December 2021 Newsletter

Vol 14, Issue 4

PTAB Post-Grant Proceedings

By Daniel P. Ochoa and Kevin J. Spexarth

The United States Patent and Trademark Office (USPTO) offers several administrative tools that can be used to challenge the validity of a granted patent. Introduced in the America Invents Act (AIA) of 2012, inter partes review (IPR) and post-grant review (PGR) proceedings can be an important part of both offensive and defensive patent strategies. Because they reach resolution in relatively short time frames and involve limited amounts of discovery, IPR and PGR proceedings can be cost-effective alternatives to traditional litigation.

What are Post-Grant Proceedings?

IPR and PGR are trial-like proceedings conducted before the Patent Trial and Appeal Board (PTAB) of the UPSTO in which a panel of administrative patent judges, all former patent practitioners, review the validity of a granted U.S. patent’s claims. IPR and PGR proceedings are inter partes, meaning that a patent challenger (i.e., the petitioner) and the challenged patent’s owner (i.e., the patentee) are directly involved in the proceedings as adverse parties. Since invalidation of the challenged patent can cause the termination of a patent infringement suit, post-grant proceedings can be utilized in parallel with a conventional patent infringement litigation defense.

While the procedures for IPRs and PGRs are similar, there are several key differences between the two which are detailed in the sections below.

Initiating a Post-Grant Proceedings

To initiate an IPR or PGR, a patent challenger must file a petition for review by the PTAB that identifies the claims being challenged along with an explanation of why the claims are believed to be invalid. The legal standard used by the PTAB to determine whether to institute a trial differs for PGRs and IPRs. To commence an IPR, a petitioner must establish a reasonable likelihood that they will prevail in invalidating at least one claim. By contrast, PGRs require a higher standard that at least one challenged claim is more likely than not to be deemed unpatentable.

IPRs and PGRs are also subject to different timing requirements. To initiate a PGR, a petition must be filed within nine months of a patent’s issuance. A petition to institute an IPR may only be filed after the nine-month window to file a PGR has closed and any PGR proceedings involving the patent have concluded. Additionally, an IPR must be filed within one year of a patent challenger being served with an infringement complaint by the patentee.

Grounds for Challenging Patent Claims

Perhaps the most significant difference between an IPR and a PGR are the grounds on which the validity of a patent’s claims may be challenged. In an IPR, patent claims can only be challenged on the basis of anticipation and obviousness. Furthermore, only issued patents, patent applications, and printed publications may be relied upon as prior art in an IPR. By contrast, a PGR may be instituted based on nearly any grounds that can be used to challenge the patentability of a patent claim, including an alleged lack of compliance with the written description, enablement, or subject matter requirements. In addition to patents and printed publications, in a PGR proceeding allegations of anticipation and obviousness may be based on evidence of public use, on-sale activity, or other public disclosures .

Potential for Estoppel

While post-grant proceedings may offer efficient methods for invalidating a patent and potentially resolving litigation, these benefits need to be weighed against the potential estoppel effects of the post-grant proceedings on future litigation. If the PTAB issues a final written decision upholding the validity of the challenged claims, the petitioner will no longer be able to challenge the validity of the patent based on “any ground that the petitioner raised or reasonably could have raised” in the IPR or PGR. Thus, because the grounds for validity challenges available in a PGR are much broader than an IPR, the estoppel effects of a PGR can be greater than those of an IPR.


Post-grant proceedings are often cheaper, faster, and more likely to invalidate a patent than presenting invalidity arguments in litigation. These benefits, however, come with the risk of estoppel effects that must be carefully considered. If you have any questions regarding post-grant proceedings, please contact your attorney at Andrus Intellectual Property Law.

Andrus Attorneys Selected for Inclusion in 2021 Super Lawyers List and Rising Stars List

We are pleased to announce that Joe Kuborn, Aaron Olejniczak and Pete Holsen have been selected to the 2021 Wisconsin Super Lawyers list and Emily Chilson and Kevin Spexarth were named Rising Stars in the State of Wisconsin.