Ex parte reexaminations have re-emerged as an increasingly important component of patent litigation and licensing negotiations. With the passage of the America Invents Act (AIA) and the advent of inter partes reviews (IPRs) and post grant reviews (PGRs) in 2012, inter partes reexamination were discontinued and ex parte reexamination fell out of favor. Over the last few years IPR institution rates have declined. Ex parte reexamination requests have increased dramatically—often providing a second chance for petitioners who were unsuccessful in IPR proceedings. The esoteric and nuanced reexamination rules and procedures combined with the complex interplay between reexaminations and AIA trials/litigation proceedings raise unique and oftentimes befuddling issues that parties must consider. This article sheds light on these issues, including summarizing the reexamination process and examining estoppel issues associated with establishing a substantial new question (SNQ) of patentability—the limiting function to allow an ex parte reexamination request granted. Lastly, we explore the impact of the recent Vivint US Court of Appeals for the Federal Circuit1 decision that may subject hundreds of ex parte reexaminations that relied on art used in failed IPR petitions to termination.


An ex parte reexamination is a powerful tool for third-party requesters—often defendants in a patent lawsuit—to attack the validity of patent claims without the estoppel risks associated with IPR and PGR proceedings. Patent Owners, on the other hand, can use ex parte reexaminations as a faster alternative to reissue to strengthen their patent claims against invalidity challenges in later or parallel AIA, district court, or US International Trade Commission (ITC) trials. A reexamination request can challenge the validity of one or more claims in the patent on proposed novelty or obviousness grounds based only on patents and other printed publications. Parties can file a reexamination at any time after a patent is granted and up to six years after it expires.

Ex Parte Reexamination Requests, Grant Rates, and Success Rates

After a peak of nearly 800 filings in 2012—the year the AIA came into effect—as expected ex parte reexamination filings steadily declined until 2019, when they took a somewhat unexpected turn. At that time, ex parte reexamination numbers began to rise, and continue to rise today. As shown in Figures 1 and 2, reexamination filings have significantly increased, but remain far below pre-AIA levels.

A surge in reexamination requests following a “failed” AIA challenge accounts for a portion of the overall growth of reexamination filings. As shown in Figure 3, about a third of all such do-over reexaminations were filed in the past two years. Nonetheless, these do-over filings do not fully explain the recent increase in popularity of ex parte reexaminations.

Figure 1: Ex Parte Reexam Requests Last 41 Years

Figure 2: Ex Parte Reexam Requests Since AIA

Figure 3: Reexam Request-PTAB Challenge Status

Figure 4: Ex Parte Reexam Grant Rate