Patent Invalidity, Reexamination and Post Grant Review

For more than a decade, the most prevalent way to attack a patent outside of court has been the “inter partes review” (IPR) provided by the America Invents Act in 2012. That is changing quickly. As the USPTO has issued an increasing number of discretionary denials – refusing to institute an IPR without ever reaching the merits of the challenge – petitioners have gone back to the older and much less glamorous ex parte reexamination. The numbers are striking. According to Unified Patents’ Patent Dispute Report for the first half of 2026, IPR petitions fell to an all-time quarterly low of 57 in the second quarter of 2026, down 83.8 percent from the same quarter in 2025, while requests for ex parte reexamination hit an all-time quarterly high of 336, up 148.9 percent year over year. Across the first half of 2026, there were 594 reexamination requests compared to 226 a year earlier. Ex parte reexamination went from 23.6 percent of post-grant filings in the first half of 2025 to 74.7 percent in the first half of 2026, while IPRs fell from 72.9 percent to 21.9 percent. A copy of the report can be obtained here:

For patent owners, this is good news. The most important reason is that the challenger largely disappears from the proceeding. A reexamination request opens the door, but the requester’s participation ends early in the process. The patent owner has the option of filing a statement after reexamination is ordered, and only if it does may the requester file a single reply. Once office actions are issued, only the patent owner and the examiner are involved, which is a very different experience from an IPR, where a well-funded adversary files expert declarations, takes depositions, replies to everything the patent owner says, and argues to a panel at an oral hearing.

The second benefit for patent owners is easy to overlook: it is considerably easier to amend the claims in a reexamination than in an IPR. In a reexamination, the patent owner may make narrowing amendments to distinguish the prior art as part of the ordinary give and take of prosecution. An IPR works nothing like that. There, the patent owner cannot simply amend. It must file a motion to amend, it may file only one such motion, it must confer with the Board before filing, and the motion can be denied outright if the amendment “does not respond to a ground of unpatentability involved in the trial.” 35 USC 316(d). 

There is one downside for the patent owner in an ex parte reexamination: no estoppel for the requester. When an IPR runs to a final written decision, the petitioner is barred from raising in court any ground it raised or reasonably could have raised. In contrast, a requester whose reexamination effort is unsuccessful can turn around and assert the very same prior art as an invalidity defense in the infringement suit. However, overall, the reduced availability of IPRs is certainly a welcome development for patent owners who are seeking to enforce their patents.