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In response to a lawsuit for patent infringement, often a defendant will file an inter partes review (IPR) challenging the validity of the asserted claims. How can a patentee avoid this scenario? The Court of Appeals for the Federal Circuit recently approved of a method that allows a patentee to potentially sacrifice a subset of a patent’s claims to avoid an IPR challenge to the remaining claims.

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Here’s the scenario: a patentee sues a defendant and asserts infringement of a subset of a patent’s claims. The defendant has one year to file an IPR. Within that year, the defendant files an IPR challenging the asserted claims. However, after the one-year IPR filing deadline expires, the patentee amends the complaint to assert infringement of additional claims from the same patent. At this point, the defendant is unable to challenge the newly asserted claims via an IPR.

In this scenario, the PTAB invalidated the subset of the patent’s claims. The defendant argued that given the similarity between the invalidated claims and newly asserted claims, the invalidated claims should collaterally estop the plaintiff from alleging infringement of the newly asserted claims. There is Federal Circuit precedent that holds that collateral estoppel may apply to patent claims that were not previously adjudicated as invalid if the differences between the unadjudicated claims and the adjudicated claims “do not materially alter the question of invalidity.”<a href="#_ftn1" id="_ftnref1">[1]</a>

However, in a precedential decision in Kroy IP Holdings, LLC v. Groupon, Inc., No. 2023-1359 (Fed. Cir. Feb. 10, 2025),<a href="#_ftn2" id="_ftnref2">[2]</a> the Federal Circuit addressed this exact scenario and concluded that collateral estoppel did not apply to the newly asserted claims.

Collateral estoppel does apply to the claims invalidated in an IPR and then asserted in district court because “once a claim is already and finally held unpatentable as a result of an IPR, the claim is subject to a wholly ministerial, inevitable, unreversible cancellation.” But those same invalidated claims cannot collaterally estop the newly asserted claims. This is because the invalidated claims were rendered invalid under a standard of proof lower than the clear and convincing evidence standard that is required in district court: “a prior final written decision of the Board of unpatentability on separate patent claims reached under a preponderance of the evidence standard cannot collaterally estop a patentee from asserting other, unadjudicated patent claims in district court litigation.” Collateral estoppel could apply to newly asserted claims if the previous claims had been found invalid in court using the clear and convincing evidence standard.

The result of this decision is that the patentee is incentivized to delay asserting a subset of a patent’s claims until after the one-year IPR filing deadline passes. A defendant can attempt to avoid this scenario by challenging in an IPR all claims, or at least all claims that a patentee could potentially assert as infringing, rather than challenging only the original asserted claims.

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<a href="#_ftnref1" id="_ftn1">[1]</a> Ohio Willow Wood Co. v. Alps South, LLC, 735 F.3d 1333, 1342 (Fed. Cir. 2013).

<a href="#_ftnref2" id="_ftn2">[2]</a> Available at <a href="https://www.cafc.uscourts.gov/opinions-orders/23-1359.OPINION.2-10-2025_2465811.pdf">https://www.cafc.uscourts.gov/opinions-orders/23-1359.OPINION.2-10-2025_2465811.pdf</a>.

Challenging a Patent via an IPR? Patentees Have an Approved Method to Mitigate the Impact