A Data-Based Look at Ex Parte Reexaminations

Summary of Reexamination Study Results

For this study, we first reviewed all reexaminations filed between January 1, 2015, through July 31, 2022, and cross-referenced those reexaminations with district court patent litigations. This resulted in a set of 864 reexaminations (about 50.02% of all reexaminations for this same time period) that involved litigated patents. We further analyzed this subset of litigated-reexamined patents and observed the following: Over 72% of reexaminations resulted in at least one claim being canceled or amended, and over 42% of reexaminations resulted in all claims being canceled or amended (see table 1). Further context and analysis regarding these findings are provided below.

Reexamination Outcomes

At the outset, we observed that between January 2015 and July 2022, approximately 50% of reexamination requests involved litigated patents. This is markedly higher than the USPTO’s reported 37% of reexaminations filed between 1981 to September 2023 that involved patents “known to be in litigation.”

Pendency

During reexamination, there are no set timing requirements for an examiner to issue an office action. This uncertainty may raise concerns for a potential requester that the reexamination will last an inordinately long time. As previously noted, reexaminations are conducted with “special dispatch,” and—although this term is not precisely defined—it is clear that reexamination proceedings will receive priority over all other cases. Further, the USPTO guidance indicates that reexaminations related to a patent asserted in a district court litigation will receive priority over all other reexaminations. As discussed below, our data shows that this special status results in a very reasonable pendency of the action.

On average, the pendency for completed reexamination proceedings between January 1, 2015, and July 31, 2022, that involved litigated patents was approximately 467 days (about 15.33 months). The data also shows that litigated reexaminations complete about 3.2 weeks (23 days) more quickly than nonlitigated reexaminations, which suggests that the priority afforded to litigated reexaminations increases the speed with which litigated reexaminations are conducted. This is a substantially shorter time frame than the 767 days (25.2 months) average pendency for all reexaminations (both litigated and nonlitigated from 1981 to September 2023) reported by the USPTO. Accordingly, this result—which has not been previously reported by the USPTO (or otherwise)—quantifies for the first time the substantive effect of the priority status afforded to reexaminations that involve litigated patents. This result also suggests that the speed with which reexaminations are completed has increased since the proceeding was first introduced. Thus, in contrast to the general perception that reexamination is a lengthy, time-consuming process, this study found that reexaminations involving both litigated and nonlitigated patents are particularly time-efficient and, as discussed in more detail below, in many cases will reach resolution faster than IPRs.

Appeals also affect pendency as discussed below.

Decision on Granting Reexamination (SNQ)

The examiner is required to issue a decision on whether or not to order reexamination within three months of the filing date of the request. Reexamination will be ordered where the request raises an SNQ. This standard involves two separate inquiries—that is, the question of patentability must be both “substantial” and “new.” As to the first prong, a prior art patent or printed publication may be considered “substantial” where there is “a substantial likelihood that a reasonable examiner would consider the prior art patent or printed publication important in deciding whether or not the claim is patentable.” Regarding the second prong, a question of patentability may be considered “new” where (1) it is based on prior art patents or printed publications that were not previously considered, or (2) it presents previously considered art “in a new light or a different way that escaped review during earlier examination.” The examiner must issue the decision within three months following the filing date of a reexamination request. If a request is denied, the requester may seek review by petitioning the director within one month of the denial.

USPTO historical data for all reexaminations shows that examiners find an SNQ exists in about 92% of all reexaminations (with about 8% denied). For the January 2015 to July 2022 time frame, that percentage increased slightly to about 94% (with only 6% of reexaminations initially denied).

The SNQ grant rate increases again to about 95% when looking only at reexaminations involving litigated patents (as opposed to all reexaminations) during the January 2015 to July 2022 time frame. Compared to the IPR institution rate, the SNQ grant rate is significantly higher. For example, between January 2015 and July 2022, the institution rate for IPR petitions was only about 64%.

Claim Outcomes

The data collected shows that, for reexaminations filed between January 2015 and July 2022 challenging litigated patents, at least one claim was canceled or changed (i.e., added or amended) in over 62% of reexaminations; confirmation of all claims occurred in over 37% of cases. This is an important finding as compared to the USPTO’s available data that shows confirmation of all claims occurs in approximately 21.6% of all reexaminations and cancelation of all claims in only 13.7% of all reexaminations. The USPTO data does not distinguish between litigated and nonlitigated reexaminations, and only considers whether all claims were confirmed or canceled. Reexaminations with mixed results, claim amendments, or claim additions, however, are combined (accounting for 64.7% of USPTO-reported proceedings), making it difficult to draw conclusions about the results.

The data collected provides a more granular view of reexamination outcomes where claims changed—i.e., the bulk of reexamination outcomes (see table 2). To start, at least one claim was invalidated (canceled or disclaimed) in about 40% of terminated reexaminations involving a litigated patent, while at least one claim was confirmed in about 50% of terminated reexaminations. In addition, patent owners were successful in amending claims in about 24% of reexaminations and adding claims in about 25% of reexaminations. Importantly, over 62% of the time, claims were either canceled or amended.

The mixed nature of reexamination outcomes makes it difficult to characterize these outcomes as a “win” or “loss” for either side. Further study is needed to fully understand the impact of reexaminations with mixed outcomes on copending litigation. However, some useful information may still be gleaned from these results.

For example, the fact that approximately 40% of these reexaminations resulted in invalidation of at least one claim suggests that there is a significant probability that reexamination will simplify at least some issues in the litigation.

Similarly, approximately 32% of these reexaminations resulted in either new claims or amended claims, suggesting that there is a significant probability that reexamination will alter parties’ litigation positions (e.g., for claim construction). For example, because claim amendments and additions generally narrow the claims, alleged infringers may have the ability to argue new noninfringement arguments. Further, any amended or added claims may be subject to intervening rights that greatly affect damages calculations.

Finally, our data shows that at least one claim was canceled or changed (i.e., added or amended) in over 62% of reexaminations. Accordingly, given the high likelihood of claim changes, a stay of district court proceedings in light of pending reexamination proceedings would likely benefit all parties by preventing the unnecessary expenditure of resources on litigating claims that will likely at least be changed in scope (if not canceled entirely).

Appeals

During reexaminations, a patent owner who “is dissatisfied with the primary examiner’s decision to reject claims in an ex parte reexamination proceeding may appeal to the Board for review of the examiner’s rejection by filing a notice of appeal within the required time.” This must be a final rejection of the claims by the examiner (e.g., a final office action). Third-party requesters may not appeal and may not participate in the appeal. And “[t]he reexamination statute does not provide for review of a patentability decision favoring the patentee.”

A patent owner who wishes to appeal must file the notice of appeal within the period for response to the examiner’s final office action (typically, two months). The patent owner then has two months from the date of the appeal to file an appeal brief. Next, the examiner has a specified period of time (set by the director) in which they may file an answer. The patent owner then receives an opportunity to reply to the examiner’s answer. The examiner’s answer may propose a new ground of rejection. In such cases, the applicant is given the opportunity to reopen the prosecution or may maintain the appeal.

Assuming the appeal continues, the patent owner may request an oral hearing within two months of the date of the examiner’s answer. After consideration of the record, including the appellant’s briefs and the examiner’s answers, the PTAB’s decision will either affirm the examiner in whole or in part, reverse the examiner’s decision, or sometimes set forth a new ground of rejection.

If a patent owner is not satisfied with the decision of the PTAB, they may appeal the PTAB’s decision to the Federal Circuit. As with appeals to the PTAB, the third-party requester may not seek judicial review nor participate in the appeal.

Looking at reexaminations of litigated patents (including still-pending reexaminations), approximately 18% of the 864 reexaminations filed between January 2015 and July 2022 involved a patent owner appeal to the PTAB. Approximately 50% (i.e., 25th percentile to 75th percentile) of these reexaminations without any appeal terminated between 309 and 599.25 days (median 424.5 days or 13.6 months) of being filed. For reexaminations with appeals, the pendency jumps to 834.5 to 1319.5 days (median 985 days or 32.4 months) of filing for the same range.

Of the 591 completed reexaminations (e.g., excluding still-pending reexaminations), there were 70 appeals, or about 12% of completed reexaminations (see table 3). And of those reexaminations, only 14 (or 20% of appealed reexaminations) were appealed to the Federal Circuit—i.e., only 2% of completed reexaminations involved a Federal Circuit appeal.

For completed reexaminations that involved an appeal, at least one claim was invalidated (canceled or disclaimed) in 64% of appealed reexaminations, while at least one claim was confirmed in 37% of appealed reexaminations. Patent owners were successful in amending claims in about 14% of appealed reexaminations and adding claims in about 19% of appealed reexaminations. With respect to Federal Circuit appeals, the Federal Circuit affirmed an examiner’s rejection of claims nearly 100% of the time (13 out of 14, or 92%).

Appealing a reexamination more than doubles the pendency (see table 4). Typically, litigated reexaminations that are not appealed last around 13.22 months. In contrast, the pendency of appealed reexaminations that involve litigated patents jumps to 32.35 months. Because the notice of intent to issue a reexamination certificate typically issues about a month before the reexamination certificate itself, the pendency times may be reduced by a month, which leads to an average nonappealed reexamination pendency of 12.22 months and an average appealed reexamination pendency of 31.35 months.

Our analysis reveals that examiners filed an answer in 71% of appeals. However, in the 29% of cases where the examiner did not file an answer, it does not necessarily mean that the examiner simply gave up. For example, in some cases, the examiner will issue a new ground of rejection. In other cases, the patent owner failed to appear, and thus an answer from the examiner was not necessitated. This occurs in about 16% of appeals. Failure to appear on the part of the patent owner includes failing to file an appeal brief after filing a notice of appeal, filing defective notices of appeal, withdrawing appeals, or failing to respond to new arguments. Our analysis shows that the examiner issued a notice of allowance after an appeal brief (without filing an answer) in only 8% of appeals.

Settlement

Once filed, reexaminations cannot be withdrawn, abandoned, or struck. Because of this, many would-be reexamination requesters are hesitant to file reexaminations, reasoning that because a reexamination cannot be settled, a corresponding case will not settle while a reexamination is pending. Instead, they may opt for IPRs, which can be terminated based on settlement between the parties.

Our study shows that 60% of patent litigations with at least one corresponding reexamination settled while the reexamination was pending (see table 5). Meanwhile about 75% of district court patent cases settle. Thus, the present study indicates that reexamination may only slightly deter district court settlements. And, as will be discussed below, this is much higher than the approximately 28% settlement rate for IPRs.

Further, our study shows that when considering settlements of a district court case that closely followed the termination of a reexamination proceeding (e.g., within six months), the settlement rate is almost equal to that of typical district court settlements. For example, for litigations involving reexamination, 38% of the cases settled within six months of termination of the reexamination, whereas 62% of cases settled more than six months after termination of the reexamination, bringing the settlement rate for reexaminations up to 72%. This generally supports the notion that reexaminations both help to narrow the issues in dispute and help parties reassess the relative strengths and weaknesses of their litigation positions.

In calculating our reexamination settlement data, we only looked at cases that involved completed reexaminations that had been ordered and completed lawsuits. In other words, if a reexamination was still pending during the time frame of January 1, 2015, to July 31, 2022, but the lawsuit terminated, then it was not included in the dataset. Similarly, during this same time frame, if a reexamination had terminated but the lawsuit was still pending, it was also not included. Finally, if a reexamination resulted in a denial (i.e., no SNQ was found and reexamination was not ordered), the reexamination and corresponding lawsuit were excluded from the dataset. We also excluded lawsuits from the dataset where the resolution was a transfer, stay, or consolidation.

Patent Owner Types

The study also analyzed reexamination outcomes based on patent owner type (see table 6). Nonpracticing entities (NPEs) comprise nearly half of litigated reexaminations (46.43%). The remaining patent owner types are a mix of large operating companies (21.39%), small or medium-sized entities (30.27%), and government entities or universities (1.90%).

Of these patent owner types, NPEs had the highest rate of canceled claims (47.10%) and lowest rate of changed (i.e., amended or added) claims (24.23%). The low amendment rate may be attributed to the fact that NPEs are highly motivated to keep litigation costs low to maximize return on investment in patent assertion campaigns, though the higher cancellation rate could suggest lower quality patents. However, it is worth noting that NPEs still had at least some claims confirmed in about 51% of reexaminations.

Large operating companies, on the other hand, had the highest rate of confirmed claims (62.22%) and the lowest rate of cancellations (25.93%). One reason for this may be that large operating companies often have the funds needed to pay for skilled lawyers and are generally known to be sophisticated in litigation. This could also suggest that large operating companies hold and assert patents of higher quality. Interestingly, large operating companies had only a slightly higher rate of changes to claims than NPEs (25.19%).

Assertions After Reexamination

Despite the increased potential for claim amendments and/or additions during reexamination, the data indicates that patents that complete reexamination are only (re)asserted in district court litigation approximately 22.4% of the time (124 out of 554 distinct patents). Of these 124 patents, 43 patents completed at least one reexamination before any district court litigation was filed. In such instances, it is likely that reexamination was conducted either at the patent owner’s request (e.g., to strengthen the patent for an anticipated campaign) or by a third party that had received a presuit demand. Most often, however, a reexamination will not terminate until sometime after litigation has commenced (i.e., a defendant typically will not file a request for reexamination until the patent owner brings suit). For patents in those cases where the reexamination did not complete until after suit had commenced, only 14.6% of patents (81 out of 554) were reasserted after reexamination terminated.

However, in 77.4% of the instances where a patent owner chose to reassert (or assert for the first time) a patent after reexamination terminated, the patent owner did so in multiple litigations (96 out of 124 litigated, reexamined patents). Moreover, out of the 124 patents that were asserted after reexamination, 59 (47.6%) were NPE-controlled, 21 (16.9%) were held by large operating companies, 39 (31.5%) were held by small or medium-sized enterprises, and 5 (4.0%) were held by government entities or universities.

Comparison to Inter Partes Review

We compared outcomes for reexaminations to IPRs (see table 7). Looking only at IPRs that reached an institution decision (i.e., IPRs that were settled or otherwise did not reach institution were excluded), IPRs have a 64.07% institution rate, compared to the much higher 95.40% SNQ grant rate of reexaminations. This difference likely reflects the different standards required to order a reexamination proceeding (requiring a finding of an SNQ) compared to an IPR proceeding, which has a slightly higher standard of demonstrating that there is a “reasonable likelihood” that the petitioner would prevail as to at least one of the challenged claims.

IPRs only have a slightly higher success rate in canceling claims at final written decision (45.56%) compared to the rate of canceling claims in reexaminations (40.25%). This is particularly notable considering the slightly shorter pendency period of reexaminations. As previously discussed with regard to reexamination pendency, reexaminations resolve on average about three months more quickly than IPRs.

Regarding changes to claims, only about 10% of IPRs even include a motion to amend, and only about 16% of those motions to amend were granted or granted in part. Accordingly, at least one claim is amended in less than 1% of IPRs. Unsurprisingly, reexaminations have a higher rate of changes to claims (i.e., amendments or additions) than IPRs, with 32% of reexaminations having an amendment (or added claim). And, as discussed above, while changes to claims do not provide the full benefits that claim cancelation provides, they do offer alleged infringers several benefits.

With respect to settlements, as noted above, would-be reexamination requesters are often hesitant to file reexaminations due to a perceived negative impact on settlement, opting instead to file IPR proceedings, which can be terminated based on settlement. Despite the logical rationale in opting for an IPR over a reexamination to further settlement, available data actually shows that IPRs may deter settlements. For example, there is a 75.32% settlement rate for patent litigations generally, while only 27.90% of lawsuits settled during an IPR proceeding. In contrast, about 60.02% of lawsuits settled during a reexamination proceeding. Thus, even though reexaminations may slightly deter district court settlements, they do not do so to the same extent as IPRs.

One notable difference between reexamination and IPR proceedings is the cost associated with filing a request or petition. The fee for filing a petition for IPR (of up to 20 claims and 14,000 words) is $19,000, and the USPTO has recently proposed increasing that cost to $23,750. And with the additional fees associated with claims in excess of 20, additional words, and post-institution fees, that number can increase to well over $30,000. Moreover, this number does not include the cost associated with the preparation of the petition and any further participation in the proceeding (e.g., additional briefing, depositions, and oral argument), which some estimate to be over $300,000 (and more if there is an appeal to the Federal Circuit).

In stark contrast, the fee for filing a request for ex parte reexamination (with no limit on number of claims or words) is $12,600 and is only $6,300 for streamlined reexaminations (requests with less than 40 pages that meet other format requirements). Although requests for reexamination will still require costs for preparation, because of the ex parte nature of these proceedings, there are no additional fees associated with the proceeding. Accordingly, ex parte reexaminations are much more cost-effective than IPRs.

Regarding timing, in an IPR, once a filing date has been assigned, the PTAB must issue a decision granting or denying institution within about six months. As set by statute, a final written decision in an IPR proceeding must issue within one year of the institution decision. The statute provides a six-month extension to this for good cause. Accordingly, assuming the institution decision issues about six months after the petition was filed, a petitioner can be confident that there will be a final decision with respect to their IPR around 18 months of filing the petition.

It will be no surprise that a requester in a reexamination will have less certainty on the length of the proceeding than a petitioner in an IPR. Though there are similar deadlines in the initial stages of a reexamination to the deadlines in an IPR, the deadlines during the later stages are less certain. What may come as a surprise is that, as addressed above, the average pendency of reexaminations for litigated patents is about 15.33 months—almost three months shorter than for IPRs. Further, our study shows that when excluding appeals, that number drops almost five months, with reexaminations resolving in 13.22 months when they are not appealed. While it has long been understood that reexaminations receive priority and are conducted with “special dispatch,” there has been little to no previous reporting on how this special status translates to overall pendency of reexamination proceedings. Although reexaminations carry the potential for longer proceedings than the relatively quick IPRs, the data shows that reexaminations are faster still—particularly when the patent is asserted in district court.

Our study also shows that the shorter pendency of reexaminations often (though, not always) holds through appeals. IPRs and reexaminations have some important differences when it comes to appeals. For example, in an IPR, both parties may appeal, while in a reexamination, only the patent owner may appeal. Additionally, in a reexamination, the patent owner may only appeal to the Federal Circuit after an appeal to the PTAB. However, in an IPR, parties are not required to appeal to the PTAB prior to appealing to the Federal Circuit. Given these differences, a comparison of the appeals process is not exact. However, for the purposes of this study, we compared a request for rehearing in an IPR to an appeal to the PTAB in a reexamination proceeding, and we compared an appeal to the Federal Circuit in a reexamination to an appeal to the Federal Circuit in an IPR.

The study shows that appeals to the PTAB in reexaminations generally last longer (resulting in a cumulative pendency of 27.33 months compared to 22.1 months for IPRs) and occur slightly more frequently than requests for rehearing in IPRs (11.84% in reexaminations compared to 7.51% in IPR proceedings). However, appeals to the Federal Circuit very rarely occur in reexamination proceedings (about 2% of reexaminations). In contrast, about 60% of IPRs are appealed to the Federal Circuit, which extends the pendency of IPR proceedings to 34.8 months. Practically speaking, it is unsurprising that there is a higher rate of Federal Circuit appeals in IPRs than reexaminations given the differences between the reexamination and IPR appellate processes—i.e., reexamination appeals are heard by the PTAB, whereas IPR appeals are heard by the Federal Circuit. Nevertheless, these differences should not be overlooked as both the frequency of appeal and the speed with which the reviewing tribunal resolves such appeals greatly affect the pendency of the case, which is confirmed by the results above. Thus, while there is a slightly higher chance that a reexamination will be appealed to the PTAB, there is a much greater chance that an IPR will be appealed to the Federal Circuit, which takes much longer to resolve than an appeal to the PTAB during reexamination.

Practical Guidance

Based on the foregoing data, there are several factors that a potential challenger should consider before filing a reexamination request.

First and foremost, a potential requester must understand that, unlike IPR, it will not be able to participate in the proceedings after the petition is filed. Although rare exceptions can occur (e.g., an opportunity to reply to a patent owner statement or submit certain papers from related district court litigation), generally the requester should not assume it will have an opportunity to rebut the patent owner’s arguments in the reexamination itself.

Another trade-off is the pace of a reexamination proceeding, which provides several benefits. For example, reexaminations have a higher rate of initial approval (i.e., finding of an SNQ and ordering a reexamination) than IPRs (i.e., institution decisions). Thus, a reexamination requester will likely know whether the proceeding has been ordered before they would know that an IPR has been instituted, which can be beneficial when requesting a stay of district court proceedings. Further, with respect to litigated patents, these proceedings tend to be resolved more quickly than IPR proceedings.

However, the relative ease of obtaining examiner institution should be carefully weighed against the risk of amendment or addition of claims in a reexamination, which is significantly higher than the rate of amendments in IPRs. This risk of amendment can be avoided by challenging only expired patents (which cannot be amended) in reexaminations.

Additionally, in contrast to IPRs where a patent owner has multiple rounds of briefing to present arguments, reexamination generally requires that the patent owner develop any arguments early in the proceeding. For example, if the patent owner chooses not to file a patent owner statement, the patent owner has only one opportunity (the response to the first office action) to persuade the examiner not to reject a claim or to accept any proposed amendments or claims. This may force the patent owner to take a position earlier in the litigation and allow an accused infringer to identify in advance key areas of dispute (for example, with respect to the patent owner’s view of certain terms for construction).

Third-party requesters should also consider the estoppel differences in the two proceedings. Estoppel generally does not apply to arguments raised in reexamination. Current Federal Circuit precedent regarding IPRs suggests that IPR estoppel under 35 U.S.C. § 315(e)(2) may apply to any ground that a petitioner reasonably could have raised when it filed the petition—not only those grounds that the petitioner actually identified. Thus, a third party may present invalidity grounds in reexamination without fear that similar or related invalidity theories (or even unrelated, to the extent they could have reasonably raised) will not be estopped in district court.

In addition, third-party requesters will have more freedom to file challenges in reexaminations. For example, they are not limited by a word count in a reexamination and thus may present any number of grounds. There are also no issues with multiple filings in reexamination, so third-party requesters may file additional reexamination requests, for example, if they were to find better prior art after filing a first reexamination. In contrast, during an IPR proceeding, the petitioner has a word count that must be adhered to, naturally limiting the number of grounds that may be presented. Additionally, because the PTAB may apply discretion to deny subsequent IPRs against the same patent, petitioners are often generally limited to one filing against a patent.

Reexamination as a Viable Alternative to IPR

The decision whether to use reexamination is highly fact-dependent and must be evaluated on a case-by-case basis—however, this study demonstrates that many of the perceived disadvantages of reexaminations likely have been overstated. For example, ex parte reexaminations are more cost-effective, especially considering the fact that they have almost the same rate of cancellations as IPRs and the fact that they typically reach resolution more quickly than IPRs. Further, when considering the advantages that even changes to claims can present for patent challengers (e.g., narrowing claims through responses to office actions, intervening rights that may arise through claim amendment), the effectiveness of reexaminations becomes even more pronounced. As a result, would-be patent challengers would be well-advised to consider incorporating reexaminations into their defensive strategy, as an IPR is not necessary in each and every scenario and may in fact be less desirable, depending on the challenger’s specific objectives.

Published in Landslide, Volume 17, Number 3, 2025. © 2025 by the American Bar Association. Reproduced with permission. All rights reserved. This information or any portion thereof may not be copied or disseminated in any form or by any means or stored in an electronic database or retrieval system without the express written consent of the American Bar Association.