Celgene Corporation v. Peter , 931 F.3d 1342 ( 2019 )


Menu:
  •   United States Court of Appeals
    for the Federal Circuit
    ______________________
    CELGENE CORPORATION,
    Appellant
    v.
    LAURA A. PETER, DEPUTY UNDER SECRETARY
    OF COMMERCE FOR INTELLECTUAL PROPERTY
    AND DEPUTY DIRECTOR OF THE UNITED
    STATES PATENT AND TRADEMARK OFFICE,
    Intervenor
    ______________________
    2018-1167, 2018-1168, 2018-1169
    ______________________
    Appeals from the United States Patent and Trademark
    Office, Patent Trial and Appeal Board in Nos. IPR2015-
    01096, IPR2015-01102, IPR2015-01103.
    --------------------------------------------------
    CELGENE CORPORATION,
    Appellant
    v.
    LAURA A. PETER, DEPUTY UNDER SECRETARY
    OF COMMERCE FOR INTELLECTUAL PROPERTY
    AND DEPUTY DIRECTOR OF THE UNITED
    STATES PATENT AND TRADEMARK OFFICE,
    Intervenor
    ______________________
    2                             CELGENE CORPORATION v. PETER
    2018-1171
    ______________________
    Appeal from the United States Patent and Trademark
    Office, Patent Trial and Appeal Board in No. IPR2015-
    01092.
    ______________________
    Decided: July 30, 2019
    ______________________
    GREGORY A. CASTANIAS, Jones Day, Washington, DC,
    argued for appellant. Also represented by JIHONG LOU,
    JENNIFER LORAINE SWIZE; GASPER LAROSA, New York, NY;
    ANTHONY INSOGNA, San Diego, CA; FRANK CHARLES
    CALVOSA, F. DOMINIC CERRITO, ANDREW CHALSON, Quinn
    Emanuel Urquhart & Sullivan, LLP, New York, NY.
    AMY J. NELSON, Office of the Solicitor, United States
    Patent and Trademark Office, Alexandria, VA, argued for
    intervenor.   Also represented by MEREDITH HOPE
    SCHOENFELD, THOMAS W. KRAUSE.           Also argued by
    KATHERINE TWOMEY ALLEN, Appellate Staff, Civil Division,
    United States Department of Justice, Washington, DC.
    Also represented by MARK R. FREEMAN, SCOTT R.
    MCINTOSH, JOSEPH H. HUNT.
    ______________________
    Before PROST, Chief Judge, BRYSON and REYNA,
    Circuit Judges.
    PROST, Chief Judge.
    The Coalition for Affordable Drugs VI LLC (“CFAD”)
    filed a petition for inter partes review (“IPR”) challenging
    the validity of all of the claims of 
    U.S. Patent No. 6,045,501
    (“the ’501 patent”) and three petitions for IPR challenging
    the validity of all of the claims of 
    U.S. Patent No. 6,315,720
    (“the ’720 patent”). The Patent Trial and Appeal Board
    CELGENE CORPORATION v. PETER                                3
    (“Board”) determined that all of the claims of the ’501
    patent and claims 1–9 and 11–32 of the ’720 patent were
    obvious. Celgene Corporation (“Celgene”) appeals the
    Board’s decisions.
    For the reasons explained below, we affirm the Board’s
    decisions finding the appealed claims obvious. We also
    hold that the retroactive application of IPR proceedings to
    pre-AIA patents is not an unconstitutional taking under
    the Fifth Amendment.
    I
    A
    A teratogen is an agent known to disturb the
    development of an embryo or fetus. Teratogenic drugs can
    cause birth defects or other abnormalities following fetal
    exposure during pregnancy. One example of a teratogenic
    drug is thalidomide. Thalidomide, first synthesized in
    1957, was originally marketed for use as a sedative in
    many countries, not including the United States. See ’501
    patent col. 1 ll. 19–22. Following reports of serious birth
    defects, thalidomide was withdrawn from all markets by
    1962. 
    Id.
     at col. 1 ll. 22–24. Despite these teratogenic
    effects, thalidomide has proven to be effective in treating
    other conditions. See 
    id.
     at col. 1 ll. 24–35. The ’501 patent
    and the ’720 patent are generally directed to methods for
    safely distributing teratogenic or other potentially
    hazardous drugs while avoiding exposure to a fetus to
    avoid adverse side effects of the drug.
    B
    In order to obtain FDA approval to sell and distribute
    thalidomide, Celgene developed a system to safely
    distribute thalidomide to patients, which it called the
    System for Thalidomide Education and Prescription Safety
    (“Original S.T.E.P.S.”). Appeal No. 18-1171, Appellant’s
    Br. 8–9. According to Celgene, the ’501 patent is directed
    to its Original S.T.E.P.S. program. See 
    id. at 10
    .
    4                            CELGENE CORPORATION v. PETER
    Celgene’s ’501 patent relates to “methods for delivering
    a drug to a patient while preventing the exposure of a
    foetus or other contraindicated individual to the drug.”
    ’501 patent at Abstract. Claim 1 is representative and
    states:
    1. A method for delivering a teratogenic drug to
    patients in need of the drug while avoiding the
    delivery of said drug to a foetus comprising:
    a. registering in a computer readable storage
    medium prescribers who are qualified to
    prescribe said drug;
    b. registering in said medium pharmacies to fill
    prescriptions for said drug;
    c. registering said patients in said medium,
    including information concerning the ability of
    female patients to become pregnant and the
    ability of male patients to impregnate females;
    d. retrieving from said medium information
    identifying a subpopulation of said female
    patients who are capable of becoming pregnant
    and male patients who are capable of
    impregnating females;
    e. providing to the subpopulation, counseling
    information concerning the risks attendant to
    fetal exposure to said drug;
    f. determining whether patients comprising
    said subpopulation are pregnant; and
    g. in response to a determination of non-
    pregnancy for said patients, authorizing said
    registered pharmacies to fill prescriptions from
    said registered prescribers for said non-
    pregnant registered patients.
    CELGENE CORPORATION v. PETER                              5
    
    Id.
     at claim 1. Claim 2 recites “[t]he method of claim 1
    wherein said drug is thalidomide.” The remaining claims
    depend from claim 1 and are not limited to thalidomide.
    CFAD filed a petition for IPR challenging all ten claims
    of the ’501 patent. The Board instituted review of claims
    1–10 on a single ground—obviousness based on Powell, 1
    Mitchell, 2 and Dishman. 3 Coalition for Affordable Drugs
    VI LLC v. Celgene Corp., No. IPR2015-01092, Paper 20
    (P.T.A.B. Oct. 27, 2015).
    In its final written decision, the Board held that CFAD
    had shown by a preponderance of the evidence that claims
    1–10 of the ’501 patent are unpatentable as obvious over
    the combination of Powell, Mitchell, and Dishman.
    Coalition for Affordable Drugs VI LLC v. Celgene Corp., No.
    IPR2015-01092, Paper 73, at 33 (P.T.A.B. Oct. 26, 2016)
    (“’501 Final Written Decision”).          The Board denied
    Celgene’s request for rehearing.
    C
    In the interim, Celgene “overhaul[ed]” its Original
    S.T.E.P.S. program to create what it called an “Enhanced
    S.T.E.P.S.” program. Appeal No. 18-1167, Appellant’s Br.
    1     R.J. Powell & J.M.M. Gardner-Medwin, Guideline
    for the Clinical Use and Dispensing of Thalidomide, 70
    Postgrad Med. J. 901–904 (1994) (Appeal No. 18-1171, J.A.
    324–25).
    2    Allen A. Mitchell et al., A Pregnancy-Prevention
    Program in Women of Childbearing Age Receiving
    Isotretinoin, 333:
    2 New Eng. J. Med. 101
    –06 (July 13, 1995)
    (Appeal No. 18-1171, J.A. 328–33).
    3    Benjamin R. Dishman et al., Pharmacists’ Role in
    Clozapine Therapy at a Veterans Affairs Medical Center, 51
    Am. J. Hosp. Pharm. 899–901 (Apr. 1, 1994) (Appeal No.
    18-1171, J.A. 334–36).
    6                             CELGENE CORPORATION v. PETER
    8–9. According to Celgene, the ’720 patent is directed to its
    Enhanced S.T.E.P.S. program. See 
    id. at 10
    .
    Celgene’s ’720 patent relates to “[i]mproved methods
    for delivering to a patient in need of the drug, while
    avoiding the occurrence of an adverse side effect known or
    suspected of being caused by the drug.” ’720 patent at
    Abstract. Claim 1, written in Jepson format, states:
    1. In a method for delivering a drug to a patient in
    need of the drug, while avoiding the occurrence of
    an adverse side effect known or suspected of being
    caused by said drug, wherein said method is of the
    type in which prescriptions for said drug are filled
    only after a computer readable storage medium has
    been consulted to assure that the prescriber is
    registered in said medium and qualified to
    prescribe said drug, that the pharmacy is
    registered in said medium and qualified to fill the
    prescription for said drug, and the patient is
    registered in said medium and approved to receive
    said drug, the improvement comprising:
    a. defining a plurality of patient risk groups
    based upon a predefined set of risk parameters
    for said drug;
    b. defining a set of information to be obtained
    from said patient, which information is
    probative of the risk that said adverse side
    effect is likely to occur if said drug is taken by
    said patient;
    c. in response to said information set, assigning
    said patient to at least one of said risk groups
    and entering said risk group assignment in
    said medium;
    d. based upon said information and said risk
    group assignment, determining whether the
    CELGENE CORPORATION v. PETER                                7
    risk that said adverse side effect is likely to
    occur is acceptable; and
    e. upon a determination that said risk is
    acceptable, generating a prescription approval
    code to be retrieved by said pharmacy before
    said prescription is filled.
    CFAD filed three petitions for IPR, each challenging all
    32 claims of the ’720 patent. The Board instituted review
    of claims 1–32 in all three cases. In the first IPR, the Board
    instituted review based on obviousness over the Thalomid
    Package Insert, 4 Cunningham, 5 Zeldis, 6 and other prior
    art. Coalition for Affordable Drugs VI, LLC v. Celgene
    Corp., No. IPR2015-01096, Paper 21 (P.T.A.B. Oct. 27,
    2015). In the second IPR, the Board instituted review
    based on obviousness over Powell and Dishman, in view of
    Cunningham, and further in view of Mann 7 and other prior
    art. Coalition for Affordable Drugs VI, LLC v. Celgene
    Corp., No. IPR2015-01102, Paper 21 (P.T.A.B. Oct. 27,
    2015). In the third IPR, the Board instituted review based
    on obviousness over the same references as the second IPR
    but using Mitchell instead of Powell as the base reference.
    4   ThalomidTM (Thalidomide) Capsules Revised
    Package Insert (July 15, 1998) (Appeal No. 18-1167, J.A.
    411–32).
    5   
    U.S. Patent No. 5,832,449
     (Appeal No. 18-1167,
    J.A. 440–62).
    6   Jerome B. Zeldis et al., S.T.E.P.S.TM: A
    Comprehensive Program for Controlling and Monitoring
    Access to Thalidomide, Clinical Therapeutics® 21:2, 319–
    30 (1999) (Appeal No. 18-1167, J.A. 491–502).
    7   Thaddeus Mann & Cecelia Lutwak-Mann, Passage
    of Chemicals into Human and Animal Semen: Mechanisms
    and Significance, 11:1 CRC Critical Reviews in Toxicology
    1, 1–14 (1982) (Appeal No. 18-1167, J.A. 8237–52).
    8                            CELGENE CORPORATION v. PETER
    Coalition for Affordable Drugs VI, LLC v. Celgene Corp.,
    No. IPR2015-01103, Paper 22 (P.T.A.B. Oct. 27, 2015).
    In each of its final written decisions, the Board held
    that CFAD had shown by a preponderance of the evidence
    that claims 1–32 of the ’720 patent were unpatentable as
    obvious over the instituted ground.           Coalition for
    Affordable Drugs VI, LLC v. Celgene Corp., No. IPR2015-
    01096, Paper 73 (P.T.A.B. Oct. 26, 2016) (“-01096 Final
    Written Decision”); Coalition for Affordable Drugs VI, LLC
    v. Celgene Corp., No. IPR2015-01102, Paper 75 (P.T.A.B.
    Oct. 26, 2016) (“-01102 Final Written Decision”); Coalition
    for Affordable Drugs VI, LLC v. Celgene Corp., No.
    IPR2015-01103, Paper 76 (P.T.A.B. Oct. 26, 2016) (“-01103
    Final Written Decision”). Following Celgene’s request for
    rehearing, the Board modified its final written decisions to
    uphold the patentability of claim 10 because CFAD failed
    to prove that claim obvious by a preponderance of the
    evidence.
    D
    Celgene timely appealed all four IPRs.           We
    consolidated the appeals from the three IPRs on the ’720
    patent (Appeal Nos. 18-1167, 18-1168, 18-1169) and
    designated the appeal from the IPR on the ’501 patent
    (Appeal No. 18-1171) as a companion case. CFAD did not
    participate in these appeals. The Director of the United
    States Patent and Trademark Office (“PTO”) intervened
    pursuant to 
    35 U.S.C. § 143
    .
    We have jurisdiction over these appeals pursuant to
    
    28 U.S.C. § 1295
    (a)(4)(A).
    II
    On appeal, Celgene argues that the Board erred in
    finding all claims of the ’501 patent and claims 1–9 and 11–
    32 of the ’720 patent obvious. Celgene also argues that the
    retroactive application of IPRs to patents filed before
    September 16, 2012, when the relevant provisions of the
    CELGENE CORPORATION v. PETER                              9
    Leahy-Smith America Invents Act went into effect (“pre-
    AIA patents”), is an unconstitutional taking. We begin by
    addressing the merits of these appeals. Then, because we
    affirm the Board’s obviousness determinations, we turn to
    the constitutional challenge.
    A
    1
    Obviousness is a question of law based on underlying
    factual determinations. Belden Inc. v. Berk-Tek LLC, 
    805 F.3d 1064
    , 1073 (Fed. Cir. 2015). We review the Board’s
    ultimate obviousness determination de novo and
    underlying factual findings for substantial evidence.
    Harmonic Inc. v. Avid Tech., Inc., 
    815 F.3d 1356
    , 1363 (Fed.
    Cir. 2016). Substantial evidence is “more than a mere
    scintilla” and means “‘such relevant evidence as a
    reasonable mind might accept as adequate to support a
    conclusion.’” Biestek v. Berryhill, 
    139 S. Ct. 1148
    , 1154
    (2019) (quoting Consol. Edison Co. v. NLRB, 
    305 U.S. 197
    ,
    229 (1938)).
    We review the Board’s determination of the broadest
    reasonable interpretation of the claim language de novo.
    Straight Path IP Grp., Inc. v. Sipnet EU S.R.O., 
    806 F.3d 1356
    , 1360 (Fed. Cir. 2015). 8
    8    We note that the PTO has since changed the claim
    construction standard used in IPR proceedings. See 
    37 C.F.R. § 42.100
    (b); Changes to the Claim Construction
    Standard for Interpreting Claims in Trial Proceedings
    Before the Patent Trial and Appeal Board, 
    83 Fed. Reg. 51,340
     (Oct. 11, 2018) (to be codified at 37 C.F.R. pt. 42).
    The new standard applies only to petitions filed on or after
    November 13, 2018, and therefore does not impact these
    cases. In these IPRs, the claims were to be construed using
    the broadest reasonable interpretation in light of the
    10                            CELGENE CORPORATION v. PETER
    2
    We begin with the ’501 patent. Celgene seeks reversal,
    or at least vacatur and remand, of the Board’s
    determination that CFAD established by a preponderance
    of the evidence that claims 1–10 would have been obvious
    over the combination of Powell, Mitchell, and Dishman.
    The Board relied on Powell’s teachings of the clinical use
    and dispensing of thalidomide; Mitchell’s description of a
    pregnancy-prevention program for women users of
    Accutane, another teratogenic drug; and Dishman’s
    disclosure of a registry for pharmacies, prescribers, and
    users of clozapine, an anti-psychotic drug with serious
    potential side effects. ’501 Final Written Decision at 13.
    The Board determined that a person of ordinary skill in the
    art would have been motivated to combine Powell,
    Mitchell, and Dishman “to address the problem of limiting
    thalidomide access to patients likely to suffer serious
    adverse side effects, including birth defects in a developing
    fetus.” 
    Id. at 24
    .
    On appeal, Celgene challenges three aspects of the
    Board’s obviousness determination: (1) its finding that the
    prior art satisfies the “computer readable storage medium,”
    limitation, which rises and falls with a claim construction
    argument; (2) its finding that it would have been obvious
    to counsel male patients about the risks of teratogenic
    drugs; and (3) its findings on secondary considerations. We
    address each in turn.
    a
    Before the Board, Celgene argued that the term
    “computer readable storage medium” in claim 1 requires a
    centralized computer readable storage medium, namely “a
    centralized database that includes all registration
    specification. Cuozzo Speed Techs., LLC v. Lee, 
    136 S. Ct. 2131
    , 2146 (2016).
    CELGENE CORPORATION v. PETER                                11
    information      regarding      the   claimed     prescribers,
    pharmacies, and patients.” ’501 Final Written Decision at
    9–10.     The Board considered Celgene’s proffered
    construction and rejected its argument that the computer
    readable storage medium of claim 1 must be centralized.
    
    Id.
     at 10–11. First, the Board noted that the term
    “centralized” does not appear in claim 1. 
    Id. at 10
    . In
    addition, the Board found that the specification does not
    require that all registration information be centralized in
    one database. 
    Id.
     (“‘The computer readable storage
    medium in which the pharmacies are registered may be the
    same as, or different from the computer readable storage
    medium in which the prescribers are registered.’” (quoting
    ’501 patent col. 4 ll. 54–57)). Finally, the Board considered
    and rejected Celgene’s prosecution history and extrinsic
    evidence arguments. See 
    id.
     at 10–11.
    On appeal, Celgene again argues that the claims
    require a centralized computer readable storage medium.
    Appeal No. 18-1171, Appellant’s Br. 31–36. According to
    Celgene, the claims’ use of the term “said medium”
    referring back to “a computer readable storage medium”
    indicates that it must be a single, centralized computer
    readable storage medium. 
    Id. at 32
    . But, as the PTO
    points out, the use of “a” or “an” in an open-ended
    “comprising” claim connotes “one or more.” Appeal No. 18-
    1171, Intervenor’s Br. 26–27; Baldwin Graphic Sys., Inc. v.
    Siebert, Inc., 
    512 F.3d 1338
    , 1342 (Fed. Cir. 2008). And
    “[t]he subsequent use of definite articles ‘the’ or ‘said’ in a
    claim to refer back to the same claim term does not change
    the general plural rule, but simply reinvokes that non-
    singular meaning.” Baldwin, 
    512 F.3d at 1342
    . Exceptions
    to the general rule that “a” or “an” means more than one
    arise only when “the language of the claims themselves, the
    specification, or the prosecution history necessitate a
    departure from the rule.” See 
    id.
     at 1342–43.
    Neither the claims themselves, the specification, nor
    the prosecution history necessitate such a departure.
    12                            CELGENE CORPORATION v. PETER
    See ’501 Final Written Decision at 10–11. The claims recite
    “a computer readable storage medium” and do not specify
    that it is centralized. The specification does not require
    that the computer readable storage medium be centralized.
    In fact, the specification envisions that there may be
    multiple, distinct computer readable storage media, i.e.,
    separate media for prescribers, pharmacies, and patients.
    See ’501 patent at col. 4 ll. 54–57, col. 10 ll. 13–17.
    Further, we are not persuaded by Celgene’s argument
    that the prosecution history disclaimed a non-centralized
    computer readable storage medium. See Appeal No. 18-
    1171, Appellant’s Br. 33–34. We agree with the PTO that
    the better reading of the prosecution history is that
    Celgene distinguished the claimed invention from the prior
    art on the basis that the invention uses a computer
    readable storage medium while the prior art used the
    Internet. See Appeal No. 18-1171, Intervenor’s Br. 31–33.
    Finally, because the intrinsic evidence does not require
    a centralized computer readable storage medium, the
    Board was correct to not allow the extrinsic evidence,
    including expert testimony, to “trump the persuasive
    intrinsic evidence in this case.” ’501 Final Written Decision
    at 10. Under the broadest reasonable interpretation, the
    Board was therefore correct in determining that claim 1
    was not limited to a centralized computer readable storage
    medium.
    Based on the Board’s finding that the computer
    readable storage medium recited in claim 1 need not be
    centralized,   the    Board   found    that    Dishman’s
    “computerized lockout system” satisfied the claim
    limitation. 
    Id.
     at 18–20. Celgene concedes that Dishman
    teaches a decentralized storage medium and does not
    dispute that Dishman satisfies this limitation under the
    Board’s construction. See Appeal No. 18-1171, Appellant’s
    Br. 37. Because Celgene’s challenge relies entirely on its
    CELGENE CORPORATION v. PETER                             13
    proposed claim construction and we affirm the Board’s
    construction, Celgene’s challenge must fail. 9
    For these reasons, Celgene’s arguments on the
    “computer readable storage medium” limitation are
    unpersuasive and are not grounds for reversal or vacatur
    and remand.
    b
    Claim 1 of the ’501 patent requires providing “male
    patients who are capable of impregnating females” with
    “counseling information concerning the risks attendant to
    fetal exposure to said drug.”         Celgene argues that
    counseling male patients about the risks of fetal exposure
    to the drug upon or after fertilization would not have been
    obvious. Appeal No. 18-1171, Appellant’s Br. 25–31.
    In finding this limitation obvious, the Board relied on
    CFAD’s expert Dr. Jeffrey Fudin’s opinion that at the time
    of the alleged invention, “the sperm of male patients could
    be damaged by teratogenic drugs and consequently result
    in birth defects, if the male was to impregnate a female.”
    ’501 Final Written Decision at 15–16. For support, Dr.
    Fudin relied on the Mann study, which showed that
    thalidomide had negative effects on the sperm of male
    rabbits and the fetuses resulting from mating with female
    rabbits. See 
    id.
     at 15–17.
    The Board evaluated Dr. Fudin’s opinion and the
    supporting Mann study and credited his testimony that a
    person of ordinary skill in the art would have “understood
    9    Even under Celgene’s claim construction, the
    Board determined that its ultimate determination on
    obviousness would not change. ’501 Final Written Decision
    at 11, 20. Specifically, the Board held, in the alternative,
    that using a centralized database would have been obvious.
    See id. at 20.
    14                            CELGENE CORPORATION v. PETER
    the necessity of counseling males, capable of impregnating
    females, about the risks that attend fetal exposure to a
    teratogenic drug.” Id. at 16–17. The Board acknowledged
    that Powell stated that “[n]o effects on male sperm are
    recognized,” but found that statement alone insufficient to
    defeat Dr. Fudin’s testimony that an ordinarily skilled
    artisan would have recognized that sperm of male patients
    treated with teratogenic drugs could lead to birth defects
    in fetuses. Id. at 17.
    On appeal, Celgene primarily disputes the Board’s
    reading of Powell, specifically the statement that “[n]o
    effects on male sperm are recognized.” See Appeal No. 18-
    1171, Appellant’s Br. 26–29. The Board found that, when
    read in context, this statement in Powell refers to the
    contraceptive effects thalidomide has on male sperm, not
    the teratogenic effects thalidomide has on male sperm. See
    ’501 Final Written Decision at 17. Celgene argues that
    “[n]o reasonable fact finder could possibly read” this
    sentence in Powell “as referring to the contraceptive effects
    of thalidomide.” Appeal No. 18-1171, Appellant’s Br. 27.
    But, the Board’s decision on this limitation relied on Dr.
    Fudin’s opinion, supported by Mann, as described above.
    Celgene’s main challenge to Dr. Fudin’s opinion and his
    reliance on Mann was that the Mann study was conducted
    on male rabbits rather than human men. Appeal No. 18-
    1171, Appellant’s Br. 30–31, Reply Br. 7–8. The Board
    considered and rejected this argument. See ’501 Final
    Written Decision at 17 (noting that Celgene previously
    admitted that studies related to rabbit sperm were
    relevant to evaluating the effects of thalidomide on human
    sperm).      Substantial evidence supports the Board’s
    ultimate determination, based on Dr. Fudin’s opinion as
    supported by Mann, that it would have been obvious in
    light of the prior art to counsel male patients about the
    risks of fetal exposure to the drug.
    CELGENE CORPORATION v. PETER                              15
    c
    Finally, Celgene challenges the Board’s determination
    that Celgene’s evidence of objective indicia of non-
    obviousness was unpersuasive. The Board considered and
    weighed Celgene’s evidence of long-felt but unmet need,
    industry praise, and unexpected results. Substantial
    evidence supports the Board’s conclusions on each of these
    secondary considerations and its conclusion that they do
    not outweigh the showing of obviousness.
    The Board found that Celgene failed to establish a
    long-felt but unsolved need because it did not show that the
    prior art methods of controlling the distribution of
    hazardous drugs—including Mitchell and Dishman—were
    insufficient to meet any need to control distribution of
    thalidomide. ’501 Final Written Decision at 28. The Board
    acknowledged Celgene’s evidence of industry praise and
    gave it weight. See id. The Board also considered Celgene’s
    evidence of unexpected results but ultimately gave it “little
    weight” because the Board was not persuaded that the
    results obtained by combining the features of the prior art
    drug distribution programs to control distribution of
    thalidomide would have been truly unexpected. See id. at
    28–29. The Board concluded that the evidence of secondary
    considerations did not outweigh the strong showing of
    obviousness. See id. at 29.
    On appeal, Celgene challenges the Board’s findings on
    unexpected results and long-felt need. Appeal No. 18-1171,
    Appellant’s Br. 38–41, Reply Br. 16–23. On unexpected
    results, Celgene faults the Board’s decision to give its
    evidence “little weight” and argues that it should have been
    given “significant, if not dispositive weight.” Appeal No.
    18-1171, Appellant’s Br. 39–40. However, substantial
    evidence supports the Board’s assessment and weighing of
    this evidence, and we decline to reweigh the evidence on
    appeal. See In re NTP, Inc., 
    654 F.3d 1279
    , 1292 (Fed. Cir.
    2011) (“This court does not reweigh evidence on appeal, but
    16                            CELGENE CORPORATION v. PETER
    rather determines whether substantial evidence supports
    the Board’s fact findings.”); Regents of the Univ. of Cal. v.
    Broad Inst., Inc., 
    903 F.3d 1286
    , 1294 (Fed. Cir. 2018) (“We
    do not reweigh the evidence. It is not our role to ask
    whether substantial evidence supports fact-findings not
    made by the Board, but instead whether such evidence
    supports the findings that were in fact made.”).
    On long-felt need, Celgene identifies what it contends
    is an “inconsisten[cy]” between the Board’s determination
    in this IPR on the ’501 patent and the IPRs on the ’720
    patent. Appeal No. 18-1171, Reply Br. 22–23. In this case,
    the Board found no long-felt but unmet need for a better
    system to distribute potentially hazardous drugs like
    thalidomide in part because existing systems were
    available and adequate. ’501 Final Written Decision at 28.
    As explained below, in the IPRs on the ’720 patent, the
    Board found that there was a motivation to improve
    existing distribution systems for potentially hazardous
    drugs because of the severity of the possible adverse effects.
    See, e.g., -01096 Final Written Decision at 22–23.
    Contrary to Celgene’s assertion, this tension is not
    irreconcilable. The fact that there is no long-felt, unmet
    need does not necessarily mean that there is no motivation
    to improve a system. See Spectrum Pharm., Inc. v. Sandoz
    Inc., 
    802 F.3d 1326
    , 1336 (Fed. Cir. 2015) (upholding
    district court’s finding that “despite the motivation . . .
    there was not a long-felt but unmet need”). In fact, Celgene
    stated that it was “committed to making the S.T.E.P.S.
    program succeed and will make any modifications to the
    program that are necessary to ensure its effectiveness.”
    See Appeal No. 18-1167, J.A. 501. Especially in this
    context involving safety, we see no conflict between finding
    a motivation to improve the safety of existing systems even
    though the existing systems were mostly successful. We
    conclude that substantial evidence supports the Board’s
    assessment of Celgene’s evidence of long-felt, unresolved
    need.
    CELGENE CORPORATION v. PETER                             17
    Finally, we see no error in the Board’s ultimate
    determination of obviousness. Before concluding that the
    claims would have been obvious, the Board weighed the
    “strong showing of obviousness” against the “appropriate
    weight” given to evidence of industry praise and the “little
    weight” given to evidence of unexpected results. ’501 Final
    Written Decision at 28–29.
    We therefore affirm the Board’s holding that claims 1–
    10 of the ’501 patent are unpatentable as obvious over the
    asserted prior art.
    3
    Turning to the ’720 patent, Celgene seeks reversal, or
    at least vacatur and remand, of the Board’s determinations
    that CFAD established by a preponderance of the evidence
    that claims 1–9 and 11–32 would have been obvious over
    the prior art. The Board’s analysis relevant to this appeal
    was nearly identical across all three proceedings. See -
    01096 Final Written Decision at 15–26; -01102 Final
    Written Decision at 16–27; -01103 Final Written Decision
    at 16–27; see also Appeal No. 18-1167, Appellant’s Br. 27,
    Intervenor’s Br. 26.
    On motivation, the Board determined that a person of
    ordinary skill in the art would have been motivated to
    improve the existing distribution methods of potentially
    hazardous drugs because “where significant safety risks
    exist with a drug, one would continuously search for safer
    ways to control the distribution of the drug.” -01096 Final
    Written Decision at 22–23; -01102 Final Written Decision
    at 24–25; -01103 Final Written Decision at 24–25.
    The Board construed the claim term “prescription
    approval code” and adopted Celgene’s proposed
    construction: “[A] code representing that an affirmative
    risk assessment has been made based upon risk-group
    assignment and the information collected from the patient,
    and that is generated only upon a determination that the
    18                            CELGENE CORPORATION v. PETER
    risk of a side effect occurring is acceptable.” -01096 Final
    Written Decision at 12–13; -01102 Final Written Decision
    at 13; -01103 Final Written Decision at 13.
    The Board then considered whether the prior art
    taught the following disputed limitation: “upon a
    determination that said risk is acceptable, generating a
    prescription approval code to be retrieved by said
    pharmacy before said prescription is filled.” The Board
    determined that it would have been obvious to a person of
    ordinary skill in the art because they would have
    appreciated that Cunningham’s approval code, used to
    track and manage trial pharmaceutical products, could
    likewise be used by prescribers and pharmacies to track
    and manage prescription pharmaceutical products. -01096
    Final Written Decision at 24; -01102 Final Written Decision
    at 26; -01103 Final Written Decision at 26. The Board
    concluded that:
    We further hold that the claimed improvement
    recited in the challenged claims represents a
    combination of known prior art elements
    (identifying patient risk groups, collecting patient
    information relating to the risk, determining
    whether the risk is acceptable, and controlling
    dispensation of the drug using both a prescription
    and an approval code) for their known purpose
    (control distribution of drug) to achieve a
    predictable result (avoid giving patients drugs that
    have an unacceptable risk of side effects).
    -01096 Final Written Decision at 24–25; -01102 Final
    Written Decision at 26; -01103 Final Written Decision at 26.
    On appeal, Celgene challenges two aspects of the
    Board’s obviousness determination: (1) its finding that
    there was a motivation to improve the existing distribution
    methods of potentially hazardous drugs; and (2) its finding
    that a person of skill in the art would have been motivated
    to develop the claimed invention. We address each below.
    CELGENE CORPORATION v. PETER                             19
    a
    Celgene first argues that there was no motivation to
    improve the existing method for avoiding birth defects from
    exposure to thalidomide (the Original S.T.E.P.S. program)
    because it was working so well that there had been no
    reports of birth defects or even potential fetal exposure to
    thalidomide using that system. Appeal No. 18-1167,
    Appellant’s Br. 32–33, 35–37. Celgene contends that
    because there were no problems with the Original
    S.T.E.P.S. program, a person skilled in the art would not
    have been motivated to improve it. See 
    id.
     Celgene
    essentially argues that there was no motivation because,
    “[i]f it ain’t broke, don’t fix it.” 
    Id. at 33
    .
    The Board considered and rejected this argument,
    finding that there was a motivation because there are
    serious concerns with distributing a drug, like thalidomide,
    that is known to cause severe adverse side effects. -01096
    Final Written Decision at 22–23; -01102 Final Written
    Decision at 24–25; -01103 Final Written Decision at 24–25
    (“[W]here significant safety risks exist with a drug, one
    would continuously search for safer ways to control the
    distribution of the drug. Put simply, where significant
    safety concerns exist[], one of ordinary skill in the art
    would not wait until an accident occurred to seek out
    improvements.”).
    The Board’s motivation determination is supported by
    substantial evidence. For example, in Zeldis, Celgene
    professed its commitment to making improvements to the
    S.T.E.P.S. program.      Appeal No. 18-1167, J.A. 501
    (“Celgene is committed to making the S.T.E.P.S. program
    succeed and will make any modifications to the program
    that are necessary to ensure its effectiveness.”).
    Finally, Celgene challenges the Board’s motivation as
    too “generic.” Appeal No. 18-1167, Appellant’s Br. 35–37.
    We disagree.      The desire to decrease the risks of
    administering a drug with adverse side effects, like
    20                             CELGENE CORPORATION v. PETER
    thalidomide, is a specific motivation to improve the prior
    art. See, e.g., Tokai Corp. v. Easton Enters., Inc., 
    632 F.3d 1358
    , 1371–72 (Fed. Cir. 2011) (upholding obviousness
    determination and motivation finding based on the “need
    in the prior art for safer utility lighters”); Hologic, Inc. v.
    Minerva Surgical, Inc., 764 F. App’x 873, 880 (Fed. Cir.
    2019) (“The lack of any specific safety concerns does not
    preclude a motivation to make a device safer.”). We
    disagree with Celgene’s assertion that approving of this
    motivation “leave[s] no room for patents on improvement.”
    Appeal No. 18-1167, Appellant’s Br. 37. In a case like this,
    where safety is a concern and where the potential adverse
    side effects are so severe, the Board did not err in finding
    that the desire to improve a system that is working well
    qualifies as a valid motivation.
    b
    Celgene also argues that, even if there had been a
    general motivation to improve the prior art systems,
    “substantial evidence does not show that there was
    motivation to overhaul that program with the particular,
    prospective, doctor-interfering system claimed by the
    ’720 patent.” Appeal No. 18-1167, Appellant’s Br. 38; see
    also 
    id.
     at 38–43.
    First, Celgene faults the Board for allegedly failing to
    explain “how the prior art renders obvious the claims’
    required affirmative risk assessment.” Id. at 40. Contrary
    to Celgene’s assertions, the Board did not “ignore” its
    affirmative risk assessment argument. In fact, the Board
    incorporated the notion of affirmative risk assessment into
    its claim construction and considered it in its obviousness
    findings. See -01096 Final Written Decision at 12–15; -
    01102 Final Written Decision at 13–16; -01103 Final
    Written Decision at 13–16. The Board relied on each of the
    primary references—Thalomid Package Insert, Powell,
    and Mitchell—for the teaching of an affirmative risk
    assessment. See -01096 Final Written Decision at 17–18,
    CELGENE CORPORATION v. PETER                             21
    20 (Thalomid Package Insert); -01102 Final Written
    Decision at 17–18, 21–22 (Powell); -01103 Final Written
    Decision at 17–18, 21–22 (Mitchell). And the Board found
    that it would have been obvious to modify the methods for
    limiting distribution of drugs with adverse side effects to
    high risk groups, disclosed in Thalomid Package Insert,
    Powell, or Mitchell, to require issuance of an approval code
    prior to dispensing the drug as disclosed in Cunningham.
    See -01096 Final Written Decision at 23–25; -01102 Final
    Written Decision at 25–27; -01103 Final Written Decision
    at 25–27. Substantial evidence supports those findings.
    Next, Celgene faults the Board for not including the
    word “prospective” in its final written decisions. Appeal
    No. 18-1167, Appellant’s Br. 40. But the term “prospective”
    does not appear in claim 1 or in the Board’s construction of
    “prescription approval code.” Thus, it is neither erroneous
    nor particularly surprising that it does not appear in the
    Board’s final written decisions.
    Finally, Celgene argues that none of the prior art
    references disclose a system to “override” a doctor’s
    prescription. See, e.g., Appeal No. 18-1167, Appellant’s Br.
    40–42, Reply Br. 3–4, 6–7. However, a physician “override”
    is not required by the language of claim 1 or by the Board’s
    construction of “prescription approval code.”
    We therefore affirm the Board’s determination that
    claims 1–9 and 11–32 of the ’720 patent are unpatentable
    as obvious over the asserted prior art.
    B
    We now turn to the constitutional issue of whether the
    retroactive application of IPRs to pre-AIA patents is an
    unconstitutional taking. 10
    10  The parties’ arguments on the constitutional issue
    are almost identical in the two appeals. Therefore, in this
    22                            CELGENE CORPORATION v. PETER
    1
    We must first decide whether to reach the
    constitutional challenge even though Celgene did not raise
    it before the Board and makes the argument for the first
    time on appeal.
    “It is well-established that a party generally may not
    challenge an agency decision on a basis that was not
    presented to the agency.” In re DBC, 
    545 F.3d 1373
    , 1378
    (Fed. Cir. 2008). But we have discretion to reach issues
    raised for the first time on appeal, and in DBC we
    recognized that there are exceptions that may justify
    considering constitutional arguments not raised below. 
    Id.
    at 1379–80 (“Because we retain discretion to reach issues
    raised for the first time on appeal, we must consider
    whether this is one of those exceptional cases that
    warrants consideration of the [constitutional] issue despite
    its tardy presentation.”).
    Departing from the general rule of waiver is
    appropriate only in limited circumstances. See 
    id. at 1380
    (stating that addressing an issue not raised below is “an
    exceptional measure” appropriate only in “rare cases”); see
    also Golden Bridge Tech., Inc. v. Nokia, Inc., 
    527 F.3d 1318
    ,
    1322–23 (Fed. Cir. 2008) (stating that “deviat[ing] from
    this general rule of waiver” and “hearing new arguments
    for the first time on appeal” is disfavored “absent limited
    circumstances”). One such circumstance that can justify
    departing from the general rule of waiver is an intervening
    change in the law. See Golden Bridge, 
    527 F.3d at 1323
    .
    We also consider whether the “interest of justice” guides us
    to consider the issue despite the fact that it was not raised
    below. See 
    id.
    section, we cite only to the briefs in Appeal No. 18-1167
    unless otherwise noted.
    CELGENE CORPORATION v. PETER                               23
    The PTO concedes that we have discretion to deviate
    from our general rule of waiver and that doing so here to
    resolve the constitutional issue presented may be in the
    interest of justice. As the PTO recognized, “[g]iven the
    growing number of retroactivity challenges apparently
    prompted by the reference to retroactivity in Oil States,
    however, this Court may nevertheless conclude that the
    interests of justice warrant addressing the retroactivity
    question quickly to avert further uncertainty regarding the
    constitutionality of inter partes review.” Intervenor’s Br.
    37 (footnote omitted).
    We have indeed seen a growing number of retroactivity
    challenges following the Supreme Court’s decision in Oil
    States, including several that are currently pending before
    this court. The Supreme Court left open this challenge
    with the following passage near the end of its decision in
    Oil States:
    Moreover, we address only the precise
    constitutional challenges that Oil States raised
    here. Oil States does not challenge the retroactive
    application of inter partes review, even though that
    procedure was not in place when its patent issued.
    Nor has Oil States raised a due process challenge.
    Finally, our decision should not be misconstrued as
    suggesting that patents are not property for
    purposes of the Due Process Clause or the Takings
    Clause.
    Oil States Energy Servs., LLC v. Greene’s Energy Grp.,
    LLC, 
    138 S. Ct. 1365
    , 1379 (2018). While Celgene’s
    constitutional challenge does not rely on a change in the
    law articulated in Oil States, it raises an issue not directly
    resolved by Oil States. Oil States was decided on April 24,
    2018, well after the Board’s October 26, 2016 final written
    decisions in the IPRs involved in this appeal, which at least
    partially explains why Celgene did not raise the argument
    before the Board.
    24                            CELGENE CORPORATION v. PETER
    Even if Celgene had raised its constitutional challenge
    before the Board, it is unclear how the Board could have
    corrected the alleged constitutional defect as it could have
    in DBC. See DBC, 
    545 F.3d at 1379
     (“If DBC had timely
    raised this issue before the Board, the Board could have
    evaluated and corrected the alleged constitutional
    infirmity by providing DBC with a panel of administrative
    patent judges appointed by the Secretary.”). 11
    Moreover, the constitutional challenge presented here
    is purely a question of law, so addressing it would not
    require us “to make factual findings” for the first time on
    appeal. See Golden Bridge, 
    527 F.3d at 1323
    .
    Finally, the briefing on the constitutional issue in this
    case is sufficiently thorough for our review. See Appellant’s
    Br. 44–52; Intervenor’s Br. 35–44; Reply Br. 20–28. This
    case stands in sharp contrast with Trading Technologies
    International, Inc. v. IBG LLC, 
    921 F.3d 1378
    , 1385 (Fed.
    Cir. 2019), where we declined to consider a number of
    11  The Supreme Court has “stated that ‘adjudication
    of the constitutionality of congressional enactments has
    generally been thought beyond the jurisdiction of
    administrative agencies.’” Elgin v. Dep’t of Treasury,
    
    567 U.S. 1
    , 16 (2012) (quoting Thunder Basin Coal Co. v.
    Reich, 
    510 U.S. 200
    , 215 (1994)). When asked at oral
    argument if the Board had authority to adjudicate a
    constitutional challenge to the AIA, the PTO responded
    that if the Board determined that the retroactive
    application of IPRs to pre-AIA patents was an
    unconstitutional taking, the Board could exercise its
    discretion to decline to institute the IPR. See Oral
    Argument at 36:52–37:57, Celgene Corp. v. Peter (No. 2018-
    1167),         http://www.cafc.uscourts.gov/oral-argument-
    recordings. That decision, however, would be unreviewable
    but for the possibility of mandamus. See Cuozzo, 136 S. Ct.
    at 2142.
    CELGENE CORPORATION v. PETER                               25
    constitutional challenges to IPRs included in “a total of four
    sentences” in the appellant’s opening brief. Id. (“Such a
    conclusory assertion with no analysis is insufficient to
    preserve the issue for appeal.”).         Here, a single
    constitutional issue received thorough briefing from the
    parties and was addressed extensively at oral argument.
    See Oral Argument at 5:06–21:50, 50:22–52:56 (Celgene),
    36:27–48:47 (Director), Celgene Corp. v. Peter (No. 2018-
    1167),         http://www.cafc.uscourts.gov/oral-argument-
    recordings. 12
    We therefore conclude that this is one of those
    exceptional circumstances in which our discretion is
    appropriately exercised to hear Celgene’s constitutional
    challenge even though it was not raised below.
    12  As to the suggestion that we wait until a case
    reaches us where the retroactivity challenge was raised
    below and decided by the Board, the first such case
    identified is Agarwal v. TopGolf International, Inc., No. 18-
    2270. In TopGolf, the Board allowed additional briefing on
    the constitutional issues left open by Oil States. In a single
    sentence of analysis, the Board determined that the
    retroactive application of IPRs was not unconstitutional,
    reasoning that “the patent at issue here was subject to ex
    parte reexamination, and, therefore, the United States
    Patent and Trademark Office has always had the ability to
    look at the patentability of an issued United States
    Patent.” TopGolf Int’l, Inc. v. Amit Agarwal, No. IPR2017-
    00928, Paper 40, at 80 (P.T.A.B. June 13, 2018). On
    appeal, Mr. Agarwal’s constitutional challenge to the
    retroactive application of IPRs to pre-AIA patents is one
    page of his opening brief. Brief for Appellant at 69–70,
    Agarwal v. TopGolf Int’l, Inc. (No. 18-2270). The reply brief
    is due on November 12, 2019, and the case will likely not
    be argued for at least several months thereafter.
    26                            CELGENE CORPORATION v. PETER
    2
    We now turn to the merits of Celgene’s constitutional
    challenge that the retroactive application of IPRs to pre-
    AIA patents is an unconstitutional taking.
    The Takings Clause of the Fifth Amendment states
    that private property shall not “be taken for public use,
    without just compensation.” U.S. Const. amend. V. The
    PTO does not dispute that a valid patent is private
    property for the purposes of the Takings Clause. See
    Intervenor’s Br. 43 (“A patent holder has a property
    interest in a valid patent . . . .”); Oral Argument at 41:06–
    41:22, Celgene Corp. v. Peter (No. 2018-1167),
    http://www.cafc.uscourts.gov/oral-argument-recordings.
    (“We don’t dispute that a valid patent is property for
    purposes of the Takings Clause.”).
    Celgene argues that the retroactive application of IPRs
    to their pre-AIA patents without just compensation is an
    unconstitutional taking under the Fifth Amendment.
    Appellant’s Br. 44–52. Specifically, Celgene advances a
    regulatory takings theory and argues that subjecting its
    pre-AIA patents to IPR, a procedure that did not exist at
    the time its patents issued, unfairly interferes with its
    reasonable investment-backed expectations without just
    compensation. Id. at 44–45, 49–51.
    The PTO responds on two fronts. First, the PTO argues
    that when the Board finds claims unpatentable in an IPR,
    it does not effectuate a taking under the Fifth Amendment
    because the patent owner “never had a valid property right
    because the patent was erroneously issued in the first
    instance.” Intervenor’s Br. 38; see also id. at 38–41.
    Second, the PTO argues that Celgene’s takings claim fails
    “because patents have been subject to reconsideration and
    cancellation by the USPTO in administrative proceedings
    for nearly four decades, and Celgene’s own patent[s were]
    issued subject to this administrative revocation authority.”
    Id. at 42; see also id. at 42–44. The PTO does not expressly
    CELGENE CORPORATION v. PETER                            27
    engage     Celgene’s    reasonable      investment-backed
    expectations argument. But the PTO does respond that
    “the AIA did not alter patent holders’ substantive rights.”
    See id. at 43. Rather, the PTO maintains that the AIA
    “merely revised the procedures by which [the] USPTO
    conducts these administrative proceedings” and that the
    procedural differences do not effect a Fifth Amendment
    taking. See id.
    In determining whether the retroactive application of
    IPRs to pre-AIA patents is an unconstitutional taking, we
    consider the effect that doing so has on the patent right
    granted by the PTO, and specifically whether IPRs differ
    from the pre-AIA review mechanisms significantly enough,
    substantively or procedurally, to effectuate a taking. We
    conclude that they do not. On this basis, we reject
    Celgene’s challenge even apart from the rationales of our
    prior decisions—which we also think control the outcome
    here, but which Celgene asks us to reconsider—that
    rejected    constitutional  challenges     to   retroactive
    application of the pre-AIA ex parte reexamination
    mechanism. 13
    13   In Patlex Corp. v. Mossinghoff, 
    758 F.2d 594
     (Fed.
    Cir. 1985), we faced a challenge to the retroactive
    application of ex parte reexaminations and held that it did
    not violate the due process clause of the Fifth Amendment,
    the jury trial guarantee of the Seventh Amendment, or
    Article III. 
    Id. at 603, 605
    . Our retroactivity analysis in
    Patlex relied in part on the “curative” nature of
    reexaminations and that “[c]urative statutes have received
    relatively favored treatment from the courts even when
    applied retroactively.” 
    Id. at 603
    .
    We later considered a challenge to the retroactive
    application of ex parte reexaminations based on the
    Takings Clause in Joy Technologies, Inc. v. Manbeck, 
    959 F.2d 226
     (Fed. Cir. 1992), superseded by statute on other
    28                           CELGENE CORPORATION v. PETER
    The validity of patents has always been subject to
    challenge in district court. And for the last forty years,
    patents have also been subject to reconsideration and
    possible cancellation by the PTO. As explained below, IPRs
    do not differ significantly enough from preexisting PTO
    mechanisms for reevaluating the validity of issued patents
    to constitute a Fifth Amendment taking.
    By the time Celgene filed the application that became
    the ’501 patent (1998) and the patent was issued (2000),
    and by the time Celgene filed the application that became
    the ’720 patent (2000) and the patent was issued (2001), ex
    parte reexamination had existed for roughly two decades.
    Ex parte reexamination, created by Congress in 1980 and
    still available today, allows “[a]ny person at any time” to
    “file a request for reexamination.” 
    35 U.S.C. § 302
    . The
    PTO determines whether the request raises “a substantial
    new question of patentability affecting any claim of the
    patent.” 
    Id.
     § 303(a). If it does, the reexamination is
    “conducted according to the procedures established for
    initial examination,” and the patent owner has the
    opportunity to amend claims.           Id. § 305.      The
    reexamination results in the confirmation of claims found
    grounds. Applying our reasoning in Patlex, we rejected the
    patent owner’s argument that ex parte reexamination and
    subsequent cancellation of some claims of its patent
    constituted a taking even though no PTO reexamination
    mechanisms existed when its patent issued. See id. at 228–
    29.
    The patent owners in Patlex and Joy Technologies had
    a stronger argument than Celgene does here because,
    before the creation of ex parte reexaminations, there were
    no PTO reexamination procedures. In contrast, pre-AIA
    patent owners, including Celgene, have known for almost
    forty years that their patents were issued subject to
    substantively similar forms of PTO reexamination.
    CELGENE CORPORATION v. PETER                             29
    to be patentable and the cancellation of claims found to be
    unpatentable. Id. § 307(a).
    Inter partes reexamination, created by Congress in
    1999, was also available when Celgene filed the
    ’720 patent, although not when it filed the ’501 patent. A
    third party could request inter partes reexamination, and
    the standard to initiate the reexamination was whether the
    request raised a “substantial new question of
    patentability.” 
    35 U.S.C. §§ 311
    –12 (1999) (amended).
    Inter partes reexamination “granted third parties greater
    opportunities to participate in the Patent Office’s
    reexamination proceedings,” and, following amendments
    in 2002, also allowed third parties to participate in any
    appeal of the PTO’s final reexamination decision.
    See Cuozzo Speed Techs., LLC v. Lee, 
    136 S. Ct. 2131
    , 2137
    (2016).
    Celgene’s pre-AIA patents were therefore granted
    subject to existing judicial and administrative avenues for
    reconsidering their validity. Not only were they subject to
    challenge in district court, “[f]or several decades, the
    Patent Office has also possessed the authority to
    reexamine—and perhaps cancel—a patent claim that it
    had previously allowed.” 
    Id.
    IPRs are the most recent legislative modification to the
    PTO’s longstanding reconsideration procedures. 14 In 2011,
    as part of the AIA, Congress created IPRs, which replaced
    inter partes reexamination. Leahy–Smith America Invents
    Act, Pub. L. No. 112-29, § 6, 
    125 Stat. 284
    , 299–313 (2011)
    (codified as amended at 
    35 U.S.C. §§ 311
    –19 (2012)). IPRs
    allow a third party to request that the PTO “reexamine the
    claims in an already-issued patent and to cancel any claim
    14    Celgene’s suggestion that PTO reconsideration “is
    a creation of the 2011 AIA legislation” or only available
    “[s]ince the AIA” is incorrect. See Appellant’s Br. 46.
    30                             CELGENE CORPORATION v. PETER
    that the agency finds to be unpatentable in light of [the]
    prior art” specified in 
    35 U.S.C. § 311
    (b). Cuozzo, 136 S. Ct.
    at 2136.
    In this case it suffices for us to decide that IPRs do not
    differ sufficiently from the PTO reconsideration avenues
    available when the patents here were issued to constitute
    a Fifth Amendment taking. Celgene identifies a number of
    differences between reexaminations and IPRs, including
    that IPRs are adjudicative and have discovery, briefing,
    and an oral hearing, Appellant’s Br. 47, but as explained
    below, these differences are not sufficiently substantive or
    significant to constitute a taking.
    Unsurprisingly, Celgene does not grapple with the far
    more significant similarities between IPRs and their
    reexamination predecessors.        In IPRs, patents are
    reviewed on the same substantive grounds—anticipation
    and obviousness, based on the same categories of prior
    art—as ex parte and inter partes reexaminations. 15 IPRs
    and reexaminations use the same preponderance of the
    evidence standard of proof. See 
    35 U.S.C. § 316
    (e) (“In an
    inter partes review instituted under this chapter, the
    petitioner shall have the burden of proving a proposition of
    unpatentability by a preponderance of the evidence.”); In
    re Baxter Int’l, Inc., 
    678 F.3d 1357
    , 1364 (Fed. Cir. 2012)
    (“In PTO reexaminations ‘the standard of proof [is] a
    preponderance of the evidence.’” (quoting In re Swanson,
    
    540 F.3d 1368
    , 1377 (Fed. Cir. 2008)). And the same
    broadest reasonable interpretation standard for claim
    construction used in reexaminations also applied in these
    15 It is undisputed that the       Board’s grounds for
    determining unpatentability were        available under the
    reexamination procedures in place      at the time the ’501
    patent and ’720 patent issued          in 2000 and 2001,
    respectively.
    CELGENE CORPORATION v. PETER                             31
    IPRs. 16 See In re CSB-Sys. Int’l, Inc., 
    832 F.3d 1335
    , 1340
    (Fed. Cir. 2016) (“During reexamination proceedings of
    unexpired patents, however, the Board uses the ‘broadest
    reasonable interpretation consistent with the specification’
    standard, or BRI.” (quoting In re NTP, Inc., 
    654 F.3d 1268
    ,
    1274 (Fed. Cir. 2011)).
    IPRs and reexaminations are also similar in that the
    Director has discretion to initiate the proceeding. In ex
    parte reexamination, the Director determines “whether a
    substantial new question of patentability affecting any
    claim of the patent concerned is raised by the request.”
    
    35 U.S.C. § 303
    (a). In IPRs, the Director has discretion to
    institute IPR if there is “a reasonable likelihood that the
    petitioner would prevail with respect to at least 1 of the
    claims challenged in the petition.” 
    Id.
     § 314(a). In both
    proceedings, the Director’s discretionary determination is
    final and non-appealable. See id. §§ 303(c), 314(d).
    Notably, IPRs serve essentially the same purpose as
    their reexamination predecessors. As the Supreme Court
    has said:
    The [IPR] proceeding involves what used to be
    called a reexamination (and, as noted above, a
    cousin of inter partes review, ex parte
    reexamination, 
    35 U.S.C. § 302
     et seq., still bears
    that name).      The name and accompanying
    procedures suggest that the proceeding offers a
    second look at an earlier administrative grant of a
    patent. Although Congress changed the name from
    “reexamination” to “review,” nothing convinces us
    16   As noted above, the PTO has since changed the
    claim construction standard used in IPR proceedings to
    align with the standard used in district court proceedings,
    a change that is favorable to the patent owner. See supra
    note 8.
    32                            CELGENE CORPORATION v. PETER
    that, in doing so, Congress wanted to change its
    basic purposes, namely, to reexamine an earlier
    agency decision.
    Cuozzo, 136 S. Ct. at 2144; see also Oil States, 
    138 S. Ct. at 1374
     (“Inter partes review is ‘a second look at an earlier
    administrative grant of a patent.’” (quoting Cuozzo, 136 S.
    Ct. at 2144)). 17
    Moreover, the Supreme Court has described district
    court challenges, ex parte reexaminations, and IPRs as
    different forms of the same thing—reexamination. See
    Return Mail, Inc. v. United States Postal Serv., 
    139 S. Ct. 1853
    , 1860 (2019) (“In sum, in the post-AIA world, a patent
    can be reexamined either in federal court during a defense
    to an infringement action, in an ex parte reexamination by
    the Patent Office, or in the suite of three post-issuance
    review proceedings before the Patent Trial and Appeal
    Board.”). All three serve the purpose of correcting prior
    agency error of issuing patents that should not have issued
    in the first place:
    Sometimes, though, bad patents slip through.
    Maybe the invention wasn’t novel, or maybe it was
    obvious all along, and the patent owner shouldn’t
    enjoy the special privileges it has received. To
    remedy these sorts of problems, Congress has long
    permitted parties to challenge the validity of
    patent claims in federal court. More recently,
    17  The legislative history of the AIA confirms that one
    of the objectives of IPRs was to “revisit and revise” issued
    patents. See Cuozzo, 136 S. Ct. at 2140. In this way, IPRs
    serve the broader goal of improving patent quality. See
    H.R. Rep. No. 112-98, pt. 1, at 48 (2011), as reprinted in
    2011 U.S.C.C.A.N. 67, 78 (explaining objective to “improve
    patent quality and restore confidence in the presumption
    of validity that comes with issued patents”).
    CELGENE CORPORATION v. PETER                                 33
    Congress has supplemented litigation with various
    administrative remedies.
    SAS Inst., Inc. v. Iancu, 
    138 S. Ct. 1348
    , 1353 (2018)
    (citation omitted); see also Microsoft Corp. v. i4i Ltd. P’ship,
    
    564 U.S. 91
    , 96 (2011) (describing district court challenges
    as an “attempt to prove that the patent never should have
    issued in the first place”); Fresenius USA, Inc. v. Baxter
    Int’l, Inc., 
    721 F.3d 1330
    , 1338 (Fed. Cir. 2013) (stating that
    “ex parte reexamination is a curative proceeding meant to
    correct or eliminate erroneously granted patents”).
    There are undoubtedly differences between IPRs and
    their predecessors. This is not surprising given that
    Congress passed the AIA with post grant review
    procedures that were intentionally more robust and would
    provide a “more efficient system for challenging patents
    that should not have issued.” See H.R. Rep. No. 112-98, pt.
    1, at 39–40 (2011), as reprinted in 2011 U.S.C.C.A.N. 67,
    69. 18 Celgene is correct that IPRs are “adjudicatory in
    nature.” Return Mail, 
    139 S. Ct. at 1860
    . Among the
    “adjudicatory characteristics” of IPRs Celgene notes are
    discovery, briefing, and an oral hearing. See Appellant’s
    Br. 47. But these procedural differences come with the
    longstanding recognition that “‘[n]o one has a vested right
    in any given mode of procedure.’” Denver & Rio Grande W.
    R.R. Co. v. Bhd. of R.R. Trainmen, 
    387 U.S. 556
    , 563 (1967)
    (quoting Ex parte Collett, 
    337 U.S. 55
    , 71 (1949)). These
    differences do not disrupt the expectation that patent
    18   Implementing IPRs to create a more robust and
    efficient system for challenging the validity of patents is
    not unlike the PTO or Congress making the system more
    robust by, for example, increasing the budget for or number
    of examiners in the reexamination unit. While those
    changes might result in significantly more requests for
    reexamination and more claims being canceled, we doubt
    that anyone would argue that they effectuate a taking.
    34                             CELGENE CORPORATION v. PETER
    owners have had for nearly four decades—that patents are
    open to PTO reconsideration and possible cancelation if it
    is determined, on the grounds specified in § 311(b), that the
    patents should not have issued in the first place.
    Celgene also argues that statistics show that IPRs have
    caused a permanent reduction in the value of patents
    granted before the AIA. See Appellants’ Br. 48–49 (citing
    statistics); Reply Br. 26–27 (citing statistics and arguing
    that they show that “patents subjected to inter partes
    review have been clobbered in ways previously
    unimaginable”). 19 But Celgene has made no showing—nor
    could it—that claims canceled in IPRs, including its own
    claims, would have fared any better in the preexisting
    reexamination procedures.
    Recognizing that its patents were also always open to
    challenge in district court, Celgene attempts to distinguish
    IPRs from district court proceedings by arguing that while
    IPRs resemble district court proceedings in some
    respects, 20 IPRs lack the “same process or rights as civil
    19  Celgene notes that almost as many IPRs were filed
    and instituted in the first four years after they were
    created as were filed in the twelve years inter partes
    reexamination were available. Appellant’s Br. 48. This
    statistic, which merely compares the frequency that these
    procedures are utilized but does not compare ultimate
    outcomes, does not sway our analysis.
    20  That IPRs resemble district court litigation in some
    ways is in line with one of the objectives of the AIA, which
    was to provide an alternative to district court litigation.
    See H.R. Rep. No. 112-98, pt. 1, at 48 (describing IPR as a
    “quick and cost effective alternativ[e] to litigation”); S. Rep.
    No. 110-259, at 20 (2008) (describing IPR as “a quick,
    inexpensive, and reliable alternative to district court
    litigation”). The fact that IPRs may have shifted some
    CELGENE CORPORATION v. PETER                               35
    litigation.” See Appellants’ Br. 47–48; Reply Br. 26–27.
    But the differences that Celgene identifies between district
    court proceedings and IPRs only serve to demonstrate that
    IPRs are similar to reexaminations. For example, IPRs use
    a preponderance of the evidence burden of proof rather
    than the district court’s clear and convincing evidence
    burden of proof.      And IPRs, at the time of these
    proceedings, used the broadest reasonable interpretation
    for claim construction rather than the narrower standard
    from Phillips v. AWH Corp., 
    415 F.3d 1303
    , 1313 (Fed. Cir.
    2005) (en banc) used in district court. While these IPR
    standards differ from those used in district court, they were
    previously used in ex parte and inter partes reexamination
    procedures, as explained above. Celgene also notes that
    the presumption of validity that applies in district court
    proceedings, overcome only by clear and convincing
    evidence, does not apply in IPRs. Reply Br. 26–27.
    However, the presumption of validity also did not apply in
    the preexisting reexamination proceedings. See In re Etter,
    
    756 F.2d 852
    , 855–56 (Fed. Cir. 1985). Moreover, we long
    ago explained that “[w]e do not consider the section 282
    presumption [of validity] . . . to be a property right subject
    to the protection of the Constitution.” Patlex Corp. v.
    Mossinghoff, 
    758 F.2d 594
    , 605 (Fed. Cir. 1985), reh’g
    granted on other grounds, 
    771 F.2d 480
     (Fed. Cir. 1985). In
    any event, because Celgene’s patents were granted subject
    to similar reexamination standards, as discussed above,
    the differences between IPRs and district court proceedings
    that Celgene identifies do not create a constitutional issue.
    In light of the foregoing, we hold that the retroactive
    application of IPR proceedings to pre-AIA patents is not an
    unconstitutional taking under the Fifth Amendment.
    Patent owners have always had the expectation that the
    validity challenges from the district court to the PTO does
    not effectuate a taking.
    36                            CELGENE CORPORATION v. PETER
    validity of patents could be challenged in district court. For
    forty years, patent owners have also had the expectation
    that the PTO could reconsider the validity of issued patents
    on particular grounds, applying a preponderance of the
    evidence standard. Although differences exist between
    IPRs and their reexamination predecessors, those
    differences do not outweigh the similarities of purpose and
    substance and, at least for that reason, do not effectuate a
    taking of Celgene’s patents.
    III
    We have considered Celgene’s remaining arguments
    and find them unpersuasive. We affirm the Board’s
    determination that all of the claims of the ’501 patent and
    claims 1–9 and 11–32 of the ’720 patent are invalid as
    obvious.
    AFFIRMED