Tris Pharma, Inc. v. Actavis Laboratories Fl, Inc. ( 2018 )


Menu:
  •        NOTE: This disposition is nonprecedential.
    United States Court of Appeals
    for the Federal Circuit
    ______________________
    TRIS PHARMA, INC.,
    Plaintiff-Appellant
    v.
    ACTAVIS LABORATORIES FL, INC.,
    Defendant-Appellee
    ______________________
    2017-2557, 2017-2559, 2017-2560
    ______________________
    Appeals from the United States District Court for the
    District of Delaware in Nos. 1:14-cv-01309-GMS, 1:15-cv-
    00393-GMS, 1:15-cv-00969-GMS, Judge Gregory M. Sleet.
    ______________________
    Decided: November 20, 2018
    ______________________
    ERROL TAYLOR, Milbank, Tweed, Hadley & McCloy,
    LLP, New York, NY, argued for plaintiff-appellant. Also
    represented by ANNA BROOK, JORDAN P. MARKHAM,
    FREDERICK ZULLOW.
    WILLIAM M. JAY, Goodwin Procter LLP, Washington,
    DC, argued for defendant-appellee. Also represented by
    BRIAN TIMOTHY BURGESS, WILLIAM G. JAMES, II; DAVID
    ZIMMER, Boston, MA; ELIZABETH HOLLAND, LINNEA P.
    CIPRIANO, MICHAEL B. COTTLER, CYNTHIA LAMBERT
    2           TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    HARDMAN, TIFFANY MAHMOOD, ALEXANDRA D. VALENTI,
    New York, NY.
    ______________________
    Before NEWMAN, O’MALLEY, and CHEN, Circuit Judges.
    CHEN, Circuit Judge.
    Tris Pharma, Inc. (Tris) holds the approved New Drug
    Application for Quillivant XR®, an extended release
    methylphenidate (MPH) formulation for the treatment of
    Attention Deficit Hyperactive Disorder (ADHD). When
    Actavis Laboratories, Inc. (Actavis) submitted an Abbre-
    viated New Drug Application (ANDA) to the U.S. Food &
    Drug Administration (FDA) seeking approval to market
    generic versions of Quillivant XR®, Tris sued Actavis for
    infringement of U.S. Patent Nos. 8,465,765 (’765 patent),
    8,563,033 (’033 patent), 8,778,390 (’390 patent), 8,956,649
    (’649 patent), and 9,040,083 (’083 patent). After a five-day
    bench trial, the district court found all asserted claims of
    the patents-in-suit invalid under 
    35 U.S.C. § 103
    . Tris
    appealed. Because the district court’s conclusions of law
    are based on inadequate fact-findings, we vacate and
    remand.
    BACKGROUND
    MPH is one of the most widely prescribed psychost-
    imulants and has been used to treat ADHD since the mid-
    1950s. Early formulations of MPH were immediate
    release (IR) forms of the drug that exhibited clinical
    benefits within 20 to 60 minutes after dosing and whose
    effects lasted 2–4 hours. IR forms of MPH, however, had
    drawbacks because they had to be administered multiple
    times a day, making it challenging for patients to adhere
    to the dosing schedule. Sustained release (SR) formula-
    tions of MPH were thus developed and available in the
    early 1980s for greater dosing convenience and patient
    compliance. But those first-generation SR formulations
    had their own shortcoming: a slow onset of action. Tris’s
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.         3
    Quillivant XR® is an extended release formulation of MPH
    comprising an IR component and a SR component. It is a
    formulation that achieves a 45-minute therapeutic onset
    and 12 hours of therapeutic effect.
    Actavis challenged the validity of twenty-one claims
    from five patents at the district court, which found all
    these claims invalid under 
    35 U.S.C. § 103
    . On appeal,
    Tris requests that we reverse the district court’s judgment
    for seven claims in three patents: ’765, ’033, and ’390
    patents. These seven appealed claims are: claims 4 and
    10 of the ’033 patent; claims 6 and 20 of the ’765 patent;
    and claims 15, 16, and 20 of the ’390 patent. All of the
    appealed claims are directed to pharmacokinetic (PK) and
    pharmacodynamic (PD) properties of the Quillivant XR®
    extended release formulation. 1 These properties include:
    (1) an extended duration of action of about 12 hours; (2) a
    single mean peak PK profile; (3) a Tmax of about 4 to 5.25
    hours (early Tmax); and (4) a 45-minute onset of ac-
    tion/therapeutic effects. All of the claims on appeal recite,
    among other properties, a single mean peak PK profile
    and 12-hour duration of effect limitation. All of the
    claims except for claim 20 of the ’765 patent recite the
    early Tmax limitation, and claim 10 of the ’033 patent and
    claim 20 of the ’765 patent are the only two claims that
    require a 45-minute onset of action. Claim 10 of the ’033
    1   Pharmacokinetics is the study of what a person’s
    body does to a drug after administration. PK values are
    measurements of a drug’s behavior in a patient’s blood
    plasma. One such value relevant for this appeal, Tmax,
    represents the time after administration when the maxi-
    mum concentration of the drug in the blood plasma (Cmax)
    occurs. The shape of the PK profile, which reflects the
    plasma concentration of the drug in the patient’s body
    over time, is also an issue in dispute in this case.
    4         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    patent is thus the only asserted claim that recites all four
    properties.
    A. Prior Art
    The district court found that the various combinations
    of the PK characteristics (single mean peak and early
    Tmax) and PD characteristics (a 45-minute onset of action
    and a 12-hour duration of effect) claimed in the patents-
    in-suit would have been obvious over the prior art. The
    prior art consists of a number of commercially available,
    second-generation, extended release formulations of MPH
    including Concerta®, Daytrana®, Focalin XR®, Metadate
    CD®, and Ritalin LA®; 2 scientific articles; and U.S. Patent
    Application Publication No. 2010/0260844 (Scicinski).
    Below, we briefly describe the prior art relevant to this
    appeal.
    Concerta® is an extended release MPH tablet with a
    12-hour duration of effect. J.A. 18, 23. The parties dis-
    pute whether or not Concerta® exhibits the single mean
    peak PK profile limitation because its plasma concentra-
    tion profile exhibits a sharp initial increase followed by a
    second increase. J.A. 19, 25. The parties also dispute
    whether Concerta® exhibits a 45-minute onset of action.
    Tris’s expert testified that the clinical efficacy study he
    performed showed that Concerta® has a 2-hour onset of
    action, J.A. 2213–14, while Actavis’s expert testified that
    second-generation products like Concerta® generally have
    an onset of action between 30 minutes to 2 hours. J.A.
    2  The district court also listed Methylin ER as a
    commercially available controlled-release formulation.
    J.A. 16. Confusingly, it later presented PK data for
    Methylin Oral Solution. J.A. 22. We decline to discuss
    the Methylin prior art reference because it is unclear on
    which version the district court is relied.
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.         5
    2069. Concerta® has a later Tmax of around 6.8 ± 1.8
    hours. J.A. 2098.
    Daytrana® is an MPH patch that exhibits a single
    mean peak PK profile and a 12-hour duration of effect.
    J.A. 2215, 2069. However, Daytrana® has a 2-hour onset
    of action, and the record as to its Tmax is unclear. J.A.
    2069.
    Focalin XR® is an extended release MPH capsule.
    While it achieves the claimed 12-hour duration of effect,
    JA 2069, and 45-minute onset of action, J.A. 3923, its PK
    profile does not exhibit a single mean peak, and it exhib-
    its a later Tmax around 6.5 hours. J.A. 2080, 2214–15,
    2297. Moreover, Tris notes that Focalin XR® only consists
    of a single enantiomer d-MPH as the active ingredient
    whereas Quillivant XR® and the appealed claims include
    both enantiomers.
    Metadate CD® is a capsule version of MPH. J.A. 19.
    While it has an early Tmax of about 4.5 hours, J.A. 2297,
    and a 45-minute onset of action, J.A. 2069, the parties
    disagree as to whether its PK profile exhibits a single
    mean peak and whether it has a 12-hour duration of
    effect. J.A. 22–23. Like Concerta®, Metadate CD®’s PK
    profile exhibits a sharp initial increase followed by a
    second increase in MPH levels at a later time. J.A. 19.
    As for its duration of effect, Tris presented testimony that
    Metadate CD®’s effects only last 6 to 8 hours. J.A. 2069,
    2204.
    Ritalin LA® is a capsule version of MPH. J.A. 21. Ri-
    talin LA® exhibits an early Tmax at 5.5 hours and an early
    onset of action. J.A. 2069, 2099. Its PK profile exhibits
    two peaks (bimodal), J.A. 2615, and it only has 6–8 hours
    of effect. J.A. 2069.
    Scincinski describes a formulation of MPH that pro-
    vides a rapid onset of action within 1 to 1.5 hours, a single
    6         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    Tmax of 5.5 to 7.5 hours, and a therapeutic duration of
    about 12 to 14 hours. J.A. 3644.
    B. District Court Opinion
    Actavis characterized Scincinski as well as the Day-
    trana®, Concerta®, and Metadate CD® formulations as all
    disclosing a single mean peak PK profile, exhibiting an
    early onset of action, and exhibiting an extended duration
    of effect. This, Actavis argued, would have suggested to a
    skilled artisan that a single mean peak PK profile could
    provide the claimed early onset of action and extended
    duration of effect. Tris disagreed for two primary reasons.
    First, the prior art formulations were developed using
    two components: IR and ER formulations of MPH. These
    two components together in a formulation typically re-
    sulted in two peaks, or a bimodal profile, with the first
    peak resulting from the IR component of the formulation
    and the second from the ER component. Further, Tris
    asserted that this bimodal profile was important to coun-
    teract “acute tolerance” or “tachyphylaxis.” Acute toler-
    ance is the theory that as the day progresses, higher
    levels of the drug in the blood are required to produce the
    same therapeutic effects. Thus, in order to achieve sus-
    tained effects, the formulations in the prior art, according
    to Tris, were designed to mimic the peaks and valleys of
    multiple immediate release dosing regimens—one peak
    for the IR formulation and a second peak for the ER
    formulation.
    Second, Tris argued that prior art formulations of
    MPH have a late Tmax to achieve the sustained duration of
    action. To support this position, Tris pointed to Metadate
    CD® and Ritalin LA®, both of which have an early Tmax
    but a shorter duration of action of around 6 to 8 hours.
    Concerta®, on the other hand, achieves the 12-hour dura-
    tion of effect but has a later Tmax that is outside the
    claimed range of about 4 to 5.25.
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.         7
    The district court stated that, “[w]hile [it] believe[d]
    Tris’[s] evidence regarding the second generation products
    [wa]s persuasive, it [wa]s not dispositive on the obvious-
    ness inquiry.” J.A. 39. Rather, the district court found
    that Daytrana® clearly exhibits a single mean peak PK
    profile, and thus Actavis had demonstrated that a prior
    art reference taught this particular claim limitation.
    Importantly, the district court found that Scicinski
    describes an oral form of MPH with a long duration of
    action, rapid onset, and a single mean peak PK profile.
    The district court reasoned that a skilled artisan would
    have undoubtedly looked to Scicinski when formulating
    an extended release MPH drug because Scicinski’s pur-
    pose of a fast onset, long-lasting MPH formulation aligned
    with what the parties agreed a skilled artisan would have
    been motivated to achieve. The district court acknowl-
    edged that Scicinski describes a hypothetical product but
    declined to discount Scicinski simply because it contains a
    prophetic example. The district court also credited Ac-
    tavis’s expert’s testimony that skilled artisans would have
    used the known technique of deconvolution to achieve a
    product that meets the target PK profile like that de-
    scribed in Scicinski:
    Q: Now, once a person of ordinary skill in the art
    has decided on a target PK profile, at a very gen-
    eral level, what are the next steps towards mak-
    ing a product?
    A: Okay. The next steps would be to take this
    pharmacokinetic profile, this plasma profile and,
    utilizing certain mathematical techniques that are
    known as deconvolution, separate out the profile
    into its elimination characteristics and its absorp-
    tion characteristics, and once you define then
    simply the absorption characteristics of that
    product, then you can design a product that has
    dissolution characteristics that could match then
    8          TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    the absorption characteristics that you get by do-
    ing this deconvolution technique.
    J.A. 40 (citing J.A. 2095).
    Further, the district court appeared to credit Actavis’s
    expert’s testimony regarding the relationship between
    Tmax and duration of effect. Actavis’s expert testified that
    a skilled artisan would not have targeted a specific Tmax
    because that parameter does not control the onset or
    duration of the drug. He noted, moreover, that the
    claimed Tmax ranges in the prior art of 4.4 to 7 hours
    overlapped with the claimed range of 3.6 to 5.78 hours,
    taking into account the court’s construction of “about.”
    The district court then addressed Tris’s expert’s tes-
    timony that a skilled artisan would not have expected a
    formulation with a single mean peak PK profile to achieve
    both early onset and extended duration of action. Be-
    cause Tris’s expert testified that he would defer to a
    formulator in terms of what sort of PK curve could be
    achieved, the district court found Actavis’s formulator’s
    expert testimony that a skilled artisan would have no
    trouble achieving early onset of action and extended
    duration of effect with a single mean peak PK profile
    persuasive. The district court ultimately found that
    “Tris’[s] nonobvious[ness] argument hinges primarily on
    the [single peak] plasma profile and fails to sufficiently
    weigh the pharmacokinetic details that would have been
    known to skilled artisans or the prior art teachings that
    disclosed how to optimize an MPH product.” J.A. 42.
    The district court then examined objective indicia of
    nonobviousness, including unexpected results, long-felt
    need, commercial success, and copying. As to unexpected
    results, the district court held that Tris failed to demon-
    strate that the Quillivant XR® formulation exhibited some
    superior property or advantage that a skilled artisan
    would have found surprising or unexpected. J.A. 45
    (citing Procter & Gamble Co. v. Teva Pharm. USA, Inc.,
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.         9
    
    566 F.3d 989
    , 997 (Fed. Cir. 2009)). Tris argued that its
    formulation unexpectedly provided (1) a 45-minute onset
    of action and a 12-hour duration of effect with a single
    mean peak PK profile and (2) a 12-hour duration of effect
    with an early Tmax of about 4 to 5.25 hours. The district
    court found these arguments irrelevant because Tris had
    not performed the proper comparison to the closest prior
    art. 
    Id.
     (citing Kao Corp. v. Unilever U.S. Inc., 
    441 F.3d 963
    , 970 (Fed. Cir. 2006)). And even considering Tris’s
    unexpected results argument, the district court observed
    that the prior art would have led a skilled artisan to
    expect that a single peak PK profile could provide for
    rapid onset and extended duration of action. Thus, the
    district court concluded that Quillivant XR®’s 12-hour
    duration of effect and single mean peak PK profile was
    not unexpected.
    Regarding long-felt need, the district court found that
    the claimed Quillivant XR® formulation did not serve a
    long-felt but unmet need. The district court pointed to
    Tris’s own expert testimony that Metadate CD®, Ritalin
    LA®, and Concerta® had already achieved the goal of once
    daily dosing. Additionally, Tris’s expert also testified that
    some second-generation MPH formulations could have an
    onset of action in as early as 30 minutes. J.A. 2069. And
    while Tris’s expert testified that there was a long-felt
    need for a drug for children who had trouble swallowing
    pills that the Daytrana® patch did not meet due to skin
    irritation issues, J.A. 2272, the district court found that
    his own writings undermined this contention. J.A. 47
    (“This contention is undermined by Dr. McGough’s own
    writings where in the book he authored entitled ‘ADHD,’
    the doctor writes that Daytrana is a product that is ‘par-
    ticularly useful when swallowing is difficult.’”).
    As to commercial success, the district court found that
    Tris’s evidence only showed a modest level of commercial
    success. Finally, the district court found that evidence of
    copying was not compelling.
    10         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    Accordingly, the district court found all of Tris’s as-
    serted claims invalid for being obvious over the prior art.
    Tris appealed. We have jurisdiction pursuant to pursuant
    to 
    28 U.S.C. § 1295
    (a)(1).
    DISCUSSION
    “Obviousness is a question of law based on underlying
    findings of fact.” Perfect Web Techs., Inc. v. InfoUSA, Inc.,
    
    587 F.3d 1324
    , 1327 (Fed. Cir. 2009) (citing In re Kubin,
    
    561 F.3d 1351
    , 1355 (Fed. Cir. 2009)). We review the
    district court’s conclusions of law de novo. Eli Lilly & Co.
    v. Teva Parenteral Meds., Inc., 
    845 F.3d 1357
    , 1372 (Fed.
    Cir. 2017). And we review the district court’s factual
    findings for clear error. Par Pharm. Inc. v. TWI Pharm.,
    Inc., 
    773 F.3d 1186
    , 1194–95 (Fed. Cir. 2014).
    Under Fed. R. Civ. P. 52(a)(1), “[i]n an action tried on
    the facts without a jury or with an advisory jury, the court
    must find the facts specially and state its conclusions of
    law separately.” Rule 52(a) lays out the separate and
    distinct roles of the trial and the appellate court.
    “[F]actfinding is the basic responsibility of district courts,
    rather than appellate courts.        Pullman-Standard v.
    Swint, 
    456 U.S. 273
    , 291–92 (1982) (citing DeMarco v.
    United States, 
    415 U.S. 449
    , 450 n.* (1974)). A court of
    appeals should not resolve in the first instance a factual
    dispute which has not been considered by the district
    court. See 
    id.
     “When the opinion explaining the decision
    lacks adequate fact-findings, meaningful review is not
    possible, frustrating the very purpose of appellate review
    as well as this court’s compliance with its statutory man-
    date.” Gechter v. Davidson, 
    116 F.3d 1454
    , 1457 (Fed.
    Cir. 1997) (citation omitted). Findings of fact are ade-
    quate when “they are sufficiently comprehensive and
    pertinent to the issue to form a basis for the decision.”
    Medtronic, Inc. v. Daig Corp., 
    789 F.2d 903
    , 906 (Fed. Cir.
    1986) (quoting Loctite Corp. v. Ultraseal Ltd., 
    781 F.2d 861
    , 873 (Fed. Cir. 1985)). Although Rule 52(a)(1) does
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.        11
    not require detailed factual findings on every issue raised,
    it does require findings on “as many of the subsidiary
    facts as are necessary to disclose to the appellate court
    the steps by which the trial court determined factual
    issues and reached its ultimate conclusions.” Atlantic
    Thermoplastics Co., Inc. v. Faytex Corp., 
    5 F.3d 1477
    ,
    1479 (Fed. Cir. 1993).
    Tris raises three primary issues on appeal. First, Tris
    argues that a skilled artisan would not have reasonably
    expected to successfully combine the claimed single mean
    peak PK profile with the claimed 45-minute onset of
    action and 12-hour duration of effect (PD characteristics)
    because the PK-PD relationship was unknown. 3 Second,
    3    On appeal, Tris cites In re Cyclobenzaprine Hy-
    drochloride Extended-Release Capsule Patent Litigation,
    as being on all fours with this case. 
    676 F.3d 1063
     (Fed.
    Cir. 2012). In Cyclobenzaprine, we reversed the district
    court’s judgment of obviousness, holding that its “failure
    to appreciate the lack of a known PK/PD relationship for
    any formulation of cyclobenzaprine rendered deficient its
    analysis of the evidence . . . and its analysis of the impli-
    cations of that evidence on its legal conclusions of obvi-
    ousness.” 
    Id. at 1071
    . However, in Cyclobenzaprine, no
    extended release formulation of the drug was present in
    the prior art, and we found that without a known PK/PD
    relationship, “immediate-release PK values are of little
    use in calculating extended-release values, because there
    is no proof that a skilled artisan would expect the extend-
    ed release values to produce a therapeutic effect solely
    because they are drawn from immediate-release values.”
    
    Id.
     The present case is different because the prior art
    disclosed numerous existing extended-release formula-
    tions, some with one or a combination of single mean peak
    PK profile, extended duration, early onset, and early Tmax.
    12         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    Tris contends that the district court failed to address why
    the combination of an early Tmax and a 12-hour duration
    of effect would have been obvious. Third, Tris claims the
    district court mistakenly disregarded Tris’s evidence of
    unexpected results based on a belief that Tris’s experts
    did not compare the claimed invention to the closest prior
    art. Rather, Tris compared the Quillivant XR® formula-
    tion with the commercially available prior art formula-
    tions identified by the parties.
    As we explain below, the district court failed to make
    the necessary factual findings and provide sufficient
    analysis of the parties’ arguments to permit effective
    appellate review. Specifically, the district court’s opinion
    merely recites the parties’ arguments but fails to explain
    or identify which arguments it credits or rejects. We thus
    cannot reach the merits of whether the Quillivant XR®
    formulation would have been obvious over the prior art.
    Rather, we identify gaps in the district court’s opinion and
    remand for the district court to conduct further fact-
    findings and detailed analysis consistent with this opin-
    ion.
    A. Single Mean Peak PK Profile, 45-Minute Onset, and
    12-Hour Duration of Effect
    Claim 10 of the ’033 patent and claim 20 of the ’765
    patent require a liquid MPH formulation with (1) a single
    mean peak PK profile, (2) a 45-minute onset of action, and
    (3) a 12-hour duration of effect. ’033 patent col. 38 ll. 34–
    35; ’765 patent col. 39 ll. 16–17. The district court held
    that a skilled artisan would have found it obvious to use a
    formulation with a single mean peak PK profile to achieve
    a 45-minute onset of action and a 12-hour duration of
    Cyclobenzaprine is thus, factually distinguishable from
    this case.
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.        13
    effect. But the district court failed to make adequate
    findings of fact to support this holding.
    First, while the district court found that one would
    have expected from the prior art that a single mean peak
    PK profile could provide for rapid onset of action and
    extended duration of effect, J.A. 46, it never articulated
    which prior art references do so and how. The district
    court’s only clear finding on this point was its statement
    that formulations in the prior art such as Daytrana®
    exhibit a single mean peak PK profile. J.A. 37. The
    district court also recited Actavis’s expert’s testimony that
    Concerta® and Metadate CD® also have a single mean
    peak PK profile, despite having a slight initial peak or
    shoulder in their plasma concentration profiles followed
    by a larger single peak, and that Scicinski also teaches a
    single mean peak PK profile. J.A. 37, 41.
    But it is unclear if these statements amount to actual
    fact-findings as opposed to a mere recounting of Actavis’s
    arguments. Even if we were to interpret these statements
    as findings of fact, there are still holes in the district
    court’s analysis. For instance, the district court never
    made explicit findings that Daytrana®, Concerta®, Meta-
    date CD®, and/or Scicinski also teach a 45-minute onset of
    action or 12-hour duration of effect. And with respect to
    the 45-minute onset of action limitation, the district court
    cited a concession by Tris’s expert that second-generation
    MPH formulations could have an onset of action in as
    early as 30 minutes, but it did not explain the significance
    of this concession. 4 J.A. 47. And the district court did not
    4   Actavis argues that the Biederman article, a prior
    art reference relied upon by Tris’s expert, describes Con-
    certa® as having an onset of action in as early as 30
    minutes and a 12-hour duration of effect. J.A. 3446
    (Biederman, J. “New-Generation Long-Acting Stimulants
    14        TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    specifically identify which second-generation products
    have an onset of action around 30 minutes or state
    whether it believed that all second-generation MPH
    products, except Daytrana®, had this onset of action time.
    As for the 12-hour duration of effect limitation, the dis-
    trict court’s opinion is vague as to whether any of the
    prior art formulations actually teach the 12-hour duration
    of effect limitation. Throughout its analysis, the district
    court imprecisely states that certain prior art discloses
    “efficacy that last[s] throughout the day,” a “long duration
    of effect,” or an “extended duration of action.” See e.g.,
    J.A. 16, 36, 46. It is unclear, however, whether the dis-
    trict court intended this language to equate to the claimed
    12-hour duration of effect. We identify these issues
    because whether a particular prior art formulation
    achieves a 45-minute onset of action and/or a 12-hour
    duration of effect are central, disputed issues on appeal.
    And it is the role of the district court to resolve these
    specific fact issues with an explanation to support those
    findings.
    Second, and importantly, the district court does not
    address a fundamental aspect of the obviousness in-
    for the Treatment of Attention-Deficit/Hyperactivity
    Disorder,” Medscape Psychiatry 8(2) (Nov. 2003)). How-
    ever, the district court never cited this passage in its
    opinion. Also, the record is unclear as to whether Scicin-
    ski actually teaches the 45-minute onset of action limita-
    tion. Scicinski reports that its formulation would be
    effective “within about 1 to 1.5 hours post administra-
    tion.” ’844 application ¶ 0016. While Actavis’s expert
    testified that a skilled artisan would have viewed this
    disclosure as consistent with a 45-minute onset, the
    district court never directly made this fact-finding. J.A.
    2102.
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.       15
    quiry—i.e. why a skilled artisan would have been moti-
    vated to use a single mean peak PK profile to achieve a
    formulation with a 45-minute onset of action and/or a 12-
    hour duration of effect with a reasonable expectation of
    success. 5 Tris argued below and to us on appeal that the
    acute tolerance theory as well as the prior art taught
    away from using a single mean peak PK profile to achieve
    a 45-minute onset and a 12-hour duration of effect.
    According to Tris, the prior art extended release products
    with a single mean peak PK profile do not achieve either
    a 45-minute onset of action, a 12-hour duration of effect,
    or both. Tris argues that this is due to the acute tolerance
    theory, which postulates that the plasma concentration of
    a drug must be higher in a patient as the day progresses
    to achieve therapeutic efficacy, and therefore a bimodal
    (two-peak) plasma concentration curve is required. On
    appeal, Actavis argues that the acute tolerance theory is
    irrelevant to whether a drug has a single or bimodal peak
    PK profile, attempts to discredit the theory, and asserts
    that skilled artisans did not regard the number of peaks
    as important when formulating a drug. But the district
    court made none of these findings below. Other than
    explaining what the acute tolerance theory is, J.A. 38 n.8,
    5   We understand that one of Actavis’s arguments on
    appeal is that Quillivant XR®’s single mean peak PK
    profile and early Tmax range are incidental properties of
    the formulation. That is, these PK limitations played no
    role in Quillivant XR®’s development. The PK character-
    istics are specifically claimed in the patents-in-suit,
    however, and Actavis has not suggested that these limita-
    tions are not entitled to patentable weight. Thus, Actavis
    needs to demonstrate that a skilled artisan would have
    been motivated to create a liquid formulation of MPH
    with these claimed PK characteristics and specific PD
    properties.
    16         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    and reciting Tris’s expert testimony explaining why acute
    tolerance was one of the reasons a first-generation MPH
    formulation like Ritalin-SR® could not achieve the desired
    clinical effects of a fast onset and extended duration, J.A.
    38, the district court did not address the acute tolerance
    theory. It is thus unclear whether the district court found
    that (1) the theory is not applicable because it does not
    affect the shape of the plasma concentration curve; (2) the
    theory is unreliable; or (3) the theory is applicable, but
    even acknowledging it, a skilled artisan would have a
    reasonable expectation of success to combine a single
    mean peak curve with a 45-minute onset of action and a
    12-hour duration of effect. And we decline to guess at
    what the district court meant.
    Without the requisite factual findings and adequate
    explanation for such findings, we cannot affirm the dis-
    trict court’s conclusion that a formulation with (1) a single
    mean peak PK profile, (2) 45-minute onset of action, and
    (3) 12-hour duration of effect would have been obvious
    over the prior art. See Golden Blount, Inc. v. Robert H.
    Peterson Co., 
    365 F.3d 1054
    , 1061 (Fed. Cir. 2004) (“Be-
    cause the district court’s sparse opinion provides this
    court with only bald conclusions for review, we conclude
    that the district court’s judgment . . . is insufficient under
    Rule 52(a). We thus vacate those portions of the district
    court’s opinion and remand those issues to the district
    court for specific factual findings.”); see also Atlantic
    Thermoplastics Co., 
    5 F.3d at 1479
     (finding the court’s
    opinion too conclusory and sparse to provide a factual
    basis for determining whether the invention was on sale
    within the meaning of 
    35 U.S.C. § 102
    (b)). Accordingly,
    we remand this issue to the district court for further fact-
    finding.
    B. Early Tmax and 12-Hour Duration of Effect
    Claims 4 and 10 of the ’033 patent; claim 6 of the ’765
    patent; and claims 15, 16, and 20 of the ’390 patent recite
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.        17
    a liquid formulation of MPH with a single Tmax of about 4
    to 5.25 hours and a 12-hour duration of effect. ’033 patent
    col. 38 ll. 3–5, 34–35; ’765 patent col. 38 ll. 4–13; ’390 at
    col. 39 ll. 3–11, 27–29. On appeal, Tris argues that the
    district court never provided its assessment of the obvi-
    ousness of a MPH formulation with both an early Tmax
    and 12-hour duration of effect. We agree.
    The district court’s analysis with respect to Tmax is
    very cursory. The entirety of the district court’s discus-
    sion of Tmax appears amounts to a mere recitation of
    Actavis’s experts’ testimony regarding how (1) Tmax does
    not control the onset or duration of effect and (2) Tmax
    ranges in the prior art formulations overlap with the
    claimed Tmax range of 3.6 to 5.78 hours (factoring in the
    district court’s construction of “about”). J.A. 41. And, yet
    again, the district court fails to articulate whether it
    credited this testimony or explain why and how the
    testimony supports its conclusion. Even if we were to
    assume that these statements were actual findings of fact,
    the district court’s analysis still fails to explain why a
    skilled artisan would have reasonably expected to achieve
    a formulation with the claimed 12-hour duration of effect
    and an early Tmax.
    The district court’s opinion lacks any response to
    Tris’s argument that formulations with an early Tmax
    (such as Metadate CD® and Ritalin LA®) did not achieve
    12 hours of effect while those with 12 hours of effect
    (Concerta® and Focalin XR®) had later Tmax values. Tris’s
    expert explained that this was because oral formulations
    only contain a certain amount of any drug; if the formula-
    tion releases a substantial amount of the drug to obtain
    an early Tmax, then the formulation would not be expected
    to achieve extended effects for the whole day. J.A. 2204.
    While Actavis’s expert responded to this in his testimony,
    J.A. 2101, the district court opinion does not discuss or
    cite Tris’s testimony.
    18         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    As with the single mean peak PK profile, 45-minute
    onset of action, and 12-hour duration of effect combination
    of limitations, we also remand the obviousness of the
    combination of an early Tmax with a 12-hour duration of
    effect to the district court for further consideration.
    C. Objective Indicia of Nonobviousness
    Tris argues on appeal that the district court incorrect-
    ly rejected Tris’s experts’ testimony on unexpected results
    because they purportedly failed to compare the Quillivant
    XR® formulation with the closest prior art. We agree.
    Tris’s experts compared the Quillivant XR® formulation to
    all prior art products whose PK and PD values were cited
    by Actavis or known to Tris. J.A. 2708–13. While Kao
    stands for the proposition that “when unexpected results
    are used as evidence of nonobviousness, the results must
    be shown to be unexpected compared with the closest
    prior art,” we do not read Kao so rigidly as to require Tris
    to identify and focus on just one prior art product when
    multiple, similar extended release formulations of MPH
    existed or were described in the prior art. 
    441 F.3d at 970
    . Because the patents-in-suit claim multiple PK and
    PD characteristics, different prior art references are
    closer on different PK and PD characteristics, and none of
    the parties asserted that one of the references or products
    represented the closest art. Under the circumstances
    here, the district court should have considered Tris’s
    evidence that its claimed invention enjoyed unexpected
    properties compared to the known, extended release
    formulations.
    Moreover, even though the district court went on to
    consider the merits of Tris’s unexpected results argument,
    the district court’s analysis is deficient because it, at best,
    only addresses the single mean peak PK limitation. J.A.
    46. The district court does not explain why—separately,
    and more importantly together with the single mean peak
    PK profile limitation—the Tmax, 45-minute onset, and 12-
    TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.       19
    hour duration of effect limitations were not unexpected.
    Thus, we remand the issue of unexpected results to the
    district court for further analysis.
    Additionally, Tris also argues that the district court
    incorrectly rejected its evidence of long-felt need based on
    second-generation products that lack one or more of the
    long-felt needs Tris identified. Below, Tris argued that
    there was a long-felt need for a product having several
    desired properties: (1) a liquid MPH product that does not
    require swallowing a tablet; (2) a 45-minute onset of
    action; and (3) 12-hour duration of effect. None of the
    prior art products, Tris contends, satisfied this alleged
    long-felt need because none of them possess all three of
    these properties.
    In rejecting Tris’s long-felt need argument, the dis-
    trict court opinion identified various prior art products
    that meet each of the three individual needs above, but
    never identified a prior art product that contains all three
    properties. For instance, Daytrana® can be administered
    to individuals without requiring them to swallow a pill;
    Metadate CD®, Ritalin LA®, and Concerta® are adminis-
    tered once daily. J.A. 44. The district court also found
    that second generation prior art products generally have
    an onset of action of as early as 30 minutes. 
    Id.
     But
    finding each of the properties in separate prior art prod-
    ucts does not adequately address Tris’s specific theory as
    to a long-felt need for all three desired properties to be
    contained a single product. Actavis contends that any
    differences in onset, duration, and formulation between
    Quillivant XR® and particular prior art products were too
    insignificant to establish any unsolved long-felt need, but
    the district court did not make such a finding for us to
    review. Accordingly, we remand the long-felt need issue
    to the district court for further consideration.
    20         TRIS PHARMA, INC. v. ACTAVIS LABORATORIES FL, INC.
    In view of the errors we identified above, we invite the
    district court to reconsider all the evidence of objective
    indicia in its overall determination of obviousness.
    CONCLUSION
    Because district court’s obviousness decision lacks the
    requisite fact-finding, and because the district court erred
    in rejecting Tris’s evidence of objective indicia of nonobvi-
    ousness, we remand the obviousness analysis to the
    district court for further fact-finding. We have considered
    the parties’ other arguments and find them unpersuasive.
    VACATED AND REMANDED
    COSTS
    No Costs.