Industrial Technology Research v. Pacific Biosciences , 640 F. App'x 871 ( 2016 )


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  •        NOTE: This disposition is nonprecedential.
    United States Court of Appeals
    for the Federal Circuit
    ______________________
    INDUSTRIAL TECHNOLOGY RESEARCH
    INSTITUTE,
    Appellant
    v.
    PACIFIC BIOSCIENCES OF CALIFORNIA, INC.,
    Appellee
    ______________________
    2015-1200
    ______________________
    Appeal from the United States Patent and Trademark
    Office, Patent Trial and Appeal Board, in Interference No.
    105,970.
    ______________________
    Decided: January 29, 2016
    ______________________
    ERIK R. PUKNYS, Finnegan, Henderson, Farabow,
    Garrett & Dunner, LLP, Palo Alto, CA, argued for appel-
    lant. Also represented by MICHAEL PAUL BARKER.
    EDWARD R. REINES, Weil, Gotshal & Manges LLP,
    Redwood Shores, CA, argued for appellee. Also repre-
    sented by MICHELE GAUGER, DEREK C. WALTER.
    ______________________
    2       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    Before PROST, Chief Judge, LOURIE and WALLACH,
    Circuit Judges.
    LOURIE, Circuit Judge.
    Industrial Technology Research Institute and Ti-
    Shiue Biotech, Inc. (collectively, “ITRI”) appeal from the
    decision of the United States Patent and Trademark
    Office Patent Trial and Appeal Board (“Board”) awarding
    judgment to Pacific Biosciences of California, Inc. (“Pac-
    Bio”) in Interference No. 105,970. Indus. Tech. Research
    Inst. v. Pac. Biosciences of Cal., Inc., Interference No.
    105,970, 
    2014 WL 4381078
    , at *1 (P.T.A.B. Sept. 3, 2014)
    (“Board Decision”). The Board terminated the interfer-
    ence after it determined that all of ITRI’s involved claims,
    viz., claims 1–28 of U.S. Patent 8,486,630 (“the ’630
    patent”), would have been obvious over the cited prior art,
    and that PacBio, the senior party, was entitled to the
    benefit of the filing date of its U.S. Provisional Applica-
    tion 61/201,551 (“the ’551 application”) because that
    application adequately described an embodiment of the
    interference Count. 
    Id. at *31.
    For the reasons that
    follow, we affirm in part, vacate in part, and remand for
    further proceedings consistent with this opinion.
    BACKGROUND
    I
    The technology at issue relates to methods of detect-
    ing modified bases in nucleic acids. Deoxyribonucleic acid
    (“DNA”) is a polymeric molecule having repeating units of
    nucleotide bases—adenine (“A”), guanine (“G”), cytosine
    (“C”), and thymine (“T”)—that are covalently linked
    together via a sugar-phosphate backbone. DNA carries
    genetic information in the sequence of those bases. DNA
    also carries epigenetic information when one or more
    bases are chemically modified. For example, C at a given
    position in the DNA sequence may be naturally methylat-
    ed and instead exist as 5-methylcytosine (“mC”). Such
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES        3
    DNA methylation plays an important role in the regula-
    tion of gene expression. ’630 patent col. 2 ll. 14–15.
    Detecting modified bases in the DNA sequence would
    facilitate the further study of their epigenetic effects.
    DNA usually exists in a double-stranded form, with
    two strands coiled around each other in a double helix.
    The two strands are often referred to as the “forward” and
    “reverse” strands. In the double helix, each base on one
    strand pairs with a base on the other strand according to
    the Watson-Crick base pairing rules—A pairs with T, and
    C with G. Thus, the forward and reverse strands typical-
    ly have complementary sequences.
    A DNA sequence may be determined using sequenc-
    ing-by-synthesis (“SBS”) methods. During DNA synthe-
    sis, a parent strand is separated from its complement, and
    an enzyme catalyzes the synthesis of a new complemen-
    tary strand by adding nucleotides, one at a time, to that
    new strand, using the parent strand as a template and
    pairing bases according to the Watson-Crick rules. The
    SBS technique monitors the order of nucleotide addition
    to the growing new strand, and from that deduces the
    sequence of the complementary template strand.
    Traditional SBS methods might not readily distin-
    guish a base from its modified form. For example, C and
    mC would both pair with G during SBS. Detecting the
    addition of a G to the growing new strand only suggests
    that either C or mC is at the corresponding position of the
    template strand. According to ITRI, some prior-art meth-
    ods relied on bisulfite conversion to distinguish C from
    mC. Appellant’s Br. 2, 10–11. Thus, one first obtains a
    reference sequence of the DNA being studied. A sample of
    that DNA is then treated with bisulfite, which converts C
    to uracil (“U”), but does not affect mC or other bases. The
    bisulfite-treated DNA is then sequenced. Because U pairs
    preferentially with A, not G, comparing the bisulfite-
    treated DNA sequence with the untreated reference
    4       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    sequence would reveal the positions of the C-to-U conver-
    sion, whereas the mC positions would show no change,
    thus distinguishing C from mC in the DNA sequence.
    II
    ITRI owns the ’630 patent, which claims a method of
    determining the position of at least one modified base in a
    double-stranded nucleic acid. Claim 24 is representative
    and reads as follows: 1
    24. A method of determining a sequence of a dou-
    ble-stranded nucleic acid sample and a posi-
    tion of at least one modified base in the
    sequence, comprising:
    a. locking the forward and reverse strands of
    the nucleic acid sample together to form a
    circular pair-locked molecule;
    b. obtaining sequence data of the circular
    pair-locked molecule via single molecule
    sequencing, wherein sequence data com-
    prises sequences of the forward and re-
    verse strands of the circular pair-locked
    molecule; and
    c. determining the sequence of the double
    stranded nucleic acid sample and the posi-
    tion of the at least one modified base in the
    sequence of the double stranded nucleic ac-
    id sample by comparing the sequences of
    the forward and reverse strands of the cir-
    cular pair-locked molecule, wherein at
    least one modified base in the double-
    stranded nucleic sample is paired with a
    1    As indicated infra, the sole count of the interfer-
    ence is identical to claim 24 of the ’630 patent.
    6        INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    The ’630 patent describes the bisulfite conversion of a
    CPLM as one embodiment of the methods for detecting
    modified bases, 
    id. col. 23
    ll. 44–65, col. 26, ll. 10–23, and
    illustrates in Figure 5B, which is shown below, a bisulfite-
    treated CPLM with matched mC-G and mismatched G-U
    base pairs, 
    id. col. 6
    ll. 16–23.
    
    Id. fig.5B. Additionally,
    claim 23 of the ’630 patent requires that
    the forward and reverse strands of the double-stranded
    nucleic acid be locked together by two nucleic acid inserts
    of known sequences to form the CPLM. See 
    id. fig.3A &
    3B (depicting a CPLM made from the forward and reverse
    strands 11 and 12 and two inserts 13 and 14). Because
    sequencing data from a given experiment may not be
    100% accurate, claim 23 provides that the CPLM is se-
    quenced multiple times; that each set of the sequence
    data of the inserts is scored by comparing the measured
    sequence with the known sequence, 
    id. col. 47
    ll. 15–18;
    and that a given set of the sequence data of the forward or
    reverse strand is then accepted or rejected based on “the
    scores of one or both of the sequences of the inserts imme-
    diately upstream and downstream of the sample sequenc-
    es,” 
    id. col. 47
    ll. 19–25.
    Claim 23 depends from claim 1; both claims are re-
    produced below.
    1.   A method of determining a sequence of a dou-
    ble-stranded nucleic acid sample and a posi-
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES         7
    tion of at least one modified base in the se-
    quence, comprising:
    a. locking the forward and reverse strands
    together to form a circular pair-locked
    molecule;
    b. obtaining sequence data of the circular
    pair-locked molecule via single molecule
    sequencing, wherein the sequence data
    comprises sequences of the forward and
    reverse strands of the circular pair-locked
    molecule;
    c. determining the sequence of the double-
    stranded nucleic acid sample by comparing
    the sequences of the forward and reverse
    strands of the circular pair-locked mole-
    cule;
    d. altering the base-pairing specificity of ba-
    ses of a specific type in the circular pair-
    locked molecule to produce an altered cir-
    cular pair-locked molecule;
    e. obtaining the sequence data of the altered
    circular pair-locked molecule wherein the
    sequence data comprises sequences of the
    altered forward and reverse strands; and
    f. determining the positions of modified ba-
    ses in the sequence of the double-stranded
    nucleic acid sample by comparing the se-
    quences of the altered forward and reverse
    strands.
    23. The method of claim 1, wherein:
    the forward and reverse strands of the circu-
    lar pair-locked molecule are locked togeth-
    er by nucleic acid inserts;
    8       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    the sequence data obtained in step (b) com-
    prise at least two copies of the sequence of
    the circular pair-locked molecule, each
    copy comprising sequences of first and sec-
    ond insert-sample units;
    the sequences of the first and second insert-
    sample units comprise insert sequences,
    which may be identical or non-identical,
    and oppositely oriented repeats of the se-
    quence of the nucleic acid sample; and
    the method further comprises:
    g. calculating scores of the sequences of at
    least four inserts contained in the se-
    quence data by comparing the sequences
    of the at least four inserts to the known
    sequences of the inserts;
    h. accepting or rejecting at least four of the
    repeats of the sequence of the nucleic acid
    sample contained in the sequence data ac-
    cording to the scores of one or both of the
    sequences of the inserts immediately up-
    stream and downstream of the sample se-
    quences, subject to the condition that at
    least one sample sequence in each orienta-
    tion is accepted;
    i. compiling an accepted sequence set com-
    prising the at least one sample sequence in
    each orientation accepted in step (g); and
    j. determining the sequence of the nucleic
    acid sample using the accepted sequence
    set.
    
    Id. col. 45
    ll. 24–47, col. 47 ll. 3–30 (emphasis added).
    Lastly, claims 27 and 28 of the ’630 patent require the
    use of a “nucleotide analog that discriminates between a
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES         9
    base and its modified form” in sequencing. 
    Id. col. 48
    ll.
    28–33, 45–50. The ’630 patent describes such a compound
    as a “discriminating analog” that “pairs preferentially
    with one but not the other of the base and its modified
    form.” 
    Id. col. 24
    ll. 15–19. The ’630 patent also provides
    examples of “discriminating analogs” that were known in
    the art. 
    Id. col. 24
    l. 42–col. 25 l. 24 (citing U.S. Patent
    7,399,614). Those examples are base-linked analogs,
    meaning that they have bulky groups chemically linked to
    the base moiety, allowing them to pair preferentially with
    a base or its modified form during sequencing. Claim 27
    is representative of those two claims and reads as follows:
    27. A method of determining a sequence of a dou-
    ble-stranded nucleic acid sample and a posi-
    tion of at least one modified base in the
    sequence, comprising:
    a. locking the forward and reverse strands
    together to form a circular pair-locked
    molecule;
    b. obtaining sequence data of the circular
    pair-locked molecule via single molecule
    sequencing, wherein the sequence data
    comprises sequences of the forward and
    reverse strands of the circular pair-locked
    molecule;
    c. determining the sequence of the double-
    stranded nucleic acid sample by compar-
    ing the sequences of the forward and re-
    verse strands of the circular pair-locked
    molecule;
    d. obtaining sequencing data of the circular
    pair-locked molecule via single molecule
    sequencing, wherein at least one nucleotide
    analog that discriminates between a base
    and its modified form is used to obtain se-
    10       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    quence data comprising at least one posi-
    tion wherein the at least one differentially
    labeled nucleotide analog was incorpo-
    rated; and
    e. determining the positions of modified ba-
    ses in the sequence of the double-stranded
    nucleic acid sample by comparing the se-
    quences of the forward and reverse
    strands.
    
    Id. col. 48
    ll. 15–37 (emphasis added).
    III
    PacBio owns by assignment U.S. Patent Application
    13/633,673 (“the ’673 application”) and U.S. Patent Appli-
    cation 13/930,178 (“the ’178 application”). PacBio copied
    the ’630 patent claims into its ’673 application to provoke
    an interference with ITRI. 2 In October 2013, the Board
    declared Interference No. 105,970 between PacBio’s ’673
    application and ITRI’s ’630 patent. Three months later,
    PacBio’s ’178 application was added to the interference.
    The interference involves a sole count corresponding
    to all twenty-eight claims of ITRI’s ’630 patent and all
    pending claims of PacBio’s ’673 and ’178 applications.
    The Count is identical to claim 24 of the ’630 patent.
    When declaring the interference, the Board accorded
    PacBio the benefit of the ’551 application, filed on Decem-
    ber 11, 2008, and accorded ITRI the benefit of an applica-
    2  The parties do not dispute that ITRI’s ’630 patent
    and PacBio’s ’673 and ’178 applications all have effective
    filing dates before the enactment of the Leahy-Smith
    America Invents Act (“AIA”), Pub. L. No. 112-29, 125 Stat.
    284 (2011). The pre-AIA versions of 35 U.S.C. §§ 102,
    103, and 112 therefore apply in this appeal. See Pub. L.
    No. 112-29, § 3(n)(1), 125 Stat. at 293.
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES        11
    tion filed on April 7, 2009. Based on those filing dates,
    the Board designated PacBio as the senior party.
    The parties then filed preliminary motions, including
    ITRI’s motion seeking to rescind the benefit of PacBio’s
    ’551 application (“rescind motion”) and PacBio’s motion
    alleging that all claims of ITRI’s ’630 patent would have
    been obvious in view of the prior art (“obviousness mo-
    tion”). The prior art asserted by PacBio against ITRI’s
    ’630 patent included: (1) U.S. Patent 8,153,375 (“the ’375
    patent”), assigned to PacBio; (2) PacBio’s Cold Spring
    Harbor Personal Genomes Meeting Presentation, dated
    October 12, 2008 (“the Personal Genomes presentation”);
    (3) Laird et al., Hairpin-bisulfite PCR: Assessing epigenet-
    ic methylation patterns on complementary strands of
    individual DNA molecules, 101 Proc. Nat’l Acad. Sci. 204
    (2004) (“Laird”); (4) Matsumura et al., Photochemical
    transition of 5-methylcytosine to thymine by DNA photo-
    ligation, 51 Nucleic Acids Symp. Series 233 (2007)
    (“Matsumura”); and (5) U.S. Patent 7,399,614 (“the ’614
    patent”).
    In a written decision on September 3, 2014, the Board
    granted PacBio’s obviousness motion and denied ITRI’s
    rescind motion. In granting PacBio’s obviousness motion,
    the Board concluded that all claims of ITRI’s ’630 patent
    would have been obvious in view of the ’375 patent, Laird,
    and Matsumura. Board Decision, 
    2014 WL 4381078
    , at
    *20. Although the Board cited Matsumura, its obvious-
    ness analysis did not rely on any specific teachings of
    Matsumura. The Board also did not rely on the ’614
    patent cited by PacBio. Moreover, the Board did not
    consider the Personal Genomes presentation, after finding
    that it was not prior art under 35 U.S.C. § 102(b). 
    Id. at *13
    n.27. Thus, the Board relied only on the ’375 patent
    and Laird as prior art in its obviousness analysis.
    First, as to claim 24, which the parties regarded as
    representative of most of the claims of the ’630 patent, the
    12      INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    Board noted that ITRI did not dispute that the ’375
    patent taught steps (a) and (b) of claim 24. The Board
    then found that Laird taught step (c), and thus concluded
    that claim 24 would have been obvious in view of the ’375
    patent and Laird. 
    Id. at *20–21.
    Second, the Board
    rejected ITRI’s argument that the prior art did not teach
    step (h) of claim 23; instead, the Board found that the ’375
    patent and Laird taught that limitation. 
    Id. at *22.
    Last,
    as to claims 27 and 28, which require a nucleotide analog
    that discriminates between a base and its modified form,
    the Board concluded that those claims would have been
    obvious because “Laird teaches such a method [of] dis-
    criminating between methylated and non-methylated
    cytosines.” 
    Id. at *22–23.
        The Board accordingly found all claims of the ’630 pa-
    tent to be unpatentable as obvious because “[t]he com-
    bined cited prior art references teach or suggest all of the
    limitations of the claims of the ’630 patent” and “a person
    of ordinary skill in the art would be motivated to combine
    the references to increase the accuracy of the invention,
    particularly with respect to discriminating between
    methylated and demethylated cytosine bases.” 
    Id. at *23.
    The Board did not opine on whether the references cited
    by PacBio would be prior art to PacBio’s own claims, thus
    rendering them similarly unpatentable as obvious, even
    though the parties disputed that issue. J.A. 269–70, 346,
    421, 750–52.
    In denying ITRI’s rescind motion, the Board found
    that PacBio was entitled to the benefit of the filing date of
    the ’551 application because that application provided an
    adequate written description of an embodiment of the
    Count. Board Decision, 
    2014 WL 4381078
    , at *28–31. In
    particular, the Board found that the ’551 application
    teaches step (c) of the Count, in part, because the applica-
    tion explicitly states that “‘sequence reads from the sense
    or ‘forward’ strand can be compared to sequence reads
    from the antisense or ‘reverse’ strand for the same nucleic
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES       13
    acid template to further validate the existence of one or
    more modified bases in the template nucleic acid.’” 
    Id. at *28–29
    (quoting ’551 application ¶ 17).
    The Board entered judgment against ITRI. 
    Id. at *1.
    ITRI then appealed to this court. We have jurisdiction
    under 28 U.S.C. § 1295(a)(4)(A). See Leahy-Smith Ameri-
    ca Invents Act Technical Corrections, Pub. L. No. 112-274,
    § 1(k)(3), 126 Stat. 2456, 2458 (2013).
    DISCUSSION
    I. OBVIOUSNESS OF ITRI’S PATENT CLAIMS
    We review the Board’s legal determinations de novo,
    In re Elsner, 
    381 F.3d 1125
    , 1127 (Fed. Cir. 2004), and the
    Board’s factual findings underlying those determinations
    for substantial evidence, In re Gartside, 
    203 F.3d 1305
    ,
    1316 (Fed. Cir. 2000). A finding is supported by substan-
    tial evidence if a reasonable mind might accept the evi-
    dence to support the finding. Consol. Edison Co. v.
    NLRB, 
    305 U.S. 197
    , 229 (1938).
    Obviousness is a question of law based on underlying
    factual findings, In re Baxter, 
    678 F.3d 1357
    , 1361 (Fed.
    Cir. 2012), including what a reference teaches, In re
    Beattie, 
    974 F.2d 1309
    , 1311 (Fed. Cir. 1992), the exist-
    ence of a reason to combine references, In re Hyon, 
    679 F.3d 1363
    , 1365–66 (Fed. Cir. 2012), and whether the
    prior art teaches away from the claimed invention, In re
    Mouttet, 
    686 F.3d 1322
    , 1330 (Fed. Cir. 2012).
    A. Claims 1–22 and 24–26
    ITRI argues that the Board erred in finding that
    Laird teaches determining the position of a modified base
    by comparing the sequences of the forward and reverse
    14       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    strands as required by step (c) of claim 24. 3 According to
    ITRI, researchers in Laird used conventional methods to
    determine the positions of modified bases, by comparing
    the sequences of bisulfite-treated and untreated versions
    of the same strand, not the forward and reverse strands of
    the same molecule as claimed by ITRI. ITRI asserts that
    the Board improperly engaged in hindsight analysis by
    speculating that a skilled artisan would have understood
    that mismatches in the sequences of the forward and
    reverse strands would indicate modified base positions.
    According to ITRI, only the ’630 patent, not Laird or any
    other prior art, teaches using mismatches to detect modi-
    fied bases.
    PacBio responds that the claims do not require using
    mismatches to detect modified bases because a preferred
    embodiment of the ’630 patent, involving bisulfite conver-
    sion of C (but not mC) to U, uses matches of mC to G to
    detect the mC positions. Appellee’s Br. 29–33 (citing ’630
    patent col. 26 ll. 10–22). PacBio alternatively argues that,
    even if the use of mismatches were required, the claims
    would still have been obvious because substantial evi-
    dence supports the Board’s finding that Laird teaches
    that limitation. PacBio additionally argues that a person
    of skill in the art would have been motivated to combine
    the prior art to practice the claimed method and achieve a
    predictable result, that one would have had a reasonable
    expectation of success in doing so, and that there is no
    evidence of objective indicia of nonobviousness.
    We agree with PacBio that the Board did not err in its
    obviousness determination as to claims 1–22 and 24–26
    3  ITRI relies only on limitations in claim 24 to chal-
    lenge the obviousness determination as to claims 1–22
    and 24–26. See Appellant’s Br. 29. Those claims there-
    fore stand or fall together with claim 24. In re Kaslow,
    
    707 F.2d 1366
    , 1376 (Fed. Cir. 1983).
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES        15
    because Laird suggests using mismatches in the sequenc-
    es of the forward and reverse strands to determine modi-
    fied base positions. ITRI does not dispute that the ’375
    patent discloses steps (a) and (b) of claim 24. Nor does
    ITRI challenge the Board’s finding of a motivation to
    combine the ’375 patent and Laird. The only question is
    then whether substantial evidence supports the Board’s
    finding that Laird teaches step (c) of claim 24, and we
    conclude that it does.
    As an initial matter, the record shows that the Board
    did not formally construe the claims. In the background
    section of the Board’s written decision, it informally
    interpreted step (c) of claim 24, or the Count, as requiring
    the use of mismatches in determining modified base
    positions, which is what ITRI proposed. Board Decision,
    
    2014 WL 4381078
    , at *3. Applying that claim interpreta-
    tion, the Board decided the obviousness motion and the
    rescind motion against ITRI. 
    Id. at *21,
    *30.
    The Board’s claim interpretation is consistent with
    the claim language and specification of the ’630 patent.
    Contrary to PacBio’s arguments, that interpretation does
    not exclude the bisulfite method disclosed in the ’630
    patent, in which bisulfite converts C, but not mC, to U in a
    CPLM. When comparing the sequences of the forward
    and reverse strands of such a bisulfite-treated CPLM, one
    would find both matched mC-G pairs and mismatched U-G
    pairs. The bisulfite method does use mismatched U-G
    pairs in distinguishing C from mC and in determining the
    positions of modified bases, which may be either U or mC.
    The parties do not otherwise allege error in the Board’s
    claim interpretation. Accordingly, on this record, we
    conclude that the Board did not err in interpreting step (c)
    16       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    of claim 24, or the Count, as requiring the use of mis-
    matches in determining modified base positions. 4
    Although we agree with ITRI on the proper interpre-
    tation of step (c) of claim 24, we nevertheless conclude
    that substantial evidence supports the Board’s finding
    that the disclosure of Laird would have suggested that
    claim limitation to a person of ordinary skill in the art.
    Laird teaches “hairpin-bisulfite PCR.” J.A. 722. It ex-
    plains that “[b]isulfite conversion . . . provides information
    on the methylation state of individual cytosines by con-
    verting cytosine (but not 5-methylcytosine) to uracil . . . .”
    J.A. 723. Thus, Laird teaches that modified bases can be
    detected through the use of bisulfite treatment.
    As disclosed in Laird, a double-stranded DNA was li-
    gated on one end with a hairpin linker, and the covalently
    linked forward and reverse strands were treated with
    bisulfite and then sequenced. 
    Id. According to
    Laird,
    “[f]or purposes of analysis and presentation, the output
    sequence was folded, using word-processing software, into
    a hairpin conformation so that both strands align.” 
    Id. (emphases added).
    Laird depicts in Figure 2 several pairs
    of forward and reverse strands side-by-side that have
    mismatches in the sequences of the forward and reverse
    strands as a result of the bisulfite treatment. J.A. 725.
    Laird explains that “[w]ith hairpin-bisulfite PCR, we can
    assess the methylation status on the bottom strand of
    each hypermethylated allele for which we have top-strand
    data,” and that “we can distinguish between symmetrical
    and asymmetrical patterns of methylation for each of the
    4  PacBio filed a motion in this court to strike cer-
    tain arguments made in ITRI’s reply brief, relating to the
    prosecution history of the ’630 patent, as improperly
    raised for the first time on appeal. Because our decision
    does not turn on those arguments, we dismiss PacBio’s
    motion as moot.
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES         17
    CpG/CpG dyads.” J.A. 724 (emphases added). Moreover,
    Figure 2D shows several asymmetrical hemimethylated
    CpG/CpG dyads, in which one strand of the DNA has a mC
    and the other has a C. J.A. 725.
    Substantial evidence therefore supports the Board’s
    finding that “Laird teaches that methylated and un-
    methylated [CpG] dyads in a bisulfite-treated DNA se-
    quence can be identified by the matching or mismatching
    of cytosines in the forward and reverse strand sequence
    data,” Board Decision, 
    2014 WL 4381078
    , at *20, and that
    “Laird explicitly teaches looking for guanine-thymine
    mismatches as evidence of non-methylated cytosine in a
    forward or reverse strand locus,” 
    id. at *21.
    We therefore
    conclude that the Board did not err in finding that Laird
    would have suggested to a person of ordinary skill in the
    art that mismatched base pairs in the sequences of the
    forward and reverse strands may be used to determine
    the positions of modified bases in double-stranded DNA.
    Accordingly, we affirm the Board’s determination that
    claims 1–22 and 24–26 would have been obvious over the
    ’375 patent and Laird.
    B. Claim 23
    ITRI argues that the Board additionally erred in find-
    ing claim 23 obvious because the Board failed to find that
    the prior art taught step (h) of claim 23, which requires
    accepting or rejecting a given data set of a DNA sample
    sequence based on the score calculated for an insert se-
    quence immediately upstream or downstream from the
    sample sequence. ITRI contends that the Board failed to
    otherwise point to any record evidence to support its
    finding that the prior art taught step (h).
    PacBio responds that step (h) of claim 23 would have
    been obvious in view of the ’375 patent. PacBio argues
    that the level of skill in the art was high and that, even if
    the ’375 patent does not precisely teach step (h), a skilled
    18      INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    artisan would have nonetheless found the differences
    between the claimed invention and the ’375 patent to be
    insubstantial and therefore obvious.
    We agree with ITRI that the Board did not sufficiently
    address whether the prior art teaches step (h) of claim 23
    or otherwise would have rendered that limitation obvious.
    It is undisputed that claim 23 requires that, when analyz-
    ing multiple reads of the CPLM sequence, one accepts or
    rejects a given data set of the forward or reverse strand
    sequence based on the score of a different sequence—the
    insert sequence upstream or downstream from the for-
    ward or reverse strand sequence. But the Board’s cursory
    obviousness analysis with respect to claim 23 lacks any
    indication that the Board considered that claim limitation
    in view of the prior art. The Board’s analysis seems to
    mainly focus on using multiple reads of one position in the
    sequence to determine the consensus sequence of that
    same position. Board Decision, 
    2014 WL 4381078
    , at *22.
    It may be true that, in view of the cited prior art and
    the level of ordinary skill in the relevant art, the differ-
    ences between step (h) of claim 23 and the prior art would
    have been insubstantial. But the scope and content of the
    prior art and the differences between the prior art and the
    claimed invention are issues of fact to be decided by the
    Board, not this court. Cooper v. Ford Motor Co., 
    748 F.2d 677
    , 679 (Fed. Cir. 1984). The Board did not make suffi-
    cient factual findings in its written decision or otherwise
    point to evidence that a skilled artisan would have ac-
    cepted or rejected a sample sequence based on the score of
    a different insert sequence that is upstream or down-
    stream from the sample sequence. We therefore vacate
    the obviousness determination as to claim 23 and remand
    for further proceedings at the Board.
    C. Claims 27 and 28
    ITRI argues that the Board erred in finding claims 27
    and 28 obvious because neither the ’375 patent nor Laird,
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES        19
    which the Board relied on, discloses the use of a discrimi-
    nating nucleotide analog as required by the claims. ITRI
    also contends that the Board provided no explanation for
    why the missing claim limitation would nonetheless have
    been obvious. ITRI also argues that the Board improperly
    disregarded evidence that the Personal Genomes presen-
    tation taught away from using base-linked analogs, which
    include discriminating nucleotide analogs, and thus would
    have discouraged a skilled artisan from combining the
    ’375 patent with a discriminating nucleotide analog.
    PacBio responds that its obviousness arguments be-
    fore the Board were based on the combination of the ’375
    patent with the ’614 patent, not Laird, and that ITRI does
    not dispute that the ’614 patent teaches discriminating
    nucleotide analogs. PacBio thus argues that, to the
    extent the Board erred in finding that Laird teaches a
    discriminating nucleotide analog, that error is harmless
    because claims 27 and 28 would have been obvious in
    view of the ’375 and ’614 patents. PacBio also argues that
    the Personal Genomes presentation does not teach away
    from the use of a discriminating nucleotide analog or the
    use of a base-linked nucleotide analog in general.
    We agree with ITRI that the Board erred in conclud-
    ing that claims 27 and 28 would have been obvious over
    the combination of the ’375 patent and Laird. The claims
    require the use of a “nucleotide analog that discriminates
    between a base and its modified form.” The ’630 patent
    explains that a “discriminating analog . . . pairs preferen-
    tially with one but not the other of the base and its modi-
    fied form.” ’630 patent col. 24 ll. 15–19. The Board did
    not find, and PacBio does not contend, that either the ’375
    patent or Laird teaches such a discriminating nucleotide
    analog. The Board only found that Laird taught “discrim-
    inating between methylated and non-methylated cyto-
    sines.” Board Decision, 
    2014 WL 4381078
    , at *23. But
    Laird’s method uses bisulfite to convert C to U and then
    distinguishes C from mC for the fact that U pairs with A
    20       INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    and mC pairs with G. The Board did not otherwise indi-
    cate why the “discriminating nucleotide analog” limitation
    would have been obvious in view of the record evidence.
    Although the ’614 patent, cited by PacBio, does dis-
    close discriminating nucleotide analogs, the parties dis-
    pute whether the Personal Genomes presentation teaches
    away from combining the ’375 and ’614 patents. ITRI
    argued to the Board that the Personal Genomes presenta-
    tion taught away from using base-linked analogs in the
    sequencing methods described in the ’375 patent. J.A.
    344. But the Board did not consider the disclosure of the
    Personal Genomes presentation, after finding that it was
    not prior art under 35 U.S.C. § 102(b). Board Decision,
    
    2014 WL 4381078
    , at *13 n.27. The Board did not consid-
    er whether the Personal Genomes presentation would
    qualify as prior art under other subsections of § 102, such
    as § 102(a).
    Whether the prior art teaches away from the claimed
    invention is a question of fact. 
    Mouttet, 686 F.3d at 1330
    .
    The Board did not consider some of the cited prior art,
    including the Personal Genomes presentation, and it did
    not properly determine whether a skilled artisan would
    have pursued the method of claims 27 and 28, which uses
    a discriminating nucleotide analog. We therefore vacate
    the obviousness determination as to claims 27 and 28 and
    remand for further proceedings at the Board.
    II.   CROSS-APPLICABILITY OF THE PRIOR ART
    Section 41.207(c) of Title 37 of the Code of Federal
    Regulations provides:
    When a motion for judgment of unpatentability
    against an opponent’s claim on the basis of prior
    art is granted, each of the movant’s claims corre-
    sponding to the same count as the opponent’s
    claim will be presumed to be unpatentable in view
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES           21
    of the same prior art unless the movant in its mo-
    tion rebuts this presumption.
    37 C.F.R. § 41.207(c) (cross-applicability of prior art).
    Before the Board, PacBio asserted the ’375 patent,
    which it owns, as prior art under 35 U.S.C. § 102(e), and
    it sought to establish common ownership of the ’375
    patent and its ’673 and ’178 applications under § 103(c),
    in order to disqualify the ’375 patent as prior art against
    itself. When the Board granted PacBio’s obviousness
    motion, invalidating all of ITRI’s claims, it did not opine
    on the patentability of PacBio’s claims or otherwise indi-
    cate whether PacBio has overcome the presumption of
    cross-applicability of the cited prior art.
    ITRI argues that the Board erred by failing to hold
    PacBio’s claims unpatentable pursuant to 37 C.F.R.
    § 41.207(c). ITRI also argues that PacBio failed to rebut
    the presumption of cross-applicability, and that the Board
    incorrectly analyzed common ownership under 35 U.S.C.
    § 103(c). PacBio responds that it has rebutted any pre-
    sumption of cross-applicability by explaining to the Board
    that the ’375 patent does not preclude patentability of its
    claims under § 103(c) and by submitting a declaration
    with its reply. PacBio also argues that the Board properly
    exercised its discretion not to apply the presumption.
    On this record, it is unclear whether the Board implic-
    itly determined that PacBio has overcome the presump-
    tion of cross-applicability or whether the Board decided
    not to apply the prior art to PacBio’s claims for some other
    reason. Because we affirm the obviousness determination
    as to claims 1–22 and 24–26 of ITRI’s ’630 patent and
    remand the case for further determinations as to claims
    23, 27, and 28 of that patent, the Board will have another
    opportunity to address the cross-applicability issue.
    The record does show, however, that the Board might
    have misunderstood what was required to disqualify prior
    22       INDUSTRIAL TECH. RESEARCH INST.    v. PAC. BIOSCIENCES
    art under 35 U.S.C. § 103(c). In an August 2014 decision
    denying ITRI’s motion to strike PacBio’s reply brief and
    accompanying declaration, the Board reasoned:
    It is therefore evident that, regardless of who the
    inventors of the ’375 patent and ’673 and ’178 ap-
    plications were, the Moore Declaration provides
    evidence in support of PacBio’s contention that
    the patent and applications had been assigned to,
    and were owned by, PacBio. That PacBio is the
    assignee of the ’375 patent and ’673 and ’178 ap-
    plications, no matter who the inventors were, is not
    disputed by the parties. To that extent, viz., the
    issue of common ownership, the Board will con-
    sider the evidentiary weight of the Moore Declara-
    tion in support of PacBio’s arguments. With
    respect to inventorship, the Board will defer that
    issue to the priority phase of the interference . . . .
    Indus. Tech. Research Inst. v. Pac. Biosciences of Cal.,
    Inc., Interference No. 105,970, Paper 166, at *9 (P.T.A.B.
    Aug. 11, 2014) (first emphasis in original) (second and
    third emphases added) (J.A. 480).
    It appears that the Board might have misapplied
    § 103(c) by reasoning that the assessment of common
    ownership may be based on evidence of common owner-
    ship by assignment, even if the assignment occurred after
    the application filing date. 35 U.S.C. § 103(c) provides
    that § 102(e) prior art does not preclude patentability if
    “the subject matter [of the prior art] and the claimed
    invention were, at the time the claimed invention was
    made, owned by the same person or subject to an obliga-
    tion of assignment to the same person” (emphasis added).
    Accordingly, evidence of common ownership by assign-
    ment after the application filing date does not establish
    common ownership or an obligation to assign ownership
    at the time of the invention.
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES         23
    We therefore remand for a determination of the cross-
    applicability of the cited prior art to PacBio’s claims and,
    if necessary, a proper analysis of common ownership of
    the ’375 patent and the ’673 and ’178 applications.
    III. WRITTEN DESCRIPTION IN THE ’551 APPLICATION
    Sufficiency of written description is a question of fact,
    which we review for substantial evidence. Ariad Pharm.,
    Inc. v. Eli Lilly & Co., 
    598 F.3d 1336
    , 1351 (Fed. Cir.
    2010) (en banc). Claims must be sufficiently supported by
    the written description of a patent, such that the disclo-
    sure “reasonably conveys to those skilled in the art that
    the inventor had possession of the claimed subject matter
    as of the filing date.” 
    Id. To receive
    the benefit of an
    earlier application in an interference, the application
    must contain an adequate written description of at least
    one embodiment of the count. Tobinick v. Olmarker, 
    753 F.3d 1220
    , 1227 (Fed. Cir. 2014).
    ITRI argues that the Board erred in designating Pac-
    Bio the senior party because the ’551 application lacks a
    written description of the Count, in particular, any ex-
    press or inherent disclosure of using mismatched base
    pairs to determine modified base positions. According to
    ITRI, paragraph 17 of the ’551 application, including its
    reference to comparing the forward and reverse strands,
    merely describes using base-pair matches, not mismatch-
    es, to confirm the reliability of sequencing data. ITRI also
    asserts that the ’551 application disclaims the bisulfite
    embodiment of the Count because the ’551 application
    states that its methods do not “rel[y] on the similarity of
    uracil to thymine.” Appellant’s Br. 41 (quoting ’551
    application ¶ 23). ITRI explains that the Count relies on
    the similarity of U and T, because, when U is the modified
    base after bisulfite treatment, the claimed method relies
    on the fact that both U and T pair with A in sequencing.
    PacBio responds that the Board correctly found that
    the ’551 application discloses an embodiment of the Count
    24      INDUSTRIAL TECH. RESEARCH INST.   v. PAC. BIOSCIENCES
    because it expressly discloses (1) a CPLM DNA sequenc-
    ing template, (2) the use of bisulfite treatment, and (3) the
    comparison of forward and reverse strands of the CPLM
    to identify modified bases. PacBio argues that the Count
    does not require using mismatches to determine the
    positions of modified bases. PacBio also argues in the
    alternative that, even if the Count did require the use of
    mismatches, the Board’s factual finding of adequate
    written description is supported by substantial evidence,
    which includes the ’551 application’s express disclosures
    and the detailed testimony of PacBio’s expert witness
    explaining the disclosures of the ’551 application.
    As 
    indicated supra
    , we conclude that the Board
    properly interpreted the Count as requiring the use of
    mismatched base pairs in detecting modified base posi-
    tions. Under that construction, we conclude that substan-
    tial evidence supports the Board’s finding that the ’551
    application adequately describes an embodiment of the
    Count. The ’551 application describes methods of detect-
    ing modified bases. The application discloses a CPLM
    template, as well as the use of bisulfite to convert C, but
    not mC, to U. J.A. 918–20. The application defines “modi-
    fied bases” as including “methylated bases” and “bisulfite-
    converted bases.” J.A. 919.
    Importantly, the application states in paragraph 17
    that “sequence reads from the sense or ‘forward’ strand
    can be compared to sequence reads from the antisense or
    ‘reverse’ strand for the same nucleic acid template to
    further validate the existence of one or more modified
    bases in the template nucleic acid.” J.A. 918 (emphases
    added). That is an explicit reference to comparing the
    forward and reverse strands and using base-pair matches
    and mismatches to detect modified bases. Although other
    portions of the ’551 application describe prior-art consen-
    sus sequencing technique, those disclosures do not alter
    the explicit reference to “compar[ing]” the forward and
    reverse strand sequences to determine “the existence of
    INDUS. TECH. RESEARCH INST.   v. PAC. BIOSCIENCES      25
    one or more modified bases.” Likewise, we find ITRI’s
    argument that paragraph 23 of the application disclaims
    the bisulfite embodiment of the Count to be unpersuasive.
    We therefore affirm the Board’s finding that the ’551
    application provides an adequate written description of at
    least one embodiment of the Count.
    CONCLUSION
    We have considered the parties’ remaining argu-
    ments, but find them unpersuasive. For the foregoing
    reasons, we affirm the Board’s decision that claims 1–22
    and 24–26 of ITRI’s ’630 patent would have been obvious
    over the cited references and that PacBio’s ’551 applica-
    tion contains an adequate written description of an em-
    bodiment of the Count. Additionally, we vacate the
    Board’s obviousness judgment as to claims 23, 27, and 28
    of the ’630 patent and remand for a further determination
    of the patentability of those claims and for the Board to
    address the cross-applicability of the cited prior art to
    PacBio’s involved claims.
    AFFIRMED IN PART, VACATED IN PART, AND
    REMANDED
    COSTS
    No costs.