Brita Lp v. International Trade Commission

United States Court of Appeals
for the Federal Circuit
______________________
BRITA LP,
Appellant
v.
INTERNATIONAL TRADE COMMISSION,
Appellee
VESTERGAARD FRANDSEN INC., D/B/A
LIFESTRAW, KAZ USA, INC., HELEN OF TROY
LIMITED,
Intervenors
______________________
2024-1098
______________________
Appeal from the United States International Trade
Commission in Investigation No. 337-TA-1294.
______________________
Decided: October 15, 2025
______________________
D EANNE MAYNARD, Morrison & Foerster LLP, Wash-
ington, DC, argued for appellant. Also represented by
S ETH W. LLOYD; PAUL ASHLEY AINSWORTH , Sterne Kessler
Goldstein & Fox PLLC, Washington, DC.
PANYIN H UGHES, Office of the General Counsel, United
States International Trade Commission, Washington, DC,
argued for appellee. Also represented by H OUDA M ORAD.
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BRITA LP v. ITC 2
ADAM S WAIN, Alston & Bird LLP, Washington, DC, ar-
gued for all intervenors. Intervenors KAZ USA, Inc., Helen
of Troy Limited also represented by THOMAS WILLIAM
D AVISON; KIRK T. BRADLEY , KARLEE N. W ROBLEWSKI, Char-
lotte, NC; KATHERINE RUBSCHLAGER, San Francisco, CA.
JEFFREY R. GARGANO, K&L Gates LLP, Chicago, IL, for
intervenor Vestergaard Frandsen Inc. Also represented by
D EVON C. BEANE , Alston & Bird LLP, Chicago, IL.
______________________
Before PROST, REYNA , and CHEN, Circuit Judges.
PROST, Circuit Judge.
Brita LP (“Brita”) appeals from a United States Inter-
national Trade Commission (“Commission”) decision deter-
mining claims 1–6 and 23 of U.S. Patent No. 8,167,141
(“the ’141 patent”) invalid for lack of written description,
lack of enablement, and indefiniteness. For the following
reasons, we affirm as to lack of written description and lack
of enablement.
BACKGROUND
I
The ’141 patent is titled “Gravity Flow Filter” and is-
sued on May 1, 2012. ’141 patent Title (capitalization nor-
malized). The application for the ’141 patent was filed as
a continuation-in-part on September 9, 2008 based on sev-
eral other applications, each of which Brita abandoned.
The ’141 patent, similar to its predecessor applications, is
directed to gravity flow fluid filtration systems used for re-
moving contaminants from water. Id. at col. 1 ll. 15–18. It
claims “filter media including at least activated carbon and
a lead scavenger.” Id. at claim 1. Activated carbon is used
“to generally improve the taste and odor of the water,” id.
at col. 1 ll. 58–61, and is typically used together with an
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BRITA LP v. ITC 3
additive to facilitate the removal of heavy metals, such as
lead and copper, id. at col. 3 ll. 51–57. The ’141 patent ex-
plains that activated carbon may be used with a “lead scav-
enger,” which is “for removing lead from water.” Id. at col.
11 ll. 60–65.
The sole independent claim at issue, claim 1, recites:
A gravity-fed water filter, comprising:
filter media including at least activated carbon and
a lead scavenger;
wherein the filter achieves a Filter Rate and Per-
formance (FRAP) factor of about 350 or less accord-
ing to the following formula:
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = [𝑉𝑉 ∗ 𝑓𝑓 ∗ 𝑐𝑐𝑒𝑒]
[𝐿𝐿 ∗ 2]
where:
V=volume of the filter media (cm3),
f=average filtration unit time over lifetime L
(min/liter),
c e=effluent lead concentration at end of lifetime L
when source water having a pH of 8.5 contains 90–
120 ppb (μg/liter) soluble lead and 30–60 ppb (μg/li-
ter) colloidal lead greater than 0.1 μm in diameter,
and
L=filter usage lifetime claimed by a manufacturer
or seller of the filter (gallons).
The ’141 patent identifies various types of filter media,
including carbon blocks, mixed media, membranes,
nonwovens, depth media, nanoparticles and nanofibers,
and ligands. Id. at col. 25 ll. 9–12, col. 26 ll. 30–37. These
filter media have different characteristics and face differ-
ent challenges associated with their use in filtering water.
For example, carbon blocks use activated carbon held to-
gether with a binder, while loose or mixed media use
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BRITA LP v. ITC 4
granular activated carbon packed into a compartment
without a binder. For carbon blocks, “lead-reducing
sorbents” can be blended with the carbon particles and the
binder particles. Id. at col. 2 ll. 38–39, col. 11 ll. 60–65. For
other types of media, an additive, such as ion exchange
resin, can be mixed with carbon to help the filter reduce
lead. Id. at col. 3 ll. 24–38; see also id. at col. 26 ll. 30–34.
One problem with mixed media filters is that “they require
a long contact time to work properly, which limits the flow
rate,” and “they take up a large amount of space inside the
filter.” Id. at col. 3 ll. 51–63; see also id. at col. 3 ll. 64–67
(“A further problem associated with blended media of gran-
ular carbon and ion exchange resin is that they have lim-
ited contaminant removal capability due to particle size
and packing geometry of the granules.”).
The ’141 patent expresses a desire to achieve a suitable
tradeoff of competing requirements for filter performance.
Id. at col. 5 ll.19–20. Achieving the right balance is im-
portant because users “do not want to wait a long time for
the filtered water” and do not want the filter to take up
excessive space in their home. Id. at col. 4 ll. 41–50. At the
same time, a filter should achieve “effective contaminant
removal and long filter life.” Id. at col. 4 ll. 50–56. The
patent explains, however, that adjusting the characteris-
tics of a filter to achieve good filter performance is not
straightforward. For example, configuring a filter to have
a low pressure drop to achieve a fast flowrate is at odds
with the design goals of “effective contaminant removal
and long life.” Id. at col. 4 ll. 52–61. “It would be useful to
have gravity flow filters that exhibit both good water flow
rates and high contaminant reduction.” Id. at col. 5 ll. 19–
20.
The ’141 patent characterizes filters in terms of a per-
formance metric that it calls “Filter Rate and Performance
Factor (FRAP) Factor.” Id. at col. 25 ll. 13–17. “Preferred
filters have a FRAP Factor ranging from 0–350.” Id. at col.
25 ll. 17–19. “The nature of the filter meeting [this]
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BRITA LP v. ITC 5
performance criteria is independent of the exact embodi-
ment of the filter and thus applicable to mixed-media, car-
bon blocks, nonwovens, hollow fibers and other filtration
formats.” Id. at col. 25 ll. 9–12. Claim 1 requires a FRAP
factor “of about 350 or less.” Id. at col. 34 ll. 9–11.
The only type of filter disclosed in the ’141 patent as
meeting the claimed FRAP factor of 350 or less is carbon
block. All of the figures of filters in the patent depict car-
bon blocks, not any other type of filter media. Id. at Figs.
1–20B. The ’141 patent also states:
Several gravity fed carbon blocks and mixed media
filters have been tested for flow rate and lead re-
duction capability against the defined lead chal-
lenge water. Filters tested include several
formulations of carbon blocks along with commer-
cially available mixed media filters produced by
BRITA® and PUR®. Based on the results from
testing, the FRAP factors were calculated for each
filter and reported below. No mixed media filters
tested met the claimed FRAP factor range due to
their inability to remove particulate lead. The for-
mulations of gravity fed carbon blocks disclosed are
unique in [their] ability to meet the required FRAP
factor. The “Examples” below include many exam-
ples of gravity flow carbon blocks that have a FRAP
factor of less than 350. It is not believed that any
currently-marketed gravity-flow filters have a
FRAP factor of less than 350.
Id. at col. 26 l. 55–col. 27 l. 2. The “examples” mentioned
in this paragraph refer to specific formulations of carbon-
block filters provided in the ’141 patent as well as certain
“mixed media filters” identified as “the current BRITA®
gravity-flow mixed media filter, the BRITA® Germany
MAXTRA® gravity-flow mixed media filter, and the Proc-
tor and Gamble PUR® 2-stage gravity-flow filter with
pleated microfilter.” See id. at col. 27 l. 14–col. 33 l. 12.
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BRITA LP v. ITC 6
Various characteristics of carbon-block filters, such as
geometry and chemistry, affect their filtration perfor-
mance. For example, the use of particular formulations of
binders in carbon blocks enables “maximizing the available
surface area of the carbon” which allows for “a carbon block
that is hydrophilic and readily absorbs water.” Id. at
col. 14 ll. 39–41. “Typical carbon block filters” have flow
rates that are “unacceptably slow,” id. at col. 11 ll. 26–31,
but “according to embodiments of the invention,” formula-
tions of carbon blocks could be made having “excellent pres-
sure drop” (and thus, fast flow rate) as a result of the “block
shapes and the porosity and high amount of interstitial
spaces and passages through the solid profile.” Id. at
col. 14 l. 61–col.15 l. 6. The ’141 patent does not disclose
any specific filter formulation using a filter media other
than carbon block that achieves the claimed FRAP factor.
II
On December 27, 2021, Brita filed a complaint with the
Commission under section 337, alleging that various re-
spondents, including Kaz USA, Inc., Helen of Troy Limited,
and Vestergaard Frandsen Inc. (together, “Intervenors”),
imported and sold water filters that infringed various
claims of the ’141 patent. The Commission initiated its in-
vestigation on January 31, 2022.
After a Markman hearing, the administrative law
judge (“ALJ”) construed “filter usage lifetime claimed by a
manufacturer or seller of the filter” to mean “[t]he total
number of gallons of water that a manufacturer or seller
has validated can be filtered before the filter is replaced,”
and rejected respondents’ arguments that the limitation is
indefinite. Certain High-Performance Gravity-Fed Water
Filters & Prods. Containing the Same, Inv. No. 337-TA-
1294, 2022 WL 3357878, at *2, 12–16 (July 20, 2022). The
ALJ then issued her initial determination (“ID”), which de-
termined that there was a violation of section 337. Initial
Determination, Inv. No. 337-TA-1294, 2023 WL 2644291,
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BRITA LP v. ITC 7
at *1 (Feb. 28, 2023). As relevant here, the ALJ determined
that asserted claims 1–6 and 23 met the written descrip-
tion and enablement requirements. Id. at *135, 165–66.
On the respondents’ petition for review, the Commis-
sion agreed to review the ALJ’s conclusions concerning:
(1) the construction of “filter usage lifetime claimed by a
manufacturer or seller of the filter” and her determination
that the term was not indefinite; (2) written description;
and (3) enablement. Certain High-Performance Gravity-
Fed Water Filters & Prods. Containing the Same, Inv.
No. 337-TA-1294, 2023 WL 6290623, at *3 (Sep. 22, 2023)
(“Commission Opinion”). The Commission determined
that (1) the term “filter usage lifetime claimed by a manu-
facturer or seller of the filter” is indefinite; (2) the asserted
claims are invalid for lack of written description as to any
filter media meeting the claimed FRAP factor other than
carbon-block filters; and (3) the asserted claims are non-
enabled as to non-carbon-block filters. Id. at *17, *38.
Given these conclusions, the Commission reversed the ID’s
finding of a violation of section 337. Id. at *38.
Brita timely appealed. We have jurisdiction under
28 U.S.C. § 1295(a)(6).
D ISCUSSION
We review the Commission’s legal determinations de
novo and its factual findings for substantial evidence.
Guandong Alison Hi-Tech Co. v. ITC, 936 F.3d 1353, 1358
(Fed. Cir. 2019). Substantial evidence is “such relevant ev-
idence as a reasonable mind might accept as adequate to
support a conclusion.” Consol. Edison Co. v. NLRB, 305
U.S. 197, 229 (1938). Importantly, “the possibility of draw-
ing two inconsistent conclusions from the evidence does not
prevent an administrative agency’s finding from being sup-
ported by substantial evidence. Consolo v. Fed. Mar.
Comm’n, 383 U.S. 607, 620 (1966).
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BRITA LP v. ITC 8
On appeal, Brita challenges the Commission’s determi-
nations regarding: (1) written description, (2) enablement,
and (3) indefiniteness. We address each issue in turn.
I
We begin with written description. Section 112 of the
Patent Act contains a written description requirement dis-
tinct from the enablement requirement. 35 U.S.C. § 112
¶ 1 (pre-AIA); see Ariad Pharm., Inc. v. Eli Lilly & Co.,
598 F.3d 1336, 1340 (Fed. Cir. 2010) (en banc). To satisfy
written description, the disclosure of the application must
“reasonably convey[] to those skilled in the art that the in-
ventor had possession of the claimed subject matter as of
the filing date.” Ariad, 598 F.3d at 1351. Assessing such
“possession as shown in the disclosure” requires “an objec-
tive inquiry into the four corners of the specification from
the perspective of a person of ordinary skill in the art.” Id.
“[T]he specification must describe an invention under-
standable to [a person of ordinary skill in the art] and show
that the inventor actually invented the invention claimed.”
Id. A “mere wish or plan” for obtaining the claimed inven-
tion is not adequate written description. Regents of the
Univ. of Cal. v. Eli Lilly & Co., 119 F.3d 1559, 1566
(Fed. Cir. 1997).
Whether the asserted claims of the ’141 patent lack
written description support is a question of fact that we re-
view for substantial evidence. Rivera v. ITC, 857 F.3d
1315, 1319 (Fed. Cir. 2017). Here, the asserted claims
cover any filtration media type with activated carbon and
a lead scavenger that meet the functional FRAP factor lim-
itation. As discussed below, substantial evidence supports
the Commission’s determination that the asserted claims
lack written description support as to any filter media
meeting the claimed FRAP factor other than carbon-block
filters.
The Commission found that the specification “only pro-
vides examples of ‘gravity flow carbon blocks that have a
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BRITA LP v. ITC 9
FRAP factor of less than 350.’” Commission Opinion, 2023
WL 6290623, at *21 (quoting ’141 patent col. 26 ll. 63–67).
We agree. While broadly claiming any “filter media includ-
ing at least activated carbon and a lead scavenger; wherein
the filter achieves a [FRAP] factor of about 350 or less,”
’141 patent claim 1, the specification describes only a single
type of filter media that can meet the claimed FRAP fac-
tor—carbon block. The ’141 patent provides a number of
“examples” of the “formulations” of filters that were tested
to obtain a FRAP factor. ’141 patent col. 27 l. 14–col. 28
l. 2, Table 1. Table 5 of the ’141 patent demonstrates that
among the filters tested, carbon-block filters were the only
filter that met the claimed FRAP factor of 350 or less. Id.
at col. 33 ll. 16–22, Table 5. Thus, the only working exam-
ples of filters meeting the claimed FRAP factor disclosed in
the ’141 patent are those using carbon-block filter media.
Further, the specification only provides the details of
specific formulations of filter components (e.g., lead
sorbent, carbon, and binder) for carbon blocks, id. at col. 27
l. 14–col. 28 l. 47, and the only types of filters that are il-
lustrated in the figures are carbon blocks. On the other
hand, the tested “mixed media filters fall above the pre-
ferred FRAP range (0–350).” Id. at col. 33 ll. 24–25; see also
id. at col. 26 ll. 61–63 (“No mixed media filters tested met
the claimed FRAP factor range due to their inability to re-
move particulate lead.”); id. at col. 31 ll. 54–55 (“All mixed
media filters tested fail to adequately reduce total led con-
centrations . . . .”).
The Commission cited testimony from both sides’ ex-
perts confirming that the ’141 patent provides working ex-
amples only of carbon-block filters, and no working
examples of any non-carbon-block filters. Commission
Opinion, 2023 WL 6290623, at *20. The inventors them-
selves also testified that they did not invent any non-car-
bon-block filters that would meet the claimed FRAP factor.
Id. at *22. Dr. Elizabeth Knipmeyer, one of the inventors,
testified that in addressing the issue of removing
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BRITA LP v. ITC 10
particulate lead in water filters without sacrificing flow
rates, her group “changed technology from a granular me-
dia to a carbon block.” J.A. 32707–08 (Dr. Knipmeyer’s
deposition testimony); see also J.A. 22202 (Dr. Knipmeyer’s
testimony at evidentiary hearing).
The Commission also found that, as far as filters meet-
ing the required FRAP factor, “[b]y their own admission in
the patent, the inventors were only in possession of a filter
that uses carbon blocks, not other types of filter media.”
Commission Opinion, 2023 WL 6290623, at *21. Again, we
agree. The specification states that “[t]he formulations of
gravity fed carbon blocks disclosed are unique in [their]
ability to meet the required FRAP factor.” ’141 patent col.
26 ll. 63–65. The properties that make carbon blocks
“unique” are evident from other portions of the specifica-
tion, where the ’141 patent describes the benefits of carbon
blocks while identifying the “drawbacks,” “problems,” and
“disadvantages” of other filter media. See, e.g., id. at col. 3
l. 57–col. 4 l. 24. Notably, the ’141 patent purports to con-
figure carbon-block filters in such a way that addresses is-
sues particular to carbon blocks to enhance performance,
whereas other types of filter media face different perfor-
mance limitations.
Indeed, the distinctions between carbon blocks and
other types of filter media pervade the ’141 patent. For ex-
ample, the specification explains that mixed or blended me-
dia using carbon granules and other additives have limited
contaminant removal capability. Id. at col. 3 l. 57–col. 4
l. 11. This is because of the nature of loose granular media,
namely, “particle size and packing geometry of the gran-
ules,” which causes water to flow through the voids be-
tween granules rather than directly contacting the
granules. Id. at col. 3 l. 64–col. 4 l. 5. The ’141 patent ex-
plains that one way to address the issue of water flowing
through the voids is to use smaller granules, however, do-
ing so comes at the cost of longer filtration time. Id. at col.
4 ll. 20–24. Another factor affecting performance is that
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BRITA LP v. ITC 11
granular media is hydrophobic, meaning the granules tend
to resist wetting and thus it is difficult for such a filter to
readily absorb water. Id. at col. 4 ll. 41–67.
Carbon blocks, by their nature, do not face the same
problems and exhibit particular structural and chemical
properties that make them advantageous for water filtra-
tion. Because they are formed in “an integrated, porous,
composite, carbon block,” id. at col. 13 ll. 23–24, there are
no loose granules, and the carbon-block filter media can
achieve more effective flow characteristics. Id. at col. 14
l. 53–col. 15 l. 6. Also, “one can achieve a carbon block that
is hydrophilic and readily absorbs water.” Id. at col. 14
ll. 31–41.
The ’141 patent purports to achieve further refine-
ments of carbon-block filters by maximizing the surface
area of the media available for filtration. Id. at col. 14
ll. 39–41; see also id. at col. 17 ll. 39–42 (seeking to “max-
imize the volume of a filtration media block media in a
given cartridge or housing total volume, while decreasing
pressure drop”). It also describes embodiments that em-
ploy a multi-core structure for carbon blocks to ensure ef-
fective water filtration. Id. at col. 23 ll. 18–45. The patent
remarks on the “noteworthy” property of such carbon
blocks as providing “excellent performance” for water fil-
tration. Id. at col. 23 ll. 25–37. Thus, the specification it-
self amply supports the conclusion that the ’141 patent only
discloses carbon-block filters as being unique in their abil-
ity to meet the claimed FRAP factor. The ’141 patent’s dis-
closure does not demonstrate possession of non-carbon-
block filter media achieving the claimed FRAP factor.
Other evidence, discussed below, reinforces this conclusion.
“[T]he level of detail required to satisfy the written de-
scription requirement varies depending on the nature and
scope of the claims and on the complexity and predictabil-
ity of the relevant technology.” Ariad, 598 F.3d at 1351
(citing Capon v. Eshhar, 418 F.3d 1349, 1357–58 (Fed. Cir.
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BRITA LP v. ITC 12
2005)). The witness testimony in this case, while acknowl-
edging that individual variables within the FRAP equation
were known, demonstrates that achieving the required
FRAP factor with any filter media was a complex task with
unpredictable challenges. J.A. 23434–38 (respondents’ ex-
pert, Dr. Gary Hatch, testifying to the interrelated nature
of the variables in the FRAP equation, such that changing
one variable in a filter can result in unpredictable changes
in other variables and the ultimate FRAP value); see also
J.A. 23467–68 (Dr. Hatch testifying that while it would be
possible to configure a gravity-fed water filter in order to
achieve “certain desired benefits, such as faster flow rate
or improved contaminant reduction,” doing so would in-
volve compromising other aspects of performance); J.A.
22218–19 (Brita’s witness, Dr. Knipmeyer, testifying that
the variables in the FRAP equation are “all interrelated”).
This also comports with the statements of the applicant in
the parent application to the ’141 patent that the art of
making an effective filter is a “very difficult task” and that
“small differences in many variables can make large differ-
ences in . . . performance.” J.A. 41077, 41112–13.
The inventors’ admissions that they did not create non-
carbon-block filters achieving the claimed FRAP factor,
and that doing so would involve “new technology” further
confirms the conclusion that the ’141 patent’s disclosure
does not demonstrate possession of non-carbon-block filter
media achieving the claimed FRAP factor. See Commission
Opinion, 2023 WL 6290623, at *22, *35–36. The inventor
testimony here “illuminates the absence of critical descrip-
tion in this case.” Nuvo Pharms. (Ir.) Designated Activity
Co. v. Dr. Reddy’s Labs. Inc., 923 F.3d 1368, 1381 (Fed. Cir.
2019). It is not enough for the patent to simply mention a
desired outcome, i.e., “meeting the [FRAP] performance cri-
teria,” ’141 patent col. 25 ll. 9–12, with non-carbon-block
filter media. See Ariad, 598 F.3d at 1357. Here, the writ-
ten description requirement demands that the specifica-
tion provide more detail than merely listing examples of
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BRITA LP v. ITC 13
non-carbon-block filter media, particularly when the record
evidence shows no such media met the claimed FRAP fac-
tor at the time of invention.
Brita offers three principal arguments for why the
Commission erred in determining a lack of written descrip-
tion. We find none of them persuasive, as they fail to over-
come the express disclosures in the patent and undisputed
testimony of the inventors and experts. First, Brita argues
that the original claims provide sufficient written descrip-
tion support. Appellant’s Br. 33–36. Second, Brita asserts
that generic statements in the specification suggesting its
invention is “applicable to all embodiments” provides con-
structive reduction to practice. Id. at 36–38. Third, Brita
argues that the ’141 patent adequately discloses repre-
sentative examples and common structural features sup-
porting its possession of the “genus” of filters covered by
claim 1. Id. at 38–40. Brita recognizes that its arguments
are “related,” id. at 33, and so we will address them to-
gether.
“[W]hile it is true that original claims are part of the
original specification, that truism fails to address the ques-
tion whether original claim language necessarily discloses
the subject matter that it claims.” Ariad, 598 F.3d at 1349
(citation omitted); see also Enzo Biochem, Inc. v. Gen-Probe
Inc., 323 F.3d 956, 968–69 (Fed. Cir. 2002) (“If a purported
description of an invention does not meet the requirements
of the statute, the fact that it appears as an original claim
or in the specification does not save it.”). Brita’s original
claims, reciting “filter media including at least activated
carbon and a lead scavenger,” ’141 patent claim 1, do noth-
ing to provide an adequate description of the types of filter
media that can satisfy the claimed FRAP factor. Nor does
the mere fact that these words appear in the specification
suggest to a skilled artisan that the inventors were in pos-
session of an invention comprising non-carbon-block filter
media that can meet the claimed FRAP factor. None of the
generic citations to different types of filter media, ’141
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BRITA LP v. ITC 14
patent col. 13 ll. 30–34, col. 25 ll. 5–12, and col. 26 ll. 30–
37, relay any meaningful disclosure related to the specific
FRAP factor limitations in the asserted claims beyond ex-
pressing a desired result.
We have held that a genus can be sufficiently disclosed
by “either a representative number of species falling within
the scope of the genus or structural features common to the
members of the genus so that one of skill in the art can
visualize or recognize the members of the genus.” Ariad,
598 F.3d at 1350 (cleaned up). The problem with Brita’s
genus argument, however, is that the ’141 patent does not
identify a representative number of species or common
structural features of members of the alleged genus. And
the problem “is especially acute with genus claims that use
functional language to define the boundaries of a claimed
genus.” Id. at 1349.
Contrary to Brita’s argument that “the claimed inven-
tion is a novel way of arranging known filter-media types,”
Appellant’s Br. 39, claim 1 is defined functionally. The
claim requires a functional result, namely, “achiev[ing]” a
value of its self-defined FRAP factor of 350 or less. ’141
patent col. 34 ll. 10–12. Indeed, the Commission recog-
nized that the ’141 patent claims “any and all filtration me-
dia types with activated carbon and a lead scavenger that
meet the functional FRAP factor limitation.” Commission
Opinion, 2023 WL 6290623, at *20. For a broad, functional
claim to meet the written description requirement, the pa-
tentee must demonstrate he “has invented species suffi-
cient to support a claim to the functionally-defined genus.”
Ariad, 598 F.3d at 1349.
As discussed above, the ’141 patent does not disclose
species other than carbon-block filters that can meet the
claimed FRAP factor. Brita’s reliance on the specification’s
statement that “[t]he nature of the filter meeting the fol-
lowing performance criteria is independent of the exact em-
bodiment of the filter,” is misplaced. Appellant’s Br. 35–36
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BRITA LP v. ITC 15
(citing ’141 patent col. 25 ll. 9–12). The specification does
not demonstrate that satisfying the claimed FRAP factor
can be decoupled from the properties of carbon-block fil-
ters. Merely pronouncing that the “nature of the filter
meeting” the FRAP factor is independent of the exact em-
bodiment does not make it so, particularly in light of the
patent’s testing results that demonstrate otherwise. And,
while the specification may provide a listing of various
types of filter media, including non-carbon-block media,
and state that the FRAP factor criteria is “applicable” to
filters using different types of media, id. at col. 13 ll. 30–34
and col. 26 ll. 30–37, this does nothing to show possession
of non-carbon-block media that meets the claim’s require-
ments of a FRAP factor of 350 or less.
Furthermore, the ’141 patent does not explain what
common characteristics its carbon-block filters would share
with non-carbon-block filters that might make them effec-
tive for meeting the claimed FRAP factor. Instead, the pa-
tent suggests the opposite, that “[t]he formulations of
gravity fed carbon blocks disclosed are unique.” ’141 patent
col. 26 ll. 63–65. As detailed above, the specification de-
scribes numerous advantageous characteristics for water
filtration that are unique to carbon blocks and which are
inapplicable to other media, like loose granular and mixed
media. The mere inclusion of activated carbon and lead
scavenger is not enough to achieve the claimed FRAP fac-
tor. Id. at Table 5 (showing mixed media filters, having
activated carbon and lead scavenger, outside the claimed
FRAP factor range). The ’141 patent’s failure to describe
structural features common to the members of the genus
“so that one of skill in the art can visualize or recognize the
members of the genus” further demonstrates its lack of
support for a claim to a genus encompassing non-carbon-
block filters. Ariad, 598 F.3d at 1350 (cleaned up).
Brita’s reliance on the knowledge of persons of ordinary
skill is similarly unavailing. Brita alleges this case in-
volves a “predictable art,” and so less detail is required to
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BRITA LP v. ITC 16
show adequate written description. Appellant’s Br. 33, 39.
According to Brita, because other non-carbon-block filter
media types were known to those of ordinary skill in the
art, the ’141 patent’s detailed description of carbon-block
embodiments “sufficed to show possession of an invention
applicable to other well-known filter media types.” Id. at
39–40. Brita also argues that a skilled artisan would know
how to configure filters to achieve “certain desired bene-
fits.” Id. at 39 (citing the questioning of Dr. Hatch). What
Brita overlooks is that in the context of the FRAP equation
(itself previously unknown), the ultimate effect of adjusting
known variables was far from certain. That is, while one
might know how to configure a filter to individually achieve
“certain desired benefits,” such as “faster flow rate” or “im-
proved contaminant reduction,” J.A. 23468, the effect that
this has on the overall FRAP value is unpredictable due to
the interrelatedness of variables. J.A. 23437. Even
Dr. Knipmeyer admitted that the individual variables in
the FRAP equation are “interrelated.” J.A. 22219. Thus,
even accepting Brita’s argument that an ordinarily skilled
artisan would know how to configure individual variables
of the FRAP equation in other, well-known filter media, it
does not follow that an ordinary artisan would know how
to configure such filter media to achieve a FRAP factor of
350 or less.
“The knowledge of ordinary artisans may be used to in-
form what is actually in the specification, but not to teach
limitations that are not in the specification, even if those
limitations would be rendered obvious by the disclosure in
the specification.” Rivera, 857 F.3d at 1322 (cleaned up).
Here, Brita cannot use the knowledge of a skilled artisan
to make up for the specification’s lack of disclosure as to
non-carbon-block filters that can meet the claimed FRAP
factor. Brita has not shown that a skilled artisan would
understand that the specification discloses non-carbon-
block filters meeting the claimed FRAP factor.
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BRITA LP v. ITC 17
In sum, substantial evidence supports the Commis-
sion’s determination that the asserted claims of the ’141
patent lack adequate written description. The Commission
appropriately found that the specification, read in light of
the background knowledge in the art, failed to inform a
skilled artisan that the inventors were in possession of fil-
ter media other than carbon blocks that achieve the
claimed FRAP factor.
II
We separately address the Commission’s determina-
tion that the asserted claims of the ’141 patent are non-
enabled as to non-carbon-block filters. Section 112 sets
forth the enablement requirement: “The specification shall
contain a written description of the invention, and of the
manner and process of making and using it, in such full,
clear, concise, and exact terms as to enable any person
skilled in the art to which it pertains . . . to make and use
the same.” 35 U.S.C. § 112 ¶ 1 (pre-AIA). “If a patent
claims an entire class of processes, machines, manufac-
tures, or compositions of matter, the patent’s specification
must enable a person skilled in the art to make and use the
entire class. In other words, the specification must enable
the full scope of the invention as defined by the claims.”
Amgen Inc. v. Sanofi, 598 U.S. 594, 610 (2023). The stand-
ard for enablement is whether a person skilled in the art
can “make and use” the invention “without undue experi-
mentation.” In re Wands, 858 F.2d 731, 735–37 (Fed. Cir.
1988). Enablement is a question of law reviewed de novo
based on underlying factual findings reviewed for substan-
tial evidence. FS.com Inc. v. ITC, 65 F.4th 1373, 1376 (Fed.
Cir. 2023).
The Commission analyzed each of the Wands factors
and concluded that it would take undue experimentation
to make and use non-carbon-block filters that meet the
claim requirements. Commission Opinion, 2023 WL
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BRITA LP v. ITC 18
6290623, at *36–37. Brita fails to identify any reversible
error in the Commission’s analysis.
Brita primarily argues that the Commission misread
the specification by treating its admissions of the inability
of tested mixed media filters to meet the claimed FRAP fac-
tor as a failure by the inventors to apply their invention to
non-carbon-block filter media. Oral Arg. at 1:37–2:21,
(“The Commission’s decision hinges on a plain misreading
of column 26.”).1 We are not persuaded that the Commis-
sion misinterpreted the specification of the ’141 patent.
The relevant passage reads: “No mixed media filters
tested met the claimed FRAP factor range due to their in-
ability to remove particulate lead. The formulations of
gravity fed carbon blocks disclosed are unique in [their]
ability to meet the required FRAP factor.” ’141 patent
col. 26 ll. 61–65. In its Wands factor analysis, the Commis-
sion determined that the ’141 patent specification provides
no teaching on how any filter other than carbon block can
achieve the required FRAP factor. Commission Opinion,
2023 WL 6290623, at *31–32. In support, the Commission
cited this passage and others in the ’141 patent explaining
that the tested mixed media filters “fail to adequately re-
duce” lead concentrations. Id. at *31 (citing ’141 patent
col. 31 ll. 9–10, col. 31 ll. 54–55). Despite the conceded fail-
ures of the tested filters, the specification “does not provide
a road map for how mixed media materials, or any type of
filter other than carbon blocks, can achieve the required
FRAP.” Commission Opinion, 2023 WL 6290623, at *31.
Much of the same evidence discussed above with re-
spect to written description also supports the Commission’s
findings regarding enablement. For example, the ’141 pa-
tent describes some of the specific problems that prevent
1 No. 24-1098, https://www.cafc.uscourts.gov/oral-
arguments/24-1098_08052025.mp3.
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BRITA LP v. ITC 19
non-carbon-block filter media types, like mixed media,
from achieving performance comparable to the carbon
blocks that meet the claimed FRAP factor. See, e.g., ’141
patent col. 3 ll. 51–67 (limited contaminant removal capa-
bility), col. 4 ll. 41–67 (hydrophobic nature of granular me-
dia). Even though the ’141 patent acknowledges that non-
carbon-block filters are different from carbon-block filters,
the ’141 patent provides no solutions to overcome the prob-
lems associated with non-carbon-block filters, and instead
characterizes its formulations of carbon-block filters meet-
ing the claimed FRAP factor as “unique.” Id. at col. 26
ll. 63–65. The inventors’ testimony confirms that the in-
ventors did not create any working examples of non-car-
bon-block filters, i.e., the inventors failed to create any
filters besides carbon block that achieved the claimed
FRAP factor. Commission Opinion, 2023 WL 6290623, at
*31. Indeed, Dr. Knipmeyer testified that she “changed
technology from a granular media to a carbon block” in de-
veloping the invention. J.A. 32707–08.
Brita further argues that the passage in column 26 of
the patent is unremarkable because the mixed media fil-
ters tested were prior art, which merely demonstrates nov-
elty. Oral Arg. at 2:22–2:32. Regardless of whether the
tested filters were prior art, the fact remains that the spec-
ification does not provide any teaching or guidance on how
to achieve the claimed FRAP factor with any type of filter
besides carbon block, going so far as to disparage other fil-
ter types. Taken together with the specification’s descrip-
tion of “drawbacks,” “problems,” and “disadvantages” of
non-carbon-block filter media, ’141 patent col. 3 l. 57–col. 4
l. 24, the specification’s test results constitute a “clear[] and
strong[] warn[ing]” against non-carbon-block filter media.
See AK Steel Corp. v. Sollac, 344 F.3d 1234, 1244 (Fed. Cir.
2003).
Brita’s other principal argument is that the invention
of the ’141 patent involves a “highly developed, predictable
art.” Appellant’s Br. 30–32. This stands in stark contrast
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BRITA LP v. ITC 20
to the Commission’s findings on the Wands factors. Com-
mission Opinion, 2023 WL 6290623, at *33–35. For exam-
ple, the Commission, recognizing that the invention is
“directed broadly to gravity-fed water filters that can
achieve FRAP of less than 350,” found “the nature of the
invention is not gravity-fed water filters generally, but
gravity-fed water filters that achieve the claimed FRAP
with any type of filter media,” id. at *33–34, and that the
variables of the FRAP equation are “interrelated such that
changing one variable will change other variables in a non-
linear and unpredictable manner,” id. at *34. We find no
error in the Commission’s findings.
Ample evidence in the record before us supports the
finding of lack of predictability in the relevant field. At oral
argument, Brita argued that both parties’ experts agreed
that a skilled artisan would know how to modify the vari-
ous components of a filter in order to achieve desired char-
acteristics. Oral Arg. at 10:57–11:08 (citing to J.A.
23467–68). However, as discussed in Section I of the dis-
cussion section in this opinion concerning written descrip-
tion, Brita’s argument fails to adequately account for the
unpredictable nature of the FRAP equation itself due to the
interrelatedness of its input characteristics. Respondents’
expert, Dr. Hatch, merely acknowledged it was known that
one could configure a filter to achieve “certain desired ben-
efits” such as volume, flow rate, or contaminant reduction.
J.A. 23468. That is, one could configure a filter to achieve
a certain value for the input variables to the FRAP equa-
tion. It does not follow, however, that one could configure
a filter of any media type to achieve the claimed FRAP fac-
tor—let alone that the specification enabled an ordinary ar-
tisan to do so without undue experimentation. Dr. Hatch
testified that the input variables to the FRAP equation are
“interrelated” and that “when you change one of these fac-
tors, you do not know what is going to be the final result of
your FRAP value.” J.A. 23437. Dr. Knipmeyer also
acknowledged that the variables are “interrelated.” J.A.
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BRITA LP v. ITC 21
22218–19. Moreover, the testimony of Brita’s expert, Dr.
Benny Freeman, demonstrates agreement with this princi-
ple that a particular change to one variable in the FRAP
equation affects others. The ’141 patent itself recognizes
the tradeoff relationship between some aspects of filter
characteristics in the context of granular media. ’141 pa-
tent col. 4 ll. 41–67 (the goal of fast flowrate is counter to
long lifetime and effective contaminant removal). But im-
portantly, the patent does not explain how to adjust the
various characteristics to achieve the claimed FRAP factor
for such granular media, or for any filter media besides car-
bon block.
Furthermore, Dr. Knipmeyer’s testimony that creating
non-carbon-block embodiments would involve “new tech-
nology,” J.A. 32984, severely undercuts Brita’s reliance on
the level of skill in the art. The Commission found that
“how to develop that new technology remains unclear and
unpredictable from [the] patent disclosure.” Commission
Opinion, 2023 WL 6290623, at *35. As discussed above,
the specification lacks any guidance on how to achieve the
claimed FRAP factor with filter media other than carbon
block.
We have held that “[i]t is the specification, not the
knowledge of one skilled in the art, that must supply the
novel aspects of an invention in order to constitute ade-
quate enablement.” Genentech, Inc. v. Novo Nordisk A/S,
108 F.3d 1361, 1366 (Fed. Cir. 1997). Brita’s reliance on
Dr. Freeman’s testimony that one could use the same
“starting materials” and reach the claimed invention es-
sentially places the entire inventive effort on one of ordi-
nary skill in the art. This violates the very quid pro quo
central to the enablement requirement—“requiring a pa-
tentee to teach the public how ‘to practice the full scope of
the claimed invention.’” McRO, Inc. v. Bandai Namco
Games Am. Inc., 959 F.3d 1091, 1091–1100 (Fed. Cir. 2020)
(quoting AK Steel, 344 F.3d at 1244). In light of other rec-
ord evidence demonstrating the differences between carbon
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BRITA LP v. ITC 22
blocks and other filter media types, the specification’s lack
of disclosure to guide one of ordinary skill to achieve the
claimed FRAP factor with other filter media is fatal to
Brita’s argument.
We conclude that substantial evidence supports the
factual findings as to the Wands factors underlying the
Commission’s enablement determination. The record thus
supports the Commission’s legal conclusion that the ’141
patent required undue experimentation to enable the full
scope of the asserted claims.
III
The Commission ultimately determined there could be
no section 337 violation because the asserted claims of the
’141 patent were invalid. We are not required to address
every possible ground on which the Commission’s determi-
nation might be sustained. Solomon Techs., Inc. v. ITC,
524 F.3d 1310, 1320 (Fed. Cir. 2008). Therefore, we decline
to reach the issue of indefiniteness.
CONCLUSION
For the foregoing reasons, we affirm.
AFFIRMED
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