Federal Circuit Affirms Broad Functional Language Render Brita’s Patent Invalid Under §112(a)

In Brita LP v. ITC, No. 2024-1098 (Fed. Cir. Oct. 15, 2025), the Federal Circuit affirmed the Commission’s determinations that certain asserted claims of Brita’s patent lack written description support and are not enabled for any filter other than carbon-block filters.

Brita sought to enforce U.S. Patent No. 8,167,141 (’the 141 patent), generally directed to gravity-flow fluid filtration systems. The Commission found that carbon-block filters were the only type enabled and sufficiently described by the patent. Brita appealed the ITC’s findings.

Brita argued the ’141 patent has written description support for non-carbon-block filters based on the claims themselves and the specification’s examples of other filters and broad statements of applicability. The Court disagreed. Specifically, the Court held that the broad functional language used in the ’141 patent—a filter meeting an internally defined performance criterion—must be read in light of the specification. Reviewing the specification, along with testimony of experts and the ’141 patent’s inventors, the Court agreed with the Commission that the complexity of the performance criterion and absence of functional examples of non-carbon-block filters meant there was no written description support for non-carbon-block filters.

The Court further affirmed the Commission’s findings on enablement, citing similar grounds as for written description. It analyzed the Wands factors and affirmed the Commission, finding that making filters within the scope of the ’141 patent’s claims is an unpredictable art, so the knowledge of the skilled artisan could not make up for the lack of functional examples.