousness, written description, enablement, indefiniteness, and double-patenting).

So long as the “information” is considered, reconsidered, or corrected during a supplemental examination of the patent, a court or agency cannot hold the patent unenforceable based on conduct relating to that information in a prior examination of the patent (e.g., the original examination).

Nevertheless, this relief is not available to the patent owner if an allegation is pleaded with particularity in a civil action or set forth with particularity in a notice received by the patent owner under the Federal Food, Drug, and Cosmetic Act before the patent owner files a request for supplemental examination to consider, reconsider, or correct information forming the basis for the allegation.

This relief is also unavailable if a defense (based upon information that was considered, reconsidered, or corrected pursuant to a supplemental examination request) is raised in an action brought in the International Trade Commission (under § 337(a) of the Tariff Act of 1930) or in a civil action brought in a federal district court (under 35 U.S.C. § 281), unless the supplemental examination and any ex parte reexamination ordered pursuant to the request are concluded before the date on which the action is brought.