Case: 19-1527    Document: 59     Page: 1   Filed: 08/27/2020




   United States Court of Appeals
       for the Federal Circuit
                  ______________________

           BAXALTA INC., BAXALTA GMBH,
                Plaintiffs-Appellants

                             v.

                  GENENTECH, INC.,
                   Defendant-Appellee

       CHUGAI PHARMACEUTICAL CO. LTD.,
                    Defendant
              ______________________

                        2019-1527
                  ______________________

     Appeal from the United States District Court for the
 District of Delaware in No. 1:17-cv-00509-TBD, Circuit
 Judge Timothy B. Dyk.
                 ______________________

                 Decided: August 27, 2020
                 ______________________

     WILLIAM R. PETERSON, Morgan, Lewis & Bockius LLP,
 Houston, TX, argued for plaintiffs-appellants. Also repre-
 sented by NATALIE A. BENNETT, Washington, DC; MICHAEL
 J. ABERNATHY, CHRISTOPHER JOHN BETTI, MARIA DOUKAS,
 KARON NICOLE FOWLER, SANJAY K. MURTHY, Chicago, IL;
 JULIE S. GOLDEMBERG, Philadelphia, PA.

    ERIC ALAN STONE, Paul, Weiss, Rifkind, Wharton &
 Garrison LLP, New York, NY, argued for defendant-
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 2                            BAXALTA INC. v. GENENTECH, INC.




 appellee.  Also represented by ALEXANDER ATKINS,
 MARISSA DORAN, JENNIFER GORDON, NICHOLAS P.
 GROOMBRIDGE, NAZ WEHRLI, JOSEPHINE YOUNG; DAVID
 COLE, KENNETH A. GALLO, Washington, DC.
                ______________________

     Before MOORE, PLAGER, AND WALLACH, Circuit Judges. 1
 MOORE, Circuit Judge.
     Baxalta Inc. sued Genentech, Inc. and Chugai Pharma-
 ceutical Co. Ltd., 2 alleging infringement of claims 1, 4, 17,
 and 19 of U.S. Patent No. 7,033,590. On December 3, 2018,
 the United States District Court for the District of Dela-
 ware issued a claim construction order, construing the
 terms “antibody” and “antibody fragment.” Following the
 claim construction order, the parties stipulated to non-in-
 fringement of the asserted claims. The district court en-
 tered judgment based on its claim construction order and
 the parties’ stipulation. Baxalta appeals the district court’s
 judgment, arguing the district court’s claim constructions
 were erroneous. We have jurisdiction under 28 U.S.C.
 § 1295(a)(1).
     Because the district court erred in construing the terms
 “antibody” and “antibody fragment,” we vacate the district
 court’s judgment of non-infringement and remand.
                     I.     BACKGROUND
    Baxalta sued Genentech, asserting that Genentech’s
 Hemlibra® (emicizumb-kxwh) product used to treat the



       1 Judge Stoll recused and took no part in this deci-
 sion. Judge Plager replaced Judge Stoll on the panel fol-
 lowing oral argument.
     2   Chugai was later voluntarily dismissed from the
 lawsuit pursuant to a joint stipulation between Chugai and
 Baxalta. J.A. 15946–47.
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 BAXALTA INC. v. GENENTECH, INC.                             3



 blood clotting disorder hemophilia infringes claims 1, 4, 17,
 and 19 of the ’590 patent. Blood clotting occurs in the body
 through a series of enzymatic activations known as the “co-
 agulation cascade.” ’590 patent at 1:7–10. One “key step”
 in the cascade is when an enzyme known as activated clot-
 ting factor VIII (FVIIIa) complexes with another enzyme
 known as activated clotting factor IX (FIXa) to form a com-
 plex that then activates factor X (FX). ’590 patent at
 1:17–19. Hemophilia A is a particular form of hemophilia
 where the activity of factor VIII is functionally absent,
 thereby impeding the coagulation cascade. This can occur
 in some Hemophilia A patients because they develop factor
 VIII inhibitors (i.e., antibodies against factor VIII), which
 hinder the effectiveness of factor VIII preparations admin-
 istered as treatments. ’590 patent at 1:24–32. The ’590
 patent relates to preparations used to treat hemophilia pa-
 tients who have developed factor VIII inhibitors. ’590 pa-
 tent at 2:25–29. The preparations comprise antibodies or
 antibody fragments that bind to factor IX or factor IXa to
 increase procoagulant activity of factor IXa to compensate
 for the decreased factor VIII activity. See, e.g., ’590 patent
 at 2:29–34. Independent claim 1 and dependent claims 4
 and 19 are illustrative and recite:
     1. An isolated antibody or antibody fragment
     thereof that binds Factor IX or Factor IXa and in-
     creases the procoagulant activity of Factor IXa.
     4. The antibody or antibody fragment according to
     claim 1, wherein said antibody or antibody frag-
     ment is selected from the group consisting of a
     monoclonal antibody, a chimeric antibody, a hu-
     manized antibody, a single chain antibody, a
     bispecific antibody, a diabody, and di-, oligo- or
     multimers thereof.
     19. The antibody or antibody fragment according to
     claim 4, wherein the antibody is a humanized anti-
     body.
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 4                            BAXALTA INC. v. GENENTECH, INC.




     The parties disputed the construction of the terms “an-
 tibody” and “antibody fragment,” among other terms not at
 issue on appeal. Generally, antibodies are Y-shaped struc-
 tures comprising two heavy chains (H chains) and two light
 chains (L chains). An antibody that has two identical H
 chains and two identical L chains is called “monospecific”
 because each H-L chain pair binds the same antigen.
 Bispecific antibodies, like Genentech’s product Hemlibra®
 (emicizumb-kxwh), have different heavy chains and/or dif-
 ferent light chains, allowing them to bind two different an-
 tigens. Baxalta argued “antibody” should be construed as
 “[a] molecule having a specific amino acid sequence com-
 prising two heavy chains (H chains) and two light chains
 (L chains).” Genentech argued “antibody” should instead
 be construed as “[a]n immunoglobulin molecule, having a
 specific amino acid sequence that only binds to the antigen
 that induced its synthesis or very similar antigens, consist-
 ing of two identical heavy chains (H chains) and two iden-
 tical light chains (L chains).”
      The district court determined that “the term antibody
 standing alone without other structural terms can have dif-
 ferent meanings to those skilled in the art,” and that both
 Baxalta’s and Genentech’s proposed constructions were ac-
 ceptable definitions. Baxalta Inc. v. Genentech, Inc.,
 No. 17-509, 2018 WL 6304351, at *4 (D. Del. Dec. 3, 2018).
 It determined, however, that the patentee “chose [Genen-
 tech’s] narrower definition” by expressly defining antibod-
 ies in column 5 of the patent, which states:
     Antibodies are immunoglobulin molecules having a
     specific amino acid sequence which only bind to an-
     tigens that induce their synthesis (or its immuno-
     gen, respectively) or to antigens (or immunogens)
     which are very similar to the former. Each immu-
     noglobulin molecule consists of two types of poly-
     peptide chains. Each molecule consists of large,
     identical heavy chains (H chains) and two light,
     also identical chains (L chains).
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 BAXALTA INC. v. GENENTECH, INC.                             5



 Id. at *5 (quoting ’590 patent at 5:56–63).
      Although the district court recognized that the ’590 pa-
 tent claims and discloses “bispecific antibodies, which do
 not have identical heavy and light chains,” and IgM and
 IgA antibodies, which “can have more than two heavy
 chains and more than two light chains,” it determined that
 these claimed embodiments were “antibody derivatives” ra-
 ther than “antibodies.” Id. at *5–6. The district court like-
 wise dismissed the “inconsisten[cy]” between Genentech’s
 definition of “antibody” and “at least dependent claims 4
 and 19” as insufficient to overcome what it considered to be
 the definitional language of column 5. Id. at *11. The dis-
 trict court therefore adopted Genentech’s construction,
 construing “antibody” as “an immunoglobulin molecule,
 having a specific amino acid sequence that only binds to
 the antigen that induced its synthesis or very similar anti-
 gens, consisting of two identical heavy chains (H chains)
 and two identical light chains (L chains).” Id. at *12.
     To support its construction, the district court cited an
 amendment Baxalta made during prosecution of the
 ’590 patent. Original claim 1 recited “[a]n antibody or an-
 tibody derivative against factor IX/factor IXa which in-
 creases the procoagulant activity of FIXa.” J.A. 15961.
 Original dependent claim 4 recited a list of “antibod[ies] or
 antibody derivative[s] according to claim 1” including “chi-
 meric antibodies, humanized antibodies, single chain anti-
 bodies, bispecific antibodies, diabodies and di-, oligo- or
 multimers thereof.” Id. During prosecution, the patent ex-
 aminer rejected the term “antibody derivatives” as not en-
 abled for “any antibody derivative against factor IX/factor
 IXa which increases the procoagulant activity of FIXa in
 claim 1” or any one of the enumerated list in dependent
 claim 4. J.A. 15987, 16008. Based on the examiner’s sug-
 gestion, the patentee amended the claims to recite “anti-
 body fragment” in place of “antibody derivative” and the
 examiner removed the enablement rejection. The district
 court determined that this amendment amounted to a
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 6                            BAXALTA INC. v. GENENTECH, INC.




 disclaimer of antibody derivatives “including bispecific an-
 tibodies, except antibody fragments.” Baxalta, 2018 WL
 6304351, at *7–8 (emphasis in original).
      The parties also disputed the construction of “antibody
 fragment.” Baxalta proposed that the term be construed as
 “[a] portion of a molecule having a specific amino acid se-
 quence comprising two heavy chains (H chains) and two
 light chains (L chains).” Id. at *12. Genentech argued it
 should instead be construed as “[a] fragment of an antibody
 which partially or completely lacks the constant region; the
 term ‘antibody fragment’ excludes all other forms of anti-
 body derivatives.” Id. The district court, relying on a por-
 tion of the written description reciting that “antibody
 fragments . . . partially or completely lack the constant re-
 gion” and identifying examples of fragments (Fv, Fab, Fab'
 [and] F(ab)'2), construed “antibody fragment” as “a frag-
 ment of an antibody which partially or completely lacks the
 constant region; the term ‘antibody fragment’ excludes
 bispecific antibodies.” Id. at *12–13 (citing ’590 patent at
 6:20–21).
     Based on the district court’s constructions, the parties
 stipulated to non-infringement of the asserted claims of the
 ’590 patent. The district court entered final judgment of
 non-infringement of claims 1, 4, 17, and 19. Baxalta ap-
 peals, arguing that the district court erroneously construed
 the terms “antibody” and “antibody fragment.”
                      II.   DISCUSSION
     We review a district court’s claim construction de novo
 “[w]here, as here, the intrinsic evidence alone determines
 the proper claim construction.” Allergan Sales, LLC v.
 Sandoz, Inc., 935 F.3d 1370, 1373 (Fed. Cir. 2019) (citing
 Teva Pharm. USA, Inc. v. Sandoz, Inc., 574 U.S. 318, 332–
 33 (2015)). “The words of a claim are generally given their
 ordinary and customary meaning as understood by a per-
 son of ordinary skill in the art when read in the context of
 the specification and prosecution history.” Thorner v. Sony
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 BAXALTA INC. v. GENENTECH, INC.                               7



 Comput. Entm’t Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir.
 2012).
                         A. “Antibody”
             i.     The Claims of the ’590 Patent
     Claim 1 of the ’590 patent recites “[a]n isolated anti-
 body or antibody fragment thereof that binds Factor IX or
 Factor IXa and increases the procoagulant activity of Fac-
 tor IXa.” Therefore, contrary to the district court’s con-
 struction, nothing in the plain language of claim 1 limits
 the term “antibody” to a specific antibody consisting of two
 identical heavy chains and two identical light chains or an
 antibody that only binds the antigen that induced its syn-
 thesis or very similar antigens.
     The dependent claims confirm that “antibody” is not so
 limited. For example, dependent claim 4, recites “[t]he an-
 tibody or antibody fragment according to claim 1, wherein
 said antibody or antibody fragment is selected from the
 group consisting of . . . a chimeric antibody, a humanized
 antibody, . . . [and] a bispecific antibody.” Each of these
 claimed “antibodies” falls outside of the district court’s con-
 struction because each does not “only bind[] to the antigen
 that induced its synthesis or very similar antigens.” 3 A


     3   The ’590 patent explains that a humanized anti-
 body has a structure of a human antibody but combines
 non-human antibody portions, such as the complement de-
 termining regions (CDRs), with human antibody portions.
 ’590 patent at 6:50–7:1. It explains that a chimeric anti-
 body differs from a humanized antibody in that it com-
 prises the entire variable regions of non-human origin in
 combination with human constant regions. Id. Finally, it
 explains that a bispecific antibody has “two different bind-
 ing specificities within one single molecule,” i.e., it can bind
 two different antigens. Id. at 7:32–38. It is undisputed
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 8                            BAXALTA INC. v. GENENTECH, INC.




 “bispecific antibody” also does not satisfy the district
 court’s construction of “antibody” because a bispecific anti-
 body does not consist of two identical H chains and two
 identical L chains. Dependent claim 19 further limits
 claims 1 and 4 by claiming that the “antibody is a human-
 ized antibody,” which again does not fall within the district
 court’s construction of “antibody.”
     The district court’s construction which excludes these
 explicitly claimed embodiments is inconsistent with the
 plain language of the claims. 4 See Intellectual Ventures I
 LLC v. T-Mobile USA, Inc., 902 F.3d 1372, 1378 (Fed. Cir.
 2018); see also Ortho-McNeil Pharm., Inc. v. Mylan Labs.,
 Inc., 520 F.3d 1358, 1362 (Fed. Cir. 2008) (rejecting a con-
 struction that would “render several dependent claims
 meaningless”).




 that humanized antibodies, chimeric antibodies, and
 bispecific antibodies fall outside the district court’s con-
 struction. See Genentech Resp. Br. at 1, 53; Baxalta Op.
 Br. at 12.
     4    Baxalta argues that the district court’s claim con-
 struction is also inconsistent with dependent claims 7, 9,
 11, 18, 21, and 22 because they require synthetic produc-
 tion methods that do not “only bind[] to the antigen that
 induced its synthesis or very similar antigens.” Baxalta
 Op. Br. at 31–32. Baxalta also argues that the district
 court’s construction excludes claimed embodiments in
 claims 3 and 20, which recite that the antibody is an “IgG,
 IgM, IgA or IgE antibody.” Genentech agrees that IgM and
 IgA antibodies do not necessarily meet the district court’s
 construction requiring that the antibody consist of two
 identical H chains and two identical L chains. Genentech
 Resp. Br. at 9, 36. We note that when a construction such
 as this is inconsistent with the plain language of the claims
 and the written description, it is incorrect.
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 BAXALTA INC. v. GENENTECH, INC.                             9



     The district court rejected this inconsistency, suggest-
 ing that the proper result here is “invalidation of the incon-
 sistent claims rather than an expansion of the independent
 claims.” Baxalta, 2018 WL 6304351, at *11. Similarly,
 Genentech invites us to assume that the examiner simply
 overlooked at least these dependent claim limitations when
 he allowed the claims. See Genentech Resp. Br. at 53 and
 Baxalta Inc. v. Genentech, Inc., No. 19-1527, Oral Arg. at
 34:44–35:12,        available        at       http://oralargu-
 ments.cafc.uscourts.gov/default.aspx?fl=2019-1527.mp3
 (counsel for Genentech explaining “we don’t have an an-
 swer to why [bispecific antibodies are] there except that
 they stood rejected and somehow got allowed”). Genentech
 argues that because the patent defines the term “antibody”
 in column 5, we should invalidate all dependent claims
 which would not be consistent with that definition such as
 claims 4 and 19. We do not agree. The plain language of
 these dependent claims weighs heavily in favor of adopting
 Baxalta’s broader claim construction. And as in Intellec-
 tual Ventures I, we reject the district court’s construction
 which renders dependent claims invalid. 902 F.3d at 1378.
    ii.    The Written Description of the ’590 Patent
     Under the heading “Antibodies and Antibody Deriva-
 tives,” the patentee explains:
     Antibodies are immunoglobulin molecules having a
     specific amino acid sequence which only bind to an-
     tigens that induce their synthesis (or its immuno-
     gen, respectively) or to antigens (or immunogens)
     which are very similar to the former. Each immu-
     noglobulin molecule consists of two types of poly-
     peptide chains. Each molecule consists of large,
     identical heavy chains (H chains) and two light,
     also identical chains (L chains).
 ’590 patent at 5:56–65. The district court determined that
 this portion of the written description defined the term “an-
 tibody.” While this is a plausible reading of the excerpt in
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 10                            BAXALTA INC. v. GENENTECH, INC.




 isolation, claim construction requires that we “consider the
 specification as a whole, and [] read all portions of the writ-
 ten description, if possible, in a manner that renders the
 patent internally consistent.” Budde v. Harley-Davidson,
 Inc., 250 F.3d 1369, 1379–80 (Fed. Cir. 2001). When con-
 sidered in the context of the remainder of the written de-
 scription and the claims, we read the excerpt in column 5
 as a generalized introduction to antibodies rather than as
 a definitional statement. We also note that these general
 statements do not include terms we have held to be limiting
 in other contexts such as “the present invention includes .
 . .” or “the present invention is . . .” or “all embodiments of
 the present invention are . . . .” Luminara Worldwide, LLC
 v. Liown Elecs. Co., 814 F.3d 1343, 1353 (Fed. Cir. 2016).
      Beyond this general description in column 5, the writ-
 ten description provides specific disclosures regarding
 bispecific, chimeric, and humanized antibodies and meth-
 ods of production thereof, all of which do not comport with
 the district court’s construction. For example, the written
 description explains that “[t]he inventive antibodies and
 antibody derivatives and organic compounds derived there
 from comprise . . . bispecific antibodies.” ’590 patent at
 6:1–6. Both parties agree “bispecific antibodies” do not con-
 sist of two identical H chains and two identical L chains
 and thus fall outside the district court’s construction. See,
 e.g., Baxalta Op. Br. at 30 n.16; Genentech Resp. Br at 1.
 The written description further discloses that “antibodies
 and antibody derivatives may also include . . . ‘technically
 modified antibodies’ such as . . . chimeric or humanized an-
 tibodies . . . . In these technically modified antibodies, e.g.,
 a part or parts of the light and/or heavy chain may be sub-
 stituted.” ’590 patent at 6:15–24. And the written descrip-
 tion explains that “[t]he antibodies of the present invention
 can be prepared by methods known from the prior art, e.g.
 by conventional hybridoma techniques, or by means of
 phage display gene libraries, immunoglobulin chain shuf-
 fling or humanizing techniques.” Id. at 7:65–8:3 (emphasis
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 BAXALTA INC. v. GENENTECH, INC.                           11



 added). The written description, therefore, discloses syn-
 thetic techniques for preparing antibodies such as human-
 ized or chimeric antibodies, which are inconsistent with the
 district court’s claim construction requirement that the an-
 tibody “only binds to the antigen that induced its synthesis
 or very similar antigens.” Recognizing that these disclosed
 techniques for preparing the claimed antibodies would re-
 sult in antibodies excluded by the district court’s construc-
 tion, Genentech’s response was “I hesitate to say that that’s
 a typo.” Baxalta, No. 19-1527 Oral Arg. at 37:02–38:26.
      Genentech does not dispute that the written descrip-
 tion discloses antibodies that fall outside the district
 court’s construction, but rather argues that “there is no le-
 gal problem with a claim construction that excludes certain
 disclosed embodiments, where the specification otherwise
 supports that construction.” Genentech Resp. Br. at 1,
 60–61. To adopt Genentech’s construction, we would need
 to invalidate several dependent claims, which according to
 Genentech, the examiner overlooked in allowing, and to
 conclude that preparation techniques for the claimed anti-
 bodies included in the written description were disclosed in
 error. See Baxalta, No. 19-1527 Oral Arg. at 31:37–32:26
 (counsel for Genentech conceding that “[claim 19] and
 claim 4 are inconsistent with the notion that column 5 is a
 definition of ‘antibody’”). As discussed, column 5 is not
 definitional, and the remainder of the written description
 and claims do not support the district court’s construction.
 The claim construction excluding these disclosed and
 claimed embodiments is therefore incorrect.
    iii.   The Prosecution History of the ’590 Patent
     The prosecution history does not, as the district court
 suggests, “confirm[] the specification’s definition of anti-
 body.” Baxalta, 2018 WL 6304351, at *7. We have recog-
 nized that the prosecution history “often lacks the clarity
 of the specification and thus is less useful for claim con-
 struction purposes.” Phillips v. AWH Corp., 415 F.3d 1303,
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 12                           BAXALTA INC. v. GENENTECH, INC.




 1317 (Fed. Cir. 2005) (en banc). While a patentee cannot
 recapture specific constructions disclaimed during patent
 prosecution either through amendment or argument, we do
 not apply the doctrine of prosecution history disclaimer
 where the alleged disavowal is less than clear. Avid Tech.,
 Inc. v. Harmonic, Inc., 812 F.3d 1040, 1045 (Fed. Cir. 2016).
      The district court’s analysis centered around the pa-
 tentee’s amendment substituting the term “antibody frag-
 ment” for “antibody derivative,” at the examiner’s
 suggestion, to overcome an enablement rejection. See
 J.A. 15987, 16008, 16012, 16017–21. Based on its previous
 definition of “antibody derivatives” as “antibodies within
 the column 5 definition that had been altered in some sig-
 nificant way,” e.g., bispecific antibodies, Baxalta, 2018 WL
 6304351, at *6–7, the district court determined that the
 amendment from “antibody derivative” to “antibody frag-
 ment” amounted to a disclaimer of antibody derivatives “in-
 cluding bispecific antibodies, except antibody fragments.”
 Id. at *7–8 (emphasis in original). Because we reject the
 premise that the excerpt of column 5 is definitional, and do
 not view the prosecution history as sufficiently clear and
 unmistakable, we conclude that the prosecution history is
 insufficient to overcome the meaning of “antibody” we dis-
 cern from the claims and the written description.
     First, there are no clear statements in the prosecution
 history regarding what scope, if any, was given up when
 the patentee substituted “antibody fragment” for “antibody
 derivative.” “[I]n order for prosecution disclaimer to at-
 tach, the disavowal must be both clear and unmistakable.”
 3M Innovative Properties Co. v. Tredegar Corp., 725 F.3d
 1315, 1325 (Fed. Cir. 2013). Both parties agree that the
 term “antibody derivative” is not a term that is commonly
 used in the art. Baxalta, 2018 WL 6304351, at *6. It is
 plausible, therefore, given the ambiguity regarding this
 amendment, that the patentee was substituting a known
 term at the suggestion of the examiner for a less commonly
 used term in the art. In fact, the written description
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 BAXALTA INC. v. GENENTECH, INC.                           13



 appears to use them almost interchangeably. See, e.g.,
 ’590 patent at 6:20–22 (identifying Fv, Fab, Fab', and
 F(ab)’2 as examples of antibody fragments); id. at 20:35–36
 (identifying scFv and Fab as examples of antibody deriva-
 tives); id. at 30:15–17 (identifying Fab, F(ab)2, and scFv as
 examples of antibody derivatives). The prosecution his-
 tory, therefore, does not clearly establish disclaimer. Sec-
 ond, the district court’s determination that the patentee
 disclaimed antibody derivatives “including bispecific anti-
 bodies, except antibody fragments” is inconsistent with the
 examiner’s subsequent allowance of at least claim 4. As
 explained above, claim 4 explicitly claims “a bispecific an-
 tibody,” a claimed embodiment directly at odds with a dis-
 claimer theory. The prosecution history, therefore, does
 not support the district court’s construction of “antibody.”
     The parties agree that Baxalta’s and Genentech’s pro-
 posed constructions are recognized meanings of “antibody.”
 We hold that the district court erred in selecting the nar-
 rower construction, which is inconsistent with the written
 description and the plain language of the claim. Consistent
 with the claims and the written description, we instead
 construe “antibody” as “an immunoglobulin molecule hav-
 ing a specific amino acid sequence comprising two heavy
 chains (H chains) and two light chains (L chains).”
                    B. “Antibody Fragment”
      The district court construed “antibody fragment” as “a
 fragment of an antibody which partially or completely
 lacks the constant region.” The district court further spec-
 ified that “the term ‘antibody fragment’ excludes bispecific
 antibodies.” Baxalta, 2018 WL 6304351, at *12–13. Bax-
 alta argues that the district court’s construction improp-
 erly excludes bispecific antibodies and imports limitations
 from the written description. For reasons related to our
 construction of “antibody,” we hold that the district court
 erred in construing “antibody fragment.” We construe that
 term as “[a] portion of an immunoglobulin molecule having
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 14                           BAXALTA INC. v. GENENTECH, INC.




 a specific amino acid sequence comprising two heavy
 chains (H chains) and two light chains (L chains).”
     The district court’s construction relied on the following
 portion of the written description:
      The term factor IX/IXa activating antibodies and
      antibody derivatives may also include . . . e.g.,
      “technically modified antibodies” such as synthetic
      antibodies, chimeric or humanized antibodies, or
      mixtures thereof, or antibody fragments which par-
      tially or completely lack the constant region, e.g.
      Fv, Fab., Fab' or F(ab) etc.
 ’590 patent at 6:15–22 (emphases added). But this excerpt
 does not, as the district court suggests, define antibody
 fragments as necessarily “partially or completely lack[ing]
 the constant region.” Indeed, the standard for lexicography
 is exacting, requiring the patentee to “‘clearly express an
 intent’ to redefine a term.” Thorner, 669 F.3d at 1365–66.
 “[A]lthough the specification often describes very specific
 embodiments of the invention, we have repeatedly warned
 against confining the claims to those embodiments.” Phil-
 lips, 415 F.3d at 1323. Here, the written description’s use
 of “may also include,” “e.g.,” “such as,” and “etc.” makes
 clear the patentee did not intend this excerpt of the written
 description to define “antibody fragment.” Instead, we con-
 strue “fragment” according to its plain and ordinary mean-
 ing in light of the written description as a whole.
 Accordingly, we construe “antibody fragment” to mean “a
 portion of an antibody” as we have defined above, that is:
 “a portion of an immunoglobulin molecule having a specific
 amino acid sequence comprising two heavy chains
 (H chains) and two light chains (L chains).”
                     III.   CONCLUSION
     We have considered the parties’ remaining arguments
 and do not find them persuasive. Because the district court
 erred in construing the terms “antibody” and “antibody
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 BAXALTA INC. v. GENENTECH, INC.                          15



 fragment” and entered judgment of non-infringement
 based on its erroneous constructions, we vacate and re-
 mand for further proceedings consistent with the correct
 constructions of the terms.
                VACATED AND REMANDED
                           COSTS
     Costs to Baxalta.
