The recent resurgence in ex parte reexamination demonstrates the importance of this post-grant review vehicle. It has become particularly important for patent challengers who may be estopped from requesting inter partes review (IPR), and for challengers who, for varying reasons, were unsuccessful before the Patent Trial and Appeal Board (PTAB). We review here the most recent ex parte reexamination statistics. We also cover new Federal Circuit case law elucidating what is required to establish a substantial new question of patentability (SNQ), which is the threshold requirement to initiate an ex parte reexamination.

As a preview, the most recent reexamination statistics indicate that both Requesters and Patent Owners may need to redefine what it means to succeed at the Central Reexamination Unit (CRU). This is because many patents emerge from reexamination only when claims are amended to avoid prior art.

In addition, Requesters and Patent Owners should consider the Federal Circuit’s holding in In re Cellect, 81 F.4th 1216 (Fed. Cir. 2023). There, the court lowered the threshold for finding an SNQ, bringing into play issues an Examiner circumstantially might have considered, but did not expressly consider in the file history. This is because the reexamination Requester should not have to disprove a negative implication when the Examiner fails to perform an act they could have performed.


After the America Invents Act (AIA) came into effect in 2012, ex parte reexamination filings steadily declined until 2019, when they began to rebound. Notwithstanding changes the current PTO administration has made with respect to discretionary denials of IPR petitions, 2023 saw a solid pace continue for a third straight year. However, reexamination requests will most likely never return to the popularity that they achieved in the years just prior to the passage of the AIA, when 600 to 800 new requests per year was the norm.

Beginning in 2020, about a third of ex parte reexaminations filed were against patents that had already faced an AIA challenge at the PTAB. The steady stream of requests for ex parte reexaminations filed after a “failed” AIA challenge has continued, but a dip in 2023 indicates that this trend should be watched closely in the coming years. Still, about a quarter to a third of all reexaminations in the most recent years were so-called do-over post grant challenges.

As we reported in our 2021 publication, historically, a CRU determination that all the claims of a patent were unpatentable at the conclusion of a reexamination proceeding was rare, coming in at around 10-15 % (whether or not a patent owner or a third party files the request). However, in recent years, the number of cases where all claims of

Reexam Requests Filed

Reexam-Requested Patents — PTAB Challenge Status

a patent are found unpatentable has increased to about 15-20% of the time. Thus, it appears it is becoming more difficult for Patent Owners to exit reexamination with unamended claims.

Not surprisingly, then, Patent Owners appear to have responded with more reexamination amendments. And those strategic amendments, in turn, have obtained favorable outcomes such as adding additional claims directed to infringing products. Without amendment, on the other hand, the reexamination process has benefited Requesters in recent years, with a majority of reexaminations terminating with none of the originally challenged claims confirmed as patentable.

Of particular interest is a more granular breakdown looking at all outcomes for claims challenged in a reexamination request, showing 64% of challenged claims emerging from reexamination either canceled or narrowed in scope.

If we shift the analysis to consider new claims presented and allowed during reexamination, we can see why Patent Owners are seizing the opportunity to add new claims to their patents during reexamination. As shown, 17% of claims listed in reexamination certificates are newly added over the course of the reexamination. These new claims are a mixed bag result for Patent Owners. They emerge having survived CRU scrutiny, but due to

Ex Parte Reexam Outcomes Patent Owner Requester

Ex Parte Reexam Outcomes Third Party Requester