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Federal Circuit Affirms The ITC’s Finding Of Invalidity Of Water-Filter Patent
11/04/2025In Brita LP v. Int’l Trade Comm’n, No. 24-1098 (Fed. Cir. Oct. 15, 2025), the Federal Circuit, in a precedential opinion, affirmed the International Trade Commission’s (“ITC” or “Commission”) decision that certain claims of U.S. Patent No. 8,167,141 (“the ’141 patent”) are invalid for lack of written description and lack of enablement. The appeal was brought by Brita LP, the complainant before the Commission. Vestergaard Frandsen Inc. d/b/a LifeStraw, KAZ USA, Inc., and Helen of Troy Limited, the respondents in the ITC investigation below, intervened.
The ’141 patent concerns gravity-fed water filters that remove contaminants and claims a “filter media including at least activated carbon and a lead scavenger” that achieves a “Filter Rate and Performance (FRAP) factor of about 350 or less” calculated under a specified formula. Although the patent lists several types of filter media—such as carbon blocks, mixed media, membranes, nonwovens, depth media, nanoparticles and nanofibers, and ligands—the only filter the specification actually shows as meeting the claimed FRAP factor is a carbon-block filter.
The Federal Circuit held that substantial evidence supported the Commission’s finding that the claims lack adequate written description for any non–carbon-block filter that satisfies the FRAP limitation. In reaching its conclusion, the Court found that the claims were defined functionally. Furthermore, the Court considered disclosures in the patent showing that, of all the different filters tested, only carbon blocks could meet the claimed FRAP factor. The Court additionally emphasized the specification’s focus on the use of carbon blocks to meet the claimed FRAP factor, including that: all of the figures depicted carbon blocks; the examples only described specific formulations of carbon block filters; and the specification distinguished carbon blocks from other types of filters.
The Court also found that expert and inventor testimony supported the Commission’s determination. This included inventor testimony that they did not invent any non-carbon-block filters that would meet the claimed FRAP factor, as well as expert testimony that the variables in the FRAP formula were interrelated and that changing one variable could result in unpredictable changes in others.
The Court also rejected Brita’s arguments that the original claims themselves supplied sufficient written description; that generic statements in the specification that the invention is “applicable to all embodiments” constituted a constructive reduction to practice; and that the patent disclosed representative species or common structural features across the claimed media. The Court found that the original claims and general specification statements did not provide any meaningful disclosure related to the FRAP factor limitations, and that the patent specification disclosed no species other than carbon blocks that met the FRAP factor.
Separately, the Federal Circuit also affirmed the Commission’s enablement ruling. The Court credited the Commission with analyzing each of the Wands factors in reaching its conclusion and found that much of the same evidence relevant to written description also supported the Commission’s findings regarding enablement. This Federal Circuit decision, along with others that have issued since the Supreme Court’s decision in Amgen v. Sanofi, continues to clarify the written description and enablement requirements.
