Court Opinion

ID: 6324246
Source: CourtListenerOpinion
Date Created: 2022-03-17 16:01:33.95142+00
Date Added: 2024-06-11T09:21:50.574380
License: Public Domain

Case: 20-1933   Document: 89     Page: 1   Filed: 03/16/2022

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

   BIOGEN INTERNATIONAL GMBH, BIOGEN MA,
                      INC.,
              Plaintiffs-Appellants

                            v.

         MYLAN PHARMACEUTICALS INC.,
                Defendant-Appellee
              ______________________

                       2020-1933
                 ______________________

    Appeal from the United States District Court for the
 Northern District of West Virginia in No. 1:17-cv-00116-
 IMK-JPM, Judge Irene M. Keeley.
                 ______________________

    ON PETITION FOR PANEL REHEARING AND
             REHEARING EN BANC
              ______________________

     WILLIAM F. LEE, Wilmer Cutler Pickering Hale and
 Dorr LLP, Boston, MA, filed a petition for panel rehearing
 and rehearing en banc for plaintiffs-appellants.      Also
 repre-sented by ANNALEIGH E. CURTIS, MADELEINE C.
 LAUPHEIMER, LISA JON PIROZZOLO; SCOTT G. GREENE, New
 York, NY; THOMAS SAUNDERS, Washington, DC; PAUL
 WILLIAM BROWNING, J. MICHAEL JAKES, JAMES B. MONROE,
 JASON LEE ROMRELL, Finnegan, Henderson, Farabow, Gar-
 rett & Dunner, LLP, Washington, DC.
Case: 20-1933      Document: 89    Page: 2   Filed: 03/16/2022

 2                             BIOGEN INTERNATIONAL GMBH v.
                                 MYLAN PHARMACEUTICALS INC.

     NATHAN K. KELLEY, Perkins Coie LLP, Washington,
 DC, filed a response to the petition for defendant-appellee.
 Also represented by SHANNON BLOODWORTH, BRANDON
 MICHAEL WHITE; DAVID LEE ANSTAETT, ANDREW
 DUFRESNE, EMILY JANE GREB, Madison, WI; DAN L.
 BAGATELL, Hanover, NH; MATTHEW GREINERT, Viatris Inc.,
 Canonsburg, PA.

     HA KUNG WONG, Venable LLP, New York, NY, for ami-
 cus curiae Biotechnology Innovation Organization. Also
 represented by KATHERINE ADAMS.

     JAMES C. CARVER, The Carver Law Firm, Baton Rouge,
 LA, for amicus curiae Chemistry and The Law Division of
 the American Chemical Society.

     JEFFREY PAUL KUSHAN, Sidley Austin LLP, Washing-
 ton, DC, for amicus curiae Pharmaceutical Research and
 Manufacturers of America. Also represented by MARY T.
 HANNON, STEVEN J. HOROWITZ, Chicago, IL; DAVID EVAN
 KORN, Pharmaceutical Research and Manufacturers of
 America, Washington, DC.
                 ______________________

   Before MOORE, Chief Judge, NEWMAN, LOURIE, DYK,
 PROST, O’MALLEY, 1 REYNA, TARANTO, CHEN, and HUGHES,
                     Circuit Judges. *
     LOURIE, Circuit Judge, with whom MOORE, Chief Judge,
     and NEWMAN, Circuit Judge, join, dissents from the de-
           nial of the petition for rehearing en banc.

       1 Circuit Judge O’Malley retired on March 11, 2022,
 and participated only in the decision on the petition for
 panel rehearing.
     *   Circuit Judge Stoll and Circuit Judge Cunningham
 did not participate.
Case: 20-1933     Document: 89    Page: 3    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                              3
 MYLAN PHARMACEUTICALS. INC.

  PER CURIAM.
                         ORDER
     Biogen International BmbH and Biogen MA, Inc. filed
 a combined petition for panel rehearing and rehearing en
 banc. A response to the petition was invited by the court
 and filed by Mylan Pharmaceuticals Inc. The court also ac-
 cepted amicus briefs filed by Biotechnology Innovation Or-
 ganization, Chemistry and The Law Division of the
 American Chemical Society, and Pharmaceutical Research
 and Manufacturers of America. The petition was referred
 to the panel that heard the appeal, and thereafter the peti-
 tion was referred to the circuit judges who are in regular
 active service. The court conducted a poll on request, and
 the poll failed.
    Upon consideration thereof,
    IT IS ORDERED THAT:
    The petition for panel rehearing is denied.
    The petition for rehearing en banc is denied.
    The mandate of the court will issue on March 23, 2022.

                                    FOR THE COURT

 March 16, 2022                     /s/ Peter R. Marksteiner
     Date                           Peter R. Marksteiner
                                    Clerk of Court
Case: 20-1933    Document: 89      Page: 4    Filed: 03/16/2022

   United States Court of Appeals
       for the Federal Circuit
                   ______________________

   BIOGEN INTERNATIONAL GMBH, BIOGEN MA,
                      INC.,
              Plaintiffs-Appellants

                              v.

          MYLAN PHARMACEUTICALS INC.,
                 Defendant-Appellee
               ______________________

                         2020-1933
                   ______________________

    Appeal from the United States District Court for the
 Northern District of West Virginia in No. 1:17-cv-00116-
 IMK-JPM, Judge Irene M. Keeley.
                 ______________________
 LOURIE, Circuit Judge, with whom MOORE, Chief Judge,
 and NEWMAN, Circuit Judge, join, dissenting from the de-
 nial of the petition for rehearing en banc.
     On March 2, 2010, this court sitting en banc in Ariad
 Pharms., Inc. v. Eli Lilly & Co., reaffirmed the proposition
 that “written description” is a requirement that exists in
 the patent statute separate and apart from any other re-
 quirements for patentability. 598 F.3d 1336, 1351 (Fed.
 Cir. 2010). We stated very clearly that “the hallmark of
 written description is disclosure.” Id. The test for written
 description “requires an objective inquiry into the four cor-
 ners of the specification from the perspective of a person of
 ordinary skill in the art.” Id. “Based on that inquiry”—
 and not based on other considerations—“the specification
Case: 20-1933    Document: 89        Page: 5   Filed: 03/16/2022

2                                  BIOGEN INTERNATIONAL GMBH
                              v.   MYLAN PHARMACEUTICALS INC.

 must describe an invention understandable to that skilled
 artisan and show that the inventor actually invented the
 invention claimed.” Id.
     We have found lack of written description in a variety
 of contexts and circumstances. For example, we found a
 lack of written description when a patent specification de-
 scribed only rat insulin-encoding cDNA but the claimed mi-
 croorganism encompassed human insulin-encoding CDNA.
 See Regents of Univ. of Cal. v. Eli Lilly & Co., 119 F.3d
 1559, 1568 (Fed. Cir. 1997). We found a lack of written
 description when a patent specification identified only one
 possible location for controls on a reclining sofa but the
 claim recited the controls in a different location. See Gen-
 try Gallery, Inc. v. Berkline Corp., 134 F.3d 1473, 1479–80
 (Fed. Cir. 1998). In another case, we found a lack of written
 description when claims were directed to a method com-
 prising administering a compound to achieve a particular
 result but the specification failed to disclose any com-
 pounds that could be used in the claimed method. See
 Univ. of Rochester v. G.D. Searle & Co., 358 F.3d 916, 927
 (Fed. Cir. 2004). We also found a lack of written descrip-
 tion when a specification disclosed small numbers of spe-
 cies of antibodies that did not reasonably represent the
 breadth of antibodies encompassed by the claimed genus.
 See Abbvie Deutschland GmbH & Co. v. Janssen Biotech,
 Inc., 759 F.3d 1285, 1300–01 (Fed. Cir. 2014).
     These decisions, and many more like them, are sup-
 ported by case law dating back to before this court existed.
 See, e.g., In re Ruschig, 379 F.2d 990, 995 (C.C.P.A. 1967)
 (finding that the claimed compound was not described in
 the specification). Indeed, these decisions are supported by
 Supreme Court precedent dating back almost two centuries
 when the Court found that Samuel Morse’s eighth patent
 claim was invalid because “he claims an exclusive right to
 use a manner and process which he has not described and
 indeed had not invented, and therefore could not describe
Case: 20-1933     Document: 89     Page: 6    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                     3
 MYLAN PHARMACEUTICALS INC.

 when he obtained his patent.” See O’Reilly v. Morse, 56
 U.S. 62, 113 (1853).
     But in all that history, this case, in which every claim
 limitation is expressly described in the disclosure of the pa-
 tent specification, is at the farthest end of the spectrum of
 cases where written description has not been found. It is
 an outlier.
     Today, by denying rehearing en banc, the judges of this
 court have let a panel majority opinion stand that imports
 extraneous considerations into the written description
 analysis and blurs the boundaries between the written de-
 scription requirement and the other statutory require-
 ments for patentability. In doing so, the court has
 contributed to the muddying of the written description re-
 quirement. Accordingly, I respectfully dissent from that
 denial.
                               I
     Biogen International GmbH (“Biogen”) owns U.S. Pa-
 tent 8,399,514 (“the ’514 patent”). Mylan Pharmaceuticals
 Inc. (“Mylan”) contended that the claims of the ’514 patent
 are invalid for lack of written description support in the
 specification. In asserting that challenge, Mylan bore the
 burden of proving by clear and convincing evidence that the
 disclosure of the ’514 patent specification failed to demon-
 strate to a person of ordinary skill in the art that the in-
 ventors invented what is claimed. The district court found
 that Mylan met its burden. Biogen Int’l GmbH v. Mylan
 Pharms. Inc., No. 1:17-cv-116, 2020 WL 3317105 (N.D. W.
 Va. June 18, 2020) (“District Court Decision”). The panel
 majority affirmed. See Biogen Int’l GMBH v. Mylan
 Pharms. Inc., 18 F.4th 1333 (Fed. Cir. 2021) (“Panel Maj.
 Op.”). I begin by explaining why it should have reversed
 and why this court should have granted the petition for re-
 hearing en banc.
     Claim 1 of the ’514 patent recites:
Case: 20-1933     Document: 89        Page: 7   Filed: 03/16/2022

4                                   BIOGEN INTERNATIONAL GMBH
                               v.   MYLAN PHARMACEUTICALS INC.

     A method of treating a subject in need of treatment
     for multiple sclerosis comprising orally administer-
     ing to the subject in need thereof a pharmaceutical
     composition consisting essentially of (a) a thera-
     peutically effective amount of dimethyl fumarate,
     monomethyl fumarate, 1 or a combination thereof,
     and (b) one or more pharmaceutically acceptable
     excipients, wherein the therapeutically effective
     amount of dimethyl fumarate, monomethyl
     fumarate, or a combination thereof is about 480 mg
     per day.
 ’514 patent at col. 27 ll. 59–67.
      In evaluating whether the written description require-
 ment has been met with respect to claim 1, we must look to
 what is disclosed in the patent specification. See, e.g., D
 Three Enters., LLC v. SunModo Corp., 890 F.3d 1042, 1052
 (Fed. Cir. 2018) (“[A]dequate written description . . . asks
 what is disclosed.”); Ariad, 598 F.3d at 1351 (“[T]he hall-
 mark of written description is disclosure.”). The ’514 pa-
 tent sets forth a number of embodiments, including five
 methods. Most relevant here, “method 4” includes “meth-
 ods of treating a neurological disease.” ’514 patent at col. 8
 ll. 35–36. And, pointedly, the title of the patent is “Treat-
 ment for Multiple Sclerosis.”
      Accordingly, the specification explicitly states that the
 neurological disease in method 4 “can [] be multiple sclero-
 sis (MS).” See id. at col. 16 ll. 18–22. This disclosure is
 consistent with the background section of the patent, which
 begins with a specific discussion of multiple sclerosis. The
 first sentence of the disclosure states:

     1   Dimethyl fumarate and monomethyl fumarate are
 often abbreviated as “DMF” and “MMF.”
Case: 20-1933     Document: 89     Page: 8    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                     5
 MYLAN PHARMACEUTICALS INC.

     Provided are certain compounds for treating neu-
     rological diseases, including demyelinating neuro-
     logical diseases, such as, e.g., multiple sclerosis.
 Id. at col. 1 ll. 12–14. The specification then proceeds to
 describe the pathology, symptoms, and available treat-
 ments for multiple sclerosis. Id. at col. 1 ll. 15–52. Viewed
 from any perspective, including that of a person of ordinary
 skill in the art, the ’514 patent describes the invention of a
 method for treating multiple sclerosis.
      Included within method 4 of the specification are meth-
 ods that comprise “administering to the subject in need
 thereof at least one compound that is [] structurally similar
 to DMF and/or MMF.” Id. at col. 8 ll. 36–38. The patent
 notes that the methods comprise administering “a thera-
 peutically effective amount of at least one neuroprotective
 compound which has Formula I, II, III, or IV, e.g., a fu-
 maric acid derivative (e.g., DMF or MMF).” Id. at col. 8
 ll. 42–44. And the specification provides details about
 what constitutes an effective amount of DMF or MMF, not-
 ing that effective doses may vary depending on a number
 of factors, and providing examples of effective doses:
     For example, an effective dose of DMF or MM[F] to
     be administered to a subject orally can be from
     about 0.1 g to 1 g per day, 200 mg to about 800 mg
     per day (e.g., from about 240 mg to about 720 mg
     per day; or from about 480 mg to about 720 mg
     per day; or about 720 mg per day).
 Id. at col. 18 ll. 58–62 (emphasis added).
      To summarize, claim 1 is directed to a method of treat-
 ing a particular disease (multiple sclerosis) by administer-
 ing particular compounds (DMF or MMF) at a particular
 dose (480 mg per day). And that is precisely what the spec-
 ification discloses—treatment of multiple sclerosis with a
 480 mg per day dose of DMF or MMF. Thus, the specifica-
 tion provides sufficient written description under 35 U.S.C.
Case: 20-1933     Document: 89        Page: 9   Filed: 03/16/2022

6                                   BIOGEN INTERNATIONAL GMBH
                              v.    MYLAN PHARMACEUTICALS INC.

 § 112. Whatever shortcomings exist in this unfocused pa-
 tent specification, failure of written description with re-
 spect to claim 1 is not one of them.
                               II
      Both the panel majority and the district court began
 their analyses by correctly recognizing that “it is the spec-
 ification itself that must demonstrate possession” of the
 claimed invention. See Panel Maj. Op., 18 F.4th at 1342
 (quoting the district court). Yet, despite the clear written
 description support in the specification itself, neither the
 panel majority nor the district court resolved the written
 description inquiry in favor of the patentee, Biogen. It is
 thus important to explain what I believe are the errors
 made by the panel majority and the district court.
      As a general matter, the panel majority and the district
 court erred by analyzing factual and legal considerations
 that are not properly contained within the written descrip-
 tion analysis. More specifically, I identify four individual
 points of error that the en banc court should have cor-
 rected. First, the panel majority and the district court
 overly emphasized unclaimed disclosures in the specifica-
 tion. Second, they erroneously imposed a heightened bur-
 den on the patentee to show that the specification proves
 efficacy. Third, they imported legal factors from other pa-
 tentability requirements. And fourth, they were influenced
 by irrelevant extrinsic evidence. I will address each of
 these points of error in turn.
                               A
     The first point of error is the undue emphasis that the
 panel majority and the district court placed on unclaimed
 disclosures in the specification. Although they acknowl-
 edged that the subject matter of the claims—treatment of
 multiple sclerosis with 480 mg per day of DMF or MMF—
 was, in fact, disclosed in the patent specification, the panel
 majority and the district court engaged in irrelevant
Case: 20-1933    Document: 89      Page: 10     Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                      7
 MYLAN PHARMACEUTICALS INC.

 comparisons between the amount of disclosure of the
 claimed subject matter versus the unclaimed subject mat-
 ter.
      For example, while conceding that “MS may arguably
 constitute an important element of the disclosure from the
 start,” the panel majority focused on the fact that the spec-
 ification “covers a broad array of nearly three dozen neuro-
 logical disorders.” Panel Maj. Op., 18 F.4th at 1342; see
 also District Court Decision, 2020 WL 3317105, at *10 (“MS
 is merely one such disease ‘among a slew of competing pos-
 sibilities.’”). As another example, the panel majority em-
 phasized that the 480 mg per day dose “is listed only once
 in the entire specification,” finding this to be “a significant
 fact that cuts against Biogen’s case.” Panel Maj. Op. 18
 F.4th at 1343; see also District Court Decision, 2020 WL
 3317105, at *10 (noting that column 18 is “the only part of
 the specification that mentions 480 mg/day of DMF”). The
 panel majority contrasted this one express disclosure of
 480 mg per day with the “series of ranges” disclosed in the
 specification, noting that the 480 mg dose “appears at the
 end of one range.” Panel Maj. Op. 18 F.4th at 1343.
     As Judge O’Malley’s panel dissent noted, the district
 court justified its focus on unclaimed subject matter by
 looking to our precedent requiring that a specification con-
 tain “blaze marks” that point a person of ordinary skill to
 the claimed species of a disclosed genus. See 18 F.4th at
 1350–51 (O’Malley, J., dissenting). Blaze mark analysis
 originated in In re Ruschig, where, unlike here, the speci-
 fication failed to disclose a claimed species within a dis-
 closed genus. See 379 F.2d 990, 994–95 (C.C.P.A. 1967).
 Although Biogen argued that the district court misapplied
 that blaze mark precedent, the panel majority dismissed
 that concern as “superfluous.” Panel Maj. Op., 18 F.4th at
 1345.
     This court has developed a body of precedent to govern
 the genus/species relationship in the context of the written
Case: 20-1933     Document: 89       Page: 11   Filed: 03/16/2022

 8                                  BIOGEN INTERNATIONAL GMBH
                               v.   MYLAN PHARMACEUTICALS INC.

 description requirement of 35 U.S.C. § 112. In cases in-
 volving claims to a genus, “a sufficient description of a ge-
 nus [] requires the disclosure of either a representative
 number of species falling within the scope of the genus or
 structural features common to members of the genus so
 that one of skill in the art can ‘visualize or recognize’ the
 members of the genus.” Ariad, 598 F.3d at 1350 (quoting
 Regents of the Univ. of Cal. v. Eli Lilly & Co., 119 F.3d
 1559, 1568–69 (Fed. Cir. 1997)). On the other hand, “[i]n
 cases where the specification describes a broad genus and
 the claims are directed to a single species or a narrow sub-
 genus, we have held that the specification must contain
 ‘“blaze marks” that would lead an ordinarily skilled inves-
 tigator toward such a species among a slew of competing
 possibilities.’”    Novartis Pharms. Corp. v. Accord
 Healthcare, Inc., 21 F.4th 1362, 1370 (Fed. Cir. 2022) (quot-
 ing Novozymes A/S v. DuPont Nutrition Biosciences APS,
 723 F.3d 1336, 1349 (Fed. Cir. 2013)).
     As we recently clarified in Novartis, however, “‘[b]laze
 marks’ are not necessary where the claimed species is ex-
 pressly described in the specification.” Id. Such is the case
 here. The ’514 patent does not merely disclose the genus
 “neurological diseases” without reference to the claimed
 species “multiple sclerosis.” Rather, the patent expressly
 states that the neurological disease in method 4 can be
 “multiple sclerosis.” ’514 patent at col. 16 ll. 18–21; see also
 id. at col. 16 l. 44 (listing additional neurological diseases
 “in addition to MS”). Similarly, with respect to doses, the
 patent explicitly includes “480 mg per day” as an end point
 of a limited number of dose ranges. Id. at col. 18 ll. 52–64.
     In this case, where the claimed species—i.e., “multiple
 sclerosis” within the genus “neurological diseases”—is ex-
 pressly described in the specification, the written descrip-
 tion requirement is satisfied regardless of the
 specification’s additional disclosure of other unclaimed
 neurological diseases. See Scriptpro, LLC v. Innovation As-
 socs., Inc., 762 F.3d 1355, 1359 (Fed. Cir. 2014) (“It is
Case: 20-1933    Document: 89      Page: 12    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                     9
 MYLAN PHARMACEUTICALS INC.

 common, and often permissible, for particular claims to
 pick out a subset of the full range of described features,
 omitting others.”). Moreover, written description support
 for the claimed 480 mg per day dose is not undermined by
 the fact that it only appears one time in the specification or
 by the fact that the patent also discloses unclaimed dose
 ranges. See Vanda Pharms. Inc. v. W.-Ward Pharms. Int’l
 Ltd., 887 F.3d 1117, 1137 (Fed. Cir. 2018) (“The disclosure
 of a dose outside of the claimed range does not compel a
 finding that the asserted claims lack adequate written de-
 scription.”). Once is enough.
     The panel majority opinion implies that a patent fails
 the written description requirement of 35 U.S.C. § 112
 when it contains too much disclosure beyond the claimed
 invention, which is incorrect. The opinion implies that a
 patentee must disclose the claimed subject matter more
 than once, which is also incorrect. And the opinion implies
 that a court may arbitrarily count the number of times the
 claimed subject matter is disclosed in the specification rel-
 ative to the number of times unclaimed subject matter is
 disclosed, which is incorrect. The en banc court should
 have intervened to correct these incorrect propositions.
                               B
     The second point of error is the panel majority’s erro-
 neous imposition of a burden of proof on the patentee to
 show that the specification proves the efficacy of the
 claimed pharmaceutical composition. Under our prece-
 dent, “it is unnecessary to prove that a claimed pharma-
 ceutical compound actually achieves a certain result.”
 Nuvo Pharms. (Ir.) Designated Activity Co. v. Dr. Reddy’s
 Lab’ys Inc., 923 F.3d 1368, 1384 (Fed. Cir. 2019). That is
 the province of the United States Food and Drug Admin-
 istration. See In re Brana, 51 F.3d 1560, 1567 (Fed. Cir.
 1995) (delineating between “the requirements under the
 law for obtaining a patent with the requirements for ob-
 taining government approval to market a particular drug
Case: 20-1933    Document: 89       Page: 13   Filed: 03/16/2022

 10                                BIOGEN INTERNATIONAL GMBH
                              v.   MYLAN PHARMACEUTICALS INC.

 for human consumption”); see also Scott v. Finney, 34 F.3d
 1058, 1063 (Fed. Cir. 1994) (“Testing for the full safety and
 effectiveness of a prosthetic device is more properly left to
 the Food and Drug Administration (FDA). Title 35 does
 not demand that such human testing occur within the con-
 fines of Patent and Trademark Office (PTO) proceedings.”).
 Yet the panel majority affirmed the district court’s decision
 that the patent fails the written description requirement
 because “nothing in [the specification] teaches a [person of
 ordinary skill in the art] that a 480 mg/day dose of DMF []
 is therapeutically effective for treating MS.” District Court
 Decision, 2020 WL 3317105, at *11; see also Panel Maj. Op.,
 18 F.4th at 1343–44 (“What matters for purposes of the in-
 quiry in this case is whether, at the time of filing the dis-
 closure, . . . a skilled artisan could deduce simply from
 reading the specification that DMF480 would be a thera-
 peutically effective treatment for MS.”).
      The claims specify precisely the amount that they
 claim would be “therapeutically effective,” namely, “480 mg
 per day.” ’514 patent col. 27 ll. 65–67. And the patent spec-
 ification leaves nothing for the skilled artisan to deduce; it
 expressly states that 480 mg per day is an effective
 amount.
                               C
     The third point of error is the panel majority’s impor-
 tation of extraneous legal considerations into the written
 description analysis. In Ariad, we stated that the first par-
 agraph of 35 U.S.C. § 112 “contains two separate descrip-
 tion requirements: a ‘written description [i] of the
 invention, and [ii] of the manner and process of making and
 using [the invention].” Ariad, 598 F.3d at 1344 (quoting 35
 U.S.C. § 112, emphasis and brackets original). The panel
 majority’s focus on the efficacy of the claimed pharmaceu-
 tical composition runs afoul of that precedent.
     Questions about the operability of a claimed inven-
 tion—i.e., whether or not the claimed invention actually
Case: 20-1933    Document: 89      Page: 14    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                     11
 MYLAN PHARMACEUTICALS INC.

 works—can be relevant to patentability. “But written de-
 scription is about whether the skilled reader of the patent
 disclosure can recognize that what was claimed corre-
 sponds to what was described; it is not about whether the
 patentee has proven to the skilled reader that the inven-
 tion works, or how to make it work, which is an enablement
 issue.” Alcon Rsch. Ltd. v. Barr Lab’ys, Inc., 745 F.3d 1180,
 1191 (Fed. Cir. 2014); see also Miles Lab’ys, Inc. v. Shandon
 Inc., 997 F.2d 870, 875 (Fed. Cir. 1993) (noting that opera-
 bility is relevant “to the enablement requirement of § 112”).
 The enablement requirement has its own legal test and its
 own substantial body of precedent separate and apart from
 the written description requirement. See, e.g., In re Wands,
 858 F.2d 731 (Fed. Cir. 1988). 2 By focusing on whether the
 patentee proved that 480 mg per day is an effective
 amount to treat multiple sclerosis—as distinct from
 whether the ’514 patent specification discloses that 480
 mg per day is an effective amount to treat multiple sclero-
 sis—the panel majority and the district court erroneously
 imported operability considerations into the written de-
 scription analysis.
      In addition to blurring the lines between written de-
 scription and enablement, the panel majority and the dis-
 trict court also considered factors relevant to the
 inventorship of the ’514 patent. For example, the district
 court went into detail about the inventors’ “respective
 roles” in developing the patented technology. District
 Court Decision, 2020 WL 3317105, at *12. Similarly, the
 panel majority focused on what could be extrapolated from

     2    Operability is also relevant for the utility require-
 ment of 35 U.S.C. § 101. See, e.g., Newman v. Quigg, 877
 F.2d 1575, 1581 (Fed. Cir. 1989) (holding that under the
 utility requirement of 35 U.S.C. § 101, a claimed invention
 must “operate to produce what [the patentee] claims it
 does”).
Case: 20-1933    Document: 89       Page: 15   Filed: 03/16/2022

 12                                BIOGEN INTERNATIONAL GMBH
                              v.   MYLAN PHARMACEUTICALS INC.

 each inventor’s research as of the time the patent applica-
 tion was filed. See Panel Maj. Op., 18 F.4th at 1339–40
 (citing testimony from inventor Lukashev about whether
 clinical doses of DMF was the focus of his work); id. at 1344
 (discussing when inventor O’Neill may have conceived the
 idea for the invention). But again, the specification itself
 discloses that 480 mg per day of DMF is an effective dose
 in a method for treating multiple sclerosis. To the extent
 Mylan argued, or could have argued, that there was an in-
 ventorship problem with the ’514 patent, that is a separate
 issue from written description under 35 U.S.C. § 112.
     The district court also imported aspects of a “best
 mode” requirement into the written description analysis.
 The district court stated that “on reading the specification,
 a POSA would be drawn to, if anything, the 720mg/day
 dose of DMF included in each dosing example.” District
 Court Decision, 2020 WL 3317105, at *11 (emphasis
 added). The court then relied on testimony that a person
 of ordinary skill reading the specification “would not know
 which dose provided in Column 18 would be most effective
 for treating MS.” Id. (emphasis added). But there is no
 requirement that the written description be sufficient to
 “draw” a person of ordinary skill toward the claimed em-
 bodiment and away from unclaimed embodiments. And
 there is certainly no requirement that patent claims be lim-
 ited to only the “most effective” embodiment disclosed in
 the specification. See ScriptPro LLC v. Innovation Assocs.,
 Inc., 833 F.3d 1336, 1341 (Fed. Cir. 2016) (“[A] specifica-
 tion’s focus on one particular embodiment or purpose can-
 not limit the described invention where that specification
 expressly contemplates other embodiments or purposes.”).
     By incorporating extraneous legal standards into the
 analysis, the panel majority opinion creates confusion for
 future patent applicants and litigants regarding what is re-
 quired to meet the written description requirement of 35
 U.S.C. § 112. The en banc court should have corrected the
Case: 20-1933    Document: 89      Page: 16    Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                     13
 MYLAN PHARMACEUTICALS INC.

 panel majority’s errors and restored the proper and estab-
 lished boundaries of the written description inquiry.
                               D
      The fourth point of error is the consideration of extrin-
 sic evidence. The test for written description “requires an
 objective inquiry into the four corners of the specification.”
 Ariad, 598 F.3d at 1351. Yet, the panel majority affirmed
 a district court decision that is replete with reasoning that
 extends far beyond the confines of the disclosure contained
 in the patent specification.
     To be fair, because the written description inquiry is
 conducted from the perspective of a person of ordinary skill
 in the art, extrinsic evidence regarding how a person of or-
 dinary skill would understand what is disclosed in the pa-
 tent specification can, at times, be relevant. See, e.g.,
 Forest Lab’ys, LLC v. Sigmapharm Lab’ys, LLC, 918 F.3d
 928, 937–38 (Fed. Cir. 2019) (affirming sufficient written
 description based on expert testimony about how a specifi-
 cation’s disclosure would have been understood in view of
 what was known in the art); Space Sys./Loral, Inc. v. Lock-
 heed Martin Corp., 405 F.3d 985, 988–90 (Fed. Cir. 2005)
 (considering expert testimony regarding how the disclosure
 of the patent specification would have been interpreted by
 a skilled artisan). But, importantly, such extrinsic evi-
 dence should be used only as part of an objective inquiry
 into what is meant by the disclosure in the patent specifi-
 cation. Where the disclosure in a patent’s specification
 plainly corresponds to what is claimed, extrinsic evidence
 should not be used to cast doubt on the meaning of what is
 disclosed.
     Meaning is not in question in this case. The ’514 patent
 contains a disclosure that corresponds to what is claimed—
 treatment of multiple sclerosis with 480 mg per day of
 DMF. In my view, the extrinsic evidence does not render
 that disclosure inadequate to support what is claimed.
Case: 20-1933    Document: 89       Page: 17   Filed: 03/16/2022

 14                                BIOGEN INTERNATIONAL GMBH
                              v.   MYLAN PHARMACEUTICALS INC.

     The district court, however, went far beyond limiting
 its use of extrinsic evidence to interpreting what is dis-
 closed in the patent. Under the guise of considering what
 a person of ordinary skill in the art would have known as
 of the claimed priority date, the district court placed con-
 siderable weight on whether Biogen’s clinical trials before
 the filing date would have been sufficient to show the effi-
 cacy of particular doses of DMF to treat multiple sclerosis.
 See District Court Decision, 2020 WL 3317105, at *11
 (“Based on the results of Biogen’s Phase II study, . . . a
 POSA would have known that 720mg/day of DMF [] is a
 therapeutically effective dose for treating MS, and that
 lower doses, such as 360mg/day of DMF [] and 120mg/day
 of DMF [], are not.”). The court also considered the disclo-
 sures contained in later-filed Biogen patent applications
 and compared them to the disclosures of the ’514 patent.
 Id. at *13–14. The court went so far as to posit explana-
 tions for why the disclosures differed between the patent
 applications, including speculating about Biogen’s motiva-
 tions for its patent prosecution decisions based on the tim-
 ing of Biogen’s clinical trials and possible desires to avoid
 prior art. Id. at *14. And the court concluded its decision
 by considering the arguments Biogen made in a Patent
 Trial and Appeal Board proceeding while defending
 against Mylan’s inter partes review petitions. Id. at *15.
     Simply put, none of that is relevant to the question
 whether the ’514 patent specification contains sufficient
 written description to support what is claimed. The en
 banc court should have granted the petition for review to
 make that clear.
                        CONCLUSION
     I recognize the hesitance to go en banc simply to correct
 errors in one case. But this case involves more than that.
 Here, the panel majority has affirmed a district court’s er-
 roneous broadening of the written description inquiry. In
 denying rehearing en banc, the court has lost an
Case: 20-1933    Document: 89     Page: 18   Filed: 03/16/2022

 BIOGEN INTERNATIONAL GMBH v.                                   15
 MYLAN PHARMACEUTICALS INC.

 opportunity to provide clarity for future litigants by reaf-
 firming the proper boundaries of the written description re-
 quirement in 35 U.S.C. § 112.
    I therefore dissent from the court’s decision not to re-
 hear this case en banc.