Two Branches, Two Directions: The Patent Office and Federal Circuit's Divergent Approaches to Duplication of Effort in IPRs

The intent of the America Invents Act (AIA) was that inter partes review (IPR) would serve as a cost-effective alternative to district court litigation, not a supplement to it. For a time, that goal was at least partially achieved. From 2014 to 2025 there were regularly over one thousand IPR’s instituted per year. These IPR’s were often given a broad estoppel effect (in many cases bolstered by Sotera stipulations) such that a significant number of anticipation and obviousness determinations were decided by the Patent Trial and Appeal Board (PTAB) rather than the courts. Recent actions from both the Patent Office and the Federal Circuit, however, are pushing validity determinations back into federal courts.

The Patent Office Embraces Discretionary Denials of IPRs

On May 14, 2026, Patent Office Director John Squires issued a precedential decision in Magnolia Medical Technologies v. Kurin, Inc., IPR 2026-00097, that amounted to a policy statement in defense of frequent, non-merits-based denial of IPR petitions. The Director identified several areas of concern: the filing of multiple petitions, petitions filed after district court or ITC proceedings are already underway where similar art is at issue, and petitions that take positions inconsistent with those advanced in parallel litigation. The Director determined that, in may cases, an IPR was used as an additional validity vehicle rather than an alternative one — which, in his view, simply increases the total cost and burden of patent litigation rather than reducing it.

The Federal Circuit Narrows IPR Estoppel

The IPR statute provides that an IPR petitioner that receives a final written decision may not assert that a patent “is invalid on any ground that the petitioner raised or reasonably could have raised during that inter partes review.” 35 U.S.C. § 315(e)(2). “Reasonably could have raised” has been interpreted to mean that a "skilled searcher exercising reasonable diligence" would have discovered the prior art ground at issue before the IPR petition was filed.

In the Federal Circuit’s recent decision in Ironburg Inventions Ltd. v. Valve Corporation (June 18, 2026), the Court clarified that the patent owner faces a heavy burden in establishing IPR estoppel as to references not at issue in the IPR. The Federal Circuit indicated that a classification search is not sufficient to show that a reference was discoverable where the classification includes a large number of other references. (The USPTO and other patent offices use “classifications” to group patents into technical categories and subcategories.) The Federal Circuit held that “something more is required for estoppel when a classification search alone returns an unreviewable number of search results.” Thus, a patent owner must show that a prior art patent was located in a reasonable classification and that a searcher would have located it using “something more,” such as a narrowing keyword search.

In a concurrence, Judge Stark indicated that a patent owner’s burden does not end with locating the reference in question, rather “the patentee’s burden to show discoverability of invalidity grounds is not automatically satisfied by proving the findability of the prior art reference(s) on which the invalidity ground is based.”

Thus, that a prior art reference is in the public record and properly classified is not enough. The Federal Circuit does not address whether the prior art being located by defendant for assertion at trial suggests that such ground “reasonably could have been raised” at the time the IPR was filed.

A System Working at Cross-Purposes

The combined effect of these two developments is a system that works at cross-purposes with the AIA's goal of efficient, nonduplicative, determination of prior art issues by the Board. If a petition is filed in parallel with district court litigation, the Director is increasingly likely to deny institution. If the petition is instituted and a final written decision is reached, the Federal Circuit's narrow construction of estoppel may permit patent challengers to mount a robust prior art defense in district court anyway. Moreover, instead of a straightforward bar, IPR estoppel will become a time-consuming trial-within-a-trial, including expert testimony on what a hypothetical skilled searcher would or would not have found.

The overall effect of these developments will likely be to move more section 102 and 103 determinations back to federal district court. Any defendant who does get an IPR instituted will still have a range of prior art available for assertion at trial.