Otsuka Pharmaceutical Co., Lt v. Thomas Price , 869 F.3d 987 ( 2017 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued December 12, 2016            Decided August 29, 2017
    No. 16-5229
    OTSUKA PHARMACEUTICAL CO., LTD., ET AL.,
    APPELLANTS
    v.
    THOMAS PRICE, SECRETARY, U.S. DEPARTMENT OF HEALTH
    AND HUMAN SERVICES, ET AL.,
    APPELLEES
    Appeal from the United States District Court
    for the District of Columbia
    (No. 1:15-cv-01688)
    Thomas G. Saunders argued the cause for appellants.
    With him on the briefs were Seth P. Waxman and Robbie
    Manhas.
    Henry C. Whitaker, Attorney, U.S. Department of Justice,
    argued the cause for federal appellees. With him on the brief
    were Benjamin C. Mizer, Principal Deputy Assistant Attorney
    General, and Scott R. McIntosh, Attorney.
    William M. Jay argued the cause for intervenors-
    appellees Alkermes, Inc., et al. With him on the brief were
    Brian T. Burgess, Andrew Kim, Sarah K. Frederick, and
    Christopher T. Holding.
    2
    Before: BROWN and SRINIVASAN, Circuit Judges, and
    WILLIAMS, Senior Circuit Judge.
    Opinion for the Court filed by Circuit Judge SRINIVASAN.
    SRINIVASAN, Circuit Judge: The Food, Drug, and
    Cosmetic Act affords periods of “marketing exclusivity” to
    pioneering drug products. When a drug earns a period of
    exclusivity, the Food and Drug Administration must withhold
    approval of certain competing drugs if various conditions are
    satisfied. But how does the FDA determine if a new drug
    bears a sufficiently close relationship to a pioneering drug to
    fall within the latter’s zone of exclusivity? This case concerns
    the FDA’s test for making that determination.
    The two drugs at issue in this case are antipsychotics
    primarily used to treat schizophrenia and bipolar disorder.
    The first drug, manufactured by Otsuka Pharmaceutical, is
    called Abilify Maintena. The second, made by Alkermes, is
    named Aristada.
    When Alkermes sought FDA approval for Aristada,
    Otsuka opposed the application on the ground that Aristada’s
    approval would violate an ongoing period of marketing
    exclusivity enjoyed by Abilify Maintena. Otsuka emphasized
    that both drugs ultimately metabolize in the body into the
    same molecule, and that Alkermes’s application for Aristada
    relied in part on studies showing the safety and efficacy of a
    precursor product to Abilify Maintena. Otsuka argued that, in
    light of the relationship between the two drugs, approving
    Aristada would infringe on Abilify Maintena’s exclusivity.
    The FDA rejected Otsuka’s arguments and granted
    approval to Aristada. The agency relied on the fact that the
    two products have different “active moieties”—roughly,
    3
    active ingredients. A drug’s active moiety has long played a
    key role in determining its eligibility to receive marketing
    exclusivity: to be entitled to exclusivity, a drug must either
    contain a previously unapproved active moiety or use an
    approved moiety in a new way. In approving Aristada, the
    FDA staked out the position that a drug’s active moiety not
    only determines its eligibility for marketing exclusivity, but
    also defines the field of drugs subject to that exclusivity.
    Otsuka sought judicial review, contending, among other
    things, that the agency’s same-moiety limitation on the scope
    of a drug’s marketing exclusivity conflicts with the FDCA.
    The district court granted summary judgment in favor of the
    FDA and Alkermes. The court concluded that the FDA’s
    same-moiety test is a reasonable construction of the statute
    and is consistent with the agency’s regulations. We agree
    with the district court and affirm its decision.
    I.
    A.
    Before a company can make a drug available for public
    consumption, the FDA must approve a new drug application
    certifying the drug’s safety and efficacy. 21 U.S.C. § 355(a),
    (b). Until 1984, all such applications were standalone
    applications: applications for which the drug’s proponent
    either conducted, or secured a right to reference, all the
    investigations used to demonstrate the drug’s safety and
    efficacy. See 
    id. § 355(b)(1).
    As a result, a company seeking
    approval of a new drug would regularly need to reestablish
    the safety and efficacy of chemical compounds used in
    previously approved drugs.
    4
    In order to reduce the need to conduct duplicative studies,
    the Drug Price Competition and Patent Term Restoration Act
    of     1984—better       known     as   the    Hatch-Waxman
    Amendments—amended the FDCA to establish two
    streamlined pathways to FDA approval. See H.R. Rep. No.
    98-857, pt. 1, at 16-17 (1984). The first abbreviated route,
    known as an Abbreviated New Drug Application (ANDA),
    permits approval of “bioequivalent” (e.g., generic) versions of
    previously approved drugs without an independent showing
    of their safety and efficacy. 21 U.S.C. § 355(j)(2)(A).
    The second abbreviated route, directly at issue here,
    enables new drug applications for non-generic drug products
    to rely, in part or in whole, on studies that “were not
    conducted by or for the applicant and for which the applicant
    has not obtained a right of reference” to show the applied-for
    drug’s safety and efficacy. 
    Id. § 355(b)(2).
    That route,
    known as a “(b)(2) application” due to the statutory
    subsection establishing it, requires an applicant to show the
    propriety of relying on the preexisting studies to demonstrate
    the applied-for drug’s safety and efficacy.            A (b)(2)
    application must also certify that sales of the applied-for drug
    would not infringe upon active, valid patents for any
    previously approved drugs invoked in support of the
    application. 
    Id. § 355(b)(2)(A).
    The Hatch-Waxman Amendments’ abbreviated pathways
    in theory could enable competitors to “free ride” off of the
    work of innovators without having to foot the substantial
    expenses associated with safety-and-efficacy testing. As a
    result, the Amendments also introduced a regime of
    marketing exclusivity into the FDCA.
    Under that system, the statute grants a first-in-time
    innovator a period of exclusivity during which the FDA must
    5
    deny approval of second-in-time abbreviated applications
    (both ANDAs and (b)(2) applications) for drug products
    meeting certain conditions. If an applicant seeking to use an
    abbreviated pathway is blocked by a previously approved
    drug’s exclusivity, the applicant can either wait for the
    exclusivity period to expire, or instead submit a standalone,
    non-abbreviated application that does not rely on any
    previously approved drugs.
    The FDCA confers marketing exclusivity under three
    distinct provisions, the full text of which are set out in an
    appendix to this opinion. We will adhere to the parties’
    convention by referring to the three provisions as “romanette
    ii,” “romanette iii,” and “romanette iv.”          21 U.S.C.
    § 355(c)(3)(E)(ii)-(iv).
    Romanette ii, the FDCA’s broadest grant of marketing
    exclusivity, applies to what FDA regulations refer to as “New
    Chemical Entities”: drugs for which “no active ingredient
    (including any ester or salt of the active ingredient) . . . has
    been approved in any other application.”           21 U.S.C.
    § 355(c)(3)(E)(ii); 21 C.F.R. § 314.108(a). The statutory
    reference to a drug’s “active ingredient” captures the drug’s
    active moiety, which the regulations define as “the molecule
    or ion . . . responsible for the physiological or
    pharmacological action of the drug substance.” 21 C.F.R.
    § 314.3(b).
    Romanette ii confers an exclusivity period of five years,
    during which “no [abbreviated] application which refers to the
    [first-in-time] drug” may be approved.            21 U.S.C.
    § 355(c)(3)(E)(ii). FDA regulations interpret exclusivity
    under romanette ii to block any abbreviated application for a
    drug whose active moiety is the same as the New Chemical
    Entity. 21 C.F.R. § 314.108(a).
    6
    Romanettes iii and iv award marketing exclusivity to
    innovations more modest than the introduction of a New
    Chemical Entity.     The exclusivity conferred by those
    provisions correspondingly is more confined in scope and
    duration than the five-year exclusivity afforded under
    romanette ii.
    Under romanette iii, an application “for a drug, which
    includes an [active moiety] that has been approved in another
    application,” is entitled to three years of exclusivity “if such
    application contains reports of new clinical investigations . . .
    essential to the approval of the application and conducted or
    sponsored by the applicant.” 21 U.S.C. § 355(c)(3)(E)(iii). In
    other words, romanette iii confers exclusivity when a
    pharmaceutical company obtains approval to market a
    previously approved active moiety in a new formulation or for
    new purposes, and doing so requires it to furnish new clinical
    investigations to the FDA. With regard to the scope of drugs
    affected by the three-year exclusivity period, the FDA may
    not approve an abbreviated application for the same
    “conditions of approval of such drug in the [first-in-time]
    application.” 
    Id. Romanette iv
    similarly grants a three-year exclusivity
    period to applicants that “supplement” a previously approved
    application if obtaining approval of the supplement requires
    submitting additional reports and investigations to the agency.
    
    Id. § 355(c)(3)(E)(iv).
    Romanette iv thus applies, for
    instance, to companies seeking to indicate an existing drug
    product for additional illnesses or otherwise alter the
    product’s labeling. The scope of exclusivity encompasses
    abbreviated applications “for a change approved in the
    supplement” to the first-in-time drug’s application. 
    Id. As with
    the scope-delimiting phrase “conditions of approval of
    such drug” in romanette iii, the FDCA does not define the
    7
    precise meaning of the scope-delimiting phrase “for a change
    approved in the supplement” in romanette iv.
    B.
    In 2002, Otsuka obtained FDA approval for Abilify
    Tablets, an antipsychotic drug. In the ensuing fifteen years,
    Otsuka has received FDA approval for a number of additional
    drug products sharing Abilify Tablets’ active moiety:
    aripiprazole. The formulation of aripiprazole at issue in this
    case, Abilify Maintena, is taken on a monthly basis by
    injection.
    Abilify Tablets earned a five-year exclusivity period
    under romanette ii for introducing aripiprazole as a New
    Chemical Entity. Although the five-year period for Abilify
    Tablets lapsed nearly a decade ago, Abilify Maintena
    subsequently received two successive marketing-exclusivity
    periods of three years each. The first three-year period, which
    expired on February 28, 2016, came under romanette iii in
    connection with Abilify Maintena’s initial approval. The
    second three-year period remains ongoing—it expires on
    December 5, 2017—and was awarded under romanette iv in
    connection with a supplemental application filed by Otsuka.
    That supplement involved a new study showing Abilify
    Maintena’s efficacy in the treatment of adult schizophrenia
    patients experiencing an acute relapse.
    On August 22, 2014, Alkermes submitted an abbreviated
    (b)(2) application for Aristada, another injectable
    antipsychotic. The application for Aristada included a clinical
    trial conducted by Alkermes to demonstrate the drug’s safety
    and efficacy at intervals up to six weeks. The company also
    sought to rely on prior studies conducted by Otsuka
    demonstrating the safety and efficacy of Abilify Tablets.
    8
    Aristada shares certain chemical similarities with the Abilify
    line of products: Aristada’s active moiety, N-hydroxymethyl
    aripiprazole, is a “prodrug” of aripiprazole, meaning that it
    ultimately metabolizes into aripiprazole in the body.
    Nonetheless, under the FDA’s approach to determining a
    drug’s active moiety, which this Court upheld in Actavis
    Elizabeth LLC v. FDA, 
    625 F.3d 760
    , 765-66 (D.C. Cir.
    2010), Aristada’s and Abilify Maintena’s active moieties are
    distinct. The FDA “starts with the molecule that comprises
    that active ingredient in the drug product, and excludes the
    ester and salt-bonded portions of the molecule.” J.A. 426.
    The remaining molecule or ion is the drug’s active moiety.
    
    Id. N-hydroxymethyl aripiprazole
    (Aristada) differs from
    aripiprazole (Abilify Maintena) in containing the “addition of
    a hydroxymethyl group, connected by a [non-ester] covalent
    C-N bond.” J.A. 435. That difference suffices under the
    FDA’s standard to distinguish the two moieties.
    Otsuka filed two citizen petitions requesting that the FDA
    deny approval of Aristada, or, alternatively, defer its approval
    until Abilify Maintena’s exclusivity periods lapsed. The FDA
    denied both petitions. The agency determined that Alkermes
    had properly invoked known information about aripiprazole
    for the purpose of demonstrating Aristada’s safety and
    efficacy. But the agency concluded that Abilify Maintena’s
    marketing exclusivity did not foreclose Aristada’s approval
    because the two drugs have different active moieties. In
    reaching that conclusion, the FDA reasoned that the FDCA’s
    marketing-exclusivity provisions block approval only of drug
    products with the same active moiety as the drug benefitting
    from exclusivity.
    Otsuka sought review in the district court. Otsuka argued
    that the FDA’s same-moiety requirement: (i) conflicts with
    9
    the FDCA; (ii) diverges from the agency’s own regulations;
    and (iii) came into existence in violation of the Administrative
    Procedure Act because the agency effectively amended its
    regulations without resort to notice-and-comment procedures.
    Alkermes, seeking to preserve the agency’s approval of
    Aristada, intervened in the dispute.
    The district court granted summary judgment in favor of
    the FDA and Alkermes. Otsuka Pharm. Co. v. Burwell, Civ.
    No. 15-cv-1688, 
    2016 WL 4098740
    (D.D.C. July 28, 2016).
    The court held that “the FDCA does not unambiguously
    prevent the FDA from determining that the FDCA’s three-
    year exclusivity bar blocks only subsequent applications for
    drugs with the same active moiety,” and that “it was not
    unreasonable for the FDA to have employed that
    interpretation.” 
    Id. at *2.
    The court further concluded that,
    because Abilify Maintena’s initial exclusivity period
    conferred by romanette iii had expired in February 2016,
    Otsuka’s claim under that period had become moot. 
    Id. at *6
    n.8. Finally, the court held that the FDA need not have
    undertaken notice-and-comment procedures because the
    same-moiety requirement was consistent with the agency’s
    existing regulations. 
    Id. at *21.
    II.
    The FDA understands a drug’s marketing exclusivity to
    require withholding approval only of drug products that share
    the same active moiety. Otsuka challenges the agency’s
    same-moiety interpretation, arguing that the FDCA calls for a
    broader understanding of the zone of marketing exclusivity
    conferred by romanettes iii and iv. In Otsuka’s view, the
    FDA’s interpretation cannot be squared with the statute and
    conflicts with the agency’s own regulations. We reject
    10
    Otsuka’s arguments under both the statute and the regulations,
    and we therefore sustain the FDA’s interpretation.
    At the outset, we note that Abilify Maintena’s initial
    three-year period of exclusivity, conferred under romanette
    iii, has expired. As a result, we agree with the district court
    that Otsuka’s claims with regard to that exclusivity period
    have become moot. See Otsuka, 
    2016 WL 4098740
    , at *6
    n.8. But we further agree with the district court that the
    mootness of Otsuka’s challenge concerning romanette iii does
    not materially affect our analysis. See 
    id. Abilify Maintena’s
    subsequent three-year exclusivity period, conferred under
    romanette iv, remains ongoing. And Otsuka’s arguments
    concerning the scope of exclusivity granted by romanette iv
    depend on, and substantially overlap with, its arguments
    concerning romanette iii. As a result, understanding and
    addressing the former necessarily requires examining the
    latter.
    A.
    Romanettes iii and iv, in conferring a three-year period of
    marketing exclusivity, are ambiguous as to the relationship, if
    any, a second-in-time drug must bear to a first-in-time drug in
    order to be subject to the latter’s exclusivity. All parties agree
    that the first- and second-in-time drugs must bear some
    relationship to one another. But they disagree about the
    nature of the necessary relationship. In the FDA’s view,
    marketing exclusivity applies as between two drugs sharing
    the same active moiety. Otsuka, by contrast, contends that
    exclusivity more broadly covers any two drugs that are “legal
    equivalents”—a term of Otsuka’s invention that draws an
    equivalence between two drugs whenever one relies upon the
    other to receive approval.
    11
    We must sustain the FDA’s interpretation of the scope of
    exclusivity afforded by romanettes iii and iv as long as it is
    consistent with the statutory terms and is reasonable. See
    Chevron, U.S.A., Inc. v. Nat. Res. Def. Council, Inc., 
    467 U.S. 837
    (1984). The agency’s understanding comfortably meets
    those standards.
    1.
    a. The FDA’s basic understanding is that the extent of
    marketing exclusivity conferred by each of the statutory
    romanettes is commensurate with the degree of innovation
    required to earn exclusivity under it. With regard to
    romanette ii, therefore, the first drug to receive FDA approval
    for a given active moiety will block approval of all
    abbreviated applications for a drug with that same active
    moiety for five years. The scope of exclusivity under
    romanettes iii and iv is more limited, but so is the innovation
    giving rise to it.
    Under romanette iii, an applicant who establishes the
    safety and efficacy of a previously approved active moiety for
    new “conditions of approval,” 21 U.S.C. § 355(c)(3)(E)(iii),
    will thereby trigger a three-year period in which the agency
    must withhold approval of drugs with the same conditions of
    approval and the same active moiety. A parallel approach
    governs romanette iv, which applies when the FDA approves
    a “change . . . in the supplement” to a previously approved
    application. 
    Id. § 355(c)(3)(E)(iv).
    In that event, a drug
    product seeking to make use of the “change approved in the
    supplement,” 
    id., cannot gain
    approval for a period of three
    years if it has the same active moiety as the previously
    approved drug.
    12
    The upshot is that, if a pharmaceutical company
    innovates with respect to a given active moiety, the statutory
    romanettes protect the full extent of the innovation, but only
    against drugs with the same active moiety. A drug’s active
    moiety thus determines its eligibility for exclusivity and
    delimits the scope of drugs whose approval is potentially
    foreclosed by that exclusivity.
    b. Romanettes iii and iv do not specify what relationship,
    if any, must exist between two drugs for marketing
    exclusivity to come into play. But the statute contains a
    textual grounding for the FDA’s same-moiety interpretation.
    Romanette iii, in pertinent part, bars abbreviated
    applications “for the conditions of approval of such drug in
    the approved subsection (b) application.” 21 U.S.C.
    § 355(c)(3)(E)(iii).  The phrase “drug in the approved
    subsection (b) application” refers to “a drug, which includes
    an [active moiety] that has been approved in another
    application.” 
    Id. All parties
    correctly understand that cross-
    reference to refer to the first-in-time drug benefitting from
    exclusivity.
    The statutory language, however, does not specify
    whether exclusivity applies whenever the second-in-time
    application is for the “conditions of approval” of the first-in-
    time drug, or whether the second-in-time application, to be
    excluded, must also involve the same drug as the first-in-time
    one. In other words, is it enough for a second-in-time
    application to share “the conditions of approval of such drug
    in the [first-in-time] application,” or must it also be for the
    same “drug in the [first-in-time] application”? 
    Id. (emphases added).
                                   13
    The former understanding would cast an exclusivity-
    bearing drug’s “conditions of approval” as the sole gatekeeper
    of exclusivity under romanette iii, giving the scope of
    exclusivity a capacious reach. For instance, imagine that a
    company originally received approval to market a drug with a
    given active moiety as a means of treating depression. Then,
    suppose the company conducts studies showing that the
    drug’s active moiety also addresses insomnia, and obtains
    approval to market a new drug product with that active moiety
    as an anti-insomnia medication. The new drug product would
    benefit from a three-year exclusivity period for that new
    “condition of approval” (i.e., as a treatment for insomnia). If
    an exclusivity-bearing drug’s conditions of approval were the
    sole gatekeeper of exclusivity, the FDA, for three years,
    would be required to withhold approval of any drug seeking
    abbreviated approval to treat insomnia, regardless of whether
    the applied-for drug bore any chemical association with the
    first-in-time drug.
    Unsurprisingly, the FDA rejects that interpretation. The
    agency instead takes the position that, in order to be subject to
    a first-in-time drug’s exclusivity, a second-in-time application
    must also be for the same drug in the first-in-time application.
    So in the example just referenced, the first-in-time drug’s
    exclusivity would not block all anti-insomnia treatments,
    regardless of chemical makeup. Rather, in keeping with the
    scope of the innovation giving rise to the three-year period of
    exclusivity, it would block only those anti-insomnia
    treatments involving the same drug.
    That conclusion then raises a second ambiguity: when
    should a second-in-time drug be considered the same as the
    drug in the first-in-time application? The agency rejects a
    narrow understanding under which “exclusivity covers only
    specific drug products and therefore protects from generic
    14
    competition only the first approved version of a drug, or
    change in a drug.” Abbreviated New Drug Application
    Regulations, 54 Fed. Reg. 28,872-01, at 28,897 (July 10,
    1989). Construing the statute in that way would provide little
    protection to innovators. For instance, a second-in-time (b)(2)
    applicant could easily move itself outside a previously
    approved drug product’s zone of exclusivity merely by
    altering one of that product’s inactive ingredients.
    The FDA instead concludes that a first-in-time drug’s
    marketing exclusivity attaches, not to the specific drug
    product receiving approval, but to a particular feature of the
    drug: its active moiety.            The agency derives that
    understanding from the fact that all three romanettes condition
    a drug’s eligibility for exclusivity on whether its “active
    ingredient (including any ester or salt of the active
    ingredient)”—i.e., its active moiety—has been approved in a
    previous application. 21 U.S.C. § 355(c)(3)(E)(ii)-(iv).
    Noting that romanette iii’s language, “such drug in the [first-
    in-time] application,” refers to “a drug, which includes an
    [active moiety] that has been approved in another
    application,” the FDA concludes that any second-in-time drug
    that includes an exclusivity-benefitted drug’s active moiety is
    likewise subject to its exclusivity. Having long considered a
    drug’s active moiety to be its distinguishing feature for
    purposes of determining its eligibility for marketing
    exclusivity, see Abbreviated New Drug Application
    Regulations; Patent and Exclusivity Provisions, 59 Fed. Reg.
    50338-01, at 50357-58 (Oct. 3, 1994), the FDA here
    correspondingly concludes that marketing exclusivity under
    romanette iii does not apply to a second-in-time drug with
    “conditions of approval” that may overlap with those of the
    first-in-time drug, but with a different active moiety.
    15
    The FDA interprets romanette iv in parallel fashion.
    Under that provision, an abbreviated application will be
    barred during a first-in-time drug’s three-year exclusivity
    period if it is “for a change approved in the supplement” to
    the previously approved application.               21 U.S.C.
    § 355(c)(3)(E)(iv). The statutory language, again, does not
    specify whether, to be excluded, it is enough for a second-in-
    time abbreviated application to be “for a change approved in
    the supplement” to the first-in-time application, or whether it
    must also be for the drug in the supplemented application.
    Mirroring its treatment of romanette iii, the FDA opted
    for the latter interpretation. The agency begins by noting that
    a pharmaceutical company cannot alter the active moiety of a
    drug product when supplementing the drug’s application. See
    Guidance for Industry: Submitting Separate Marketing
    Applications and Clinical Data for Purposes of Assessing
    User Fees, FOOD & DRUG ADMIN. 3 (Dec. 2004). As a result,
    “a change approved in the supplement” to an application must
    be a change in the conditions of approval for that specific
    drug—for instance, an alteration in its labeling or indications,
    as with Abilify Maintena’s supplemented labeling indicating
    its efficacy in treating adult schizophrenia patients
    experiencing an acute relapse.
    The FDA correspondingly reads romanette iv to provide
    that, to infringe a previously approved drug’s three-year
    exclusivity under that provision, a second-in-time application
    must not only be for the “change approved in the supplement”
    to the previously approved drug’s application, but also must
    be for the same drug (i.e., a drug containing the same active
    moiety). Marketing exclusivity therefore would not apply, for
    instance, to an abbreviated application for a drug with a
    different active moiety, the label for which happened to
    16
    overlap in some way           with   the   first-in-time   drug’s
    supplemented labeling.
    2.
    Otsuka contends that the FDA’s same-moiety limitation
    on the scope of exclusivity conferred by romanettes iii and iv
    is inconsistent with the statute. Because none of Otsuka’s
    arguments “unambiguously foreclose[s] the agency’s
    construction of the statute,” we defer to the FDA’s reasonable
    interpretation. Cablevision Sys. Corp. v. FCC, 
    649 F.3d 695
    ,
    704 (D.C. Cir. 2011); accord 
    Actavis, 625 F.3d at 765
    .
    a. Otsuka’s central submission is that a principle it terms
    “legal equivalence” must be read into the FDCA’s marketing-
    exclusivity provisions.      Legal equivalence, as Otsuka
    conceives it, is broader than (but apparently inclusive of)
    equivalence in active moieties. And if two drugs are legally
    equivalent, Otsuka posits, approval of the second-in-time drug
    should be subject to the first-in-time drug’s exclusivity,
    regardless of whether the two drugs share the same active
    moiety.
    Otsuka appears to believe that two drugs should be
    considered legal equivalents in at least the following
    scenarios: (i) the two drugs share the same active moiety; (ii)
    one drug relies on the other drug to receive FDA approval; or
    (iii) one drug relies on a drug that is itself legally equivalent
    to (i.e., satisfies one of the first two conditions with respect
    to) the other drug. On that understanding, Aristada and
    Abilify Maintena are legally equivalent: Aristada relied in its
    application on Abilify Tablets, which in turn is legally
    equivalent to Abilify Maintena because the two drugs share
    the same active moiety (aripiprazole), and also because
    Abilify Maintena itself relied on Abilify Tablets for approval.
    17
    Consequently, as Otsuka sees it, the FDA erred by permitting
    Aristada to rely on aripiprazole (Abilify Tablets) for approval,
    but treating Aristada as distinct from aripiprazole (Abilify
    Maintena) for purposes of defining the latter product’s zone
    of exclusivity.
    Congress perhaps could have written a statute under
    which, if one drug relies on the safety or efficacy of a
    previously approved drug to obtain approval, the two drugs
    must be considered “legally equivalent” for purposes of
    defining the previously approved drug’s zone of exclusivity.
    But the statutory romanettes nowhere expressly set out any
    concept of legal equivalence in describing the scope of
    marketing exclusivity. Instead, Otsuka claims to find a
    footing for its theory in the FDCA’s provisions governing
    new drug applications, which in turn, the company contends,
    informs the proper interpretation of the romanettes.
    Otsuka’s complex, multi-layered theory begins with the
    FDCA’s condition that a new drug application must contain
    “full reports of investigations which have been made to show
    whether or not such drug is safe for use and whether such
    drug is effective in use.” 21 U.S.C. § 355(b)(1) (emphasis
    added). Otsuka notes that an abbreviated (b)(2) application,
    which must also satisfy that condition, can do so by relying on
    studies showing the safety and efficacy of an already
    approved drug. As a result, Otsuka reasons, at least some of
    the investigations submitted in connection with a (b)(2)
    application would “have been made to show,” not that the
    applied-for drug is safe and effective, but that the relied-upon
    drug is safe and effective.
    With that premise in mind, Otsuka returns to
    § 355(b)(1)’s statement that a new drug application (including
    a (b)(2) application) must contain “full reports of
    18
    investigations which have been made to show whether or not
    such drug” is safe and effective. 
    Id. (emphasis added).
    Because at least some of the investigations invoked in support
    of a (b)(2) application will concern the relied-upon drug,
    Otsuka reasons, the phrase “such drug” in § 355(b)(1) must
    encompass, not just the drug for which approval is sought, but
    also any drug on which the application relies. In that way,
    Otsuka submits, the phrase “such drug” necessarily embraces
    a concept of legally equivalent drugs—i.e., drugs treated as
    the same drug under the statute because one relied on the
    other to secure approval.
    Otsuka’s theory cannot stop there, because the company
    still needs to export the concept of legal equivalence from
    § 355(b)(1), which pertains to new drug applications, into the
    statutory romanettes, which pertain to marketing exclusivity.
    For that next step, Otsuka invokes the general assumption that
    “identical words used in different parts of the same act are
    intended to have the same meaning.” Comm’r v. Lundy, 
    516 U.S. 235
    , 250 (1996) (quoting Sullivan v. Stroop, 
    496 U.S. 478
    , 484 (1990)). That assumption means, to Otsuka, that the
    phrase “such drug” must embrace a drug and its legal
    equivalents, not just in § 355(b)(1), but anywhere that phrase
    appears in the pertinent provisions of the FDCA.
    One such provision is romanette iii. In relevant part,
    romanette iii blocks approval of second-in-time (b)(2)
    applications “for the conditions of approval of such drug” in
    the first-in-time application. 21 U.S.C. § 355(c)(3)(E)(iii)
    (emphasis added). Otsuka reasons that, because “such drug”
    in § 355(b)(1) refers to a drug and its legal equivalents, “such
    drug” in romanette iii likewise should embrace a drug’s legal
    equivalents. As a result, Otsuka concludes, the marketing
    exclusivity afforded by romanette iii requires withholding
    19
    approval of any drugs that are legally equivalent to the first-
    in-time drug and share its conditions of approval.
    Finally, although romanette iv (as opposed to romanette
    iii) does not contain the words “such drug,” Otsuka suggests
    that the concept of legal equivalence should be read into
    romanette iv, as well, in order to maintain symmetry across
    the romanettes with regard to the scope of marketing
    exclusivity.       The endpoint of Otsuka’s multi-step
    interpretation thus is that a second-in-time drug is subject to
    the marketing exclusivity of any drug it relies upon (and that
    drug’s legal equivalents), regardless of whether the drugs
    share the same active moiety.
    b. For Otsuka’s theory to prevail, it would need to show
    not only that its interpretation is permissible, but that the
    agency’s alternative understanding is not. See, e.g., 
    Actavis, 625 F.3d at 765
    . Otsuka falls far short of making that
    showing.
    To start with the initial premise of Otsuka’s theory, the
    FDA’s competing reading of § 355(b)(1)’s “made to show”/
    “such drug” language is entirely reasonable. Otsuka’s
    interpretation, as explained, construes the phrase “such drug”
    to refer simultaneously to the applied-for drug (e.g., Aristada)
    and any drug on which the application relies (e.g., Abilify
    Tablets)—which, to Otsuka, means that “such drug”
    embodies a concept of legal equivalence between the applied-
    for drug and any relied-upon drug. The agency, by contrast,
    interprets “such drug” to refer solely to the applied-for drug.
    The agency’s interpretation draws significant support
    from the statutory history. For nearly a half century, “such
    drug” could have referred only to the applied-for drug. Those
    words were part of the original FDCA in 1938, in the
    20
    precursor provision to § 355(b). See Food, Drug, and
    Cosmetic Act, Pub. L. No. 75-717, § 505(b), 52 Stat. 1040,
    1052 (1938). And it was not until the Hatch-Waxman
    Amendments in 1984 that the statute even provided for
    abbreviated pathways through which an applicant could rely
    on investigations concerning a previously approved drug.
    Until then, consequently, the “investigations which have been
    made to show whether or not such drug” is safe and effective
    necessarily referred to investigations showing the safety and
    efficacy of the applied-for drug, not any previously approved
    drug.
    To the extent those same words could have taken on a
    new meaning following introduction of the abbreviated
    pathways in 1984, the agency’s interpretation of “such drug”
    to mean (only) the applied-for drug remains entirely sound.
    Under that interpretation, an application can satisfy
    § 355(b)(1)’s condition—that it include “full reports of
    investigations which have been made to show whether or not
    such drug is safe and effective for use”—as long as the
    investigations show the applied-for drug’s safety and
    effectiveness. To be sure, in a (b)(2) application, the
    investigations relied upon can include ones that originally
    involved testing of a previously approved drug. But those
    investigations still could serve to show—and thus could
    qualify as now being “made to show”—the applied-for drug’s
    safety and effectiveness, provided the drug’s proponent
    established a scientific basis for reaching that conclusion.
    In that light, the agency’s reading of “made to
    show”/“such drug” in § 355(b)(1) is fully reasonable, and
    considerably more straightforward than Otsuka’s. And
    because the agency understands “such drug” to refer solely to
    the applied-for drug, its reading, unlike Otsuka’s, does not
    21
    involve any concept of legal equivalence between an applied-
    for drug and other drugs on which it may rely.
    Even if we assume Otsuka’s reading of “such drug” in
    § 355(b)(1) is controlling, Otsuka again falls short in its effort
    to transport its preferred understanding of “such drug” from
    § 355(b)(1) into the statutory romanettes. Because Otsuka
    cannot make that essential showing, its statutory argument,
    independent of any other shortcomings, must fail.
    Otsuka asserts that we should treat the words “such
    drug,” which appear nearly fifty times in Section 505 of the
    FDCA alone, as a statutory term of art. Doing so would be
    the reductio ad absurdum of the “normal rule of statutory
    construction that identical words used in different parts of the
    same act are intended to have the same meaning.” 
    Lundy, 516 U.S. at 250
    (citation omitted). By nature, the object of the
    word “such” entirely depends on context.            See Such,
    MERRIAM-WEBSTER’S COLLEGIATE DICTIONARY (11th ed.
    2003) (defining “such” as “of the character, quality, or extent
    previously indicated or implied”). Consequently, the words
    “such drug” might readily refer to one drug in one instance
    and another drug in another.
    So even if it were true—which it is not—that the words
    “such drug” in § 355(b)(1) can only be read to refer
    simultaneously to the applied-for and the relied-upon drug, it
    would not necessarily follow that those words in romanette iii
    should carry the same meaning. Whereas § 355(b)(1) pertains
    to new drug applications, romanette iii is a distinct provision
    dealing with the distinct subject of marketing exclusivity. As
    a result, even if § 355(b)(1)’s reference to “such drug”
    encompasses drugs that rely on one another for purposes of
    meeting the criteria for a new drug application, that still
    would not establish that the same, legal-equivalence
    22
    understanding must inform a separate provision dealing with a
    separate subject.
    Once again, the agency’s competing interpretation of the
    relevant statutory language is entirely reasonable. The agency
    reads the language of romanette iii to indicate that “such
    drug,” in context, refers only to the first-in-time drug
    benefitting from exclusivity. The provision precludes the
    FDA from approving an ANDA or (b)(2) application “for the
    conditions of approval of such drug in the approved
    subsection (b) application,” which in turn refers to the drug
    that “includes an [active moiety] that has been approved in
    another application.” 21 U.S.C. § 355(c)(E)(iii) (emphasis
    added). “Such drug,” then, is a specific “approved” drug:
    namely, the drug (i.e., active moiety) entitled to the three-year
    period of exclusivity conferred by romanette iii. Nothing in
    the statute requires concluding that the reference to “such
    drug” automatically embraces so-called legal equivalents to it.
    (And that is to say nothing of the fact that romanette iv, unlike
    romanette iii, does not contain the words “such drug” at all.)
    The implications of Otsuka’s conception of legal
    equivalence further counsel against concluding that Congress
    intended to incorporate it into the statutory romanettes. Under
    Otsuka’s interpretation, if one drug relies on another to obtain
    abbreviated approval for the same conditions of approval, the
    relied-upon drug’s zone of exclusivity necessarily
    encompasses the applied-for drug. That theory would apply
    regardless of the reason that the abbreviated application relied
    on the previously approved drug.
    But a (b)(2) application can rely on any scientific
    investigations, including general academic literature, that help
    to establish the applied-for drug’s safety and efficacy. See 
    id. § 355(b)(1).
    So, for instance, a (b)(2) application could
    23
    rely—and in at least one instance has relied, Intervenor Br.
    30-31 & n.10—on a prior study to show the safety of an
    inactive ingredient in the applied-for drug. Otsuka’s reading
    thus would treat two drug products as legally equivalent, such
    that one’s exclusivity would preclude approval of the other,
    even though the only intersection between the two products
    involved an inactive ingredient. There is no reason to
    suppose Congress intended the scope of a drug’s marketing
    exclusivity to sweep so far.
    Otsuka’s notion of legal equivalence also stands in
    considerable tension with our decision in Actavis Elizabeth
    LLC v. FDA, 
    625 F.3d 760
    (D.C. Cir. 2010). That case
    involved prodrugs (which, as noted, are drugs that eventually
    metabolize into a different chemical compound in the body).
    We upheld the FDA’s understanding that a prodrug of a
    previously approved drug, if it has a different active moiety,
    can qualify as a “major innovation[]” entitled to “‘[N]ew
    [C]hemical [E]ntity’ status and the resulting five-year
    exclusivity” afforded under romanette ii. 
    Id. at 765.
    We said
    we would be “hard pressed to second guess” the FDA’s
    considered view that such a drug is sufficiently “distinct” so
    as to be “uniquely deserving” of New Chemical Entity status.
    
    Id. at 765-66.
    If we accepted Otsuka’s assertion that the scope of
    marketing exclusivity under the FDCA is governed by a
    principle of legal equivalence, that principle would apply no
    less to the five-year exclusivity period granted by romanette ii
    than to the three-year periods granted by romanettes iii and iv.
    According to Otsuka’s reading, consequently, the FDA would
    be required to treat a New Chemical Entity entitled to a five-
    year exclusivity period under Actavis—i.e., a “major
    innovation” containing no active moiety that “has been
    approved in any other application,” 21 U.S.C.
    24
    § 355(c)(3)(E)(ii)—as equivalent to any previously approved
    drug on which it relied for approval. Otsuka fails to persuade
    us that the FDCA unambiguously contains a principle of legal
    equivalence under which even a drug earning the status of a
    New Chemical Entity is equivalent to a previously approved
    drug.
    c. Otsuka does not advance its cause by relying on the
    patent-certification measures pertaining to (b)(2) applications.
    A (b)(2) applicant must certify that sale of the applied-for
    drug would not infringe upon a valid patent with respect to
    any relied-upon drug. See 21 U.S.C. § 355(b)(2)(A). The
    provision states that the applicant must include a certification
    “with respect to each patent which claims the drug for which
    such investigations were conducted or which claims a use for
    such drug for which the applicant is seeking approval.” 
    Id. (emphasis added).
    Otsuka’s argument with regard to that
    language parallels its earlier argument under § 355(b)(1).
    Otsuka again asserts that “such drug” in the patent-
    certification provision refers both to the relied-upon and the
    applied-for drug, and that the words thus embody a principle
    of legal equivalence. Otsuka accordingly claims that the FDA
    “effectively conced[ed]” that Aristada and Abilify Maintena
    are legally equivalent when it required Alkermes’ new drug
    application for Aristada to certify to method-of-use patents for
    aripiprazole. Appellants’ Br. 28.
    Otsuka gets no further with this legal-equivalence
    argument than it did with the earlier one. Here, too, Otsuka’s
    reading of “such drug” is hardly compelled. Those words
    refer back to “the drug for which [the relied-upon]
    investigations were conducted.” 21 U.S.C. § 355(b)(2)(A).
    That drug is the relied-upon drug, not the applied-for drug.
    And although the words “such drug” appear in a phrase
    referring to a patent “which claims a use for such drug for
    25
    which the applicant is seeking approval,” 
    id. (emphasis added),
    the emphasized language is most naturally read to
    modify “use,” not “such drug”—i.e., the “use . . . for which
    the applicant is seeking approval,” not the “drug for which the
    applicant is seeking approval.” So understood, “such drug”
    refers solely to the relied-upon drug, not to both the relied-
    upon and applied-for drugs.
    In any event, even if we assume Otsuka’s understanding
    of “such drug” in the patent-certification provision is
    controlling, Otsuka once again runs aground in assuming that
    its preferred interpretation of “such drug” in that provision
    would necessarily carry over to “such drug” in romanette iii.
    The patent-certification provision is a prophylactic measure to
    notify a patent holder of possible infringement by a new drug
    application that relies on one of its drugs. In that light, the
    fact that Alkermes was required to certify to Otsuka’s
    method-of-use patents for aripiprazole in no way constitutes a
    concession that the two drugs are “equivalent” for purposes of
    the FDCA’s marketing-exclusivity provisions. As the agency
    has explained, marketing exclusivity under the romanettes is a
    distinct form of protection from that afforded by the patent
    system. See generally Frequently Asked Questions on Patents
    and       Exclusivity,     FOOD      &      DRUG       ADMIN.,
    https://www.fda.gov/Drugs/DevelopmentApprovalProcess/uc
    m079031.htm (last updated Dec. 5, 2016). We see no reason
    to conclude that the patent-certification provision does
    anything more than guard against patent infringement,
    without speaking to—much less defining—the zone of a
    drug’s marketing exclusivity.
    d. In a final attempt to persuade the Court, Otsuka warns
    of the practical implications of upholding the FDA’s same-
    moiety requirement. According to Otsuka, unless the scope
    of marketing exclusivity extends to legally equivalent drugs,
    26
    competitors will be able to rely on an innovator’s drug while
    readily evading its exclusivity. In particular, Otsuka explains
    that “[p]ioneer drug companies will be reluctant to develop
    new, innovative drugs if their marketing exclusivity can be
    easily circumvented by a follow-on company that creates a
    prodrug of the pioneer product’s active moiety.” Appellants’
    Br. 18.
    Otsuka’s argument in that respect boils down to an
    attempt to re-litigate this Court’s decision in Actavis, 
    625 F.3d 760
    . There, as explained, we upheld the FDA’s position that
    a prodrug of a previously approved drug, if it contains a
    different active moiety, is entitled to the five-year exclusivity
    period granted to a New Chemical Entity. Otsuka’s argument
    that the statute should be read to bar competitors from
    receiving approval for such prodrugs thus “represent[s] little
    more than question-begging”: “In the FDA’s view,” prodrugs
    with previously unapproved active moieties “are ‘major
    innovations’ deserving five-year exclusivity,” even if they
    ultimately metabolize into a previously approved active
    moiety. 
    Id. at 765-66.
    We have no occasion to revisit our
    decision in Actavis, or to question the FDA’s expert judgment
    that “even minor covalent structural changes are capable of
    producing . . . major changes in the activity of a drug.” 
    Id. * *
       *
    For those reasons, Otsuka fails to show that the language
    of the FDCA unambiguously compels its “legal-equivalence”
    interpretation of the scope of marketing exclusivity under the
    romanettes. Rather, the agency’s same-moiety interpretation
    is reasonable and warrants our deference.
    27
    B.
    As a fallback to its statutory arguments, Otsuka claims
    that the FDA’s same-moiety interpretation should be rejected
    as irreconcilable with the agency’s own regulations and past
    statements.      “An agency’s interpretation of its own
    regulations is entitled to judicial deference,” and is controlling
    unless “plainly erroneous or inconsistent with the
    regulation[s].” 
    Actavis, 625 F.3d at 763
    (internal quotation
    marks omitted). We see no reason to reject the FDA’s same-
    moiety interpretation as incompatible with the agency’s
    regulations implementing the statutory romanettes. Those
    regulations largely parrot the language of the romanettes,
    which, as we have found, comfortably accommodate the
    agency’s same-moiety rule. The same is true of the
    regulations.
    Otsuka observes that the regulation implementing
    romanette ii explicitly imposes a “same active moiety”
    limitation on the scope of the five-year exclusivity period
    conferred by that provision. 21 C.F.R. § 314.108(b)(2). By
    contrast, Otsuka notes, the regulations pertaining to
    romanettes iii and iv contain no such language expressly
    establishing a same-moiety requirement.              See 
    id. §§ 314.108(b)(4),
    (b)(5). As a result, Otsuka reasons, the
    latter regulations should be understood implicitly to reject a
    same-moiety limitation. We disagree.
    Under Otsuka’s reading, the three-year exclusivity
    periods under romanettes iii and iv would be broader in
    scope—because they would be unencumbered by a same-
    moiety limitation—than the five-year period conferred by
    romanette ii. That result would make little sense. Romanette
    ii confers exclusivity in connection with a more significant
    innovation, and hence awards a longer exclusivity period,
    28
    than romanettess iii and iv. If anything, then, one would
    expect romanette ii to grant a broader scope of exclusivity. In
    that light, the agency can permissibly understand the express
    inclusion of a same-moiety limitation in the romanette-ii
    regulation to make especially clear that such a limitation
    constrains the broader exclusivity conferred by that
    regulation, rather than to imply that the same limitation does
    not govern the narrower exclusivity conferred by the
    romanette-iii and -iv regulations.
    Otsuka next points to the language of the regulation
    corresponding to romanette iii. That regulation, Otsuka
    emphasizes, provides that three-year marketing exclusivity
    under romanette iii bars second-in-time applications “for the
    conditions of approval of the original application” rather than
    “for the conditions of approval of such drug.”               
    Id. § 314.108(b)(4).
    Otsuka argues that the absence of the “such
    drug” language undermines the agency’s position that the
    regulation accommodates a same-moiety limitation. But it is
    Otsuka, not the FDA, that attaches dispositive significance to
    the words “such drug.” The FDA, for its part, persuasively
    contends that the phrase “the conditions of approval of the
    original application” can just as easily accommodate a same-
    moiety limitation as the phrase “the conditions of approval of
    such drug.”
    Otsuka also identifies past FDA statements that it reads to
    be incompatible with the agency’s present espousal of a same-
    moiety limitation. But the only instance in which the agency
    appears to have squarely expressed a contrary view was in a
    2010 opinion letter concerning the glaucoma medicine
    Lumigan. In that letter, the FDA stated that Lumigan “could
    not [have] receive[d] approval for 3 years” following another
    drug’s (Xalatan’s) receipt of a three-year exclusivity period
    under romanette iii, even though the two drugs have different
    29
    active moieties. J.A. 121. The FDA’s position in that letter
    plainly assumed that romanette iii does not include a same-
    moiety limitation.
    Agencies, however, can change their interpretations
    provided that they acknowledge and explain the change and
    the new position is otherwise permissible. See FCC v. Fox
    Television Stations, Inc., 
    556 U.S. 502
    , 516 (2009). That is
    what the FDA did in this case. In its letter denying Otsuka’s
    petitions, the FDA explicitly acknowledged its comments in
    the Lumigan letter. The denial letter then explained the
    agency’s various reasons for adopting its present position now
    that the issue was “squarely before the Agency.” J.A. 441
    n.87. Those reasons mirror the ones discussed throughout this
    opinion. In those circumstances, there is no reason to deny
    deference to the agency’s present interpretation.
    Finally, we are unpersuaded by Otsuka’s contention that
    the agency was required to adopt the same-moiety limitation
    through notice-and-comment rulemaking. Because the same-
    moiety requirement is not “a new position inconsistent with
    an existing regulation” and does not work “a substantive
    change in [any] regulation,” there was no need for the FDA to
    have undertaken notice and comment procedures before
    adopting it. U.S. Telecomm. Ass’n v. FCC, 
    400 F.3d 29
    , 35
    (D.C. Cir. 2005) (emphasis and internal parenthesis removed).
    *    *   *    *   *
    For the foregoing reasons, we affirm the district court’s
    grant of summary judgment.
    So ordered.
    Appendix
    21 U.S.C. § 355(c)(3)(E)
    (ii) If an application submitted under subsection (b) of this
    section for a drug, no active ingredient (including any ester or
    salt of the active ingredient) of which has been approved in
    any other application under subsection (b) of this section, is
    approved after September 24, 1984, no application which
    refers to the drug for which the subsection (b) application was
    submitted and for which the investigations described in clause
    (A) of subsection (b)(1) of this section and relied upon by the
    applicant for approval of the application were not conducted
    by or for the applicant and for which the applicant has not
    obtained a right of reference or use from the person by or for
    whom the investigations were conducted may be submitted
    under subsection (b) of this section before the expiration of
    five years from the date of the approval of the application
    under subsection (b) of this section, except that such an
    application may be submitted under subsection (b) of this
    section after the expiration of four years from the date of the
    approval of the subsection (b) application if it contains a
    certification of patent invalidity or noninfringement described
    in clause (iv) of subsection (b)(2)(A) of this section. The
    approval of such an application shall be made effective in
    accordance with this paragraph except that, if an action for
    patent infringement is commenced during the one-year period
    beginning forty-eight months after the date of the approval of
    the subsection (b) application, the thirty-month period
    referred to in subparagraph (C) shall be extended by such
    amount of time (if any) which is required for seven and one-
    half years to have elapsed from the date of approval of the
    subsection (b) application.
    (iii) If an application submitted under subsection (b) of this
    section for a drug, which includes an active ingredient
    (including any ester or salt of the active ingredient) that has
    been approved in another application approved under
    subsection (b) of this section, is approved after September 24,
    1984, and if such application contains reports of new clinical
    investigations (other than bioavailability studies) essential to
    the approval of the application and conducted or sponsored by
    the applicant, the Secretary may not make the approval of an
    application submitted under subsection (b) of this section for
    the conditions of approval of such drug in the approved
    subsection (b) application effective before the expiration of
    three years from the date of the approval of the application
    under subsection (b) of this section if the investigations
    described in clause (A) of subsection (b)(1) of this section and
    relied upon by the applicant for approval of the application
    were not conducted by or for the applicant and if the applicant
    has not obtained a right of reference or use from the person by
    or for whom the investigations were conducted.
    (iv) If a supplement to an application approved under
    subsection (b) of this section is approved after September 24,
    1984, and the supplement contains reports of new clinical
    investigations (other than bioavailability studies) essential to
    the approval of the supplement and conducted or sponsored
    by the person submitting the supplement, the Secretary may
    not make the approval of an application submitted under
    subsection (b) of this section for a change approved in the
    supplement effective before the expiration of three years from
    the date of the approval of the supplement under subsection
    (b) of this section if the investigations described in clause (A)
    of subsection (b)(1) of this section and relied upon by the
    applicant for approval of the application were not conducted
    by or for the applicant and if the applicant has not obtained a
    right of reference or use from the person by or for whom the
    investigations were conducted.