Court Opinion

ID: 4362643
Source: CourtListenerOpinion
Date Created: 2019-01-29 16:01:14.159864+00
Date Added: 2024-06-11T14:48:39.613991
License: Public Domain

NOTE: This disposition is nonprecedential.

  United States Court of Appeals
      for the Federal Circuit
                ______________________

    IN RE: IKEDA FOOD RESEARCH CO., LTD.,
                     Appellant
              ______________________

                      2017-2624
                ______________________

    Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. 12/851,668.
                  ______________________

               Decided: January 29, 2019
                ______________________

   THOMAS H. JENKINS, Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP, Washington, DC, argued for
appellant. Also represented by MICHAEL PAUL BARKER,
MICHAEL LIU SU, Palo Alto, CA.

   SARAH E. CRAVEN, Office of the Solicitor, United
States Patent and Trademark Office, Alexandria, VA,
argued for appellee Andrei Iancu. Also represented by
THOMAS W. KRAUSE, KAKOLI CAPRIHAN.
                ______________________

Before WALLACH, TARANTO, and HUGHES, Circuit Judges.
WALLACH, Circuit Judge.
    Appellant Ikeda Food Research Co., Ltd. (“Ikeda”) ap-
peals a decision on appeal of the U.S. Patent and Trade-
2                       IN RE: IKEDA FOOD RESEARCH CO., LTD.

mark Office’s (“USPTO”) Patent Trial and Appeal Board
(“PTAB”) in an ex parte reexamination affirming an
examiner’s rejection of, inter alia, claims 22−23 (“the
Challenged Claims”) of U.S. Patent Application No.
12/851,668 (“the ’668 application”) (J.A. 837–99) as obvi-
ous pursuant to 35 U.S.C. § 103(a) (2006). 1 See In re
Ikeda Food Research Co., No. 2015-002637 (P.T.A.B. July
28, 2017) (J.A. 2–17). We have jurisdiction pursuant to 28
U.S.C. § 1295(a)(4)(A) (2012). We affirm.
                       BACKGROUND
                  I. The ’668 Application
    Entitled “Coenzyme-Binding Glucose Dehydrogenase,”
the ’668 application generally relates to a “convenient”
method for patients to regularly measure and monitor
their blood glucose, i.e., blood sugar, “and a means for
controlling the blood sugar level . . . which can be utilized
not only in a hospital but also at home.” J.A. 839. The
enzymatic method employs blood glucose “biosensors,” 2

    1   Congress amended § 103 when it enacted the
Leahy-Smith America Invents Act (“AIA”). Pub. L. No.
112-29, § 3(c), 125 Stat. 284, 287 (2011). However, be-
cause the ’668 application never contained a claim having
an effective filing date on or after March 16, 2013 (the
effective date of the statutory changes enacted in 2011), or
a reference under 35 U.S.C. §§ 120, 121, or 365(c) to any
patent or application that ever contained such a claim,
the pre-AIA § 103 applies. See id. § 3(n)(1), 125 Stat. at
293.
    2   Biosensors commonly rely on enzymes, with the
most commonly used enzymes being those that catalyze
(cause or accelerate) oxidation-reduction reactions. See
J.A. 356. Such enzymes include glucose oxidases (“GOx”)
and glucose dehydrogenases (“GDH”), the latter of which
includes enzymes that use nicotinamide adenine dinucleo-
IN RE: IKEDA FOOD RESEARCH CO., LTD.                      3

J.A. 839, as “an important marker for diabetes,” J.A. 838.
The ’668 application describes prior art methods that use
“a biosensor employing a [GDH]” and exhibit various
disadvantages, such as “high background noise” that
leads to erratic readings “due to a level of residual oxy-
gen,” and “a complicated reaction system” that is “expen-
sive.” J.A. 839–40. The ’668 application purports to
improve upon the prior art by claiming use of, inter alia, a
specific enzyme: a “flavin”-dependent GDH (“FAD-GDH”)
designated as Enzyme Commission (“E.C.”) 3 1.1.99.10,
J.A. 890, whose “relative reactivity” (or “substrate speci-
ficity”), was found to exhibit “high activity” on glucose,
and “low activity” on the seventeen other substrates
tested, including maltose, see J.A. 864−65.
    The “objective of the invention is to provide a novel
[GDH] which exhibits an excellent substrate-recognizing
ability toward glucose and which has low activity on
maltose,[4] and also to provide a method for producing the
same and a microorganism having an ability of producing
the same.” J.A. 841. The newly-discovered “coenzyme-
binding [GDH] has [the] ability of catalyzing a reaction
for oxidizing glucose, especially a hydroxyl group in the

tide (“NAD(P)+”) or pyrroloquinoline quinone (“PQQ”) as
an expensive and unstable cofactors. See J.A. 356,
838−40, 843.
    3   E.C. numbers are promulgated by the Enzyme
Commission, J.A. 176, and provide a common classifica-
tion scheme for enzymes based on the chemical reactions
they catalyze, see J.A. 7−8.
    4   Maltose is “a sugar produced by the breakdown of
starch,” and enzymes that have intrinsic enzymatic
activity towards maltose, such as PQQ-GDH, were later
reported to pose high risks for patients on infusion drugs.
J.A. 269; see J.A. 840−41 (excerpts from another utility
patent application).
4                       IN RE: IKEDA FOOD RESEARCH CO., LTD.

[first] position of glucose, in the presence of an electron
acceptor.” J.A. 842. To obtain the FAD-GDH enzyme, a
microorganism (or microbe) containing the enzyme is first
“cultured,” and the enzyme is “recovered from the culture
by means of an ordinary protein purification method.”
J.A. 864, 869. The ’668 application recounts the purified
enzyme’s activity to maltose as 1.4%, relative to its activi-
ty to glucose, which is regarded as 100%. See J.A. 882
(Table 1); see also J.A. 845 (describing the graphical data
quantifying various activity of the coenzyme-binding
GDHs). Accordingly, the purified FAD-GDH enzyme is
used in prior-art biosensors that comprise “an action
electrode, a counter electrode,” and “an enzymatic reac-
tion layer.” J.A. 874.
    Independent claim 22 is representative of the Chal-
lenged Claims, and recites:
    A biosensor for measuring glucose, comprising:
        an electrode system comprising an action
        electrode and a counter electrode; and
        an enzymatic reaction layer in contact
        with the action electrode and/or the coun-
        ter electrode, the enzymatic reaction layer
        comprising an electron acceptor and a sol-
        uble [f]lavin compound-binding glucose
        dehydrogenase, which has enzymatic ac-
        tivity to glucose comprising catalyzing a
        reaction for oxidizing glucose in the pres-
        ence of the electron acceptor,
        wherein enzymatic activity to maltose in
        the enzymatic reaction layer is 5% or less
        relative to the enzymatic activity to glu-
        cose;
        wherein the biosensor can quantify glu-
        cose concentrations ranging from 4.5 mM
        to 30 mM.
IN RE: IKEDA FOOD RESEARCH CO., LTD.                      5

J.A. 230 (emphasis added).
               II. The Prior Art References
                         A. Senior
    Entitled “Method for Determining Glucose Content of
Fluid,” European Patent Application Publication
No. 0094161 (“Senior”) (J.A. 283−300) discloses a qualita-
tive procedure for determining blood glucose concentra-
tion, preferably using either a FAD-GDH enzyme derived
from a strain of A. orzyae, which is a different microor-
ganism than the ’668 application’s FAD-GDH enzyme yet
similarly designated E.C. 1.1.99.10, or a PQQ-GDH
enzyme which is designated E.C. 1.1.99.17. See J.A. 283
(“A method for determining glucose present in a fluid
wherein a sample of a glucose-containing fluid is contact-
ed with an assay mixture comprising . . . flavin-dependent
glucose dehydrogenase enzyme E.C. 1.1.99.10 and a
reducible compound, reduction of which can produce
changes in electro-magnetic radiation absorbance charac-
teristics and/or electrical changes.”), 287 (discussing “a
preferred source of E.C. 1.1.99.17” as the second enzyme).
Senior states that the FAD-GDH enzyme it employs “need
not be purified to an excessively high standard” and that
the PQQ-GDH has some “lesser activity on other sugars.”
J.A. 289.
                 B. The Yugawa Patents
    Related U.S. Patent Nos. 6,656,702 (“Yugawa A”) and
6,059,946 (“Yugawa B”) (collectively, “the Yugawa pa-
tents”) disclose “a biosensor” comprising, inter alia, an
“electrode system” with a “working electrode,” “counter
electrode,” and “a reaction layer.” Yugawa A col. 2 ll. 3−7;
see Yugawa B col. 2 ll. 4−8 (same). The enzymes used in
the reaction layer specifically include GDH and PQQ-
GDH. Yugawa A col. 2 ll. 8−15; Yugawa B col. 5 l. 45.
The Yugawa patents also describe stability and cost
advantages of their biosensor similar to those described in
6                        IN RE: IKEDA FOOD RESEARCH CO., LTD.

the ’668 application. Compare Yugawa A col. 1 l. 63–col. 2
l. 2, and Yugawa B col. 1 ll. 66−67, with J.A. 840–41.
                         DISCUSSION
        I. Standard of Review and Legal Standard
     “We review the PTAB’s factual findings for substan-
tial evidence and its legal conclusions de novo.” Redline
Detection, LLC v. Star Envirotech, Inc., 811 F.3d 435, 449
(Fed. Cir. 2015) (citation omitted). “Substantial evidence
is something less than the weight of the evidence but
more than a mere scintilla of evidence,” meaning that “[i]t
is such relevant evidence as a reasonable mind might
accept as adequate to support a conclusion.” In re NuVa-
sive, Inc., 842 F.3d 1376, 1379–80 (Fed. Cir. 2016) (inter-
nal quotation marks and citations omitted). “If two
inconsistent conclusions may reasonably be drawn from
the evidence in record, the PTAB’s decision to favor one
conclusion over the other is the epitome of a decision that
must be sustained upon review for substantial evidence.”
Elbit Sys. of Am., LLC v. Thales Visionix, Inc., 881 F.3d
1354, 1357 (Fed. Cir. 2018) (internal quotation marks,
brackets, and citation omitted).
     A patent claim is invalid “if the differences between
the subject matter sought to be patented and the prior art
are such that the subject matter as a whole would have
been obvious at the time the invention was made to a
person having ordinary skill in the art [(‘PHOSITA’)].” 35
U.S.C. § 103(a). Obviousness is a question of law based
on underlying findings of fact. See In re Adler, 723 F.3d
1322, 1325 (Fed. Cir. 2013). Those underlying findings of
fact include: (1) “the scope and content of the prior art,”
(2) “differences between the prior art and the claims at
issue,” (3) “the level of ordinary skill in the pertinent art,”
and (4) the presence of objective indicia of nonobvious-
ness, such “as commercial success, long felt but unsolved
needs, failure of others,” and unexpected results. Graham
v. John Deere Co. of Kan. City, 383 U.S. 1, 17 (1966); see
IN RE: IKEDA FOOD RESEARCH CO., LTD.                        7

United States v. Adams, 383 U.S. 49, 50–52 (1966). For
objective indicia of non-obviousness, a showing that a
problem was both recognized in the prior art and there
existed a failure of others to provide “a feasible solution to
the long-standing problem” supports a finding of long-felt
need. In re Cyclobenzaprine Hydrochloride, 676 F.3d
1063, 1083 (Fed. Cir. 2012) (citation omitted). Further,
“[a]n obviousness determination requires finding that a
[PHOSITA] would have been motivated to combine or
modify the teachings in the prior art and would have had
a reasonable expectation of success in doing so.” Regents
of Univ. of Cal. v. Broad Inst., Inc., 903 F.3d 1286, 1291
(Fed. Cir. 2018) (citation omitted).
    “We have recognized that inherency may supply a
missing claim limitation in an obviousness analysis.”
PAR Pharm., Inc. v. TWI Pharm., Inc., 773 F.3d 1186,
1194–95 (Fed. Cir. 2014); see id. at 1195 (collecting cases).
However, “the limitation at issue necessarily must be
present[] or the natural result of the combination of
elements explicitly disclosed by the prior art” to be inher-
ently disclosed by the reference. Id.; see Southwire Co. v.
Cerro Wire LLC, 870 F.3d 1306, 1311 (Fed. Cir. 2017)
(requiring the PTAB to find that a reference disclosed an
“identical or substantially identical” process to that
claimed by the patent in order to find inherent obvious-
ness). Where “all process limitations . . . are expressly
disclosed by [the prior art reference], except for the func-
tionally expressed [limitation at issue], the [US]PTO can
require an applicant to prove that the subject matter
shown to be in the prior art does not possess the charac-
teristic relied on.” Southwire, 870 F.3d at 1311 (internal
quotation marks and citation omitted).
                      II. Obviousness
    The PTAB affirmed the Examiner’s findings that em-
ploying the FAD-GDH enzyme preparation described in
Senior with the biosensor described in the Yugawa pa-
8                       IN RE: IKEDA FOOD RESEARCH CO., LTD.

tents would have rendered the Challenged Claims obvious
to a PHOSITA. See J.A. 9−10; see also J.A. 153−57 (Ex-
aminer’s findings). In rendering its obviousness decision,
the PTAB specifically determined that even though Senior
did not expressly disclose the low-maltose activity limita-
tion of claim 22 of the ’668 application, Senior’s disclosed
enzyme preparation inherently contains the same enzy-
matic specificity for glucose relative to maltose as the
Challenged Claims. See J.A. 10; see also J.A. 10−11
(relying on the undisputed fact that both Senior and the
’668 application classify their respective FAD-GDH en-
zyme in their enzyme preparations as E.C. 1.1.99.10, and
concluding that it was reasonable to infer they have the
same low substrate specificity for glucose relative to
maltose). The PTAB also disagreed with Ikeda that
Ikeda’s proffered extrinsic evidence of another “contami-
nated” GDH preparation somehow established that Sen-
ior’s enzyme preparation was likewise contaminated. J.A.
11−12. Ikeda contends that “the PTAB erred in its prima
facie case” by (1) relying upon inherency to supply the
necessary low-maltose activity claim element in making
its obviousness determination, see Appellant’s Br. 30, and
(2) improperly shifting the evidentiary burden to Ikeda,
see id. at 33. Ikeda also asserts that “the [PTAB] erred in
discounting the objective indicia of nonobviousness,”
especially that of a long-felt need. Id. at 42 (capitalization
modified). We address each argument in turn.
A. Substantial Evidence Supports the PTAB’s Determina-
tion that the Challenged Claims Would Have Been Obvi-
        ous over Senior and the Yugawa Patents
     Ikeda contests the PTAB’s determination that Sen-
ior’s E.C. 1.1.99.10 FAD-GDH enzyme preparation inher-
ently discloses the Challenged Claims’ limitation of a
reaction layer with low reactivity toward maltose relative
to glucose, id. at 30, but does not contest that each of the
IN RE: IKEDA FOOD RESEARCH CO., LTD.                       9

other limitations are taught by this combination, see
generally id. 5 Specifically, Ikeda argues that because
“Senior’s enzyme preparation was contaminated with
about 7,000 times more protein than the [’668 applica-
tion]’s preparation,” these impurities cause Senior’s
preparation to “differ[] vastly” from the ’668 application’s
preparation in how it reacts with maltose. Appellant’s Br.
31. We disagree.
    Substantial evidence supports the PTAB’s conclusion
that Senior’s FAD-GDH enzyme preparation inherently
discloses the Challenged Claims’ low-maltose activity
limitation. Table 1 of the ’668 application discloses that
the E.C. 1.1.99.10 enzyme’s activity for maltose is 1.4%
relative to its activity for glucose. See J.A. 882 (reporting
testing results in Table 1 that state that the FAD-GDH
enzyme preparation’s activity towards “maltose” is “1.4%”
relative to its 100% activity towards glucose).        Senior
discloses an assay for determining blood glucose concen-
tration and teaches, in relevant part, purifying an FAD-
GDH enzyme from a crude cellular extract. See J.A. 287.
Although Senior does not directly address glucose specific-
ity or maltose, see J.A. 283−300, Senior’s FAD-GDH
enzyme, prepared from “A[.] oryzae,” has the same “E.C.
1.1.99.10” classification number as the ’668 application’s
FAD-GDH enzyme, even though each FAD-GDH enzyme
is produced from a different microorganism, i.e., from “A.
terreus,” compare J.A. 287, 293, with J.A. 843. E.C.
classification numbers are based on enzyme reactivity, see
J.A. 176 (describing, in a scientific journal, the known

    5   Ikeda also does not dispute the PTAB’s finding
that the Yugawa patents’ biosensor (comprising “an
insulating plate (layer), electrode system, and a reaction
layer,” J.A. 9), could be combined with Senior’s FAD-GDH
E.C. 1.1.99.10 enzyme to arrive at the Challenged Claims’
biosensor, see generally Appellant’s Br.
10                      IN RE: IKEDA FOOD RESEARCH CO., LTD.

“genomics” and “chemical information” represented by
E.C. classification numbers), and Ikeda’s counsel does not
dispute that enzymes with the same E.C. number have the
same substrate specificity “for purposes of this appeal,”
Oral. Arg. at 6:32−:47, http://oralarguments.cafc.uscourts.
gov/default.aspx?fl=2017-2624.mp3.      Therefore, it was
reasonable for the PTAB to conclude that both Senior and
the ’668 application characterize their microbe-derived
preparations as having identical enzymatic activity, which
necessarily includes having the same substrate specificity.
See J.A. 7−8, 11; cf. Butamax (TM) Advanced Biofuels
LLC v. Gevo, Inc., 746 F.3d 1302, 1306 (Fed. Cir. 2014)
(acknowledging that assignment “of different E[.]C[.]
numbers to the same enzyme” indicates that “the differ-
ence between the numbers is the identity of the cofactor
named”), judgment vacated sub nom. on other grounds
Gevo, Inc. v. Butamax Advanced Biofuels LLC, 135 S. Ct.
1173 (2015). The PTAB had a reasonable basis to con-
clude that because Senior discloses the use of the FAD-
GDH enzyme described in the ’668 application, classified
under E.C. 1.1.99.10, the claimed low “5% or less” activity
against maltose relative to glucose in the reaction layer is
inherently disclosed in Senior’s enzyme preparation. See
J.A. 11; see also PAR Pharm., 773 F.3d at 1194–95 (con-
cluding that “[t]he claimed . . . parameters . . . [were]
inherent properties of the obvious . . . formulation,” and
thus “[t]he reduced food effect was an inherent result of [a
composition] even if it was previously not known in the
prior art that a food effect existed” (internal quotation
marks and citation omitted)).
     The PTAB properly adhered to our precedent regard-
ing the prima facie framework to conclude that Ikeda
failed to present sufficient evidence to rebut the substan-
tial evidence supporting that Senior’s FAD-GDH enzyme
preparation inherently discloses the ’668 application’s
claimed low maltose activity relative to glucose. See In re
Spada, 911 F.2d 705, 708 (Fed. Cir. 1990) (“[W]hen the
IN RE: IKEDA FOOD RESEARCH CO., LTD.                    11

[US]PTO shows sound basis for believing that the prod-
ucts of the applicant and the prior art are the same, the
applicant has the burden of showing that they are not.”
(emphasis added) (citation omitted)). Ikeda did not pre-
sent evidence of testing any of the enzyme preparations
found in the prior art, such as by replicating Senior’s
described process of creating its preparation, to support
its argument that the purity of Senior’s preparation must
have differed from the ’668 application because it con-
tained maltose hydrolyzing contaminants (or impurities).
See J.A. 110−25 (Reply Brief), J.A. 249−447 (Reply to
Final Action). Instead, Ikeda presented evidence in the
form of U.S. Patent No. 7,655,130 (“Tsuji”) in support of
its contention that because Tsuji’s purified FAD-GDH
E.C. 1.1.99.10 enzyme preparation “AOGDH” 6 has high
maltose reactivity even after purification, there must
likewise be maltose-hydrolyzing contaminants in Senior’s
FAD-GDH preparation that would cause the preparation
to exhibit more than 5% activity toward maltose relative
to glucose. See J.A. 110−25 (Ikeda Reply Brief); see also
J.A. 432 (stating, in Tsuji’s Example 1, that “[i]n the
AOGDH purified preparation, . . . 90% of maltose was
already degraded into glucose, and after reacting for ten
minutes, nearly 100% maltose was degraded”). 7 The

    6   Tsuji refers to its GDH enzyme preparation as
“AOGDH” because it is recovered from native fungus
Aspergillus oryzae. See J.A. 431.
     7  The parties do not dispute that Tsuji, J.A. 426−48,
which issued in 2010, qualifies as extrinsic evidence that
may be relevant in determining what was inherently
present in the prior art. See generally Appellant’s Br.;
Appellee’s Br. Therefore, we deem it appropriate to
consider Tsuji’s teachings here. See ASM Am., Inc. v.
Genus, Inc., 401 F.3d 1340, 1347 (Fed. Cir. 2005) (conclud-
ing that extrinsic evidence that post-dated the patent
filing date nonetheless was helpful in determining how a
12                      IN RE: IKEDA FOOD RESEARCH CO., LTD.

PTAB found that “Tsuji’s example of a contaminated
preparation [did not] establish the presence of such con-
taminants in Senior.” J.A. 11. In addition, there is no
specific evidence in Tsuji or of record that any contami-
nant in Tsuji results in a greater than 5% maltose activity
relative to glucose. See Tsuji col. 1 l. 28−col. 14 l. 8. To
the contrary, Tsuji’s AOGDH preparation Table 1 shows
low, i.e., “0.4%,” enzymatic reactivity to maltose relative
to “100.0%” reactivity to glucose. Id. col. 12 ll. 1−43. The
PTAB could reasonably find that Tsuji does not persua-
sively rebut the prima facie finding of inherency.
    Moreover, simply because Senior never quantified
maltose activity achieved by its disclosed embodiments
does not preclude the PTAB’s evidentiary finding that
Senior’s enzyme preparation process necessarily achieved
the low activity of 5% or less relative to glucose claimed in
the Challenged Claims, see J.A. 230; J.A. 11−12, especial-
ly since Senior’s enzyme’s stated E.C. classification was
the same as the ’668 application’s enzyme, compare J.A.
293 with J.A. 843. “In the absence of any evidence that
the claimed [low activity] would have been unexpected in
light of [Senior’s] disclosure, there is no indication that
the limitation is anything other than mere quantification
of the results of a known process.” Southwire, 870 F.3d at
1311. As our predecessor court explained, the fairness of
shifting the burden “is evidenced by the [US]PTO’s inabil-
ity to manufacture products or to obtain and compare
prior art products.” In re Best, 562 F.2d 1252, 1255
(CCPA 1997). Therefore, we see no reason to call into
question the PTAB’s finding “that the ‘possible presence
of contaminants’ in Senior’s enzyme preparation [does
not] render the claimed biosensor non-obvious.” J.A. 11;
see Elbit, 881 F.3d at 1537 (“If two inconsistent conclu-

PHOSITA would have understood the claim term at the
time it was filed).
IN RE: IKEDA FOOD RESEARCH CO., LTD.                    13

sions may reasonably be drawn from the evidence in
record, the PTAB’s decision to favor one conclusion over
the other is the epitome of a decision that must be sus-
tained upon review for substantial evidence.” (internal
quotation marks and citation omitted)). Ikeda’s evidence
does not show that the PTAB lacked a reasonable basis
for finding that Senior, as the operative prior art, neces-
sarily possesses the ’668 application’s claimed low maltose
activity relative to glucose. See In re Spada, 911 F.2d at
709 (determining that an appellant “showed no error, in
science or in law, in the [PTAB]’s holding that . . . the
products [at issue] appeared to be the same and thus that
[the appellant’s] products were not new”).
    Ikeda’s counterarguments lack merit. First, Ikeda ar-
gues that the PTAB improperly “conflat[ed] Senior’s
enzyme preparation with the enzyme per se,” Appellant’s
Br. 30, such that the E.C. 1.1.99.10 “designation does not
mean that the enzyme preparation possesses only that
single enzymatic activity,” id. at 32. However, Ikeda’s
logic misses the mark. The Challenged Claims do not
require such exclusivity; the only disputed limitation is
that they require a low maltose relative to glucose. See
J.A. 230. Thus, Ikeda’s contention that an E.C. designa-
tion does not refer to a single enzymatic activity does not
contradict the evidence supporting the PTAB’s finding
that the E.C. 1.1.99.10 designation means that the prepa-
ration has identical or similar substrate specificity for
glucose.
    Second, Ikeda avers that the PTAB “ignored [Ikeda]’s
evidence when deciding whether there exists a reasonable
basis for inherency.” Appellant’s Br. 36 (emphasis added).
However, as we determine above, the PTAB expressly
considered, and found unpersuasive, Ikeda’s evidence in
support of its argument that the purity of Senior’s enzyme
preparation differed from the ’668 application and thus
did not inherently possess low activity against maltose.
See, e.g., J.A. 11 (stating that, “[a]s an initial matter,
14                     IN RE: IKEDA FOOD RESEARCH CO., LTD.

[Ikeda’s] speculation about the possibility that Senior’s
preparation may contain contaminants does not establish
that Senior’s preparation in fact had such contaminants,”
and that while the PTAB “agree[d] with [Ikeda] that the
claims are directed to the activity of the enzyme layer and
not just of GDH,” it “d[id] not agree that the ‘possible
presence of contaminants’ in Senior’s enzyme preparation
renders the claimed biosensor non-obvious” (emphases
added)), 12 (“[Ikeda’s] example relied on a different prep-
aration method than was used in Senior.”). Accordingly,
the PTAB properly considered the record evidence in
affirming the Examiner’s obviousness findings.
  B. Substantial Evidence Supports the PTAB’s Finding
 that Objective Indicia of Nonobviousness Do Not Rebut
          the Prima Facie Case of Obviousness
    The PTAB found, inter alia, that Ikeda’s “objective in-
dicia of nonobviousness” do not “demonstrate[] the non-
obviousness of the claimed biosensor” because the “scope
of the [Challenged] Claims was not commensurate with
the asserted need.” J.A. 15. The PTAB accorded Ikeda’s
expert’s testimony little weight when he testified that
“biosensors based on NAD-GDH enzymes did not satisfy
this long-felt need because they require a cofactor” be-
cause the Challenged Claims “encompass biosensors that
use cofactors and thus do not satisfy the alleged need for
dehydrogenase-based glucose sensors that do not rely on a
cofactor.” J.A. 15. Ikeda argues that “a need existed since
at least 1986 for improved blood glucose monitors” that
were “both specific and independent of separate cofac-
tors.” Appellant’s Br. 43, 44 (capitalization modified).
Ikeda also argues that the PTAB “erred by not crediting
[Ikeda’s] evidence of long-felt need” for a GDH enzyme
with no separate cofactor. Id. at 47. We disagree with
Ikeda.
    We see no error in the PTAB’s analysis, and ultimate
rejection as unpersuasive, of Ikeda’s evidence of secondary
IN RE: IKEDA FOOD RESEARCH CO., LTD.                      15

considerations relating to long-felt need. Ikeda’s expert
stated that twenty years elapsed after the publication of
Senior, and seventeen years elapsed after a 1986 publica-
tion by Ikeda’s expert documenting a “need for a dehydro-
genase-based glucose sensor” that “ha[d] no cofactor
requirement,” before the ’668 application was filed.
J.A. 273−74 (expert declaration); see J.A. 14 (acknowledg-
ing, by the PTAB, that “[a]lthough Senior does not require
a cofactor, [Ikeda’s expert] contends that Senior’s disclo-
sure failed to satisfy the need for a dehydrogenase-based
glucose sensor because of the possible presence of contam-
inants and the low degree of purification” (internal quota-
tion marks and citation omitted)). However, the PTAB
considered Ikeda’s expert testimony and concluded that it
did not have any substantive relevance, see J.A. 14−15, a
determination that we do not revisit, see Elbit, 881 F.3d
at 1358 (“The PTAB is entitled to weigh the credibility of
the witnesses.” (brackets and citation omitted)). Fur-
thermore, we recognize that claim 22 employs the transi-
tional phrase “comprising” in the preamble, J.A. 230, and,
therefore, does not exclude biosensors that employ a
cofactor, see CIAS, Inc. v. All. Gaming Corp., 504 F.3d
1356, 1360 (Fed. Cir. 2007) (“In the patent claim context[,]
the term ‘comprising’ is well understood to mean ‘includ-
ing but not limited to.’” (citation omitted)). Thus, the
Challenged Claims encompass biosensors that use cofac-
tors, and it follows that they do not satisfy Ikeda’s alleged
need for dehydrogenase-based glucose sensors that do not
rely on a cofactor. 8

    8  The PTAB found, as an alternative to its inherent
obviousness analysis, that even if “Senior’s [FAD-GDH]
enzyme preparation includes contaminants, it would have
been obvious for [a PHOSITA] to modify . . . Senior’s
chromatographic purification to” achieve the claimed low-
maltose activity of the ’668 application’s FAD-GDH en-
16                     IN RE: IKEDA FOOD RESEARCH CO., LTD.

                      CONCLUSION
    We have considered Ikeda’s remaining arguments and
find them unpersuasive. Accordingly, the Decision on
Appeal of the U.S. Patent and Trademark Office’s Patent
Trial and Appeal Board is
                      AFFIRMED

zyme.     J.A. 12 (emphasis added) (internal quotation
marks and citation omitted). Although Ikeda challenges
this alternative finding on appeal, see Appellant’s Br. 5,
39−41, we need not address this alternative theory, given
that we uphold the PTAB’s inherent obviousness deter-
mination, see supra Section II.B; In re Gleave, 560 F.3d
1331, 1338 (Fed. Cir. 2009) (declining to address alterna-
tive grounds of unpatentability when we uphold one such
ground).