  United States Court of Appeals
      for the Federal Circuit
                ______________________

     SENJU PHARMACEUTICAL CO., LTD.,
   KYORIN PHARMACEUTICAL CO., LTD., AND
             ALLERGAN, INC.,
             Plaintiffs-Appellants,

                           v.

         APOTEX INC. AND APOTEX CORP.,
               Defendants-Appellees.
              ______________________

                      2013-1027
                ______________________

    Appeal from the United States District Court for the
District of Delaware in No. 11-CV-1171, Judge Sue L.
Robinson.
                ______________________

               Decided: March 31, 2014
               ______________________

    RICHARD D. KELLY, Oblon, Spivak, McClelland, Maier,
& Neustadt, L.L.P., of Alexandria, Virginia, argued for
plaintiffs-appellants. With him on the brief were
STEPHEN G. BAXTER, FRANK J. WEST, and TIA D. FENTON.

   HUGH S. BALSAM, Locke Lord LLP, of Chicago, Illinois,
argued for defendants-appellees. With him on the brief
were SCOTT B. FEDER, DAVID B. ABRAMOWITZ, PATRICK C.
GALLAGHER, of Chicago, Illinois, and ALAN B. CLEMENT, of
New York, New York.
2                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



                  ______________________

Before NEWMAN, PLAGER, and O’MALLEY, Circuit Judges.
    Opinion for the court filed by Circuit Judge PLAGER.
    Dissenting opinion filed by Circuit Judge O’MALLEY.
PLAGER, Circuit Judge.
    This is a patent case calling on us to consider the ap-
plication of claim preclusion doctrine (res judicata) to a
second suit on the same patent based on amended claims
resulting from a re-examination of the patent. Plaintiffs-
Appellants Senju Pharmaceutical Co., Ltd., Kyorin Phar-
maceutical Co., Ltd., and Allergan, Inc. (collectively
referred to as “Senju”) filed suit in the United States
District Court for the District of Delaware against De-
fendants-Appellees Apotex Inc. and Apotex Corp. (“Apo-
tex”). Plaintiffs alleged infringement of certain claims of
Senju’s reexamined U.S. Patent No. 6,333,045 (the ’045
patent).
    In response, Apotex filed a motion to dismiss Senju’s
lawsuit. Apotex argued that Senju had asserted the same
’045 patent against Apotex in a previous infringement
action (the “first action”) prior to the ’045 patent’s reex-
amination, and therefore Senju’s subsequent action for
infringement of the reexamined ’045 patent (the “second
action”) was barred by the doctrine of claim preclusion.
The district court agreed and granted Apotex’s motion to
dismiss. Senju now appeals.
    For the reasons that follow, we conclude that Senju’s
action for infringement was properly dismissed as barred
by claim preclusion, and therefore affirm the district
court’s ruling.
                     I.   BACKGROUND
    The ’045 patent relates to an ophthalmic solution for
eye drops that contains the drug Gatifloxacin. Gatifloxa-
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                3



cin is an antimicrobial agent used to kill various types of
bacteria. When treating the eye with Gatifloxacin, tear
dilution and the outer layer of the eye, the cornea, can
prevent the Gatifloxacin from passing into and treating
the space between the cornea and the lens of the eye, the
aqueous humor. ’045 patent col.1 ll.27–34.
    The ’045 patent discloses a pharmaceutical solution
that resolves this problem by combining the Gatifloxacin
with disodium edetate (“EDTA”).         Id. col.1 ll.54–61.
EDTA helps expand the intercellular spaces of the cornea,
accelerating the passage of Gatifloxacin solution into the
eye. Id. The ’045 patent as originally issued in December
2001 claimed this combination of Gatifloxacin and EDTA.
    Pursuant to the terms of the Hatch-Waxman Act
(Pub.L. No. 98–417, 98 Stat. 1585) (“the Act”), Apotex in
July 2007 filed an Abbreviated New Drug Application
(“ANDA”) (No. 79-084) with the Food and Drug Admin-
istration (“FDA”). The application requested approval to
manufacture, market, and sell a generic version of the
Gatifloxacin ophthalmic solution covered by the ’045
patent. Apotex filed the Paragraph IV notice specified by
the Act, which places the patent-holder on notice of the
application. In response, in November 2007 Senju filed
its first action against Apotex, arguing that Apotex’s
ANDA and any manufacture of Gatifloxacin ophthalmic
solution were acts of infringement of the ’045 patent
claims 1–3 and 6–9 under the Act.
    The district court held a bench trial, and in June
2010 the district court issued findings of fact and conclu-
sions of law under Rule 52(a). At that time the court held
that, though the ANDA product infringed claims 1–3, 6, 7,
and 9 of the ’045 patent, claims 1–3 and 6–9 were invalid
as obvious. Senju Pharm. Co. v. Apotex Inc., 717 F. Supp.
2d 404, 433 (D. Del. 2010). Senju then filed a motion for a
new trial or to amend the district court’s judgment and
findings, specifically regarding the validity of claim 7.
4                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



     Over one year passed while the district court ad-
dressed this and other issues. In December 2011 the
district court again concluded that claim 7 was invalid on
the ground of obviousness, and it entered final judgment
in the case. Senju Pharm. Co. v. Apotex Inc., 836 F. Supp.
2d 196 (D. Del. 2011). In due course, the judgment was
affirmed by this court. See 485 F. App’x 433 (Fed. Cir.
2012).
    In the gap between the district court’s issuance in
June 2010 of its findings of fact and conclusions of law
under Rule 52(a), and its entry of final judgment in the
case in December 2011, the patentee Senju filed, in Feb-
ruary 2011, with the U.S. Patent and Trademark Office
(“PTO”) a request for reexamination of claims 1–3, 6, 8,
and 9 of the ’045 patent. The PTO granted reexamination
in April 2011. In response to an initial rejection on the
ground of obviousness, Senju amended claim 6 to include
several additional limitations, including the amount of
Gatifloxacin, the amount of EDTA, and the pH. Senju
also added new independent claim 12 with similar limita-
tions. In October 2011, the PTO issued a reexamination
certificate cancelling claims 1–3 and 8–11, and certifying
amended claim 6, new independent claim 12, and new
dependent claims 13–16 as patentable.
    On November 28, 2011, still in the gap prior to the en-
try of final judgment in the first action, Senju filed a new
action against Apotex, seeking a declaratory judgment
that Apotex’s manufacture, use, or sale of Gatifloxacin
ophthalmic solution infringed claims 6 and 12–16 set
forth in the reexamination certificate of the ’045 patent.
     In January 2012, several weeks after the district
court issued its final judgment in the first case, Apotex
filed a Rule 12(b)(6) motion to dismiss this second suit,
arguing that Senju was precluded from asserting the
reexamined ’045 patent in the second action under the
doctrine of claim preclusion. Apotex argued that Senju’s
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                  5



second action involved the same cause of action that
Senju asserted in its first action.
    The district court agreed that Senju had asserted the
same cause of action in its second action that it had
asserted in its first action. The district court reached this
conclusion because “none of the claims [that Senju] added
or amended during reexamination were broader than
their predecessors,” and the reexamined claims “[did] not
create any new cause of action that plaintiffs lacked
under the original version of the patent.” Senju Pharm.
Co. v. Apotex Inc., 891 F. Supp. 2d 656, 662 (D. Del. 2012).
The district court therefore granted Apotex’s motion to
dismiss the second action, rendering final judgment for
Apotex. Id. This appeal by the patentee Senju of the
dismissal of its suit followed.
   We have jurisdiction to decide Senju’s appeal based
upon 28 U.S.C. § 1295(a).
                      II. DISCUSSION
            A. Principles of Claim Preclusion
    Senju’s appeal requires us to decide whether Senju’s
second action is barred by the judicial doctrine now gen-
erally known as claim preclusion, earlier known as res
judicata and still referred to by that name. “[U]nder the
doctrine of res judicata, a judgment ‘on the merits’ in a
prior suit involving the same parties or their privies bars
a second suit based on the same cause of action.” Lawlor
v. Nat’l Screen Serv. Corp., 349 U.S. 322, 326 (1955).
    The underlying policies that the doctrine of claim pre-
clusion is designed to further are considerations of effi-
ciency and finality:
    The general rule of res judicata applies to repeti-
    tious suits involving the same cause of action. It
    rests upon considerations of economy of judicial
    time and public policy favoring the establishment
6                  SENJU PHARMACEUTICAL CO.    v. APOTEX INC.



    of certainty in legal relations. The rule provides
    that when a court of competent jurisdiction has
    entered a final judgment on the merits of a cause
    of action, the parties to the suit and their privies
    are thereafter bound “not only as to every matter
    which was offered and received to sustain or de-
    feat the claim or demand, but as to any other ad-
    missible matter which might have been offered for
    that purpose.”
C.I.R. v. Sunnen, 333 U.S. 591, 597 (1948) (quoting
Cromwell v. Sac Cnty., 94 U.S. 351, 352 (1876)).
     Whether a cause of action is barred by claim preclu-
sion is a question of law that we review without defer-
ence. Acumed LLC v. Stryker Corp., 525 F.3d 1319, 1323
(Fed. Cir. 2008). We look to the law of the regional circuit
in which the district court sits for guidance regarding the
principles of claim preclusion; however, whether a partic-
ular cause of action in a patent case is the same as or
different from another cause of action has special applica-
tion to patent cases, and we therefore apply our own law
to that issue. Id. at 1323.
     Under Third Circuit law, the home circuit of the dis-
trict court in this case, claim preclusion principles re-
quire: “(1) a final judgment on the merits in a prior suit
involving[ ] (2) the same parties or their [privies]; and (3)
a subsequent suit based on the same cause of action.”
CoreStates Bank, N.A. v. Huls Am., Inc., 176 F.3d 187,
194 (3d Cir. 1999). In this case, both parties agree that
Senju meets the first two of the three requirements for
claim preclusion—that is, Senju’s first action resulted in a
final judgment on the merits, and both the first and
second actions involved the same parties.
    The parties disagree, however, regarding the third re-
quirement—whether Senju’s first and second actions were
based on the same cause of action. That is the central
issue of this appeal.
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                  7



    In applying the policies expressed by the doctrine of
claim preclusion, our court has identified certain signifi-
cant factors to be considered in determining when a cause
of action is the same. In Acumed, we followed the ap-
proach in the Restatement (Second) of Judgments, which
states that a cause of action is defined by the transaction-
al facts from which it arises, and the extent of the factual
overlap. 525 F.3d at 1323–24 (citing Restatement (Sec-
ond) of Judgments § 24 (1982)); see also United States v.
Tohono O’Odham Nation, 131 S. Ct. 1723, 1730 (2011)
(“The now-accepted test in preclusion law for determining
whether two suits involve the same claim or cause of
action depends on factual overlap.”).
    A word of caution. Use of the term “claim” can cause
confusion in a patent case involving claim preclusion law.
In patent law, a “claim” is a substantive part of the patent
document and plays a critically important role in in-
fringement litigation. In civil procedure, and particularly
in discussions regarding preclusion law, “claim” is equiva-
lent to “cause of action”—the name “claim preclusion”
means preclusion of a cause of action. Whenever possible,
other than in referring to the name of the doctrine itself,
we will use the longer descriptor “cause of action” when
discussing claim preclusion issues; the term “claim” will
be used to refer to patent claims. Note, however, that
cited texts and judicial opinions may use “claim” and
“cause of action” interchangeably.
     One of the areas of factual overlap that we consider
in a patent case involving claim preclusion is the overlap
of the product or process accused in the instant action
with the product or process accused in the prior action. If
the products or processes are essentially the same, then
claim preclusion may apply. Acumed, 525 F.3d at 1324
(stating that “claim preclusion does not apply unless the
accused device in the action before the court is ‘essentially
the same’ as the accused device in a prior action between
the parties that was resolved by a judgment on the mer-
8                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



its”) (quoting Foster v. Hallco Mfg. Co., 947 F.2d 469, 479–
80 (Fed. Cir. 1991)).
     We also consider whether the same patents are in-
volved in both suits. Ordinarily, “[e]ach patent asserted
raises an independent and distinct cause of action.”
Kearns v. Gen. Motors Corp., 94 F.3d 1553, 1555 (Fed. Cir.
1996). Claim preclusion will generally apply when a
patentee seeks to assert the same patent against the
same party and the same subject matter. Id. at 1557
(concluding that five patents already asserted against the
same party in a previous action were properly dismissed
on res judicata grounds); Transclean Corp. v. Jiffy Lube
Int’l, Inc., 474 F.3d 1298, 1305 (Fed. Cir. 2007) (noting
that two cases involved the same cause of action because
the cases included the same patent and the same accused
devices). How this general rule is to be understood is a
key issue in this case.
      B. Application of Claim Preclusion Principles
                             1.
    With the preceding legal principles in mind, we turn
to the question of factual overlap of Apotex’s first and
second actions. The first area of overlap to be considered
is whether the products in the first and second actions are
“essentially the same.”
    In a case such as this, the ‘product’ is the drug de-
scribed in the ANDA. See Roche Palo Alto LLC v. Apotex,
Inc., 531 F.3d 1372, 1380 (Fed. Cir. 2008) (reviewing for
purposes of claim preclusion whether a first ANDA formu-
lation and a second ANDA formulation were “essentially
the same”). The drug described in an ANDA can be
viewed as the ‘product’ for claim preclusion purposes even
though the accused infringer has not yet made, used, or
sold the drug. This legal fiction—the fiction of a ‘product’
that may never have been made, used, or sold in the
United States by the alleged infringer—exists because the
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                9



filing of an ANDA creates a statutory act of infringement.
35 U.S.C. § 271(e)(2)(A); Bayer Schering Pharma AG v.
Lupin, Ltd., 676 F.3d 1316, 1318 (Fed. Cir. 2012) (“[T]he
Hatch–Waxman Act creates a mechanism that allows for
prompt judicial determination of whether the ANDA
applicant’s drug or method of using the drug infringes a
valid patent. The Act makes it an act of infringement to
file an ANDA for a drug or for a use of the drug that is
claimed in a patent.”).
     In its first suit, Senju alleged infringement based on
Apotex’s ANDA No. 79-084 and its described Gatifloxacin
ophthalmic solution. J.A. 104–05. In its second suit, this
case, Senju requested a declaratory judgment of infringe-
ment based on Apotex’s submission of the same ANDA
(No. 79-084). J.A. 124–25. Thus, both actions involve the
same Gatifloxacin ophthalmic solution described in ANDA
No. 79-084. Because the product in the second action
completely overlaps with the product in the first action,
there is on that basis no new cause of action.
                            2.
     The more difficult question is whether the same pa-
tent, or more precisely the same patent rights, were
involved in both suits. Senju argues that the reexamina-
tion created a new cause of action because the reexamined
patent claims are substantially different from the claims
in the original ’045 patent. The reexamined claims are
different according to Senju because they include the
amount of Gatifloxacin or its salt, the pH range, and the
amount of EDTA, none of which are included in the
original claims.
    Senju argues that, under our precedents, the district
court was required to consider these as new claims and
determine whether the claims as a whole are “substantial-
ly the same” in accordance with its understanding of the
analysis outlined in Aspex Eyewear, Inc. v. Marchon
Eyewear, Inc., 672 F.3d 1335, 1340-42 (Fed. Cir. 2012).
10                 SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



Senju contends that the district court erred by dismissing
its case as barred by claim preclusion without performing
this analysis.
    Apotex responds that the district court correctly dis-
missed Senju’s case. According to Apotex, in order for
Senju to comply with the statutory requirements for
reexamination outlined in 35 U.S.C. § 305, the claim
scope of its reexamined ’045 claims had to be the same as
or narrower than the claim scope of the original ’045
claims. Since the claim scope of Senju’s reexamined ’045
claims was subsumed by the claim scope of its original
claims, Apotex contends that the ’045 reexamined patent
did not give Senju any additional rights against Apotex’s
product that Senju did not already possess in its first
lawsuit.
    Apotex argues that, under its understanding of Aspex,
reexamined claims cannot create a new cause of action
that did not exist before. According to Apotex, Senju has
engaged in ‘claim splitting,’ and its second suit, the in-
stant suit, is barred by claim preclusion.
    On these facts we believe Apotex has the better ar-
gument. The argument can be viewed in terms of the
cause of action in each suit. Senju’s focus is on the patent
claims in the first suit. Senju’s theory is based on the
patent claims that are found in the original patent and
the cause of action thereunder; the cause of action in the
second suit is based on the new or amended patent claims
now in the patent as a result of the re-examination.
According to Senju, in order to determine whether a cause
of action for infringement is the same in both suits, the
differences between the patent claims must be examined
to determine whether there are substantial differences, in
which case the causes of action are different. Senju
argues that the failure of the trial court to have made
detailed comparisons requires a remand for that to be
done.
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                 11



    Apotex’s response focuses on whether it is the same
patented invention, and only derivatively on whether the
patent claims asserted in each of the suits are the same or
substantially the same. Apotex argues that the narrower
claims that resulted from this reexamination, claims that
presumably now avoid the prior art that rendered the
original claims invalid, are necessarily subsets of those
broader claims and therefore their subject matter was
included in the original infringement suit. Apotex further
argues that Senju’s reliance on cases that involve reissue
of a patent is misplaced, since reissue can result in broad-
ened claims under certain circumstances, whereas reex-
amination does not permit broadening.
    Both parties cite to and find support for their posi-
tions in language found in our recent case of Aspex Eye-
ware. The history of that litigation—involving a long
series of court battles between the several parties—is
convoluted and need not be laid out here.
    What is important for our understanding of this cir-
cuit’s claim preclusion law is that the opinion in Aspex
addressed four separate issues. First was the issue in
this case: whether a new cause of action arose as a result
of the reexamination that had occurred; second was
whether the same product was at issue in both cases (it
was not an ANDA case); third was the effect of a settle-
ment agreement between the parties; and fourth were
certain claim construction issues the court undertook to
address.
    In the course of discussing the various issues the opin-
ion made statements that, taken out of their context,
could be read as relating to the first issue, that is, wheth-
er a new cause of action was created by the reexamina-
tion.    For purposes of determining our precedents
regarding that issue, it is only the first section of the
discussion in Aspex to which we must attend.
12                  SENJU PHARMACEUTICAL CO.    v. APOTEX INC.



    Regarding claim preclusion, the opinion summarized
patentee Aspex’s argument in essentially the same terms
as plaintiff Senju has made here:
     Aspex’s main argument is that res judicata does
     not bar this action, because Aspex’s claims in this
     case are based on claims [ ] amended and added in
     reexamination. Because those claims were not in
     existence (at least not in the same form) at the
     time the prior actions were filed against [the de-
     fendants], Aspex argues that the new claims cre-
     ated new causes of action that Aspex could not
     have pursued in the previous cases. Accordingly,
     Aspex argues, res judicata does not bar it from
     pursuing the claims in this case.
Id. at 1340–41.
    The court rejected that argument, starting its discus-
sion with:
     Amended [ ] and new claim[s] of the reexamined
     [ ] [’]545 patent did not create new causes of action
     for Aspex, separate from the causes of action cre-
     ated by the original [ ] [’]545 patent. Those two
     claims were merely new versions of claims that
     were part of the [ ] [’]545 patent prior to its reex-
     amination.
Id. at 1341.
    The court in its conclusion of the discussion of this is-
sue said,
     [c]onsistent with that rule [the rule that new
     claims that emerge from reexamination must not
     be broader than the original claims], the claims on
     which Aspex relies are not broader than their
     predecessor; they therefore did not create a new
     legal right against infringement that Aspex lacked
     under the original version of the patent.
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                 13



Id. at 1342.
     In between the start and the conclusion, the Aspex
court pointed out two reasons why the patentee’s reliance
on cases involving reissued patents was in error. Unlike
reissue, reexamination does not result in the surrender of
the original patent and the issuance of a new patent.
Furthermore, the court noted, the two claims on which
Aspex relied are different only in the additional limiting
characteristics that were added, and thus were not “mate-
rially different” from the original claim, and did not create
a new cause of action that was not previously available.
Id.
    In this case we reach the same conclusion that the
Aspex court did—claims that emerge from reexamination
do not in and of themselves create a new cause of action
that did not exist before. We reach this conclusion be-
cause a so-called “reexamined patent” is the original
patent; it has just been examined another time as indicat-
ed in its reexamination certificate. 1 Reexamination does
not involve the filing of a new patent application nor the
issuance of a new patent.
    The reexamination process does permit some amend-
ment of the patent and its claims, but any amendment
that occurs during reexamination is statutorily con-
strained. For example, amendments to the disclosure
cannot introduce new matter. 35 U.S.C. § 132(a) (“No
amendment shall introduce new matter into the disclo-



    1   After reexamination, the PTO issues a reexamina-
tion certificate that memorializes the results of the reex-
amination process.       The reexamination certificate
identifies the patent and “confirm[s] any claim of the
patent determined to be patentable, and incorporat[es] in
the patent any proposed amended or new claim deter-
mined to be patentable.” 35 U.S.C. § 307(a).
14                 SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



sure of the invention”); 35 U.S.C. § 112, ¶ 1 (2011); Ariad
Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed.
Cir. 2010) (stating that the disclosure must “‘clearly allow
persons of ordinary skill in the art to recognize that [the
inventor] invented what is claimed’”) (citing Vas-Cath Inc.
v. Mahurkar, 935 F.2d 1555, 1563 (Fed. Cir. 1991)).
    Any change to the original patent is further con-
strained by 35 U.S.C. § 305, which states that “[n]o pro-
posed amended or new claim enlarging the scope of a
claim of the patent will be permitted in a reexamination
proceeding under this chapter.” We have strictly inter-
preted § 305 to prohibit any broadening amendments.
The reexamined claim cannot be broader in any respect,
even if it is narrowed in other respects. Predicate Logic,
Inc. v. Distributive Software, Inc., 544 F.3d 1298, 1303
(Fed. Cir. 2008). Therefore, while reexamination can
make certain changes in the patent, such changes are
strictly circumscribed by the original patent’s disclosure
and claim scope.
    As a result, a reexamined patent claim cannot contain
within its scope any product or process which would not
have infringed the original claims. Id. Put another way,
because the patent right is a right to exclude whose outer
boundary is defined by the scope of the patent’s claims, as
explained in Aspex, reexamination does not provide larger
claim scope to a patentee than the patentee had under the
original patent claims.
    The court in Aspex held that the original patent
claims in that case and the issued reexamination claims
were not materially different. This led Senju to argue
that in every case it is necessary to make that factual
determination in detail. But that is an unwarranted
extension of the point. Both in Aspex and in this case the
district court could readily ascertain that the reexamined
claims were essentially the original claims with the
addition of limitations designed to avoid prior art. In
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                15



Aspex the appellate court noted that fact; in our case the
trial court noted that the amended and new claims were
essentially the original claims with limiting words added. 2
    Whether it is possible that a reexamination could ever
result in the issuance of new patent claims that were so
materially different from the original patent claims as to
create a new cause of action, but at the same time were
sufficiently narrow so as not to violate the rule against
reexamined claims being broader than the original claims,
is a question about which we need not opine—that is not
the case before us. We hold that, in the absence of a clear
showing that such a material difference in fact exists in a
disputed patentable reexamination claim, it can be as-
sumed that the reexamined claims will be a subset of the
original claims and that no new cause of action will be
created. This applies whether the judgment in the origi-
nal suit was based on invalidity of the claims or simply on
non-infringement.
    We conclude, as the court did in Aspex, that the
claims in this case that emerged from reexamination do
not create a new cause of action that did not exist before.
Senju cannot sue Apotex on the same patent twice.
    At its core, what Senju seeks is a do-over. Having lost
its suit, Senju seeks to use reexamination to obtain a
second bite at the apple, to assert its patent against the
same party, Apotex, and the same product, the Gatifloxa-


   2    “Claim 6 was amended to add limiting words.
Claim 12 is similar to canceled claim 1, except that it adds
the gatifloxacin concentration, EDTA concentration, and
pH characteristics. Claims 13 through 15 are dependent
on claim 12, and claim 16 is dependent on claim 15.
Consequently, claims 6 and 12–16 are all narrower in
scope than the original claims.” Senju Pharma. Co. v.
Apotex Inc., 891 F. Supp. 2d 656, 662 (D. Del. 2012).
16                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



cin ophthalmic solution described in ANDA No. 79-084.
But that is exactly what claim preclusion was designed to
prevent. Claim preclusion “applies to repetitious suits
involving the same cause of action.” C.I.R., 333 U.S. at
597. Claim preclusion exists to “encourage[ ] reliance on
judicial decisions, bar[ ] vexatious litigation, and free[ ]
the courts to resolve other disputes.” Brown, 442 U.S. at
131.
    Senju raises several additional arguments about pur-
ported differences between its first and second suits based
on issues of proof under the new patent claims. We have
examined these additional arguments and find them
without merit, for the accused products are the same in
both actions. Although Senju criticizes the district court’s
opinion, in any event that argument is immaterial since
“[w]e sit to review judgments, not opinions.” Stratoflex,
Inc. v. Aeroquip Corp., 713 F.2d 1530, 1540 (Fed. Cir.
1983).
     Senju concedes that all of the elements of claim pre-
clusion are met save the last: whether its first and second
suits were based on the same cause of action. Because we
conclude that the facts of Senju’s first and second actions
overlap and the reexamination of the ’045 patent did not
create a new cause of action, the resolution of this case is
straightforward: Senju’s suit against Apotex is barred on
the principles of claim preclusion. For these reasons, we
affirm the district court’s dismissal of Senju’s suit.
                      III. CONCLUSION
     The judgment of the district court is affirmed.
                        AFFIRMED
  United States Court of Appeals
      for the Federal Circuit
                 ______________________

      SENJU PHARMACEUTICAL CO., LTD.,
    KYORIN PHARMACEUTICAL CO., LTD., AND
              ALLERGAN, INC.,
              Plaintiffs-Appellants,

                            v.

         APOTEX INC. AND APOTEX CORP.,
               Defendants-Appellees.
              ______________________

                       2013-1027
                 ______________________

    Appeal from the United States District Court for the
District of Delaware in No. 11-CV-1171, Judge Sue L.
Robinson.
                ______________________
O’MALLEY, Circuit Judge, dissenting.
    The dispositive issue in this case is whether Senju’s
reexamined claims granted new patent rights that Senju
could not have asserted in its first lawsuit against Apotex.
The majority says that, “a so-called ‘reexamined patent’ is
the original patent.” Maj. Op. at 13 (emphasis added).
Under the majority’s reasoning, after a patentee asserts a
patent’s original claims in one lawsuit, a subsequent
lawsuit asserting the patent’s reexamined claims against
the same defendant is an improper attempt to revisit a
patent that has already been adjudicated. But, it is the
rights created by a patent that are adjudicated, and it is
2                  SENJU PHARMACEUTICAL CO.    v. APOTEX INC.



on whether new rights were obtained through reexamina-
tion that I believe we must focus.
     Although reexamined claims cannot be broader in
scope than original claims, they sometimes grant broader
rights than original claims. This case illustrates this fact.
In Senju’s first action against Apotex, the district court
ruled that the asserted original claims of U.S. Patent No.
6,333,045 were invalid as obvious, meaning that Senju
had no rights at all under these claims. Senju Pharm. Co.
v. Apotex Inc., 836 F. Supp. 2d 196, 210–11 (D. Del. 2011)
aff’d, 485 F. App’x 433 (Fed. Cir. 2012); Senju Pharm. Co.
v. Apotex Inc., 717 F. Supp. 2d 404, 433 (D. Del. 2010).
The narrowed claims that emerged from reexamination
after the first lawsuit was filed but before final judgment
was entered in that action were presumptively valid,
however, and may have—for the first time—given Senju
actionable legal rights. See Superior Fireplace Co. v.
Majestic Prods. Co., 270 F.3d 1358, 1367 (Fed. Cir. 2001)
(noting that the presumption of validity applies to reex-
amined claims). If reexamination did, in fact, create
rights that did not exist in time for Senju to assert them
in the first action against Apotex, claim preclusion should
not prevent Senju from asserting its new rights in this
action. See Lawlor v. Nat’l Screen Serv. Corp., 349 U.S.
322, 328 (1955) (a prior judgment “cannot be given the
effect of extinguishing claims which did not even then
exist and which could not possibly have been sued upon in
the previous case”). To rule otherwise would fault Senju
for failing to raise claims that did not exist—a problemat-
ic result that the majority’s analysis would allow.
    Determining whether the ’045 patent’s reexamined
claims actually provided Senju new rights requires com-
paring the reexamined claims with the patent’s original
claims. Only if the reexamined claims are substantially
the same as Senju’s original claims can we conclude that
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                  3



the reexamined claims cover rights that could have been
asserted in the first action against Apotex. 1 Because the
district court failed to conduct this necessary comparison,
I would vacate its judgment and remand for further
analysis. Accordingly, I respectfully dissent.
                             I.
    The doctrine of claim preclusion applies in only two
ways: (1) to prevent a party from relitigating claims that
have already been resolved, and (2) to bar a party from
bringing certain claims that could have been brought in a
prior lawsuit. See Federated Dep’t Stores, Inc. v. Moitie,
452 U.S. 394, 398 (1981) (“There is little to be added to
the doctrine of res judicata as developed in the case law of
this Court. A final judgment on the merits of an action
precludes the parties and their privies from relitigating
issues that were or could have been raised in that ac-


    1   Importantly, neither the majority nor Apotex con-
tends that Senju’s reexamined claims could have been
asserted in the original action. Although Senju’s reex-
amined claims issued before final judgment was entered
in the first action, Senju did not have an opportunity to
bring its reexamined claims in that case. A judgment had
been entered in the first litigation prior to the issuance of
Senju’s reexamined claims. When the reexamined claims
issued, the district court had reopened the record—but
only for the limited purpose of allowing additional testi-
mony regarding the validity of claim 7 of the ’045 patent.
If Senju’s reexamined claims could have been brought in
the original action, then traditional principles of claim
preclusion would bar claims for past infringement, and
the doctrine set forth in Kessler v. Eldred, 206 U.S. 285
(1907), might well bar claims of infringement with respect
to actions occurring post-judgment, despite our holding in
Aspex. See Brain Life, LLC v. Elekta Inc., No. 2013-1239
(Fed. Cir. ___, 2014). That is not this case, however.
4                 SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



tion.”); CoreStates Bank, N.A. v. Huls Am., Inc., 176 F.3d
187, 194 (3d Cir. 1999). We expect parties to bring all
their mature claims arising from the same set of facts in a
single lawsuit, and not to dispute rights that have already
been determined. But we have never expected parties to
assert rights that they do not have. See Lawlor, 349 U.S.
at 328; see also Alexander & Alexander, Inc. v. Van Impe,
787 F.2d 163, 166 (3d Cir. 1986) (noting that res judicata
“does not bar claims arising subsequent to the entry of [a
prior] judgment and which did not then exist or could not
have been sued upon in the prior action”). Nonetheless,
the majority seems to introduce such an expectation into
our case law today—requiring patentees to assert rights
they have, or may later acquire, in a single lawsuit. This
unprecedented expansion of the doctrine of claim preclu-
sion is not one that I endorse.
    The majority correctly observes that “a reexamined
claim cannot contain within its scope any product or
process which would not have infringed the original
claims.” Maj. Op. at 14. Claims cannot be broadened
through reexamination under 35 U.S.C. § 305. Thus, if a
product does not infringe a patent’s original claims, the
product necessarily will not infringe any of that patent’s
reexamined claims. Consequently, if a court enters final
judgment that a product does not infringe a patent’s
original claims, then the product’s noninfringement of any
reexamined claims is already “a thing adjudicated,” and
traditional notions of claim and issue preclusion collec-
tively would prevent a party from asserting infringement
of the reexamined claims in a subsequent action. See
Black’s Law Dictionary (9th ed. 2009) (translating “res
judicata” as “a thing adjudicated”). In other words, when
infringement is the only consideration, reexamined claims
cannot expand a patentee’s rights beyond those granted
by the original claims.
    The majority, however, does not consider how issues
of validity affect the preclusion analysis. With respect to
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                 5



infringement, a product that does not infringe a broad
original claim will, in every instance, not infringe a nar-
rower reexamined claim (or a reexamined claim of identi-
cal scope to an original claim). But, the same analysis
does not apply to validity determinations. Here, Senju’s
original claims were invalidated, meaning that they
provided Senju with no patent rights. Senju, 836 F. Supp.
2d at 210–11; Senju, 717 F. Supp. 2d at 433. This does
not mean that Senju necessarily had no patent rights
under its reexamined claims solely because they could not
be broader in scope than Senju’s original claims. During
reexamination of the ’045 patent, the United States
Patent and Trademark Office (“PTO”) considered the prior
art and arguments that led the district court to invalidate
Senju’s original asserted claims, as well as the district
court’s opinion holding those claims invalid. See Senju
Pharm. Co. v. Apotex Inc., 891 F. Supp. 2d 656, 658
(D. Del. 2012). The PTO agreed with the district court
that the original claims were obvious. See id. Senju,
however, narrowed the scope of its claims during reexam-
ination, and the PTO ultimately determined that these
narrowed claims were patentable. See id. at 658–59. The
reexamined claims that issued were presumptively valid
and, unlike the invalid original claims, may have provided
Senju with actionable patent rights (i.e., a new cause of
action).
    Despite the district court’s determination that the
’045 patent’s original claims were invalid, Senju’s right to
exclude under its reexamined claims was only “a thing
adjudicated” if those claims were substantially the same
as its original claims. Otherwise, Senju’s second lawsuit
against Apotex involved new patent rights and raised new
questions of validity and infringement that the courts
have never answered. The majority acknowledged that
the precise issue presented is “whether . . . the same
patent rights[ ] were involved in both suits,” as opposed to
whether “the same patents” were involved. Maj. Op. at 9
6                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



(emphases added). Despite this, the majority concludes
that it “need not opine” on “[w]hether it is possible that a
reexamination could ever result in the issuance of new
patent claims that were so materially different from the
original patent claims as to create a new cause of ac-
tion . . . .” Id. at 15. That issue, however, is squarely
presented here, and Senju’s reexamined and original
claims must be compared to determine whether reexami-
nation created a new cause of action. 2
                            II.
    The majority’s analysis is based largely on this court’s
decision in Aspex Eyewear, Inc. v. Marchon Eyewear, Inc.,
672 F.3d 1335 (Fed. Cir. 2012), but Aspex merely applied
traditional claim preclusion principles and does not
support the majority’s expansive view of the doctrine. In
2002, Aspex Eyewear, Inc. (“Aspex”) alleged that Revolu-
tion Eyewear, Inc. (“Revolution”) had infringed claims 6,
22, and 34 of a patent claiming magnetic clip-on eyewear.
Id. at 1338. The district court entered summary judg-
ment of noninfringement with respect to claims 6 and 34,
and granted summary judgment that claim 22 was in-
fringed and not invalid. Id. at 1338–39. In 2008, the PTO


    2   Before it would be appropriate to compare Senju’s
reexamined and original claims, the majority suggests
that there must be a “clear showing that . . . a material
difference in fact exists” between the original and reex-
amined claims. Maj. Op. at 15. The basis for requiring
this heightened showing or placing the burden on the
patentee is unclear. Because the majority has determined
that Senju has not shown such a material difference here,
moreover—where Senju’s reexamined claims are pre-
sumptively valid and its original claims have been ruled
invalid—it is difficult to imagine how a party could meet
the heightened requirement that the majority imposes
today.
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                7



completed a reexamination of the same patent, which,
among other things, allowed an amended version of claim
23 and allowed new claim 35, which depended from claim
23. Id. at 1339. In 2009, Aspex filed a separate lawsuit
against Revolution, asserting infringement of reexamined
claims 23 and 35. Id. at 1340. The district court deter-
mined that claim preclusion barred Aspex’s assertion of
its reexamined claims, and our court agreed that the
reexamined claims did not create rights beyond those
Aspex had under its original claims. Id. at 1340, 1342.
     Importantly, both the trial court in Aspex and our
court conducted the same type of analysis I would require
the district court to conduct here: comparing the patent’s
reexamined claims with its original claims to determine
whether they were substantially the same. See id. at
1340–42. After careful analysis, our court agreed with
the district court that Aspex’s newly asserted claims
“were merely new versions of claims that were part of
the . . . patent prior to its reexamination.” Id. at 1341.
We observed that the amendment to claim 23 during
reexamination was “insubstantial” and that the limitation
added by claim 35 was “an insignificant change.” Id.
Thus, because Aspex’s reexamined claims were substan-
tially the same as its original claims, we concluded that
no new grounds to assert infringement were presented
and that “allowing Aspex to pursue amended claim 23 and
new claim 35 . . . would present a clear instance of ‘claim
splitting,’ which is forbidden by the principles of res
judicata.” Id. (quoting Mars Inc. v. Nippon Conlux Ka-
bushiki–Kaisha, 58 F.3d 616, 619 (Fed. Cir. 1995)). In
short, in Aspex, we determined that Aspex’s reexamined
claims covered rights that could have been asserted prior
to reexamination—a traditional basis for applying claim
preclusion. Neither the district court nor the majority,
however, makes this critical determination here, render-
ing their analyses incomplete.
8                  SENJU PHARMACEUTICAL CO.   v. APOTEX INC.



    In expanding the reach of claim preclusion, the major-
ity highlights dicta in Aspex that I do not agree is appli-
cable to this case. In Aspex, we did state that “claims that
emerge from reexamination do not create a new cause of
action that did not exist before.” Id. at 1342 (citing Hoff-
man v. Wisner Classic Mfg. Co., 927 F. Supp. 67, 73
(E.D.N.Y. 1996)). But, in Aspex, none of the original
claims had been invalidated. We did not assess whether
entirely new patent rights might have emerged from
reexamination. The original case turned on whether the
accused products infringed the claims of the patent at
issue. Because we found the new claims coextensive with
the original claims, we found the noninfringement finding
in the first action controlling. Consequently, the state-
ment in Aspex that reexamination cannot create new
rights should have no bearing here, where the facts of the
case prove otherwise.
     Also missing from the discussion is the Aspex court’s
articulation of the principles that should govern here. In
Aspex, we expressly noted: “If a claim did not exist at the
time of the earlier action, it could not have been asserted
in that action and is not barred by res judicata.” Aspex,
672 F.3d at 1342. We stressed this idea again, stating:
“res judicata requires a party to assert all claims that the
party could have asserted in the earlier lawsuit; it follows
that if the party could not have asserted particular
claims . . . those claims could not have been asserted and
therefore are not barred by res judicata.” Id. If Senju’s
reexamined claims are not substantially the same as its
original claims—as may well be true—then they do not
encompass rights that Senju could have asserted in the
first action. In such a case, Aspex makes clear that claim
preclusion should not apply.
                            III.
    Finally, the majority’s concerns about Senju’s use of
“reexamination to obtain a second bite at the apple” are
SENJU PHARMACEUTICAL CO.   v. APOTEX INC.                 9



not well-founded. Maj. Op. at 15. Reexamination routine-
ly provides defendants with a second opportunity to
invalidate a patent’s claims. Even after a defendant fails
to invalidate a patent in district court, it can nonetheless
strip the plaintiff of any right to relief if it succeeds in
invalidating the plaintiff’s claims in reexamination before
final judgment is entered in the first case. See, e.g.,
Fresenius USA, Inc. v. Baxter Int’l, Inc., 721 F.3d 1330
(Fed. Cir. 2013). Here, as the majority concedes, the
reexamination certificate issued before final judgment
was entered in the first action before the district court.
The reexamination cancelled claims 1–3 and 8–11 of the
’045 patent and certified amended claim 6, new independ-
ent claim 12, and new dependent claims 13–16 as patent-
able. Still before final judgment was entered, Senju filed
its second action asserting the new, presumptively valid,
claims that emerged from reexamination. Thus, Senju’s
potentially new rights were both granted by the PTO and
asserted in federal court before the final judgment in the
first action. Particularly when a plaintiff is acting before
the entry of a final judgment resolving any patent
rights—a timeframe where defendants are free to use
reexamination to alter patent rights that are being adju-
dicated before a district court—there seems to be no basis
for preventing a plaintiff from making favorable use of
reexamination, as defendants often do.
                            IV.
    In sum, the majority’s analysis rests on a mischarac-
terization of the rights granted by reexamined claims,
resulting in an unprecedented expansion of the doctrine of
claim preclusion. For the reasons stated above, I dissent.
