Otsuka Pharmaceutical Co., Ltd. v. Lupin Ltd., Lupin Pharmaceuticals, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
OTSUKA PHARMACEUTICAL CO., LTD.,
Plaintiff-Appellant
v.
LUPIN LTD., LUPIN PHARMACEUTICALS, INC.,
Defendants-Appellees
______________________
2024-2297
______________________
Appeal from the United States District Court for the
District of Delaware in No. 1:21-cv-00900-RGA, Judge
Richard G. Andrews.
______________________
Decided: May 21, 2026
______________________
ZACHARY L. G ARRETT , Venable LLP, New York, NY, ar-
gued for plaintiff-appellant. Also represented by J OHN D.
MURNANE, J OSHUA ROTHMAN, ALICIA A LEXANDRA ROSE
RUSSO; MEGAN S. WOODWORTH , Venable LLP, Washington,
DC.
WILLIAM R. ZIMMERMAN, Knobbe, Martens, Olson &
Bear, LLP, Washington, DC, argued for defendants-appel-
lees. Also represented by J ARED C. B UNKER, Irvine, CA;
CAROL P ITZEL CRUZ, Bellevue, WA.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 2
______________________
Before H UGHES and C UNNINGHAM , Circuit Judges, and
BURROUGHS , District Judge.†
HUGHES , Circuit Judge.
Otsuka Pharmaceutical Co., Ltd. appeals a final judg-
ment of the United States District Court for the District of
Delaware. The district court held that certain claims of
U.S. Patent Nos. 8,273,735 and 8,501,730 were not in-
fringed by Lupin Ltd. and Lupin Pharmaceuticals, Inc.’s
manufacturing process incorporated in Abbreviated New
Drug Application No. 216063. The court also held that cer-
tain claims of U.S. Patent No. 8,273,735 were invalid for
obviousness. For the following reasons, we affirm.
I
Otsuka Pharmaceutical Co., Ltd. (Otsuka) is the owner
of U.S. Patent Nos. 8,501,730 and 8,273,735 (collectively,
patents-in-suit). Respectively, the patents-in-suit claim
highly pure tolvaptan—a compound used to treat Autoso-
mal Dominant Polycystic Kidney Disease (ADPKD)—and
improved methods for synthesizing tolvaptan. While previ-
ous synthesis methods for tolvaptan led to the production
of an impurity known as the dechlorinated impurity, the
innovation of the patents-in-suit is that, by reducing the
amount of a key hydrogenating reagent in the synthesis
process—sodium borohydride—the amount of the dechlo-
rinated impurity is reduced. Otsuka uses this innovation
in manufacturing its ADPKD treatment JYNARQUE®.
In May 2021, Lupin Ltd. notified Otsuka that it had
submitted an Abbreviated New Drug Application (ANDA)
† Honorable Allison D. Burroughs, District Judge,
United States District Court for the District of Massachu-
setts, sitting by designation.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 3
to the Food and Drug Administration, seeking approval to
market generic versions of JYNARQUE®. Otsuka then
brought an action for infringement of the ’730 patent
against Lupin Ltd. and its wholly owned subsidiary Lupin
Pharmaceuticals, Inc. (collectively, Lupin) under 35 U.S.C.
§ 271(a), (e)(2)(A), and (g). Later, Otsuka amended its com-
plaint to also assert infringement of the ’735 patent. Prior
to and at trial, the issues were narrowed to include in-
fringement and invalidity for obviousness.
Otsuka asserted claims 1, 2, 4, and 5 of the ’730 patent
and claims 7, 8, and 10 of the ’735 patent against Lupin.
The asserted claims of the ’730 patent are all independent
product-by-process claims, and they require reduction of a
benzazepine compound in the presence of a hydrogenating
agent. The claims further require that this hydrogenating
agent be present in an amount of either 0.25–1 or
0.25–0.5 molar equivalent per 1 mole of benzazepine pre-
cursor compound. For example, claim 1 of the ’730 patent
recites:
1. A highly pure 7-chloro-5-hydroxy-1-[2-me-
thyl-4-(2-methylbenzoylamino)benzoyl]-2,3,4,5
-tetrahydro-1H-1-benzazepine having a purity
of more than 99.5%, or a salt thereof, which is
produced by the process which comprises re-
ducing a benzazepine compound of the formula
(1):
wherein X1 is a halogen atom, R1 and R2 are in-
dependently a lower alkyl group, or a salt
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 4
thereof in the presence of a hydrogenating
agent selected from the group consisting of lith-
ium aluminum hydride, sodium borohydride,
zinc borohydride, and diborane in an amount of
0.25 to 1 mole per 1 mole of the compound (1).
’730 Patent, 29:9–32.
Similarly, the asserted claims of the ’735 patent are
method claims, all of which also require the reduction of a
benzazepine compound in the presence of a hydrogenating
agent in an amount of either 0.25–1 or 0.25–0.5 molar
equivalent per 1 mole of benzazepine compound. For exam-
ple, claim 7, which depends from unasserted claim 6, re-
cites (reproduced with claim 6 below for reference):
6. A process for producing a 2,3,4,5-tetrahydro-
1H-1-benzazepine compound of the formula
(10):
wherein X1 is a halogen atom, R1 and R2 are in-
dependently a lower alkyl group, or a salt
thereof, which comprises reducing a benzaze-
pine compound of the formula (1):
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 5
wherein R1, R2 and X1 are as defined above, or
a salt thereof in the presence of a hydrogenat-
ing agent selected from the group consisting of
lithium aluminum hydride, sodium borohy-
dride, zinc borohydride, and diborane in an
amount of 0.25 to 1 mole per 1 mole of the com-
pound (1).
7. The process according to claim 6, wherein
the hydrogenating agent is sodium borohydride
which is used in an amount of 0.25 to 1 mole
per 1 mole of the compound (1).
’735 Patent, 31:61–32:36.
Lupin’s ANDA submission incorporates Drug Master
File (DMF) No. 036263, which describes the process by
which Lupin intends to synthesize its generic tolvaptan
ANDA product. Lupin’s DMF indicates that its tolvaptan
synthesis process also makes use of a reduction reaction
like the one claimed by Otsuka, but where Otsuka’s
claimed process generally uses 1 molar equivalent or less of
hydrogenating agent such as sodium borohydride per
1 mole of precursor compound, Lupin’s process uses at least
1.2 molar equivalents of sodium borohydride per 1 mole of
precursor. See, e.g., J.A. 2571–73. In Lupin’s process, after
this sodium borohydride has been added, two samples are
taken, one after 15 minutes and one after 75 minutes. At
each point, the sample is tested to see if no more than
0.05% of the original amount of precursor compound re-
mains in the reaction mixture. If these tests indicate that
0.05% or less of the original amount of precursor compound
remains, then Lupin quenches the reaction by adding wa-
ter and hydrochloric acid. This destroys the chemical bonds
in the sodium borohydride, preventing any further reac-
tion. If these tests indicate that more than 0.05% of the
amount of precursor compound remains, more sodium bo-
rohydride is added.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 6
After a bench trial, the district court held that Lupin’s
DMF method for producing tolvaptan did not infringe the
asserted claims of the patents-in-suit. Separately, the dis-
trict court considered evidence of the invalidity of the pa-
tents-in-suit for obviousness over several pieces of prior
art, ultimately concluding that “Lupin has shown by clear
and convincing evidence that a POSA would have found the
claimed invention [of the ’735 patent] obvious.” Otsuka
Pharm. Co. v. Lupin Ltd., No. 21-cv-00900, 2024 WL
3618123, at *11 (D. Del. July 31, 2024) (Bench Trial Opin-
ion). The district court also found, however, that Lupin did
not demonstrate the invalidity of the asserted ’730 patent
claims under its obviousness theory.
Otsuka appeals. We have jurisdiction under 28 U.S.C.
§ 1295(a)(1).
II
On appeal, Otsuka challenges the district court’s in-
fringement conclusions, its conclusion that Lupin’s expert
at trial qualified as a skilled artisan, and its invalidity con-
clusions regarding the ’735 patent. We address each argu-
ment in turn.
A
We begin with Otsuka’s challenge to the district court’s
infringement conclusions. “Following a bench trial, we re-
view the district court’s conclusions of law de novo and its
fact-findings for clear error.” Merck Sharp & Dohme Corp.
v. Amneal Pharms. LLC, 881 F.3d 1376, 1384 (Fed. Cir.
2018). Infringement is a question of fact reviewed for clear
error after a bench trial. United Therapeutics Corp. v.
Liquidia Techs., Inc., 74 F.4th 1360, 1367 (Fed. Cir. 2023).
“A factual finding is clearly erroneous when, despite some
supporting evidence, we are left with a definite and firm
conviction that the district court was in error.” Packet Intel.
LLC v. NetScout Sys., Inc., 965 F.3d 1299, 1305 (Fed. Cir.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 7
2020) (quoting Alcon Rsch. Ltd. v. Barr Lab’ys, Inc.,
745 F.3d 1180, 1186 (Fed. Cir. 2014)).
Otsuka’s primary infringement argument on appeal is
that the district court adopted a “practical completion” con-
struction for the claim term “amount” but applied a differ-
ent and contradictory “absolute completion” construction in
determining that Lupin’s DMF process does not infringe.
Under the proper understanding of “amount,” Otsuka
claims that Lupin infringes because the reaction is practi-
cally complete before 1 molar equivalent of hydrogenating
agent is added to the reaction mixture.
During claim construction, the parties disputed how to
construe the term “amount” in the asserted claims. While
Lupin offered a construction of “amount” that would make
the relevant amount of hydrogenating agent the total
amount added into the reaction chamber, see J.A. 136,
25:1–4, the district court disagreed, finding that the claim
language itself required that the claimed amount of hydro-
genating agent be “the amount while the reaction is taking
place,” see J.A. 138–39, 27:22–28:9. Later, in post-trial
briefing, the parties presented conflicting visions of when
the reduction reaction actually takes place. While Otsuka
argued that the claim term referred to “the amount of hy-
drogenating agent added before the reduction reaction
reaches ‘practical completion’ or is ‘complete in a practical
sense,’” Bench Trial Opinion, 2024 WL 3618123, at *6
(quoting J.A. 1987), Lupin argued that “so long as unre-
acted ketone precursor and sodium borohydride are pre-
sent, the reaction will continue to proceed,” id. (quoting
J.A. 2025). The district court agreed with Otsuka, finding
that Lupin’s proposed construction was directed to the
“theoretical possibility” of “absolute completion” of the re-
action. Id. The district court therefore noted that it under-
stood “the reduction reaction to be ‘taking place’ until it
reaches some point of practical completion.” Id.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 8
Having decided that the “amount” of hydrogenating
agent was the amount present until the claimed reduction
reached “practical completion,” the district court deter-
mined that Otsuka failed to show infringement for two rea-
sons. First, the district court found that, even if Otsuka
was correct that practical completion is reached when “so
little precursor ketone remains that no further reduction is
observed,” Otsuka did not adduce evidence that showed
that the reaction was practically complete by the time the
amount of precursor compound fell to 0.05% of its original
level, the point at which Lupin decides to end the reaction
by initiating the quenching step. See id. at *7 (quoting
J.A. 1985). Second, the district court determined that, even
if Lupin’s reaction did reach practical completion at the
0.05% precursor level, Otsuka failed to demonstrate that
“no more than 1 molar equivalent of sodium borohydride or
less has been added by that point.” Id.
Assuming without deciding that practical completion is
reached when Otsuka claims it is—that is, when the
amount of precursor compound has fallen to 0.05% of its
original level—we agree with the district court that Otsuka
has failed to prove infringement of the patents-in-suit by
Lupin’s DMF process. Otsuka offers two main pieces of ev-
idence to suggest infringement of the patents-in-
suit: (1) two experiments performed by Lupin while devel-
oping its DMF process, Experiments 109 and 115, which
Otsuka contends show practical completion before 1 molar
equivalent of sodium borohydride is added; and (2) testi-
mony from its expert Dr. William Roush that the details of
Lupin’s DMF process indicate that the reduction reaction
will be complete long before the addition of 1 molar equiv-
alent of sodium borohydride. Ultimately, neither persuades
us that the district court clearly erred.
First, as the district court found, the underlying data
for Experiments 109 and 115 “contained anomalies that
might be accounted for by some unspecified ‘margin of er-
ror’ or a lack of ‘appropriate quality control.’” Id. (citations
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 9
omitted). For example, as per the testimony from Otsuka’s
expert Dr. Roush, after the full amount of hydrogenating
reagent was added in Experiment 115, the precursor mole-
cule appeared to be regenerating, despite this being impos-
sible based on the reaction’s chemistry. See J.A. 324,
88:7–16; J.A. 354–56, 118:3–120:25. While Otsuka at-
tempts to convince us that these experiments nonetheless
could form a reliable basis for Dr. Roush’s infringement
opinions, we do not find clear error in the district court’s
decision to not rely on experimental data that is, by
Dr. Roush’s own admission, flawed.
Second, Dr. Roush’s separate testimony that Lupin’s
DMF process is practically complete before the addition of
1 molar equivalent of hydrogenating agent, based on his
“vast experience performing sodium borohydride reac-
tions,” similarly fails to persuade us that the district court
clearly erred. J.A. 312, 76:15–16. Otsuka claims that
Dr. Roush’s expertise, combined with certain details about
Lupin’s DMF process, demonstrates that the DMF reaction
will proceed quickly and run to completion before even
0.5 molar equivalents of hydrogenating agent are added.
But Dr. Roush’s DMF conclusions also meaningfully rely
on data from Lupin’s Experiments 109 and 115. See, e.g.,
J.A. 1993 (characterizing Dr. Roush’s testimony as “based
on Experiments 109/115, and taking into account the dif-
ferences in process parameters between Experi-
ments 109/115 and the DMF process”). And we find no
clear error in the district court’s conclusion that these ex-
periments, on their own or in combination with Dr. Roush’s
expertise, shed little light on when the reduction reaction
in Lupin’s DMF process is practically complete. For one,
record evidence from both experts supports the district
court’s conclusion that Experiments 109 and 115 were per-
formed under different conditions than the DMF process.
See, e.g., J.A. 327, 91:23–25 (Dr. Roush); J.A. 432–33,
196:13–197:5 (Dr. Dichtel). Further, notwithstanding
Dr. Roush’s testimony that these differences should be
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 10
immaterial, see J.A. 327–34, 91:23–98:13, Dr. Dichtel tes-
tified that these differences would be material and impact
any potential infringement conclusions resulting from the
extrapolation of these experiments to the DMF process, see
J.A. 432–33, 196:13–197:24.
Considering the totality of the evidence before the dis-
trict court, we do not find clear error in its conclusion that
“Otsuka fail[ed] to prove by a preponderance of the evi-
dence that the reduction reaction in Lupin’s tolvaptan syn-
thesis process reaches completion before more than 1 molar
equivalent of sodium borohydride has been added.” Bench
Trial Opinion, 2024 WL 3618123, at *7.
B
We next turn to Otsuka’s argument that the district
court’s infringement and invalidity analyses were flawed
because Lupin’s expert Dr. Dichtel does not qualify as a
person having ordinary skill in the art. Otsuka notes that
the district court’s own definition of the skilled artisan in
this case is someone who “ha[s] a relevant doctorate degree
and ‘at least two years of experience in the synthesis, re-
search, and development of medicinal compounds.’” Appel-
lant Br. 49 (citing Bench Trial Opinion, 2024 WL 3618123,
at *3). Otsuka then argues that because Dr. Dichtel lacks
the requisite experience, his testimony should not have
been admitted.
Otsuka presented these same arguments to the district
court after trial. Ultimately, however, the district court did
not entertain the merits of Otsuka’s arguments, finding
that because Otsuka did not timely object to Dr. Dichtel’s
testimony before or during trial, it had not preserved any
challenge to the admissibility of Dr. Dichtel’s testimony.
Bench Trial Opinion, 2024 WL 3618123, at *5 (citing Fed.
R. Evid. 103(a)).
We review procedural issues not unique to patent law,
such as forfeiture, under the law of the regional circuit. See
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 11
Innogenetics, N.V. v. Abbott Lab’ys, 512 F.3d 1363, 1371
(Fed. Cir. 2008). The Third Circuit “review[s] for abuse of
discretion a district court’s determination that a party for-
feited an argument by failing to raise it earlier in the pro-
ceedings.” Harbor Bus. Compliance Corp. v. Firstbase.io,
Inc., 152 F.4th 516, 527 (3d Cir. 2025). If an argument is
found to be forfeited, it is reviewable only in “truly ‘excep-
tional circumstances.’” Id. at 529 (citation omitted).
Under the law of the Third Circuit, a party who fails to
object to errors at trial forfeits the right to complain about
those alleged errors later. United States v. Rivas, 493 F.3d
131, 136 (3d Cir. 2007). And while Otsuka is correct that it
argued Dr. Dichtel was not a skilled artisan in an elliptical
fashion in its opening statement, see, e.g., J.A. 244–45,
8:3–9:21 (“[W]e think Dr. Dichtel is straying from his ex-
pertise.”), it did not object at trial when Dr. Dichtel stated
that he felt comfortable opining on the patents-in-suit from
the perspective of a skilled artisan, see J.A. 445–46,
209:21–210:12. Nor did Otsuka file a Daubert motion seek-
ing to exclude Dr. Dichtel as an expert before trial. On
these facts, we cannot find that the district court abused
its discretion in finding that Otsuka forfeited its challenges
to Dr. Dichtel’s status as a skilled artisan. We therefore up-
hold the district court’s finding without reaching the merits
of this issue.
C
Finally, we consider Otsuka’s arguments that the dis-
trict court erred in invalidating the asserted claims of the
’735 patent for obviousness. “Obviousness is a question of
law based on underlying facts, and ‘[o]n appeal from a
bench trial, this court reviews the district court’s conclu-
sions of law de novo and findings of fact for clear error.’” Eli
Lilly & Co. v. Teva Parenteral Meds., Inc., 845 F.3d 1357,
1372 (Fed. Cir. 2017) (quoting Prometheus Lab’ys, Inc. v.
Roxane Lab’ys, Inc., 805 F.3d 1092, 1097 (Fed. Cir. 2015)).
The underlying factual determinations within the
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 12
obviousness analysis include: “(1) the scope and content of
the prior art; (2) differences between the prior art and the
claims at issue; (3) the level of ordinary skill in the perti-
nent art; and (4) secondary considerations such as commer-
cial success, long felt but unsolved needs, and failure of
others.” Incept LLC v. Palette Life Scis., Inc., 77 F.4th 1366,
1371 (Fed. Cir. 2023).
In its bench trial opinion, the district court first con-
cluded that a skilled artisan would have been motivated to
select Kondo,1 a reference which teaches a process for
small-scale synthesis of tolvaptan, as a starting point in
seeking to achieve the claimed invention. Next, the district
court found that within the Kondo process, a skilled artisan
would have been motivated to specifically select the reduc-
tion step for modification based on testimony from
Dr. Dichtel. The district court then concluded that a skilled
artisan would have been motivated to reduce the amount
of sodium borohydride used in Kondo’s reduction step be-
fore going on to find that a skilled artisan would also be
motivated to reach the claimed invention either in light of
his or her background knowledge or in light of two other
pieces of prior art. After establishing this motivation to
combine, the district court also found a reasonable expec-
tation of success in developing the invention claimed by the
asserted claims of the ’735 patent. Finally, the district
court considered various secondary considerations of non-
obviousness and concluded that these considerations did
not overcome the strong evidence in favor of obviousness.
On appeal, Otsuka primarily attacks the court’s moti-
vation analysis, arguing that Dr. Dichtel’s focus on
1 Kazumi Kondo et al., 7-Chloro-5-hydroxy-1-[2-me-
thyl-4-(2-methylbenzoylamino)benzoyl]-2,3,4,5-tetrahydro-
1H-1-benzazepine (OPC-41061): A Potent, Orally Active
Nonpeptide Arginine Vasopressin V2 Receptor Antagonist,
7 Bioorganic & Med. Chemistry 1743, 1743–54 (1999).
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 13
Kondo—and, specifically, Kondo’s reduction step—is indic-
ative of hindsight bias that should have rendered his testi-
mony not credible. Otsuka also argues that the district
court erred by dismissing its secondary consideration evi-
dence, specifically evidence of unexpectedly high tolvaptan
purity and yield over Kondo.
We are unpersuaded that the district court clearly
erred in its analysis of the skilled artisan’s motivation to
start with and modify Kondo. While Otsuka argues that
Dr. Dichtel focused solely on Kondo, reflecting hindsight
bias, Dr. Dichtel testified that he “did [his] own literature
search” and looked at several other tolvaptan-synthesis
references in addition to Kondo, but that he considered
Kondo to be a particularly promising reference. See
J.A. 544–45, 308:21–309:13. So too does Otsuka’s argu-
ment downplay evidence, credited by the district court,
that a separate, non-prior-art reference, Zard,2 referred to
Kondo as a standard method for synthesizing tolvaptan at
the time of the claimed invention. See J.A. 677–78,
441:18–442:21. While Otsuka is correct that Zard acknowl-
edged “major obstacle[s]” with Kondo’s process, see
J.A. 618–19, 382:4–383:10, considering all of the evidence,
we do not find that these considerations undermine the dis-
trict court’s conclusion that “Lupin . . . presented clear and
convincing evidence that a POSA would have recognized
Kondo as a viable starting point,” Bench Trial Opinion,
2024 WL 3618123, at *12. See In re Mouttet, 686 F.3d 1322,
1334 (Fed. Cir. 2012) (recognizing that even “inferior com-
bination[s]” of prior art may be appropriately considered in
obviousness inquiry).
Similarly, we find no clear error in the district court’s
analysis of the skilled artisan’s motivation to modify the
reduction step of Kondo specifically. As the district court
2 U.S. Patent Application Publication
No. 2007/0185323.
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 14
noted, both experts agreed that many of the steps of Kondo
would have been considered for modification, including the
reduction step. See J.A. 546–48, 310:13–312:16
(Dr. Dichtel); J.A. 665, 429:7–16 (Dr. Roush). And
Dr. Dichtel presented significant testimony about why a
skilled artisan would have sought to modify Kondo’s reduc-
tion step, including cost savings, improvement of the reac-
tion’s safety profile, post-processing simplification, and
knowledge that the hydrogenating agent was already being
used in molar excess. See, e.g., J.A. 457–63, 221:1–227:12.
This evidence, tethered to the chemical realities of the re-
action, is a far cry from the conclusory expert testimony our
case law rejects. Cf. TQ Delta LLC v. CISCO Sys., Inc.,
942 F.3d 1352, 1361–62 (Fed. Cir. 2019). We therefore de-
cline to find clear error in the district court’s choice to credit
this testimony.
Lastly, we fail to find reversible error in the district
court’s conclusions regarding secondary considerations of
non-obviousness. Otsuka purports to demonstrate both
high yield and high purity by relying in part on a declara-
tion from one of its chemists, Hirotaka Yukawa. See
J.A. 4106–16. However, in analyzing purity, the Yukawa
declaration compares the claimed methods not to Kondo it-
self, but to a process that uses double Kondo’s amount of
hydrogenating agent. Compare J.A. 449–50, 213:21–214:9
(reflecting that Kondo uses 1.5 molar equivalents of hydro-
genating agent), with J.A. 4111 (indicating that Yukawa’s
process used “3 fold molar amount of [sodium borohydride]
per 1 mole of the [precursor molecule]”). The district court
did not therefore clearly err by failing to credit the Yukawa
declaration as accurately reporting the results of Kondo’s
purity. See Bench Trial Opinion, 2024 WL 3618123, at *21.
Nor do we find clear error in the district court’s conclusion
that this difference in concentration of hydrogenating
agent was material because “Otsuka’s internal documents
report the presence of a dechlorinated impurity when using
2 molar equivalents of sodium borohydride . . . but not
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OTSUKA PHARMACEUTICAL CO., LTD. v. LUPIN LTD. 15
when using 1.5 molar equivalents as disclosed in Kondo.”
Id. at *10, *21. While Otsuka argues that this interpreta-
tion of the evidence of record rests on a misinterpretation
of Otsuka’s internal documents, we do not find clear error
in the district court’s contrary conclusion, based on testi-
mony from Dr. Dichtel that the court explicitly found “more
credible.” Id. at *21.
Regarding unexpectedly high yield, it appears that the
district court overlooked evidence from Dr. Dichtel’s testi-
mony, Kondo itself, and the Yukawa declaration reporting
that the yield of Kondo’s process using 1.5 molar equiva-
lents of hydrogenating agent was 30%, as opposed to the
claimed process’s 82–93% yield. Nonetheless, we conclude
that any error in evaluating this secondary consideration
is harmless. After all, “weak secondary considerations gen-
erally do not overcome a strong prima facie case of obvious-
ness.” Genentech, Inc. v. Sandoz Inc., 55 F.4th 1368, 1378
(Fed. Cir. 2022) (citation modified). And we have already
declined to disturb the district court’s findings underpin-
ning the prima facie case. Accordingly, any evidence intro-
duced of unexpected yield “is not sufficient to overcome the
strong case of obviousness as a matter of law.” Adapt
Pharma Operations Ltd. v. Teva Pharms. USA, Inc.,
25 F.4th 1354, 1375 (Fed. Cir. 2022). We therefore affirm
the district court’s obviousness determinations regarding
the asserted claims of the ’735 patent.
III
We have considered the parties’ remaining arguments
and find them unpersuasive. For the foregoing reasons, we
affirm the district court’s judgment of non-infringement of
the patents-in-suit, its determination that Otsuka forfeited
its skilled-artisan arguments, and its judgment that the as-
serted claims of the ’735 patent are invalid for obviousness.
AFFIRMED
Case: 24-2297 Document: 46 Page: 15 Filed: 05/21/2026

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