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 represented 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 defendantCase: 19-1527 Document: 59 Page: 1 Filed: 08/27/2020
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 Pharmaceutical 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 Delaware issued a claim construction order, construing the 

terms “antibody” and “antibody fragment.” Following the 

claim construction order, the parties stipulated to non-infringement of the asserted claims. The district court entered 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 decision. Judge Plager replaced Judge Stoll on the panel following 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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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 “coagulation cascade.” ’590 patent at 1:7–10. One “key step” 

in the cascade is when an enzyme known as activated clotting factor VIII (FVIIIa) complexes with another enzyme 

known as activated clotting factor IX (FIXa) to form a complex 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 administered as treatments. ’590 patent at 1:24–32. The ’590 

patent relates to preparations used to treat hemophilia patients who have developed factor VIII inhibitors. ’590 patent 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 increases the procoagulant activity of Factor IXa.

4. The antibody or antibody fragment according to 

claim 1, wherein said antibody or antibody fragment is selected from the group consisting of a 

monoclonal antibody, a chimeric antibody, a humanized 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 antibody.

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The parties disputed the construction of the terms “antibody” and “antibody fragment,” among other terms not at

issue on appeal. Generally, antibodies are Y-shaped structures 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 different light chains, allowing them to bind two different antigens. Baxalta argued “antibody” should be construed as 

“[a] molecule having a specific amino acid sequence comprising 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, consisting of two identical heavy chains (H chains) and two identical light chains (L chains).” 

The district court determined that “the term antibody

standing alone without other structural terms can have different meanings to those skilled in the art,” and that both 

Baxalta’s and Genentech’s proposed constructions were acceptable 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 [Genentech’s] narrower definition” by expressly defining antibodies in column 5 of the patent, which states:

Antibodies are immunoglobulin molecules having a 

specific amino acid sequence which only bind to antigens that induce their synthesis (or its immunogen, respectively) or to antigens (or immunogens) 

which are very similar to the former. Each immunoglobulin molecule consists of two types of polypeptide chains. Each molecule consists of large, 

identical heavy chains (H chains) and two light, 

also identical chains (L chains).

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Id. at *5 (quoting ’590 patent at 5:56–63).

Although the district court recognized that the ’590 patent 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” rather than “antibodies.” Id. at *5–6. The district court likewise 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 district 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 antigens, 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 antibody derivative against factor IX/factor IXa which increases 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 “chimeric antibodies, humanized antibodies, single chain antibodies, bispecific antibodies, diabodies and di-, oligo- or 

multimers thereof.” Id. During prosecution, the patent examiner rejected the term “antibody derivatives” as not enabled 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 suggestion, the patentee amended the claims to recite “antibody 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 antibodies, 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 sequence 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 antibody derivatives.” Id. The district court, relying on a portion of the written description reciting that “antibody 

fragments . . . partially or completely lack the constant region” and identifying examples of fragments (Fv, Fab, Fab'

[and] F(ab)'2), construed “antibody fragment” as “a fragment 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 appeals, 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 person 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 antibody or antibody fragment thereof that binds Factor IX or 

Factor IXa and increases the procoagulant activity of Factor IXa.” Therefore, contrary to the district court’s construction, 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 synthesis or very similar antigens. 

The dependent claims confirm that “antibody” is not so 

limited. For example, dependent claim 4, recites “[t]he antibody 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 construction 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 antibody has a structure of a human antibody but combines 

non-human antibody portions, such as the complement determining regions (CDRs), with human antibody portions. 

’590 patent at 6:50–7:1. It explains that a chimeric antibody differs from a humanized antibody in that it comprises 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 binding 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 antibody 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 humanized 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 construction that would “render several dependent claims 

meaningless”). 

that humanized antibodies, chimeric antibodies, and 

bispecific antibodies fall outside the district court’s construction. See Genentech Resp. Br. at 1, 53; Baxalta Op. 

Br. at 12.

4 Baxalta argues that the district court’s claim construction is also inconsistent with dependent claims 7, 9, 

11, 18, 21, and 22 because they require synthetic production 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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The district court rejected this inconsistency, suggesting that the proper result here is “invalidation of the inconsistent 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://oralarguments.cafc.uscourts.gov/default.aspx?fl=2019-1527.mp3 

(counsel for Genentech explaining “we don’t have an answer 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 Intellectual 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 Derivatives,” the patentee explains:

Antibodies are immunoglobulin molecules having a 

specific amino acid sequence which only bind to antigens that induce their synthesis (or its immunogen, respectively) or to antigens (or immunogens) 

which are very similar to the former. Each immunoglobulin molecule consists of two types of polypeptide 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 “antibody.” While this is a plausible reading of the excerpt in 

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isolation, claim construction requires that we “consider the 

specification as a whole, and [] read all portions of the written 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 considered in the context of the remainder of the written description 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 written description provides specific disclosures regarding 

bispecific, chimeric, and humanized antibodies and methods 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 consist 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 antibodies . . . . In these technically modified antibodies, e.g., 

a part or parts of the light and/or heavy chain may be substituted.” ’590 patent at 6:15–24. And the written description 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 shuffling or humanizing techniques.” Id. at 7:65–8:3 (emphasis 

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added). The written description, therefore, discloses synthetic techniques for preparing antibodies such as humanized or chimeric antibodies, which are inconsistent with the 

district court’s claim construction requirement that the antibody “only binds to the antigen that induced its synthesis 

or very similar antigens.” Recognizing that these disclosed 

techniques for preparing the claimed antibodies would result in antibodies excluded by the district court’s construction, 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 description discloses antibodies that fall outside the district 

court’s construction, but rather argues that “there is no legal 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 antibodies 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 antibody.” Baxalta, 2018 WL 6304351, at *7. We have recognized that the prosecution history “often lacks the clarity 

of the specification and thus is less useful for claim construction 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 patentee’s amendment substituting the term “antibody fragment” 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 significant way,” e.g., bispecific antibodies, Baxalta, 2018 WL 

6304351, at *6–7, the district court determined that the 

amendment from “antibody derivative” to “antibody fragment” amounted to a disclaimer of antibody derivatives “including 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 discern 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 attach, 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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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 derivatives); id. at 30:15–17 (identifying Fab, F(ab)2, and scFv as 

examples of antibody derivatives). The prosecution history, therefore, does not clearly establish disclaimer. Second, the district court’s determination that the patentee 

disclaimed antibody derivatives “including bispecific antibodies, 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 antibody,” a claimed embodiment directly at odds with a disclaimer theory. The prosecution history, therefore, does 

not support the district court’s construction of “antibody.”

The parties agree that Baxalta’s and Genentech’s proposed constructions are recognized meanings of “antibody.” 

We hold that the district court erred in selecting the narrower 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 having 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 specified that “the term ‘antibody fragment’ excludes bispecific 

antibodies.” Baxalta, 2018 WL 6304351, at *12–13. Baxalta argues that the district court’s construction improperly 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 partially 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.” Phillips, 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 construe “fragment” according to its plain and ordinary meaning 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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fragment” and entered judgment of non-infringement 

based on its erroneous constructions, we vacate and remand for further proceedings consistent with the correct 

constructions of the terms.

VACATED AND REMANDED

COSTS

Costs to Baxalta.

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