The United States Court of Appeals for the Federal Circuit clarified in Shockwave Medical, Inc. v. Cardiovascular Sys., Inc.1 how Applicant Admitted Prior Art (AAPA) fits into inter partes review (IPR) practice. In response, the United States Patent and Trademark Office issued a memorandum that narrows the use of AAPA in IPR petitions. The USPTO explained that while AAPA can still be used in a limited way for background information and to show motivation to combine references, it can no longer be used to supply a claim limitation missing from the prior art patents and printed publications raised by the petitioner.
The Shockwave Decision
Shockwave's patent relates to a catheter system that uses intravascular lithotripsy to break down arterial plaque. Cardiovascular Systems challenged validity of the claims in a petition for IPR. In its obviousness presentation, the petitioner relied in part on a European Patent Publication combined with admissions in Shockwave's own patent about over-the-wire balloon catheters. Shockwave's AAPA states that "typical prior art over-the-wire angioplasty balloon catheters[s] . . . are usually non-compliant with a fixed maximum dimension when expanded with a fluid such as saline."
The main legal issue in the appeal was whether AAPA could serve as the basis for the IPR challenge. More specifically, the question was whether the patentee's own statements in the patent specification could be relied on to show the existence of an element or limitation of a claim challenged as being invalid for obviousness. Under 35 U.S.C. § 311(b), an IPR petition may only be based on patents and printed publications. AAPA is not one of these categories. The Federal Circuit relied on its earlier Qualcomm I and Qualcomm II precedents, holding that AAPA cannot be the "basis" of an IPR petition but can still play a supporting role in the challenge.
Some background is potentially helpful in understanding the distinction. In Qualcomm I, the court held that AAPA cannot be the basis of a petition in IPR and remanded the case to the Patent Trial and Appeal Board (PTAB) to determine whether AAPA had in fact formed the basis of the petition. On remand, the PTAB concluded that AAPA does not form the basis of a ground in violation of § 311(b) if the ground relies on AAPA "in combination with" permissible prior art patents or printed publications. On this reasoning, the PTAB held that a petitioner's reliance on AAPA for disclosure of a claim limitation not otherwise found in the prior art was permissible. However, in Qualcomm II, while the Federal Circuit acknowledged the PTAB's reasoning, it nonetheless reversed the PTAB's decision because the IPR petitioner had expressly labeled AAPA as part of its "basis" for the obviousness ground.
One might reasonably view the Qualcomm I and II decisions as exalting form over substance, with the outcome depending on how the IPR petitioner labeled its argument rather than what it actually argued. Nonetheless, in Shockwave the court reaffirmed its Qualcomm I and Qualcomm II decisions explaining that AAPA may be used only as evidence of background knowledge, and to show motivation to combine references, and even to supply a missing claim limitation if that limitation reflects knowledge already common in the art – so long as the petitioner doesn't say that the AAPA is part of the "basis" of its validity challenge.
The petitioner in Shockwave used AAPA only to show that a conventional angioplasty balloon catheter was well known, not as the anchor of the obviousness challenge. That distinction mattered. The Federal Circuit held that such use of AAPA was valid because it provided context rather than serving as the foundation of the obviousness ground. By contrast, in Qualcomm II, the IPR petition expressly designated the AAPA as a "basis" of the obviousness ground, which crossed the line. While the label obviously matters at least to the court, practitioners may conclude that the substantive distinction is harder to see.
The court in Shockwave also emphasized that the scope of AAPA's use must be judged by the petition itself, not by the PTAB's final written decision. In contrast to Qualcomm II where the petitioner had expressly listed AAPA as part of its basis, in Shockwave the petition did not indicate AAPA as its "basis." Put differently, what matters is how the petitioner framed its reliance on AAPA in the petition, not whether the PTAB's final written decision indicates that AAPA was, nonetheless, a basis of the obviousness challenge.
The USPTO Director's Memo: Narrowing the Use of AAPA
Against this backdrop, the USPTO responded quickly. In a July 31, 2025 memorandum, Acting Director Coke Morgan Stewart announced that the Office will strictly enforce 37 C.F.R. § 42.104(b)(4) going forward.2 This rule requires IPR petitions to specify where each claim element is found only in patents or printed publications. The memo explains:
"Enforcement of Rule 104(b)(4) means that applicant admitted prior art (AAPA), expert testimony, common sense, and other evidence that is not 'prior art consisting of patents or printed publications' (collectively, 'general knowledge') may not be used to supply a missing claim limitation. General knowledge may still be used in an IPR to support a motivation to combine or to demonstrate the knowledge of a person having ordinary skill in the art."
In practice, this bars petitioners from relying on AAPA, expert testimony, or common sense to fill a missing claim element. AAPA can still be used for motivation to combine or to show the knowledge of a person having ordinary skill in the art, but nothing more.
This marks a significant change. While Federal Circuit precedent allows AAPA to be used even for missing limitations when those reflect general knowledge, the USPTO has now cut off that use in IPR proceedings. The memo replaces earlier guidance that permitted limited reliance on AAPA and adopts a stricter rule: only patents and printed publications can establish prior art disclosure of a claim element.
According to the USPTO, this approach reduces the risk of further litigation over AAPA at the Federal Circuit. The memo explains that enforcing Rule 104(b)(4) will create clarity by ensuring that petitions clearly identify their legal and factual bases and that patent owners receive proper notice of the grounds being raised. On the other hand, there was no dispute in any of Qualcomm I, Qualcomm II, and Shockwave regarding what grounds were being raised, or the legal and factual bases for the IPR petitioners' grounds in those proceedings. Whether the Federal Circuit will uphold or overrule the USPTO's interpretation and application of 37 C.F.R. § 42.104(b)(4) is unknown.
The change applies to IPR petitions filed on or after September 1, 2025.
Footnotes
1. 142 F.4th 1371 (Fed. Cir. 2025).
2 chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.uspto.gov/sites/default/files/documents/aapa_memo_final__signed.pdf?utm_campaign=subscriptioncenter&utm_medium=email&utm_source=govdelivery
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