Case: 19-1749    Document: 87    Page: 1     Filed: 10/13/2020




   United States Court of Appeals
       for the Federal Circuit
                  ______________________

                IMMUNEX CORPORATION,
                      Appellant

                            v.

       SANOFI-AVENTIS U.S. LLC, GENZYME
          CORPORATION, REGENERON
           PHARMACEUTICALS, INC.,
                Cross-Appellants

     ANDREI IANCU, UNDER SECRETARY OF
   COMMERCE FOR INTELLECTUAL PROPERTY
    AND DIRECTOR OF THE UNITED STATES
      PATENT AND TRADEMARK OFFICE,
                   Intervenor
             ______________________

                   2019-1749, 2019-1777
                  ______________________

     Appeals from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in Nos. IPR2017-
 01879, IPR2017-01884.
                  ______________________

                 Decided: October 13, 2020
                  ______________________

     ELDORA ELLISON, Sterne Kessler Goldstein & Fox,
 PLLC, Washington, DC, argued for appellant. Also repre-
 sented by DAVID HOLMAN, DAVID WILLIAM ROADCAP, JON
 WRIGHT.
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2            IMMUNEX CORPORATION     v. SANOFI-AVENTIS U.S. LLC




    LAUREN FORNAROTTO, McKool Smith, P.C., New York,
 NY, argued for cross-appellants. Also represented by JOHN
 FRANKLIN GARVISH, II, MATTHEW CAMERON, GEOFFREY
 SMITH, JOEL LANCE THOLLANDER, Austin, TX; ERIC
 SORENSEN HANSEN, MIKE MCKOOL, Dallas, TX; NOAH
 SAMUEL FRANK, GEORGE W. HICKS, JR., NATHAN S.
 MAMMEN, Kirkland & Ellis LLP, Washington, DC.

     FRANCES LYNCH, Office of the Solicitor, United States
 Patent and Trademark Office, Alexandria, VA, argued for
 intervenor. Also represented by SARAH E. CRAVEN, THOMAS
 W. KRAUSE, FARHEENA YASMEEN RASHEED.
                  ______________________

    Before PROST, Chief Judge, REYNA and TARANTO, Circuit
                           Judges.
 PROST, Chief Judge.
     This is a consolidated appeal from two Patent Trial and
 Appeal Board (“Board”) decisions in inter partes reviews
 (“IPRs”) of U.S. Patent No. 8,679,487 (“the ’487 patent”),
 owned by Immunex Corp. (“Immunex”). Sanofi-Aventis
 U.S. LLC, Genzyme Corp., and Regeneron Pharmaceuti-
 cals, Inc. (collectively, “Sanofi”) challenged the ’487 patent,
 which covers isolated human antibodies that bind the hu-
 man interleukin-4 receptor. The Board invalidated all
 challenged claims in one of the IPRs, No. IPR2017-01884.
 Immunex appeals, contesting the construction of the claim
 term “human antibodies.” In the other IPR, No. IPR2017-
 01879, involving a subset of the same claims, the Board did
 not invalidate the patents for reasons of inventorship.
 Sanofi appeals, contesting the Board’s inventorship deter-
 mination. We consolidated the cases in the nature of an
 appeal and a cross-appeal. For the reasons below, we agree
 with the Board’s claim construction in No. IPR2017-01884
 (here, “the appeal”). Accordingly, we affirm that invalidity
 decision. Because this leaves valid no claims at issue in the
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 IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC          3



 second IPR, we dismiss Sanofi’s inventorship appeal from
 No. IPR2017-01879 (here, the “cross-appeal”).
                        BACKGROUND
                               I
     The ’487 patent is directed to antibodies that bind to
 the human interleukin-4 (“IL-4”) receptor, the resulting in-
 hibition of which is significant for treating various inflam-
 matory disorders, such as arthritis, dermatitis, and
 asthma. See ’487 patent col. 3 ll. 15–31; J.A. 3–4.
     Claim 1 reads:
     An isolated human antibody that competes with a
     reference antibody for binding to human IL-4 inter-
     leukin-4 (IL-4) receptor, wherein the light chain of
     said reference antibody comprises the amino acid
     sequence of SEQ ID NO:10 and the heavy chain of
     said reference antibody comprises the amino acid
     sequence of SEQ ID NO:12.
 ’487 patent (emphasis added). This appeal concerns what
 “human antibody” means in this patent.
     First, the relevant science. Antibodies are proteins.
 Like all proteins, they are composed of numerous individ-
 ual amino acids chained together in a particular sequence.
 Antibodies are roughly Y-shaped, made of four chains—two
 “heavy” and two “light.” Each chain can be further divided
 into a “variable region” and a “constant region.” And each
 variable region contains three relatively small “comple-
 mentarity-determining regions” (CDRs) situated at the tips
 of the Y. The remainder of the variable regions are the
 “framework regions.”
     Particular antibody regions have particular biological
 implications. For instance, it is primarily the CDRs that
 give an antibody its ability to bind selectively to specific
 targets (i.e., antigens), despite making up just a sliver of
 its structure. See J.A. 1501, 7042–43. To that end, an
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4           IMMUNEX CORPORATION     v. SANOFI-AVENTIS U.S. LLC



 antibody’s exact amino acid sequence determines what the
 antibody binds to, which affects the antibody’s therapeutic
 usefulness. The amino acid sequence of an antibody also
 determines whether the human immune system recognizes
 and rejects it as “non-human.” Amino acid sequences that
 are human in origin—that is, sequences “consistent with
 the amino acid sequences of antibodies produced naturally
 by the human immune system,” see Appellant’s Br. 4—can
 avoid triggering immune responses.
     Early efforts at therapeutic antibody development
 started with mice. For example, researchers could inject a
 mouse with an antigen, the mouse would generate antibod-
 ies to the antigen, and those antibodies would be har-
 vested. In that case, the entire amino acid sequence was
 murine (i.e., from mice). These antibodies, disappointingly,
 tended to plague patients with “undesirable and harmful
 immune reactions.” See Appellant’s Br. 7–8. Too much of
 each antibody was “mouse” in origin, to the consternation
 of the human immune system.
     Through various techniques, the proportion of an anti-
 body that is recognized as “mouse” can be decreased. In
 “chimeric” antibodies, for instance, the constant regions
 tend to be human in origin, and the variable regions, in-
 cluding the CDRs, tend to be nonhuman—making the an-
 tibodies’ amino acid sequences mostly human in origin.
 Appellant’s Br. 8–9. In “humanized” antibodies, only the
 CDRs are nonhuman—the antibodies’ amino acid se-
 quences, including the portions responsible for immune re-
 action, are almost entirely human in origin. 1 Further, fully
 human antibodies can be made in which even the CDRs are
 human in origin.



     1   One of Immunex’s examples describes the amino
 acid sequences of a “chimeric” antibody as 66% human and
 a “humanized” antibody as 97% human. Appellant’s Br. 8.
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      Here, some of the disclosed embodiments are “partially
 human” and some are “completely human.” E.g., ’487 pa-
 tent col. 19 ll. 38–44, col. 21 ll. 6–14. Among the former,
 the specification’s embodiments specifically include hu-
 manized and chimeric antibodies.

col. 18 ll. 36–37,
 col. 19 ll. 21–37.
     The claim construction dispute is this: in the context of
 this patent, must a “human antibody” be entirely human?
 Or may it also be “partially human,” including “human-
 ized”?
                              II
      Amid infringement litigation, Sanofi filed three IPR pe-
 titions challenging claims 1–17 of the ’487 patent. Two
 were instituted.
     In one final written decision, the Board concluded that
 claims 1–17 were unpatentable as obvious over two refer-
 ences, Hart and Schering-Plough. Sanofi-Aventis v. Im-
 munex, No. IPR2017-01884, Paper 96, 

 (P.T.A.B. Feb. 14, 2019) (“Final Written Decision”).
     Hart describes a commercially available murine anti-
 body that purportedly meets all the limitations of claim 1—
 except that it is fully murine, not human at all. Final Writ-
 ten Decision, 

, at *7–8. But Schering-
 Plough teaches humanizing such murine antibodies by
 “grafting” their CDRs onto an otherwise fully human anti-
 body.

that the claims were ob-
 vious in light of the humanized antibody that would result
 from this combination. Further, Sanofi argued in a second
 obviousness ground that the gap between “humanized” and
 “fully human” could be closed using the teachings of a third
 reference, Hoogenboom. J.A. 1095. The Board reached
 only the first ground, finding that the “humanized” anti-
 body met its construction of “human antibody.” Final Writ-
 ten Decision, 

, at *9, *12. On appeal,
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6           IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC



 Immunex insists only that the Board erred in this construc-
 tion.
     In the second final written decision, the Board con-
 cluded that Sanofi had not shown by a preponderance of
 the evidence that claims 1–14, 16, and 17 were anticipated
 by one of Immunex’s own publications. Sanofi-Aventis v.
 Immunex, No. IPR2017-01879, Paper 88 (P.T.A.B. Feb. 14,
 2019). Sanofi appealed, contending that the Board erred in
 determining that the disclosure was not § 102(e) prior art
 “by another.” We consolidated Immunex’s appeal and
 Sanofi’s appeal in the nature of an appeal and a cross-ap-
 peal, respectively. See Order (July 10, 2019), ECF No. 21.
    We have jurisdiction under 28 U.S.C. § 1295(a)(4)(A).
                        DISCUSSION
                              I
     First, we consider the applicable claim construction
 standard in light of a post-briefing terminal disclaimer.
     After appellate briefing was complete, Immunex filed
 with the Patent and Trademark Office (“PTO”) a terminal
 disclaimer of its patent. The PTO promptly accepted it,
 and Immunex’s patent therefore expired on May 26, 2020,
 just over two months before oral argument.
      Immunex then filed a citation of supplemental author-
 ity under Federal Rule of Appellate Procedure 28(j), appris-
 ing us of (but not explaining the reason for) its terminal
 disclaimer and asking us to change the applicable claim
 construction standard. See Citation of Suppl. Authority
 (Apr. 10, 2020), ECF No. 66. Sanofi and the PTO insist
 that Immunex has waived the Phillips issue. We need not
 reach waiver, determining for the following reasons that
 the BRI standard applies.
     Today, in all newly filed IPRs, the Board applies the
 Phillips district-court claim construction standard.
 37 C.F.R § 42.100(b) (2020); Phillips v. AWH Corp.,
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 IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC           7



 

(Fed. Cir. 2005) (en banc). 2 But when Sanofi
 filed its IPRs, the Board applied this standard only to ex-
 pired patents. To unexpired patents, it applied the broad-
 est reasonable interpretation (“BRI”) standard. 37 C.F.R.
 § 42.100(b) (2016); In re CSB–Sys. Int’l, Inc., 

,
 1341–42 (Fed. Cir. 2016). Immunex, with its letter, now
 urges us to apply Phillips, citing Wasica Finance GmbH v.
 Continental Automotive Systems, Inc., 

, 1279
 (Fed. Cir. 2017), and In re CSB–System International,
 

. But unlike here, the patents in Wasica and
 CSB had expired before the Board’s decision.
     We have also applied the Phillips standard when a pa-
 tent expired on appeal. See PTO Resp. Letter (Apr. 30,
 2020), ECF No. 72 (citing Apple Inc. v. Andrea Elecs. Corp.,
 

, 707 (Fed. Cir. 2020)). But we do not read
 Andrea Electronics to mean that whenever a patent expires
 on appeal, at any time and for any reason, Phillips applies.
 In Andrea Electronics, the patent’s term expired as ex-
 pected. It was not cut short by a litigant’s terminal dis-
 claimer.    And, importantly, the expected expiration
 happened before appellate briefing began. The parties
 knew this at the outset, as the expiration date was part of
 the record before the Board, and were able to fully brief the
 consequences. Not so here, where the patentee shortened
 the term abruptly after the parties had already fully
 briefed claim construction under the BRI standard. 3



     2   See Changes to the Claim Construction Standard
 for Interpreting Claims in Trial Proceedings Before the Pa-
 tent Trial and Appeal Board, 83 Fed. Reg. 51,340 (Oct. 11,
 2018) (codified at 37 C.F.R. pt. 42). The new standard ap-
 plies only to petitions filed on or after November 13, 2018.
      3  Further, Immunex did not request further briefing
 on the implications of a possible pivot to Phillips. And be-
 yond noting that a district court has already more narrowly
 construed the claim term at issue (albeit not in a final
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8           IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC



     This court “shall review the decision from which an ap-
 peal is taken on the record before the Patent and Trade-
 mark Office.” 35 U.S.C. § 144. Our predecessor court has
 refused to consider terminal disclaimers filed after the
 Board’s decision. In re Thorington, 

, 533–34
 (CCPA 1969); In re Heyl, 

(CCPA 1967). In
 this situation, we do the same.
     Accordingly, in this case we will review the Board’s
 claim construction under the BRI standard.
                              II
     Next, we address the Board’s claim construction. Im-
 munex contends that the Board erred by construing the
 term “human antibody” to encompass not only “fully hu-
 man” but also “partially human” antibodies.
      Claim 1 of the ’487 patent recites a “human antibody.”
 The Board determined that the BRI of “human antibody”
 “includes both fully human and partially human antibod-
 ies.” Final Written Decision, 

, at *7. As
 relevant to its obviousness rejection, the Board’s construc-
 tion includes “humanized” antibodies.

*9. According
 to Immunex, however, “humanized” is not “human.” For
 the reasons below, we disagree with Immunex and agree
 with the Board.
                              A
     We review the Board’s claim construction de novo and
 any underlying factual findings for substantial evidence.
 Kaken Pharm. Co. v. Iancu, 

, 1350 (Fed. Cir.
 2020) (citing Teva Pharms. USA, Inc. v. Sandoz, Inc.,
 

(2015); 

). In this
 case, claim terms are given their “broadest reasonable con-
 struction in light of the specification of the patent.”


 judgment), it did not advance any argument that our re-
 view should come out differently under Phillips.
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 37 C.F.R. § 42.100(b) (2016); Cuozzo Speed Techs., LLC v.
 Lee, 

, 2142 (2016).
     We review the Board’s claim construction according to
 the Supreme Court’s decision in Teva. Accordingly, we re-
 view the Board’s evaluation of the intrinsic record de novo.
 See 

; Knowles Elecs. LLC v. Cirrus
 Logic, Inc., 

, 1361–62 (Fed. Cir. 2018). But
 “[w]e review underlying factual determinations concerning
 extrinsic evidence for substantial evidence.” In re Cuozzo
 Speed Techs., LLC, 

, 1279–80 (Fed. Cir.
 2015), aff’d sub nom. Cuozzo Speed Techs., LLC v. Lee,
 

(2016); 

–32; 

–62.
                              B
     First, we turn to the intrinsic record. Personalized Me-
 dia Commc’ns, LLC v. Apple Inc., 

, 1340
 (Fed. Cir. 2020) (“When construing claim terms, we first
 look to, and primarily rely on, the intrinsic evidence, in-
 cluding the claims themselves, the specification, and the
 prosecution history of the patent, which is usually disposi-
 tive.” (quoting Sunovion Pharms., Inc. v. Teva Pharms.
 USA, Inc., 

, 1276 (Fed. Cir. 2013))). As dis-
 cussed below, the intrinsic evidence supports the correct-
 ness of the Board’s construction.
                              1
     We begin claim construction by looking to the language
 of the claim itself. Allergan Sales, LLC v. Sandoz, Inc.,
 

, 1374 (Fed. Cir. 2019). But nothing in the
 claim’s language restricts “human antibodies” to those that
 are fully human. This is not surprising: antibodies, amid a
 rapidly evolving scientific background, are a frequent sub-
 ject of claim-construction disputes that stretch beyond
 plain meaning. E.g., Baxalta Inc. v. Genentech, Inc.,
 

, 1345–49 (Fed. Cir. 2020) (construing “anti-
 body”); UCB, Inc. v. Yeda Rsch. & Dev. Co., 

,
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 10           IMMUNEX CORPORATION     v. SANOFI-AVENTIS U.S. LLC



 1259–61 (Fed. Cir. 2016) (construing “monoclonal anti-
 body”); Biogen Idec, Inc. v. GlaxoSmithKline LLC, 

, 1095–97 (Fed. Cir. 2013) (construing “anti-CD20 an-
 tibody”). Nor is the claim context helpful, as the dependent
 claims provide no further guidance.
     Accordingly, we consult the rest of the intrinsic record.
 Indeed, the specification is key—it is “highly relevant to
 the claim construction analysis” and the “single best guide
 to the meaning of a disputed term.” 

(quoting Vitronics Corp. v. Conceptronic, Inc.,
 

, 1582 (Fed. Cir. 1996)); see also In re Trans-
 logic Tech., Inc., 

, 1256–58 (Fed. Cir. 2017)
 (endorsing Phillips “best practices” in the BRI context).
     Many patentees do expressly define “human antibody.”
 See, e.g., Abbott GbmH & Co. v. Centocor Ortho Biotech,
 Inc., 

, 247 (D. Mass. 2012) (noting ex-
 press definition of “human antibody”). Here, however, we
 are without an express definition. But the usage of “hu-
 man” throughout the specification confirms its breadth.
      The specification contrasts “partially human” with
 “fully” or “completely human.” E.g., ’487 patent col. 19
 ll. 41–44, col. 20 ll. 57–60, col. 21 ll. 1–2. For example, the
 specification states that “[a]ntibodies of the invention in-
 clude, but are not limited to, partially human (preferably
 fully human) monoclonal antibodies.”

col. 20
 ll. 57–60. And elsewhere, it notes that “[t]he desired anti-
 bodies are at least partially human, and preferably fully
 human.”

col. 19 ll. 41–44.
      Still further, the specification reads:
      A method for producing an antibody comprises im-
      munizing a non-human animal, such as a trans-
      genic mouse, with an IL-4R polypeptide, whereby
      antibodies directed against the IL-4R polypeptide
      are generated in said animal. Procedures have
      been developed for generating human antibodies in
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     non-human animals. The antibodies may be par-
     tially human, or preferably completely human.
 ’487 patent col. 19 ll. 38–44 (emphases added). Again, here
 the specification makes clear that “human antibodies” is a
 broad category encompassing both partially and com-
 pletely human antibodies. 4
     Immunex disagrees with this reading: it protests that
 the phrase “the antibodies,” as italicized above, refers not
 to “human antibodies”—one sentence back—but to “anti-
 bodies directed against the IL-4R polypeptide”—two sen-
 tences back. We are unpersuaded. Immunex’s proposed
 interpretation would contort the logical and grammatical
 reading of the passage.
    The specification also repeatedly clarifies that some
 “human” antibodies are “fully human”:
     Examples of antibodies produced by immunizing
     such transgenic mice are the human monoclonal
     antibodies designated 6-2 (described in example 6);
     12B5 (described in example 8); and MAbs 63, 1B7,
     5A1, and 27A1 (all described in example 9). Mono-
     clonal antibodies 6-2, 12B5, 63, 1B7, 5A1, and 27A1
     are fully human antibodies, and are capable of in-
     hibiting activity of both IL-4 and IL-13.



     4    Immunex, disagreeing that “fully” was necessary to
 convey an antibody’s “completely human” nature, quotes
 approvingly a district court’s remark in the accompanying
 litigation that “when one purchases . . . a German Shep-
 herd, one assumes, absent further context, that the seller
 will not deliver . . . a poodle-Shepherd mix.” Appellant’s
 Br. 24 (quoting J.A. 9035). But to the extent that canine
 metaphors are apt, more on the nose is that “brown dogs”
 plainly include “partially brown” dogs, such as a mostly
 brown dog with a white spot.
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 12          IMMUNEX CORPORATION      v. SANOFI-AVENTIS U.S. LLC



 ’487 patent col. 21 ll. 6–13 (emphases added); see also

 col. 43 ll. 26–27 (“[Antibody] 12B5 was determined to be an
 IgG1 antibody, and to be fully human.” (emphasis added)).
 If “human antibodies” were already understood to mean
 “fully human,” no clarification would be necessary. This
 usage confirms that a reader would take “human monoclo-
 nal antibodies” to be broader.
     Consistent with this usage, the abstract and the sum-
 mary each simply refer to “human” antibodies. See ’487 pa-
 tent Abstract (“Particular antibodies provided herein
 include human monoclonal antibodies generated by proce-
 dures involving immunization of transgenic mice. Such hu-
 man antibodies may be raised against human IL-4
 receptor.”);

col. 2 ll. 42–46 (“Particular antibodies pro-
 vided herein include human monoclonal antibodies gener-
 ated by procedures involving immunization of transgenic
 mice. Such human antibodies may be directed against hu-
 man IL-4 receptor, for example.”).
     Accordingly, the language of the specification confirms
 a broadest reasonable interpretation of “human antibodies”
 that includes those that are partially human—including
 “humanized” antibodies.
                                2
     Next, we turn to the prosecution history. The Board
 found the prosecution history to be “equivocal, at best.” Fi-
 nal Written Decision, 

, at *6. Immunex
 insists that the Board undervalued the prosecution history.
 Appellant’s Br. 32. We agree—here the prosecution history
 is relevant and informative. But it supports the Board’s
 construction.
    First, we note that Immunex used both “fully human”
 and “human” within the same claim set in another patent
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 application in the same family. 5 “[T]he prosecution of re-
 lated patents may be relevant to the construction of a given
 claim term.” Teva Pharms. USA, Inc. v. Sandoz, Inc.,
 

, 1343 n.5 (Fed. Cir. 2015). And here, Im-
 munex provides no convincing explanation for its simulta-
 neous use of the two terms beyond what is apparent: they
 are not interchangeable.
      Second, “there is a strong presumption against a claim
 construction that excludes a disclosed embodiment.” Nobel
 Biocare Servs. AG v. Instradent USA, Inc., 

,
 1381 (Fed. Cir. 2018) (quoting In re Katz Call Processing
 Pat. Litig., 

, 1324 (Fed. Cir. 2011)). We noted
 above that the specification’s embodiments include par-
 tially human antibodies—both humanized and chimeric.
 And the prosecution history here illustrates why the pre-
 sumption against their exclusion from the claims is not
 overcome.
     As initially filed, claim 1 recited simply “an isolated an-
 tibody.” J.A. 2409. The word “human” was added later, at
 the same time that dependent claim 11, which recited “a
 human, partially human, humanized, or chimeric anti-
 body,” was canceled. 6 J.A. 2233–34. Immunex does not


     5   One claim read: “An isolated antibody that com-
 petes for binding to human IL-4 receptor with a fully hu-
 man control antibody . . . .” J.A. 6086 (emphasis added). A
 dependent claim then recited: “The isolated antibody . . .
 wherein said isolated antibody is a human . . . antibody.”
 J.A. 6087 (emphasis added).
      6  Immunex insists that the Board incorrectly “per-
 ceived an overlap between claim terms [‘human’ and ‘par-
 tially human’] when there is no evidence supporting such
 overlap.” Appellant’s Br. 39. We are unconvinced. Indeed,
 most of the claim terms overlap. The list also included “hu-
 manized” and “chimeric”; these overlap with “partially hu-
 man.”
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 dispute that its originally filed claim covered humanized
 and chimeric embodiments as well as fully human ones.
     Immunex suggests instead that the amendment “sur-
 render[ed]” the partially human embodiments. E.g., Ap-
 pellant’s Br. 26; see also

36 
(arguing that Immunex
 “unambiguously amended the claims to remove antibodies
 that are not fully human”). We disagree. “Because the
 claim language does not require the exclusion of those em-
 bodiments, and there is no basis in the intrinsic record for
 excluding them,” Immunex “has not overcome [the] pre-
 sumption” against their exclusion. Nobel 
Biocare, 903 F.3d
 at 1381
; see also, e.g., 
Baxalta, 972 F.3d at 1348
 (“[D]isavowal must be clear and unmistakable.”).
     As the Board noted, “human” was added to overcome
 an anticipating reference that disclosed nonhuman murine
 antibodies—a far cry from “humanized” antibodies. Final
 Written Decision, 
2019 WL 643041
, at *5; Appellee’s
 Br. 45–46. 7
     We agree with the Board that nothing indicates that
 Immunex added “human” to limit the scope to fully human.
 There was no apparent need to do so in light of the rejec-
 tion, and no evidence that anyone understood Immunex to
 be casting aside subject matter that was not at issue. Final
 Written Decision, 
2019 WL 643041
, at *5–6.
     Immunex points out that the examiner subsequently
 issued a new obviousness rejection, combining Mosley with
 Jakobovits’s “fully human” antibodies. As Immunex ar-
 gues, the examiner must have understood human antibod-
 ies to mean only “fully human” antibodies because the
 examiner “repeatedly referred to ‘fully human’ antibodies
 while describing Jakobovits.” See Appellant’s Br. 34. But
 this argument shows only that “fully human” antibodies


      7 Immunex did not dispute this characterization of
 the Mosley rejection by Sanofi or the Board.
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 are “human,” which is undisputed. Further, given that
 Jakobovits itself uses the term “fully human” to describe its
 own disclosure, 8 we decline to treat as significant the ex-
 aminer’s adoption of that term in making the rejection.
 Nothing supports reading Immunex’s claim as limited to
 fully human antibodies just because the particular combi-
 nation of prior art used to reject it included antibodies that
 were fully human.
     Third, in a post-amendment office action, the examiner
 expressly wrote that the amended “human” antibodies en-
 compassed “humanized” antibodies. J.A. 2211. Immunex
 suggests without substantiation that this was a “copy and
 paste error.” See Appellant’s Br. 36. But if so, Immunex
 made no effort to disabuse the examiner of this under-
 standing. And, while hardly dispositive, this uncontested
 characterization is consistent with the Board’s construc-
 tion.
    Accordingly, the prosecution history also supports the
 Board’s construction.
                               C
    Next, we address the role of extrinsic evidence in the
 Board’s construction.
      Immunex argues that the Board “failed to establish
 how a person of ordinary skill in the art would have under-
 stood the term ‘human antibody.’” Appellant’s Br. 47. That
 is, Immunex contends that the Board did not adequately
 consult its extrinsic evidence—its experts’ testimony, prod-
 uct catalogs, and a selection of journal articles—to estab-
 lish whether “human antibody” had an established



     8   Jakobovits begins: “The ability to produce a diverse
 repertoire of fully human monoclonal antibodies (mAbs)
 may have significant applications to human therapy.”
 J.A. 6452.
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 meaning to a person of ordinary skill in the art, independ-
 ent of the specification. We disagree.
      It is true that we seek the meaning of claim terms from
 the perspective of the person of ordinary skill in the art.
 The key, however, is that we look to how that person would
 have understood a term in view of the specification. See,
 e.g., In re Am. Acad. of Sci. Tech Ctr., 
367 F.3d 1359
, 1364
 (Fed. Cir. 2004) (“[C]laims are to be given their broadest
 reasonable interpretation consistent with the specification,
 and claim language should be read in light of the specifica-
 tion as it would be interpreted by one of ordinary skill in
 the art.” (cleaned up)).
      While extrinsic evidence may sometimes illuminate a
 well-understood technical meaning, 
Teva, 574 U.S.
 at 331
–32, that does not mean that litigants can introduce
 ambiguity in a way that disregards language usage in the
 patent itself. The patent drafter controls the content of the
 specification, writes the claims, and responds to office ac-
 tions. The drafter, then, is in the best position to anticipate
 ambiguity or questions of scope and to write the patent ac-
 cordingly. Indeed, we give the intrinsic evidence “priority,”
 see, e.g., 
Knowles, 883 F.3d at 1361
–62, over extrinsic evi-
 dence with which it is “inconsistent,” Tempo Lighting, Inc.
 v. Tivoli, LLC, 
742 F.3d 973
, 977 (Fed. Cir. 2014) (emphasis
 omitted); see, e.g., Celgene Corp. v. Peter, 
931 F.3d 1342
,
 1350–51 (Fed. Cir. 2019) (holding that the Board “was cor-
 rect to not allow the extrinsic evidence, including expert
 testimony, to trump the persuasive intrinsic evidence”
 (cleaned up)).
      Immunex’s extrinsic evidence included the testimony
 of its two experts, who discussed their views in light of a
 handful of journal articles, catalogs, and other documents.
 The Board cited this evidence, and clearly considered it.
 Final Written Decision, 
2019 WL 643041
, at *6–7. But the
 Board found nothing credible to call its interpretation into
 question. To the contrary, it credited a prior art reference
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 IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC         17



 and expert testimony that were squarely consistent with
 “humanized” being understood as a subset of “human.” See

 id. at 
*6 (citing J.A. 5099–100 ¶¶ 9–10 as “Ex. 1477”). 9 To
 the extent that the Board credited this evidence, and there-
 fore necessarily rejected Immunex’s conflicting evidence,
 we owe it deference. See 
Teva, 574 U.S. at 331
–32.
     At any rate, the intrinsic evidence here decides the is-
 sue. Extrinsic evidence may be of assistance if the intrinsic
 record is equivocal, leaving us looking for further guidance.
 See Helmsderfer v. Bobrick Washroom Equip., Inc.,
 
527 F.3d 1379
, 1382 (Fed. Cir. 2008). But here, the mean-
 ing of “human antibody” as discerned from the intrinsic ev-
 idence squarely conflicts with the meaning that Immunex
 would distill from its selected extrinsic evidence.
 Id. (“A
 court may 
look to extrinsic evidence so long as the extrinsic
 evidence does not contradict the meaning otherwise appar-
 ent from the intrinsic record.”). Accordingly, the intrinsic
 record trumps.
                              D
     Finally, we turn to the matter of the Board’s departure
 from an earlier court’s claim construction.
     In litigation that prompted this IPR, a district court
 construed “human” to mean “fully human” only. See Im-
 munex Corp. v. Sanofi, No. CV 17-02613 SJO, 
2018 WL


     9 
  Immunex belittles this reference, Riechmann, pub-
 lished in 1988 in the prominent journal Nature, as being
 “long-outdated” by 2001. Appellant’s Br. 54–55. Nonethe-
 less, Riechmann, being cited in the specification, is intrin-
 sic evidence. See V-Formation, Inc. v. Benetton Grp. SpA,
 
401 F.3d 1307
, 1310–11 (Fed. Cir. 2005). Immunex does
 not contest that Riechmann uses “human” to describe anti-
 bodies that are other than fully human. Yet Immunex was
 apparently untroubled by Riechmann’s nomenclature
 when drafting its patent.
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 6252460, at *12–14 (C.D. Cal. Aug. 24, 2018). That claim
 construction order issued two months before the oral hear-
 ing in this IPR, and the parties discussed it in their briefing
 and at oral argument before the Board.
     The Board did not adopt the district court’s construc-
 tion. After conducting a full analysis of the parties’ argu-
 ments, the Board concluded that it reached a different
 interpretation “based on the broader applicable case law.”
 Final Written Decision, 
2019 WL 643041
, at *7.
     Immunex chides the Board for not explaining more
 fully its departure from the district court’s narrower Phil-
 lips-based construction. Citing Power Integrations, Inc. v.
 Lee, 
797 F.3d 1318
, 1326 (Fed. Cir. 2015), Immunex con-
 tends that the Board must explain in detail why, under a
 broader legal standard, it reaches a broader construction
 than a district court does.
      The Board’s misstep in Power Integrations, however,
 was not merely failing to explain the difference between a
 Phillips construction and the BRI. Rather, the Board there
 both “failed to acknowledge the district court’s claim con-
 struction” and “devoted a substantial portion of its analy-
 sis” to an issue not raised by the parties, focusing on a “red
 herring” and failing to adequately address the substance of
 the patentee’s primary argument.
 

1324–25; 
see also

 

1323 
(stating that the Board “fundamentally miscon-
 strued [the] principal claim construction argument”). In-
 deed, the problem was not that the Board’s construction
 was broader. Rather, the Board had left unaddressed a
 specific interpretive aspect of the claim term upon which
 its anticipation determination was based, stymying review.
 See
 id. at 
1325 (concluding that the Board’s opinion “pro-
 vides . . . an inadequate predicate upon which to evaluate
 its decision to reject claim 1 . . . as anticipated”).
     Regardless, in Power Integrations we reiterated that
 the Board “is not generally bound by a previous judicial
 construction of a claim term.”
 Id. at 
1326; see also Mayne
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 IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC         19



 Pharma Int’l Pty. Ltd. v. Merck Sharp & Dohme Corp.,
 
927 F.3d 1232
, 1242 (Fed. Cir. 2019) (“[W]e are not per-
 suaded that the Board erred in discounting the district
 court’s construction because the court construed the claims
 under the narrower, Phillips standard.”). And we empha-
 sized that the Board need not “in all cases assess a previous
 judicial interpretation of a disputed claim term.” Power In-
 
tegrations, 797 F.3d at 1327
. Rather, we require the Board
 to provide “reasoning in sufficient detail to permit mean-
 ingful appellate review.”
 Id. And the Board’s 
opinion was
 sufficiently detailed to permit meaningful appellate re-
 view. We conclude that the Board did not err by not saying
 more.
                             ***
     In summary, the Board’s construction was correct. Ac-
 cordingly, we affirm the Board’s invalidity judgment pred-
 icated on that claim construction.
                              III
     Last, we turn to Sanofi’s cross-appeal. Sanofi had al-
 leged in its petition for IPR2017-01879 that certain claims
 of the ’487 patent were anticipated by the disclosure of
 mAb 6-2, an isolated human antibody, in an earlier publi-
 cation of Immunex’s. That reference, U.S. Patent Applica-
 tion Publication No. 2002/0002132 (“the ’132 publication”),
 is within the same prosecution family as the ’487 patent.
 But Sanofi contested the listed inventorship, insisting that
 mAb 6-2 was invented “by another”—namely, by research
 technician Norman Boiani, not the ’487 patent’s inven-
 tors—and therefore that the this disclosure was prior art
 under § 102(e). The Board disagreed, concluding that
 Mr. Boiani was not an inventor of mAb 6-2. Sanofi cross-
 appeals this determination.
     Because we affirm the Board’s invalidity judgment in
 the other IPR, which implicates the same claims, it is un-
 necessary to reach this issue.
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 20         IMMUNEX CORPORATION    v. SANOFI-AVENTIS U.S. LLC



                        CONCLUSION
      We have considered the parties’ other arguments but
 find them unpersuasive. 10 For the foregoing reasons, we
 affirm the Board’s judgment holding the ’487 patent invalid
 as obvious. We dismiss the cross-appeal.
      AFFIRMED-IN-PART, DISMISSED-IN-PART




      10 Additionally, in its reply brief, Immunex raised an
 Appointments Clause challenge to the Board’s authority,
 citing Arthrex and asking us to vacate and remand accord-
 ingly. See Arthrex, Inc. v. Smith & Nephew, Inc., 
941 F.3d
 1320 
(Fed. Cir. 2019). But under Customedia Technologies,
 LLC v. Dish Network Corp., 
941 F.3d 1173
, 1174 (Fed. Cir.
 2019), failure to raise this challenge in the opening brief
 constitutes forfeiture.