  United States Court of Appeals
     for the Federal Circuit
                 ______________________

            ELI LILLY AND COMPANY,
                  Plaintiff-Appellee

                                v.

                    HOSPIRA, INC., 
                  Defendant-Appellant
                 ______________________

                  2018-2126, 2018-2127
                 ______________________

   Appeals from the United States District Court for the
Southern District of Indiana in No.  1:16-cv-03460-TWP-
MPB, Judge Tanya Walton Pratt. 
            --------------------------------------------------
            ELI LILLY AND COMPANY,
                  Plaintiff-Appellee

                                v.

     DR.  REDDY'S LABORATORIES, LTD.,  DR. 
         REDDY'S LABORATORIES, INC., 
              Defendants-Appellants
             ______________________

                       2018-2128
                 ______________________
2                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




   Appeal from the United States District Court for the
Southern District of Indiana in No.  1:16-cv-00308-TWP-
MPB, Judge Tanya Walton Pratt. 
                ______________________

                 Decided: August 9, 2019
                 ______________________

    ADAM LAWRENCE PERLMAN, Williams & Connolly LLP,
Washington, DC, argued for plaintiff-appellee in 2018-2126
and 2018-2128.  Also represented by GALINA I. FOMENKOVA,
DOV PHILIP GROSSMAN, DAVID M. KRINSKY, ANDREW P.
LEMENS, CHARLES MCCLOUD; JAMES PATRICK LEEDS, Eli
Lilly and Company, Indianapolis, IN. 

    BRADFORD PETER LYERLA, Jenner & Block LLP, Chi-
cago, IL, argued for defendant-appellant in 2018-2126. 
Also represented by YUSUF ESAT, SARA TONNIES HORTON;
ADAM G. UNIKOWSKY, Washington, DC. 

    JOHN C. O'QUINN, Kirkland & Ellis LLP, Washington,
DC, argued for defendants-appellants in 2018-2128.  Also
represented by WILLIAM H. BURGESS, CALVIN ALEXANDER
SHANK; JEFFERY B. ARNOLD, Holland & Knight LLP, At-
lanta, GA; MERRI C. MOKEN, CHARLES A. WEISS, ERIC H.
YECIES, New York, NY. 

    BRIAN TIMOTHY BURGESS, Goodwin Procter LLP, Wash-
ington, DC, for amicus curiae Actavis LLC in 2018-2128. 
Also represented by EDWINA CLARKE, EMILY L. RAPALINO,
DARYL L. WIESEN, Boston, MA; LINNEA P. CIPRIANO, New
York, NY. 
                 ______________________


    Before LOURIE, MOORE, and TARANTO, Circuit Judges. 
ELI LILLY AND COMPANY v. HOSPIRA, INC.                        3



LOURIE, Circuit Judge. 
    Hospira Inc. (“Hospira”), Dr. Reddy’s Laboratories
Ltd., and Dr. Reddy’s Laboratories Inc. (collectively,
“DRL”) appeal from two judgments of the United States
District Court for the Southern District of Indiana in two
infringement suits brought by Eli Lilly & Company
(“Lilly”) under the Hatch-Waxman Act, 21 U.S.C. § 355. 
The district court held in each case that the defendant’s
submission of a New Drug Application pursuant to 21
U.S.C. § 355(b)(2) infringed U.S. Patent 7,772,209 (the
“’209 patent”) under 35 U.S.C. § 271(e)(2).  See Eli Lilly &
Co. v. Hospira, Inc., No.  1:16-cv-03460-TWP-MPB, 2018
WL 3008570 (S.D. Ind. June 15, 2018) (“Hospira Decision”);
Eli Lilly & Co. v. Dr. Reddy’s Labs.,  Ltd., 323 F. Supp.  3d
1042 (S.D. Ind. 2018) (“DRL Decision”); see also Eli Lilly &
Co. v. Dr. Reddy’s Labs.,  Ltd., No.  1:16-cv-00308-TWP-
MPB, 2017 WL 6387316 (S.D. Ind. Dec. 14, 2017) (“DRL
Summary Judgment Decision”).  Accordingly, the district
court entered orders under 35 U.S.C. § 271(e)(4)(A) prohib-
iting FDA approval of the products at issue until the expi-
ration of the ’209 patent.  Eli Lilly & Co. v. Hospira, Inc.,
No.  1:16-cv-03460-TWP-MPB (S.D. Ind. June 27, 2018),
ECF No.  94; Eli Lilly & Co. v. Dr. Reddy’s Labs.,  Ltd., No. 
1:16-cv-00308-TWP-MPB, 2018 WL 3616715 (S.D. Ind.
July 27, 2018).  We decide these appeals together in this
combined opinion.  1
     We reverse the district court’s finding of literal in-
fringement in the Hospira Decision as clearly erroneous in
light of the court’s claim construction of “administration of
pemetrexed disodium.”  Because the district court did not
err in its application of the doctrine of equivalents in either


    1   We refer to the joint appendices in these appeals by
reference to each appellant.  Lilly’s brief in the Hospira ap-
peal is referred to as “Lilly Br.  I” and its brief in the DRL
appeal as “Lilly Br.  II.” 
4                      ELI LILLY AND COMPANY v. HOSPIRA, INC. 




decision, we affirm both judgments of infringement.  Thus,
the Hospira Decision is affirmed-in-part and reversed-in-
part, and the DRL Decision is affirmed. 
                        BACKGROUND
     Lilly markets the compound pemetrexed in the form of
a disodium salt as Alimta®, which is indicated, both alone
and in combination with other active agents, for treating
certain types of non-small cell lung cancer and mesotheli-
oma.  Pemetrexed is an antifolate, a class of molecules
which, at the time of the invention in 2001, was “one of the
most thoroughly studied classes of antineoplastic agents.” 
’209 patent col.  1 ll.  19–20.  Antifolates are structurally
similar to folic acid and work by competitively binding to
certain enzymes that use folic acid metabolites as cofactors
in several steps of de novo nucleotide synthesis.  Id. col.  1
ll.  40–41.  Unlike folic acid, antifolates do not enable these
synthetic steps, but instead inhibit them.  Pemetrexed in-
hibits several of these enzymes, including thymidylate syn-
thase, which methylates deoxyuridine in the final step of
deoxythymidine synthesis.  Id. col.  1 ll.  59–61.  By inhibit-
ing the creation of these nucleotides, antifolates slow down
DNA and RNA synthesis, and with it, cell growth and divi-
sion.  Cancer cells tend to grow rapidly, so antifolate ther-
apy affects them disproportionately, but healthy cells can
also be damaged. 
    Pemetrexed had been known for at least a decade in
2001.  Lilly’s U.S. Patent 5,344,932 (“Taylor”) disclosed
that certain glutamic acid derivatives with pyrrolo[2,3-
d]pyrimidine heterocyclic ring structures, exemplified by
pemetrexed, are “particularly active . . .  inhibitors of thy-
midylate synth[ase],” Taylor col.  1 ll.  59–60; see also id. col. 
19 l. 37–col.  20 l. 25 (disclosing data indicating that
pemetrexed inhibits thymidylate synthase activity in vitro
in human cell lines and in vivo in mice).  The Taylor patent
also disclosed that its compounds could be employed as
“pharmaceutically acceptable salt[s],” id. col.  2 l. 35, and
ELI LILLY AND COMPANY v. HOSPIRA, INC.                       5



that the disodium salt form was particularly advantageous,
id. col.  2 ll.  47–48.  U.S. Patent 4,997,838 (“Akimoto”), to
which Lilly took a license, disclosed a large genus of com-
pounds containing pyrrolo[2,3-d]pyrimidine heterocyclic
ring structures and a glutamic acid functional group, and
that encompassed pemetrexed.  The Akimoto patent dis-
closes nearly fifty exemplary compounds, col.  14 l. 61–col. 
16 l. 48, none of which is pemetrexed.  Akimoto further dis-
closes that its compounds may be prepared as salts of
“pharmaceutically acceptable bases,” such as “alkali met-
als, alkali earth metals, non-toxic metals, ammonium, and
substituted ammonium.”  Id. col.  14 ll.  44–47. 
     By 2001, Lilly had also published the results of several
clinical trials investigating the use of pemetrexed disodium
as a treatment for different types of cancer.  See, e.g., W.
John et al., “ Activity of Multitargeted Antifolate
(Pemetrexed Disodium, LY231514) in Patients with Ad-
vanced Colorectal Carcinoma: Results from a Phase II
Study,” Cancer, 88(8):1807–13 (2000).  In the course of con-
ducting these studies, Lilly discovered that pemetrexed
disodium caused severe hematologic and immunologic side
effects, resulting in infections, nausea, rashes, and even
some deaths.  See id.; see also Neptune Generics, LLC v. Eli
Lilly & Co., 921 F.3d 1372, 1377–78 (Fed.  Cir.  2019) (dis-
cussing Lilly’s response to adverse clinical data), and Nep-
tune Generics, LLC v. Eli Lilly & Co., No.  IPR2016-00240,
2017 WL 4466557, at *28–30 (P.T.A.B. Oct. 5, 2017) (same). 
As the ’209 patent teaches, such side effects are not uncom-
mon among antifolates.  See ’209 patent col.  1 ll.  11–14. 
Some researchers hypothesized that folic acid deficiency
caused these side effects and suggested supplementing
pemetrexed disodium treatment with folic acid.  DRL J.A.
7870 (citing J.F. Worzalla et al., “ Role of Folic Acid in Mod-
ulating the Toxicity and Efficacy of the Multitargeted An-
tifolate, LY231514,” Anticancer Research, 18:3235–40
(1998)). 
6                      ELI LILLY AND COMPANY v. HOSPIRA, INC. 




     The invention of the ’209 patent is an improved method
of treatment with antifolates, particularly pemetrexed
disodium, through supplementation with a methylmalonic
acid lowering agent and folic acid.  Doing so, according to
the patent, lessens antifolate toxicity without sacrificing ef-
ficacy.  See ’209 patent col.  10 ll.  17–53 (reporting that pre-
supplementation regimen of vitamin B12 and folic acid in
clinical studies substantially reduced pemetrexed-induced
toxicity and deaths while delivering a superior chemother-
apeutic response rate).  The ’209 patent lists preferred an-
tifolates, including some then-existing antifolate therapies,
as well as “derivatives described in” several patents includ-
ing the Akimoto patent, and “most preferred, Pemetrexed
Disodium.”  Id. col.  4 ll.  28–43.  Each of the claims of the
’209 patent requires administration of pemetrexed diso-
dium following administration of folic acid and a
methylmalonic acid lowering agent, specified in some
claims, as well as the Alimta® label, as vitamin B12.  Claim
12 is representative2:
    12.  An improved method for administering
    pemetrexed disodium to a patient in need of chemo-
    therapeutic treatment, wherein the improvement
    comprises:
        a) administration of between about 350 µg
        and about 1000 µg of folic acid prior to the
        first administration of pemetrexed diso-
        dium;




    2  The district court treated claim 12 as representa-
tive, DRL Summary Judgment Decision, 2017 WL
6387316, at *1–2; Hospira Decision, 2018 WL 3008570, at
*2, and no party has disputed that determination on ap-
peal.  See, e.g., DRL Opening Br.  8–9; Hospira Opening Br. 
23. 
ELI LILLY AND COMPANY v. HOSPIRA, INC.                       7



        b) administration of about 500 µg to about
        1500 µg of vitamin B12, prior to the first
        administration of pemetrexed disodium;
        and
        c) administration of pemetrexed disodium. 
    In a parent application, Application 10/297,821 (the
“’821 application”), Lilly originally sought broad claims to
methods of administering an antifolate in conjunction with
a methylmalonic acid lowering agent, with or without folic
acid.  The original independent claims 2 and 5 read:
    2. ( Original) A method of reducing the toxicity as-
    sociated with the administration of an antifolate to
    a mammal comprising
        administering to said mammal an effective
        amount of said antifolate in combination
        with a methylmalonic acid lowering agent. 
    5. ( Original) A method of reducing the toxicity as-
    sociated with the administration of an antifolate to
    a mammal comprising
        administering to said mammal an effective
        amount of said antifolate in combination
        with a methylmalonic acid lowering agent
        and FBP binding agent. 
DRL J.A. 7860.  A dependent claim further limited the an-
tifolate to pemetrexed disodium.  Id. at 7861. 
    Claim 2 was rejected as anticipated by F.G. Arsenyan
et al., “ Influence of Methylcobalamin on the Antineoplastic
Activity of Methotrexate,” Onkol.  Nauchn.,  12(10):1299-
1303 (1978), which disclosed experiments treating mice
with various tumors with a combination of methotrexate,
an antifolate, and methylcobalamin, a vitamin B12 deriva-
tive.  The rest of the pending claims, including Claim 5,
were rejected as obvious over a collection of references: U.S.
Patent 5,431,925 (“Ohmori”)—which taught treatment of
8                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




chemotherapeutically-induced immunosuppression with a
combination of vitamins that could include folic acid and
vitamin B12—Worzalla, John, and Arsenyan. ’ 821 appli-
cation, Sept. 27, 2004, Office Action; DRL J.A. 7868–72. 
     In response, Lilly amended both claims to narrow “an-
tifolate” to “pemetrexed disodium” and cancelled its de-
pendent claim limited to pemetrexed disodium. ’ 821
application, Jan. 25, 2005, Response to Office Action; DRL
J.A. 7877–84.  In its remarks, Lilly asserted that the
amendment to claim 2 overcame the anticipation rejection
because Arsenyan does not disclose pemetrexed disodium. 
Id. To overcome the obviousness rejection of claim 5 and
its dependents, Lilly generally argued that, while John dis-
closes hematologic and immunologic toxicities from admin-
istration of pemetrexed disodium, it never suggests
vitamin supplementation, and none of the other references
“teach the use of [vitamin B12] to reduce toxicities associ-
ated with an antifolate.”  Id. The examiner then withdrew
the anticipation rejection and later withdrew the obvious-
ness rejection.  The ’821 application issued as U.S. Patent
7,053,065, and the ’209 patent later issued from a continu-
ation application. 
    These appeals were taken from cases which are among
the latest in a series of patent disputes about Alimta® that
reaches back more than a decade.  3 In this most recent
chapter, DRL, Hospira, and Actavis 4 submitted New Drug


    3   This is the fourth appeal we have decided concern-
ing Alimta® and the third specifically concerning the ’209
patent.  See Neptune Generics, 921 F.3d 1372; Eli Lilly &
Co. v. Teva Parenteral Meds.,  Inc., 845 F.3d 1357 (Fed.  Cir. 
2017); Eli Lilly & Co. v. Teva Parenteral Meds.,  Inc., 689
F.3d 1368 (Fed.  Cir.  2012). 
    4   Lilly also sued Actavis LLC (“Actavis”) for infringe-
ment of the ’209 patent, Eli Lilly & Co. v. Actavis LLC, No. 
1:17-cv-00982-TWP-MPB (S.D. Ind. Mar. 30, 2017), ECF
ELI LILLY AND COMPANY v. HOSPIRA, INC.                      9



Applications under § 505(b)(2) of the Federal Food, Drug,
and Cosmetic Act, 21 U.S.C. § 355(b)(2), relying on Lilly’s
clinical data for pemetrexed disodium.  But each applicant
seeks to market different pemetrexed salts—in DRL’s and
Hospira’s applications, pemetrexed ditromethamine.  Both
DRL and Hospira represented to the FDA that their choice
of the tromethamine cation was immaterial because
pemetrexed dissociates from its counterion in solution,
DRL J.A. 8555–57; Hospira J.A. 124, and tromethamine
was known to be safe for pharmaceutical use, DRL J.A.
8555, 8557. 
     Lilly then asserted the ’209 patent against each of
these NDA applicants in the United States District Court
for the Southern District of Indiana.  In the DRL case, the
district court construed the phrase “administration of
pemetrexed disodium” to mean “liquid administration of
pemetrexed disodium,” which “is accomplished by dissolv-
ing the solid compound pemetrexed disodium into solu-
tion.”  DRL Summary Judgment Decision, 2017 WL
6387316, at *4.  The district court denied DRL’s motion for
summary judgment of noninfringement, holding that pros-
ecution history estoppel does not bar Lilly from asserting
that DRL’s proposed pemetrexed ditromethamine product
would infringe through the doctrine of equivalents because
the reason for Lilly’s amendment was to distinguish other
antifolates and was therefore only tangential to
pemetrexed ditromethamine.  Id. at *6–7.  The district
court also rejected DRL’s argument that Lilly dedicated



No.  1, but the parties stipulated to be bound by the district
court’s decision in the DRL case that neither prosecution
history estoppel nor the disclosure-dedication rule bars
Lilly’s assertion of infringement through the doctrine of
equivalents.  Actavis Br.  2.  Actavis filed a brief in the DRL
appeal as amicus curiae requesting reversal of that portion
of the district court’s decision. 
10                    ELI LILLY AND COMPANY v. HOSPIRA, INC. 




pemetrexed ditromethamine to the public under the disclo-
sure-dedication rule through its reference to Akimoto’s an-
tifolate compounds because Akimoto is not incorporated by
reference into the ’209 patent and in any event discloses
pemetrexed ditromethamine only within a genus of thou-
sands of compounds, which the district court held does not
constitute the requisite disclosure of an identifiable alter-
native under this court’s precedent.  Id. at *7–8; see, e.g.,
SanDisk Corp. v. Kingston Tech.  Co., 695 F.3d 1348, 1363
(Fed.  Cir.  2012). 
     Following a bench trial, the district court’s opinion
largely followed its rationale in the DRL Summary Judg-
ment Decision with respect to the applicability of prosecu-
tion history estoppel and the disclosure-dedication rule. 
DRL Decision, 323 F. Supp.  3d at 1046–48.  In addition, the
court found that DRL’s proposed product would be admin-
istered in a manner that would meet the “administration
of pemetrexed disodium” step of the asserted claims under
the doctrine of equivalents, id. at 1049, regardless of the
“differences in chemical properties between pemetrexed
disodium and pemetrexed ditromethamine,” id. at 1050. 
     In the Hospira case, the parties similarly disputed the
doctrine of equivalents, but Lilly also asserted literal in-
fringement because Hospira’s proposed product label al-
lows reconstitution of its pemetrexed ditromethamine salt
in saline.  Hospira Decision, 2018 WL 3008570, at *2–3;
Hospira J.A. 229.  After the district court issued the DRL
Summary Judgment Decision, Hospira conceded, contin-
gent upon its right to appeal, that its product would in-
fringe under the claim construction of “administration of
pemetrexed disodium” set forth in that opinion and that its
doctrine of equivalents arguments were likewise fore-
closed.  Hospira Br.  18.  The district court, “rel[ying] heav-
ily” on the DRL Summary Judgment Decision, granted
Lilly’s motion for summary judgment of infringement, both
literally and under the doctrine of equivalents.  Hospira
Decision, 2018 WL 3008570, at *1 n.2, *6. 
ELI LILLY AND COMPANY v. HOSPIRA, INC.                       11



   These appeals followed.  We have jurisdiction under 28
U.S.C. § 1295(a)(1). 
                         DISCUSSION
     We review a district court’s grant of summary judg-
ment according to the law of the regional circuit.  Kaneka
Corp. v. Xiamen Kingdomway Grp.  Co., 790 F.3d 1298,
1303 (Fed.  Cir.  2015) (citing Halo Elecs.,  Inc. v. Pulse El-
ecs.,  Inc., 769 F.3d 1371, 1377 (Fed.  Cir.  2014)).  In the Sev-
enth Circuit, summary judgment is reviewed de novo, con-
struing all facts and drawing all inferences in favor of the
non-movant.  Wis. Alumni Research Found.  v. Apple Inc.,
905 F.3d 1341, 1352 (Fed.  Cir.  2018) (citing Austin v.
Walgreen Co., 885 F.3d 1085, 1087 (7th Cir.  2018)).  On ap-
peal from a bench trial, we review a district court’s conclu-
sions of law de novo and its findings of fact for clear error. 
Braintree Labs.,  Inc. v. Novel Labs.,  Inc., 749 F.3d 1349,
1358 (Fed.  Cir.  2014) (citing Brown & Williamson Tobacco
Corp. v. Philip Morris Inc., 229 F.3d 1120, 1123 (Fed.  Cir. 
2000)).  A factual finding is clearly erroneous if, despite
some supporting evidence, we are left with the definite and
firm conviction that a mistake has been made.  United
States v. U.S. Gypsum Co., 333 U.S. 364, 395 (1948). 
    Claim construction is ultimately an issue of law, which
we review de novo.  Shire Dev.,  LLC v. Watson Pharm.,  Inc.,
787 F.3d 1359, 1364 (Fed.  Cir.  2015).  We review de novo
the district court’s findings of fact on evidence “intrinsic to
the patent (the patent claims and specification[], along
with the patent’s prosecution history),” and review for clear
error extrinsic findings of fact.  Teva Pharm.  USA, Inc. v.
Sandoz, Inc., 135 S. Ct.  831, 841 (2015).  While infringe-
ment is a question of fact, Lucent Techs.,  Inc. v. Gateway,
Inc., 580 F.3d 1301, 1309 (Fed.  Cir.  2009), we review de
novo the district court’s grant of summary judgment of non-
infringement, Unwired Planet, LLC v. Apple Inc., 829 F.3d
1353, 1356 (Fed.  Cir.  2016).  To prove infringement, a pa-
tentee “must supply sufficient evidence to prove that the
12                    ELI LILLY AND COMPANY v. HOSPIRA, INC. 




accused product or process contains, either literally or un-
der the doctrine of equivalents, every limitation of the
properly construed claim.”  Seal-Flex, Inc. v. Athletic Track
& Court Const.,  172 F.3d 836, 842 (Fed.  Cir.  1999).  The
patentee has the burden of proving infringement by a pre-
ponderance of the evidence.  SmithKline Diagnostics, Inc.
v. Helena Labs.  Corp., 859 F.2d 878, 889 (Fed.  Cir.  1988). 
    Hospira requests reversal of the district court’s finding
that its submission of a § 505(b)(2) NDA for its pemetrexed
product literally infringed the claims of the ’209 patent. 
DRL and Hospira both argue, as does the amicus curiae
Actavis, that the district court erred as a matter of law by
refusing to apply prosecution history estoppel to bar Lilly’s
doctrine of equivalents claim, and DRL further contends
that the disclosure-dedication rule precludes Lilly’s equiv-
alents claim.  Finally, DRL disputes the district court’s
finding that administration of pemetrexed ditromethamine
is equivalent to the claim element “administration of
pemetrexed disodium.”  We address each argument in turn. 
                 A. Literal Infringement
    Hospira argues that it cannot literally infringe the
claims of the ’209 patent because intravenous administra-
tion of pemetrexed ditromethamine dissolved in saline—a
solution which contains pemetrexed and chloride anions
alongside sodium and tromethamine cations—is not “ad-
ministration of pemetrexed disodium.”  Hospira also notes
that such a solution will, in any case, contain far more than
two sodium cations per pemetrexed anion.  Finally, Hos-
pira appears to make a perfunctory argument that, in the
alternative, we should reverse the district court’s construc-
tion and hold that the term encompasses any route of ad-
ministering pemetrexed disodium, not just liquid, as the
district court’s construction requires. 
    Lilly counters that Hospira’s view improperly imposes
a “source limitation,” requiring that the pemetrexed diso-
dium salt exist in solid form before administration, even
ELI LILLY AND COMPANY v. HOSPIRA, INC.                       13



though Hospira’s proposed product label, like that of Ali-
mta®, calls for administration of a solution containing
pemetrexed anions and sodium cations.  Lilly also contends
that Hospira’s claim construction arguments are irrelevant
because Hospira’s proposed product will be administered
intravenously anyway. 
    We agree with Hospira.  It was clearly erroneous for
the district court to hold that the “administration of
pemetrexed disodium” step was met because Hospira’s
pemetrexed ditromethamine product will be dissolved in
saline before administration.  A solution of pemetrexed and
chloride anions and tromethamine and sodium cations can-
not be deemed pemetrexed disodium simply because some
assortment of the ions in the solution consists of
pemetrexed and two sodium cations.  As Lilly acknowl-
edges throughout its brief, pemetrexed disodium is a salt. 
See, e.g., Lilly Br.  I 12 (pemetrexed toxicity is caused “by
pemetrexed itself once dissociated in solution,” not
pemetrexed disodium); see also Hospira J.A. 1596 (October
2017 Alimta® Label referring to the drug substance as the
“disodium salt” of pemetrexed).  Once diluted, the salt’s
crystalline structure dissolves, and the individual ions dis-
sociate.  See Hospira J.A. 2820 (declaration of Lilly’s ex-
pert).  In other words, pemetrexed disodium no longer
exists once dissolved in solution, and, as a corollary, a dif-
ferent salt of pemetrexed dissolved in saline is not
pemetrexed disodium. 
    We conclude that to literally practice the “administra-
tion of pemetrexed disodium” step under the district court’s
claim construction, the pemetrexed disodium salt must be
itself administered.  See DRL Summary Judgment Deci-
sion, 2017 WL 6387316, at *4 (“‘[A]dministration of
pemetrexed disodium’ . . .  refer[s] to a liquid administration
of pemetrexed disodium. . . .,  accomplished by dissolving
the solid compound pemetrexed disodium into solu-
tion . . . .”);  see also Tex.  Instruments Inc. v. Cypress Semi-
conductor Corp., 90 F.3d 1558, 1563 (Fed.  Cir.  1996) (“To
14                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




literally infringe, the accused . . .  process must contain
every limitation of the asserted claim.” ( citing Laitram
Corp. v. Rexnord, Inc., 939 F.2d 1533, 1535 (Fed.  Cir. 
1991))).  There is no dispute that Hospira has only sought
approval to market pemetrexed ditromethamine, Lilly Br. 
I 4, and that neither its proposed product nor methods of
administering it will constitute administering the
pemetrexed disodium salt.  Accordingly, Hospira will not
practice the step of “administration of pemetrexed diso-
dium,” and the district court’s finding of literal infringe-
ment must be reversed. 
                B. Doctrine of Equivalents
    Few propositions of patent law have been so consist-
ently sustained by the Supreme Court as the doctrine of
equivalents.  See Festo Corp. v. Shoketsu Kinzoku Kogyo
Kabushki Co., 535 U.S. 722, 733 (2002) (“Festo VIII”)
(“[E]quivalents remain a firmly entrenched part of the set-
tled rights protected by the patent.”);  Warner-Jenkinson
Co. v. Hilton Davis Chem.  Co., 520 U.S. 17, 40 (1997) (“[W]e
adhere to the doctrine of equivalents.”);  Graver Tank &
Mfg.  Co. v. Linde Air Prods.  Co., 339 U.S. 605, 608 (1950)
(“Originating almost a century ago in the case of Winans v.
Denmead, [56 U.S. 330 (1853)] . . . [ the doctrine of equiva-
lents] has been consistently applied by this Court and the
lower federal courts, and continues today ready and avail-
able for utilization when the proper circumstances for its
application arise.”).  It is settled that a patentee is entitled
“in all cases to invoke to some extent the doctrine of equiv-
alents,” Seymour v. Osborne, 78 U.S. 516, 555 (1870), with-
out a “judicial exploration of the equities of a case”
beforehand.  See Warner-Jenkinson, 520 U.S. at 34. 
    Yet the Supreme Court has also acknowledged that the
doctrine of equivalents, “when applied broadly, conflicts
with the definitional and public-notice functions of the stat-
utory claiming requirement,” Warner-Jenkinson, 520 U.S.
at 29, and that, without the proper balance between these
ELI LILLY AND COMPANY v. HOSPIRA, INC.                         15



two imperatives, the doctrine may “take[] on a life of its
own, unbounded by the patent claims.”  See id. at 28–29. 
We have emphasized, moreover, that the doctrine of equiv-
alents is “the exception, however, not the rule,” and not
merely “the second prong of every infringement charge,
regularly available to extend protection beyond the scope
of the claims.”  London v. Carson Pirie Scott & Co., 946 F.2d
1534, 1538 (Fed.  Cir.  1991).  Patent infringement is princi-
pally determined by examining whether the accused sub-
ject matter falls within the scope of the claims. 
    To that end, courts have placed important limitations
on a patentee’s ability to assert infringement under the
doctrine of equivalents.  See, e.g., Festo VIII, 535 U.S. at
737–41 (prosecution history estoppel); Warner-Jenkinson,
520 U.S. at 39 n.8 (“[A] theory of equivalence [cannot] en-
tirely vitiate a particular claim element . . . .”);  Graver
Tank, 339 U.S. at 608 (accused equivalent cannot differ
substantially from the claimed invention); Johnson &
Johnston Assocs.  Inc. v. R.E. Serv.  Co., 285 F.3d 1046, 1054
(Fed.  Cir.  2002) (en banc) (subject matter disclosed but not
claimed is dedicated to the public) (citing Maxwell v. J.
Baker, Inc., 86 F.3d 1098 (Fed.  Cir.  1996)); Wilson Sporting
Goods Co. v. David Geoffrey & Assocs.,  904 F.2d 677, 683
(Fed.  Cir.  1990) (“[T]he asserted scope of equivalency [can-
not] encompass the prior art . . . .” ( Rich, J.) (citations omit-
ted)).  These appeals implicate several of these limitations. 
              1.  Prosecution History Estoppel
    The main dispute in these appeals is whether Lilly has
rebutted the presumption of prosecution history estoppel
that attached to its amendment in the ’821 application. 
Prosecution history estoppel arises when a patent appli-
cant narrows the scope of his claims during prosecution for
a reason “substantial[ly] relating to patentability.”  See
generally Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki
Co., 344 F.3d 1359, 1366–67 (Fed.  Cir.  2003) (en banc)
(“Festo X”).  Such a narrowing amendment is presumed to
16                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




be a surrender of all equivalents within “the territory be-
tween the original claim and the amended claim,” but the
presumption is overcome if the patentee can show the ap-
plicability of one of the few exceptions identified by the Su-
preme Court.  Festo VIII, 535 U.S. at 740–41 (citing Exhibit
Supply Co. v. Ace Patents Corp., 315 U.S. 126, 136–37
(1942)).  Whether prosecution history estoppel applies to
bar a doctrine of equivalents claim is a question of law, re-
viewed de novo.  See Regents of Univ.  of Cal.  v. Dakocyto-
mation Cal.,  Inc., 517 F.3d 1364, 1371 (Fed.  Cir.  2008)
(citing Pharmacia & Upjohn Co. v. Mylan Pharm.,  Inc., 170
F.3d 1373, 1376 (Fed.  Cir.  1999)). 
    Lilly does not dispute that the amendment in question
was both narrowing and made for a substantial reason re-
lating to patentability.  Lilly Br.  II 21.  Furthermore, Lilly
relies on only one exception to giving effect to the presump-
tion as to the scope of surrender: that the rationale of its
amendment “[bore] no more than a tangential relation to
the equivalent in question.”  Festo VIII, 535 U.S. at 740.  As
a result, the parties’ dispute about whether prosecution
history estoppel applies is confined to whether Lilly’s
amendment narrowing “an antifolate” to “pemetrexed diso-
dium” was only tangential to pemetrexed ditromethamine,
which is the accused compound.  Whether the tangential
exception applies is a question of law, Integrated Tech. 
Corp. v. Rudolph Techs.,  Inc., 734 F.3d 1352, 1356 (Fed. 
Cir.  2013), and a patentee seeking to use the exception
“must base his arguments solely upon the public record of
the patent’s prosecution.”  Festo X, 344 F.3d at 1369–70 (ci-
tation omitted). 
     The Appellants argue that Lilly failed to explain why
it did not pursue a narrower amendment literally encom-
passing pemetrexed ditromethamine, and they emphasize
our statement that the tangential exception is “very nar-
row.”  Integrated, 734 F.3d at 1358 (quoting Cross Med. 
Prods.,  Inc. v. Medtronic Sofamor Danek, Inc., 480 F.3d
1335, 1342 (Fed.  Cir.  2007)).  The Appellants further point
ELI LILLY AND COMPANY v. HOSPIRA, INC.                     17



out that Lilly cannot be said to have “lacked the words to
describe” pemetrexed ditromethamine, see Festo VIII, 535
U.S. at 734, because Lilly’s previous patents, as well as the
European companion to the ’209 patent, claimed
pemetrexed salts generally and pemetrexed disodium in a
dependent claim.  They also assert that the district court
erred by focusing on whether Lilly actually needed to relin-
quish pemetrexed ditromethamine to overcome the Arsen-
yan anticipation rejection because “the tangential
exception is not a patentee’s-buyer’s-remorse exception.” 
DRL Br.  39. 
    In response, Lilly argues that the district court
properly held that the reason for its amendment was to dis-
tinguish pemetrexed from antifolates generally and that
the different salt type is a merely tangential change with
no consequence for pemetrexed’s administration or mecha-
nism of action within the body.  Lilly also contends that it
is not barred from asserting the tangential exception
simply because pemetrexed ditromethamine is within “the
territory between the original claim and the amended
claim.”  Festo VIII, 535 U.S. at 740.  Finally, Lilly argues
that Appellants’ view that courts must “consider hypothet-
ical alternative amendments” that would literally encom-
pass the alleged equivalent “would eviscerate the
tangentiality exception.”  Lilly Br.  II 44. 
    We agree with Lilly.  As a general matter, we find Ap-
pellants’ view of prosecution history estoppel, and the tan-
gential exception in particular, too rigid.  Tangential
means “touching lightly or in the most tenuous way.”  Web-
ster’s Third New International Dictionary (2002).  The rea-
son for Lilly’s amendment, as the district court concluded,
was to narrow original claim 2 to avoid Arsenyan, which
only discloses treatments using methotrexate, a different
antifolate.  See DRL J.A. 7879–80 (overcoming the Arsen-
yan anticipation rejection by arguing that it “does not dis-
close pemetrexed disodium”).         To overcome a clear
anticipation, Lilly opted to narrow its original claim 2 and
18                    ELI LILLY AND COMPANY v. HOSPIRA, INC. 




its dependents to more accurately define what it actually
invented, an improved method of administering
pemetrexed.  In other words, the particular type of salt to
which pemetrexed is complexed relates only tenuously to
the reason for the narrowing amendment, which was to
avoid Arsenyan.  We therefore hold that Lilly’s amendment
was merely tangential to pemetrexed ditromethamine be-
cause the prosecution history, in view of the ’209 patent it-
self, strongly indicates that the reason for the amendment
was not to cede other, functionally identical, pemetrexed
salts. 
     The prosecution record confirms our understanding. 
Original claim 5, which, like all the current claims of the
’209 patent, required supplementation with both vitamin
B12 and folic acid, was never rejected as anticipated over
Arsenyan.  Instead, the art cited against original claim 5
and its dependent claims in the obviousness ground of re-
jection was replete with information about pemetrexed
disodium; John disclosed clinical trials using pemetrexed
disodium, reporting both its efficacy and its toxic side ef-
fects, and in response, DRL J.A. 7869–70, Worzalla sug-
gested folic acid supplementation to counteract these side
effects, DRL J.A. 7870–71.  The prosecution record implies
that Lilly’s amendment, inartful though it might have
been, was prudential in nature and did not need or intend
to cede other pemetrexed salts. 
    Hospira argues that the amendment was made to over-
come the obviousness rejection over Ohmori and John and
that Lilly has provided no reason for the amendment rela-
tive to that rejection.  Like Lilly, we find this argument
makes little sense.  John discloses the results of a clinical
trial of pemetrexed disodium and explicitly suggests the
toxicities caused by pemetrexed; as we concluded above,
narrowing “antifolate” to “pemetrexed disodium” could not
possibly distinguish the art cited in the obviousness ground
of rejection. 
ELI LILLY AND COMPANY v. HOSPIRA, INC.                        19



      DRL also insists that we have held that an applicant’s
remorse at ceding more claim scope than necessary is not a
reason for the tangential exception to apply.  See, e.g., Lu-
cent Techs.,  Inc. v. Gateway, Inc., 525 F.3d 1200, 1218 (Fed. 
Cir.  2008); Schwarz Pharma, Inc. v. Paddock Labs.,  Inc.,
504 F.3d 1371, 1377 (Fed.  Cir.  2007).  This is generally
true, but DRL overreads the holdings of these cases.  After
all, the tangential exception only exists because applicants
over-narrow their claims during prosecution.  Amend-
ments are not construed to cede only that which is neces-
sary to overcome the prior art, see Schwarz, 504 F.3d at
1377, nor will the court “speculat[e]” whether an amend-
ment was necessary, see Kinzenbaw v. Deere & Co., 741
F.2d 383, 389 (Fed.  Cir.  1984).  But the reason for an
amendment, where the tangential exception is invoked,
cannot be determined without reference to the context in
which it was made, including the prior art that might have
given rise to the amendment in the first place.  See Festo X,
344 F.3d at 1370.  Here, it is unlikely that a competitor
would have been “justified in assuming that if he [made an
equivalent pemetrexed salt], he would not infringe [the
’209 patent].”  Kinzenbaw, 741 F.2d at 389; cf.  Festo VIII,
535 U.S. at 738 (“There is no reason why a narrowing
amendment should be deemed to relinquish equivalents
. . .  beyond a fair interpretation of what was surrendered.”). 
    Furthermore, Appellants’ suggestion that Lilly must
prove that it could not have drafted a claim that literally
encompassed pemetrexed ditromethamine is unsupported
by our precedent on prosecution history estoppel, not to
mention excessive.  We do not demand perfection from pa-
tent prosecutors, and neither does the Supreme Court.  See
Festo VIII, 535 U.S. at 738 (“It does not follow . . .  that [an]
amended claim becomes so perfect in its description that
no one could devise an equivalent.”).  Lilly’s burden was to
show that pemetrexed ditromethamine was “peripheral, or
not directly relevant,” to its amendment, Festo X, 344 F.3d
at 1369.  And as we concluded above, Lilly has done so. 
20                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




    In addition, the Appellants maintain that when a pa-
tentee submits an amendment adding two claim limita-
tions, it cannot later argue that the reason for the
amendment was tangential to an accused equivalent con-
taining only one of the added limitations simply because
the second limitation was unnecessary to overcome the
prior art.  They offer Felix v. American Honda Motor Co.,
562 F.3d 1167 (Fed.  Cir.  2009), as an illustration of this
principle.  5 In that case, we held that prosecution history
estoppel applied to a claim directed to a vehicle bed storage
system—limited in response to a rejection to having a
channel with a flange and a gasket mounted on that
flange—barring assertion of equivalence with respect to a
product that met the channel aspect, but not the gasket as-
pect, of the limitation.  Id. at 1184–85. 
    But as Lilly points out, this holding was determined by
that patent’s prosecution history, Felix, 562 F.3d at 1184,
and we have also held that prosecution history estoppel
does not apply in similar circumstances, where the



     5    The parties argue at length about which of our
cases are properly analogous to the facts presented in these
appeals.  Here, in applying the Supreme Court’s frame-
work, we find the analogies to other cases less helpful than
a direct consideration of the specific record of this case and
what it shows about the reason for amendment and the re-
lation of that reason to the asserted equivalent.  This case-
specific focus, within the governing framework, comports
with the equitable nature of prosecution history estoppel. 
See Festo VIII, 535 U.S. at 738 (“[The Supreme Court has]
consistently applied the doctrine in a flexible way, not a
rigid one.”);  cf.  Heckler v. Cmty.  Health Servs.  of Crawford
Cty.,  Inc., 467 U.S. 51, 59 (1984) (“Estoppel is an equitable
doctrine invoked to avoid injustice in particular cases. . . . 
[and] a hallmark of the doctrine is its flexible applica-
tion . . . .”). 
ELI LILLY AND COMPANY v. HOSPIRA, INC.                     21



prosecution record differed.  See, e.g., Regents, 517 F.3d at
1376–78 (amendment narrowing “disabling hybridization
capacity of [nucleic acid] sequences” to methods using a
“blocking nucleic acid” was merely tangential to unclaimed
repetitive sequence nucleic acids); Insituform Techs.,  Inc.
v. CAT Contracting, Inc., 385 F.3d 1360, 1368 (Fed.  Cir. 
2004) (amendment narrowing method of inserting resin
into tube using a vacuum to one using “a cup” to do so was
merely tangential to a multiple cup embodiment because
the number of cups bore no relationship to the cited prior
art or the rationale behind the narrowing amendment). 
Thus, our cases demonstrate that prosecution history es-
toppel is resistant to the rigid legal formulae that Appel-
lants seek to extract from them.  See Intervet Inc. v. Merial
Ltd., 617 F.3d 1282, 1291 (Fed.  Cir.  2010) (“[T]here is no
hard-and-fast test for what is and what is not a tangential
relation . . . .”). 
    Finally, DRL also contends that our precedent squarely
forecloses Lilly’s tangentiality argument, and it invites us
to read those cases to hold that “where the reason for the
amendment and the equivalent in question both relate to
the same claim element, the tangential exception does not
apply.”  DRL Br.  47.  We decline this invitation because
such a bright-line rule is both contrary to the equitable na-
ture of prosecution history estoppel, as articulated in Festo
VIII, 535 U.S. at 738, and inconsistent with the equitable
spirit that animates the doctrine of equivalents, see Graver
Tank, 339 U.S. at 608–09 (the doctrine is one of “whole-
some realism”).  Instead, we reaffirm that whether an
amendment was merely tangential to an equivalent must
be decided in the context of the invention disclosed in the
patent and the prosecution history.  Festo X, 344 F.3d at
1370. 
    DRL’s intuition—that an amendment that narrows an
existing claim element evinces an intention to relinquish
that claim scope—is often correct.  Indeed, as we have
found in previous cases, it is a powerful indication that an
22                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




amendment was not merely tangential.  See, e.g., Honey-
well Int’l, Inc. v. Hamilton Sundstrand Corp., 523 F.3d
1304, 1315–16 (Fed.  Cir.  2008); Biagro W. Sales, Inc. v.
Grow More, Inc., 423 F.3d 1296, 1306 (Fed.  Cir.  2005).  But
here, we conclude that this consideration is not dispositive
because the rest of the prosecution history, and the ’209
patent itself, show that it is implausible that the reason for
Lilly’s amendment was to surrender other pemetrexed
salts.  Indeed, such a relinquishment would effectively ded-
icate the entirety of Lilly’s invention to the public and
thereby render the ’209 patent worthless, and it would
have been irrelevant for distinguishing the prior art. 
Again, the prosecution history strongly indicates a less
sweeping and more sensible reason for Lilly’s amendment:
to surrender antifolates other than pemetrexed.  Thus, we
conclude on this prosecution record that Lilly’s amendment
was merely tangential to pemetrexed ditromethamine. 
              2.  Disclosure-Dedication Rule
    DRL next argues that the disclosure-dedication rule
bars Lilly from asserting infringement under the doctrine
of equivalents.  The ’209 patent sets forth its invention as
an improved method of administering antifolates, ’209 pa-
tent col.  2 ll.  47–58, and teaches that the derivatives de-
scribed in the Akimoto patent are preferred examples of
antifolates, id. col.  4 ll.  34–40.  DRL contends that one of
these derivatives is pemetrexed ditromethamine and that
it was dedicated to the public when Lilly declined to claim
it.  DRL asserts that the district court erred because it both
required express incorporation of Akimoto by reference
into the ’209 patent and concluded that Akimoto does not
specifically disclose pemetrexed ditromethamine. 
    Lilly counters that the disclosure-dedication rule re-
quires express disclosure of the subject matter in question
in the specification except in narrow circumstances, such
as when that subject matter is disclosed in a priority appli-
cation, see Abbott Labs.  v. Sandoz, Inc., 566 F.3d 1282,
ELI LILLY AND COMPANY v. HOSPIRA, INC.                      23



1297 (Fed.  Cir.  2009), or prior art expressly incorporated
by reference, SanDisk, 695 F.3d at 1366.  Lilly also argues
that the district court correctly determined that the rele-
vant portion of Akimoto discloses only a generic formula
from which a skilled artisan would not be able to recognize
pemetrexed ditromethamine. 
    We agree with Lilly and hold that the disclosure-dedi-
cation rule is inapplicable to this case because the ’209 pa-
tent does not disclose methods of treatment using
pemetrexed ditromethamine, and, as a result, Lilly could
not have dedicated such a method to the public. 
    Under the disclosure-dedication rule, subject matter
disclosed by a patentee, but not claimed, is considered ded-
icated to the public.  See Johnson & Johnston, 285 F.3d at
1054.  The reason for the doctrine is that members of the
public reading a disclosure of particular subject matter are
entitled, absent a claim to it, to assume that it is not pa-
tented and therefore dedicated to the public (unless, for ex-
ample, claimed in a continuation or other application based
on the disclosure).  Cf.  Maxwell, 86 F.3d at 1107 (failure to
claim inventive subject matter “is clearly contrary to 35
U.S.C. § 112, which requires that a patent applicant ‘par-
ticularly point[] out and distinctly claim[] the subject mat-
ter which the applicant regards as his invention’”).  Subject
matter is considered disclosed when a skilled artisan “can
understand the unclaimed disclosed teaching upon reading
the written description,” but not “any generic reference . . . 
necessarily dedicates all members of that particular ge-
nus.”  PSC Comput.  Prod.,  Inc. v. Foxconn Int’l, Inc., 355
F.3d 1353, 1360 (Fed.  Cir.  2004). 
    DRL further contends that the disclosure-dedication
rule does not impose a § 112 requirement for sufficiency of
disclosure, see Toro Co. v. White Consol.  Indus.,  Inc., 383
F.3d 1326, 1334 (Fed.  Cir.  2004), and that a skilled artisan
reading the ’209 patent would both look for a disclosure of
pemetrexed in Akimoto, and also seek to use a well-known
24                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




cation like tromethamine, which it maintains is generically
disclosed in Akimoto in the form of “substituted ammo-
nium” base salts. 
     We are unpersuaded by DRL’s arguments.  As the dis-
trict court noted, Akimoto’s formula, col.  1 l. 49–col.  2 l. 3,
includes seven functional group variables and encompasses
thousands of compounds, and while Akimoto discloses
about fifty exemplary compounds, none of them is
pemetrexed.  Moreover, Akimoto does not even disclose tro-
methamine expressly but only generically among dozens of
other salts.  At most, Akimoto discloses ammonium salts
generally, which is far from a description of tromethamine. 
In similar circumstances, we have held that “sufficient de-
scription of a genus” requires that a skilled artisan be able
to “‘visualize or recognize’ the members of the genus.”  See
Ariad Pharm.,  Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1350
(Fed.  Cir.  2010) (quoting Regents of the Univ.  of Cal.  v. Eli
Lilly & Co., 119 F.3d 1559, 1568–69 (Fed.  Cir.  1997)). 
Akimoto does not so describe pemetrexed ditromethamine,
and we see no reason why a skilled artisan would set out
on DRL’s winding path to cobble together pemetrexed dit-
romethamine.         While the ’209 patent teaches that
pemetrexed disodium is the “most preferred” antifolate,
that knowledge would not change the skilled artisan’s un-
derstanding of what Akimoto discloses. 
   Because Akimoto contains only a “generic reference” to
pemetrexed ditromethamine, PSC Comput.,  355 F.3d at
1360, we conclude that it was not dedicated to the public. 
                          3.  Merits
    A component in an accused product or process may be
equivalent to a claim element if the two are insubstantially
different with respect to the “role played by [the] element
in the context of the specific patent claim.”  Warner-Jen-
kinson, 520 U.S. at 39–40.  Relevant differences can in-
clude the function each serves, the way in which each
works, and the result each obtains, id. at 39, and, especially
ELI LILLY AND COMPANY v. HOSPIRA, INC.                      25



in biochemical cases, structural or pharmacological charac-
teristics, Mylan Inst.  LLC v. Aurobindo Pharm.  Ltd., 857
F.3d 858, 869 (Fed.  Cir.  2017). “ The determination of
equivalency vel non is a question of fact,” Canton Bio Med., 
Inc. v. Integrated Liner Techs.,  Inc., 216 F.3d 1367, 1369
(Fed.  Cir.  2000) (citing Pall Corp. v. Micron Separations,
Inc., 66 F.3d 1211, 1218 (Fed.  Cir.  1995)), which we review
for clear error in an appeal from a bench trial, Pfizer, Inc.
v. Apotex, Inc., 480 F.3d 1348, 1359 (Fed.  Cir.  2007). 
    DRL argues that the district court erred in finding that
its proposed pemetrexed ditromethamine product will be
administered in an insubstantially different way from the
claimed method.  DRL maintains that the district court fo-
cused on the fact that each product treats the same dis-
eases by delivering pemetrexed intravenously, when the
relevant context is the manner of administration.  In DRL’s
view, the chemical differences between sodium and tro-
methamine—e.g., pH, buffering capacity, or solubility—
DRL Br.  20–21, render the methods in which each is ad-
ministered to a patient substantially different. 
    Lilly responds that the relevant context is treatment of
a patient “in need of chemotherapeutic treatment.” ’ 209
patent claim 12.  Lilly agrees with the district court that
the chemical differences between sodium and trometham-
ine are clinically irrelevant because each undisputedly
lacks therapeutic activity. 
    We see no clear error in the district court’s findings.  As
the district court found, DRL’s product will accomplish an
identical aim, furnishing the same amount of pemetrexed
to active sites in the body; in exactly the same way, by di-
luting a pemetrexed salt in an aqueous solution for intra-
venous administration.          Indeed, after dilution and
immediately before administration, DRL’s product is func-
tionally identical to Lilly’s in that it contains the same
amount of diluted pemetrexed anion.  DRL J.A. 8557.  And
DRL declines to identify the relevance of any of the
26                     ELI LILLY AND COMPANY v. HOSPIRA, INC. 




chemical differences it identifies.  See UCB, Inc. v. Watson
Labs.  Inc., 927 F.3d 1272, 1284–86 (Fed.  Cir.  2019) (chem-
ical differences may not be relevant if the equivalent has
known interchangeability in the context of the claimed
composition).  We find DRL’s arguments unconvincing and
therefore affirm the district court’s findings. 
    In summary, these cases are eminently suitable for ap-
plication of the doctrine of equivalents, and we conclude
that neither prosecution history estoppel nor the disclo-
sure-dedication rule bars Lilly from asserting infringement
through equivalence. 
                        CONCLUSION
    We have fully considered each party’s further argu-
ments but find them unpersuasive.  For the foregoing rea-
sons, we reverse the district court’s finding of literal
infringement in the Hospira Decision but affirm its judg-
ment of infringement under the doctrine of equivalents. 
The judgment of infringement under the doctrine of equiv-
alents in the DRL Decision is likewise affirmed. 
AFFIRMED-IN-PART AND REVERSED-IN-PART IN
      APPEAL NOS.  2018-2126, 2018-2127
        AFFIRMED IN APPEAL NO.  2018-2128
                           COSTS
     Each party shall bear its own costs.