Teva Pharmaceuticals International Gmbh v. Eli Lilly and Company

Case: 24-1094     Document: 65    Page: 1   Filed: 04/16/2026




   United States Court of Appeals
       for the Federal Circuit
                   ______________________

   TEVA PHARMACEUTICALS INTERNATIONAL
   GMBH, TEVA PHARMACEUTICALS USA, INC.,
              Plaintiffs-Appellants

                             v.

                ELI LILLY AND COMPANY,
                     Defendant-Appellee
                   ______________________

                         2024-1094
                   ______________________

     Appeal from the United States District Court for the
 District of Massachusetts in No. 1:18-cv-12029-ADB, Judge
 Allison Dale Burroughs.
                   ______________________

                  Decided: April 16, 2026
                  ______________________

    KEVIN P. MARTIN, Goodwin Procter LLP, Boston, MA,
 argued for plaintiffs-appellants. Also represented by
 ELAINE BLAIS; GABRIEL FERRANTE, New York, NY.

    WILLIAM BARRETT RAICH, Finnegan, Henderson,
 Farabow, Garrett & Dunner, LLP, Washington, DC, ar-
 gued for defendant-appellee. Also represented by CHARLES
 COLLINS-CHASE, DANIELLE ANDREA DUSZCZYSZYN, J.
 MICHAEL JAKES.
                 ______________________
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 2              TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


     Before PROST and CUNNINGHAM, Circuit Judges, and
                 ANDREWS, District Judge.1
 PROST, Circuit Judge.
     Teva Pharmaceuticals International GmbH and Teva
 Pharmaceuticals USA, Inc. (collectively, “Teva”) sued Eli
 Lilly and Company (“Lilly”) for infringing Teva’s U.S. Pa-
 tent Nos. 8,586,045 (“the ’045 patent”), 9,884,907 (“the
 ’907 patent”), and 9,884,908 (“the ’908 patent”) (collec-
 tively, the “headache patents”).
     A jury found that Lilly willfully infringed the headache
 patents and failed to prove their asserted claims invalid.
 The U.S. District Court for the District of Massachusetts
 then granted judgment as a matter of law (“JMOL”) that
 those claims are invalid for failure to satisfy both the writ-
 ten-description and enablement requirements of 

35 U.S.C. § 112

. Teva appeals. We reverse and remand.
                         BACKGROUND
                               I
     CGRP is a protein found in humans. When it binds to
 receptors on certain cells, the cells expand and increase
 blood flow through blood vessels—a phenomenon associ-
 ated with headache.
     Antibodies are proteins that an immune system pro-
 duces to fight disease. They do so by identifying and bind-
 ing to antigens, like CGRP. Relevant to this appeal are
 anti-CGRP antagonist antibodies, which bind to CGRP so
 as to “antagonize” (i.e., inhibit) CGRP and its headache-as-
 sociated activity. These antibodies can exist in mice. A
 process for converting a murine (i.e., mouse) antibody into



     1    Honorable Richard G. Andrews, District Judge,
 United States District Court for the District of Delaware,
 sitting by designation.
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                     3
 ELI LILLY AND COMPANY


 a form that the human immune system will not reject is
 known as humanization, and it results in “humanized” an-
 tibodies.
      The headache patents, which have a November 2006
 priority date, concern using humanized anti-CGRP antag-
 onist antibodies to treat headache. See, e.g., ’045 patent
 Abstract, col. 1 ll. 18–21, col. 4 ll. 50–51, claim 30.2 The
 specification observes that anti-CGRP antagonist antibod-
 ies were “known in the art,” and it cites prior art regarding
 murine antibodies of this sort. See 

id.

 at col. 25 ll. 59–63.
 For example, the specification references murine anti-
 CGRP antagonist antibody “4901” and cites a product cat-
 alog offering this antibody for sale. See 

id.

 at col. 25
 ll. 61–62 (citing product catalog shown at J.A. 18046); see
 also 

id.

 at col. 51 ll. 5–27, col. 55 ll. 22–23 (disclosing other
 murine anti-CGRP antagonist antibodies). The specifica-
 tion also states that “anti-CGRP antagonist antibodies may
 be made by any method known in the art.” 

Id.

 at col. 27
 ll. 41–42. And although the specification disclosed just one
 humanized anti-CGRP antagonist antibody—“G1,” which
 is the active ingredient in Teva’s Ajovy product, see, e.g., 

id.

 at cols. 72–73—it also disclosed prior-art methods of hu-
 manization, see 

id.

 at col. 28 l. 55–col. 29 l. 28.
     Claim 30 of the ’045 patent is representative of the as-
 serted claims for purposes of this appeal.3 Rewritten to-
 gether with claim 17, from which it depends, claim 30
 recites:
     A method for reducing incidence of or treating
     headache in a human, comprising administering to



     2    Because the headache patents share a substan-
 tively identical specification, for convenience, we cite only
 the ’045 patent’s specification.
     3    The asserted claims are claim 30 of the ’045 patent
 and claims 5 and 6 of each of the ’907 and ’908 patents.
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 4              TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


     the human an effective amount of an anti-CGRP
     antagonist antibody, wherein said anti-CGRP an-
     tagonist antibody is a . . . humanized monoclonal
     antibody.
 

Id.

 at claims 17, 30.
                              II
     Between August and October 2018, Lilly filed petitions
 for inter partes review (“IPR”) with the Patent Trial and
 Appeal Board (“Board”) challenging several of Teva’s pa-
 tents. Those patents fell into two groups. One was the
 headache patents—which, as noted above, claim a method
 of using humanized anti-CGRP antagonist antibodies to
 treat headache. The other group we refer to as the “anti-
 body patents,” because they claimed humanized anti-
 CGRP antagonist antibodies themselves.4
     In arguing that claims of the antibody patents are un-
 patentable for obviousness, Lilly maintained that, by No-
 vember 2006, anti-CGRP antagonist antibodies “were well
 known in the art”—indeed, that the prior art was “replete
 with exemplary disclosures of anti-CGRP antagonist anti-
 bodies.” J.A. 21417 (capitalization normalized); J.A. 21513.
 Techniques for making such antibodies were also, accord-
 ing to Lilly, “extensively described in the prior art.”
 J.A. 21442; see also J.A. 21417 (“[S]everal publications had
 described anti-CGRP antagonist antibodies and methods of
 making them.”). And, as to humanization, Lilly main-
 tained that it “was a well-established and routine proce-
 dure” by November 2006. See J.A. 21407.
     The Board determined that, although the antibody pa-
 tents’ challenged claims were unpatentable, those of the



     4  The antibody patents are U.S. Patent Nos.
 9,340,614; 9,266,951; 9,890,210; 9,346,881; 9,890,211; and
 8,597,649.
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                  5
 ELI LILLY AND COMPANY


 headache patents were not. Each Board decision was ap-
 pealed to this court, and we affirmed as to each. See Teva
 Pharms. Int’l GmbH v. Eli Lilly & Co., 

8 F.4th 1349

 (Fed. Cir. 2021) (three of the antibody patents); Teva
 Pharms. Int’l GmbH v. Eli Lilly & Co., 

856 F. App’x 312

 (Fed. Cir. 2021) (the other three antibody patents); Eli Lilly
 & Co. v. Teva Pharms. Int’l GmbH, 

8 F.4th 1331

 (Fed. Cir.
 2021) (the headache patents).
                              III
     Teva brought this suit against Lilly in September 2018,
 alleging that Lilly indirectly infringed the headache pa-
 tents via its Emgality product.5
     At the ensuing trial, the jury returned a verdict for
 Teva, finding that Lilly willfully infringed the asserted
 claims and did not prove them invalid for lack of written
 description or enablement. It awarded Teva damages ac-
 cordingly.
      Lilly then moved for JMOL of invalidity on written de-
 scription and enablement, which the district court granted.
 See Teva Pharms. Int’l GmbH v. Eli Lilly & Co., No. 18-cv-
 12029, 

2023 WL 6282898

 (D. Mass. Sep. 26, 2023) (“JMOL
 Op.”). The district court acknowledged that the jury could
 have permissibly found that murine anti-CGRP antagonist
 antibodies were known in the art and disclosed in the spec-
 ification. See 

id. at *12

. The court also acknowledged that
 a person of ordinary skill in the art would have (1) known
 methods for making murine anti-CGRP antagonist anti-
 bodies; (2) known that humanizing antibodies was routine;
 and (3) understood from the specification that all human-
 ized anti-CGRP antagonist antibodies would treat head-
 ache. See 

id. at *4, *12

, *19 n.23. The court nonetheless


     5   Teva also alleged infringement of the antibody pa-
 tents, but it dismissed those claims after we affirmed the
 Board’s unpatentability decisions as to those patents.
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 6              TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 concluded that, as a matter of law, the asserted claims are
 invalid for lack of both written description and enablement.
    Teva timely appealed.6 We have jurisdiction under
 

28 U.S.C. § 1295

(a)(1).
                         DISCUSSION
     We review grants of JMOL under the law of the re-
 gional circuit—here, the First Circuit. See Akamai Techs.,
 Inc. v. Limelight Networks, Inc., 

805 F.3d 1368, 1374

 (Fed. Cir. 2015). We therefore review the district court’s
 JMOL de novo and will reinstate the jury verdict “unless
 the facts and inferences, viewed in the light most favorable
 to the verdict, point so strongly and overwhelmingly” in
 Lilly’s favor “that a reasonable jury could not have re-
 turned the verdict.” See Acevedo-Diaz v. Aponte, 

1 F.3d 62, 66

 (1st Cir. 1993) (cleaned up); see also Pac. Biosciences of
 Cal., Inc. v. Oxford Nanopore Techs., Inc., 

996 F.3d 1342

,
 1350 (Fed. Cir. 2021) (noting that, in reviewing a JMOL,
 we generally “treat the jury as having made all verdict-sup-
 porting factual findings that are supported by substantial
 evidence”).
      The JMOL inquiry accounts for the applicable burden
 and standard of proof, see Anderson v. Liberty Lobby, Inc.,
 

477 U.S. 242

, 250–55 (1986), and here, Lilly had the burden
 to prove facts underlying its invalidity case by clear and
 convincing evidence, see, e.g., BASF Corp. v. SNF Holding
 Co., 

955 F.3d 958, 963

 (Fed. Cir. 2020). So, if a reasonable
 jury could have found that Lilly failed to prove its invalid-
 ity case by clear and convincing evidence, we must reverse
 the JMOL. See Boehringer Ingelheim Vetmedica, Inc. v.




     6    Lilly conditionally cross-appealed regarding dam-
 ages but later voluntarily dismissed that appeal. See Order
 (Sep. 8, 2025), ECF No. 64.
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                   7
 ELI LILLY AND COMPANY


 Schering-Plough Corp., 

320 F.3d 1339, 1353

 (Fed. Cir.
 2003).
     The invalidity issues in this case concern 

35 U.S.C. § 112

 ¶ 1,7 which states in relevant part:
     The specification shall contain a written descrip-
     tion of the invention, and of the manner and pro-
     cess of making and using it, in such full, clear,
     concise, and exact terms as to enable any person
     skilled in the art to which it pertains, or with which
     it is most nearly connected, to make and use the
     same . . . .
 This provision contains two separate requirements: writ-
 ten description and enablement. See, e.g., Centrak, Inc. v.
 Sonitor Techs., Inc., 

915 F.3d 1360, 1366

 (Fed. Cir. 2019)
 (citing Ariad Pharms., Inc. v. Eli Lilly & Co., 

598 F.3d 1336, 1351

 (Fed. Cir. 2010) (en banc)).
     We first discuss written description, then enablement.
 Because the parties focus more on written description, we
 do the same.




     7    The Leahy-Smith America Invents Act (“AIA”) es-
 sentially redesignated § 112 ¶ 1 as § 112(a). See AIA, 

Pub. L. No. 112-29, sec. 4

(c), 

125 Stat. 284

, 296 (2011). Given
 the filing dates of the applications for the headache pa-
 tents, the pre-AIA version applies to the ’045 patent,
 whereas the AIA version applies to the other two patents.
 See 

id.

 sec. 4(e), 125 Stat. at 297 (applying AIA version to
 any patent application filed on or after September 16,
 2012). Because any difference between the two versions is
 immaterial to this opinion’s discussion, and because we cite
 only the ’045 patent’s specification, we refer to the pre-AIA
 version throughout this opinion.
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 8              TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


                               I
     To satisfy the written-description requirement of § 112
 ¶ 1, a patent’s specification must “reasonably convey[]”
 that, as of the filing date, “the inventor[s] had possession
 of the claimed subject matter”—i.e., that they “actually in-
 vented the invention claimed.” See Ariad, 

598 F.3d at 1351

. This test requires an “objective inquiry into the
 four corners of the specification from the perspective of a
 person of ordinary skill in the art,” 

id.,

 who “comes to the
 patent with the knowledge of what has come before,” Falko-
 Gunter Falkner v. Inglis, 

448 F.3d 1357, 1366

 (Fed. Cir.
 2006) (cleaned up). Whether a patent satisfies the written-
 description requirement is a question of fact, and what it
 takes to satisfy that requirement varies depending on the
 context, including the nature and scope of the claims. Ar-
 iad, 

598 F.3d at 1351

; see Capon v. Eshhar, 

418 F.3d 1349

,
 1358 (Fed. Cir. 2005) (“The ‘written description’ require-
 ment states that the patentee must describe the invention;
 it does not state that every invention must be described in
 the same way.”).
     For claims to a genus, adequate written description re-
 quires disclosure of “either a representative number of spe-
 cies falling within the scope of the genus or structural
 features common to the 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

 (cleaned up). As with
 written description generally, there are no “bright-line
 rules governing . . . the number of species that must be dis-
 closed to describe a genus claim, as this number necessarily
 changes with each invention.” 

Id. at 1351

.
     The written-description dispute in this case concerns
 whether the specification disclosed a representative num-
 ber of species of the asserted claims’ genus of humanized
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                 9
 ELI LILLY AND COMPANY


 anti-CGRP antagonist antibodies.8 We first discuss rele-
 vant precedent and why it supports the jury’s finding re-
 garding written description. We then address, and reject,
 Lilly’s arguments for JMOL on this issue.
                              A
     Several of our cases are particularly instructive for an-
 alyzing written description in circumstances like those
 here—where a claim pertains to a well-known genus that
 is not, itself, the invention.
     In Ajinomoto, for example, the patent disclosed that en-
 hancing the activity of a bacterium’s yddG gene would in-
 crease the bacterium’s production of particular amino
 acids. The patent also disclosed several ways of enhancing
 that activity, one of which was substituting a “more potent
 promoter” in the bacterium’s DNA. See Ajinomoto Co. v.
 ITC, 

932 F.3d 1342

, 1346–47 (Fed. Cir. 2019). The claim
 covered a method of producing particular amino acids from
 a bacterium having a “more potent promoter” for its yddG
 gene substituted. The patent challenger argued that the
 genus of “more potent promoters” lacked adequate written
 description because the specification did not disclose a rep-
 resentative number of species. The ITC rejected that argu-
 ment, and on appeal, we affirmed. We initially observed
 that, because the patent disclosed four examples of “potent
 promoters” and cited an article disclosing examples
 thereof, substantial evidence supported the ITC’s finding
 that “enhancing promoter activity was well-known” and
 that a skilled artisan “would have been able to identify
 more potent promoters by employing common tools.” 

Id. at 1359

 (cleaned up). We then reasoned that the patent
 “ma[de] clear” that its invention was identifying the yddG



     8   On appeal, Teva does not argue that the specifica-
 tion disclosed structural features common to the members
 of that genus.
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 10             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 gene and discovering that enhancing its activity increased
 the amino acids’ production; it was “not the well-known
 techniques” for enhancing that activity. 

Id.

 (emphasis
 added). Because “the genus of more potent promoters was
 already well explored” in the art by the time of the patent’s
 invention, the ITC “permissibly found in the specification,
 read in light of the background knowledge in the art, a rep-
 resentative number of species.” 

Id.

      Our predecessor court confronted a similar situation in
 Herschler. There, the inventor discovered that a certain
 chemical, DMSO, enhances skin penetration of other ma-
 terials. The claim was to a method of enhancing skin pen-
 etration of a “physiologically active steroidal agent” by
 applying it together with DMSO. In re Herschler, 

591 F.2d 693, 695

 (CCPA 1979). The court concluded that the spec-
 ification adequately described the genus of “physiologically
 active steroidal agent[s]” because, even though it disclosed
 just one species thereof, a skilled artisan reading the spec-
 ification would understand that any member of the genus
 would work in the claimed method. See 

id.

 at 700–01. In
 reaching this conclusion, the court repeatedly distin-
 guished between claims to a genus itself (particularly a
 novel one) and claims that, like the one at issue, concerned
 a known genus used as part of a different invention. See
 

id.

 at 701–02. For example, it acknowledged that while
 steroids “as drugs” might vary broadly in their physiologi-
 cal activity, steroids “as a class of compounds carried
 through a layer of skin by DMSO” appeared on the record
 to be “quite similar.” 

Id. at 701

 (emphasis added); see also
 

id. at 702

 (distinguishing between claims to “classes of new
 compounds per se or . . . processes using those new com-
 pounds” and “claims drawn to the use of known . . . com-
 pounds in a manner auxiliary to the invention” (some
 emphasis removed)); 

id. at 701

 (observing that, “[w]ere this
 application drawn to novel ‘steroidal agents,’ a different
 question would be posed”).
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                  11
 ELI LILLY AND COMPANY


      The plurality opinion in Fuetterer was key to the court’s
 reasoning in Herschler. See Herschler, 591 F.2d at 701–02
 (citing In re Fuetterer, 

319 F.2d 259

 (CCPA 1963) (Rich,
 J.)).9 In Fuetterer, the claim was to a composition for tire-
 tread stock, one component of which was “an inorganic salt
 that is capable of holding a mixture . . . in colloidal suspen-
 sion in water.” 319 F.2d at 260–61. The specification dis-
 closed only four such salts. 

Id. at 265

. The Patent and
 Trademark Office had rejected the claim under § 112 ¶ 1,10
 “believing that not all inorganic salts are capable of per-
 forming” the specified function and that “one skilled in the
 art would not know offhand which inorganic salts are ca-
 pable of so functioning.” Id. On appeal, the court reversed.
 As the plurality opinion explained:
     Appellant’s invention is the combination claimed
     and not the discovery that certain inorganic salts
     have colloid suspending properties. We see nothing
     in patent law which requires appellant to discover
     which of all those salts have such properties and
     which will function properly in his combination.
     The invention description clearly indicates that



     9    We appreciate that the plurality opinion in Fuet-
 terer is not binding, given that only two judges of the five-
 judge panel joined it (a third concurred in the result). See
 

319 F.2d at 266

. Yet Herschler, which is binding, relied
 heavily on the plurality opinion in Fuetterer. See Hersch-
 ler, 

591 F.2d at 701

 (“We wish to maintain the line first
 clearly drawn in [Fuetterer].”). And, regardless of its status
 as binding precedent, we may (and do) consider it persua-
 sive authority.
      10  Technically, the rejection was for “undue breadth,”
 but we later explained that such a rejection was “based on
 the first paragraph of § 112” for insufficient disclosure. In
 re Hyatt, 

708 F.2d 712

, 714–15 (Fed. Cir. 1983) (citing In re
 Borkowski, 

422 F.2d 904, 909

 (CCPA 1970)).
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 12             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


      any inorganic salt which has such properties is us-
      able in his combination. If others in the future dis-
      cover what inorganic salts additional to those
      enumerated do have such properties, it is clear ap-
      pellant will have no control over them per se, and
      equally clear his claims should not be so restricted
      that they can be avoided merely by using some in-
      organic salt not named by appellant in his disclo-
      sure.
 Id. at 265 (emphasis in original); see id. at 266 (reiterating
 that the appellant “has not invented, and is not claiming,
 colloid suspending agents”).11
     The circumstances here fit well within this line of prec-
 edent. The headache patents make clear that their claimed
 invention is the use of anti-CGRP antagonist antibodies, or
 humanized versions thereof, to treat headache—not such
 antibodies themselves. See, e.g., ’045 patent claim 30. A
 reasonable jury could have found that anti-CGRP antago-
 nist antibodies themselves and methods of making them
 were well known, replete, or extensively described in the
 prior art—based on Lilly’s own statements that they were
 “well known,” “replete,” or “extensively described” in the



      11    See also Erfindergemeinschaft UroPep GbR v. Eli
 Lilly & Co., 

276 F. Supp. 3d 629, 648

 (E.D. Tex. 2017)
 (Bryson, J., sitting by designation) (“It is often the case that
 a patent claiming the invention of a new genus, or the use
 of a new genus, must provide more detail regarding that
 genus, such as disclosing a number of representative spe-
 cies . . . . On the other hand, when a genus is well under-
 stood in the art and not itself the invention but is instead a
 component of the claim, background knowledge may pro-
 vide the necessary support for the claim.” (emphasis
 added)), aff’d, 

739 F. App’x 643

 (Fed. Cir. 2018) (nonprece-
 dential).
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                 13
 ELI LILLY AND COMPANY


 prior art.12 See J.A. 21417 (capitalization normalized);
 J.A. 21513; J.A. 21442. A reasonable jury could have also
 found that humanization was a well-established and rou-
 tine procedure by the priority date—again, based on Lilly’s
 own statements that it “was a well-established and routine
 procedure” by the priority date.13 J.A. 21407. And, as Lilly
 does not dispute, a reasonable jury could have found that a
 skilled artisan would have understood from the specifica-
 tion that all humanized anti-CGRP antagonist antibodies
 treat headache. See, e.g., J.A. 4174, 4272; see also JMOL
 Op., 

2023 WL 6282898

, at *12, *19 n.23.
     Taken together, these fact findings (which we treat the
 jury as having made)—along with the specification’s disclo-
 sures—suffice to support the jury’s rejection of Lilly’s writ-
 ten-description challenge. The asserted claims are to
 methods of using humanized anti-CGRP antagonist anti-
 bodies to treat headache. Although the specification dis-
 closed just one humanized anti-CGRP antagonist antibody,
 it also disclosed several murine versions and prior-art
 methods of humanization—against a backdrop of anti-
 CGRP antagonist antibodies (and methods of making
 them) being well known and humanization being routine.
 And, critically, a skilled artisan would have understood
 from the specification that all humanized anti-CGRP an-
 tagonist antibodies treat headache. The jury therefore
 could have reasonably found that the specification dis-
 closed a representative number of species of humanized



     12  Substantial evidence apart from Lilly’s statements
 also supported such a finding. See, e.g., J.A. 4059, 4063–67,
 4119–26 (testimony of Teva’s expert Dr. Hill); J.A. 4209–14
 (testimony of Teva’s expert Dr. Hale).
     13  Again, substantial evidence apart from Lilly’s
 statements also supported such a finding. See, e.g.,
 J.A. 4220–24 (testimony of Teva’s expert Dr. Hale);
 J.A. 3295–96 (testimony of Lilly’s expert Dr. McDonnell).
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 14             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 anti-CGRP antagonist antibodies for purposes of the
 claimed invention, thus rendering JMOL of no written de-
 scription improper.
                               B
                               1
     Lilly tries, unsuccessfully, to distinguish the foregoing
 precedent. Its attempt focuses on the requirement that the
 antibodies be humanized.
     Specifically, Lilly notes that, however one views the
 prior-art status of anti-CGRP antagonist antibodies gener-
 ally,14 humanized versions of those antibodies were not
 known—indeed, were absent from the prior art altogether.
 Lilly also observes that the specification disclosed only one
 humanized version. And, as to the murine anti-CGRP an-
 tagonist antibodies disclosed in the specification, Lilly
 maintains that they cannot count towards representative-
 ness of the genus of humanized antibodies, because they
 are not truly members of that genus. Lilly therefore main-
 tains that the circumstances here cannot fit within the line
 of precedent discussed above concerning a well-known ge-
 nus used as part of a different invention.
      Lilly’s focus on humanization to show lack of written
 description is unpersuasive. As already discussed, a rea-
 sonable jury could have found that, by the priority date,
 (1) anti-CGRP antagonist antibodies and methods of mak-
 ing them were well known, and (2) humanization was a
 routine procedure. The specification also disclosed several
 examples of murine anti-CGRP antagonist antibodies and



      14  To the extent Lilly suggests that anti-CGRP antag-
 onist antibodies generally—even murine ones—were not
 well known as of the priority date, see Appellee’s Br. 49, 51,
 61, the jury could have readily found otherwise, for reasons
 already discussed.
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 ELI LILLY AND COMPANY


 prior-art methods of humanization. See ’045 patent col. 25
 ll. 59–63, col. 51 ll. 5–27 (murine anti-CGRP antagonist an-
 tibodies); 

id.

 at col. 28 l. 55–col. 29 l. 28 (prior-art humani-
 zation methods). As the jury could have seen it, murine
 versions—themselves well known, with several examples
 disclosed—were just a routine (and likewise disclosed) pro-
 cedure away from being humanized. That being so, and
 because a specification need not show an actual reduction
 to practice in order to satisfy the written-description re-
 quirement, e.g., Ariad, 

598 F.3d at 1352

, the humanization
 requirement does not undermine the well-known status of
 the non-humanized anti-CGRP antagonist antibodies or
 otherwise render the above-discussed line of precedent in-
 applicable.
     Lilly nonetheless insists that, even if humanizing these
 antibodies might have been obvious in view of the specifi-
 cation, “a description that merely renders the invention ob-
 vious does not satisfy” the written-description
 requirement.      See Appellee’s Br. 52 (quoting Ariad,
 

598 F.3d at 1352

). This principle, while correct, does not
 help Lilly. The specification did not merely render human-
 izing these antibodies obvious; it explicitly disclosed as
 much, along with how to do it, via prior-art methods that a
 reasonable jury could have found were routine. See, e.g.,
 ’045 patent col. 4 ll. 50–51 (“In some embodiments, the
 anti-CGRP antagonist antibody is humanized.”); 

id.

 at col. 28 l. 55–col. 29 l. 28 (prior-art humanization meth-
 ods).
     Lilly also argues that, because humanizing an anti-
 CGRP antagonist antibody requires knowing its amino
 acid sequence, and because no such sequences were dis-
 closed in the specification or prior art, adequate written de-
 scription is lacking. See Appellee’s Br. 49–51. We are
 unpersuaded. Substantial evidence showed that if a skilled
 artisan possessed an anti-CGRP antagonist antibody, he or
 she could “determin[e] its amino acid sequence through
 known sequencing techniques.”               See J.A. 21675
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 16             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 (declaration of Lilly’s own expert concerning a prior-art ref-
 erence that is also cited in the ’045 patent). And there
 seems to be no dispute that the inventors possessed at least
 the particular anti-CGRP antagonist antibodies disclosed
 in the specification. Further, substantial evidence shows
 that, more generally, anti-CGRP antagonist antibodies
 were accessible before the priority date. See J.A. 18046
 (product catalog offering antibody “4901” for sale);
 J.A. 4122 (testimony regarding a researcher who received
 seven such antibodies as a gift from another researcher);
 see also supra note 12. Accordingly, a reasonable jury could
 have found that the specification demonstrates that the in-
 ventors possessed sequences necessary to humanize anti-
 CGRP antagonist antibodies.
     Finally, even apart from humanization, Lilly takes is-
 sue with the distinction we have drawn between (1) claims
 to a method of using humanized anti-CGRP antagonist an-
 tibodies to treat headache and (2) claims to such antibodies
 themselves. According to Lilly, this is a “semantic distinc-
 tion without a difference.” See Appellee’s Br. 61 (quoting
 Univ. of Rochester v. G.D. Searle & Co., 

358 F.3d 916, 926

 (Fed. Cir. 2004)); see also 

id.

 (citing Ariad, 

598 F.3d at 1355

). We disagree with Lilly—for at least two related
 reasons.
     First, the above-discussed line of precedent supports
 this distinction, see, e.g., Herschler, 591 F.2d at 701–02,
 and Lilly has not shown why that precedent does not apply
 here.
      Second, the cases Lilly relies on for its “semantics” ar-
 gument are easily distinguished. For example, in Roches-
 ter, the claims were to methods of selectively inhibiting the
 activity of a particular gene product (PGHS-2) by adminis-
 tering a compound that selectively inhibits such activity.
 See 

358 F.3d at 918

. In maintaining that adequate written
 description existed, the patentee argued that the claims
 were to methods, not the compounds themselves. See 

id.

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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                  17
 ELI LILLY AND COMPANY


 at 926. We deemed this a “semantic distinction without a
 difference,” because the specification did not disclose any
 compounds usable in the claimed methods, nor was there
 any evidence that such compounds were known. See 

id.

 at 926–27. That is not the case here, where anti-CGRP an-
 tagonist antibodies were well known in the prior art and
 disclosed in the specification. Likewise, in Ariad, the
 claims were to methods of reducing the activity of a partic-
 ular transcription factor (NF-êB). 

598 F.3d at 1341

. We
 said that demonstrating possession of the claimed methods
 required “sufficiently disclosing molecules capable of re-
 ducing NF-êB activity.” 

Id. at 1355

. The problem was that
 the specification did not sufficiently disclose such mole-
 cules; instead, of the three types of molecules it “hypothe-
 size[d],” two had no adequately disclosed examples at all,
 and the third had insufficient disclosure of its ability to re-
 duce NF-êB activity. See 

id.

 at 1355–58.
      Moreover, in Rochester, the claims were to methods of
 selectively inhibiting PGHS-2’s activity by administering a
 compound that selectively inhibits PGHS-2’s activity. In
 effect, the claims were to methods of doing X using “some-
 thing that does X.” Thus, not only was the compound in
 Rochester not disclosed or otherwise known, the use to
 which it was put could not fairly be considered part of a
 different invention. Ariad presented a similar situation:
 the claims were to methods of doing X, and the claims “en-
 compass[ed] the use of all substances” that did X. See
 

598 F.3d at 1341

. Here, in contrast, the asserted claims
 are not to “methods of antagonizing CGRP using human-
 ized antibodies that antagonize CGRP”; they are to meth-
 ods of treating headache using such antibodies—something
 different from the function that characterizes these anti-
 bodies.
     Simply put, neither of these cases presented the cir-
 cumstances of the above-discussed line of precedent and
 this case—i.e., a well-known genus used as part of a differ-
 ent invention.
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 18             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


                              2
     Lilly’s other arguments for JMOL of no written descrip-
 tion generally concern structural or functional differences
 among the genus of humanized anti-CGRP antagonist an-
 tibodies.15 These arguments are likewise unpersuasive.
     For example, Lilly notes that CGRP has three regions
 to which an anti-CGRP antagonist antibody might bind—
 namely, the C-terminal, mid-region, and N-terminal. It
 then argues that, because the anti-CGRP antagonist anti-
 bodies disclosed in the specification bind only to the C-ter-
 minal, adequate written description is lacking.          See
 Appellee’s Br. 15, 45. We reject this argument. Initially, a
 reasonable jury could have found that, for each of the three
 regions, an anti-CGRP antagonist antibody that binds to it
 was known in the prior art. See, e.g., J.A. 3321–24, 4125,
 21998. More importantly, as the district court recog-
 nized—and as Lilly does not dispute—a reasonable jury
 could have found that a skilled artisan reading the specifi-
 cation would have understood that “anti-CGRP antagonist
 antibodies could bind to different regions of CGRP and still
 accomplish the claimed function of treating headache.” See
 JMOL Op., 

2023 WL 6282898

, at *14. Thus, like the ster-
 oids in Herschler—which might have varied broadly as
 drugs but performed quite similarly in the claimed method,
 see 591 F.2d at 701—here, the differences in binding re-
 gions among humanized anti-CGRP antagonist antibodies
 do not prevent those antibodies from performing in the
 claimed method of treating headache. Those differences



      15 Although Lilly also advances an argument concern-
 ing the purported breadth associated with the genus, see
 Appellee’s Br. 36–39, it makes essentially the same argu-
 ment in the context of enablement, see 

id.

 at 54–58, which
 is where we deem the argument better addressed, see infra
 Discussion Part II.
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                19
 ELI LILLY AND COMPANY


 therefore do not demonstrate inadequate written descrip-
 tion for that method.
     Relatedly, Lilly argues that, because its product differs
 structurally and functionally from G1 (the sole humanized
 anti-CGRP antagonist antibody disclosed in the specifica-
 tion), written description must be inadequate. For this ar-
 gument, Lilly cites AbbVie as having required disclosure of
 an antibody “structurally similar” to the accused antibody
 in order to show representativeness. See Appellee’s
 Br. 40–41 (quoting AbbVie Deutschland GmbH & Co. v.
 Janssen Biotech, Inc., 

759 F.3d 1285, 1301

 (Fed. Cir.
 2014)).16 We reject this argument as well. Lilly has not
 explained, nor do we see, why we should treat any of the
 alleged structural or functional differences between Lilly’s
 product and G1 differently from the way we treat the vari-
 ous possible binding regions discussed above. In both
 cases, the relevant point remains: a reasonable jury could
 have found that a skilled artisan reading the specification
 would have understood that anti-CGRP antagonist anti-
 bodies were well known (and disclosed), that humanizing
 was routine (and disclosed), and that, insofar as treating
 headache is concerned, all humanized versions of such



     16   Lilly also suggests that Juno supports such a re-
 quirement for representativeness.            See Appellee’s
 Br. 41–42 (citing Juno Therapeutics, Inc. v. Kite Pharma,
 Inc., 

10 F.4th 1330, 1339

 (Fed. Cir. 2021)). Juno, however,
 did not directly address any specific requirement to dis-
 close a composition structurally similar to the accused com-
 position in order to satisfy representativeness. Further,
 the portion of Juno that Lilly cites for this argument con-
 cerned “structural features common to the members of the
 genus,” 10 F.4th at 1338–39—not representativeness. And
 Teva does not argue that the specification disclosed struc-
 tural features common to the members of the genus of hu-
 manized anti-CGRP antagonist antibodies. Supra note 8.
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 20             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 antibodies work. The specification therefore disclosed
 members of the genus that are sufficiently representative
 for purposes of the claimed invention.17
     Further, while this court did conclude in AbbVie that
 adequate written description was lacking—in part because
 there was no evidence that any disclosed antibody was
 “structurally similar to, and thus representative of,” the ac-
 cused product, 

759 F.3d at 1301

 (emphasis added)—we do
 not understand AbbVie to have set forth a bright-line, al-
 ways-applicable rule that representativeness requires dis-
 closure of a composition structurally similar to the accused
 product. Indeed, as the above-discussed line of precedent
 demonstrates, the representativeness inquiry accounts for
 the specific circumstances of the invention, see, e.g.,
 Ajinomoto, 

932 F.3d at 1359

; see also Ariad, 

598 F.3d at 1351

 (observing that there are no “bright-line rules gov-
 erning . . . the number of species that must be disclosed to
 describe a genus claim, as this number necessarily changes
 with each invention”), and AbbVie did not involve the cir-
 cumstances relevant here and in that precedent—i.e., a
 well-known genus used as part of a different invention.
   Thus, for the foregoing reasons, we conclude that
 JMOL of no written description was improper.




      17  Although Lilly also maintains that adequate writ-
 ten description is lacking because its product treats “clus-
 ter” headache, whereas G1 does not, a reasonable jury
 could have found that Lilly’s support for these factual prop-
 ositions was less than clear and convincing. See, e.g.,
 J.A. 4018–21 (testimony of Teva’s expert Dr. Blumenfeld
 regarding the impact of different study designs on efficacy
 of cluster-headache treatment).
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.                21
 ELI LILLY AND COMPANY


                              II
     Enablement and written description “often rise and fall
 together.” Ariad, 

598 F.3d at 1352

. So it is here.
      To satisfy the enablement requirement of § 112 ¶ 1, a
 patent’s specification “must teach those skilled in the art
 how to make and use the full scope of the claimed invention
 without undue experimentation.” MagSil Corp. v. Hitachi
 Glob. Storage Techs., Inc., 

687 F.3d 1377, 1380

 (Fed. Cir.
 2012) (cleaned up); see also § 112 ¶ 1 (requiring a descrip-
 tion of the invention “and of the manner and process of
 making and using it, in such full, clear, concise, and exact
 terms as to enable” a skilled artisan “to make and use the
 same”). The specification’s teachings in this regard must
 be “at least commensurate with the scope of the claims.”
 E.g., Amgen Inc. v. Sanofi, 

987 F.3d 1080, 1084

 (Fed. Cir.
 2021) (cleaned up), aff’d, 

598 U.S. 594

 (2023). Although
 whether a claim is enabled is a question of law that we re-
 view de novo, in the context of a jury trial, any factual un-
 derpinnings are reviewed for substantial evidence. See,
 e.g., Trs. of Bos. Univ. v. Everlight Elecs. Co., 

896 F.3d 1357, 1361

 (Fed. Cir. 2018).
      Lilly’s no-enablement argument concerns the pur-
 ported breadth associated with the genus of humanized
 anti-CGRP antagonist antibodies. Lilly maintains that the
 number of candidate antibodies for inclusion in this genus
 is very large and that the specification does not tell a
 skilled artisan how to determine in advance which ones
 will antagonize CGRP. Instead, Lilly says, the inventors
 left to others the “research assignment” of screening and
 testing those candidates to make that determination. In
 Lilly’s view, these efforts would have been so time-consum-
 ing and expensive as to constitute undue experimentation.
 See Appellee’s Br. 54–58.
     In addressing Lilly’s no-enablement argument, we will
 assume two things in its favor, solely for argument’s sake.
 First, we will assume that a reasonable jury could have
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 22             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 only found that making all anti-CGRP antagonist antibod-
 ies would have required screening and testing a very large
 number of candidate antibodies to determine which ones
 do, in fact, antagonize CGRP. Second, we will assume that,
 even if a reasonable jury could have found that such mak-
 ing, screening, and testing would have been routine in this
 field as of the priority date, see, e.g., J.A. 4212–14, 4250,
 the amount of time and expense required to make (and hu-
 manize) all anti-CGRP antagonist antibodies would have
 constituted undue experimentation, see, e.g., Idenix
 Pharms. LLC v. Gilead Scis. Inc., 

941 F.3d 1149, 1163

 (Fed. Cir. 2019) (observing that a substantial amount of ex-
 perimentation, “even if routine,” can be undue (cleaned
 up)).
     With these assumptions in mind, we note that Lilly’s
 argument might be more persuasive if the asserted claims
 were to the genus of humanized anti-CGRP antagonist an-
 tibodies themselves. If that were so, this case would re-
 semble Amgen. There, the claims were to the entire genus
 of antibodies that (1) bind to specific amino acid residues
 on the protein PCSK9 and (2) block PCSK9 from binding to
 certain receptors. Amgen, 598 U.S. at 602. Yet, although
 the patentee laid claim to that entire genus (for any and all
 purposes), its specification failed to teach a skilled artisan
 how to find more of these antibodies without engaging in
 an unreasonable amount of experimentation. The specifi-
 cation’s mere disclosure of steps by which a skilled artisan
 might find more was, in the context of that invention, not
 enablement; instead, it was “little more than [a] research
 assignment[]” comprised of “painstaking” trial and error.
 Id. at 614 (cleaned up). We later applied a similar analysis
 and reached a similar conclusion in Baxalta, which in-
 volved facts “materially indistinguishable from those in
 Amgen.” Baxalta Inc. v. Genentech, Inc., 

81 F.4th 1362, 1366

 (Fed. Cir. 2023).
   The asserted claims here are unlike the claims in
 Amgen and Baxalta, however, because they do not claim
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 TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.               23
 ELI LILLY AND COMPANY


 humanized anti-CGRP antagonist antibodies themselves;
 instead, they claim only the use of such antibodies for the
 different, limited purpose of treating headache. In light of
 the well-known status of anti-CGRP antagonist antibodies
 and the routine nature of humanization, the more relevant
 “research assignment” in this case would have been deter-
 mining which humanized anti-CGRP antagonist antibod-
 ies treat headache. See Amgen, 

987 F.3d at 1084

 (observing
 that the specification’s teachings must be “at least com-
 mensurate with the scope of the claims”). That assignment
 was completed; the specification disclosed that all such an-
 tibodies work for that purpose. Given that anti-CGRP an-
 tagonist antibodies (and methods of making them) were
 already well known, humanizing them would have been
 routine, such humanized antibodies themselves are not
 claimed here, and all of them work in the claimed method,
 undertaking to find or make all of them would—in the con-
 text of these claims—be more akin to extra credit than a
 necessary research assignment left to others to complete.
     Finally, we conclude that the circumstances here are
 distinguishable from Idenix, a case upon which Lilly relies
 heavily. There, the claim was to a method of using a 2’-
 methyl-up nucleoside to treat the hepatitis C virus
 (“HCV”), and the number of potential 2’-methyl-up nucleo-
 sides was quite large. We framed the “key enablement
 question” as “whether a person of ordinary skill in the art
 would know, without undue experimentation, which 2’-me-
 thyl-up nucleosides would be effective for treating HCV.”
 Idenix, 

941 F.3d at 1156

. The patentee argued on appeal
 that the number of potential 2’-methyl-up nucleosides—
 and the amount of screening necessary to determine which
 ones treated HCV—was unimportant because “the jury
 could have [found] that all 2’-methyl-up” nucleosides
 treated HCV. See 

id. at 1159

 (emphasis in original). We
 rejected this argument because the evidence there did not
 support such a finding. 

Id.

 Accordingly, that the claim en-
 compassed “at least many, many thousands of 2’-methyl-up
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 24             TEVA PHARMACEUTICALS INTERNATIONAL GMBH v.
                                      ELI LILLY AND COMPANY


 nucleosides” that “need[ed] to be screened for HCV efficacy”
 rendered the amount of necessary experimentation high,
 thus weighing in favor of non-enablement. 

Id.

 Here, in
 contrast, it is undisputed that a reasonable jury could have
 found that all humanized anti-CGRP antagonist antibodies
 treat headache, thereby obviating any extensive screening
 to determine which ones do.
     In sum, given the nature of the asserted claims and the
 jury’s supportable findings, we conclude that JMOL of no
 enablement was improper.
                         CONCLUSION
     We have considered Lilly’s remaining arguments and
 find them unpersuasive. For the foregoing reasons, we re-
 verse the district court’s JMOL and remand for any neces-
 sary or appropriate further proceedings consistent with
 this opinion.
                REVERSED AND REMANDED
                            COSTS
 Costs to Teva.