  United States Court of Appeals
      for the Federal Circuit
                ______________________

IMPAX LABORATORIES INC., ASTRAZENECA AB,
        ASTRAZENECA UK LIMITED,
             Plaintiffs-Appellees

                           v.

LANNETT HOLDINGS INC., LANNETT COMPANY
                  INC.,
           Defendants-Appellants
          ______________________

                      2017-2020
                ______________________

    Appeal from the United States District Court for the
District of Delaware in Nos. 1:14-cv-00984-RGA, 1:14-cv-
00999-RGA, Judge Richard G. Andrews.
                 ______________________

                Decided: June 28, 2018
                ______________________

   JAMES F. HURST, Kirkland & Ellis LLP, Chicago, IL,
argued for plaintiffs-appellees. Also represented by
MARCUS EDWARD SERNEL.

    JOSEPH F. POSILLICO, Fox Rothschild, LLP, Philadel-
phia, PA, argued for defendants-appellants. Also repre-
sented by FRANK T. CARROLL; MICHAEL W. GLYNN, New
York, NY.
                ______________________
2                 IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



    Before LOURIE, DYK, and TARANTO, Circuit Judges.
LOURIE, Circuit Judge.
    Lannett Holdings Inc. and Lannett Co. Inc. (together,
“Lannett”) appeal from the decision of the United States
District Court for the District of Delaware concluding,
after a bench trial, that claims 4, 11, 12, and 14 of U.S.
Patent 6,760,237 (“the ’237 patent”) and claims 6 and 14–
16 of U.S. Patent 7,220,767 (“the ’767 patent”) were not
shown to be invalid, see Impax Labs., Inc. v. Lannett
Holdings Inc., 246 F. Supp. 3d 1024 (D. Del. 2017) (“Opin-
ion”), entering judgment in favor of Impax Laboratories
Inc. (“Impax”), AstraZeneca AB, and AstraZeneca UK
Limited (together, “AstraZeneca”), and entering an in-
junction against Lannett pursuant to 35 U.S.C.
§ 271(e)(4), see Impax Labs. Inc. v. Lannett Holdings Inc.,
No. 1:14-cv-00984-RGA (D. Del. Apr. 17, 2017), ECF No.
174; J.A. 1–4. For the reasons that follow, we affirm.
                       BACKGROUND
     Triptans are selective serotonin receptor agonists, de-
veloped in the early 1980s. The first triptan to be mar-
keted was sumatriptan under the name Imitrex®, which
first became available in the U.S. in an injection form in
1993. In 1995, sumatriptan became available in an oral
tablet form and later, in 1997, in an intranasal form as
Imitrex® (sumatriptan) Nasal Spray (“NS”). Zolmitriptan
is another triptan, which first became available in the
U.S. in an oral tablet form in 1999 under the name
Zomig®. At that time, there were several other triptans
that were either on the market or under development.
    AstraZeneca owns and Impax is the exclusive licensee
of the ’237 and ’767 patents, 1 which relate to formulations



    1  At the district court, Lannett alleged lack of
standing and ownership issues regarding the ’237 and
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.                 3



of zolmitriptan for intranasal administration. The claims
at issue in this appeal are directed to pharmaceutical
formulations, intranasal administration devices, or aque-
ous solutions, of zolmitriptan. ’237 patent col. 5 l. 4–col. 6
l. 22; ’767 patent col. 5 l. 8–col. 6 l. 25.
    Claim 4 of the ’237 patent depends from claim 2,
which in turn, depends from claim 1. Claims 1, 2, and 4
of the ’237 patent read as follows:
    1. A pharmaceutical formulation suitable for in-
    tranasal     administration    which    comprises
    zolmitriptan and a pharmaceutically acceptable
    carrier wherein the pH of the formulation is in the
    range 4.5 to 5.5.
    2. A pharmaceutical formulation according to
    claim 1 wherein the pH of the formulation is 5.
    4. A pharmaceutical formulation according to
    claim 2 wherein the formulation is buffered.
’237 patent col. 5 ll. 4–9, 12–13.
    Similarly, claims 6 and 15 of the ’767 patent read:
    6. A pharmaceutical formulation suitable for in-
    tranasal    administration     which    comprises
    zolmitriptan and a pharmaceutically acceptable
    carrier wherein the pH of the formulation is in the
    range 3.5 to 5.5, wherein the formulation is buff-
    ered by a mixture of citric acid and disodium
    phosphate.




’767 patents among different AstraZeneca entities and
their effect on the licensing agreement between Impax
and AstraZeneca. Opinion, 246 F. Supp. 3d at 1028–30.
However, Lannett no longer challenges standing on
appeal.
4                   IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



    15. An aqueous solution of zolmitriptan in a buffer
    at a pH of less than 6.0.
’767 patent col. 5 ll. 23–27, col. 6 ll. 21–22.
     Other formulation claims of the ’237 and ’767 patents
at issue include similar limitations with regard to pH
ranges and buffering, and some formulation claims in-
clude additional limitations relating to sterility. ’237
patent col. 5 l. 4–col. 6 l. 22; ’767 patent col. 5 l. 8–col. 6
l. 25. These additional limitations are not at issue on
appeal.
    AstraZeneca owns the New Drug Application (“NDA”)
for Zomig® (zolmitriptan) Nasal Spray, 2.5 mg/spray and
5 mg/spray, approved by the U.S. Food and Drug Admin-
istration (“FDA”) for treatment of migraine. The ’237 and
’767 patents are listed in connection with Zomig® Nasal
Spray in the FDA’s Approved Drug Products with Thera-
peutic Equivalence Evaluations, commonly known as the
“Orange Book.”
    In 2012, AstraZeneca and Impax entered into an
agreement for distribution, license, development, and
supply of the Zomig® products. The agreement granted to
Impax an exclusive license to AstraZeneca’s patents
covering the Zomig® products, including the ’237 and ’767
patents, in return for the payment of $130 million and
additional payments at varying royalty rates, including
40% on the nasal spray. Opinion, 246 F. Supp. 3d at
1039; J.A. 2204–05.
    In June 2014, Lannett notified AstraZeneca that it
had filed an Abbreviated New Drug Application
(“ANDA”), seeking approval for a generic version of
Zomig® Nasal Spray, making a certification according to
21 U.S.C. § 355(j)(2)(A)(vii)(IV) (“Paragraph IV certifica-
tion”), alleging noninfringement and/or invalidity of the
’237 and ’767 patents.
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.               5



    In July 2014, Appellees filed suit against Lannett in
the District of Delaware for infringement of the ’237 and
’767 patents pursuant to 35 U.S.C. § 271(e)(2)(A). In
December 2015, the district court issued its claim con-
struction opinion and order. The court agreed with Appel-
lees that the preamble of “[a] pharmaceutical formulation
suitable for intranasal administration” is limiting. Impax
Labs. Inc. v. Lannett Holdings Inc., 2015 WL 7737309, at
*2–3 (D. Del. 2017) (“Claim Construction Opinion”); see
also Impax Labs. Inc. v. Lannett Holdings Inc., No. 1:14-
cv-00984-RGA (D. Del. Dec. 8, 2017), ECF No. 64 (“Claim
Construction Order”); J.A. 9–10. The court also adopted
Appellees’ construction of “zolmitriptan” as meaning its
chemical name and structure, declining to adopt Lannett’s
proposed construction that would include “ionic and
covalently bonded forms thereof that preserve the phar-
maceutical activity of the structure.” Claim Construction
Opinion, 2015 WL 7737309, at *3–4. The court, however,
agreed with Lannett regarding the construction of the
word “buffer,” adopting the “functional definition” pro-
posed by Lannett, id. at *4–7; J.A. 9, and adopted the
parties’ agreed-upon constructions of “disodium phos-
phate” and “pH of the formulation is 5,” J.A. 10.
    In September 2016, a four-day bench trial was held on
the issues of infringement and validity. Following the
bench trial, the parties stipulated that Lannett’s product
described in its ANDA with a target pH of 5, if approved
by the FDA, will infringe the ’237 and ’767 patents.
Impax Labs. Inc. v. Lannett Holdings Inc., No. 1:14-cv-
00984-RGA (D. Del. Sept. 29, 2016), ECF No. 137.
    In March 2017, the district court issued its decision on
validity, holding that Lannett failed to prove by clear and
convincing evidence that the asserted claims were invalid.
Opinion, 246 F. Supp. 3d at 1030. The court first made
factual findings on the teachings of the prior art refer-
ences, namely, sumatriptan NS, International Publication
No. WO 99/64044 (“Marquess”), U.S. Patent 6,326,401
6                  IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



and its counterpart French Publication No. FR 2773489
(together, “Chauveau”), 2 and Stewart Tepper & Alan
Rapoport, The Triptans: A Summary, 12(5) CNS Drugs
403–417 (Nov. 1999) (“Tepper & Rapoport”). Id. at 1032–
34.
    The district court then determined that Lannett failed
to prove that claim 4 of the ’237 patent and claim 15 of
the ’767 patent were anticipated by Marquess or
Chauveau, as neither of the references disclosed all the
limitations of the claims. Id. at 1034–35. The court also
determined that Lannett failed to prove by clear and
convincing evidence that the claims at issue would have
been obvious over the prior art. Id. at 1035–44. In reach-
ing the nonobviousness conclusion, the court found that:
(1) the prior art, including Chauveau, taught away from
formulating zolmitriptan for intranasal administration
because zolmitriptan was known to be active, not by itself,
but through its more potent metabolite, 183C91; (2) the
prior art at the time failed to teach that zolmitriptan by
itself, as contrasted with its metabolite, would have been
effective; and (3) a skilled artisan would not have been
motivated to make with a reasonable expectation of
success nasal formulations of zolmitriptan. Id. at 1036–
39; see also id. at 1032 n.3. The court also found that
sumatriptan does not have an active metabolite and that
“[o]nly two other triptans, eletriptan and almotriptan,
have active metabolites, but their metabolites ‘don’t really
contribute at all to the efficacy of those drugs.’ Zolmitrip-
tan stands alone in the class of triptans as having an
active, more potent metabolite.” Id. at 1033 (quoting
Appellees’ expert, Dr. Alan Rapoport) (citation omitted).



    2   As counterparts of each other, the two Chauveau
references’ disclosures are substantially identical. In this
opinion, references to Chauveau will be based on the U.S.
patent unless otherwise noted.
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.                7



    The district court also considered evidence of objective
indicia of nonobviousness. Id. at 1039–43. It found that
the 2012 agreement between Impax and AstraZeneca
supported a showing of nonobviousness, but found any
further secondary considerations evidence inconclusive.
Id. Ultimately, after noting that “[t]he question of obvi-
ousness is a close one,” the court determined that Lannett
had failed to meet its burden of proving invalidity by clear
and convincing evidence. Id. at 1043–44. Following the
decision on the issue of validity, the court entered final
judgment and an injunction in favor of Appellees. J.A. 1–
4.
   Lannett timely appealed. We have jurisdiction pur-
suant to 28 U.S.C. § 1295(a)(1).
                          DISCUSSION
    As an initial matter, we note that Lannett no longer
argues anticipation as a defense and does not challenge
the district court’s claim constructions on appeal. Also,
Lannett’s invalidity arguments relying on International
Publication No. WO 98/02186 (“Penkler”) and European
Publication No. EP 0636623 (“Robertson”), which were not
raised or developed either before the district court or on
appeal in its opening brief, are waived. SmithKline
Beecham Corp. v. Apotex Corp., 439 F.3d 1312, 1319–20
(Fed. Cir. 2006). We further note that because the court’s
nonobviousness decision applied commonly to all of the
challenged claims, the court did not and needed not make
separate decisions on the validity of the claims at issue.
Opinion, 246 F. Supp. 3d at 1030–31, 1032 n.2. Similarly,
on appeal, the parties do not make separate arguments on
validity, 3 and thus all of the claims at issue rise and fall



    3   In its opening brief, Lannett appears to suggest
that the district court’s nonobviousness conclusion with
respect to claim 15 was in error because claim 15 merely
8                  IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



together with the issue of whether it would have been
obvious to make zolmitriptan into a nasal spray.
    We proceed to the obviousness issue, the sole issue on
appeal, based on the prior art references and arguments
properly before us. On appeal from a bench trial, we
review a district court’s conclusions of law de novo and its
findings of fact for clear error. Golden Blount, Inc. v.
Robert H. Peterson Co., 365 F.3d 1054, 1058 (Fed. Cir.
2004). A factual finding is only clearly erroneous if,
despite some supporting evidence, we are left with the
definite and firm conviction that a mistake has been
made. United States v. U.S. Gypsum Co., 333 U.S. 364,
395 (1948); see also Polaroid Corp. v. Eastman Kodak Co.,
789 F.2d 1556, 1559 (Fed. Cir. 1986) (“The burden of
overcoming the district court’s factual findings is, as it
should be, a heavy one.”).
    A party challenging the validity of a patent must es-
tablish invalidity by clear and convincing evidence. See
Microsoft Corp. v. i4i Ltd. P’ship, 564 U.S. 91, 95 (2011).
Clear and convincing evidence should “place[] in the fact
finder ‘an abiding conviction that the truth of [the] factual
contentions are highly probable.’” Procter & Gamble Co.
v. Teva Pharm. USA, Inc., 566 F.3d 989, 994 (Fed. Cir.
2009) (quoting Colorado v. New Mexico, 467 U.S. 310, 316
(1984)) (second alteration in original).
    Obviousness is a question of law based on underlying
factual findings relating to “the scope and content of the



requires an “aqueous solution.” Appellant’s Br. 25–26.
However, beyond this oblique reference in its opening
brief, Lannett does not separately argue invalidity of
claim 15 until its reply brief. Id.; Reply Br. 5–7. We
therefore find Lannett’s separate invalidity arguments
regarding claim 15 waived. SmithKline Beecham, 439
F.3d at 1319–20.
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.               9



prior art,” “differences between the prior art and the
claims at issue,” “the level of ordinary skill in the perti-
nent art,” and “secondary considerations,” such as “com-
mercial success, long felt but unsolved needs, [and] failure
of others.” Apple Inc. v. Samsung Elecs. Co., 839 F.3d
1034, 1047–48 (Fed. Cir. 2016) (en banc) (internal quota-
tion marks omitted) (quoting Graham v. John Deere Co.,
383 U.S. 1, 17–18 (1966); KSR Int’l Co. v. Teleflex Inc.,
550 U.S. 398, 406 (2007)).
    On appeal, Lannett contends that the district court
erred in concluding that the claims at issue would not
have been obvious, based on an erroneous finding that the
prior art taught away from nasal formulations of
zolmitriptan. According to Lannett, the court improperly
disregarded express teachings in the prior art. Lannett
also argues that the court erred in finding that the 2012
agreement, which encompassed the entire Zomig® fran-
chise, including matters unrelated to the patents at issue,
supported its conclusion of nonobviousness. Lannett
alleges that it made a strong showing of obviousness, and
therefore, even accepting the district court’s findings of
teaching away and objective indicia of nonobviousness,
the court still erred in its ultimate conclusion of obvious-
ness.
    Appellees respond that the district court did not err
because it correctly found that a skilled artisan would not
have been motivated to make nasal formulations of
zolmitriptan or had a reasonable expectation of success in
doing so. Appellees contend that the court’s finding of
teaching away was not clearly erroneous, and, at any rate,
Lannett failed to prove obviousness by clear and convinc-
ing evidence. According to Appellees, the court’s factual
findings, including those relating to secondary considera-
tions, were supported by record evidence and based on
credibility determinations concerning the parties’ experts,
and such evidence should not be reweighed on appeal.
10                 IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



    We find no reversible error in the district court’s deci-
sion that Lannett failed to prove invalidity of the asserted
claims by clear and convincing evidence. The court’s
decision was supported by its underlying factual findings,
which we do not find clearly erroneous. Because the
question of the level of ordinary skill in the art is undis-
puted, we proceed to the remaining parts of the obvious-
ness analysis.
                              I
                             A
     Lannett contends that the prior art expressly disclos-
es nasal formulations of zolmitriptan, and it faults the
district court for failing to consider the prior art “as a
whole.” Appellant’s Br. 31. Lannett argues that prior art
references, in particular, Chauveau, 4 expressly disclosed



     4  Lannett alludes to Tepper & Rapoport as support-
ing the similar proposition that the prior art taught nasal
formulations of zolmitriptan, without making any particu-
lar invalidity argument based on Tepper & Rapoport.
Appellant’s Br. 17–18. Thus, we find any invalidity
argument relying on Tepper & Rapoport waived,
SmithKline Beecham, 439 F.3d at 1319–20; at any rate,
we find no clear error in the district court’s finding that
the statement that a zolmitriptan nasal spray being
“under development” in Tepper & Rapoport was a mere
“passing reference,” Opinion, 246 F. Supp. 3d at 1034.
“[U]nder development” does not mean developed, with an
expectation of success. Lannett also similarly alludes to
Marquess for the same proposition without making any
particular invalidity argument based on Marquess.
Appellant’s Br. 18–19. Similarly, any invalidity argument
based on Marquess is waived. SmithKline Beecham, 439
F.3d at 1319–20. Moreover, the court correctly found that
Marquess did not disclose the claimed nasal formulation
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.                       11



using zolmitriptan in a nasal spray. Lannett urges that
the court’s discounting of Chauveau’s express mention of
zolmitriptan in connection with nasal formulations consti-
tuted clear error. We disagree.
    Chauveau is generally directed to formulating an ac-
tive ingredient using capryl caproyl macrogol glycerides (a
version of which is marketed under the name Labrasol®)
for oromucosal administration of the active ingredient.
Chauveau col. 2 ll. 5–16, col. 3 ll. 18–21. As the district
court noted, Chauveau discusses that its teachings can be
applied to formulations for buccal, nasal, or pharyngeal
administration, among which the nasal route is preferred.
Id. col. 1 ll. 5–6, col. 2 ll. 27–29, col. 3 ll. 60–67, col. 5 ll. 8–
15. Chauveau’s teachings seek to provide pharmaceuti-
cally effective formulations for active ingredients that
would be degraded by oral administration, particularly in
the gastrointestinal tract. Id. col. 1 ll. 10–31, 48–52. The
court found that Chauveau “offers a laundry list of poten-
tial active ingredients,” including “over twenty-five cate-
gories or examples of medications.” Opinion, 246 F. Supp.
3d at 1033 (citing Chauveau col. 2 l. 38–col. 3 l. 14). At
the end of the list, Chauveau states that “[t]he active
substance can also be, in particular, an antimigraine
active substance, such as a triptan, such as sumatriptan
or zolmitriptan.” Chauveau col. 3 ll. 12–14. The example
formulations described in Chauveau include IS 159 (tryp-
tamine-5-O-carboxymethyl-tyrosyl-glycinamide) as the
active ingredient, but not zolmitriptan. Id. col. 4 ll. 10–
28, col. 5 l. 47–col. 9 l. 18.
    Lannett is correct that in an obviousness analysis,
prior art should be viewed as a whole. Takeda Chem.
Indus., Ltd. v. Alphapharm Pty., Ltd., 492 F.3d 1350,


of zolmitriptan according to the court’s construction of
“zolmitriptan,” which is unchallenged on appeal. Opinion,
246 F. Supp. 3d at 1034–35.
12                 IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



1358 (Fed. Cir. 2007). However, Chauveau, as a whole, is
not about intranasal formulations of zolmitriptan, which
is barely mentioned. It is about formulations of a wide
variety of compounds with capryl caproyl macrogol glycer-
ides. Zolmitriptan is mentioned once, with no further
mention in an example or claim. Moreover, properly
viewing the prior art as a whole, the district court here
made additional findings beyond the fact that zolmitrip-
tan was barely mentioned in Chauveau. Specifically, the
court found that the prior art taught that zolmitriptan
has a “unique attribute” in that its “[f]irst pass metabo-
lism results in an active metabolite, 183C91, which is two
to eight times more powerful than zolmitriptan itself.”
Opinion, 246 F. Supp. 3d at 1036–37. The court credited
Appellees’ expert, Dr. Rapoport, who provided his opinion
on the state of the prior art in support of this finding. Id.
The court also noted that Lannett’s expert did not dispute
the relevance of zolmitriptan’s active metabolite in con-
sidering whether to develop zolmitriptan formulations.
Id. at 1037. It is also undisputed that sumatriptan does
not have an active metabolite. See id. at 1033.
    Lannett nevertheless argues that the district court
erred in finding that the effectiveness of zolmitriptan
“relied on” its active metabolite, Appellant’s Br. 41–45,
and puts forth arguments to discount the significance of
zolmitriptan’s active metabolite. In particular, Lannett
argues that triptans are specifically designed to act as
serotonin receptor agonists, which, by itself, would rebut
the contention that zolmitriptan was understood to be
ineffective without the contribution of its metabolite. We
disagree, particularly because Lannett’s contentions are
without any evidentiary support beyond its attorney
arguments concerning factual issues. Ferring B.V. v.
Watson Labs., Inc.-Fla., 764 F.3d 1401, 1406–07 (Fed. Cir.
2014) (rejecting a conclusory obviousness argument
without evidentiary support).
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.                13



    Contrary to Lannett’s contentions, the district court
found that zolmitriptan’s more potent, active metabolite
was actually thought to be significant for its efficacy by a
person of skill in the art at the time. Specifically, the
court credited Appellees’ evidence of expert testimony and
studies and found that a skilled artisan would have
expected delayed or lower therapeutic effectiveness from
zolmitriptan if administered nasally because it would
have been “absolutely counterintuitive to make a nasal
spray when you have an active metabolite which is more
potent . . . than the drug itself.” Opinion, 246 F. Supp. 3d
at 1037 (quoting Dr. Rapoport); J.A. 667. As such, the
court found that “because of zolmitriptan’s reliance on its
active metabolite, the prior art failed to teach that
zolmitriptan by itself would be effective.” Id. The court
thus found zolmitriptan’s acting through its metabolite
not only relevant, which was substantially undisputed,
but also significant for a skilled artisan to consider re-
garding whether to make intranasally administered
zolmitriptan.
    In view of the totality of the record evidence of the
state of the prior art, we cannot find that the district
court clearly erred in its findings. Far from disregarding
the prior art’s discussion of zolmitriptan, the court specifi-
cally considered and acknowledged that zolmitriptan was
mentioned in connection with nasal formulations and
sprays. However, the court also properly considered
additional record evidence to make findings on the state
of the prior art as a whole.
    Both parties put forth evidence of various factors a
person of ordinary skill in the art would have considered.
Ultimately, the district court found that a skilled artisan
would not have been motivated to make a zolmitriptan
nasal spray with a reasonable expectation of success.
Opinion, 246 F. Supp. 3d at 1038–39; see id. at 1043–44.
“The presence or absence of a motivation to combine
references in an obviousness determination is a pure
14                 IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



question of fact,” and “[w]hat a reference teaches and
whether it teaches toward or away from the claimed
invention are questions of fact.” Par Pharm., Inc. v. TWi
Pharm., Inc., 773 F.3d 1186, 1196–97 (Fed. Cir. 2014)
(citation and internal quotation marks omitted). In
particular, the court here found that “a skilled artisan
would look to any of the other triptans before looking to
zolmitriptan to develop a pharmaceutical product that
would not take advantage of first pass metabolism.”
Opinion, 246 F. Supp. 3d at 1037.
    Based on the record before us, we do not find that the
court clearly erred in concluding that at the time,
zolmitriptan’s known significant reliance on its active
metabolite would have, on balance, dissuaded a person of
skill in the art from making nasal formulations of
zolmitriptan. See, e.g., Winner Int’l Royalty Corp. v.
Wang, 202 F.3d 1340, 1349–50 (Fed. Cir. 2000) (no clear
error in the district court’s finding that a person of skill in
the art, on balance, would not have made the claimed
invention); Intendis GmbH v. Glenmark Pharm. Inc., 822
F.3d 1355, 1366–67 (Fed. Cir. 2016) (no clear error when
the district court found that a person of skill in the art
would have pursued other formulations).
                              B
    The district court also considered evidence of second-
ary considerations, including the 2012 license agreement
between Impax and AstraZeneca covering the Zomig®
products for which Impax paid $130 million. The court
found that this 2012 agreement favored Appellees as it
found a nexus between the agreement and the ’237 and
’767 patents. However, it found that Appellees’ other
evidence of secondary considerations was inconclusive.
    Lannett argues that the district court’s analysis is un-
supported by any evidence, as the court, without any
support, did its own nexus analysis. We disagree. The
court found that the patents covering the oral formula-
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.                15



tions of zolmitriptan expired in only a little more than one
year after the effective date of the 2012 agreement, but
the patents covering the nasal formulations of zolmitrip-
tan, i.e., the ’237 and ’767 patents, were not set to expire
until 2021. Opinion, 246 F. Supp. 3d at 1039. Based on
the timing of the 2012 agreement as it related to the
various formulation patents and the sales data presented
to the court, it found that “a portion of the $130 million
had to be based on expected profits from Zomig nasal
spray.” Id. at 1040. Also, contrary to Lannett’s sugges-
tion, the court did rely on corroborating evidence showing
a nexus between the patents at issue and the licensing,
including Impax’s press release stating that Impax
“look[s] to build sales of the Zomig® nasal spray dosage
form.” Id. (quoting the press release); J.A. 2405. Thus,
there was adequate nexus between the intranasal patents
and $130 million. To the extent that Lannett invites us to
analyze the 2012 agreement and reweigh evidence, we
decline to do so. In view of other underlying factual
findings discussed above, it is sufficient for us to find that
the court did not clearly err in finding that the 2012
agreement is at least in part attributable to the patents at
issue.
                               II
    We finally consider whether the district court reached
a legally erroneous conclusion of nonobviousness. The
court called this case indeed a “close one.” Opinion, 246
F. Supp. 3d at 1043. The court stated that, on the one
hand, as a “promising migraine treatment,” various
aspects of zolmitriptan “would have been encouraging to a
skilled artisan motivated to make an anti-migraine nasal
spray better than Imitrex.” Id. On the other hand, the
court stated that “zolmitriptan had a known, powerful
metabolite, the creation of which would be delayed and
diminished by nasal administration” of zolmitriptan,
which “would point a skilled artisan away from including
zolmitriptan in a nasal spray.” Id. The court found
16                IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.



Appellees’ experts more credible than Lannett’s and
ultimately was not convinced that Lannett had shown
that the patents were invalid. Id. at 1044. We are un-
convinced that the court erred in that judgment.
    Contrary to Lannett’s suggestion, it has not shown a
“strong” case of obviousness and has not proven obvious-
ness by clear and convincing evidence. Procter & Gamble,
566 F.3d at 994. We are not left with a firm conviction
that the district court erred in its underlying factual
findings, as discussed above. Indeed, the court weighed
the evidence before it and made findings for and against
both Appellees and Lannett. We do not and should not
reweigh evidence or make factual findings anew on ap-
peal. See Teva Pharm. USA, Inc. v. Sandoz, Inc., 135 S.
Ct. 831, 838 (2015) (“A district court judge who has pre-
sided over, and listened to, the entirety of a proceeding
has a comparatively greater opportunity to gain that
familiarity than an appeals court judge who must read a
written transcript or perhaps just those portions to which
the parties have referred.”).
     Ultimately, we agree that this case was close. But, we
defer to the district court in its fact findings, including
what Chauveau discloses and the state of the prior art as
a whole. And we are especially persuaded by the testimo-
ny of Appellees’ expert, Dr. Rapoport, on which the dis-
trict court relied, who opined that it would have been
“absolutely counterintuitive” to make an intranasal
formulation of zolmitriptan, given that its activity primar-
ily came from its metabolite, and the agreement between
AstraZeneca and Impax covering the intranasal product
and its patents for which the latter paid $130 million. We
therefore conclude that the district court did not commit
reversible error in its nonobviousness conclusion.
    The district court did not clearly err in its underlying
factual findings, and we agree with the district court that
Lannett failed to prove by clear and convincing evidence
IMPAX LABS. INC.   v. LANNETT HOLDINGS INC.             17



that the claims of the ’237 and ’767 patents are invalid.
We have considered all the other arguments raised in the
briefs, but have not been persuaded that the district court
erred in its conclusions.
                          CONCLUSION
    For the foregoing reasons, we affirm the judgment of
the district court.
                         AFFIRMED
