Case: 23-2254   Document: 118    Page: 1   Filed: 03/13/2025




    United States Court of Appeals
        for the Federal Circuit
                 ______________________

  MERCK SHARP & DOHME B.V., MERCK SHARP &
               DOHME, LLC,
              Plaintiffs-Appellees

                            v.

   AUROBINDO PHARMA USA, INC., AUROBINDO
   PHARMA LTD., USV PRIVATE LIMITED, GLAND
    PHARMA LIMITED, MANKIND PHARMA LTD.,
  LIFESTAR PHARMA LLC, FRESENIUS KABI USA,
    LLC, DR. REDDY'S LABORATORIES, INC., DR.
        REDDY'S LABORATORIES, LTD., SUN
     PHARMACEUTICAL INDUSTRIES, INC., SUN
     PHARMACEUTICAL INDUSTRIES LIMITED,
    SANDOZ INC., LEK PHARMACEUTICALS, D.D.,
  MYLAN API US LLC, MYLAN PHARMACEUTICALS
  INC., MYLAN INC., EUGIA PHARMA SPECIALTIES
                     LIMITED,
                Defendants-Appellants

   LUPIN LTD., LUPIN PHARMACEUTICALS, INC.,
    LUPIN INC., TEVA PHARMACEUTICALS USA,
                        INC.,
                      Defendants
                ______________________

                       2023-2254
                 ______________________

     Appeal from the United States District Court for the
 District of New Jersey in Nos. 2:20-cv-02576-CCC-LDW,
 2:20-cv-02750-CCC-MF, 2:20-cv-02751-CCC-MF, 2:20-cv-
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 2 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



 02786-CCC-MF, 2:20-cv-02787-CCC-MF, 2:20-cv-02892-
 CCC-MF, 2:20-cv-02909-CCC-MF, 2:20-cv-02964-CCC-MF,
 2:20-cv-03007-CCC-MF, 2:20-cv-03068-CCC-MF, 2:20-cv-
 03072-CCC-MF, 2:20-cv-03112-CCC-MF, 2:20-cv-03117-
 CCC-MF, 2:20-cv-03270-CCC-MF, 2:20-cv-03314-CCC-MF,
 2:20-cv-03795-CCC-MF, Judge Claire C. Cecchi.
                 ______________________

                Decided: March 13, 2025
                ______________________

     DAVID M. KRINSKY, Williams & Connolly LLP, Wash-
 ington, DC, argued for plaintiffs-appellees. Also repre-
 sented by STANLEY E. FISHER, SHAUN PATRICK MAHAFFY,
 ASHWIN SHANDILYA; SHAYNA S. COOK, ALAN ERNST
 LITTMANN, DOUG J. WINNARD, Goldman Ismail Tomaselli
 Brennan & Baum LLP, Chicago, IL; SARAH GEERS, Jones
 Day, New York, NY; ANTHONY INSOGNA, San Diego, CA;
 ANDREA WEISS JEFFRIES, Los Angeles, CA.

     ERIC THOMAS WERLINGER, Katten Muchin Rosenman
 LLP, Washington, DC, argued for all defendants-appel-
 lants. Defendants-appellants Mylan API US LLC, Mylan
 Pharmaceuticals Inc., Mylan Inc. also represented by
 TIMOTHY H. GRAY; JOSEPH JANUSZ, JITENDRA MALIK, Char-
 lotte, NC; DEEPRO MUKERJEE, LANCE SODERSTROM, New
 York, NY BRIAN SODIKOFF, Chicago, IL; MATTHEW
 GREINERT, Mylan, Canonsburg, PA.

     MAUREEN DONOVAN QUELER, Office of the Solicitor,
 United States Patent and Trademark Office, Alexandria,
 VA, argued for amicus curiae Coke Morgan Stewart. Also
 represented by SARAH E. CRAVEN, AMY J. NELSON,
 FARHEENA YASMEEN RASHEED.

     TIMOTHY H. KRATZ, Kratz & Barry LLP, Atlanta, GA,
 for defendants-appellants Aurobindo Pharma USA, Inc.,
 Aurobindo Pharma Ltd., Eugia Pharma Specialties
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 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.   3



 Limited. Also represented by GEORGE BARRY, III; MICHAEL
 PATRICK HOGAN, Philadelphia, PA; R TOUHEY MYER, Wil-
 mington, DE.

      ROBERT FLORENCE, Parker Poe Adams & Bernstein
 LLP, Atlanta, GA, for defendant-appellant USV Private
 Limited. Also represented by TASNEEM DHARAMSI, Green-
 ville, SC; ELIZABETH CROMPTON, Washington, DC.

     IMRON T. ALY, ArentFox Schiff LLP, Chicago, IL, for de-
 fendant-appellant Gland Pharma Limited. Also repre-
 sented by KEVIN MICHAEL NELSON; MATTHEW THOMAS
 WILKERSON.

    DMITRY SHELHOFF, Shelhoff Canfield & Chin LLC,
 Short Hills, NJ, for defendants-appellants Mankind
 Pharma Ltd., Lifestar Pharma LLC. Also represented by
 KENNETH CANFIELD; JULIA S. KIM, EDWARD D. PERGAMENT,
 Pergament & Cepeda LLP, Florham Park, NJ.

     BRIAN TIMOTHY BURGESS, Goodwin Procter LLP, Wash-
 ington, DC, for defendants-appellants Fresenius Kabi
 USA, LLC, Dr. Reddy's Laboratories, Inc., Dr. Reddy's La-
 boratories, Ltd., Sandoz Inc., Lek Pharmaceuticals, d.d.
 Also represented by NATASHA ELISE DAUGHTREY, Los An-
 geles, CA; WILLIAM EVANS, ROBERT FREDERICKSON, III,
 EMILY L. RAPALINO, DARYL L. WIESEN, Boston, MA.

     CHARLES B. KLEIN, Winston & Strawn LLP, Washing-
 ton, DC, for defendants-appellants Sun Pharmaceutical In-
 dustries, Inc., Sun Pharmaceutical Industries Limited.
 Also represented by JOVIAL WONG.
                   ______________________

      Before DYK, MAYER, and REYNA, Circuit Judges.
 DYK, Circuit Judge.
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 4 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



     This case concerns patent term extensions (“PTEs”) for
 reissued patents under the Hatch-Waxman Act. The
 Hatch-Waxman Act provides a process for extending pa-
 tent terms by up to five years to compensate patent owners
 for time lost during the lengthy regulatory review of new
 drug applications. See 

. The formula for
 calculating PTE is set forth in subsection 156(c), which pro-
 vides that “[t]he term of a patent . . . shall be extended by
 the time equal to the regulatory review period . . . oc-
 cur[ring] after the date the patent is issued.” 

 § 156(c)
 (emphasis added). The sole issue on appeal is whether PTE
 for a reissued patent should be calculated based on the is-
 sue date of the original patent or the reissued patent; in
 other words, whether the reference to “the patent” in sub-
 section 156(c) is to the original patent or the reissued pa-
 tent. Using the issue date of the reissued patent would
 usually result in shorter PTE because review that occurs
 before the issue date does not affect PTE.
     Here, the United States Patent and Trademark Office
 (“PTO”) granted an application for a five-year PTE for a re-
 issued patent, U.S. Patent No. RE44,733 (the
 “RE’733 patent”), based on the issue date of the original pa-
 tent, 

 (the “’340 patent). We hold
 that, in the context of reissued patents, the reference to
 “the patent” in subsection 156(c) is to the original patent.
 Here, the ’340 patent included claims directed to the active
 ingredient for a drug product (and the RE’733 patent re-
 tained those same claims). Under these circumstances, the
 RE’733 patent was entitled to a five-year PTE based on the
 ’340 patent’s issue date, since regulatory review effectively
 prevented the patent owner from enforcing the patent dur-
 ing that period. We thus affirm the district court’s holding
 that the PTO correctly calculated the RE’733 patent’s PTE.
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 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.   5



                        BACKGROUND
                              I
     The material facts of this case are not in dispute.
 Plaintiff-Appellee Merck 1 owned the ’340 patent, which is-
 sued on December 30, 2003. The ’340 patent was directed
 to a class of 6-mercapto-cyclodextrin derivatives. Claim 4
 is exemplary:
     A 6-mercapto-cyclodextrin derivative according to
     claim 1 selected from the group consisting of:
         6-per-deoxy-6-per-(2-carboxyethyl)thio-γ-cy-
         clodextrin;
         6-per-deoxy-6-per-(3-carboxypropyl)thio-γ-cy-
         clodextrin;
         6-per-deoxy-6-per-(4-carboxyphenyl)thio-γ-cy-
         clodextrin;
         6-per-deoxy-6-per-(4-carboxyphenylme-
         thyl)thio-γ-cyclodextrin;
         6-per-deoxy-6-per-(2-carboxypropyl)thio-γ-cy-
         clodextrin; and
         6-per-deoxy-6-per-(2-sulfoethyl)thio-γ-cy-
         clodextrin;
         or a pharmaceutically acceptable salt thereof.
 ’340 patent, col. 20 ll. 51–64 (emphasis added).      On
 April 13, 2004, four months after the ’340 patent issued,
 Merck applied to the Food and Drug Administration
 (“FDA”) for approval of 6-per-deoxy-6-per-(2-carboxy-
 ethyl)thio-γ-cyclodextrin (“sugammadex”). Sugammadex


     1   Throughout this opinion, “Merck” refers to Merck
 Sharp & Dohme B.V. and Merck Sharpe & Dohme LLC as
 well as their predecessors-in-interest.
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 6 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



 is the active ingredient in BRIDION®, a drug that is ad-
 ministered as an intravenous injection to reverse neuro-
 muscular blockade, a form of paralysis induced by
 rocuronium bromide and vecuronium bromide in certain
 types of surgery.
     While regulatory review was pending, Merck filed an
 application with the PTO to reissue the ’340 patent. The
 reissue application retained the original claims of the
 ’340 patent and included narrower claims directed specifi-
 cally to sugammadex. 2 On January 28, 2014, the ’340 pa-
 tent was reissued as the RE’733 patent, retaining the
 ’340 patent’s original claims and adding twelve additional,
 narrower claims relating to sugammadex. Claim 21 is ex-
 emplary of the new claims:
     A method for reversal of drug-induced neuromus-
     cular block in a subject, which comprises parenter-
     ally administering to said subject an effective
     amount of 6-per-deoxy-6-per-(2-carboxyethyl)thio-
     γ-cyclodextrin, sodium salt.
 RE’733 patent, col. 22 ll. 29–32. None of the ’340 patent’s
 nine original claims was cancelled.
     The regulatory review process continued until Decem-
 ber 15, 2015, when sugammadex was approved. Merck
 thus could not market sugammadex for nearly twelve years
 of the ’340 patent’s original term, which was set to expire
 on January 27, 2021. 3 On February 10, 2016, Merck filed



     2   Merck filed this application after this court clari-
 fied that the addition of narrower claims may constitute a
 proper basis for seeking reissue, see In re Tanaka, 

 (Fed. Cir. 2011).
     3   The ’340 patent’s application filing date was No-
 vember 23, 2000, corresponding to an original expiration
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 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.    7



 a PTE application for the RE’733 patent, seeking the max-
 imum five-year PTE based on the ’340 patent’s original is-
 sue date. On February 4, 2020, the PTO granted a five-
 year PTE to the RE’733 patent based on the ’340 patent’s
 original issue date: “Since the regulatory review period for
 BRIDION® began on April 13, 2004, which is after the De-
 cember 30, 2003[,] date of issuance for the ’340 patent, the
 entire regulatory review period has been considered in the
 above determination of the [PTE] length[.]” J.A. 6815. The
 RE’733 patent’s expiration date was accordingly shifted
 from January 27, 2021, to January 27, 2026.
                              II
     From January to March 2020, after the RE’733 patent
 reissued and around the time the FDA granted Merck’s
 PTE application, Defendants-Appellants (collectively “Au-
 robindo”) 4 filed Abbreviated New Drug Applications (“AN-
 DAs”) with the FDA to obtain approval to sell generic
 versions of BRIDION®. Aurobindo submitted a Para-
 graph IV         certification  under     21       U.S.C.



 date, without any extensions or adjustments, of Novem-
 ber 23, 2020. The patent received sixty-five days of patent
 term adjustment under 

(b) and was thus set
 to expire on January 27, 2021.
     4   Separate suits were brought against the other ap-
 pellants in the same district: Aurobindo Pharma USA, Inc.,
 Aurobindo Pharma, Ltd., and Eugia Pharma Specialties
 Ltd.; Gland Pharma Ltd.; Mankind Pharma Ltd. and
 Lifestar Pharma LLC; Mylan API US LLC, Mylan Phar-
 maceuticals Inc., and Mylan Inc.; Sandoz Inc., and Lek
 Pharmaceuticals d.d.; Sun Pharmaceutical Industries, Inc.
 and Sun Pharmaceutical Industries Ltd.; Fresenius Kabi
 USA, LLC; Dr. Reddy’s Laboratories, Inc., and Dr. Reddy’s
 Laboratories, Ltd.; and USV Private Ltd. These cases were
 consolidated.
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 8 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



 § 355(j)(2)(A)(vii)(IV) as to the RE’733 patent. A Para-
 graph IV certification allows an ANDA applicant to certify,
 to the best of its knowledge, that a patent that claims the
 brand-name drug or use for such drug is “invalid or will not
 be infringed by the manufacture, use, or sale of the new
 drug for which the application is submitted.” Id. In accord-
 ance with the patent statute, 

(e)(2)(A),
 Merck treated this filing as an act of infringement and
 brought suit.
     At trial, Aurobindo argued that the RE’733 patent was
 not entitled to a five-year PTE and had therefore expired.
 It argued that the PTO erred in calculating the
 RE’733 patent’s PTE based on the ’340 patent’s original is-
 sue date, urging that the plain text of subsection 156(c) re-
 quired the PTO to calculate PTE based on the issue date of
 “the patent” for which PTE was sought: the RE’733 patent.
 According to Aurobindo, the RE’733 patent was only enti-
 tled to a 686-day PTE (corresponding to an expiration date
 of December 14, 2022), since “only 686 days of the 4,265-
 day regulatory review period for BRIDION® ‘occur[red] af-
 ter the date the [RE’733] patent . . . issued.’” Defendants’
 Opening Brief on Their Patent Term Extension Invalidity
 Defense at 11, In re Sugammadex, 

 (D.N.J. June 13, 2023) (No. 20-cv-2576) (alterations in
 original) (quoting 

(c)).
     The district court disagreed, finding that Aurobindo’s
 construction of subsection 156(c) would undermine the
 purpose of the Hatch-Waxman Act. The district court con-
 cluded that section 156 should be read in light of 

, 252, and that “the patent” in subsection 156(c)
 must refer to the original patent, not the reissued patent.
 See In re Sugammadex, No. 20-cv-2576, 

,
 at *15–16 (D.N.J. June 13, 2023).          Based on this
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 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.    9



 construction, the district court held that the RE’733 patent
 was entitled to a five-year PTE. 5
     Aurobindo appealed. We have jurisdiction pursuant to
 

(a)(1). On January 19, 2024, the PTO filed
 an amicus brief in support of affirmance. We invited the
 PTO to present oral argument.
                        DISCUSSION
     Statutory construction is a question of law that is re-
 viewed de novo. Hawkins v. United States, 

 (Fed. Cir. 2006). Statutory construction begins “with
 the language of the statute itself,” United States v. Ron
 Pair Enters., Inc., 

 (1989), bearing in
 mind that “[s]tatutory language cannot be construed in a
 vacuum,” Sturgeon v. Frost, 

 (2016) (in-
 ternal citation and quotation marks omitted). The “[i]nter-
 pretation of a word or phrase depends upon reading the
 whole statutory text, considering the purpose and context.”
 Dolan v. U.S. Postal Serv., 

 (2006).
     The question on appeal is not, as the parties sometimes
 suggest, the meaning of the term “issue.” Aurobindo is
 clearly correct that the date the reissued patent issues is
 the date of reissue (here, January 28, 2014). Rather, this




     5   The district court held a one-day bench trial in
 which expert witnesses testified as to the practices of the
 PTO in granting PTEs for reissued patents for the purpose
 of establishing an agency practice that may be entitled to
 deference. Sugammadex, 

, at *2. This
 was improper, since agency practice is determined by ex-
 amining agency orders, not by the testimony of expert wit-
 nesses. Rumsfeld v. United Techs. Corp., 

 (Fed. Cir. 2003). This error has no impact on this ap-
 peal.
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  10 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



  case requires us to determine the meaning of the term “the
  patent” as used in subsection 156(c):
      The term of a patent eligible for extension under
      subsection (a) shall be extended by the time equal
      to the regulatory review period for the approved
      product which period occurs after the date the pa-
      tent is issued[.]
  

(c) (emphasis added).
      Aurobindo argues that, under the text’s plain meaning,
  “the patent” refers to the reissued patent, since “the ‘patent
  eligible for extension’ is the [reissued] patent.” Appellant’s
  Br. 23 (quoting 

(c)). This is because “the
  reissue[d] patent is distinct from the original patent[,]
  [and] the latter ceases to exist on the date the former is
  issued.” 

 (emphasis removed). Merck urges the
  opposite interpretation, arguing that subsection 156(c)’s
  “text, together with other patent statutes and the history
  of patent reissue, demonstrate that [subs]ection 156(c) re-
  fers to the original issue date.” Appellee’s Br. 17 (emphasis
  removed). We agree with Merck that the reference to “the
  patent” in subsection 156(c) refers to the original patent di-
  rected to a drug product. 6
      As the PTO points out, the language of subsec-
  tion 156(c) standing alone is ambiguous. It is unclear
  whether “the patent” refers to the original or reissued pa-
  tent. Because “[w]e cannot say that [this language] is alto-
  gether free of ambiguity,” we “consider statutory text and
  context together.” Caraco Pharm. Lab’ys, Ltd. v. Novo



      6   PTE is available for patents that contain drug
  product claims, method of using drug product claims, and
  method of manufacturing drug product claims. 

(b). This opinion collectively refers to these claims as
  claims “directed to a drug product.”
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  MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC. 11




  Nordisk A/S, 

 (2012); accord Chapman v.
  Hous. Welfare Rights Org., 

 (1979). The
  Supreme Court in Caraco provided important guidance for
  interpreting another provision of the Hatch-Waxman Act
  where, as here, the plain text of the statute was ambiguous.
      In Caraco, the Court considered the meaning of a pro-
  vision authorizing an ANDA applicant sued for patent in-
  fringement to bring a counterclaim “on the ground that the
  patent does not claim . . . an approved method of using the
  drug.” 

 (alteration in original) (quoting 

(j)(5)(C)(ii)(I)). The patentee urged that “not
  an” meant “not any,” such that an ANDA applicant could
  only bring this challenge if the patent did not claim any
  approved method of using the drug at all. See 

 The
  ANDA applicant urged that “not an” meant “not a particu-
  lar one,” such that this challenge was available if the pa-
  tent did not claim one of the methods of use for which the
  ANDA applicant sought to market the drug. See 

 Rec-
  ognizing that the meaning of “not an” was ambiguous, the
  Court looked to the broader “statutory context,” explaining
  that “Congress understood[] [that] a single drug may have
  multiple methods of use” and concluded that “[t]he statu-
  tory scheme . . . contemplates that one patented use will
  not foreclose marketing a generic drug for other unpat-
  ented ones.” 

 at 414–15. The Court concluded that “not
  an” must refer to “not a particular one” as suggested by the
  ANDA applicant because “[w]ithin [the Hatch-Waxman
  Act’s] framework, the counterclaim naturally functions to
  challenge the brand’s assertion of rights over whichever
  discrete use (or uses) the generic company wishes to pur-
  sue.” 

. This was “because Congress meant (as it
  usually does) for the provision it enacted to fit within the
  statutory scheme.” 

.
      So, too, here, we must interpret the term “the patent”
  with reference to “the specific context in which that lan-
  guage is used, and the broader context of the statute as a
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  12 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



  whole.” Robinson v. Shell Oil Co., 

 (1997);
  see also Dep’t of Homeland Sec. v. MacLean, 

,
  393 (2015) (rejecting an interpretation that “could defeat
  the purpose of the . . . statute”); Centripetal Networks, Inc.
  v. Cisco Sys., Inc., 

 (Fed. Cir. 2022) (ex-
  plaining that in interpreting a statute, we “look to the pro-
  visions of the whole law, and [] its object and policy”
  (quoting Dole v. United Steelworkers of Am., 

 (1990)).
      While Congress does not appear to have contemplated
  the situation presented by reissued patents in drafting sec-
  tion 156, the purpose of the section is clear: to compensate
  pharmaceutical companies for the effective truncation of
  their patent terms while waiting for regulatory approval of
  new drug applications. See H.R. Rep. No. 98-857, pt. 1,
  at 15 (1984) (stating that the purpose of PTE is to “create
  a new incentive for increased expenditures for research
  and development,” where “[t]he incentive is the restoration
  of some of the time lost on patent life while the patent is
  awaiting pre-market approval” (emphasis added)); Drug
  Price Competition and Patent Term Restoration Act of
  1984: Hearing on S. 2748 Before the S. Comm. on Lab. &
  Hum. Res. of the U.S. Senate at 2, 98th Cong. 1102 (1984)
  (statement of Sen. Orrin Hatch) (“The added research and
  development will flow from added patent protection which
  will compensate the research drug companies for the years
  of exclusive marketing time under their patents lost be-
  cause of the lengthy FDA testing and review period.”).
      We have recognized that the purpose of the Hatch-
  Waxman Act is to “provid[e] patent holders with limited
  extensions of patent term in order to recover a portion of
  the market exclusivity lost during the lengthy process of
  development and FDA review.” Glaxo, Inc. v. Novopharm,
  Ltd., 

 (Fed. Cir. 1997); see also Merck
  & Co. v. Hi-Tech Pharmacal Co., 

  (Fed. Cir. 2007); PhotoCure ASA v. Kappos, 

,
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  MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC. 13




  1374 (Fed. Cir. 2010). In particular, “[t]he statute contem-
  plates a patentee receiving time lost in its patent term by
  reason of FDA delay, and the statute should be liberally
  interpreted to achieve this end.” Merck & Co. v. Kessler,
  

 (Fed. Cir. 1996).
      We conclude that, in the context of reissued patents,
  the Hatch-Waxman Act contemplates PTE for those pa-
  tents and only those patents with claims directed to drug
  products whose period of exclusivity was delayed by FDA
  review. 7 That purpose applies in this case, since constru-
  ing “the patent” in subsection 156(c) as the original patent
  compensates Merck for the period of exclusivity lost due to
  regulatory delay. On the other hand, Aurobindo’s construc-
  tion denies Merck compensation for all but a small period
  of the delay. There is no reason why the Hatch-Waxman
  Act’s purpose would be served by disabling extensions of
  the unexpired term solely based on a patent holder’s deci-
  sion to seek reissue, and Aurobindo offers none. 8
      Aurobindo, however, urges that “the patent” cannot re-
  fer to the original patent because the original patent is



      7   We note that the Hatch-Waxman Act was passed
  prior to the Uruguay Round Agreements Act, so the pa-
  tent’s expiration date was based on the issue date rather
  than the filing date. This does not change our analysis,
  since any period of regulatory review that occurs after the
  patent’s issue date still disables the patent owner from
  commercially marketing the drug product during the life-
  time of the patent.
      8   At oral argument, when asked why Congress would
  intend for a patent owner to lose PTE simply by seeking
  reissue, counsel for the defendants replied: “If the text is
  plain that’s it. There might be policy reasons for why the
  statute might have been written differently, but that is for
  Congress to determine.” Oral Arg. at 2:01–08.
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  14 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



  “dead” upon reissue. Appellant’s Br. 26 (quoting Seattle
  Box Co. v. Indus. Crating & Packing, 

  (Fed. Cir. 1984)); see also Eby v. King, 

  (1895) (holding that a patent owner may not rely on the
  original patent after the reissued patent is declared void
  because the original patent “is extinguished” (quoting Peck
  v. Collins, 

 (1880)); Moffitt v. Garr,
  

, 282–83 (1861) (holding that a suit for infringe-
  ment of the original patent brought before the issuance of
  the reissued patent must “fail” because “[a] surrender of
  the patent [for reissue] . . . extinguishes the patent”). But
  whether the holder of the reissued patent has an enforcea-
  ble right in the original patent’s claims is irrelevant, since
  the reissued patent inherits “the unexpired part of the term
  of the original patent,” 

(a), which now un-
  ambiguously “begin[s] on the date on which the patent is-
  sues and end[s] 20 years from the date on which the
  application for the patent was filed,” 

 § 154(a)(2), subject
  to patent term adjustment (not at issue in this case). Sec-
  tion 156 is designed to extend the term of the original pa-
  tent, not to make the original patent enforceable after
  reissue. We have explained that a “reissue patent does not
  simply replace an original patent nunc pro tunc.” Intel
  Corp. v. Negotiated Data Sols., Inc., 

  (Fed. Cir. 2012). We accordingly conclude that Aurobindo’s
  argument is foreclosed by the both the purpose of sec-
  tion 156 and related statutory context.
      The only construction that comports with the purpose
  of the Hatch-Waxman Act is one that extends PTE to pa-
  tent owners who were actually disabled from benefiting
  from patent protection during the pendency of regulatory
  review. We thus conclude that, in the context of reissued
  patents, “the patent” in subsection 156(c) refers to the orig-
  inal patent. A reissued patent is entitled to PTE based on
  the original patent’s issue date where, as here, the original
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  MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC. 15




  patent included the same claims directed to a drug product
  subject to FDA review. 9



      9    We do not find the parties’ reliance on section 251
  to be helpful, since it does not shed any light on the mean-
  ing of the term “the patent.” We are also not persuaded by
  Merck’s reliance on language in section 252 providing that
  that “every reissued patent shall have the same effect and
  operation in law, on the trial of actions for causes thereaf-
  ter arising, as if the same had been originally granted in
  such amended form.” According to Merck, the “point of this
  clause” is to “backdat[e] reissued patents to the original pa-
  tent date for assessing litigation defenses.” Appellee’s
  Br. 31.
       While we agree that section 252 applies to assessing
  litigation defenses, we think the more plausible reading of
  section 252 is to backdate reissued patents to the original
  priority dates and critical dates of the original patents for
  the purpose of assessing defenses such as anticipation and
  obviousness. See Fresenius USA, Inc. v. Baxter Int’l, Inc.,
  

 (Fed. Cir. 2013) (“[T]his change was
  meant ‘simply to correct an almost unbelievable and ineq-
  uitable situation. . . . [that] if a patentee applies for a reis-
  sue, no matter for what purpose, all rights he had in and
  under the original patent are forfeited ab initio upon the
  grant of the reissue.’” (quoting S. Rep. No. 71-567, at 1)).
       Merck’s reliance on language that provides that reis-
  sued claims that are “substantially identical” to the claims
  in an originally patent “shall . . . have effect continuously
  from the date of the original patent” is similarly misplaced.
  The purpose of this provision is to clarify that a patent
  owner cannot enforce reissued claims before the reissued
  patent issues unless those claims are substantially identi-
  cal to the original patent’s claims. See Seattle Box,
  

 (“Congress, in this statute, has explicitly
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  16 MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC.



      Our reading of subsection 156(c) is further confirmed
  by other statutory provisions of the Patent Act. Subsec-
  tion 156(a) provides that “the term of a patent . . . shall be
  extended . . . from the original expiration date of the pa-
  tent.” 35 U.S.C § 156(a) (emphasis added). The most nat-
  ural reading of this language is that “the patent” must be
  the original patent, since the “original expiration date” is
  tied to the filing date of the original patent, not the reissued
  patent. Subsection 154(a)(2) now provides that a patent’s
  term “begin[s] on the date on which the patent issues and
  end[s] 20 years from the date on which the application for
  the patent was filed.” The reference to “the patent” here
  must be to the original patent, not the reissued patent,
  which inherits the original patent term. 10
      While not binding, we note that the PTO has also re-
  vised its Manual of Patent Examining Procedure in a man-
  ner that substantially tracks with our analysis as applied
  in this case. It has been revised to provide that “[w]ith re-
  spect to calculating the amount of extension to which the
  reissued patent is entitled to receive, so long as the original
  patent claimed the approved product and the reissued pa-
  tent claims the approved product, the original patent grant
  date would be used to calculate the extension to which the
  reissued patent would be entitled.” MPEP § 2766. This


  limited claim continuity to claims in the reissued patent
  identical to claims in the original patent.”) We find no ba-
  sis to conclude that Congress intended for this provision to
  apply outside the context of backdating priority dates.
       10  If the original patent included claims directed to a
  drug product subject to regulatory review and the patent
  owner subsequently cancels those claims, section 156 of
  course would not apply, whether the cancellation occurred
  before or after regulatory review. This is because cancelled
  claims are treated as void ab initio. Fresenius, 

.
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  MERCK SHARP & DOHME B.V. v. AUROBINDO PHARMA USA, INC. 17




  comports with the statutory scheme of the Hatch-Waxman
  Act, which is to award PTE only in those circumstances in
  which the patent owner is prevented from enjoying patent
  protection because of the pendency of regulatory review. 11
                         CONCLUSION
      We conclude that in the context of reissued patents,
  “the patent” in subsection 156(c) refers to the original pa-
  tent that includes claims that are directed to a drug prod-
  uct. Because the ’340 patent included claims directed to
  sugammadex and was issued before FDA approval of
  BRIDION®, we agree with the district court that the
  RE’733 reissue patent was entitled to the five-year PTE
  based on the ’340 patent’s issue date.
                         AFFIRMED




      11  Difficult questions arise in cases where the original
  patent did not include any claims directed to the drug prod-
  uct and was later reissued to include broader claims di-
  rected to such products. In such cases, a patent owner may
  or may not have had the opportunity to enforce the patent
  during review depending on whether the reissued patent
  was issued before or after regulatory review. Those ques-
  tions are not presented by this case.