   United States Court of Appeals
       for the Federal Circuit
                    __________________________

   IN RE CYCLOBENZAPRINE HYDROCHLORIDE
       EXTENDED-RELEASE CAPSULE PATENT
                              LITIGATION
---------------------------------------------------------------------------------
                      ------------------------------------
       EURAND, INC. (NOW KNOWN AS APTALIS
    PHARMATECH, INC.), CEPHALON, INC., AND
                              ANESTA AG,
                     Plaintiffs-Cross Appellants,
                                       v.
  MYLAN PHARMACEUTICALS INC. AND MYLAN
                   INC.,
            Defendants-Appellants,
                                     and
               PAR PHARMACEUTICAL, INC.,
                    Defendant-Appellee.
                    __________________________

                         2011-1399, -1409
                    __________________________

    Appeals from the United States District Court for the
District of Delaware in Case No. 09-MD-2118, Judge Sue
L. Robinson.
                 _____________________

                       Decided: April 16, 2012
                        _____________________
EURAND   v. MYLAN                                           2


    JONATHAN E. SINGER Fish & Richardson, P.C., of Wil-
mington, Delaware, argued for plaintiff-cross appellant.
With him on the brief were WILLIAM J. MARSDEN, JR. of
Minneapolis, Minnesota, JUANITA R. BROOKS, of San
Diego, California, and CHERYLYN ESOY MIZZO, of Wash-
ington, DC.

    JAMES H. WALLACE, JR., Wiley Rein LLP, of Washing-
ton, DC, argued defendants-appellants. With him on the
brief were MARK A. PACELLA, ROBERT J. SCHEFFEL,
MATTHEW J. DOWD, KEVIN P. ANDERSON and BRIAN H.
PANDYA.
              __________________________

 Before NEWMAN, O’MALLEY, and REYNA, Circuit Judges.
O’MALLEY, Circuit Judge.
     After a bench trial, the U.S. District Court for the Dis-
trict of Delaware found U.S. Patent Nos. 7,387,793 and
7,544,372 invalid as obvious. Case No. 2011-1409 is an
appeal from that judgment. We reverse and vacate the
district court’s judgment of invalidity because the district
court erred when it declared the patents in suit invalid as
obvious. Specifically, by failing to consider the lack of a
known pharmacokinetic/pharmacodynamic relationship
for the claimed drug formulation, the trial court erred
when it assessed the importance of the teachings of the
prior art to the obviousness analysis.
    As an alternative ground in support of the district
court’s judgment invalidating the ’793 and ’372 patents,
the defendants argue that the district court erred when it
found that the patents satisfy the best mode disclosure
requirement. We affirm the district court’s best mode
ruling. The evidence supports a finding that the patents
3                                         EURAND   v. MYLAN


in suit enable one of ordinary skill in the art to practice
the inventor’s preferred dew points.
    After invalidating the ’793 and ’372 patents as obvi-
ous, the district court enjoined the defendants—the
parties who prevailed at trial—from launching their
generic product pending appeal to this court. That order
is challenged in Case No. 2011-1399. We dismiss that
appeal as premature because several outstanding issues
in the district court leave uncertain whether the defen-
dants could recover on their appeal bond.
                            I.
    Plaintiff Aptalis Pharmatech, Inc. is the owner of the
’793 and ’372 patents. Plaintiff Anesta AG, a wholly
owned subsidiary of plaintiff Cephalon, Inc., is the exclu-
sive licensee of the patents. We refer to the plaintiffs
collectively as Cephalon.
    The ’793 patent covers a modified-release dosage form
of skeletal muscle relaxants. The ’372 patent covers a
method of relieving muscle spasms with the formulation
disclosed in the ’793 patent. Cephalon markets a drug
covered by the patents under the brand name Amrix. The
active pharmaceutical ingredient in Amrix is cycloben-
zaprine hydrochloride. A single dose of Amrix releases
cyclobenzaprine hydrochloride in the body during a
twenty-four-hour period.       Immediate-release formula-
tions, by contrast, release the drug in a shorter amount of
time and require multiple daily doses.
    The ’793 and ’372 patents share the same specifica-
tion and, as relevant to this appeal, have the same limita-
tions in claims 1–3. Claim 1 recites a dosage form of a
skeletal muscle relaxant (in the ’793 patent) and a
method of relieving muscle spasms (in the ’372 patent),
which, in relevant part, “provides [a] therapeutically
EURAND   v. MYLAN                                           4


effective plasma concentration over a period of 24 hours to
treat muscle spasm associated with painful musculoskele-
tal conditions . . . .” ’793 patent col.10 ll.23, 43–46 (filed
Nov. 14, 2003); ’372 patent col.10 ll.21, 43–46 (filed Feb. 6,
2008). Claim 2 depends on claim 1 and specifies the
claimed skeletal muscle relaxant as cyclobenzaprine
hydrochloride. ’793 patent col.10 ll.62–64; ’372 patent
col.10 ll.61–62. Claim 3 depends on claim 2 and specifies
the following pharmacokinetic values:
         [A] maximum blood plasma concentration
         (Cmax) within the range of about 80% to
         125% of about 20 ng/mL of cycloben-
         zaprine HCl and an AUC0–168 within the
         range of about 80% to 125% of about 740
         ng·hr/mL and a Tmax within the range of
         80% to 125% of about 7 hours following
         oral administration . . . .
’793 patent col.10 l.65–col.11 l.5; ’372 patent col.10 l.63–
col.11 l.3.
    Pharmacokinetics is the study of what a person’s body
does to a drug after administration. The pharmacokinetic
(“PK”) values recited in claim 3 measure various charac-
teristics about the drug’s behavior in a patient’s blood
plasma. Cmax, as claim 3 alludes, represents the maxi-
mum concentration of the drug in a person’s blood
plasma. AUC0–168 represents the area under the blood
plasma concentration curve, or, in other words, the body’s
total exposure to the drug. Tmax represents the time after
administration when the maximum concentration of the
drug in the blood plasma (Cmax) occurs.
    To formulate a therapeutically effective, extended-
release version of cyclobenzaprine hydrochloride, the
inventors had to ascertain the correct pharmacoki-
netic/pharmacodynamic (“PK/PD”) profile. The PK side of
5                                         EURAND   v. MYLAN


the relationship—what a person’s body does to the drug—
includes the Cmax, AUC, and Tmax, as identified in claim 3.
The PD side of the relationship describes the effect that a
drug renders on a person’s body. The PD of cycloben-
zaprine hydrochloride is the relief of muscle spasms.
    The determination of a PK profile is a quantitative
exercise. The determination of PD, or therapeutic effec-
tiveness, however, is a qualitative exercise. As one of
Cephalon’s experts, Dr. Stanley Davis, explained, a
therapeutically effective plasma concentration is “a con-
centration that the formulation provides when the formu-
lation works.” The district court, likewise, construed the
claim limitation “therapeutically effective plasma concen-
tration” to mean “the amount of a drug required to pro-
duce the therapeutic result.”
    One of the patents’ inventors, Dr. Gopi Venkatesh,
testified at trial about how he and his co-inventor, Dr.
James Clevenger, ascertained the correct PK/PD profile
for the patented formulation. First, they estimated PK
values with computer models. They started by creating
PK profiles for the immediate-release formulation. The
immediate-release formulation is dosed at 10 mg. Using
immediate-release PK data, the inventors created models
for twice-a-day dosing and three-times-a-day dosing at 10
mg per dose. Then, they drew on that data to create a
model for a single, 30 mg dose. The inventors then cre-
ated an in vitro dissolution profile, which modeled how
much drug would be released over time if the formulation
with the model PK values were placed in a solution such
as water. Finally, the inventors tested a formulation with
the model PK values and dissolution profile in a clinic.
Clinical test results confirmed that the formulation was
therapeutically effective.
EURAND   v. MYLAN                                         6


                            II.
     The defendants, Mylan Pharmaceuticals Inc. and My-
lan Inc. (collectively, “Mylan”), and Par Pharmaceutical,
Inc. (“Par”), filed abbreviated new drug applications
(“ANDAs”) for generic versions of extended-release
cyclobenzaprine hydrochloride. In support of their AN-
DAs, Mylan and Par filed “Paragraph IV” certifications, in
which they alleged that their generic products would not
infringe the ’793 patent, or that the patent was invalid or
unenforceable. See 21 U.S.C. § 355(j)(2)(A)(vii)(IV) (2006).
The U.S. Food and Drug Administration (“FDA”) ap-
proved both defendants’ applications. Because Mylan was
the first party to file a Paragraph IV certification, the
FDA granted Mylan a 180-day exclusive marketing period
for its generic product.
    Cephalon sued Mylan and Par for patent infringe-
ment, claiming that the defendants’ filing of their ANDAs
infringed the ’793 patent. See 35 U.S.C. § 271(e)(2) (2006
& Supp. IV 2010). The FDA stayed Mylan’s exclusive
marketing period for thirty months because of the litiga-
tion. The district court conducted a bench trial in Sep-
tember and October 2010. Rather than ruling from the
bench, the district court took the matter under advise-
ment to prepare a written opinion. The end of the FDA’s
thirty-month stay approached as the parties waited for
the district court’s opinion. On April 8, 2011, the district
court, sua sponte, temporarily enjoined Mylan from
launching its generic product pending the issuance of an
opinion. The thirty-month stay expired on April 17, 2011.
    The district court issued its written opinion on May
12, 2011. It ruled that Mylan’s and Par’s products in-
fringed the ’793 and ’372 patents, but that Cephalon’s
asserted patent claims were invalid as obvious. The
district court entered judgment of invalidity in favor of
7                                         EURAND   v. MYLAN


Mylan and Par. The district court’s sua sponte injunction
expired by its own terms upon entry of judgment.
    On May 13, 2011, the day after the district court en-
tered judgment, Mylan launched its generic product. On
May 15, 2011, Cephalon moved for an injunction to bar
Mylan’s launch pending appeal and to recapture product
already released. Cephalon argued that it was likely to
prevail on appeal because it believed the district court
had made a number of errors in its obviousness analysis.
In response, the district court conceded certain errors and
modified some of its findings, but reaffirmed its obvious-
ness ruling. Notwithstanding that it affirmed Mylan’s
victory, the district court granted Cephalon’s motion for
injunctive relief and issued an injunction pending appeal
to this court. The district court expressed uncertainty
about whether this court would affirm its invalidity ruling
and found that Cephalon was “just as likely as not” to
succeed on appeal. The district court then found that the
potential harm to Cephalon and a lack of a corresponding
threat of harm to Mylan weighed in favor of an injunction.
    Mylan appealed the injunction. Cephalon appealed
the district court’s invalidity ruling. Mylan moved this
court to stay the injunction pending resolution of the
appeal, and this court did so temporarily, pending full
briefing of Mylan’s motion. In re Cyclobenzaprine Hydro-
chloride Extended-Release Capsule Patent Litig., No.
2011-1399 (Fed. Cir. May 25, 2011) (order granting im-
mediate stay of preliminary injunction). After briefing
from the parties, this court lifted the temporary stay, but
declined to require that Mylan recall any product it had
sold while the stay was in place. In re Cyclobenzaprine
Hydrochloride Extended-Release Capsule Patent Litig.,
Nos. 2011-1399, 2011-1409 (Fed. Cir. July 7, 2011) (order
granting temporary stay in part). We now consider both
appeals on their merits.
EURAND   v. MYLAN                                          8


                            III.
     We address the district court’s obviousness ruling
first. A patent may not issue “if the differences between
the subject matter sought to be patented and the prior art
are such that the subject matter as a whole would have
been obvious at the time the invention was made to a
person having ordinary skill in the art to which said
subject matter pertains.” 35 U.S.C. § 103(a) (2006).
Obviousness is a question of law based on underlying
factual findings: (1) the scope and content of the prior art;
(2) the differences between the claims and the prior art;
(3) the level of ordinary skill in the art; and (4) objective
considerations of nonobviousness. Graham v. John Deere
Co., 383 U.S. 1, 17–18 (1966). Generally, a party seeking
to invalidate a patent as obvious must “demonstrate ‘by
clear and convincing evidence that a skilled artisan would
have had reason to combine the teaching of the prior art
references to achieve the claimed invention, and that the
skilled artisan would have had a reasonable expectation
of success from doing so.’” Procter & Gamble Co. v. Teva
Pharms. USA, Inc., 566 F.3d 989, 994 (Fed. Cir. 2009)
(quoting Pfizer, Inc. v. Apotex, Inc., 480 F.3d 1348, 1361
(Fed. Cir. 2007)). See also Amgen, Inc. v. F. Hoffmann-La
Roche Ltd., 580 F.3d 1340, 1362 (Fed. Cir. 2009) (“An
obviousness determination requires that a skilled artisan
would have perceived a reasonable expectation of success
in making the invention in light of the prior art.”) (cita-
tions omitted). The Supreme Court has warned, however,
that, while an analysis of any teaching, suggestion, or
motivation to combine known elements is useful to an
obviousness analysis, the overall obviousness inquiry
must be expansive and flexible. KSR Int’l Co. v. Teleflex,
Inc., 550 U.S. 398, 415, 419 (2007).
    In reviewing a district court’s obviousness ruling after
a bench trial, we review its legal conclusion de novo, but
9                                          EURAND   v. MYLAN


we review its underlying factual findings for clear error.
Proctor & Gamble, 566 F.3d at 993–94. The clear-error
standard of review applied to a district court’s factual
findings demands that we defer to those findings unless
we are left with “a definite and firm conviction that a
mistake has been committed.” United States v. U.S.
Gypsum Co., 333 U.S. 364, 395 (1948). While we afford
deference to a district court’s factual findings, however,
we retain plenary review to determine whether, as a legal
matter, the evidence satisfies the clear-and-convincing
standard of proof. Proctor & Gamble, 566 F.3d at 993–
94. Indeed, the Supreme Court recently confirmed that a
party asserting an obviousness claim bears that high
burden of persuasion. Microsoft Corp. v. i4i Ltd., 131 S.
Ct. 2238, 2242 (2011).
                            A.
     We find that the district court’s legal conclusion that
bioequivalence alone was sufficient to render the claims
at issue obvious was in error. We also find clear error in a
number of the district court’s factual findings, as identi-
fied below.
    The obviousness inquiry in this case is focused on bio-
equivalence. The concept of bioequivalence means the
body is exposed to the same amount of active pharmaceu-
tical ingredient at the same rate after administration of
either an immediate-release or extended-release formula-
tion. The district court found the asserted claims obvious
because it believed the claimed extended-release PK
profile is bioequivalent to the immediate-release PK
profile. Mylan agrees with the district court’s approach of
resting its obviousness finding on bioequivalence. Cepha-
lon, however, argues that the district court placed undue
weight on bioequivalence and, as a result, misinterpreted
the proffered prior art references.
EURAND   v. MYLAN                                       10


    We agree with Cephalon. The district court treated
bioequivalence as the end of its inquiry when the court
found that it would have been obvious to a person having
ordinary skill in the art to target extended-release PK
values “mirroring”—in other words, bioequivalent to—
those of the immediate-release cyclobenzaprine formula-
tion. The district court, however, was also required to
consider the asserted claims’ limitation requiring thera-
peutic effectiveness, and whether it would have been
obvious to one of ordinary skill in the art at the time of
the invention that a bioequivalent PK value would satisfy
that limitation. Graham, 383 U.S. at 17–18 (making clear
that “differences between the prior art and the claims at
issue are to be ascertained”) (emphasis added).
    Mylan and Par argued, and the district court agreed,
that the undisputed fact that cyclobenzaprine lacked a
known PK/PD relationship at the time of invention was
irrelevant. Without such a known relationship, however,
skilled artisans could not predict whether any particular
PK profile, including a bioequivalent one, would produce a
therapeutically effective formulation. Dr. Davis, Cepha-
lon’s expert, testified that cyclobenzaprine’s “mode of
action was not really well known and there [was] cer-
tainly no clear relationship between a given pharmacoki-
netic profile and the pharmacodynamic effect, what it
actually does to the body.” One of the defendants’ experts,
Dr. Gordon Amidon, acknowledged that there was nothing
in the prior art or published literature “that would help a
person skilled in the art determine a therapeutically
effective plasma concentration over a 24-hour period.”
    Mylan and Par did not dispute that cyclobenzaprine
lacked a known PK/PD relationship. Rather, they at-
tempted to avoid that fact in two ways. First, they as-
serted the truism that skilled artisans would need only a
reasonable expectation of success and would not need to
11                                         EURAND   v. MYLAN


be certain of what a particular PK profile would yield.
See Defs.’ Resp. & Reply Br. 26. Second, Mylan and Par
argued to the district court that the patents in suit lack
sufficient written description to support the “therapeuti-
cally effective” limitation. Lack of written description,
however, is a separate defense, which the defendants do
not advance on appeal. For purposes of obviousness,
therefore, we must accept as true that cyclobenzaprine
lacked a known PK/PD relationship at the time of inven-
tion, and that the asserted claims contain a valid “thera-
peutically effective” limitation.
     The district court misapprehended the importance of
the lack of a known PK/PD relationship. The district
court stated that “[t]he lack of a PK/PD relationship is of
no moment . . . given that one of ordinary skill in the art
would expect the extended release formulation to have the
same PD effect on the body if it has the immediate release
formulation’s PK profile.” That statement contains an
inherent contradiction. By stating that skilled artisans
would assume that the immediate-release and extended-
release PK profiles produce the same PD effect, the dis-
trict court was assuming that a known PK/PD relation-
ship existed for the immediate-release formulation.
Because all experts and parties agree, however, that
skilled artisans did not know the PK/PD relationship even
for the immediate-release formulation, there was no way
to match the dosage for the extended-release formulation
to achieve a known therapeutic effect. The district court,
therefore, could not find obviousness without finding that
the prior art would have taught or suggested a therapeu-
tically effective formulation to one of ordinary skill in the
art. The record lacks any such evidence. While it may
have been obvious to experiment with the use of the same
PK profile when contemplating an extended-release
formulation, there is nothing to indicate that a skilled
EURAND   v. MYLAN                                        12


artisan would have had a reasonable expectation that
such an experiment would succeed in being therapeuti-
cally effective. See Proctor & Gamble, 566 F.3d at 994
(requiring a reasonable expectation of success to prove
obviousness).
     This distinction is important. Where a skilled artisan
merely pursues “known options” from “a finite number of
identified, predictable solutions,” the resulting invention
is obvious under Section 103. KSR, 550 U.S. at 421.
Where, however, a defendant urges an obviousness find-
ing by “merely throw[ing] metaphorical darts at a board”
in hopes of arriving at a successful result, but “the prior
art gave either no indication of which parameters were
critical or no direction as to which of many possible
choices is likely to be successful,” courts should reject
“hindsight claims of obviousness.” In re Kubin, 561 F.3d
1351, 1359 (Fed. Cir. 2009) (quoting In re O’Farrell, 853
F.2d 894, 903 (Fed. Cir. 1988)).
                            B.
    The district court’s failure to appreciate the lack of a
known PK/PD relationship for any formulation of
cyclobenzaprine rendered deficient its analysis of the
evidence that Mylan and Par offered to prove the claimed
PK values obvious and its analysis of the implications of
that evidence on its legal conclusion of obviousness. We
explain below why the district court’s analysis was defi-
cient.
                             1.
    The district court found that a skilled artisan could
calculate the claimed AUC and Tmax by conducting what it
called “routine experimentation”: creating computer
models based on data from articles by Winchell and
Hucker, and PK data for Flexeril, the branded immediate-
13                                         EURAND   v. MYLAN


release formulation. The district court relied on the
testimony of Dr. Amidon in interpreting those prior art
references. 1 Mylan and Par agree with the district court,
arguing that the evidence shows that “one of ordinary
skill in the art could readily convert the known pharma-
cokinetic data for Flexeril® administered 10 mg three
times a day to an equivalent pharmacokinetic profile for a
single daily 30 mg administration.” Defs.’ Resp. & Reply
Br. 40.
    Dr. Amidon’s testimony, however, was insufficient to
support the conclusion that a skilled artisan would rea-
sonably expect to achieve a therapeutically effective AUC
and Tmax. Indeed, it was actually inconsistent with that
conclusion. As Dr. Amidon explained, Winchell reveals
that cyclobenzaprine is linear, which means that blood
plasma concentration increases proportionally to dosage.
The fact that a skilled artisan could have predicted a
particular blood plasma concentration, however, does not
mean that such knowledge would have provided a skilled
artisan a reasonable expectation of success in calculating
a blood plasma concentration that was therapeutically
effective. As Dr. Amidon also explained, Winchell sug-
gests that cyclobenzaprine is well absorbed in the body.
That information, however, pertains to the body’s physical
absorption of the drug rather than the correct PK/PD
relationship. As Dr. Amidon further explained, Winchell
provides PK values for immediate-release cycloben-

     1   The district court also relied upon the testimony
of another defense expert, Dr. Courtney Fletcher, to find
that the Tmax can be calculated when the other parame-
ters of the model are known. Because Cephalon is correct
that Dr. Fletcher was not qualified to testify to that point,
any reliance on Dr. Fletcher for this proposition was clear
error. Indeed, the district court seemed to concede this
point when responding to the errors that Cephalon identi-
fied in the court’s trial opinion.
EURAND   v. MYLAN                                       14


zaprine, and Hucker provides plasma concentration time
curves for the immediate-release formulation. Without a
known PK/PD relationship, however, immediate-release
PK values are of little use in calculating extended-release
values, because there is no proof that a skilled artisan
would expect the extended-release values to produce a
therapeutic effect solely because they are drawn from
immediate-release values.
    The evidence on which the district court relied to find
the claimed Cmax obvious similarly focuses on bare PK
values rather than the PD effect that the PK values could
be expected to produce. The district court found that
Winchell “undisputably [sic]” disclosed the claimed Cmax.
Winchell indicates that, after subjects are dosed every
eight hours for seven days at 10 mg/dose, subjects have a
Cmax of 25.9 ng/ml. That value is 129.5% of 20 ng/ml.
Claim 3 of the patents in suit claims a Cmax range of about
80% to 125% of about 20 ng/ml. The district court, how-
ever, cited no evidence specifically indicating that a
cyclobenzaprine PK profile with a Cmax of 129.5% of 20
ng/ml would be expected to yield the same therapeutic
effect as that with a Cmax range of about 80% to 125% of
about 20 ng/ml.
    The district court, moreover, cited nothing to support
a finding that the claimed Cmax range of about 80% to
125% of about 20 ng/ml even encompasses Winchell’s Cmax
of 129.5% of 20 ng/ml. Claim 3 does specify that the
claimed range is about 80% to 125% of about 20 ng/ml.
The district court construed the term “about” to mean
“approximately,” but failed to cite any evidence indicating
that 129.5% of 20 ng/ml is approximately 125% of 20
15                                        EURAND   v. MYLAN


ng/ml.     The parties have not directed us to any such
proof. 2
     The district court found persuasive Dr. Amidon’s ul-
timate opinion that a skilled artisan could expect to
achieve efficacy by relying on the Winchell and Hucker
articles to estimate a PK profile for an extended-release
formulation by using computer software. While we would
normally afford the district court deference in crediting
such an opinion, we cannot do so here because Dr. Amidon
failed to discuss why, in the specific context of cycloben-
zaprine, a skilled artisan would expect PK values drawn
from the prior art to yield a therapeutically effective
formulation. Indeed, the portion of Dr. Amidon’s testi-
mony on which the district court relied conflicts with his
acknowledgement that the prior art and published litera-
ture lacked any guidance to help a skilled artisan deter-
mine a therapeutically effective, extended-release plasma
concentration. Dr. Amidon’s own computer modeling,
moreover, failed to generate PK values within the claimed
ranges.
   Mylan and Par rely extensively on Dr. Amidon’s tes-
timony about the prior art in arguing that it would have
been obvious to try to develop extended-release cycloben-

     2  While it might appear to a layperson that 129.5%
is “about” 125%, expert testimony is necessary to estab-
lish how a person having ordinary skill in the art would
perceive those figures. We have no way of knowing the
importance of even small differences in these percentages
in the absence of some evidence in the record addressing
that point. See Ortho-McNeil Pharm., Inc. v. Caraco
Pharm. Labs., Inc., 476 F.3d 1321, 1326 (Fed. Cir. 2007)
(“The use of the word “about,” avoids a strict numerical
boundary to the specified parameter. Its range must be
interpreted in its technological and stylistic context.”
(quoting Pall Corp. v. Micron Separations, Inc., 66 F.3d
1211, 1217 (Fed. Cir. 1995))).
EURAND   v. MYLAN                                       16


zaprine bioequivalent to the immediate-release PK pro-
file, and that skilled artisans would have had a reason-
able expectation of success in doing so. The insufficiency
of that evidence demonstrates why the defendants’ argu-
ment stands on a weak foundation. Evidence of obvious-
ness, especially when that evidence is proffered in support
of an “obvious-to-try” theory, is insufficient unless it
indicates that the possible options skilled artisans would
have encountered were “finite,” “small,” or “easily trav-
ersed,” and that skilled artisans would have had a reason
to select the route that produced the claimed invention.
Ortho-McNeil Pharm., Inc. v. Mylan Labs., Inc., 520 F.3d
1358, 1364 (Fed. Cir. 2008) (citing KSR, 550 U.S. at 421).
While it is true that Section 103 bars patentability unless
“the improvement is more than the predictable use of
prior art elements according to their established func-
tions,” KSR, 550 U.S. at 417, where the prior art, at best,
“[gives] only general guidance as to the particular form of
the claimed invention or how to achieve it,” relying on an
“obvious-to-try” theory to support an obviousness finding
is “impermissible.” In re Kubin, 561 F.3d at 1359 (quoting
In re O’Farrell, 853 F.2d at 903). Nothing in Dr. Amidon’s
testimony sheds light on why a skilled artisan would have
chosen a bioequivalent PK profile in the absence of a
known PK/PD relationship for cyclobenzaprine. Thus, the
absence of such testimony suggests that skilled artisans
would not have encountered finite, small, or easily trav-
ersed options in developing a therapeutically effective,
extended-release formulation. See id. And, there is
nothing in the record to support the conclusion that what
the co-inventors did here was no more than a “predictable
use of known prior art elements.” KSR, 550 U.S. at 417.
   The Winchell and Hucker articles, the Flexeril data,
and the defense experts’ interpretation of those refer-
ences, fail to indicate that a skilled artisan would have
17                                         EURAND   v. MYLAN


reasonably expected to calculate therapeutically effective
PK values based on those references. While the district
court’s assessment of this evidence may be understand-
able given its predicate mistake regarding the absence of
a known PK/PD profile for the immediate-release formu-
lation, it was, nonetheless, clear error.
                             2.
    The district court also relied on other evidence to sup-
port its obviousness analysis. The district court’s factual
conclusions from this evidence again were clearly errone-
ous, however, and the weight given to them in the court’s
obviousness conclusion was undue.
    The district court noted that Dr. Clevenger, co-
inventor of the patents in suit, created computer models
of the claimed PK values after he reviewed the Flexeril
PK data. The district court cited Dr. Clevenger’s ap-
proach when it concluded that the claimed AUC and Tmax
could be obtained by “routine experimentation.” In rely-
ing on Dr. Clevenger’s testimony, the district court merely
retraced the inventor’s steps. This hindsight analysis is
inappropriate because obviousness must be assessed at
the time the invention was made. See Ortho-McNeil, 520
F.3d at 1364 (noting that 35 U.S.C. § 103(a) directs an
inquiry into whether the subject matter as a whole “would
have been obvious at the time the invention was made”).
Like the district court, Mylan and Par rely on Dr.
Clevenger’s testimony for the proposition that “one of
ordinary skill could use the available software . . . and
estimate the parameters identified by Mylan’s experts.”
Defs.’ Resp. & Reply Br. 41. Like the district court,
however, Mylan and Par employ hindsight analysis.
    Dr. Clevenger’s testimony, moreover, does not support
the proposition for which the district court cited it. The
district court found significant Dr. Clevenger’s testimony
EURAND   v. MYLAN                                         18


that “[i]t can be assumed that the [immediate-release
product] produced a therapeutic effect . . .” and that “if we
get something similar to those blood levels . . . then we,
too, will have a product that will produce a therapeutic
effect.” The district court, however, omitted the next
exchange in Dr. Clevenger’s examination: “[Question:] . . .
So the idea is that if the blood levels were similar to
Flexeril, then hopefully, the effect would be similar—the
therapeutic effect would be similar to Flexeril? [Answer:]
Hopefully. Depends on the relationship between blood
levels and therapeutic effect.” The district court later
attempted to minimize the importance of Dr. Clevenger’s
omitted testimony, concluding that “this testimony simply
shows that the inventor needed to verify his results in the
lab. Obviousness calls for an expectation of success, not a
guarantee.” A plain reading of the testimony, however,
indicates that Dr. Clevenger never expressed even an
expectation of success. He merely testified that, whether
blood levels similar to those produced by Flexeril would
produce a therapeutic effect similar to that of Flexeril,
depended on the relationship between blood levels and
therapeutic effectiveness—a relationship that all concede
was unknown.
    The district court also relied on an FDA guidance
document, which it found directed skilled artisans to
pursue bioequivalence when formulating extended-release
formulations. The title of the document the district court
cited is “Guidance for Industry.” The district court found
that the document sets forth an FDA directive that an
extended-release dosage form have the same AUC and
Cmax of an already-approved immediate-release formula-
tion. The FDA document, however, states that its pur-
pose is “to provide recommendations to sponsors and/or
applicants planning to include . . . bioequivalence infor-
mation” in applications. The document provides advice on
19                                         EURAND   v. MYLAN


what they should do if they plan to pursue bioequivalence.
The document provides little support for an obviousness
finding here, because, in the absence of a known PK/PD
relationship for cyclobenzaprine, there is no evidence that
a skilled artisan would have targeted bioequivalence in
the first instance.
    One judge of our court has observed that the FDA’s
publishing of approval requirements for extended-release
formulations does not necessarily render obvious a drug
that meets those requirements, because “knowledge of the
goal does not render its achievement obvious.” Abbott
Labs., Inc. v. Sandoz, Inc., 544 F.3d 1341, 1352 (Fed. Cir.
2009). That observation is particularly salient here
because Mylan and Par fail to demonstrate that skilled
artisans would have even viewed bioequivalence as the
goal when creating an extended-release cyclobenzaprine
formulation. Indeed, while there might have been a
desire for an extended-release formulation, there is no
evidence that skilled artisans would have known how to
achieve it. See Cardiac Pacemakers, Inc. v. St. Jude Med.,
Inc., 381 F.3d 1371, 1377 (Fed. Cir. 2004) (“Recognition of
a need does not render obvious the achievement that
meets that need. . . . Recognition of an unsolved problem
does not render the solution obvious.”).
                             3.
    Finally, the district court relied on two other prior art
references, neither of which supports a finding that the
“therapeutically effective” limitation is obvious. Those
references—U.S. Patent No. 6,344,215 and European
Patent Application No. 518,263A1 (“Urban”)—disclose
formulation technology and dissolution profiles rather
than pharmacokinetics. The Urban reference discloses a
micropellet that can be used for an extended-release
formulation. It lists cyclobenzaprine as a suitable me-
EURAND   v. MYLAN                                        20


dicament for the formulation. The ’215 patent—Dr.
Venkatesh is the named inventor—discloses a multipar-
ticulate dosage form, for use with methylphenidate, that
features the same dissolution profile claimed in the pat-
ents in suit. The district court believed that it would have
been obvious to use the same drug delivery system be-
cause it had already been proven effective with methyl-
phenidate. Mylan and Par, likewise, argue that “[t]he
only meaningful structural difference between the as-
serted claims of the ’793 patent and ’215 patent was the
active ingredient, cyclobenzaprine versus methylpheni-
date.” Defs.’ Resp. & Reply Br. 8.
    Even if the ’215 patent and Urban teach the claimed
physical drug delivery system and dissolution profile, they
reveal nothing about the critical limitation at issue here:
a therapeutically effective PK profile. Cephalon has
acknowledged that the structure of the drug delivery
system and the dissolution profile are not novel aspects of
the claimed invention. Oral Argument at 22:40, available
at            http://www.cafc.uscourts.gov/oral-argument-
recordings/2011-1399/all. Urban and the ’215 patent
provide no support for the district court’s obviousness
finding with respect to pharmacokinetics.
                             C.
    After the district court found that Mylan and Par
proved the asserted claims obvious, it considered Cepha-
lon’s proof of objective considerations of nonobviousness to
determine whether Cephalon’s proofs were sufficient to
“rebut” that obviousness determination. Specifically, the
district court considered Cephalon’s evidence of the fail-
ure of others to make the patented invention; longfelt but
unsolved needs fulfilled by the patented invention; com-
mercial success of the patented invention; and unexpected
results produced by the patented invention. See Graham,
21                                         EURAND   v. MYLAN


383 U.S. at 17–18; Pfizer, Inc. v. Apotex, Inc., 480 F.3d
1348, 1369 (Fed. Cir. 2007). The district court found
Cephalon’s evidence insufficient to rebut Mylan’s and
Par’s showing. The district court erred, however, by
making its finding that the patents in suit were obvious
before it considered the objective considerations and by
shifting the burden of persuasion to Cephalon. In doing
so, the district court contravened this court’s precedent
requiring that a fact finder consider all evidence relating
to obviousness before finding a patent invalid on those
grounds, and the court imposed a burden-shifting frame-
work in a context in which none exists.
                             1.
     The premature nature of the court’s obviousness find-
ing is apparent. Before it reached the objective considera-
tions, the district court stated that the claimed PK profile
“would have been obvious to one of skill in the art at the
time of the invention” and that “a person of ordinary skill
in the art would have been motivated to take a group of
known elements to create an extended release version of
cyclobenzaprine, and [would have had] a reasonable
expectation of success in doing so.” It was not until after
the district court found the asserted claims obvious that it
proceeded to analyze the objective considerations, or what
it called the “secondary considerations.”
                             2.
     The district court’s error is understandable because
this court has inconsistently articulated the burden of
proof applicable to an obviousness defense in district court
litigation. It was error nonetheless.
    In Stratoflex, Inc. v. Aeroquip Corp., we held that a
fact finder in district court litigation may not defer ex-
EURAND   v. MYLAN                                         22


amination of the objective considerations until after the
fact finder makes an obviousness finding:
         It is jurisprudentially inappropriate to
         disregard any relevant evidence on any is-
         sue in any case, patent cases included.
         Thus evidence rising out of the so-called
         “secondary considerations” must always
         when present be considered en route to a
         determination of obviousness. . . . Indeed,
         evidence of secondary considerations may
         often be the most probative and cogent
         evidence in the record. It may often estab-
         lish that an invention appearing to have
         been obvious in light of the prior art was
         not. It is to be considered as part of all the
         evidence, not just when the decisionmaker
         remains in doubt after reviewing the art.
713 F.2d 1530, 1538–39 (Fed. Cir. 1983) (citations omit-
ted). Many subsequent cases have expressly followed
Stratoflex’s directive that courts consider all objective
evidence before reaching an obviousness conclusion. See
Ruiz v. A.B. Chance Co., 234 F.3d 654, 663 (Fed. Cir.
2000) (“Our precedent clearly establishes that the district
court must make Graham findings before invalidating a
patent for obviousness.”); Cable Elec. Prods. v. Genmark,
Inc., 770 F.2d 1015, 1026 (Fed. Cir. 1985) (quoting Strato-
flex, 713 F.2d at 1539) (“The opinions of this court have
suggested that evidence on these secondary considera-
tions is to be taken into account always, ‘not just when
the decisionmaker remains in doubt after reviewing the
art.’”); Simmons Fastener Corp. v. Illinois Tool Works,
Inc., 739 F.2d 1573, 1575 (Fed. Cir. 1984); (“The section
103 test of nonobviousness set forth in Graham is a four
part inquiry comprising, not only the three familiar
elements (scope and content of the prior art, differences
23                                         EURAND   v. MYLAN


between the prior art and the claims at issue, and level of
ordinary skill in the pertinent art), but also evidence of
secondary considerations when such evidence is, of course,
present”); Richardson-Vicks Inc. v. Upjohn Co., 122 F.3d
1476, 1483 (Fed. Cir. 1997) (holding that “we must con-
sider all of the evidence under the Graham factors before
reaching our decision”); Rockwell Int’l Corp. v. United
States, 147 F.3d 1358, 1366 (Fed. Cir. 1998) (following
Richardson-Vicks); and Kan. Jack, Inc. v. Kuhn, 719 F.2d
1144, 1150–51 (Fed. Cir. 1983) (finding that a district
court’s consideration of commercial success complied with
“the basic requirement that all evidence touching the
obvious-nonobvious issue be fully considered before a
conclusion is reached on that issue” (citing In re Sernaker,
702 F.2d 989, 996 (Fed. Cir. 1983))).
     While many panels of this court have adhered to Stra-
toflex’s directive, some instead have spoken of the obvi-
ousness analysis in terms of a “prima facie” case which
must then be “rebutted” by the patentee. Under that
framework, a court inquires whether the party challeng-
ing validity has proven a “prima facie” case of obvious-
ness, based only on reference to the patent and the
proffered prior art, and only then considers objective
evidence, asking whether such evidence is sufficient to
overcome the prima facie case. 3

     3    See, e.g., Innovention Toys, L.L.C. v. MGA Entm’t,
Inc., 637 F.3d 1314, 1323 (Fed. Cir. 2011) (“[S]hould the
district court conclude [on remand] that [defendant] has
made out a prima facie case of obviousness based on the
[prior art], the court must then determine whether [plain-
tiff’s] secondary considerations overcome [defendant’s]
prima facie case”); Transocean Offshore Deepwater Drill-
ing, Inc. v. Maersk Contractors USA, Inc., 617 F.3d 1296,
1305 (Fed. Cir. 2010) (“If all of the factual disputes re-
garding the objective evidence resolve in favor of [plain-
tiff], it has presented a strong basis for rebutting the
EURAND   v. MYLAN                                        24


     Despite this language, however, those cases should
not be interpreted as establishing a formal burden-
shifting framework. This is so for a number of reasons.
First, a review of those cases indicates that in none was
the placement of the burden with respect to evidence of
objective considerations, or the timing of the fact finder’s
consideration of that evidence, determinative. See supra
n.3.
    Second, even panels that have used the “prima facie”
and “rebuttal” language generally have made clear that a
fact finder must consider all evidence of obviousness and
nonobviousness before reaching a determination. For
example, in Iron Grip Barbell Co. v. USA Sports, Inc.,
while the panel did hold that “there is no objective evi-
dence to rebut the strong showing of obviousness based on

prima facie case [of obviousness].”); Muniauction, Inc. v.
Thomson Corp., 532 F.3d 1318, 1327 (Fed. Cir. 2008)
(“Under the foregoing analysis, we conclude that [defen-
dant] has clearly and convincingly established a prima
facie case that claims 1 and 31 of the ’099 patent are
obvious as a matter of law. Accordingly, we turn to
[plaintiff’s] attempt to rebut this prima facie case with
secondary considerations of nonobviousness.”); Eli Lilly &
Co. v. Zenith Goldline Pharms., Inc., 471 F.3d 1369, 1380
(Fed. Cir. 2006) (“[Plaintiff] overcame any prima facie
case of obviousness . . . [because it] proved extensive
secondary considerations to rebut obviousness”); Ormco
Corp. v. Align Tech., Inc., 463 F.3d 1299, 1311 (Fed. Cir.
2006) (“A nonmovant may rebut a prima facie showing of
obviousness with objective indicia of nonobviousness.”);
Iron Grip Barbell Co. v. USA Sports, Inc., 392 F.3d 1317,
1325 (Fed. Cir. 2004) (“[W]e conclude that there is no
objective evidence to rebut the strong showing of obvious-
ness based on the prior art.”); and WMS Gaming Inc. v.
Int’l Game Tech., 184 F.3d 1339, 1359 (Fed. Cir. 1999)
(“The objective evidence of non-obviousness may be used
to rebut a prima facie case of obviousness based on prior
art references.”).
25                                         EURAND   v. MYLAN


the prior art,” 392 F.3d 1317, 1325 (Fed. Cir. 2004), it also
cautioned that, in “determining the question of obvious-
ness, inquiry should always be made into whatever objec-
tive evidence of nonobviousness there may be.” Id. at
1323 (quoting Vandenberg v. Dairy Equip. Co., 740 F.2d
1560, 1567 (Fed. Cir. 1984)). In Transocean Offshore
Deepwater Drilling, Inc. v. Maersk Contractors USA, Inc.,
while the panel observed that, “[i]f all of the factual
disputes regarding the objective evidence resolve in favor
of [plaintiff], it has presented a strong basis for rebutting
the prima facie case [of obviousness],” the panel stated,
“[t]o be clear, a district court must always consider any
objective evidence of nonobviousness presented in a case.”
617 F.3d 1296, 1305 (Fed. Cir. 2010). And in WMS Gam-
ing Inc. v. International Game Technology, while the
panel stated that “[t]he objective evidence of non-
obviousness may be used to rebut a prima facie case of
obviousness based on prior art references,” it also stated
that “[t]he consideration of the objective evidence pre-
sented by the patentee is a necessary part of the obvious-
ness determination.” 184 F.3d 1339, 1359 (Fed. Cir.
1999). Thus, a reading of these cases that permits a fact
finder to reach a conclusion of obviousness before consid-
ering all relevant evidence, including evidence of objective
considerations, would not only conflict with Stratoflex’s
directive that objective considerations are “to be consid-
ered as part of all the evidence, not just when the deci-
sionmaker remains in doubt after reviewing the art,” 713
F.2d at 1538, but would ignore their actual holdings.
    Next, the Supreme Court has never imposed nor even
contemplated a formal burden-shifting framework in the
patent litigation context. 4 It has, instead, required that

     4 The Court’s treatment of the burden of persuasion
in the obviousness context markedly differs from its
treatment of the burden of persuasion in other contexts,
EURAND   v. MYLAN                                        26


all evidence relevant to obviousness or nonobviousness be
considered, and be considered collectively. In Graham,
the Court stated that “[s]uch secondary considerations as
commercial success, long felt but unsolved needs, failure
of others, etc., might be utilized to give light to the cir-
cumstances surrounding the origin of the subject matter
sought to be patented,” along with the scope and content
of the prior art, the differences between the prior art and
the claims at issue, and the level of ordinary skill in the
pertinent art. 383 U.S. at 17–18. Notably, the Court did


such as employment discrimination claims under Title VII
of the Civil Rights Act of 1964. In McDonnell Douglas
Corp. v. Green, the Court established the well-known
formal, three-part burden-shifting framework that a
plaintiff must satisfy to prove a discrimination claim with
circumstantial evidence. 411 U.S. 792 (1973). Several
differences are apparent between the Court’s burden-
shifting framework under McDonnell Douglas and its
treatment of the burden of proof with respect to obvious-
ness. First, the term “prima facie,” as used in the
McDonnell Douglas context, means “the establishment of
a legally mandatory, rebuttable presumption,” as opposed
to “the plaintiff’s burden of producing enough evidence to
permit the trier of fact to infer the fact at issue.” Tex.
Dep’t of Cmty. Affairs v. Burdine, 450 U.S. 248, 254 n.7
(1981). As discussed above, the Court has never spoken
in terms of a legally rebuttable presumption with respect
to obviousness. Second, the Court’s rationale for fashion-
ing a formal burden-shifting framework in employment
discrimination cases is to facilitate inquiry into an em-
ployer’s intent: “the allocation of burdens and the creation
of a presumption by the establishment of a prima facie
case is intended progressively to sharpen the inquiry into
the elusive factual question of intentional discrimination.”
Burdine, 256 F.3d at 256 n.8. While the obviousness
inquiry undoubtedly demands precision, the Court has
never identified a problem in its application such that
“sharpening” by way of a burden-shifting scheme is neces-
sary.
27                                         EURAND   v. MYLAN


not characterize the objective factors as after-the-fact
considerations or relegate them to “secondary status.”
The Court, rather, indicated that the objective considera-
tions have broader applicability, noting that, “[a]s indicia
of obviousness or nonobviousness, these inquiries may
have relevancy.” Id. The Court recently reaffirmed this
approach to objective considerations when it described the
obviousness inquiry as “expansive and flexible” and noted
that Graham “invite[s] the courts, where appropriate, to
look at any secondary considerations that would prove
instructive.” KSR, 550 U.S. at 415. And, in i4i, the Court
reaffirmed both the scope and placement of the burden of
proof in these circumstances. 131 S. Ct. at 2245, n.4.
    In i4i, the Court was asked to articulate the standard
of proof a party must satisfy to prove an invalidity de-
fense. 131 S. Ct. at 2242. The Court held that the stan-
dard of proof is proof by clear and convincing evidence.
Id. In explaining that holding, the Court differentiated
between the concepts of burden of proof, burden of pro-
duction, burden of persuasion, and standard of proof. Id.
at 2245. As the Court explained, the commonly used term
“burden of proof” encompasses the concepts of “burden of
persuasion” and “burden of production.” Id. at 2245 n.4.
The burden of persuasion specifies “which party loses if
the evidence is balanced,” while the burden of production
specifies “which party must come forward with evidence
at various stages in the litigation.” Id. at 2245 n.4. The
standard of proof, the court further explained, specifies
“how difficult it will be for the party bearing the burden of
persuasion to convince the jury of the facts in its favor.”
Id. at 2245 n.4.
    The Court resorted to common-law principles to de-
termine that the standard of proof is proof by clear and
convincing evidence because the Patent Act does not
explicitly articulate the standard of proof. Id. at 2245–
EURAND   v. MYLAN                                         28


46. By contrast, the Court noted, the Patent Act specifies
that the burden of proof is placed on the party challenging
validity: “The burden of establishing invalidity of a patent
or any claim thereof shall rest on the party asserting such
invalidity.” Id. at 2245 (quoting 35 U.S.C. § 282). The
Court provided no indication that it believes the burden of
persuasion should shift to the patentee at some point to
prove nonobviousness. 5
    Finally, not only is Stratoflex the law, it is sound in
requiring that a fact finder consider the objective evidence
before reaching an obviousness determination.            The
objective considerations, when considered with the bal-
ance of the obviousness evidence in the record, guard as a
check against hindsight bias. Graham, 383 U.S. at 36
(quoting Monroe Auto Equip. Co. v. Heckethorn Mfg. &
Supply Co., 332 F.2d 406, 412 (6th Cir. 1964)). In Gra-
ham, the Court recognized the danger of hindsight bias
and the ameliorative effect that the objective considera-
tions might offer. In discussing the utility of the objective
considerations, the Court cited a law review note pub-
lished after the nonobviousness requirement was enacted
in the 1952 Patent Act. Id. at 18 (citing Richard L. Rob-
    5   It is true that, in most cases, it is a patentee who
chooses to offer proof of objective considerations as evi-
dence of nonobviousness. It is also true that district
courts will often impose a discovery obligation on patent-
ees to be the first to produce evidence relating to objective
considerations. And, it is true that district courts also
often require patentees to present their objective evidence
during their case in chief to make an efficient use of time
and resources during trial, relying on their authority
under Federal Rule of Evidence 611(a) to structure the
presentation of evidence. Those realities do not change
the fact that the party challenging validity bears the
burden of persuasion throughout the litigation. i4i, 131 S.
Ct. at 2245 & n.4.
29                                         EURAND   v. MYLAN


bins, Subtests of “Nonobviousness”: A Nontechnical Ap-
proach to Patent Validity, 112 U. Pa. L. Rev. 1169 (1964)
(“Robbins”)). In that note, the author argued that the
instruments of decision-making applied in patent cases at
the time were inadequate and allowed judges to rely on
“judicial hunches,” thereby deciding cases on extralegal
grounds. Robbins, 112 U. Pa. L. Rev. at 1170 & n.11
(citing Joseph C. Hutcheson, Jr., The Judgment Intuitive:
The Function of the “Hunch” in Judicial Decisions, 14
Cornell L.Q. 274, 278 (1929)). Such “judicial hunches” are
encouraged by hindsight bias. As one commentator
recently observed, “decision-makers unconsciously let
knowledge of the invention bias their conclusion concern-
ing whether the invention was obvious in the first in-
stance.”    Gregory N. Mandel, Patently Non-Obvious:
Empirical Demonstration that the Hindsight Bias Renders
Patent Decisions Irrational, 67 Ohio St. L.J. 1391, 1393
(2006). In other words, knowing that the inventor suc-
ceeded in making the patented invention, a fact finder
might develop a hunch that the claimed invention was
obvious, and then construct a selective version of the facts
that confirms that hunch. This is precisely why the
Supreme Court explained that objective considerations
might prevent a fact finder from falling into such a trap,
observing that objective considerations might serve to
“resist the temptation to read into the prior art the teach-
ings of the invention in issue.” 383 U.S. at 36. 6 And, it is

     6  To be sure, courts must exercise care in assessing
proffered evidence of objective considerations, giving such
evidence weight only where the objective indicia are
“attributable to the inventive characteristics of the dis-
covery as claimed in the patent.” See Rochelle Cooper
Dreyfuss, The Federal Circuit: A Case Study in Special-
ized Courts, 64 N.Y.U. L. Rev. 1, 10 (1989) (noting that
this court has imposed such a “nexus” requirement on the
objective considerations). See also Ormco Corp. v. Align
EURAND   v. MYLAN                                        30


precisely why fact finders must withhold judgment on an
obviousness challenge until it considers all relevant
evidence, including that relating to the objective consid-
erations.
    In sum, opinions of this court should not be read to
require a burden-shifting framework in derogation of
Stratoflex’s directive that objective evidence be considered
before making an obviousness determination and in
disregard of where the burdens of proof and persuasion
are properly placed in district court litigation. 7 Such a

Tech., Inc., 463 F.3d 1299, 1311–12 (Fed. Cir. 2006)
(noting that a nexus must exist between a product’s
commercial success and the claimed invention).
   7     It appears that the language discussing a two-
part, burden-shifting inquiry may have originated in and
been borrowed from the test employed in appeals from the
Board of Patent Appeals and Interferences. In Iron Grip
Barbell, for example, we stated that a “presumption of
obviousness” that exists when a claimed invention falls
within a range disclosed in the prior art could be “rebut-
ted if it can be shown: (1) That the prior art taught away
from the claimed invention . . . or (2) that there are new
and unexpected results.” 392 F.3d at 1322. For that
proposition, we cited In re Geisler, 116 F.3d 1465, 1471
(Fed. Cir. 1997), and In re Woodruff, 919 F.2d 1575, 1578
(Fed. Cir. 1990). Both of those cases were appeals from
obviousness rejections during prosecution. In re Geisler,
116 F.3d at 1467; In re Woodruff, 919 F.2d at 1575.

    Unlike in district court litigation, a burden-shifting
framework makes sense in the prosecution context. The
prima facie case furnishes a “procedural tool of patent
examination, allocating the burdens of going forward as
between examiner and applicant.” In re Oetiker, 977 F.2d
1443, 1445 (Fed. Cir. 1992). During prosecution, a patent
applicant, as a practical matter, may not have the oppor-
tunity to present objective evidence unless and until an
examiner reviews the application and issues an obvious-
31                                         EURAND   v. MYLAN


reading disregards our own precedent and is inconsistent
with Supreme Court case law, including very recent case
law.
                                3.
    The district court appears to have fallen into the un-
derstandable but improper trap of constructing a selective
version of the facts relating to the objective considerations
so as to confirm its hunch that the asserted claims were
obvious. The district court focused on objective evidence
that supported its obviousness determination, but ignored

ness rejection. This is because “the examiner bears the
initial burden, on review of the prior art or on any other
ground, of presenting a prima facie case of unpatentabil-
ity. If that burden is met, the burden of coming forward
with evidence or argument shifts to the applicant.” Id.
Courts should not apply the burden-shifting framework
for patentability appeals to invalidity determinations
appealed from a district court, however, because the
prosecution and litigation contexts are distinct.

     In the prosecution context, not only are the decision
maker and the patent holder the only two parties in-
volved, but that decision maker—the examiner—is re-
quired to determine patentability by a preponderance of
the evidence. Id. Evidence of objective considerations
also may not be available until years after an application
is filed, and until long after the examiner first considers
the prior art. Litigation differs significantly from the
examination process. First, in the litigation context,
validity, rather than patentability, is the issue. The
challenged patent enjoys a presumption of validity, and
the challenger must convince a third-party decision
maker of the patent’s invalidity by clear and convincing
evidence. 35 U.S.C. § 282; i4i, 131 S. Ct. at 2242. And, in
litigation, all relevant evidence is presented to the fact
finder in a single proceeding. There is simply no practical
need to impose a burden-shifting framework in litigation.
EURAND   v. MYLAN                                        32


other evidence that cast the objective considerations in a
light favorable to Cephalon. And, it is clear that the
district court assumed that it was Cephalon’s burden to
disprove the court’s initial obviousness finding.
    Had the district court, instead, considered the objec-
tive evidence in its entirety before making an obviousness
finding, and considered that evidence in light of the actual
burden imposed upon a patentee and a patent challenger,
much of that evidence would have encouraged the district
court to question the claim that the mere existence of an
immediate-release formulation of cyclobenzaprine made
an extended-release version of that drug obvious. Specifi-
cally, we find that evidence of a longfelt need for an
extended-release formulation and the failure of others to
formulate one strongly support a conclusion of nonobvi-
ousness. We address each of these considerations.8



     8   We find no error in the district court’s conclusion
that Cephalon failed to offer adequate proof of reduced
sedation through its formulation and, thus, could not rely
on unexpected results to support its contention that
Mylan and Par failed to prove obviousness by clear and
convincing evidence. While we question the trial court’s
interpretation of Eurand’s evidence of commercial success,
moreover, we cannot find clear error therein. That these
objective criteria do not strongly support a finding of
nonobviousness does not affect our conclusions, however.
On both points, we find the evidence to be neutral; while
they do not support a finding of nonobviousness, they add
little to Mylan and Par’s claim of obviousness. While
evidence of reduced sedation may not have been strong,
the patents in suit do not claim that benefit; they claim
only therapeutic effectiveness. And, while Amrix’s com-
mercial success may be slow in coming, it is clear its
success is increasing, as its benefits—particularly greater
compliance—become known.
33                                         EURAND   v. MYLAN


                             a.
    Cephalon claims that another pharmaceutical com-
pany, ALZA, tried but failed to develop an extended-
release cyclobenzaprine formulation. 9 The district court
rejected this claim, because, in its view, ALZA’s goals
were different than Cephalon’s. Mylan and Par endorse
the district court’s reasoning. The district court, however,
ignored the fact that Cephalon and ALZA shared a com-
mon goal: to make a therapeutically effective product.
This was clear error.
    Evidence that others tried but failed to develop a
claimed invention may carry significant weight in an
obviousness inquiry. “While absolute certainty is not
necessary to establish a reasonable expectation of success,
there can be little better evidence negating an expectation
of success than actual reports of failure.” Boehringer
Ingelheim Vetmedica, Inc. v. Schering-Plough Corp., 320
F.3d 1339, 1354 (Fed. Cir. 2003). This is particularly true
when the evidence indicates that others found develop-
ment of the claimed invention difficult and failed to
achieve any success. Advanced Display Sys. v. Kent State
Univ., 212 F.3d 1272, 1285 (Fed. Cir. 2000). In such
circumstances, “evidence of failed attempts by others
could be determinative on the issue of obviousness.” Id.
    The evidence of ALZA’s failure to develop an ex-
tended-release formulation strongly supports a nonobvi-
ousness finding. In the late 1990s, ALZA performed
pharmacokinetic modeling and created a PK profile for
immediate-release cyclobenzaprine dosed three times a

     9   Cephalon also claims that Merck and Schering-
Plough tried but failed to develop an extended-release
formulation. The evidence of Merck’s and Schering-
Plough’s alleged failures, however, is weak, and the
district court did not clearly err in disregarding it.
EURAND   v. MYLAN                                        34


day. This approach was similar to the manner in which
Drs. Venkatesh and Clevenger modeled their PK profile.
The immediate-release PK profile that ALZA modeled
represented “peaks and valleys” on a graph, with blood
plasma concentrations undulating as time passed. ALZA
then hypothesized a PK profile for an extended-release
cyclobenzaprine product based on its model for the imme-
diate-release product. For its extended-release PK profile,
ALZA chose a straight line that cut through the immedi-
ate-release profile, staying below the peaks and above the
valleys. ALZA hoped that staying below the peaks would
avoid side effects and that staying above the valleys
would maintain therapeutic effectiveness. Clinical trials,
however, revealed that ALZA’s product was not therapeu-
tically effective. ALZA lost $10 million in its unsuccessful
attempt to develop an extended-release formulation.
    At trial, Cephalon called a former ALZA vice presi-
dent, Dr. Samuel Saks. Cephalon’s counsel showed Dr.
Saks Cephalon’s PK profile. That profile indicated that
Cephalon had departed from ALZA’s attempt to cut
through the immediate release PK profile’s peaks and
valleys. Rather, Cephalon had chosen a PK profile in
which the Cmax rose higher and the minimum blood
plasma concentration (Cmin) dipped lower than those of the
immediate-release profile. After reviewing Cephalon’s PK
profile, Dr. Saks expressed surprise that Cephalon suc-
ceeded, because he believed a lower Cmin would be less
effective. Thus, where ALZA failed to develop a therapeu-
tically effective product, Cephalon took a materially
different approach and succeeded. Evidence that others
were “‘going in different ways’ is strong evidence that the
[inventor’s] way would not have been obvious.” Panduit
Corp. v. Dennison Mfg. Co., 774 F.2d 1082, 1099 (Fed. Cir.
1985), vacated and remanded on other grounds, 475 U.S.
809 (1986).
35                                         EURAND   v. MYLAN


    The district court disregarded ALZA’s failures. ALZA
intended to make a formulation that was not only thera-
peutically effective, but one that also reduced side effects.
Cephalon’s patents do not cover a formulation that re-
duces side effects. The district court noted that an alleged
failure must be directed to the problem that a patent
purports to solve. Symbol Techs., Inc. v. Opticon, Inc., 935
F.2d 1569, 1578 (Fed. Cir. 1991). Because ALZA had the
additional goal of reducing side effects, the district court
believed that ALZA’s failure was not directed to the
problem that Cephalon’s patents purport to solve.
     The district court clearly erred because it disregarded
that Cephalon and ALZA did share a central common
goal: to create a therapeutically effective product. There
is no dispute that AZLA sought to create a product that
worked. The patents in suit, of course, cover a therapeu-
tically effective PK profile. The district court was not
required to disregard Cephalon and ALZA’s common goal
simply because ALZA had an additional goal not encom-
passed by the patents in suit. The purpose of evidence of
failure of others is to show “indirectly the presence of a
significant defect in the prior art, while serving as a
simulated laboratory test of the obviousness of the solu-
tion to a skilled artisan.” Symbol Techs., 935 F.2d at
1578–79 (quoting Robbins, 112 U. Pa. L. Rev. at 1173).
ALZA’s failure accomplishes that purpose, confirming
that a therapeutically effective PK profile was lacking in
the prior art and that skilled artisans struggled to attain
it. Such a scenario is classic evidence of nonobviousness.
See, e.g., Advanced Display Sys., 212 F.3d at 1285 (hold-
ing that the objective evidence supported an obviousness
finding where others had “tried for a long time” to develop
the claimed invention but found it “very hard” and “were
all not successful”). ALZA’s failure to develop a therapeu-
tically effective product, in sum, is keyed to the problem
EURAND   v. MYLAN                                          36


that the patents in suit purport to solve, and it supports a
finding that Cephalon’s accomplishment was not obvious
to those skilled in the art.
                              b.
    Cephalon also claimed that a longfelt need existed for
an extended-release cyclobenzaprine formulation and that
Amrix satisfied that need. The district court rejected that
argument because it believed Cephalon failed to offer any
expert testimony to support it. The district court’s as-
sessment of this factor was inadequate.
    Longfelt need is closely related to the failure of others.
Evidence is particularly probative of obviousness when it
demonstrates both that a demand existed for the patented
invention, and that others tried but failed to satisfy that
demand. See, e.g., In re Piasecki, 745 F.2d 1468, 1475
(Fed. Cir. 1984) (finding nonobviousness where the evi-
dence demonstrated a failure of others to provide a feasi-
ble solution to a longstanding problem); Alco Standard
Corp. v. Tenn. Valley Auth., 808 F.2d 1490, 1500 (Fed.
Cir. 1986) (affirming a nonobviousness finding where the
evidence showed that the relevant industry had searched
for more than a decade for a reliable solution and that
major manufacturers in the industry had tried but failed
to develop such a solution).
    Cephalon’s proof indicates that a longfelt need existed
for a therapeutically effective, extended-release cycloben-
zaprine formulation. The immediate-release formulation
existed for decades, but that formulation’s regimen of
multiple daily doses led to poor patient compliance. As
discussed above, moreover, others tried but failed to
develop an extended-release version. In addition to these
facts, Cephalon called Dr. David Steiner, a physician who
has practiced in pain management for more than a dec-
ade. Dr. Steiner discussed his experiences treating his
37                                        EURAND   v. MYLAN


patients’ pain in the clinic. He testified that patient
compliance with a medical regimen is important and that
he began prescribing Amrix, in part, because of the pros-
pect of more convenient dosing for his patients.
     Not only was the district court wrong that Cephalon
produced no expert testimony on this issue, but the dis-
trict court was wrong to ignore the non-expert evidence
proffered on this point. In combination with compelling
evidence of the failure of others to produce an extended-
release formulation, this factor further supports a nonob-
viousness finding.
                            4.
    Where, as here, the obviousness determination turns
on whether one of ordinary skill in the art would have
expected that a particular formulation of an extended-
release drug would be successful—in other words, would
render a therapeutically effective treatment—objective
indicia of failure of others and longfelt need are particu-
larly telling. The district court would have encountered a
different landscape had it examined the objective evidence
in light of the absence of a known PK/PD relationship.
ALZA’s failure to develop a therapeutically effective,
extended-release formulation suggests that skilled arti-
sans would not have reasonably expected to succeed in
developing the claimed formulation. The long delay
between the marketing of an immediate-release formula-
tion and Amrix, and Dr. Steiner’s testimony of longfelt
need, moreover, supports the inference that it was diffi-
cult for researchers to create a therapeutically effective,
extended-release product. Because a desire existed for
such a product, researchers, presumably, would have
created one if they were able to do so.
   Rather than supporting a finding of obviousness, the
most relevant objective considerations, when considered
EURAND   v. MYLAN                                         38


as part of the totality of the evidence, support a nonobvi-
ousness finding.
                             D.
     The record, in sum, is insufficient to support a conclu-
sion of obviousness by clear and convincing evidence. At
its core, Mylan and Par’s proof of obviousness is that the
claimed PK profile is bioequivalent to the immediate-
release profile. In rejecting the sufficiency of Mylan and
Par’s proof, we do not hold that bioequivalence can never
serve as evidence of obviousness. Indeed, it is most
certainly relevant to that inquiry. We only hold that, on
the facts of this case—in which therapeutic effectiveness
is a claimed limitation and the parties do not dispute that
cyclobenzaprine lacked a known PK/PD relationship—
Mylan and Par cannot rely on bioequivalence as the sole
basis for an obviousness finding, particularly given the
heavy burden of proof imposed on them in this context.
Indeed, defense counsel acknowledged at oral argument
that Mylan and Par are not requesting a categorical rule
that it is always obvious to try to target bioequivalence
when formulating an extended-release formulation. See
Oral       Argument       at      8:54,      available     at
http://www.cafc.uscourts.gov/oral-argument-
recordings/2011-1399/all. If we were to affirm the district
court’s obviousness ruling on the basis of this record, we
effectively would announce such a rule. 10

    10  The parties have not cited any cases in which the
presence or absence of a known PK/PD relationship was
determinative. Indeed, in other cases, it appears that the
parties and the court assumed bioequivalence would
produce a therapeutically effective result. See Abbott
Labs. v. Andrx Pharms., Inc., 452 F.3d 1331, 1340–43
(Fed Cir. 2006) (finding a substantial question of validity
on a preliminary injunction motion where the prior art
disclosed substantially bioequivalent PK values, but
39                                         EURAND   v. MYLAN


    The district court erred in finding that Mylan and Par
proved that the asserted claims are obvious by clear and
convincing evidence.
                            IV.
    We address next Mylan and Par’s best mode defense.
The district court rejected Mylan and Par’s claim that the
patents in suit are invalid for failure to disclose the best
mode. Although the district court applied the incorrect
test for a best mode disclosure violation, the district
court’s findings support its ultimate conclusion that no
best mode disclosure violation existed.
     A patent’s specification must “set forth the best mode
contemplated by the inventor of carrying out his inven-
tion.” 35 U.S.C. § 112 ¶ 1 (2006). The version of the
Patent Act currently in effect provides that, although an
applicant must disclose the best mode to register a patent,
a party to a lawsuit may not rely on an alleged best mode
disclosure violation to cancel, invalidate, or hold a patent
otherwise unenforceable.        Id.; Leahy-Smith America
Invents Act, Pub. L. No. 112-29, sec. 15(a), 125 Stat. 284,
328 (2011) (to be codified at 35 U.S.C. § 282 ¶ 2(3)(A)).
That provision, however, is inapplicable to this case
because it is the product of amendments made to the
Patent Act that became effective after this action was
filed. Leahy-Smith America Invents Act, Pub. L. No. 112-
29, sec. 15(c), 125 Stat. 284, 328 (2011) (providing that the
best mode amendments apply only to actions commenced

failing to address whether bioequivalent PK values would
produce a therapeutically effective result); Adams Respi-
ratory Therapeutics, Inc. v. Perrigo Co., 616 F.3d 1283,
1289 (Fed. Cir. 2010) (reversing a district court’s grant of
summary judgment because a fact finder could reasonably
find infringement based on the accused ANDA product’s
having a Cmax equivalent to that of a standard immediate-
release product).
EURAND   v. MYLAN                                         40


on or after the effective date of the amendments). The
version of the Patent Act applicable to this case permits
an accused infringer to assert a best mode disclosure
violation as a defense. 35 U.S.C. § 282 ¶ 2(3) (2006).
    A defense of failure to disclose the best mode is a
question of fact. Zygo Corp. v. Wyko Corp., 79 F.3d 1563,
1566–67 (Fed. Cir. 1996). We review a lower court’s
finding of no best mode disclosure violation for clear error.
Id.
    Mylan and Par claim that the specification fails to
disclose the best mode because it omits a particular range
of dew points. The claimed cyclobenzaprine formulation
is made with a coated bead. During the formulation
process, the bead is placed in a fluid bed machine, which
sprays a layer of the drug and a layer of extended-release
coating on the bead. The dew point of the air entering the
fluid bed must be controlled. Mylan and Par claim that
Dr. Venkatesh preferred dew points of 6–12ºC for imme-
diate-release coating and 7–16ºC for extended-release
coating, with target dew points of 8ºC and 10ºC, respec-
tively. The specification does not disclose those dew
points.
    To determine whether a best mode disclosure viola-
tion exists, a fact finder applies a two-prong test. First,
the fact finder determines whether, at the time the appli-
cation was filed, the inventor possessed a best mode for
practicing the invention. Eli Lilly & Co. v. Barr Labs.,
Inc., 251 F.3d 955, 963 (Fed. Cir. 2001) (citations omit-
ted). A subjective inquiry, the first prong focuses on “the
inventor’s state of mind at the time he filed the patent
application, and asks whether the inventor considered a
particular mode of practicing the invention to be superior
to all other modes at the time of filing.” Teleflex, Inc. v.
41                                         EURAND   v. MYLAN


Ficosa N. Am. Corp., 299 F.3d 1313, 1330 (Fed. Cir. 2002)
(citation omitted).
     The district court found that Dr. Venkatesh preferred
particular dew points at the time the applications were
filed. In March 2003, before the patent applications were
filed, Dr. Venkatesh told the FDA that, during scale-up
experiments, “the dew point of the incoming air was
monitored by setting the control at a very low target of
8°C (6–12)°C” and that “[d]ecreasing the dew point of the
incoming process air reduced the tackiness of the beads
and reduced the tendency of the coated beads from clump-
ing together.” Dr. Venkatesh acknowledged that dew
points could affect dissolution: “If you don’t use the proper
optimization, then you may not get good yield or you may
not get the proper coating . . . [t]hen the product will not
be good . . . .” While Cephalon argued to the district court
that Dr. Venkatesh did not have a subjective belief in a
best mode, Cephalon does not contest on appeal the
district court’s finding that he did have such a belief, and
we do not find that finding to have been clearly erroneous
in any event.
     If the inventor possessed a best mode at the time of
filing, as the district court found Dr. Venkatesh did, the
second prong of the inquiry requires the fact finder to
determine whether the specification discloses sufficient
information such that one reasonably skilled in the art
could practice the best mode. Eli Lilly, 251 F.3d at 963
(citations omitted). Because the second prong focuses on
what the specification teaches to a person of ordinary skill
in the art, the inquiry is objective. Id.
    Mylan and Par mistakenly attempt to cast the second
prong as an inquiry concerning whether Dr. Venkatesh
“concealed” his best mode. Defs.’ Resp. & Reply Br. 50.
That characterization is inaccurate. Concealment impli-
EURAND   v. MYLAN                                       42


cates an inventor’s state of mind, which is inconsistent
with an objective inquiry focused on what the specifica-
tion teaches to a skilled artisan. U.S. Gypsum Co. v. Nat’l
Gypsum Co., 74 F.3d 1209, 1215–16 (Fed. Cir. 1996). As
we explained in U.S. Gypsum, this court has used the
term “concealment” as a shorthand way of inquiring about
the adequacy of the disclosure:
         The “concealment” language of our case
         law originated in In re Gay, 309 F.2d 769
         (CCPA 1962). In Gay, the Court of Cus-
         toms and Patent Appeals (CCPA) ex-
         plained that “the sole purpose of [the best
         mode] requirement is to restrain inventors
         from applying for patents while at the
         same time concealing from the public pre-
         ferred embodiments of their inventions
         which they have in fact conceived.” . . .
         Subsequently, the CCPA clarified that
         “only evidence of concealment (whether
         accidental or intentional) is to be consid-
         ered. That evidence, in order to result in
         affirmance of a best mode rejection, must
         tend to show that the quality of an appli-
         cant’s best mode disclosure is so poor as to
         effectively result in concealment.” In re
         Sherwood, 613 F.2d 809, 816 (CCPA
         1980).
Id. Thus, the proper inquiry focuses on the adequacy of
the disclosure rather than motivation for any nondisclo-
sure. See also Bayer AG v. Schein Pharms., Inc., 301 F.3d
1306, 1320 (Fed. Cir. 2002) (explaining that the inquiry is
objective).
    The district court did not directly address whether the
specification adequately disclosed the best mode. Rather,
43                                         EURAND   v. MYLAN


the district court found that the dew points did not need
to be disclosed because they amounted to routine details.
We have recognized that routine details apparent to one
of ordinary skill in the art need not be disclosed to satisfy
the best mode disclosure requirement. E.g., Teleflex, 299
F.3d at 1331–32; Eli Lilly, 251 F.3d at 963; and Young
Dental Mfg. Co. v. Q3 Special Prods., Inc., 112 F.3d 1137,
1144 (Fed. Cir. 1997).
    To conclude that the optimal dew points were routine
details exempt from disclosure, the district court was
required to find that the dew points would be apparent to
a person of ordinary skill in the art. Teleflex, 299 F.3d at
1331–32. The district court found the following: (1) it
would be routine to control humidity during product
fabrication; (2) the allegedly concealed dew points were
within the normal operating range of a commonly used
fluid-bed coating device; (3) Dr. Venkatesh’s optimal dew
point was within the normal operating range; and (4) the
defendants’ own technicians were able to optimize the
dew point in just a few days. That evidence does not
indicate that the optimal dew points would actually be
apparent to one of ordinary skill in the art. If they were,
the evidence, presumably, would indicate that skilled
artisans would know the optimal dew points and program
the fluid bed accordingly before commencing production.
The district court’s findings indicate, rather, that some,
albeit minimal, work was required to ascertain the opti-
mal dew points.
    Rather than finding that the dew points were routine
details apparent to one of ordinary skill in the art, the
district court could, and should, have made a more fun-
damental finding: that the specification need not disclose
the optimal dew points to enable skilled artisans to prac-
tice the best mode. See U.S. Gypsum, 74 F.3d at 1215–16
(focusing the inquiry on the adequacy of the disclosure).
EURAND   v. MYLAN                                       44


As one expert, Dr. Robert Williams, explained, skilled
artisans do not begin the fabrication process by attempt-
ing to attain a particular dew point in the fluid bed.
Rather, they attempt to manipulate and harmonize a
number of parameters, including, for example, air humid-
ity, inlet air quantity, inlet air temperature, and spray
rate. Dew point is a function of the other parameters.
The totality of these parameters, when harmonized,
creates the optimal condition for fabricating product.
Thus, as the district court’s findings suggest, skilled
artisans would expect to attain the optimal dew points
during the ordinary harmonization process by employing
routine steps such as controlling the humidity and operat-
ing the fluid bed within the normal operating range.
Because harmonization—a process known to skilled
artisans—would produce the optimal dew points, the
specification need not disclose them to enable skilled
artisans to practice the best mode. The disclosure is
adequate without them.
    Mylan and Par argue that, because the dew points
materially affect the claimed invention, express disclosure
in the specification was required. For this proposition,
they cite Bayer, 301 F.3d at 1312. Mylan and Par mis-
read Bayer. There, we held that, to prove inadequate
disclosure of the best mode, an accused infringer must
prove that the undisclosed information affects the proper-
ties of the claimed invention. Id. at 1319. The panel also
held that an accused infringer may prove a best mode
disclosure violation if the undisclosed subject matter
materially affects the properties of the claimed invention,
even if the undisclosed subject matter is not strictly
within the bounds of the patent claims. Id. at 1316.
Bayer created an exception to the general rule that “the
best mode disclosure requirement only refers to the
invention defined by the claims.” Id. at 1315–16. Bayer is
45                                         EURAND   v. MYLAN


inapposite here because there is no dispute that the dew
points are within the bounds of the asserted claims: The
claims cover a particular dissolution profile, and dew
point affects dissolution. The only issue here is whether
the disclosure is adequate to enable a person of ordinary
skill in the art to practice the invention incorporating the
optimal dew points. Mylan and Par cannot avoid that
issue merely by claiming that the dew points are material
to the claimed invention.
    Invalidation as a result of a best mode disclosure vio-
lation requires proof by clear and convincing evidence.
Teleflex, 299 F.3d at 1330. Mylan and Par cannot meet
that burden because the record indicates that skilled
artisans could readily obtain the optimal dew points using
a common fluid bed. We find, therefore, that the district
court did not err in rejecting Mylan and Par’s best mode
defense.
                            V.
    We address next Mylan’s appeal in Case No. 2011-
1399. Mylan appeals from the district court’s order
entering an injunction against launch of its generic ver-
sion of Amrix. Mylan argues that it is virtually always
improper to enjoin a prevailing party from acting in a
manner authorized by a district court’s own judgment;
that it is particularly inappropriate to enter an injunction
pending appeal against a prevailing generic in an ANDA
action; and that, even if such an injunction is permissible
in the abstract, the district court abused its discretion
when it entered an injunction in this case. Mylan con-
tends that it is entitled to recapture damages, capped by
the amount of the bond imposed, regardless of the out-
come on appeal.
    Given our ruling today, Mylan is no longer a prevail-
ing party or a prevailing generic, however. We have
EURAND   v. MYLAN                                         46


reversed the judgment of invalidity upon which Mylan
predicates its objections in this appeal. If our resolution
of the appeal in Case No. 2011-1409 resulted in an order
directing judgment in favor of Cephalon and a permanent
injunction, Mylan’s own appeal would certainly be moot.
See Grupo Mexicano de Desarrollo, S.A. v. Alliance Bond
Fund, Inc., 527 U.S. 308, 314 (1998). In Grupo Mexicano
de Desarrollo, the Supreme Court explained:
         [I]f [a plaintiff’s] lawsuit turns out to be
         meritorious—if he is found to be entitled
         to the permanent injunction that he
         seeks—even if the preliminary injunction
         was wrongly issued (because at that stage
         of the litigation the plaintiff’s prospects of
         winning were not sufficiently clear, or the
         plaintiff was not suffering irreparable in-
         jury) its issuance would in any event be
         harmless error. The final injunction es-
         tablishes that the defendant should not
         have been engaging in the conduct that
         was enjoined.
Id. at 314–15. See also Global NAPs, Inc. v. Verizon New
England, Inc., 489 F.3d 13, 22 (1st Cir. 2007) (“[A] party
is wrongfully enjoined when it had a right all along to do
what it was enjoined from doing.“); Blumenthal v. Merrill
Lynch, Pierce, Fenner & Smith, Inc., 910 F.2d 1049, 1054
(2d Cir. 1990) (“A party has been ‘wrongfully enjoined’ . . .
if it is ultimately found that the enjoined party had at all
times the right to do the enjoined act.”) Thus, if Mylan
was simply enjoined from engaging in conduct in which it
had no right to engage, Mylan’s complaints about that
injunction become meaningless. This simple principle
may or may not ultimately apply in this case, however. It
is unclear at this stage what the ultimate resolution of
this matter will be and whether launch of Mylan’s generic
47                                        EURAND   v. MYLAN


will be deemed unauthorized. See, e.g., Grupo Mexicano
de Desarrollo, 527 U.S. at 314–15 (indicating that where a
permanent injunction either does not ultimately issue or
is narrower in scope than a preliminary injunction, a
claim against the bond could lie).
    Here, it is unclear whether a final judgment against
Mylan will be entered and, if so, what the scope of an
injunctive remedy, if any, might be. There is much litiga-
tion that is yet to occur—both as to Cephalon’s claims for
relief and as to Mylan’s currently stayed counterclaims.
For these reasons, we find it premature to address My-
lan’s claim on the appeal bond or to resolve the questions
Mylan poses regarding the circumstances under which, or
the standards by which, an injunction pending appeal
may be imposed on a prevailing party in an ANDA action.
We dismiss Mylan’s appeal without prejudice to reassert a
claim for damages against the appeal bond if and when
such a claim might be ripe and appropriate. In the in-
terim, the appeal bond will remain in place unless the
parties stipulate to its release.
                           VI.
    On a final matter, we note that, because Mylan’s pat-
ent misuse and antitrust claims remained unresolved at
the time of appeal, the parties did not appeal from a final
judgment, which normally precludes an appellate court
from exercising jurisdiction. See Fed. R. Civ. P. 54. After
the appeals were filed, the parties moved the district
court for entry of a certificate pursuant to Rule 54(b) of
the Federal Rules of Civil Procedure, which would allow
the disposed issues to be immediately appealed. The
district court granted the motion and entered the Rule
54(b) certificate. We have permitted parties to establish
appellate jurisdiction with a nunc-pro-tunc Rule 54(b)
certificate. Storage Tech. Corp. v. Cisco Sys., Inc., 329
EURAND   v. MYLAN                                            48


F.3d 823, 829–30 (Fed. Cir. 2003); State Contracting &
Eng’g Corp. v. Fla., 258 F.3d 1329, 1334–35 (Fed. Cir.
2001). While the parties should have moved for entry of a
Rule 54(b) certificate before filing their appeals, the late-
filed certificate is sufficient to establish appellate jurisdic-
tion under our precedent.
                             VII.
    We reverse and vacate the district court’s invalidity
judgment and affirm its best mode ruling. We dismiss as
premature Mylan’s appeal from the district court’s entry
of the injunction. To allow the district court an opportu-
nity to assess the propriety of a preliminary injunction
pending further proceedings, the injunction will remain in
place for forty-five days post-mandate, or until further
order of the district court, whichever occurs sooner.
    AFFIRMED IN PART, REVERSED IN PART,
     VACATED IN PART, DISMISSED IN PART
