Court Opinion

ID: 4423084
Source: CourtListenerOpinion
Date Created: 2019-08-06 16:00:46.550845+00
Date Added: 2024-06-11T12:52:01.989947
License: Public Domain

United States Court of Appeals
     for the Federal Circuit
             ______________________

AJINOMOTO CO., INC., AJINOMOTO HEARTLAND
                   INC.,
                 Appellants

                       v.

    INTERNATIONAL TRADE COMMISSION,
                Appellee

CJ CHEILJEDANG CORP., CJ AMERICA, INC., PT
        CHEILJEDANG INDONESIA,
               Intervenors

--------------------------------------------

CJ CHEILJEDANG CORP., CJ AMERICA, INC., PT
        CHEILJEDANG INDONESIA,
                Appellants

                       v.

    INTERNATIONAL TRADE COMMISSION,
                Appellee

AJINOMOTO CO., INC., AJINOMOTO HEARTLAND
                    INC.,
                 Intervenors
           ______________________

              2018-1590, 2018-1629
             ______________________
2                                  AJINOMOTO CO., INC. v. ITC

   Appeals from the United States International Trade
Commission in Investigation No. 337-TA-1005.
                ______________________

                  Decided: August 6, 2019
                  ______________________

    JOHN D. LIVINGSTONE, Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP, Atlanta, GA, argued for Ajinomoto
Co., Inc., Ajinomoto Heartland Inc. Also represented by
MARTIN DAVID WEINGARTEN; CHARLES E. LIPSEY, Reston,
VA; MAREESA ARNITA FREDERICK, CORA RENAE HOLT,
BARBARA RUDOLPH, Washington, DC.

   HOUDA MORAD, Office of General Counsel, United
States International Trade Commission, Washington, DC,
argued for appellee. Also represented by SIDNEY A.
ROSENZWEIG, DOMINIC L. BIANCHI, WAYNE W. HERRINGTON.

   JAMES F. HALEY, JR., Haley Guiliano LLP, New York,
NY, argued for CJ CheilJedang Corp., CJ America, Inc., PT
CheiJedang Indonesia. Also represented by STEVEN PEPE,
Ropes & Gray LLP, New York, NY; MATTHEW RIZZOLO,
Washington, DC.
                ______________________

     Before DYK, MOORE, and TARANTO, Circuit Judges.
    Opinion for the court filed by Circuit Judge TARANTO.
Opinion concurring in part and dissenting in part filed by
                  Circuit Judge DYK.
TARANTO, Circuit Judge.
    Ajinomoto Co., Inc. and Ajinomoto Heartland Inc. (col-
lectively, Ajinomoto) filed a complaint against CJ
CheilJedang Corp., CJ America, Inc., and PT CheilJedang
Indonesia (collectively, CJ) with the International Trade
Commission, alleging that CJ was importing certain
AJINOMOTO CO., INC. v. ITC                                 3

products that infringed Ajinomoto’s U.S. Patent No.
7,666,655. CJ used several strains of Escherichia coli bac-
teria to produce L-tryptophan products, which it then im-
ported into the United States.           The Commission
determined that CJ’s earlier strains did not infringe but
that CJ’s two later strains did. The Commission also found
that the relevant claim of the ’655 patent is not invalid for
lack of an adequate written description.
    Ajinomoto appeals the Commission’s claim construc-
tion underlying the determination of no infringement by
the earlier strains. CJ cross-appeals aspects of the deter-
mination of infringement by the later strains and the rejec-
tion of the invalidity challenge. We affirm.
                              I
                             A
    The ’655 patent claims E. coli bacteria that have been
genetically engineered to increase their production of aro-
matic L-amino acids, such as L-tryptophan, during fermen-
tation, as well as methods of producing aromatic L-amino
acids using such bacteria. See ’655 patent, col. 2, lines 40–
45. In particular, the ’655 patent identifies a specific gene
in the E. coli genome, the yddG gene, that encodes a mem-
brane protein, the YddG protein. Id., col. 2, lines 46–48.
That protein transports aromatic L-amino acids out of the
bacterial cell and into the surrounding culture medium,
where they can be collected. See id., col. 7, lines 11–16.
When yddG gene activity in bacteria is enhanced so that
more YddG protein is produced, the bacteria show in-
creased production of, and increased resistance to, aro-
matic L-amino acids. Id., col. 2, lines 49–57. 1

    1  The specification defines a bacterium’s “resistance”
to an amino acid as its ability “to grow on a minimal me-
dium containing” the amino acid on “which unmodified or
4                                     AJINOMOTO CO., INC. v. ITC

     The ’655 patent describes three ways to enhance the
activity of the yddG gene. First, plasmids containing addi-
tional copies of the yddG gene can be introduced into the
bacterium. Id., col. 2, lines 50–52; id., col. 5, line 62,
through col. 6, line 2. Second, additional copies of the yddG
gene can be inserted into the bacterial chromosome. Id.,
col. 2, lines 52–54; id., col. 6, lines 3–6. Third, a stronger
“promoter” than the one native to the E. coli yddG gene can
be used. Id., col. 2, lines 54–57; id., col. 6, lines 12–15. 2
   Claim 20, the only claim of the ’655 patent still asserted
when the Commission issued its decision, claims “[a]
method for producing an aromatic L-amino acid, which
comprises cultivating the bacterium according to any
one of claims 9–12, 13, 14, 15–18, or 19.” Id., col. 24, lines

the wild type, or the parental strain of the bacterium can-
not grow,” or its ability “to grow faster” on such a medium
“than unmodified or the wild type, or the parental strain of
the bacterium.” ’655 patent, col. 4, lines 49–56.
     2   A promoter is a nucleotide sequence within a DNA
molecule, located adjacent to the nucleotide sequence that
constitutes the gene to be expressed. The Lewin textbook
cited by Ajinomoto shows a “typical promoter” around 41
nucleotides long. J.A. 6043; see also J.A. 6177 (article by
Deuschle et al., cited at ’655 patent, col. 6, lines 18–21,
showing longer promoters). The promoter is the binding
site for RNA polymerase, which initiates transcription (the
first step in gene expression) by separating the two strands
of DNA. The ’655 patent’s specification defines “[s]trength
of promoter” with reference to the “frequency of acts of the
RNA synthesis initiation.” ’655 patent, col. 6, lines 15–16.
     The promoter is only one part of a gene’s “expression
regulation sequence,” which controls expression of the
gene. See id., col. 3, line 14; id., col. 5, line 2. Besides pro-
moters, the “expression regulation sequence” can include,
e.g., operators, enhancers, terminators, and silencers.
AJINOMOTO CO., INC. v. ITC                                  5

4–6 (emphasis added). Of the claims in that list, claims 9
and 15 are the independent claims, and they are the two
alternatives, under claim 20, of importance in this case.
    Claim 9 recites:
        9. A recombinant Escherichia coli bacterium,
    which has the ability to accumulate aromatic L-
    amino acid in a medium, wherein the aromatic L-
    amino acid production by said bacterium is en-
    hanced by enhancing activity of a protein in a cell
    of said bacterium beyond the levels observed in a
    wild-type of said bacterium,
       [1] and in which said protein consists of the
    amino acid sequence of SEQ ID NO: 2
        [2] and said protein has the activity to make
    the bacterium resistant to L-phenylalanine, fluoro-
    phenylalanine or 5[-]fluoro-DL-tryptophan,
        [3] wherein the activity of the protein is en-
    hanced by [3a] transformation of the bacterium
    with a DNA encoding the protein to express the
    protein in the bacterium, [3b] by replacing the na-
    tive promoter which precedes the DNA on the chro-
    mosome of the bacterium with a more potent
    promoter, [3c] or by introduction of multiple copies
    of the DNA encoding said protein into the chromo-
    some of said bacterium to express the protein in
    said bacterium.
Id., col. 22, lines 51–67 (paragraph breaks and bold num-
bering added). The Commission referred to limitation [1]
as the “protein limitation,” limitation [2] as the “resistance
limitation,” and limitation [3] as the “enhancement limita-
tion.” Claim 15 is materially identical to claim 9, except for
the protein limitation. Whereas claim 9 identifies the
claimed protein by a specific amino-acid sequence, claim 15
identifies it by reference to a corresponding DNA se-
quence—a protein “encoded by the nucleotide sequence
6                                  AJINOMOTO CO., INC. v. ITC

which hybridizes with the complement of the nucleotide se-
quence of SEQ ID NO: 1 under” certain conditions. See id.,
col. 23, lines 14–32.
                             B
    In May 2016, Ajinomoto filed a complaint against CJ
with the Commission under 19 U.S.C. § 1337. Ajinomoto
alleged that CJ violated § 1337(a)(1)(B)(ii) by importing an-
imal-feed-grade L-tryptophan products produced by a pro-
cess covered by the ’655 patent. 3 The Commission
instituted an investigation based on Ajinomoto’s com-
plaint.
     The parties before us, including the Commission, agree
that whether the accused products were produced by a pro-
cess covered by the patent is a question of infringement.
The proceeding focused on three groups of E. coli strains
that CJ has used to produce tryptophan. First, CJ’s “ear-
lier strains” contained both the native E. coli yddG gene
and the native E. coli yddG promoter, except that the first
nucleotide of the promoter was changed through chemical
mutagenesis, resulting in a stronger promoter. Second, in
November 2016, several months after Ajinomoto filed its
complaint, CJ began using its first “later strain,” which
contained two copies of a yddG gene: (1) the native E. coli
yddG gene with the native E. coli yddG promoter; and (2) a
non-E. coli yddG gene with two promoters—(2a) a native
non-E. coli yddG promoter and (2b) an rmf promoter. 4
Third, in December 2016, CJ started using its second “later

    3   Ajinomoto also alleged that CJ infringed U.S. Pa-
tent No. 6,180,373, which similarly claims methods of pro-
ducing tryptophan using genetically engineered bacteria.
The ’373 patent expired on January 30, 2018, and is not at
issue in this court.
    4   The rmf and rhtB promoters are promoters associ-
ated with other genes in the E. coli genome.
AJINOMOTO CO., INC. v. ITC                                 7

strain,” which also contained two copies of a yddG gene:
(1) the native E. coli yddG gene with the native E. coli
yddG promoter; and (2) a codon-randomized non-E. coli
yddG gene with two promoters—(2a) an rmf promoter and
(2b) an rhtB promoter. 5
     In August 2017, the administrative law judge (ALJ) is-
sued a final initial determination. The ALJ construed “re-
placing the native promoter . . . with a more potent
promoter” in the enhancement limitation to mean “remov-
ing the native upstream region of the yddG gene and in-
serting one of a class of promoters that controls expression
of a different gene.” J.A. 90–91. Using that construction,
the ALJ found that CJ’s earlier strains did not infringe; he
found that they failed to meet the enhancement limitation
because CJ created the more potent promoter in those
strains by mutagenesis of a single nucleotide rather than
removal of the entire native promoter and insertion of a
new promoter. As to CJ’s later strains, the ALJ found that
(a) the first later strain did not infringe because Ajinomoto
had failed to prove that it met the resistance limitation,
and (b) the second later strain also did not infringe because

    5    Each particular codon (three nucleotides in a row
on a DNA molecule) that encodes for an amino acid always
encodes for the same amino acid, but many of the 20 amino
acids are encoded by more than one of the 64 codons. See
Amgen, Inc. v. Chugai Pharm. Co., 927 F.2d 1200, 1208 n.4
(Fed. Cir. 1991) (discussing “redundancy” of genetic code).
For instance, the DNA sequences TTA and TTG both code
for the amino acid leucine. “Codon randomization” refers
to creation of DNA molecules that use different codons (e.g.,
TTA or TTG) to code for the same amino acid (e.g., leucine)
in building the same protein. See Mycogen Plant Sci. v.
Monsanto Co., 243 F.3d 1316, 1323 (Fed. Cir. 2001) (“[O]ne
codon can be substituted for another in the gene without
changing the amino acid and resulting protein.”).
8                                  AJINOMOTO CO., INC. v. ITC

its non-E. coli YddG protein was not equivalent to the
claimed E. coli YddG protein under the doctrine of equiva-
lents. Finally, the ALJ found that claim 20 of the ’655 pa-
tent is invalid for lack of an adequate written description
of the “more potent promoter” limitation incorporated into
that claim.
     In October 2017, the full Commission decided to review
the ALJ’s final initial determination in its entirety, and in
December 2017, the Commission issued its decision. It af-
firmed the ALJ’s construction of “replacing the native pro-
moter . . . with a more potent promoter” and accordingly
affirmed the ALJ’s finding that CJ’s earlier strains did not
infringe. But the Commission reversed several of the ALJ’s
other findings. Specifically, it determined that both of CJ’s
later strains met all disputed claim limitations and thus
infringed claim 20 and that claim 20 was not proved to lack
an adequate written description. The Commission accord-
ingly entered a limited exclusion order against CJ’s infring-
ing products, i.e., those made by both of CJ’s later strains
but not its earlier strains. The Commission also issued a
cease-and-desist order against CJ America, which held in-
ventory of the infringing products.
    Ajinomoto and CJ both timely appealed. We have ju-
risdiction under 28 U.S.C. § 1295(a)(6).
                             II
    We begin with Ajinomoto’s appeal of the Commission’s
finding of no infringement by the earlier strains.
Ajinomoto challenges that finding solely by arguing that
the Commission erred in its claim construction of “replac-
ing the native promoter . . . with a more potent promoter.”
Ajinomoto argues that, properly construed, the phrase is
not limited to removing the entire native promoter and in-
serting a new promoter, as the Commission concluded, but
encompasses mutagenesis of individual nucleotides within
the native promoter. We review the Commission’s claim
construction de novo, as the Commission relied on only
AJINOMOTO CO., INC. v. ITC                                   9

intrinsic evidence and made no factual findings based on
extrinsic evidence. Teva Pharm. USA, Inc. v. Sandoz, Inc.,
135 S. Ct. 831, 841 (2015); see Cont’l Circuits LLC v. Intel
Corp., 915 F.3d 788, 795 (Fed. Cir. 2019). We agree with
the Commission’s claim construction and therefore affirm
the non-infringement finding.
      The ordinary and customary meaning of the claim lan-
guage provides support for the Commission’s claim con-
struction. The language of “replacing the native promoter
. . . with a more potent promoter” suggests, in ordinary par-
lance, an operation at the level of the entire promoter as a
unit, not at the level of a single nucleotide that is just one
small component of the promoter. To say that one is “re-
placing” an object (e.g., a laptop computer, a bicycle, a sail-
boat, a blender) suggests that one is doing more than
altering one small part of it. That suggestion is bolstered
when one also uses language (here, a “more potent pro-
moter”) referring to the replacement at the level of the
overall object. The suggestion is further reinforced by the
most apt of the dictionary definitions of “replace” intro-
duced before the Commission—“to provide a substitute
for.” J.A. 10361; see also J.A. 5622 (patent applicants ex-
plaining “replacing” as “substitut[ing]”). In many contexts,
one would not refer to swapping out one small component
of a larger unit as “replacing” the unit or as providing a
“substitute” for the unit, even though the net result is a
differently constituted larger unit. Context matters, of
course, but here, Ajinomoto has not shown a contrary com-
mon understanding (or even one of several common under-
standings) among relevant artisans in the specific context
of replacing a promoter with a more potent promoter. Ac-
cordingly, the claim language, though hardly establishing
a plain meaning, supports the Commission’s construction.
     The specification offers additional support, though it
too is hardly plain insofar as it bears on the particular con-
struction issue. The specification states that “the enhance-
ment of gene expression can be achieved by locating the
10                                    AJINOMOTO CO., INC. v. ITC

DNA of the present invention under control of more potent
promoter instead of the native promoter.” ’655 patent,
col. 6, lines 12–15. That statement speaks of a promoter as
a unit, but it does not use the language of “replacing.” In-
deed, the specification nowhere uses that language. But it
does discuss “substituting” promoters, using a term that,
as indicated above, is an apt definition of “replacing” here.
The specification describes “[t]he present inventions” as in-
cluding “[t]he bacterium according to the above bacterium,
wherein native promoter of said DNA is substituted with
more potent promoter.” Id., col. 3, lines 19–21. The term
is then used in Example 4, which is titled “Substitution of
the Native Upstream Region of yddG Gene by the Hybrid
Regulatory Element Carrying the PL Promoter and SDlacZ
in E. coli Chromosome,” and which involves removing the
entire native promoter and inserting a new promoter. See
id., col. 11, line 5, through col. 12, line 46. The sole specifi-
cation example of “substitution” thus fits the Commission’s
claim construction. And while the specification discusses
mutagenesis, it does so only in the context of the protein-
coding region of the yddG gene, not the promoter. See id.,
col. 5, lines 18–30.
    We turn finally to the prosecution history—on which
the parties to this case have focused most of their compet-
ing analyses. We conclude that the best understanding of
what transpired before the examiner further supports the
Commission’s construction. Because the prosecution his-
tory reinforces what is already suggested by the claim lan-
guage and specification, this case provides no occasion,
contrary to Ajinomoto’s contention (Ajinomoto Br. 34), for
requiring clear and unmistakable disavowal or disclaimer
to justify a claim construction contrary to a meaning evi-
dent from the claim language and specification.
     What was claim 2 of the original application recited
“[t]he bacterium according to claim 1, wherein said activi-
ties of proteins . . . is enhanced by transformation of said
bacterium with DNA coding for the protein . . . or by
AJINOMOTO CO., INC. v. ITC                                  11

alteration of expression regulation sequence of said DNA on
the chromosome of the bacterium.” J.A. 5047 (emphasis
added). 6 The examiner rejected the claim for lack of an ad-
equate written description and lack of enablement. As to
written description, the examiner explained that “[w]hile
generic expression regulation sequences are known in the
art, a particular, endogenous expression regulation se-
quence for the DNA that encodes [amino-acid] SEQ ID
NO:2, or related sequences, is not described.” J.A. 5371.
“Without description of the endogenous regulation se-
quence,” the examiner continued, “an endogenous regula-
tion sequence that has been altered to increase expression
of said protein also lacks adequate written description.” Id.
Turning to enablement, the examiner stated:
    The specification, while being enabling for Esche-
    richia strains wherein the native promoter for the
    DNA encoding SEQ ID NO: 2 has been changed by
    substitution with a more potent promoter, does not
    reasonably provide enablement for the genus of an
    L-amino acid producing bacterium wherein the ac-
    tivity of proteins described by SEQ ID NO: 2 and
    related sequences is increased due to specific alter-
    ations within the chromosomal expression regula-
    tion sequence for DNA encoding said proteins.
    ....

    6   Although claims 9 and 15 issued from what were
numbered as claims 12 and 24 when added during prose-
cution, the parties do not dispute that the amendments to
original claim 2 (which eventually was cancelled) are rele-
vant to construing issued claims 9 and 15. The same “re-
placing the native promoter . . . with a more potent
promoter” language added to original claim 2 was eventu-
ally added to claims 9 and 15.
12                                  AJINOMOTO CO., INC. v. ITC

         The instant specification teaches how to select
     Escherichia bacteria that have an increased pro-
     duction of L-amino acids, and the art teaches how
     to mutagenize chromosomal DNA and how to char-
     acterize the mutations in the DNA. However, nei-
     ther the specification nor the art contain any
     examples of how to specifically change endogenous
     Escherichia chromosomal expression regulation se-
     quences for the DNA encoding proteins described
     by SEQ ID NO: 2, or related sequences, such that
     the activity of said proteins in the bacteria is in-
     creased. The art and the specification provide en-
     ablement for inserting a known promoter in the
     chromosomal DNA to upregulate the expression of
     the DNA encoding SEQ ID NO: 2; however, neither
     the specification nor the art enable making specific
     changes to expression regulation sequences for
     DNA encoding SEQ ID NO:2 and related sequences
     on the chromosome of Escherichia bacteria. The
     art and specification lack a detailed description of
     the structure of the instant endogenous expression
     regulation sequences, and they lack any guidance
     on how to alter such sequences such that DNA ex-
     pression is increased; therefore, to make the in-
     stant bacteria with altered expression regulation
     sequences would be unpredictable.
J.A. 5374–75.
    In response to the rejections, the applicants amended
the claim to recite “replacing the native promoter that pre-
cedes a DNA encoding said protein . . . with a more potent
promoter” instead of “by alteration of expression regulation
sequence of said DNA.” J.A. 5610. The applicants ex-
plained the amendment as follows: “Applicants have
amended Claim 2 consistent with the Examiner’s recogni-
tion that the specification enables Escherichia strains
wherein the native promoter for the DNA encoding SEQ ID
AJINOMOTO CO., INC. v. ITC                                  13

NO: 2 has been changed by substitution with a more potent
promoter.” J.A. 5622.
     Reading the written-description and enablement rejec-
tions together, we think that the most reasonable under-
standing of the examiner’s comments is that the examiner
was drawing a distinction between alterations to the pro-
moter, which were sufficiently described and enabled be-
cause E. coli promoters were well understood in the art,
and alterations to the expression-regulation sequence more
broadly, which were not adequately described or enabled.
To be sure, the examiner’s statement that the art and the
specification “lack any guidance on how to alter such se-
quences such that DNA expression is increased” might at
first suggest that the applicants had not described and en-
abled the full scope of “alteration.” But in context, this
statement is best read as meaning that the applicants had
not described and enabled the full scope of “expression reg-
ulation sequence,” so that “alteration” of that sequence also
was not adequately described or enabled, even though gen-
eral techniques for altering DNA sequences were well
known in the relevant art.
    We need not determine the precise basis for the exam-
iner’s rejections, however, as “there is no principle of patent
law that the scope of a surrender of subject matter during
prosecution is limited to what is absolutely necessary to
avoid a prior art reference that was the basis for an exam-
iner's rejection.” Norian Corp. v. Stryker Corp., 432 F.3d
1356, 1361 (Fed. Cir. 2005). Rather, patentees frequently
“surrender more through amendment than may have been
absolutely necessary to avoid particular prior art.” Id.
That principle logically extends to amendments made to
overcome rejections under § 112. Cf. Biogen Idec, Inc. v.
GlaxoSmithKline LLC, 713 F.3d 1090, 1095–96 (Fed. Cir.
2013). Indeed, we have stated more generally that “[t]he
question is what a person of ordinary skill would under-
stand the patentee to have disclaimed during prosecution,
not what a person of ordinary skill would think the
14                                 AJINOMOTO CO., INC. v. ITC

patentee needed to disclaim during prosecution.” Tech.
Props. Ltd. LLC v. Huawei Techs. Co., 849 F.3d 1349, 1359
(Fed. Cir. 2017). A patentee must “be held to what he de-
clares during the prosecution of his patent,” because a con-
trary rule would undermine “[t]he public notice function of
a patent.” Springs Window Fashions LP v. Novo Indus.,
L.P., 323 F.3d 989, 995 (Fed. Cir. 2003).
    We conclude that this is a case where the applicants
surrendered more than may have been necessary. As dis-
cussed above, the best reading of the prosecution history is
that, to overcome the written-description and enablement
rejections, it might well have sufficed if the applicants had
narrowed their claims from alterations to the overall ex-
pression-regulation sequence to alterations to the pro-
moter.     But the applicants did not merely change
“expression regulation sequence” to “native promoter”;
they also changed “alteration” to “replacing.” Just as
“when different words are used in separate claims, they are
presumed to have different meanings,” Aspex Eyewear, Inc.
v. Marchon Eyewear, Inc., 672 F.3d 1335, 1349 (Fed. Cir.
2012), when a word is changed during prosecution, the
change tends to suggest that the new word differs in mean-
ing in some way from the original word.
     That inference is bolstered by the applicants’ remarks
accompanying the amendment. Those remarks effectively
equate “replacing the native promoter . . . with a more po-
tent promoter” in the amended claim with “chang[ing]” the
native promoter “by substitution with a more potent pro-
moter.” J.A. 5622. As we have already noted, Example 4,
described as involving “substitution” of a promoter, in-
volves removal of the entire native promoter and insertion
of a new promoter. ’665 patent, col. 11, line 5, through col.
12, line 46. The applicants’ remarks, understood in light of
the word choices and the specification, thus reinforce the
Commission’s conclusion that the new claim language does
not include mutagenesis of individual nucleotides.
AJINOMOTO CO., INC. v. ITC                                 15

    For those reasons, we affirm the Commission’s claim
construction and its finding that CJ’s earlier strains do not
infringe based on that claim construction.
                             III
    CJ, in its cross-appeal, challenges the Commission’s
determinations that CJ’s second later strain met the pro-
tein limitation, that both of CJ’s later strains met the re-
sistance limitation, and that claim 20 is not invalid for lack
of an adequate written description. We affirm the Commis-
sion as to all three issues.
     A determination of infringement or non-infringement,
whether literal or under the doctrine of equivalents, is a
finding of fact, reviewed here for substantial evidence.
Kinik Co. v. Int’l Trade Comm’n, 362 F.3d 1359, 1361 (Fed.
Cir. 2004). But a determination of the applicability or in-
applicability of prosecution history estoppel, which limits
the availability of the doctrine of equivalents, is a matter
of law, reviewed de novo. Spectrum Pharm., Inc. v. Sandoz
Inc., 802 F.3d 1326, 1337 (Fed. Cir. 2015). The determina-
tion that a patent claim did not lack adequate support in
the written description is a factual finding, reviewed for
substantial evidence. Rivera v. Int’l Trade Comm’n, 857
F.3d 1315, 1319 (Fed. Cir. 2017). Ajinomoto had to prove
infringement by a preponderance of the evidence, while CJ
had to prove invalidity by clear and convincing evidence.
See Motorola Mobility, LLC v. Int’l Trade Comm’n, 737
F.3d 1345, 1348 (Fed. Cir. 2013); Enercon GmbH v. Int’l
Trade Comm’n, 151 F.3d 1376, 1384 (Fed. Cir. 1998).
                              A
    The Commission found that CJ’s second later strain in-
fringed claim 20, which covers two alternatives of rele-
vance in this case—the claim 9 alternative and the claim
15 alternative. The infringement finding for CJ’s second
later strain does not rest on the claim 15 alternative,
which, in its protein limitation, requires a protein encoded
16                                 AJINOMOTO CO., INC. v. ITC

by a nucleotide sequence that hybridizes with the comple-
ment of SEQ ID NO:1 (the nucleotide sequence of the E.
coli yddG gene). The Commission did not find, and
Ajinomoto does not argue for, either literal or equivalents
infringement based on claim 15. The Commission found
infringement under the claim 9 alternative—specifically, it
found that the YddG protein encoded by the codon-random-
ized non-E. coli yddG gene of this strain is an equivalent of
SEQ ID NO:2 (the amino-acid sequence of the E. coli YddG
protein), as required by the protein limitation of claim 9.
    CJ challenges that finding on two grounds. Based on
an amendment to original claims made during prosecution,
CJ asserts that prosecution history estoppel bars
Ajinomoto from relying on the doctrine of equivalents to
meet the protein limitation. Separately, CJ asserts that
the non-E. coli YddG protein of CJ’s second later strain
cannot reasonably be found to be an equivalent of the
claimed E. coli YddG protein under the function-way-result
test for equivalence. We address those arguments in turn.
                             1
    Under the doctrine of prosecution history estoppel, “[a]
patentee’s decision to narrow his claims through amend-
ment may be presumed to be a general disclaimer of the
territory between the original claim and the amended
claim.” Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki
Co., 535 U.S. 722, 740 (2002). The Supreme Court has
specified three ways the patentee can rebut that presump-
tion, each of which, if established, means that “the amend-
ment cannot reasonably be viewed as surrendering a
particular equivalent.” Id. First, “[t]he equivalent may
have been unforeseeable at the time of the application.” Id.
Second, “the rationale underlying the amendment may
bear no more than a tangential relation to the equivalent
in question.” Id. Third, “there may be some other reason
suggesting that the patentee could not reasonably be
AJINOMOTO CO., INC. v. ITC                                   17

expected to have described the insubstantial substitute in
question.” Id. at 740–41.
     In this case, the relevant facts about what transpired
during prosecution are as follows. Claim 1 as originally
filed recited two alternative conditions for the claimed pro-
tein:
    a protein as defined in the following (A) or (B) in a
    cell of said bacterium:
    (A) a protein which comprises the amino acid se-
    quence shown in SEQ ID NO:2 in Sequence listing;
    (B) a protein which comprises an amino acid se-
    quence including deletion, substitution, insertion
    or addition of one or several amino acids in the
    amino acid sequence shown in SEQ ID NO:2 in Se-
    quence listing.
J.A. 5047. The examiner rejected that claim as anticipated
by a reference disclosing the E. coli “yfiK gene product” (i.e.,
the E. coli YfiK protein)—which differed from SEQ ID
NO:2 by deletion, substitution, insertion, or addition of sev-
eral amino acids and, therefore, did not come within the (A)
alternative but did come within the (B) alternative. J.A.
5378. In response, the applicants left the (A) alternative
alone but replaced the language following (B) with new lan-
guage: “a protein which comprises an amino acid sequence
that is encoded by a nucleotide sequence that hybridizes
with the nucleotide sequence of SEQ ID NO:1 under strin-
gent conditions.” J.A. 5609. 7

    7   As previously noted, claims 9 and 15 issued from
new claims added at the same time as this amendment.
See supra note 6. Claims 9 and 15 respectively contain the
same language as the (A) and (B) limitations in claim 1 af-
ter it was amended. Claim 20, the claim at issue, treats
18                                  AJINOMOTO CO., INC. v. ITC

      As an initial matter, CJ’s argument for prosecution his-
tory estoppel in this case involves an unusual circum-
stance. The infringement determination does not rest on
finding an equivalent of the new claim language—namely,
the (nucleotide) SEQ ID NO:1 language now in claim 15.
Rather, it rests on finding an equivalent of the (amino-acid)
SEQ ID NO:2 language now in claim 9, which was not itself
altered by the amendment at issue. That is, the original
claim provided two alternatives; only the second was mod-
ified by amendment; and only the first is asserted as the
basis for infringement by CJ’s second later strain. But we
need not reach Ajinomoto’s contention that, in this circum-
stance, prosecution history estoppel does not apply at all,
i.e., that there is not even a presumed (though rebuttable)
surrender of the asserted equivalent. The Commission did
not so rule, instead concluding that the “tangential rela-
tion” exception applied, so that Ajinomoto did not surren-
der the protein produced by the codon-randomized non-E.
coli yddG gene of CJ’s second later strain. J.A. 41–44. We
agree with that conclusion. 8
    In applying the “tangential relation” exception, we
“ask[] whether the reason for the narrowing amendment
was peripheral, or not directly relevant, to the alleged
equivalent.” Festo Corp. v. Shoketsu Kinzoku Kogyo Ka-
bushiki Co., 344 F.3d 1359, 1369 (Fed. Cir. 2003). “[T]he
inquiry into whether a patentee can rebut the Festo

claims 9 and 15 as alternatives in the same way that orig-
inal and amended claim 1 treated (A) and (B).
    8   CJ contends that Ajinomoto forfeited invocation of
the “tangential relation” exception because it did not in-
voke the exception before the ALJ or in its request for re-
view by the full Commission. CJ cites no authority that
barred the Commission from exercising discretion to raise
the issue and give the parties an adequate opportunity to
address it, as the Commission did here.
AJINOMOTO CO., INC. v. ITC                                19

presumption under the ‘tangential’ criterion focuses on the
patentee’s objectively apparent reason for the narrowing
amendment.” Id. Our cases require the patentee to show
that the way in which the alleged equivalent departs from
what the claim limitation literally requires is tangential to
the discernible objective reason for the narrowing amend-
ment. In that situation, there is no surrender of the equiv-
alent by that amendment.
    For instance, in Insituform Technologies, Inc. v. CAT
Contracting, Inc., the patent claimed a method of using a
vacuum to impregnate a flexible tube with resin. 385 F.3d
1360, 1362–63 (Fed. Cir. 2004). The claims were originally
rejected over a prior-art reference that disclosed a single
vacuum source located far away from the resin source. Id.
at 1369. The applicant amended the claim at issue to re-
quire a single vacuum source placed near the resin source.
See id. at 1368–70. The alleged equivalent used multiple
vacuum sources. Id. at 1369–70. We held that the “tan-
gential relation” exception applied, observing that the pur-
pose of the narrowing amendment was to distinguish the
invention from the prior art based on the location of the
vacuum source relative to the resin, not to limit the number
of vacuum sources. Id. at 1370.
    Similarly, in Regents of the University of California v.
Dakocytomation California, Inc., the patented method in-
volved using DNA testing to detect chromosomal abnor-
malities. 517 F.3d 1364, 1369–70 (Fed. Cir. 2008). The
claim at issue originally recited “disabling the hybridiza-
tion capacity of repetitive sequences” generally. Id. at
1377. The examiner rejected the claim over several prior-
art references, one of which disclosed disabling hybridiza-
tion using unique sequence probes. Id. at 1378. In re-
sponse, the applicants amended the claim to recite a
particular technique of disabling hybridization using block-
ing nucleic acids. Id. The parties stipulated that the added
“blocking nucleic acid” limitation was limited to human nu-
cleic acids, but the alleged equivalent used synthetic
20                                   AJINOMOTO CO., INC. v. ITC

nucleic acids. Id. at 1376. We concluded that the narrow-
ing amendment was tangential to how the equivalent dif-
fered from the literal claim limitation: “[I]n narrowing the
claim to overcome the prior art rejections, the focus of the
patentees’ arguments centered on the method of blocking—
not on the particular type of nucleic acid that could be used
for blocking.” Id. at 1378. Indeed, we noted, “the ‘nucleic
acid’ limitation was never narrowed during prosecution
and was not at issue in the office action rejecting the
claims,” and “none of the cited references concerned the
type of nucleic acid that could perform the blocking, or
mentioned the accused equivalent.” Id.
     Our decision in Intervet Inc. v. Merial Ltd. is to similar
effect. In that case, the patent claimed DNA constructs en-
coding a type of porcine circovirus. 617 F.3d 1282, 1284
(Fed. Cir. 2010). The claim at issue originally recited DNA
sequences from a group of thirteen open reading frames,
which are portions of a gene that encode a protein. Id. at
1285–86, 1291. The examiner rejected the claim over open
reading frames from another organism, noting that the
claim as written could cover open reading frames from any
organism. Id. at 1291. The applicants then amended the
claim to require that the open reading frames be “of porcine
circovirus type II.” Id. The alleged equivalent was a nu-
cleotide sequence that was over 99% homologous to one of
the claimed sequences. Id. at 1286. The “tangential rela-
tion” exception applied to that equivalent, we held, because
“[t]he rationale for the amendment was to narrow the
claimed universe of [open reading frames] down to those of
[porcine circovirus type II], and bore only a tangential re-
lation to the question of which DNA sequences are and are
not properly characterized as [porcine circovirus type II].”
Id. at 1292.
    This understanding of the “tangential relation” excep-
tion also underlies cases in which we have held that the
patentee failed to establish that a narrowing amendment
was tangential to the equivalent at issue. For example, in
AJINOMOTO CO., INC. v. ITC                                 21

Biagro Western Sales, Inc. v. Grow More, Inc., the claims at
issue, which claimed buffered phosphorus fertilizers, were
rejected over a prior-art reference disclosing a fertilizer
that was buffered only when diluted. 423 F.3d 1296, 1299,
1306 (Fed. Cir. 2005). In response, the applicant amended
the claims by adding the limitation “wherein said phospho-
rous-containing acid or salt thereof is present in an amount
of about 30 to about 40 weight percent,” explaining that the
fertilizer must be concentrated and that the amendment
specified a range for the concentration. Id. at 1305–06.
The alleged equivalent contained phosphorus compounds
at a concentration of between 59% and 62%. Id. at 1305.
We concluded that the “tangential relation” exception did
not apply, reasoning that it was “clear from the prosecution
history that the reason for adding the range limitation was
to overcome a prior art fertilizer that was not concen-
trated,” and “both the reason for the amendment and the
asserted equivalent relate to the concentration of the ferti-
lizer.” Id. at 1306.
    Here, we conclude, the Commission correctly concluded
that Ajinomoto had rebutted the Festo presumption be-
cause the amendment was tangential to the equivalent in
question. The objectively evident rationale for the amend-
ment was to limit the set of proteins within the claim’s
scope so that it no longer included the prior-art E. coli YfiK
protein and, more generally, no longer allowed as wide a
range of amino acid alterations (hence changes in the pro-
tein) as original alternative (B), which had allowed “dele-
tion, substitution, insertion or addition of one or several
amino acids in the amino acid sequence shown in SEQ ID
NO: 2.” J.A. 5047. The reason for the amendment had
nothing to do with choosing among several DNA sequences
in the redundant genetic code that correspond to the same
protein. Indeed, it is undisputed that the non-E. coli YddG
protein produced without codon randomization remains
within the literal claim scope even after the amendment
and that the non-E. coli YddG protein is identical whether
22                                 AJINOMOTO CO., INC. v. ITC

produced from the codon-randomized or the non-codon-ran-
domized version of the non-E. coli yddG gene.
    Accordingly, the reason for the narrowing amendment
—limiting the amino-acid makeup of the proteins included
in one of the alternatives covered by the claim—is unre-
lated to differences among the several DNA sequences that
encode a given protein. Under Festo’s express provision for
a “tangential relation” exception to the presumption as to
the scope of surrender by amendment during prosecution,
this conclusion about the reason for the amendment at is-
sue does not “ignore[] how the patentee deliberately elected
to narrow the claims” (Dissent at 6); rather, it identifies
what was not within the “scope disclaimed” (id. at 7), so
that it may be proved to infringe by satisfying the other
requirements of the doctrine of equivalents. We therefore
reject CJ’s contention that prosecution history estoppel
precludes the Commission’s finding of infringement under
the doctrine of equivalents for the second later strain.
                             2
     CJ’s second challenge to the Commission’s finding re-
garding the protein limitation and CJ’s second later strain
is that the non-E. coli YddG protein of CJ’s second later
strain could not properly be found to be equivalent to the
claimed E. coli YddG protein. Ajinomoto presented its
equivalence case within the function-way-result frame-
work, under which a product or process that does not liter-
ally satisfy a claim limitation may nevertheless infringe “if
it performs substantially the same function in substan-
tially the same way to obtain the same result.” Duncan
Parking Techs., Inc. v. IPS Grp., Inc., 914 F.3d 1347, 1362
(Fed. Cir. 2019) (quoting Graver Tank & Mfg. Co. v. Linde
Air Prods. Co., 339 U.S. 605, 608 (1950)). We conclude that
substantial evidence supports the Commission’s finding of
equivalence under that test.
   As to “function”: Ajinomoto’s expert, Dr. Gregory
Stephanopoulos, testified that both E. coli and non-E. coli
AJINOMOTO CO., INC. v. ITC                                23

YddG proteins function as “export protein[s] that actively
export[] aromatic L-amino acids and aromatic L-amino acid
analogs” out of the bacterial cell. J.A. 545–46. A 2007 ar-
ticle by Doroshenko et al. similarly explains that both pro-
teins are involved in exporting aromatic compounds. See
J.A. 9451. And Dr. So Young Kim, a CJ employee, testified
during a deposition that both proteins would be expected
to have similar functions based on similarities in the or-
ganisms from which they are derived. See J.A. 10641 (“Q.
Based on the similarity between E. coli and [the non-E. coli
organism], you would suspect that the protein coded by the
[non-E. coli] yddG gene would be useful for whatever it
does in E. coli, right? A. I think that way too.”). Thus, the
Commission’s finding that both proteins perform the same
function is supported by substantial evidence.
    As to “way”: Dr. Stephanopoulos testified that the two
proteins are 85% to 95% identical in structure. J.A. 546.
This range was corroborated by a 2002 article by Santivi-
ago et al., which indicates an 85% structural identity, see
J.A. 9444, and the Doroshenko article, which notes a 95%
identity in amino-acid sequence, J.A. 9451. On the record
here, substantial evidence supports a finding that the two
proteins perform the membrane-transport function in sub-
stantially the same way. See also Mylan Institutional LLC
v. Aurobindo Pharma Ltd., 857 F.3d 858, 868 (Fed. Cir.
2017) (noting that the “function” and “way” inquiries often
overlap or are synonymous).
    As to “result”: Dr. Stephanopoulos testified that, by ex-
porting L-tryptophan out of the bacterial cell, both proteins
increase the ability of bacteria to “produce and accumulate
L-tryptophan.” See J.A. 547. That statement is supported
by CJ’s fermentation data, which showed that strains con-
taining the E. coli yddG gene but with a stronger promoter,
and strains containing the non-E. coli yddG gene with a
strong promoter, both showed greater production of L-tryp-
tophan than did strains containing the E. coli yddG gene
with the native promoter. See J.A. 7957; J.A. 10053. In
24                                   AJINOMOTO CO., INC. v. ITC

other words, enhancing the expression of either the E. coli
or the non-E. coli yddG gene had the effect of increasing
production of L-tryptophan, which supports an inference
that the proteins encoded by those genes both result in in-
creased L-tryptophan production. The Commission’s find-
ings regarding result are supported by substantial
evidence.
    CJ argues that the two proteins do not perform the
same function in the same way because the E. coli YddG
protein exports aromatic L-amino acids such as L-trypto-
phan, whereas the non-E. coli YddG protein exports a dif-
ferent compound—namely, paraquat (also known as
methyl viologen). But a 2012 article by Liu et al. explains
that YddG proteins can export both types of compounds.
See J.A. 9751 (“YddG is classified as aromatic amino
acid/paraquat exporter . . . .”). And Dr. Stephanopoulos, re-
lying on the Santiviago article, testified that the non-E. coli
YddG protein must be coupled to the OmpD protein, which
is present in the non-E. coli organism but not E. coli, to
export paraquat. J.A. 762 (citing J.A. 9439). The fact that
the non-E. coli YddG protein may be involved in exporting
compounds other than L-tryptophan in the non-E. coli or-
ganism does not undermine the Commission’s well-sup-
ported finding that the non-E. coli YddG protein is involved
in exporting L-tryptophan in the E. coli bacteria used by
CJ.
                              B
    CJ challenges the Commission’s finding of infringe-
ment of both later strains on one additional ground. The
Commission found that CJ’s later strains met the re-
sistance limitation. CJ argues that substantial evidence
AJINOMOTO CO., INC. v. ITC                                 25

does not exist to support that finding. 9 We reject that ar-
gument.
    Several pieces of evidence indicate that, as a general
matter, enhancing the activity of the YddG protein in-
creases bacteria’s resistance to L-tryptophan. Table 1 of
the ’655 patent shows that E. coli bacteria with multiple
copies of the yddG gene introduced through plasmids
demonstrated better growth on a tryptophan substrate,
and thus more resistance, than unmodified E. coli bacteria.
See ’655 patent, col. 9, lines 50–65 (bottom row, compare
column “pUC19” (-) with column “pYDDG1” (+)). Similarly,
the Doroshenko article, mentioned above, describes an ex-
periment in which E. coli bacteria with a stronger promoter
preceding the yddG gene demonstrated enhanced re-
sistance to L-tryptophan. See J.A. 9455 (row DV036, col-
umn DL-5-f-Trp).
    CJ’s fermentation data, mentioned above, also provides
direct evidence that CJ’s later strains have increased re-
sistance to L-tryptophan. That data shows a greater vol-
ume of tryptophan with both of CJ’s later strains than with
unmodified E. coli bacteria. See J.A. 7957 (first later
strain: middle table, row F4, column “Volume produced”);
J.A. 10053 (second later strain: row “Product (g)” toward
middle of table). Dr. Stephanopoulos indicated that a
strain’s ability to overproduce L-tryptophan necessarily
meant that the strain had increased resistance to L-trypto-
phan. See J.A. 1448 (“[I]f that product feedback inhibits its
own synthesis, clearly, this is not going to work.”); see also

    9     CJ does not challenge the finding that CJ’s first
later strain meets the protein limitation of the claim 15 al-
ternative of claim 20. Specifically, CJ’s first later strain
uses a non-E. coli yddG gene without codon randomization,
which hybridizes with the complement of SEQ ID NO:1
(i.e., the nucleotide sequence of the E. coli yddG gene), and
thus falls within the literal scope of claim 15.
26                                 AJINOMOTO CO., INC. v. ITC

J.A. 521 (stating that bacteria that “exhibit enhanced re-
sistance to an aromatic L-amino acid or an aromatic L-
amino acid analog” also “overproduce the corresponding ar-
omatic L-amino acid analog”).
     CJ’s objections to the sufficiency or even relevance of
this evidence are unpersuasive. CJ points out that the bac-
teria used to generate the data in Table 1 of the ’655 patent
contained plasmids with more than the two copies of the
yddG gene in CJ’s later strains. See J.A. 1229. The Doro-
shenko article, however, indicates that enhancing the ac-
tivity of even a single copy of the yddG gene can increase
resistance to L-tryptophan. CJ responds that the strain
studied in Doroshenko used a strong λPL promoter, while
CJ’s later strains use relatively weaker non-E. coli native
yddG, rmf, and rhtB promoters. See J.A. 9454. But Dr.
Stephanopoulos testified that at least the rmf promoter in
both of CJ’s later strains also is more potent than the na-
tive E. coli yddG promoter. J.A. 554. Thus, even if CJ is
correct that its later strains do not contain tandem promot-
ers, the Commission could reasonably infer that the pro-
moters used in CJ’s later strains enhance the activity of the
yddG genes relative to unmodified E. coli bacteria and
thereby increase those strains’ resistance to L-tryptophan.
    CJ also cites Ajinomoto’s 2002 Progress Report as evi-
dence that enhancing a single copy of the yddG gene is in-
sufficient to enhance resistance to L-tryptophan. That
report states that an experiment using “only one copy” of
the yddG gene with a PL promoter “does not correctly
model[]” an earlier experiment using a “moderate-copy-
number” plasmid with the yddG gene, which had shown a
“positive effect” of the yddG gene on tryptophan produc-
tion. J.A. 10268. No more need be inferred from the report
than that enhancing a single copy of the yddG gene in-
creases resistance to L-tryptophan less than using a
greater number of copies. The Commission did not need to
infer that enhancing a single copy as in CJ’s later strains
does not enhance resistance at all.
AJINOMOTO CO., INC. v. ITC                                27

    Further, CJ asserts that the increased production of L-
tryptophan, and thus the enhanced resistance to L-trypto-
phan, observed in its later strains could be attributable to
the presence of other genetic mutations rather than to in-
creased YddG protein activity alone. See J.A. 442. But the
claims require only that the protein “has the activity to
make the bacterium resistant” to L-tryptophan, not that
the protein be the sole cause of the bacterium’s enhanced
resistance to L-tryptophan. See ’655 patent, col. 22, lines
57–59. Considering the already-mentioned evidence that
the YddG protein generally has the effect of increasing re-
sistance to L-tryptophan, the Commission had substantial
evidence from which to find that it was more likely than
not that increased activity of the YddG protein at least
partly contributed to the enhanced resistance of CJ’s later
strains.
                             C
     CJ’s final contention in its cross-appeal seeks reversal
of the Commission’s rejection of CJ’s invalidity challenge to
claim 20. CJ argues that substantial evidence does not
support the Commission’s finding that CJ did not prove
lack of an adequate written description for the genus of
“more potent promoter[s]” recited in claims 9 and 15 and,
by incorporation, in claim 20. We reject CJ’s argument.
    “[A] sufficient description of a genus . . . requires the
disclosure of either a representative number of species fall-
ing 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 ge-
nus.” Ariad Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336,
1350 (Fed. Cir. 2010) (en banc). The Commission found
both that the ’655 patent discloses a representative number
of species of more potent promoters and that there are
structural features common to the genus of more potent
promoters. Both of those findings are supported by
28                                  AJINOMOTO CO., INC. v. ITC

substantial evidence, and they suffice to uphold the Com-
mission’s rejection of CJ’s written-description challenge.
                              1
    As to a representative number of species, we have rec-
ognized that the amount of disclosure necessary to satisfy
the written-description requirement “will necessarily vary
depending on the context,” considering such facts as “the
existing knowledge in the particular field, the extent and
content of the prior art, the maturity of the science or tech-
nology,” and “the predictability of the aspect at issue.” Ar-
iad, 598 F.3d at 1351 (quoting Capon v. Eshhar, 418 F.3d
1349, 1359 (Fed. Cir. 2005)). In some circumstances, we
have added, “a patentee may rely on information that is
‘well-known in the art’ for purposes of meeting the written
description requirement,” because “the specification is
viewed from the perspective of one of skill” in the relevant
art. Bos. Sci. Corp. v. Johnson & Johnson, 647 F.3d 1353,
1366 (Fed. Cir. 2011).
     The ’655 patent discloses four examples of “potent pro-
moters”: “PL promoter of lambda phage,” the “lac pro-
moter,” the “trp promoter,” and the “trc promoter.” ’655
patent, col. 6, lines 21–24. The patent also cites the 1986
article by Deuschle et al. as disclosing “examples of potent
promoters” and “[m]ethods for [the] evaluation [of] the
strength of promoter[s].” Id., col. 6, lines 16–21. That ar-
ticle provides data about the relative strength of fourteen
promoters and describes a general methodology for deter-
mining promoter strength in E. coli bacteria. J.A. 6174–
77. This evidence supports the Commission’s finding that
“enhancing promoter activity was well-known” and that a
skilled artisan “would have been able to identify more po-
tent promoters by employing common tools for measuring
RNA transcription.” J.A. 46.
    The ’655 patent also makes clear that its invention was
“identifying the yddG gene encoding a membrane protein”
and discovering that the gene “conferred on a
AJINOMOTO CO., INC. v. ITC                                29

microorganism resistance to phenylalanine and several
amino acid analogues” when the gene was amplified or its
expression enhanced, see ’655 patent, col. 2, lines 46–57,
not the well-known techniques for performing the amplifi-
cation or expression enhancement, see id., col. 5, line 57,
through col. 6, line 33. We have explained that the repre-
sentative-species inquiry is directed to whether the inven-
tor “has truly invented the genus” as opposed to “a research
plan, leaving it to others to explore the unknown contours
of the claimed genus.” AbbVie Deutschland GmbH & Co.,
KG v. Janssen Biotech, Inc., 759 F.3d 1285, 1300 (Fed. Cir.
2014). Here, the genus of more potent promoters was al-
ready well explored in the relevant art by the time of the
’655 patent’s invention. In these circumstances, the Com-
mission permissibly found in the specification, read in light
of the background knowledge in the art, a representative
number of species for the genus of more potent promoters.
                             2
     As to a common structural feature, the Commission
found that a skilled artisan could “identify more potent
yddG promoters given the well-known link between con-
sensus sequence and promoter strength,” i.e., that promot-
ers having fewer departures from a “consensus sequence”
in a promoter are generally stronger than promoters with
more departures from such a sequence. J.A. 46. 10 Substan-
tial evidence supports that finding. For instance, a 1983
article by Hawley and McClure describes a study demon-
strating that most “mutations that decrease initiation fre-
quency also decrease the homology of the promoter to the
consensus sequence, while up-mutations increase the

    10 The consensus sequence is a specific nucleotide se-
quence that appears in the promoters associated with
many different genes in the genome of a particular organ-
ism. In E. coli, the consensus sequence has two parts:
TTGACA at the -35 region and TATAAT at the -10 region.
30                                 AJINOMOTO CO., INC. v. ITC

homology in” most instances. J.A. 6237. Similarly, a 1986
article by Horwitz and Loeb explains that “mutations that
increase transcription, ‘up mutations,’ usually increase ho-
mology with the consensus sequence and spacing,” while
“mutations that decrease transcription, ‘down mutations,’
usually decrease homology with the consensus sequence
and spacing.” J.A. 6251.
    CJ disputes that similarity to the consensus sequence
defines a common structural feature, citing several articles
as indicating that a promoter closer to the consensus se-
quence will not always be stronger than one farther from
that sequence. For instance, a 1998 article by Jensen and
Hammer reports that a pattern observed in another organ-
ism—that “the relatively strong promoters were the perfect
ones,” i.e., those closer to the consensus sequence—“did not
hold true for E. coli: here the promoters which had either
an error in the consensus sequence or a shorter spacer were
relatively strong.” J.A. 9149. Moreover, a 1985 article by
Aoyama and Takanami states that similarity to the con-
sensus sequence “is still not enough to predict the site and
strength of promoter from a given sequence,” J.A. 6215,
and a 1999 book edited by Fernandez and Hoeffler notes
that “the strongest promoters in E. coli do not necessarily
adhere to the consensus sequence,” J.A. 9113.
    CJ’s argument both assumes too strict a legal standard
and reads too much into its cited references. Adequate
written description does not require a perfect correspond-
ence between the members of the genus and the asserted
common structural feature; for a functionally defined ge-
nus like the one at issue here, we have spoken more mod-
estly of a “correlation between structure and function.”
Ariad, 598 F.3d at 1350 (emphasis added). In any event,
CJ’s evidence at most establishes that, starting with the
consensus sequence, deviations from that sequence do not
always decrease promoter strength, at least in E. coli. But
the genus at issue here is “more potent promoter[s]” than
the native promoter, not less potent promoters than the
AJINOMOTO CO., INC. v. ITC                                 31

consensus sequence. And the Commission had substantial
evidence from which to find that, starting from the native
E. coli yddG promoter, deviations toward the consensus se-
quence generally increase promoter strength.
    The cases cited by CJ in which we have held genus
claims to lack an adequate written description are inappo-
site. In Boston Scientific, the specification contained “no
examples of macrocyclic lactone analogs of rapamycin” (the
claimed genus) and essentially “no guidance on how to
properly determine whether a compound is a macrocyclic
lactone analog of rapamycin.” 647 F.3d at 1364. In AbbVie,
there was “no evidence to show any described antibody to
be structurally similar to, and thus representative of,” an
antibody accused of coming within the claim, nor was there
“evidence to show whether one of skill in the art could make
predictable changes to the described antibodies to arrive at
other types of antibodies such as” the accused antibody.
759 F.3d at 1301. And in Regents of the University of Cali-
fornia v. Eli Lilly & Co., the specification described “a pro-
cess for obtaining human insulin-encoding cDNA” (such
cDNA required by the claim at issue) but not any “sequence
information indicating which nucleotides constitute hu-
man cDNA” or “further information in the patent pertain-
ing to that cDNA’s relevant structural or physical
characteristics.” 119 F.3d 1559, 1567 (Fed. Cir. 1997).
Here, by contrast, the ’655 patent expressly provides four
examples of “more potent promoters,” and the Commission
supportably found that a skilled artisan could make rela-
tively predictable changes to the native promoter to arrive
at a more potent promoter.
                             IV
    For the foregoing reasons, we affirm the Commission’s
decision.
    No costs.
                        AFFIRMED
 United States Court of Appeals
     for the Federal Circuit
             ______________________

AJINOMOTO CO., INC., AJINOMOTO HEARTLAND
                   INC.,
                 Appellants

                       v.

    INTERNATIONAL TRADE COMMISSION,
                Appellee

CJ CHEILJEDANG CORP., CJ AMERICA, INC., PT
         CHEIJEDANG INDONESIA,
               Intervenors

--------------------------------------------

CJ CHEILJEDANG CORP., CJ AMERICA, INC., PT
         CHEIJEDANG INDONESIA,
                Appellants

                       v.

    INTERNATIONAL TRADE COMMISSION,
                Appellee

AJINOMOTO CO., INC., AJINOMOTO HEARTLAND
                    INC.,
                 Intervenors
           ______________________

              2018-1590, 2018-1629
             ______________________
2                                     AJINOMOTO CO., INC. v. ITC

   Appeals from the United States International Trade
Commission in Investigation No. 337-TA-1005.
                ______________________
DYK, Circuit Judge, concurring-in-part and dissenting-in-
part.
    I join the majority as to parts I, II, III (B) (as it relates
to Strain A, corresponding to the “first later strain” in the
majority) and (C). I respectfully dissent from the majority’s
conclusion that Ajinomoto successfully rebutted the pre-
sumption of prosecution history estoppel under the tangen-
tial exception as to respondent’s recombinant bacterial
Strain B, which corresponds to the “second later strain” re-
ferred to by the majority, see Majority Op. at 15.
     On appeal, the only asserted claim is claim 20 of U.S.
Patent No. 7,666,655 (’655 patent). It covers “[a] method for
producing an [amino acid,] which comprises cultivating the
bacterium according to any one of claims 9[, or 15].” ’655
patent, col. 24, ll. 4–6. In relevant part, claim 9 covers a
recombinant bacteria having a “protein consist[ing] of the
amino acid sequence of SEQ ID NO: 2.” Id. col. 22, ll. 56–
57. This corresponds to the amino acid sequence of E. coli
YddG protein (a membrane-bound protein involved in the
cellular export of aromatic amino acids). Strain B does not
literally infringe claim 9 because it produces a protein with
an amino acid sequence that differs from SEQ ID NO: 2.
See J.A. 37. Instead, Ajinomoto asserts infringement under
the doctrine of equivalents, arguing that Strain B’s non-E.
coli YddG protein is equivalent to the E. coli YddG protein
(SEQ ID NO: 2) in claim 9.
   The prosecution history shows that claim language was
amended such that the accused equivalent is excluded. 1

    1   Everyone agrees that the relevant prosecution his-
tory for the analysis focuses on the language in claim 1,
AJINOMOTO CO., INC. v. ITC                                   3

Originally, the claim language covered variations of SEQ
ID NO: 2, stating that it covered “deletion, substitution, in-
sertion or addition of one or several amino acids” of SEQ ID
NO: 2. J.A. 5609. During prosecution, the examiner re-
jected the claim as anticipated by prior art (Livshits) that
disclosed a recombinant E. coli bacteria producing YfiK
protein, encoded by the yfiK gene, which had an amino acid
sequence different from the SEQ ID NO: 2 but still satis-
fied the claim limitations. J.A. 5378. Specifically, the ex-
aminer stated “Livshits et al. anticipate claims 1-4 because
the yfiK gene product can be considered a protein” meeting
the claim limitation above. Id. In response to this rejection,
the patentee narrowed the claim language (which now ap-
pears in claim 15) to only cover protein variants differing
from SEQ ID NO: 2 when they are “encoded by a nucleotide
sequence that hybridizes with the nucleotide sequence of
SEQ ID NO: 1[, the E. coli yddG gene,] under stringent con-
ditions comprising 60°C, 1 x SSC, 0.1% SDS.” J.A. 5609;
see ’655 patent, col. 23, ll. 19–22. 2 The patentee stated that
“[i]n view of this amendment, Livshits et al no longer an-
ticipates the claimed invention.” J.A. 5617.
    The majority assumes that prosecution history estop-
pel presumptively applies in this case. Majority Op. at 18.
But the majority concludes that Ajinomoto is still not pre-
cluded from arguing infringement under the doctrine of
equivalents based on the tangential exception.
   We have consistently described this exception as “very
narrow.” Integrated Tech. Corp. v. Rudolph Techs., Inc.,
734 F.3d 1352, 1358 (Fed. Cir. 2013) (quoting Cross Med.

which was later utilized in claims 9 and 15 that were added
later in prosecution.
    2    Strain B does not literally infringe claim 15 be-
cause the non-E. coli YddG protein’s encoding nucleotide
sequence does not hybridize with SEQ ID NO: 1 under the
claimed conditions.
4                                  AJINOMOTO CO., INC. v. ITC

Prods., Inc. v. Medtronic Sofamor Danek, Inc., 480 F.3d
1335, 1342 (Fed. Cir. 2007)). Under this exception, the
question is “whether the reason for the narrowing amend-
ment was peripheral, or not directly relevant, to the alleged
equivalent.” Festo Corp. v. Shoketsu Kinzoku Kogyo Ka-
bushiki Co., 344 F.3d 1359, 1369 (Fed. Cir. 2003) (en banc).
The inquiry “focuses on the patentee’s objectively apparent
reason for the narrowing amendment,” which “should be
discernible from the prosecution history record.” Id. (em-
phasis added). In my view the “reason for the narrowing
amendment” in this case is directly related to the equiva-
lent.
    Originally, the claim covered proteins with amino acid
sequence variations from SEQ ID NO: 2, which would have
included the non-E. coli YddG protein at issue here. The
examiner rejected the original claim based on anticipating
prior art, and the patentee responded with a narrowing
amendment. Instead of continuing to define the covered
proteins in terms of amino acid sequence variations from
SEQ ID NO: 2, 3 the patentee deliberately chose to redefine
the claimed proteins in terms of the ability of their encod-
ing nucleotide sequences to hybridize with SEQ ID NO: 1
under the claimed conditions. The amended claim lan-
guage excluded the prior art protein (Livshits) because it
was made based on a nucleotide sequence that did not meet
the newly added hybridization requirement. The accused
equivalent is similarly not covered by the amended claims
because it is produced based on an encoding nucleotide se-
quence that does not hybridize with SEQ ID NO: 1 under
the claimed conditions. Thus, I do not see how the reason

    3    The patentee later added claim language that cov-
ered other, more limited, variations from the amino acid
sequence of SEQ ID NO: 2, by “one to five amino acids,” but
that claim language is not at issue here. ’655 Patent, col.
21, l. 42.
AJINOMOTO CO., INC. v. ITC                                  5

for the narrowing amendment is tangential to the accused
equivalent.
    Ajinomoto argues that “[t]o the extent anything was
given up during prosecution, it was the YfiK protein [dis-
closed in Livshits] . . . and, possibly, other non-YddG pro-
teins.” Ajinomoto Response & Reply Br. at 41 (emphasis
omitted). Ajinomoto’s argument that prosecution history
estoppel would only apply to the specific prior art protein
(or possibly other non-YddG proteins) is not only incon-
sistent with how the patentee amended the claims but also
our caselaw. Specifically, “[Ajinomoto’s] representations
convey to the public that it was relying on [the claimed hy-
bridization requirement] to overcome the prior art. The
public is entitled to rely on those representations.” Inte-
grated Tech., 734 F.3d at 1359. “The fact that the inventors
may have thought after the fact that they could have relied
on other distinctions in order to defend their claims[, e.g.,
by limiting the claim to only YddG-type proteins,] is irrele-
vant and speculative . . . .” Schwarz Pharma, Inc. v. Pad-
dock Labs., Inc., 504 F.3d 1371, 1377 (Fed. Cir. 2007). “It is
not relevant to the determination of the scope of the sur-
render that the applicant did not need to amend the claims”
in the way that it chose to do so “in order to overcome the
prior art.” Lucent Techs., Inc. v. Gateway, 525 F.3d 1200,
1218 (Fed. Cir. 2008) (citing Norian Corp v. Stryker Corp.,
432 F.3d 1356, 1361–62 (Fed. Cir. 2005)).
    The majority adopts a slightly different version of
Ajinomoto’s untenable argument. The majority concludes
that the “objectively evident rationale” for the narrowing
amendment was “to limit the set of proteins within the
claim’s scope so that it no longer included the prior-art
[protein], and, more generally, no longer allowed as wide a
range of amino acid alterations.” Majority Op. at 21 (em-
phasis in original). The majority reasons that because
Strain A, which makes the same protein as Strain B but
with a different nucleotide sequence, literally infringes
claim 15, somehow Strain B should be found to infringe
6                                   AJINOMOTO CO., INC. v. ITC

claim 9 under the doctrine of equivalents. It theorizes that
“[t]he reason for the amendment had nothing to do with
choosing among several DNA sequences in the redundant
genetic code that correspond to the same protein” (i.e., the
accused equivalent). Id. at 21. In this way, the majority
concludes that the reason for the narrowing amendment—
limiting the range of proteins covered by the claim—is un-
related to the way in which the equivalent departs from the
literal claim limitation—differences among the several
DNA sequences that encode a given protein.
    The problem with the majority’s analysis is that it ig-
nores how the patentee deliberately elected to narrow the
claims. The anticipating prior art disclosed E. coli YfiK pro-
tein, encoded by the yfiK gene, and this prior art was
avoided by narrowing the claim to only cover certain encod-
ing nucleotide sequences. That rationale is directly related
to the accused equivalent, which does not infringe because
it does not use a covered encoding nucleotide sequence. In
other words, the rationale for the narrowing amendment
(avoiding a prior art protein based on its encoding nucleo-
tide sequence that does not meet the newly claimed hybrid-
ization requirement) directly relates to the accused
equivalent (a protein made by an encoding nucleotide se-
quence that does not meet the newly claimed hybridization
requirement).
    The cases cited by the majority also do not support its
approach. In Insituform Technologies, Inc. v. CAT Con-
tracting, Inc., 385 F.3d 1360 (Fed. Cir. 2004), and Regents
of the University of California v. Dakocytomation Califor-
nia, 517 F.3d 1364 (Fed. Cir. 2008), multiple limitations
were added with a narrowing amendment but only one of
those limitations related to what was taught in the prior
art cited by the examiner. We held that the equivalent to
the other limitation was permitted under the tangential ex-
ception. In Insituform, the rationale for the amendment
was to limit the location of the vacuum source, not the num-
ber of vacuum sources (the accused equivalent). 385 F.3d
AJINOMOTO CO., INC. v. ITC                                 7

at 1370. In Regents, the rationale for the amendment was
to limit the type of blocking method, not the particular
types of nucleic acids that could be used in that method (the
accused equivalent). 517 F.3d at 1378. These cases cannot
be read as allowing the patentee to recapture scope dis-
claimed in order to distinguish the prior art, which is ex-
actly what the patentee is attempting to do here. The
anticipating prior art cited by the examiner specifically
taught a protein made by a particular gene, and the pa-
tentee narrowed the claim to avoid this prior art by limit-
ing the claim to only cover proteins made by particular
nucleotide sequences (which neither the prior art nor
Strain B have).
    Our decision in Intervet Inc. v. Merial Ltd., 617 F.3d
1282 (Fed. Cir. 2010), is also inapposite. There, the claims
were “narrow[ed from] the claimed universe of [nucleotide
sequences] down to those of [porcine circovirus type II
(‘PCV-2’)],” but there remained the tangential “question of
which DNA sequences are and are not properly character-
ized as PCV-2.” Id. at 1292 (emphasis added). In contrast,
there is no question here of which nucleotide sequences are
“properly characterized” as being included under the claim
language—only those that hybridize with SEQ ID NO: 1
“under stringent conditions comprising 60°C, 1 x SSC,
0.1% SDS” are covered. J.A. 5609. There is no dispute that
CJ’s bacterial strain does not satisfy this specific and un-
ambiguous limitation.
    In my view the tangential exception cannot apply. The
equivalent is directly related to the reason for the amend-
ment—to exclude those proteins made by an encoding nu-
cleotide sequence that does not hybridize with SEQ ID
NO: 1 under the specified conditions. I respectfully dissent
from the majority’s contrary conclusion.