  United States Court of Appeals
      for the Federal Circuit
                ______________________

   BIOGEN IDEC, INC. AND GENENTECH, INC.,
             Plaintiffs-Appellants,

                           v.

  GLAXOSMITHKLINE LLC AND GLAXO GROUP
                 LIMITED,
            Defendants-Appellees.
           ______________________

                      2012-1120
                ______________________

    Appeal from the United States District Court for
the Southern District of California in No. 10-CV-0608,
Judge Roger T. Benitez.
                ______________________

                Decided: April 16, 2013
                ______________________

    JOHN ALLCOCK, DLA Piper LLP, of San Diego, Cali-
fornia, argued for plaintiffs-appellants. With him on the
brief were KATHRYN RILEY GRASSO, STANLEY J.
PANIKOWSKI and AARON FOUNTAIN. Of counsel on the
brief were MEREDITH MARTIN ADDY, Steptoe & Johnson,
LLP, of Chicago, Illinois. Of counsel was RAMA C.
ELLURU, of Washington, DC.
2                          BIOGEN IDEC   v. GLAXOSMITHKLINE

    LISA M. FERRI, Mayer Brown LLP, of New York, New
York, argued for defendants-appellees. With her on the
brief were BRIAN W. NOLAN; VERA A. NACKOVIC and
ANDREA C. HUTCHINSON, of Chicago, Illinois.
                ______________________

     Before DYK, PLAGER, and REYNA, Circuit Judges.
     Opinion for the court filed by Circuit Judge REYNA.
     Dissenting opinion filed by Circuit Judge PLAGER.
REYNA, Circuit Judge.
    Biogen Idec Inc. and Genentech, Inc. (collectively, “Bi-
ogen”) seek review of the district court’s construction of
the disputed claim term “anti-CD20 antibody” that nar-
rowed the term based on prosecution history disclaimer.
Under that construction, Biogen stipulated that it could
not prove infringement by GlaxoSmithKline LLC and
Glaxo Group Ltd. (collectively, “GSK”). Biogen took that
approach in order to appeal the district court’s claim
construction. We conclude that the district court did not
err in finding a clear and unmistakable disclaimer and,
therefore, we affirm.
                     I. BACKGROUND
    In the mid-1990’s, scientists from Biogen discovered
that patients with Chronic Lymphocytic Leukemia (CLL)
could be treated using anti-CD20 antibodies like Biogen’s
Rituxan® (rituximab). CLL is a cancer in which a type of
white blood cell called a B lymphocyte (“B cell”) becomes
cancerous. Normal B cells of CLL patients undergo a
malignant transformation, which causes the cells to
replicate and accumulate in the bloodstream, bone mar-
row, and certain tissues at much higher levels than in a
healthy person. Symptoms of CLL include fatigue, fevers,
bleeding, and infections caused by a decrease in the
number of red blood cells and platelets due to the overa-
bundance of B cells in the blood stream. Biogen Idec, Inc.
 BIOGEN IDEC   v. GLAXOSMITHKLINE                       3
v. GlaxoSmithKline LLC, No. 10-CV-00608, 2011 U.S.
Dist. LEXIS 120043, at *2 (S.D. Cal. Oct. 17, 2011).
Patients also exhibit signs of the condition including
enlarged lymph nodes and spleen from an excess of B cells
in the tissue of those organs. Id. As a result, researchers
sought a treatment regime that mitigated both the symp-
toms and signs of CLL by reducing the number cancerous
B cells without the deleterious side effects stemming from
other treatments such as radiation or chemotherapy.
     Fortunately, both normal and cancerous B cells have
a portion of the CD20 antigen protein exposed beyond the
cell surface. Anti-CD20 antibodies are capable of target-
ing and binding to these CD20 antigens on the B cell’s
surface. Once the anti-CD20 antibody successfully at-
taches to the CD20 antigen, it destroys the B cell regard-
less of whether it is normal or cancerous. For patients
with CLL, administering the anti-CD20 antibodies thus
mitigates the symptoms and signs caused by the condition
while still allowing their bodies to replenish normal B
cells.
    Biogen sought a patent covering, inter alia, a method
for treating patients with CLL involving administering a
therapeutically effective amount of the anti-CD20 anti-
body.    It was eventually awarded U.S. Patent No.
7,682,612 (“the ’612 patent”), entitled “Treatment of
Hematologic Malignancies Associated with Circulating
Tumor Cells Using Chimeric Anti-CD20 Antibody.” The
patent was not limited to any particular type of anti-
CD20 antibody and, in fact, has dependent claims claim-
ing specific types of antibodies: chimeric, 1 rituximab,




   1   Chimeric antibodies are antibodies with human
and nonhuman (typically rodent) regions.
4                           BIOGEN IDEC   v. GLAXOSMITHKLINE
humanized, 2 and human. In describing its preferred
embodiment, the patent explains that
    the anti-CD20 antibody will bind CD20 with high
    affinity, i.e., ranging from 10-5 to 10-9 M. Prefera-
    bly, the anti-CD20 antibody will comprise a chi-
    meric, primate, PRIMATIZED®, human, or
    humanized antibody. Also, the invention embrac-
    es the use of antibody fragments . . . and aggre-
    gates thereof.
’612 patent col. 2 ll. 45–51. But in this regard, the specifi-
cation acknowledges that “a particularly preferred chi-
meric anti-CD20 antibody is RITUXAN® (rituximab),
which is a chimeric gamma 1 anti-human CD20 anti-
body.” Id. col. 3 ll.18–20. Additionally, the ’612 patent
incorporates by reference U.S. Patent No. 5,736,137 (“the
’137 patent”), which teaches the isolation, screening, and
characterization of Rituxan®. The ’137 patent also de-
fines an “anti-CD20 antibody” as used therein as “an
antibody which specifically recognizes a cell surface . . .
typically designated as the human B lymphocyte restrict-
ed differentiation antigen Bp35, commonly referred to as
CD20.” ’137 patent col. 6 l. 65 to col. 7 l. 2.
    At the time of Biogen’s discovery, scientists already
knew that available anti-CD20 antibodies could treat
certain cancers of the lymph nodes, called B-cell lympho-
mas, such as non-Hodgkins lymphoma. Unlike CLL,
however, lymphomas are characterized by B cells with a
greater density of CD20 antigen targets on the surface
and fewer cancerous B cells in the bloodstream. Thus,
lymphomas were readily treated with anti-CD20 antibod-
ies, but it remained doubtful whether they would be
effective against CLL.


    2   Humanized antibodies are antibodies with sub-
stantially human regions.
 BIOGEN IDEC   v. GLAXOSMITHKLINE                           5
    Initially, it was believed that only one large loop, or
epitope, of the CD20 antigen’s protein chain was exposed
on the cancerous B cell’s surface, which made that loop
the only suitable target for an anti-CD20 antibody. After
Biogen filed its application for the ’612 patent, other
researchers discovered that the CD20 antigen had a
second small loop, to which other anti-CD20 antibodies
could attach.
    During prosecution of the ’612 patent, the examiner
rejected all the claims because the specification did not
provide enablement commensurate with the scope of the
claimed invention, which, under the “broadest reasonable
interpretation” standard applied by the U.S. Patent and
Trademark Office (PTO), included “any and all anti-CD20
antibodies, no matter the specificity or affinity for the
specific epitope on the circulating tumor cells.” Joint
App’x 307. “[S]election of an antibody as an immunother-
apeutic agent,” continued the examiner, “is an unpredict-
able task as the antibody must possess sufficient
specificity and a high degree of affinity for its target for
use as an immunotherapeutic agent and because these
qualities are dependent on the physiology of the particu-
lar pathology and the accessibility of the target antigen.”
Id. The examiner acknowledged that the specification
was enabling for Rituxan®, but that it was “silent con-
cerning what sort of specificity and affinity would be
necessary” for other anti-CD20 antibodies. Id. In re-
sponse, Biogen pointed to its disclosure of Rituxan® and
maintained that
   even though antibodies directed to the same anti-
   gen might have different affinities and functional
   characteristics, one of skill in the art could readily
   identify an antibody that binds to CD20 with simi-
   lar affinity and specificity as does RITUXAN® us-
   ing techniques that are well known in the art. . . .
   With that knowledge in hand, the skilled artisan
   could readily produce anti-CD20 antibodies using
6                           BIOGEN IDEC   v. GLAXOSMITHKLINE
    similar techniques, and screen such antibodies for
    those having an affinity and functional activity
    similar to RITUXAN®.
Joint App’x 324–25. After considering Biogen’s argu-
ments, the examiner withdrew her enablement rejection,
and the claims eventually issued.
    In 2002, GSK, in collaboration with Genmab A/S, de-
veloped a breakthrough anti-CD20 antibody, Arzerra®
(ofatumumab), which is distinctly different from Ritux-
an® in several respects. Whereas Rituxan® attaches to
the large loop, it is believed that Arzerra® attaches to the
second small loop previously thought to be hidden inside
the cell. This means that the Arzerra® anti-CD20 anti-
body differs from the Rituxan® anti-CD20 antibody with
regard to specificity, or ability of the antibody to bind to a
particular epitope of an antigen, and affinity, or tightness
of the bond between the antibody and the antigen. Like-
wise, unlike Rituxan®, which is a chimeric antibody,
Arzerra® is a fully human antibody, so there is less of a
risk that the body will reject it and develop antibodies
against it. Researchers believe that its fully human
characteristic permits the antibody to bind to the small
loop. Additionally, because Arzerra® binds to the small
loop, it has a much greater affinity for the CD20 antigen,
which means that it can bind longer, giving the antibody
more time to kill the target B cell.
    In March 2010, Biogen sued GSK for infringement of
the ’612 patent, asserting claims 1-4, 6, 8-10, 14-17, 20-22,
and 58-60. GSK counterclaimed, alleging noninfringe-
ment, invalidity, and unenforceability of those claims.
The district court held a Markman hearing, and on Octo-
ber 18, 2011, construed the following terms: “effective to
treat the chronic lymphocytic leukemia,” “anti-CD20
 BIOGEN IDEC   v. GLAXOSMITHKLINE                      7
antibody”/“CD-20 binding fragment,” 3 and “does not
include treatment with a radiolabeled anti-CD20 anti-
body”/“radiation is not used.” For the term, “anti-CD20
antibody,” Biogen proposed the broad construction “an
antibody that binds to a cell surface CD20 antigen.” The
district court, however, adopted GSK’s construction of
“rituximab and antibodies that bind to the same epitope
of the CD20 antigen with similar affinity and specificity
as rituximab.” Biogen, 2011 U.S. Dist. LEXIS 120043, at
*31. It based this conclusion on prosecution history
disclaimer wherein Biogen limited that term to overcome
the examiner’s enablement rejection. Following this
construction, which excluded GSK’s accused Arzerra®
product, Biogen stipulated to noninfringement, and on
November 15, 2011, the court entered judgment against
Biogen under Federal Rule of Civil Procedure 54(b).
Biogen subsequently appealed to this court. We have
jurisdiction over this appeal pursuant to 28 U.S.C.
§ 1295(a)(1).
                  II. STANDARD OF REVIEW
    Claim construction is an issue of law. Markman v.
Westview Instruments, Inc., 52 F.3d 967, 981 (Fed. Cir.
1995) (en banc), aff’d, 517 U.S. 370 (1996). Accordingly,
this court reviews district court claim constructions de
novo. Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448,
1456 (Fed. Cir. 1998) (en banc).
                      III. DISCUSSION
    Claims terms “are generally given their ordinary and
customary meaning.” Phillips v. AWH Corp., 415 F.3d
1303, 1312 (Fed. Cir. 2005) (en banc) (quoting Vitronics


   3     The claim construction issues concerning “anti-
CD20 antibody” and “CD-20 binding fragment” are indis-
tinct; thus, they will be addressed collectively under the
term “anti-CD20 antibody.”
8                          BIOGEN IDEC   v. GLAXOSMITHKLINE
Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir.
1996)). But a term’s ordinary meaning must be consid-
ered in the context of all the intrinsic evidence, including
the claims, specification, and prosecution history. 3M
Innovative Props. Co. v. Avery Dennison Corp., 350 F.3d
1365, 1371 (Fed. Cir. 2003); see also Phillips, 415 F.3d at
1314. “[T]he prosecution history can often inform the
meaning of the claim language by demonstrating how the
inventor understood the invention and whether the inven-
tor limited the invention in the course of prosecution,
making the claim scope narrower than it would otherwise
be.” Phillips, 415 F.3d at 1317. In the latter circum-
stance, we have recognized that a “clear and unmistaka-
ble” disavowal during prosecution overcomes the “‘heavy
presumption’ that claim terms carry their full ordinary
and customary meaning.” Omega Eng’g, Inc. v. Raytek
Corp., 334 F.3d 1314, 1323, 1326 (Fed. Cir. 2003); see also
Epistar Corp. v. Int’l Trade Comm’n, 566 F.3d 1321, 1334
(Fed. Cir. 2009) (“A heavy presumption exists that claim
terms carry their full ordinary and customary meaning,
unless it can be shown the patentee expressly relinquished
claim scope.” (emphasis added)). Thus, when the patentee
unequivocally and unambiguously disavows a certain
meaning to obtain a patent, the doctrine of prosecution
history disclaimer narrows the meaning of the claim
consistent with the scope of the claim surrendered. Id. at
1324.
    Prosecution history disclaimer plays an important
role in the patent system. It “promotes the public notice
function of the intrinsic evidence and protects the public’s
reliance on definitive statements made during prosecu-
tion.” Id. Such statements can take the form of either
amendment or argument. See Elkay Mfg. Co. v. Ebco Mfg.
Co., 192 F.3d 973, 979 (Fed. Cir. 1999); see also Computer
Docking Station Corp. v. Dell, Inc., 519 F.3d 1366, 1374
(Fed. Cir. 2008) (“Statements made during prosecution
may also affect the scope of the claims.”). For this reason,
 BIOGEN IDEC   v. GLAXOSMITHKLINE                        9
the entirety of a patent’s file history captures the public
record of the patentee’s representations concerning the
scope and meaning of the claims. Seachange Int’l, Inc. v.
C-COR Inc., 413 F.3d 1361, 1372 (Fed. Cir. 2005) (quoting
Hockerson-Halberstadt, Inc. v. Avia Grp. Int’l, Inc., 222
F.3d 951, 957 (Fed. Cir. 2000)); see also Elkay, 192 F.3d at
979 (“[I]t is the totality of the prosecution history that
must be assessed, not the individual segments of the
presentation made to the [PTO] by the applicant . . . .”).
Competitors are entitled to rely on those representations
when determining a course of lawful conduct, such as
launching a new product or designing-around a patented
invention. Id. Beyond the notice function and reliance-
based aspects of a patent’s prosecution history, it “pro-
vides evidence of how the [PTO] and the inventor under-
stood the patent.” Edwards Lifesciences LLC v. Cook Inc.,
582 F.3d 1322, 1327 (Fed. Cir. 2009) (quoting Phillips,
415 F.3d at 1317) (alteration in original).
    This case requires us to analyze how the PTO and the
inventors understood the disputed term, “anti-CD20
antibody,” in the ’612 patent to determine if the inventors
disclaimed claim scope during prosecution of that patent.
Biogen maintains that all the evidence—including the
claims, the specification, and statements made by all
parties recorded in the prosecution history—indicates
that the term was used according to its plain and ordinary
meaning, “an antibody that binds to a cell surface CD20
antigen.” For purposes of our analysis, we initially as-
sume without deciding that neither the claims nor the
specification compel a construction contrary to the one
offered by Biogen. The question becomes whether state-
ments in the prosecution history are sufficient to over-
come the “heavy presumption” that the term carries its
full ordinary and customary meaning advanced by Bio-
gen. We conclude that they are.
    During prosecution of the ’612 patent, the examiner
rejected all pending claims because the specification did
10                         BIOGEN IDEC   v. GLAXOSMITHKLINE
not enable a person skilled in the art to practice the full
scope of the claims, which could have encompassed “any
and all anti-CD20 antibodies, no matter the specificity or
affinity for the specific epitope on the circulating tumor
cells.” Joint App’x 307. Instead, according to the examin-
er, the specification only enabled Rituxan®, rituximab,
and 2B8-MX-DTPA. 4 It was not enabling for other anti-
CD20 antibodies, which had different structural and
functional properties.
     In response, rather than challenging the examiner’s
understanding of the crucial terms, the applicants argued
that the specification was enabling for anti-CD20 antibod-
ies with similar affinity and specificity as Rituxan®.
Indeed, the applicants conceded that other “antibodies
directed to the same antigen [i.e., CD20] might have
different affinities and functional characteristics,” and
limited their claims to antibodies similar to Rituxan®
nonetheless. Joint App’x 324. While the applicants may
not have repeated the examiner’s language verbatim et
literatim, it is clear that they were limiting their inven-
tion to what the examiner believed they enabled: antibod-
ies that have a similar specificity and affinity for the
specific epitope to which Rituxan® binds. 5


     42B8-MX-DTPA, like Rituxan®, is a chimeric anti-
CD20 antibody. See generally ’137 patent.
     5  Pointing to another portion of the prosecution his-
tory, Biogen maintains that the novel aspect of the ’612
patent is its recognition that any anti-CD20 antibody
could treat CLL. Joint App’x 325. This argument, how-
ever, does not alter our analysis where the applicants
overcame the examiner’s enablement rejection by explicit-
ly relinquishing claim scope. See Computer Docking
Station, 519 F.3d at 1377 (“[A] disavowal, if clear and
unambiguous, can lie in a single distinction among
many.”).
 BIOGEN IDEC   v. GLAXOSMITHKLINE                        11
     Biogen now argues that because it never explicitly re-
ferred to any particular “epitope”—and because CD20 was
only thought to have one epitope at the time the patent
application was filed—the applicants were merely refer-
ring to specificity and affinity in their general sense; that
is, anti-CD20’s general preference for B cells regardless of
the particular CD20 epitope to which it binds. Read in
context, however, the full prosecution history does not
support Biogen’s position. The examiner began by char-
acterizing antibodies by their specificity and affinity for a
specific epitope, and the applicants adopted that charac-
terization when they limited their claims to antibodies
similar to Rituxan®. While disavowing statements must
be “so clear as to show reasonable clarity and deliberate-
ness,” Omega, 334 F.3d at 1325, this requirement does not
require the applicant to parrot back language used by the
examiner when clearly and deliberately responding to a
particular grounds for rejection. If an applicant chooses,
she can challenge an examiner’s characterization in order
to avoid any chance for disclaimer, but the applicants in
this case did not directly challenge the examiner’s charac-
terization. See TorPharm Inc. v. Ranbaxy Pharm., Inc.,
336 F.3d 1322, 1330 (Fed. Cir. 2003) (“Whether the pa-
tentee chooses to dispute the examiner’s view of matters
is relevant to claim interpretation, for there a court may
need to ascertain exactly what subject matter was actual-
ly examined and allowed by the PTO.”). Rather, they
simply discussed specificity and affinity with regard to
the disclosure of the ’612 patent, which was narrowly
limited to Rituxan®, rituximab, and 2B8-MX-DTPA. The
disclaimer of antibodies that do not have a similar affinity
and specificity for the specific epitope to which Rituxan®
binds was clear and unmistakable. Accordingly, the
district court properly limited the scope of the claim term,
“anti-CD20 antibody,” based on prosecution history dis-
claimer. 6

    6   We are mindful that “it is the applicant, not the
12                         BIOGEN IDEC   v. GLAXOSMITHKLINE
    Biogen makes two arguments regarding why the
claim term’s full plain and ordinary meaning should
control, both of which are unpersuasive. First, Biogen
argues that the claims envisage a difference between
claim one’s broad coverage of any and all anti-CD20
antibodies, and the specific types of antibodies listed in
the dependent claims—chimeric, rituximab, humanized,
and human. See ’612 patent col. 8 ll. 31–38. Biogen also
asserts the general caution against importing a preferred
embodiment into the claims. Biogen’s Br. 32. Our cases
make clear, however, that where found, prosecution
history disclaimer can overcome the presumption of claim
differentiation. Regents of Univ. of Cal. v. DakoCytoma-


examiner, who must give up or disclaim subject matter
that would otherwise fall within the scope of the claims.”
Innova/Pure Water, Inc. v. Safari Water Filtration Sys.,
Inc., 381 F.3d 1111, 1124 (Fed. Cir. 2004). This case,
however, differs markedly from those frequently raising
this admonition. Those cases typically involve an appli-
cant standing silent when confronted by statements made
by the examiner during prosecution, most often in the
examiner’s Statement of Reasons for Allowance. See, e.g.,
Salazar v. Procter & Gamble Co., 414 F.3d 1342, 1345–47
(Fed. Cir. 2005); ACCO Brands, Inc. v. Micro Sec. Devices,
Inc., 346 F.3d 1075, 1079 (Fed. Cir. 2003). This case deals
not only with applicants letting stand an examiner’s
narrow characterization of a claim term, but also their
adoption of that characterization to overcome the examin-
er’s enablement rejection. Thus, the acquiescence cases
are inapposite. See TorPharm, 336 F.3d at 1330 (“[T]he
public is entitled to equate an inventor’s acquiescence to
the examiner’s narrow view of patentable subject matter
with abandonment of the rest.”).
 BIOGEN IDEC   v. GLAXOSMITHKLINE                         13
tion Cal., Inc., 517 F.3d 1364, 1375–76 (Fed. Cir. 2008).
Furthermore, the applicants’ disclaimer in this case is not
necessarily inconsistent with other possible embodiments
or even the dependent claims, so long as they involve
chimeric, humanized, or human antibodies that are
similar to Rituxan®. Cf. Elekta Instrument S.A. v. O.U.R.
Scientific Int’l, Inc., 214 F.3d 1302, 1308 (Fed. Cir. 2000)
(adopting a claim construction that excluded the preferred
and sole embodiment in light of, inter alia, prosecution
history disclaimer).
      Second, Biogen contends that because the ’612 patent
incorporated the ’137 patent by reference, the latter
patent’s definition of “anti-CD20 antibody” should control.
The problem with this argument is that the ’137 patent
expressly and uniquely defines “anti-CD20 antibody” for
use therein, that is, within the ’137 patent. ’137 patent
col. 6 l. 65 (“As used herein, the term ‘anti-CD20 antibody’
is . . . .” (emphasis added)). The definition, therefore, does
not necessarily reflect how a person of ordinary skill in
the art would understand the disputed term in the con-
text of the ’612 patent. See Phillips, 415 F.3d at 1313.
Rather, it may very well be that this is a “special defini-
tion given to a claim term by the patentee that differs
from the meaning it would otherwise possess.” Id. at
1316. Even assuming the ’137 patent conveyed “anti-C20
antibody’s” plain and ordinary meaning, this is a case
where prosecution history disclaimer overcomes the
presumption of plain and ordinary meaning as we con-
cluded above.
    We have considered Biogen’s other arguments, but
find no basis for reversing the district court’s claim con-
struction.
                      IV. CONCLUSION
    For the foregoing reasons, we affirm the district
court’s conclusion that “anti-CD20 antibody” as used in
14                         BIOGEN IDEC   v. GLAXOSMITHKLINE
the ’612 patent is limited by prosecution history disclaim-
er.
                      AFFIRMED
                          COSTS
     No costs.
  United States Court of Appeals
      for the Federal Circuit
                 ______________________

    BIOGEN IDEC, INC. AND GENENTECH, INC.,
              Plaintiffs-Appellants,

                            v.

  GLAXOSMITHKLINE LLC AND GLAXO GROUP
                 LIMITED,
            Defendants-Appellees.
           ______________________

                       2012-1120
                 ______________________

    Appeal from the United States District Court for
the Southern District of California in No. 10-CV-0608,
Judge Roger T. Benitez.
                ______________________

PLAGER, Circuit Judge, Dissenting.
     Because I do not find anywhere in the majority opin-
ion or in the prosecution history that clear and unmistak-
able evidence of a disclaimer as required by our
precedents, I cannot agree with the majority that such a
disclaimer was made by Biogen during the prosecution of
its application for the ’612 patent; I respectfully dissent.
    The parties do not dispute that the plain meaning of
the claim term “anti-CD20 antibody” is “an antibody that
binds to a cell surface CD-20 antigen.” Nor do the parties
dispute that the written description of the ’612 patent
supports that plain meaning. Indeed, the majority con-
2                          BIOGEN IDEC   v. GLAXOSMITHKLINE
cedes that “neither the claims nor the specification [sic]
compel a construction contrary to the one offered by
Biogen.” Maj. Op. at 9. The only dispute is whether the
applicants disclaimed the plain meaning of “anti-CD20
antibody” during prosecution.
    The majority purports to tease out of the prosecution
history such a disclaimer. The doctrine of prosecution
disclaimer promotes the public notice function of a pa-
tent’s intrinsic evidence and protects the public’s reliance
on definitive statements made during prosecution. Ome-
ga Eng’g, Inc. v. Raytek Corp., 334 F.3d 1314, 1324 (Fed.
Cir. 2003). However, the give-and-take that is often part
of the process of negotiation between an examiner and an
applicant may result in less-than-clear understandings,
as happened here. Making too much of such ambiguous
statements “does not advance the patent’s notice function
or justify public reliance.” SanDisk Corp. v. Memorex
Products, Inc., 415 F.3d 1278, 1287 (Fed. Cir. 2005).
Accordingly, we have consistently declined to invoke the
doctrine of prosecution disclaimer in the absence of “an
unambiguous disavowal that clearly and unmistakably
disclaims” the plain meaning of a disputed claim term.
Grober v. Mako Prods., Inc., 686 F.3d 1335, 1342 (Fed.
Cir. 2012) (emphasis added).
    The prosecution history of the ’612 patent makes clear
that one may practice the claimed invention by adminis-
tering RITUXAN® and RITUXAN®-like antibodies to a
CLL patient. See J.A. 325 (stating that “[t]he antibodies
to be used for the claimed immunotherapy were described
in detail in U.S. Patent 5,736,137,” which “describes the
isolation, screening and characterization of RITUXAN®”).
The question we must answer, however, is whether the
prosecution history makes it clear that using RITUXAN®-
like antibodies is the only way to practice the claimed
invention, and that no other antibodies can be used.
 BIOGEN IDEC   v. GLAXOSMITHKLINE                            3
   The specific prosecution history on which the majority
seems to rely is the following:
    Examiner:
   Claims 1 and 12 are broadly drawn to ‘. . . an anti-
   CD20 antibody or fragment thereof’. This is
   broadly interpreted for examination purposes to
   be any and all anti-CD20 antibodies, no matter
   the specificity or affinity for the specific epitope on
   the circulating tumor cells. While the specifica-
   tion is enabling for the application of RITUXAN®,
   RITUXIMAB® and 2B8-MX-DTPA in the treat-
   ment of hematologic malignancies, the specifica-
   tion is not enabling in the application of all other
   anti-CD20 antibodies, which may have different
   structural and functional properties.
J.A. 307.
   Applicants:
   Applicants respectfully submit that even though
   antibodies directed to the same antigen might
   have different affinities and functional character-
   istics, one of skill in the art could readily identify
   an antibody that binds to CD20 with similar affin-
   ity and specificity as does RITUXAN® using tech-
   niques that are well known in the art. . . . With
   that knowledge in hand, the skilled artisan could
   readily produce anti-CD20 antibodies using simi-
   lar techniques, and screen such antibodies for
   those having an affinity and functional activity
   similar to Rituxan®.
J.A. 324–25.
    Does this constitute a clear and unmistakable dis-
claimer of all antibodies except RITUXAN® and
RITUXAN®-like antibodies? I do not think so. The exam-
iner was addressing an enablement issue; the applicants’
4                          BIOGEN IDEC   v. GLAXOSMITHKLINE
response was at worst a non-response to the examiner’s
concern, and at best a statement that antibodies other
than RITUXUN® and RITUXUN®-like antibodies that had
similar affinity and specificity are included in the claims.
“Similar” does not mean “same.” Applicants’ usage of
“similar” is inconsistent with an acceptance by the appli-
cants of the narrow confines proposed by the examiner’s
reference to the “specificity or affinity for the specific
epitope.”
     Regarding the introduction of the “epitope” issue,
much of the dispute before us centers on whether the
applicants disclaimed antibodies that bind to a different
binding site (or epitope) than does RITUXAN®. Biogen
argues that the disputed claim term covers antibodies
that bind to CD20 generally. The majority, however,
affirms the district court’s decision to the contrary, im-
porting a specific “epitope” into its claim construction. 1
The majority does so because applicants purportedly
adopted the examiner’s limitation on this point. See Maj.
Op. at 11. Yet applicants in their response omitted the
very term “epitope” that the majority claims they adopted
as a limitation. And while the applicants’ decision to omit
“epitope” from their response could mean that the appli-
cants silently accepted this limitation suggested by the
examiner, it also could mean that the applicants silently
rejected it. Even more to the point, when applicants
spoke in their disputed statement of binding, they did not



    1   The district court construed “anti-CD20 antibody,”
as “rituximab and antibodies that bind to the same
epitope of the CD20 antigen with similar affinity and
specificity as rituximab.” Biogen Idec, Inc. v. Glax-
oSmithKline LLC, No. 10-CV-00608, 2011 U.S. Dist.
LEXIS 120043, at *31 (S.D. Cal. Oct. 17, 2011).
 BIOGEN IDEC   v. GLAXOSMITHKLINE                         5
say as construed by the district court “bind[s] to the same
epitope”; applicants said “binds to CD20.” 2
    Applicants’ statements—when considered in light of
either the range of antibodies included in the claim, or the
specific epitope to which the antibodies might attach—fail
to meet the “clear and unmistakable” standard set forth
in our case law. This is especially true given our case law
that it is the applicant, not the examiner, who disclaims
claim scope. See Innova/Pure Water, Inc. v. Safari Water
Filtration Sys., Inc., 381 F.3d 1111, 1124 (Fed. Cir. 2004);
see also Sorensen v. Int’l Trade Comm’n, 427 F.3d 1375,
1379 (Fed. Cir. 2005). It was the examiner, not the appli-
cants, who invoked the concept of epitopes. Compare J.A.
307-09 with J.A. 324-28. But it is the applicant, not the
examiner, who must give up or disclaim subject matter
that would otherwise fall within the scope of the claims,
and an applicant’s silence regarding statements made by
the examiner during prosecution cannot amount to a clear
and unmistakable disavowal of claim scope.               See
Sorensen, 427 F.3d at 1379; see also Salazar v. Procter &
Gamble Col., 414 F.3d 1342, 1345 (Fed. Cir. 2005).
    Nothing in the intrinsic record made by the applicants
links the efficacy of the recited antibodies to a particular
epitope of CD20. To the contrary, the intrinsic evidence
repeatedly links the efficacy of the antibodies to their
ability to selectively target the CD20 antigen, as opposed
to other antigens. See, e.g., J.A. 44-45 (’612 patent, dis-
cussing the inventive concept of targeting the CD20
antigen, and incorporating the ’137 patent by reference);


    2   Applicants’ comment and the district court’s con-
struction both state “with similar affinity and specificity
as [RITUXAN®]” after discussing where the binding
occurs. Therefore, the fundamental difference between
the applicants’ comment and the construction is the
district court’s limitation of binding to a specific epitope.
6                           BIOGEN IDEC   v. GLAXOSMITHKLINE
J.A. 325-26 (prosecution history, linking the efficacy of the
antibodies to their ability to bind CD20); J.A. 376 (’137
patent, discussing the inventive concept of targeting the
CD20 antigen).
     Nowhere in the prosecution history did the applicants
state that antibodies that bind to the same epitope on
CD20 with similar affinity and specificity as RITUXAN®
must be used, or that antibodies lacking those character-
istics must not be used. To the contrary, the applicants
repeatedly made clear—including in the same discussion
as the allegedly disclaiming statement—that because the
invention was based on the discovery that anti-CD20
antibodies could treat CLL, the claimed methods were not
limited to the use of any particular type anti-CD20 anti-
body. See, e.g., J.A. 325-26 (arguing that “the novelty of
the presently claimed invention does not lie in an anti-
CD20 antibody per se” and that anti-CD20 “antibodies to
be designed in the future for use in the claimed methods
would certainly be encompassed”).
    By ignoring most of the prosecution history and read-
ing something into the above dialogue between the exam-
iner and the applicants that is not there, it is possible to
argue, as GSK has done, that the “anti-CD20 antibodies”
that may be used in the claimed methods are limited to
only RITUXAN®-like antibodies. But it is at least equally
possible, and more correct, to read the applicants’ prose-
cution arguments as contemplating the use of antibodies
other than RITUXAN®-like antibodies. And when a
prosecution argument is subject to more than one reason-
able interpretation, it cannot rise to the level of a clear
and unmistakable disclaimer. 01 Communique Lab. Inc.
v. LogMeIn, Inc., 687 F.3d 1292, 1297 (Fed. Cir. 2012).
We have long followed the rule that even a poorly-phrased
prosecution argument does not a disclaimer make.
    Finally, the ’612 patent incorporates by reference the
’137 patent, which has a broader definition than the
 BIOGEN IDEC   v. GLAXOSMITHKLINE                         7
majority’s claim construction for “anti-CD20 antibody.”
The majority opinion tries to distinguish the ’137 patent’s
definition as only applying “herein”—or, in other words, in
the ’137 patent. See Maj. Op. at 13. This distinction
misses the mark.
     First, what the majority opinion dismisses as the
“special definition” of “anti-CD20 antibody” found in the
’137 patent is contained in the incorporated patent, not in
the incorporating one. Thus, even assuming that the
applicants of the ’137 patent were acting as their own
lexicographer when broadly defining the term “anti-CD20
antibody,” the ’612 patent then incorporated this “special
definition” into its own disclosure. Indeed, that is the
whole point of incorporation by reference—to incorporate
disclosure from another application. If there was ever any
doubt on this point, the prosecution history explicitly
affirms the reliance on the ’137 patent with respect to the
antibodies at issue. And this affirmation occurs right in
the middle of the allegedly disclaiming discussion of the
CD20 antibody relied upon by the majority. See J.A. at
324-25.
    As I read the record, it was error for the district court
to construe the claims as requiring the use of
“[RITUXAN®] and antibodies that bind to the same
epitope of the CD20 antigen with similar affinity and
specificity as [RITUXAN®].” Biogen Idec, Inc., 2011 U.S.
Dist. LEXIS 120043 at *31. Because the district court’s
construction eviscerates the “clear and unmistakable”
requirement for prosecution disclaimer, I cannot join the
majority in affirming that erroneous construction. I
would reverse the district court’s claim construction in
favor of the plain meaning of “anti-CD20 antibody” as set
8                         BIOGEN IDEC   v. GLAXOSMITHKLINE
out at the beginning of this opinion, and remand for
further proceedings under the proper claim construction. 3




    3  Given the breadth of the plain meaning construc-
tion, nothing in this analysis precludes GSK on remand
from the opportunity to raise the issue of validity on the
grounds that were troubling the examiner, and which the
alleged disclaimer is purported to address.
