The US District Court for the Northern District of Iowa issued an instructive decision clarifying the scope of statutory estoppel under the Leahy-Smith America Invents Act (AIA) following post-grant review (PGR) proceedings before the Patent Trial & Appeal Board. Intirion Corp. v. College Products, Inc., Case No. 23-cv-4023-CJW-KEM (N.D. Iowa Sept. 16, 2025) (Williams, J.)

Intirion brought a patent infringement suit against College Products, which responded by petitioning the Board for PGR, challenging the patents based on obviousness and indefiniteness. While the PGR was pending, the district court proceeded with claim construction and initially found the terms “level of smoke,” “amount of smoke,” and “dangerous condition” indefinite. Intirion moved for reconsideration, and College Products filed a motion for partial summary judgment asserting invalidity. Intirion also sought a stay of the litigation pending the PGR outcome, which the court granted.

The Board instituted review of all claims. Initially, it found that neither party had requested express construction of any terms and adopted Intirion’s interpretation that “level of smoke” and “amount of smoke” meant “merely detecting smoke,” based on Intirion’s representations in the district court. In its final written decision (FWD), the Board acknowledged the district court’s indefiniteness findings but ultimately adopted the plain and ordinary meaning of the terms, concluding that a person of ordinary skill in the art could determine appropriate thresholds using known methods. Expert testimony persuaded the Board that defining the terms by their function was sufficiently definite under patent law.

After the Board upheld the claims, the district court found that College Products was estopped under 35 U.S.C. §325(e)(2) from asserting any invalidity grounds (including indefiniteness and obviousness) that were or reasonably could have been raised during the PGR. The district court explained that the AIA established a streamlined system allowing third parties to challenge the patentability of issued claims before the Board as a quicker and more cost-effective alternative to litigation. This structure is specifically designed to prevent challengers from getting multiple bites at the apple by raising the same or similar arguments in subsequent court proceedings.

College Products argued that estoppel should not apply because it filed its motion for partial summary judgment before the Board issued its FWD. The district court rejected this argument, explaining that the statutory language provides no exception based on timing and imposes a clear bar once the Board has issued a FWD. The district court also found that College Products’ position was inconsistent with applicable case law and noted that it failed to cite any contrary authority.

The district court further explained that it had intentionally deferred ruling on College Products’ motion for partial summary judgment of invalidity pending the outcome of the PGR proceedings. Once the PTAB issued its FWDs, College Products was estopped from further challenging the validity of the patents, including through its pending summary judgment motion, because it could have raised any such indefiniteness arguments during the PGR process.

Practice note: Unlike inter partes review (IPR), during PGR a petitioner can challenge patentability on grounds [...]

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