A newly filed opposition in IPR2025-00677 puts a familiar but strategically important PTAB issue front and center: whether a patent owner’s proposed substitute claims can survive scrutiny when offered through a contingent motion to amend. In its April 7, 2026 filing, the petitioner asks the Patent Trial and Appeal Board to deny the patent owner’s amendment request, arguing that the revised claims still do not satisfy the governing patentability and procedural standards.

A contingent motion to amend is exactly what it sounds like: the patent owner proposes substitute claims only if the Board finds the original claims unpatentable. These motions have become a critical pressure point in inter partes review practice because they can reshape the case late in the proceeding, preserve some patent coverage for the owner, and force the petitioner to attack not just the issued claims but a second, newly drafted claim set.

Although the specifics of the substitute claims matter, oppositions to these motions usually make several core arguments, and this filing appears to fit that pattern. Petitioners commonly contend that the proposed claims are still unpatentable over the prior art, are obvious in light of combinations already in the record, or fail for written description or enablement reasons if the patent owner has added narrowing language not adequately supported by the original specification. Procedurally, petitioners also often argue that the amendment improperly enlarges claim scope, introduces new issues too late, or does not clearly respond to a ground of unpatentability raised in the petition.

The broader context is important. Since the PTAB’s amendment framework evolved to make motions to amend more viable, these disputes have become much more consequential. A patent owner that loses on the original claims may still salvage meaningful protection through substitute claims. For petitioners, that means “winning” the IPR on instituted claims may not end the risk if replacement claims emerge with litigation value. For patent owners, the motion to amend is no longer a longshot formality; it is often a parallel merits battle requiring its own expert support, claim drafting discipline, and prior-art analysis.

Litigators should pay attention because these filings reveal how parties are adapting to PTAB practice in real time. They offer a roadmap for attacking or defending substitute claims, preserving invalidity positions for parallel district court disputes, and managing estoppel exposure. They also underscore a practical lesson: in modern IPRs, amendment strategy is often as important as the original petition.

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