       NOTE: This disposition is nonprecedential.

  United States Court of Appeals
      for the Federal Circuit
              __________________________

      DURAMED PHARMACEUTICALS, INC.,
              Plaintiff-Appellee,
                           v.
          WATSON LABORATORIES, INC.,
               Defendant-Appellant.
              __________________________

                      2010-1331
              __________________________

    Appeal from the United States District Court for the
District of Nevada in Case No. 08-CV-0116, Judge Larry
R. Hicks.
              ____________________________

               Decided: March 25, 2011
             ____________________________

    ALEXANDER F. MACKINNON, Kirkland & Ellis LLP, of
Los Angeles, California, argued for plaintiff-appellee.
With him on the brief was ROBERT G. KRUPKA. Of counsel
on the brief were CHARANJIT BRAHMA, COREY J. MANLEY
and J. JOHN LEE, of Washington, DC.

   MARK T. JANSEN, Kilpatrick Townsend and Stockton
LLP, of San Francisco, California, argued for defendant-
appellant. With him on the brief were NANCY L.
DURAMED PHARMA   v. WATSON LABS                          2


TOMPKINS; KENNETH E. JENKINS, of San Diego, Califor-
nia; CEDRIC C.Y. TAN and KRISTIN M. COOKLIN, of Wash-
ington, DC.
              __________________________

     Before LOURIE, LINN, and DYK, Circuit Judges.
LOURIE, Circuit Judge.
    Watson Laboratories, Inc. (“Watson”) appeals from
the decision of the United States District Court for the
District of Nevada, holding on summary judgment that
the asserted claims of U.S. Patent 7,320,969 (“the ’969
patent”) were not invalid for obviousness. Duramed
Pharms., Inc. v. Watson Labs., Inc., 701 F. Supp. 2d 1163,
1167-71 (D. Nev. 2010). Watson also appeals the district
court’s exclusion of its expert’s testimony on prior use of
the claimed invention. Id. at 1166-67. Because the
district court erred in its determination of nonobvious-
ness, but did not abuse its discretion in excluding certain
expert testimony, we reverse in part, affirm in part, and
remand.
                      BACKGROUND
     Duramed Pharmaceuticals, Inc. (“Duramed”) owns the
’969 patent, which covers an extended-cycle combined oral
contraceptive (“COC”) regimen commercialized by
Duramed as Seasonique®. Unlike traditional 28-day COC
regimens, in which estrogen- and progestin-containing
pills are administered for 21 days and hormone-free pills
for 7 days, extended-cycle regimens increase the men-
strual cycle’s natural length by administering hormone-
containing pills for greater than 21 days. Extended-cycle
regimens thus postpone estrogen-withdrawal symptoms
experienced by many women during the hormone-free
period. The incidence of estrogen-withdrawal symptoms
can also be reduced by administering low dosages of
3                          DURAMED PHARMA    v. WATSON LABS


estrogen during the traditional hormone-free period.
Duramed’s Seasonique® combines an extended-cycle COC
regimen with the administration of low-dose, unopposed
estrogen during the hormone-free period. Specifically, the
regimen consists of 84 daily pills containing 30 μg of the
estrogen ethinyl estradiol and 150 μg of the progestin
levonorgestrel, followed by 7 daily pills containing 10 μg
of ethinyl estradiol only.
    On March 6, 2008, Duramed brought suit against
Watson under 35 U.S.C. § 271(e)(2) after Watson filed an
Abbreviated New Drug Application (“ANDA”) seeking
Food and Drug Administration (“FDA”) approval for a
generic version of Seasonique®. Duramed alleged in-
fringement of claims 1-9, 15, and 17-19 of the ’969 patent.
Claim 19 is representative:
    19. A method of contraception in a female in need
    thereof the method comprising administering to
    the female a dosage comprising a combination of
    estrogen and progestin for a period of 84 consecu-
    tive days, followed by administration of a dosage
    consisting essentially of estrogen for a period of 7
    consecutive days,
        wherein the estrogen that is administered
           in combination with progestin for the
           period of 84 consecutive days is orally
           administered monophasicly in a daily
           amount of about 30 μg of ethinyl estra-
           diol,
        the estrogen that is administered for the
           period of 7 consecutive days is orally
           administered monophasicly in a daily
           amount of about 10 μg of ethinyl estra-
           diol, and
        the progestin that is administered in com-
            bination with estrogen for the period
DURAMED PHARMA   v. WATSON LABS                           4


            of 84 consecutive days is orally admin-
            istered monophasicly in a daily
            amount      of   about     150 μg    of
            levonorgestrel.
’969 patent claim 19. The ’969 patent issued on January
22, 2008, and claims priority back to an application filed
on December 5, 2001.
     Watson stipulated to infringement but challenged the
’969 patent’s validity under 35 U.S.C. § 103. In making
its obviousness challenge, Watson relied on, inter alia, (1)
a 1994 Kovacs article, which describes an extended-cycle
COC regimen of 84 daily pills containing 30 μg ethinyl
estradiol and 150 μg levonorgestrel, followed by 7 daily
hormone-free pills; (2) U.S. Patent 6,027,749 (“the ’749
patent”), which discloses COC regimens of up to 77 daily
pills containing 15-20 μg ethinyl estradiol and 50-125 μg
levonorgestrel, followed by 7 daily pills containing 10-15
μg ethinyl estradiol to reduce the incidence of premen-
strual headaches; and (3) two Sulak articles from 1997
and 2000, which describe the problem of headaches re-
sulting from estrogen withdrawal as well as the use of
low-dose, estrogen-only pills during the hormone-free
period as a way to alleviate such headaches.
    Watson’s expert witness, Dr. Michael A. Thomas,
opined on the teachings of these prior art references. He
also opined that one of skill in the art would have been
motivated to combine the Kovacs COC regimen with the 7
days of unopposed estrogen as claimed in the ’969 patent
because the Kovacs article recognized that the regimen
may result in headaches in some women. J.A. 824-25. In
addition, Dr. Thomas testified that he had personally
prescribed the contraceptive regimen claimed in the ’969
patent prior to the patent’s priority date, December 5,
2001. The district court granted Duramed’s motion to
5                          DURAMED PHARMA    v. WATSON LABS


exclude Thomas’s testimony regarding this prior use as
uncorroborated. Duramed, 701 F. Supp. 2d at 1166-67.
    The district court also granted summary judgment of
nonobviousness. The court analyzed Watson’s “three most
significant” prior art references, the Kovacs article, the
Sulak article, 1 and the ’749 patent, finding the remaining
art “cumulative.” Id. at 1168 n.3. Regarding the Kovacs
article, the court found that it did not provide support for
combining 84 daily hormone pills with 7 days of unop-
posed estrogen to alleviate estrogen-withdrawal symp-
toms because it describes headaches throughout the
menstrual cycle and fails to make any mention of using
unopposed estrogen. Id. at 1168-69. Regarding the Sulak
articles, the court found that, although they identify
headaches as a symptom of hormone withdrawal, they
mention the addition of unopposed estrogen only as a
theoretical, untested solution. Id. at 1169-70. Regarding
the ’749 patent, the court found that by disclosing a
variety of COC regimens, the patent did not establish
consistent knowledge in the community, and that it
provided no basis for adding estrogen-only pills to the end
of a COC regimen to alleviate withdrawal headaches. Id.
at 1170. Finally, the court found that Watson’s expert,
Thomas, was not a person of ordinary skill in the art, but
rather an active participant in research in the field of
endocrinology. Id.
    Watson appealed. We have jurisdiction pursuant to
28 U.S.C. § 1295(a)(1).




    1   The district court cites the 1997 Sulak article, but
it appears to have relied on a combination of the 1997 and
2000 Sulak articles. Accordingly, we refer to these arti-
cles together as the Sulak articles.
DURAMED PHARMA   v. WATSON LABS                           6


                       DISCUSSION
    This court reviews a district court’s decision on sum-
mary judgment de novo, reapplying the same standard
applied by the district court. Iovate Health Scis., Inc. v.
Bio-Engineered Supplements & Nutrition, Inc., 586 F.3d
1376, 1380 (Fed. Cir. 2009). Summary judgment is ap-
propriate only “if the movant shows that there is no
genuine dispute as to any material fact and the movant is
entitled to judgment as a matter of law.” Fed. R. Civ. P.
56(a). In deciding a motion for summary judgment, “[t]he
evidence of the non-movant is to be believed, and all
justifiable inferences are to be drawn in his favor.”
Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 255 (1986).
     “[A] moving party seeking to have a patent held not
invalid at summary judgment must show that the non-
moving party, who bears the burden of proof at trial,
failed to produce clear and convincing evidence on an
essential element of a defense upon which a reasonable
jury could invalidate the patent.” Eli Lilly & Co. v. Barr
Labs., Inc., 251 F.3d 955, 962 (Fed. Cir. 2001). To defeat
summary judgment, the nonmoving party must then come
forward with evidence sufficient to establish a genuine
issue of material fact regarding that essential element.
Freedman Seating Co. v. Am. Seating Co., 420 F.3d 1350,
1363 (Fed. Cir. 2005).
                      I. Obviousness
    Under the Patent Act, “[a] patent may not be ob-
tained . . . 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). Although the ultimate determination
of obviousness under § 103 is a question of law, it is based
7                          DURAMED PHARMA    v. WATSON LABS


on several underlying factual findings, including (1) the
scope and content of the prior art; (2) the level of ordinary
skill in the pertinent art; (3) the differences between the
claimed invention and the prior art; and (4) evidence of
secondary factors, such as commercial success, long-felt
need, and the failure of others. Graham v. John Deere
Co., 383 U.S. 1, 17-18 (1966).
    An invention “composed of several elements is not
proved obvious merely by demonstrating that each of its
elements was, independently, known in the prior art.”
KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418 (2007).
Rather, “it can be important to identify a reason that
would have prompted a person of ordinary skill in the
relevant field to combine the elements in the way the
claimed new invention does,” id., although such a reason
need not be explicitly stated in the prior art, see id. at
419. Furthermore, when there exists a finite number of
identified, predictable solutions to a known problem, a
combination that results in “anticipated success” is likely
the product not of innovation, but of ordinary skill and
common sense. Id. at 421.
    Watson argues that it raised genuine issues of mate-
rial fact regarding whether it would have been obvious to
combine the Kovacs COC regimen with the administra-
tion of low-dose estrogen during the traditional hormone-
free period to treat estrogen-withdrawal headaches in
light of, inter alia, the Sulak articles and the ’749 patent.
Watson claims that the court, in granting summary
judgment of nonobviousness, erred by, inter alia, (1)
focusing on individual references instead of considering
the teaching of the prior art as a whole; (2) improperly
requiring clear and convincing evidence of invalidity on
summary judgment; (3) ignoring all but three prior art
references, including the 2000 Sulak article, as cumula-
tive; (4) erroneously requiring that the prior art teach a
DURAMED PHARMA    v. WATSON LABS                           8


virtual guarantee, rather than a reasonable expectation,
of success; and (5) failing to make a finding of the level of
skill in the art.
    Duramed responds that the district court correctly
granted summary judgment of nonobviousness because
Watson failed to present any evidence of a reason to
combine Kovacs with 7 days of low-dose, unopposed
estrogen to reduce the incidence of estrogen-withdrawal
headache during the traditional hormone-free period.
According to Duramed, by disclosing that headaches
occurred throughout the menstrual cycle, the Kovacs
article fails to suggest that the Kovacs regimen caused
the headaches because of estrogen withdrawal. Rather,
Duramed continues, the art taught that extended-cycle
regimens were a cure for—not a cause of—such head-
aches, including the 2000 Sulak article, which discusses
extended-cycle regimens and unopposed estrogen as
alternative solutions to the problem of withdrawal head-
aches in traditional 28-day COC regimens. Regarding the
’749 patent, Duramed claims that it also does not provide
a motivation to modify Kovacs with unopposed estrogen
because it does not associate estrogen-withdrawal head-
aches with any particular extended-cycle regime, let alone
the extended-cycle Kovacs regimen. Finally, Duramed
dismisses Watson’s expert testimony as conclusory and
thus insufficient to raise a genuine issue of fact.
    Duramed also disagrees that the district court made
any of the errors alleged by Watson. Rather, according to
Duramed, the district court (1) correctly held Watson to
the clear and convincing evidentiary standard on sum-
mary judgment; (2) implicitly made a finding on the level
of skill in the art in Watson’s favor; (3) correctly analyzed
only three prior art references, rejecting the rest as cumu-
lative; and (4) properly required Watson to show, not
absolute certainty, but a reasonable expectation that
9                           DURAMED PHARMA    v. WATSON LABS


combining Kovacs with unopposed estrogen would succeed
in reducing the incidence of estrogen-withdrawal head-
aches.
    We agree with Watson that the district court erred in
its obviousness analysis and, as a result, incorrectly
granted summary judgment of nonobviousness. Specifi-
cally, the district court erred in assessing the content and
scope of the prior art, leading it to incorrectly analyze
each prior art reference in isolation without considering
the prior arts’ teaching as a whole in light of the creativity
and common sense of a person of ordinary skill. The court
also appears to have applied an incorrect evidentiary
standard on summary judgment. Finally, the court failed
to make any finding on the level of skill in the art. We
address each in turn.
          A. Content and Scope of the Prior Art
    The district court erred in several of its findings on
the disclosure of the Sulak articles and the ’749 patent,
which then infected the court’s summary judgment deci-
sion. Regarding Sulak, the court rejected all considera-
tion of the articles’ teaching of the use of unopposed
estrogen because that use was mentioned only as a “theo-
retical,” rather than a tested, solution to estrogen-
withdrawal headaches. Duramed, 701 F. Supp. 2d at
1169. A reference, however, is prior art for all that it
discloses, and there is no requirement that a teaching in
the prior art be scientifically tested, see PharmaStem
Therapeutics, Inc. v. ViaCell, Inc., 491 F.3d 1342, 1363-64
(Fed. Cir. 2007), or even guarantee success, see Alza Corp.
v. Mylan Labs., Inc., 464 F.3d 1286, 1295 (Fed. Cir. 2006),
before providing a reason to combine. Rather, it is suffi-
cient that one of ordinary skill in the art would perceive
from the prior art a reasonable likelihood of success. Id.
DURAMED PHARMA    v. WATSON LABS                          10


    Regarding the ’749 patent, the district court first
found that the patent “provides no reference or basis to a
practitioner on the effects of adding unopposed estrogen
to the end of an extended regimen in regards to hormone
withdrawal headaches.” Duramed, 701 F. Supp. 2d at
1170. The ’749 patent, however, expressly teaches the
administration of 7 days of 10 μg ethinyl estradiol during
the traditional hormone-free period following a variety of
extended-cycle COC regimens. ’749 patent col.9 ll.48-52.
Moreover, it teaches that the administration of unopposed
estrogen is to reduce the “incidence of side effects, such as
headaches within the framework of premenstrual syn-
drome.” Id. The district court also found that the ’749
patent discloses a variety of COC regimens and thus
concluded that the patent “does not teach any one specific
combination that would establish consistent knowledge in
the community.” Duramed, 701 F. Supp. 2d at 1170.
However, the question is not whether there existed a
consistent COC regimen in the art, but rather whether
one of ordinary skill in the art would have been motivated
to combine the Kovacs regimen with 7 days of low-dose,
unopposed estrogen with the reasonable expectation that
the addition of low-dose estrogen would successfully
reduce the incidence of estrogen-withdrawal headaches
during the hormone-free period.
    Based on its errors in assessing the content of these
prior art references, the district court improperly ana-
lyzed and rejected the teaching of each in isolation, con-
cluding that each alone failed to establish by clear and
convincing evidence a motivation to combine. Specifically,
while recognizing that the Sulak articles identify head-
aches as a symptom of hormone withdrawal, the court
ignored the articles’ suggestion of unopposed estrogen as
a possible solution, concluding instead that, because it
remained an untested solution, “the Sulak article does not
11                         DURAMED PHARMA    v. WATSON LABS


show by clear and convincing evidence that a person of
ordinary skill would have added unopposed estrogen to
the traditional hormone-free interval to alleviate the
hormone withdrawal symptoms that arise during that
period.” Id. at 1169-70. The district court next, as de-
scribed above, rejected the disclosure of the ’749 patent in
its entirety, and thus failed to address its teaching of the
use of unopposed estrogen to treat headaches following
various extended-cycle COC regimens in light of the
teaching of a specific extended-cycle COC regimen in
Kovacs. Id. at 1170. Finally, the district court analyzed
the Kovacs article without reference to the ’749 patent or
the Sulak articles, concluding that because the article
taught that women on the regimen reported headaches
“scattered throughout the [menstrual] cycle,” and itself
did not mention the use of unopposed estrogen, “the
[Kovacs] article does not provide clear and convincing
support” that a practitioner would treat headaches asso-
ciated with the regimen by adding unopposed estrogen.
Id. at 1169. Accordingly, the district court failed to prop-
erly consider the collective teaching of the prior art in
light of the common sense and creativity of the person of
ordinary skill in the art. See KSR, 550 U.S. at 419-21.
    The district court also appears to have applied an in-
correct evidentiary standard on summary judgment,
incorrectly placing the burden of proof on the nonmoving
party, Watson, to show clear and convincing evidence of
invalidity as a matter of law. In this case, Duramed
moved for summary judgment of nonobviousness, and
thus the burden rested with Duramed to show that Wat-
son had failed to come forth with clear and convincing
evidence of an essential element of its prima facie case of
obviousness. See Eli Lilly, 251 F.3d at 962. Although the
ultimate evidentiary burden of showing clear and convinc-
ing evidence does not change on summary judgment,
DURAMED PHARMA    v. WATSON LABS                          12


Watson could defeat summary judgment by showing a
genuine issue of material fact, which, if believed by the
finder of fact, could provide clear and convincing evidence
of a motivation to combine the prior art references. See
Freedman Seating, 420 F.3d at 1364; see also Monarch
Knitting Mach. Corp. v. Sulzer Morat GmbH, 139 F.3d
877, 881 (Fed. Cir. 1998) (“If facts remain in dispute, this
court weighs the materiality of the dispute, i.e., whether
resolution of the dispute one way or the other makes a
difference to the final determination of obviousness.”).
That is the standard the district court should have made
clear it was applying on summary judgment.
                B. Level of Skill in the Art
    A determination of obviousness requires a factual
finding of the level of ordinary skill in the pertinent art,
35 U.S.C. § 103(a); Graham, 383 U.S. at 17, which the
district court failed to make in this case. When a finding
of the level of skill affects the court’s ultimate conclusion
under § 103, the failure to make such a finding consti-
tutes reversible error. See Kloster Speedsteel AB v. Cruci-
ble Inc., 793 F.2d 1565, 1574 (Fed. Cir. 1986), overruled
on other grounds by Knoff-Bremse Systeme v. Dana Corp.,
383 F.3d 1337 (Fed. Cir. 2004). The district court granted
summary judgment of nonobviousness based on an un-
specified level of skill, but a finding of a higher level of
skill could have altered this ruling because, in general, an
invention may be more obvious to one of higher skill than
it might have been to one of lower skill. See Union Car-
bide Corp. v. Am. Can Co., 724 F.2d 1567, 1573 (Fed. Cir.
1984).
    Watson argues that the level of skill was high, requir-
ing a medical degree and several years of experience in
the field of reproductive endocrinology. Duramed argued
below that even a nurse practitioner can be a person of
13                         DURAMED PHARMA    v. WATSON LABS


ordinary skill but suggests on appeal that the district
court implicitly sided with Watson. There is no evidence
for Duramed’s contention. Rather, the district court
appears to have simply rejected all of Watson’s expert’s
testimony by finding that Thomas was not a person of
ordinary skill, but extraordinary skill. 2 See Duramed,
701 F. Supp. 2d at 1170. That was error. Since a deter-
mination of obviousness is made from the vantage point of
a legal construct, a hypothetical person having ordinary
skill in the pertinent art, In re Rouffet, 149 F.3d 1350,
1357 (Fed. Cir. 1998), a person of extraordinary skill may
opine on the knowledge of this hypothetical person, see
Moore v. Wesbar Corp., 701 F.2d 1247, 1253 (7th Cir.
1983) (holding that an expert of “more than the ‘ordinary
skill’ required by the statute” was “well suited to assist
the court in deciding what would be obvious to such a
person”). Accordingly, Thomas’s credentials as a tenured
professor who actively participates in endocrinology
research do not disqualify him from opining on what an
ordinary person of lesser skill, whether a medical doctor
with less research experience or a nurse practitioner,
would have understood from the prior art.
    Finally, contrary to Duramed’s claim, Thomas’s expert
testimony was not merely conclusory. He connected each
claim limitation with disclosures in the prior art, and his
opinion on a motivation to combine rests on factual sup-
port in the record. J.A. 823-26, 836-38; cf. Perfect Web
Techs., Inc. v. InfoUSA, Inc., 587 F.3d 1324, 1331 (Fed.
Cir. 2009) (holding expert testimony insufficient to raise a
genuine issue of fact when it relied on irrelevant prior art

     2  The district court limited its discussion to the tes-
timony of Thomas’s prior use of the claimed extended-
cycle COC regimen. Accordingly, it is unclear from the
opinion whether or not the court credited other aspects of
Thomas’s testimony.
DURAMED PHARMA   v. WATSON LABS                        14


and failed entirely to address one claim limitation).
Accordingly, this testimony should not have been disre-
garded on summary judgment. See KSR, 550 U.S. at 427
(“In considering summary judgment on th[e] question [of
obviousness] the district court can and should take into
account expert testimony, which may resolve or keep open
certain questions of fact.”).
    In light of the errors made by the district court, we
reverse the district court’s grant of summary judgment of
nonobviousness and remand. We note, however, that in
reviewing the record de novo on summary judgment and
crediting Duramed’s lower level of skill in the art, the
district court on remand may well conclude that the
claimed extended-cycle COC regimen would have been
obvious as a matter of law.
     Kovacs teaches the claimed administration of 84 daily
pills containing 150 μg levonorgestrel and 30 μg ethinyl
estradiol. The ’749 patent teaches the claimed admini-
stration of 10 μg ethinyl estradiol for 7 days during the
traditional hormone-free period. Moreover, this admini-
stration follows a variety of extended-cycle COC regimens
to treat estrogen-withdrawal headaches, which the 2000
Sulak article confirms for traditional 28-day COC regi-
mens are “more common during the hormone-free inter-
vals compared with the active-pill weeks.” J.A. 1240-41.
The 1997 Sulak article also teaches that women on ex-
tended-cycle COC regimens experience headaches during
the hormone-free period. 3 J.A. 1225. And Watson’s


   3    Watson stated at oral argument that the 1997 Su-
lak article tested the Kovacs regimen. Oral Arg. at 5:00-
5:30. The article does list Kovacs in Table 1 as one prior
art regimen, but it does not state that the women in its
study were on the Kovacs regimen. Moreover, many of
the women in the study did not stabilize on a regimen of
15                         DURAMED PHARMA    v. WATSON LABS


expert opined that one of skill in the art would have been
motivated to combine the Kovacs COC regimen with the 7
days of unopposed estrogen taught by the ’749 patent and
the Sulak articles to arrive at the claimed invention
because the Kovacs article recognized that the regimen
resulted in headaches in some women, J.A. 824-25, al-
though “scattered throughout the [menstrual] cycle,” J.A.
229.
    Thus, on the record before us, there appear to be no
genuine issues of material fact that, based on the teaching
of Kovacs, the ’749 patent, and the Sulak articles, one of
ordinary skill would have been motivated to combine the
Kovacs regimen and 7 days of 10 μg unopposed ethinyl
estradiol with a reasonable expectation that the combina-
tion would reduce the incidence of headaches associated
with that regimen. Yet, Watson did not move for sum-
mary judgment of obviousness and stated at oral argu-
ment that it was “absolutely not” requesting that this
court hold the asserted claims obvious as a matter of law.
Oral Arg. at 1:12-1:43. In light of this procedural posture,
Duramed did not have an opportunity to challenge Wat-
son’s prima facie case of obviousness or introduce any
secondary considerations of nonobviousness. Accordingly,
we leave that determination to the district court on re-
mand.
                II. Exclusion of Testimony
    A decision to exclude evidence raises an issue not
unique to patent law, and thus we apply the law of the
regional circuit in which the district court sits, in this
case, the Ninth Circuit. Juicy Whip, Inc. v. Orange Bang,
Inc., 382 F.3d 1367, 1370 (Fed. Cir. 2004). A district
court’s decision to exclude evidence is reviewed for abuse

84 days of hormone-containing pills as claimed in the ’969
patent. J.A. 1225
DURAMED PHARMA   v. WATSON LABS                          16


of discretion. United States v. Pang, 362 F.3d 1187, 1194
(9th Cir. 2004).
    The district court excluded Thomas’s testimony re-
garding his prior use of the claimed invention as uncor-
roborated in light of the “general rule” that “corroboration
of oral testimony regarding prior invention or use is
required before the evidence is admissible.” Duramed,
701 F. Supp. 2d at 1166-67 (citing Texas Digital Sys., Inc.
v. Telegenix, Inc., 308 F.3d 1193, 1217 (Fed. Cir. 2002),
and Woodland Trust v. Flowertree Nursery, Inc., 148 F.3d
1368, 1371 (Fed. Cir. 1998)). Watson does not argue that
the testimony on prior use was in fact corroborated, but
rather argues that because Thomas’s testimony was not
the sole evidence of obviousness, it should not have been
excluded. Watson claims that although uncorroborated
oral testimony alone is insufficient to meet the clear and
convincing standard for invalidity, it may contribute to
the clear and convincing evidence standard when not the
sole evidence of invalidity.
    Yet, Watson acknowledged that it was not relying on
this testimony to support either its opposition to summary
judgment or its prima facie case of obviousness. Oral Arg.
at 22:25-23:35. We therefore decline to decide to what
degree such evidence may or may not contribute to a
determination of obviousness by clear and convincing
evidence, concluding instead that Watson failed to meet
its “particularly high hurdle” to demonstrate that the
district court abused its discretion in excluding testimony
on prior use. Texas Digital, 308 F.3d at 1218.
17                        DURAMED PHARMA   v. WATSON LABS


                        CONCLUSION
     For the foregoing reasons, we reverse the district
court’s grant of summary judgment of nonobviousness,
affirm the court’s exclusion of Watson’s expert testimony
on prior use, and remand for further proceedings consis-
tent with this opinion.
  REVERSED IN PART, AFFIRMED IN PART, and
                REMANDED
                          COSTS
     Costs to Watson.
