Pfizer v. Apotex (Formerly Known as Torpharm)

United States Court of Appeals for the Federal Circuit

2006-1261

PFIZER, INC.,

Plaintiff-Appellee,

v.

APOTEX, INC. (formerly known as TorPharm, Inc.)

Defendant-Appellant.

Richard G. Greco, Kay Scholer LLP, of New York, New York, argued for plaintiff-
appellee. With him on the brief were Milton Sherman, Betty A. Ryberg, and Regina O.
Kent.

Robert B. Breisblatt, Welsh & Katz, Ltd., of Chicago, Illinois, argued for
defendant-appellant. With him on the brief were A. Sidney Katz, Steven E. Feldman,
and Philip D. Segrest, Jr.

Appealed from: United States District Court for the Northern District of Illinois

Chief Judge James M. Rosenbaum
 United States Court of Appeals for the Federal Circuit
2006-1261

PFIZER, INC.,

Plaintiff-Appellee,

v.

APOTEX, INC. (formerly known as TorPharm, Inc.)

Defendant-Appellant.

__________________________

DECIDED: March 22, 2007
__________________________

Before MICHEL, Chief Judge, MAYER, and LINN, Circuit Judges.

Opinion for the court filed by Chief Judge MICHEL. Circuit Judge LINN concurs in the
result.

MICHEL, Chief Judge.

Pfizer Inc. filed suit against Apotex, Inc. (formerly known as TorPharm, Inc.) in

the United States District Court for the Northern District of Illinois on July 30, 2003,

alleging that, pursuant to 21 U.S.C. § 355(j)(5)(B)(iii), Apotex’s filing with the United

States Food and Drug Administration (“FDA”) of its Abbreviated New Drug Application

(“ANDA”) No. 76-719 seeking approval to commercially sell amlodipine besylate tablets

(2.5 mg, 5 mg, and 10 mg strengths) before the expiration of the term of U.S. Patent No.

4,879,303 (“the ’303 patent”) to Pfizer, infringed claims 1-3 of the ’303 patent. The

ANDA product sought to be approved by Apotex is a generic version of Pfizer’s
amlodipine besylate drug product, which is commercially sold in tablet form in the

United States under the trademark Norvasc®. Norvasc® is approved by the FDA for

treating hypertension and chronic stable and vasospastic angina. The ’303 patent,

entitled “Pharmaceutically Acceptable Salts,” is listed in the FDA’s Approved Drug

Products with Therapeutic Equivalence Evaluations (“Orange Book”) with respect to the

Norvasc® drug product in accordance with 21 U.S.C. § 355(b)(1). Apotex certified in

ANDA No. 76-719 that it believed the ’303 patent was invalid and unenforceable, and

sought approval to market and sell its amlodipine besylate tablets before September 25,

2007 (i.e., the expiration date of the ’303 patent plus an additional six months of

pediatric exclusivity) pursuant to 21 C.F.R. § 314.94(a)(12)(i)(A)(4).

In its answer to Pfizer’s complaint, Apotex denied infringement and

counterclaimed for declaratory judgments that the claims of the ’303 patent are invalid

for anticipation and obviousness, and that the ’303 patent is unenforceable due to

Pfizer’s alleged inequitable conduct before the United States Patent and Trademark

Office (“USPTO”). Prior to trial, however, Apotex stipulated that its ANDA product

contains each limitation of claims 1-3 of the ’303 patent, and that if the ’303 patent were

upheld as valid and enforceable, its ANDA product would literally infringe those claims.

Following a bench trial, the district court entered a final judgment on January 29,

2006 for Pfizer and against Apotex on Apotex’s request for declaratory judgments that

the claims of the ’303 patent are invalid or unenforceable. Based on the stipulation, the

trial court found infringement. The district court then ordered that the effective date of

any approval of Apotex’s ANDA No. 76-719 shall not be earlier than September 25,

2007, and enjoined Apotex from making, using, offering to sell, selling, or importing into

2006-1261 2
the United States any product comprising amlodipine besylate covered by (or the use of

which is covered by) the claims of the ’303 patent until September 25, 2007. Pfizer Inc.

v. Apotex, Inc., No. 03C 5289 (N.D. Ill. Jan. 29, 2006).

Pfizer dismissed its claim of willful infringement against Apotex by a Stipulation

and Order dated January 23, 2006. Apotex now appeals from the district court’s final

judgment, challenging the rulings as to validity and enforceability. Because the district

court erred in holding that the subject matter of claims 1-3 of the ’303 patent would not

have been obvious, we reverse. We therefore do not address Apotex’s assertion that it

had proven that Pfizer engaged in inequitable conduct before the USPTO during

prosecution of the ’303 patent.

I. BACKGROUND

A.

Norvasc® contains amlodipine besylate. The active ingredient found in Norvasc®

is 2-[(2-aminoethoxy)methyl]-4-(2-chlorophenyl)-3-ethoxycarbonyl-5-methoxycarbonyl-

6-methyl-1,4-dihydropyridine, commonly referred to as amlodipine. Amlodipine is a

member of a class of compounds referred to as dihydropyridines. Active drug

molecules, such as amlodipine, are frequently made into pharmaceutically-acceptable

acid addition salts to improve their bioavailability. Amlodipine besylate 1 is an acid

addition salt form of amlodipine, formed from the reaction of amlodipine, a weak base,

and benzene sulphonic acid.

Pfizer’s Discovery Chemistry group, located in Sandwich, England, invented

amlodipine and discovered its anti-hypertensive and anti-ischemic pharmacological

1
Besylate is referred to in the art interchangeably as benzene sulphonate,
benzenesulphonate, or benzene sulfonate.

2006-1261 3
properties prior to 1982. Pfizer filed a patent application in the United Kingdom on

March 11, 1982 specifically claiming amlodipine. A U.S. counterpart application

claiming priority from the U.K. application issued as U.S. Patent No. 4,572,909 (“the

’909 patent”) on February 25, 1986. 2 The ’909 patent claims certain dihydropyridine

compounds and their pharmaceutically-acceptable acid addition salts. The ’909 patent

discloses that the pharmaceutically-acceptable acid addition salts of amlodipine “are

those formed from acids which form non-toxic acid addition salts containing

pharmaceutically acceptable anions, such as hydrochloride, hydrobromide, sulphate,

phosphate or acid phosphate, acetate, maleate, fumarate, lactate, tartrate, citrate and

gluconate salts,” and that the preferred salt is maleate. 3 ’909 patent col.2 ll.3-10.

Meanwhile, on or about July 14, 1982, the Discovery Chemistry group

recommended that amlodipine be developed as a commercial drug product. By this

time, Pfizer had made several acid addition salts of amlodipine, including the maleate,

fumarate, salicylate, hydrochloride, and methane sulphonate forms. The Discovery

Chemistry group designated amlodipine maleate as the drug substance for

development.

2
The ’909 patent was subject to an appeal before this court in Pfizer Inc. v.
Dr. Reddy’s Labs., Ltd., 359 F.3d 1361 (Fed. Cir. 2004). There, this court held that the
term of the ’909 patent as extended under the patent term restoration provision of the
Hatch-Waxman Act covers amlodipine and any salt or ester as claimed in claims 1, 7,
and 8. Id. at 1367.
3
We recognize that hydrochloride and hydrobromide are not technically
anions. However, since the patentee chose to be his own lexicographer, we will refer to
these two acids as anions for purposes of this opinion. Phillips v. AWH Corp., 415 F.3d
1303, 1316 (Fed. Cir. 2005) (en banc).

2006-1261 4
 On or about August 11, 1982, the project of formulating a commercial drug

product was assigned to Dr. James Wells, a manager in Pfizer’s Pharmaceutical

Research and Development Department, who was assisted by Mr. Edward Davison, a

member of the same group. By April 24, 1984, Dr. Wells identified a formulation for

amlodipine maleate that produced “excellent capsules.” In attempting to produce a

direct compression tablet product of an amlodipine maleate formulation, however, Dr.

Wells encountered two problems: (1) chemical instability of the amlodipine maleate, and

(2) stickiness of the tablet blend of amlodipine maleate. Chemical stability refers to the

resistance of a drug compound to chemical breakdown, while stickiness refers to the

adherence of the drug substance, in formulation, to manufacturing equipment, such as

the punch faces of a tablet-making press.

To solve the problems of the tablet form of amlodipine maleate, Dr. Wells

suggested that other amlodipine salts be made and tested. In a memo dated April 24,

1984, Dr. Wells acknowledged the difficulty in stickiness and stability he was

experiencing in attempting to make a tablet formulation of amlodipine maleate and

stated that, by changing from the maleate salt to the free base of amlodipine or another

acid addition salt, “many of the stability problems would disappear.” Dr. Wells identified

six alternative anions, i.e., hydrochloride, methane sulphonate, benzene sulphonate,

lactate, succinate, and acetate, as potential anions with which to create acid addition

salt forms of amlodipine. He also eventually added the tosylate anion to this group. Dr.

Wells testified at trial that he selected these candidates based on their differing

structures and properties, but could not explain why three of the seven alternative

anions were members of the same class of sulphonic acids.

2006-1261 5
 Mr. Davison testified at trial that he tested these amlodipine acid addition salt

forms as well as amlodipine maleate and the free base for solubility, pH, hygroscopicity,

and stickiness. Another researcher, Dr. Robin Platt, an analytical chemist at Sandwich,

was brought in to test the stability of the amlodipine acid addition salts. Dr. Platt

subjected the maleate, acetate, succinate, besylate, mesylate, and eventually the

tosylate, salicylate, and hydrochloride salt forms of amlodipine to thin-layer

chromatography to determine the number and amount of degradants found in the

various amlodipine salts, and compiled a ranking thereof based upon the stability of

each salt formulation.

Dr. Platt’s findings were communicated to Dr. Wells via memorandum on or

about October 9, 1984, wherein Dr. Platt reported that the besylate salt “showed a much

improved stability profile over the maleate in all cases.” On October 11, 1984, Dr. Wells

recommended via memorandum to Dr. J.R. Davidson, a deputy of Pfizer’s

Pharmaceutical Research and Development Department, that the amlodipine maleate

salt be replaced with amlodipine besylate for the commercial amlodipine tablet product

based on Dr. Platt’s memo and Mr. Davison’s test results.

By April 30, 1985, both amlodipine maleate and amlodipine besylate were

undergoing human testing in clinical trials. Pfizer scientists predicted that the capsule

form of amlodipine maleate would have a shelf life of three years, but that “poor stability

of amlodipine maleate tablet formulations” precluded commercialization. On the other

hand, the scientists noted that amlodipine besylate tablet formulations exhibited “clear

superiority” in their processing characteristics, particularly non-stickiness, and in

stability. Capsule formulations of amlodipine besylate had not yet been produced, but

2006-1261 6
work on this project was “expected to be straightforward.”

On April 4, 1986, Pfizer filed a patent application to amlodipine besylate in the

U.K., which eventually issued as U.K. Patent No. 160833. On May 5, 1986, Pfizer

submitted a supplement to the FDA stating that the dosage form anticipated for

commercial use would be a tablet of amlodipine besylate and that all future clinical trials

with amlodipine would use this new formulation. In the supplement, Pfizer stated, “We

feel that the change in salt form is justified since benzenesulfonate is a commercially

acceptable salt, as exemplified by the tranquilizer mesoridazine (Serentil).” In support

of the use of the besylate salt form of amlodipine, Pfizer submitted a summary of the

acute oral toxicity of amlodipine besylate and amlodipine maleate in rats and a

comparison of the effects of both the besylate and maleate forms on blood pressure and

heart rate of dogs. Pfizer stated that the results showed that there was no quantitative

difference in efficacy between equivalent doses of amlodipine besylate tablets or

capsules and amlodipine maleate capsules. In addition, Pfizer submitted a

pharmacokinetic report and interim clinical summary showing that amlodipine besylate

tablets and amlodipine maleate capsules were bioequivalent and had comparable

safety and toleration when administered to healthy human volunteers.

On March 25, 1987, Pfizer filed a U.S. application (serial no. 07/030,658) to

amlodipine besylate claiming priority from the U.K. application. During prosecution, the

examiner initially rejected all claims of the application as obvious over the ’909 patent in

view of U.S. Patent 4,032,637 to Spiegel (1977) (“Spiegel”) and U.S. Patent 3,816,612

to Schmidt (1974) (“Schmidt”). The examiner noted that Schmidt discloses that aryl

sulphonic acid salts, which include besylate, are superior to the preferred maleate of the

2006-1261 7
’909 patent, while Spiegel provides an example of a pharmaceutical compound wherein

the besylate form is specifically identified as the preferred embodiment. In response to

the rejection, Pfizer argued that the besylate salt,

while not the most soluble salt, has many other advantages not possessed
by other acid addition salts . . . . [I]n addition to having good solubility, [the
besylate salt] is unique in imparting to the product good stability,
nonhygroscopicity and good processability. For one salt to have all of
these outstanding features is not suggested or taught in the art, and would
require extensive experimentation to find.

The examiner, however, maintained the rejection, stating that “these qualities are basic

considerations by a person skilled in the art for selecting a suitable pharmaceutical salt”

as evidenced by Berge, “Pharmaceutical Salts,” J. Pharm. Sci., 66(1):1-19 (Jan. 1977)

(“Berge”). Table 1 of Berge shows 53 FDA-approved, commercially marketed anions,

including benzene sulphonate, that are useful for making pharmaceutically-acceptable

salts, and lists the relative frequency of which each was used as a percentage based on

the total number of anions or cations in use through 1974. Berge discloses that

benzene sulphonate had a frequency of use of 0.25%.

In response to a final obviousness rejection by the Examiner, Pfizer filed a

continuation application (serial no. 07/256,938) and abandoned the original application.

Along with the continuation application, Pfizer submitted a preliminary amendment and

statement, and a declaration under 37 C.F.R. § 1.132 by Dr. Wells dated October 3,

1988 (“Wells Declaration”). In the statement, Pfizer argued that the Wells Declaration

demonstrated that the besylate salt of amlodipine possessed “all the desired

characteristics necessary for a medicinal agent” and that it would not have been

obvious “that only the besylate salt of amlodipine would have all the necessary

properties for a commercial product.” Pfizer argued that choosing an appropriate salt is

2006-1261 8
a very difficult task “since each salt imparts unique properties to the parent compound”

and that one skilled in the art would “conclude that the besylate salt of amlodipine is a

unique compound and not an obvious one.” The Wells Declaration stated that the

besylate salt of amlodipine was “found to possess a highly desirable combination of

physicochemical properties,” including good solubility, stability, non-hygroscopicity, and

processability, which properties are “unpredictable both individually and collectively.”

The continuation application was allowed and issued as the ’303 patent on

November 7, 1989. The first three claims of the ’303 patent are reproduced here:

1. The besylate salt of amlodipine.

2. A pharmaceutical composition comprising an antihypertensive,
antiischaemic or angina-alleviating effective amount of the besylate salt of
amlodipine as claimed in claim 1 together with a pharmaceutically-
acceptable diluent or carrier.

3. A tablet formulation comprising an anti-hypertensive, antiischaemic or
angina-alleviating effective amount of the besylate salt of amlodipine as
claimed in claim 1 in admixture with excipients.

Norvasc® was launched as a commercial product by Pfizer in the U.S. in

November 1992.

B.

From January 11, 2006, to January 18, 2006, the district court conducted a

bench trial on the issues of (1) whether the claims of the ’303 patent were anticipated by

the disclosure of the ’909 patent, (2) whether the ’303 patent was invalid for

obviousness, and (3) whether the claims of the ’303 patent were unenforceable due to

inequitable conduct before the USPTO. On January 18, 2006, the district court stated

its findings and conclusions pursuant to Fed. R. Civ. P. 52(a) orally in open court.

Bench Order Tr. 1-28, January 18, 2006. The district court concluded that Apotex failed

2006-1261 9
to meet its burden of proving invalidity or inequitable conduct by clear and convincing

evidence.

The district court first addressed the issue of invalidity by anticipation, finding that

while the ’909 patent claims a genus of pharmaceutically-acceptable salts of amlodipine

that encompasses amlodipine besylate, the ’909 patent does not as a matter of law

disclose it. The district court held that since the ’909 patent does not list the species of

a salt made from benzene sulphonate, it does not anticipate the claims of the ’303

patent.

With regard to obviousness, the district court rejected Apotex’s argument that the

’909 patent in view of the Berge article (and other prior art) rendered the invention of the

claims of the ’303 patent obvious. The district court first found that a person of ordinary

skill in the art would have a bachelor’s degree in pharmaceutical science or analytical

chemistry, and some experience in drugs and drug preparation. The district court

concluded that the Berge article does not direct the skilled artisan to create the besylate

salt of amlodipine because Berge discloses that benzene sulphonate was used only at a

frequency of 0.25%, or 1 out of every 400 drugs, prior to 1974. The district court noted

that the examiner must have considered the Berge article since it was cited in the ’303

patent, yet the examiner ultimately determined that the claims of the ’303 patent were

not obvious in view of this reference. 4 Further, the district court stated that there would

4
The trial transcript reads, “The patent examiner cannot [sic] have been
aware of the Berge article as it was specifically noted and cited in the ’303 patent itself.
As such, the Court could not possibly find by clear and convincing evidence that the
article and its teachings could not have been considered by the patent [sic] when
ultimately determining whether the ’303 patent was obvious . . . .” Bench Order Tr.
22:16-22. We interpret this passage in the only way that makes sense—that the

2006-1261 10
be no expectation of success in making a besylate salt of amlodipine because, as Berge

teaches and expert testimony on both sides accepted, “There is no reliable way of

predicting the influence of a particular salt species on the behavior of a parent

compound.” Bench Order Tr. 23:3-6.

The district court also stated that the besylate salt of amlodipine was

unexpectedly superior to the amlodipine salts of the prior art. Specifically, the district

court stated that, while amlodipine besylate was not superior to amlodipine maleate “in

every category,” it nonetheless “clearly and unexpectedly illustrates a superior

combination of properties when compared to what was suggested in the preferred

preparation”—ostensibly the amlodipine maleate disclosed as the preferred

embodiment of the ’909 patent. These properties included good solubility, stability, non-

hygroscopicity, and processability (non-stickiness). The district court found that

amlodipine besylate exhibited at least a solubility exceeding 1.0 mg/ml, which the court

stated is the desirable solubility factor for a commercial product, and that the ’303 patent

listed the besylate salt form of amlodipine as the most stable salt form out of eight salts

tested, with the maleate salt form being sixth on the list.

The district court also rejected Apotex’s argument that amlodipine besylate is

actually hygroscopic rather than non-hygroscopic as disclosed in the ’303 patent.

Apotex asserted that amlodipine besylate attracts water because it (1) can exist as a

hydrate, (2) may have water within its crystalline structure, and (3) can have water on its

surface at extended temperatures and humidity. The district court stated that while

each of these facts is true, each was entirely unenlightening because hygroscopicity per

Examiner did consider the Berge reference during prosecution. While oral bench
rulings are certainly authorized, they may be ill-advised in a case of this complexity.

2006-1261 11
se was not a critical factor. Instead, the district court emphasized that the maleate salt

of amlodipine underwent a Michael addition reaction when exposed to water, creating at

least ten degradation products making amlodipine maleate unsuitable at least in tablet

form for medicinal purposes, whereas the amlodipine besylate did not undergo the

same reaction. Lastly, the district court found that Pfizer conducted extensive tests for

processability of the amlodipine besylate by manufacturing tablets on conventional

tablet-making machinery and measuring the amount of product sticking to the punch

face after each manufacturing run. The district court concluded that the tests showed

that amlodipine besylate was sufficiently non-sticky so as to be commercially

processable and less sticky than the maleate form.

Besides evidence of superiority provided in the ’303 patent itself, the district court

pointed to another “objective consideration” in determining that amlodipine besylate was

not obvious over the prior art: “Pfizer would not have changed from the maleate, into

which it had invested both time and research dollars, to seek out a very strange and

rare besylate salt, absent an extremely good reason.” Bench Order Tr. 23:16-21. For

all these reasons, the district court held that the claims of the ’303 patent were not

proven invalid for obviousness.

Next, the district court rejected Apotex’s claim that Pfizer engaged in inequitable

conduct before the USPTO in violation of its duty of candor and 37 C.F.R § 1.56.

Apotex argued that Pfizer made several material misrepresentations to the USPTO

during prosecution of the application leading to the ’303 patent, including

misrepresenting the solubility, stability, and hygroscopicity of amlodipine besylate and

misrepresenting the number of tablets tested for processability both in the patent

2006-1261 12
application and in the Wells Declaration. Specifically, Apotex asserted that Pfizer (1)

fraudulently identified the solubility of amlodipine besylate in its application for patent as

4.6 mg/ml where internal Pfizer documents show the solubility to actually be 3.5 mg/ml;

(2) fraudulently claimed in the application to have tested over a thousand tablets for

stickiness where internal Pfizer documents show varying numbers up to only 150 tablets

were actually tested; and (3) fraudulently ranked the respective stabilities of the various

salt forms of amlodipine in an ordinal—rather than quantitative—fashion so as to

conceal from the USPTO that the stability differences between the besylate, tosylate,

and mesylate salt forms of amlodipine were actually very minor.

The district court first determined that none of these alleged misrepresentations

were either material or false. In this regard, the court stated that whether the solubility

of amlodipine besylate is 4.6 mg/ml as identified in the ’303 patent or 3.5 mg/ml as

identified in internal Pfizer documents was at most a minor discrepancy given that any

solubility over the critical 1.0 mg/ml level was sufficient solubility to meet the standards

of a drug company seeking to produce a commercial drug. As for stability, the district

court found that amlodipine besylate was far more stable than amlodipine maleate,

which as described above undergoes the undesirable Michael addition reaction.

Second, the district court held that Apotex failed to show intent to deceive by clear and

convincing evidence. Indeed, the court found “precious little evidence at all” showing an

intent to deceive, stating that “[w]hile it is clear that Pfizer was eager to extend the

patent life of its amlodipine compound, such a desire does not rise to the level of

fraudulent conduct.” Bench Order Tr. 25:24-26:1.

2006-1261 13
 On January 29, 2006, the district court entered a final judgment in favor of Pfizer

and against Apotex on Pfizer’s claim of infringement as well as on Apotex’s

counterclaims alleging and seeking declarations of invalidity and unenforceability of the

’303 patent. The district court also ordered that, pursuant to 35 U.S.C. § 271(e)(4)(A),

the effective date of any approval of Apotex’s ANDA No. 76-719 shall not be earlier than

September 25, 2007, and pursuant to 35 U.S.C. § 271(e)(4)(B), enjoined Apotex, its

officers, agents, servants, employees and attorneys, and those persons in active

concert or participation with it, from engaging in the manufacture, use, offer for sale, or

sale within the U.S., or importation into the U.S. of any product comprising amlodipine

besylate covered by, or the use of which is covered by, the claims of the ’303 patent

until September 25, 2007. Pfizer Inc. v. Apotex, Inc., No. 03C 5289 (N.D. Ill. Jan. 29,

2006). On February 17, 2006, Apotex filed a timely notice of appeal. We have

jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).

II. DISCUSSION

A.

Apotex appeals the district court’s final judgment that it failed to prove by clear

and convincing evidence that the invention of claims 1-3 of the ’303 patent would have

been obvious and are therefore invalid, and the district court’s finding that Apotex failed

to prove Pfizer committed inequitable conduct before the USPTO. Because the district

court erred in holding non-obvious the invention of claims 1-3 of the ’303 patent, we

reverse the district court’s judgment. Since we hold that claims 1-3 are invalid for

obviousness, we need not and do not address Apotex’s assertion that Pfizer engaged in

inequitable conduct before the USPTO during prosecution of the ’303 patent.

2006-1261 14
 On appeal from a bench trial, this court reviews the trial court’s conclusions of

law de novo and findings of fact for clear error. Golden Blount, Inc. v. Robert H.

Peterson Co., 365 F.3d 1054, 1058 (Fed. Cir. 2004). The ultimate conclusion of

whether a claimed invention would have been obvious is a question of law reviewed de

novo based on underlying findings of fact reviewed for clear error. Richardson-Vicks

Inc. v. Upjohn Co., 122 F.3d 1476, 1479 (Fed. Cir. 1997). A factual finding is clearly

erroneous if, despite some supporting evidence, “the reviewing court on the entire

evidence is left with the definite and firm conviction that a mistake has been committed.”

United States v. U.S. Gypsum Co., 333 U.S. 364, 395 (1948).

B.

The district court held that Apotex had established a prima facie case of

obviousness because the patent examiner initially rejected the claims to amlodipine

besylate for obviousness. Specifically, the district court stated, “The ’303 patent’s file

wrapper shows that the examiner originally rejected the claimed invention because of

obviousness. Under these circumstances, of course, the Court must accept that the

defendant has made a prima facie showing on this question.” Bench Order Tr. 21:20-

24. The district court’s ruling must be rejected, not only because it is legally incorrect,

but also because it may reflect a serious misconception regarding the proper burden of

proof each party bears in a patent litigation.

Our case law consistently provides that a court is never bound by an examiner’s

finding in an ex parte patent application proceeding. Fromson v. Advance Offset Plate,

Inc., 755 F.2d 1549, 1555 (Fed. Cir. 1985). Thus, it can never be the case that an

examiner’s interim finding of prima facie obviousness renders the claims of an issued

2006-1261 15
patent prima facie obvious. Instead, deference to the decisions of the USPTO takes the

form of the presumption of validity under 35 U.S.C. § 282. Purdue Pharma L.P. v.

Faulding Inc., 230 F.3d 1320, 1329 (Fed. Cir. 2000). That is, by statute a patent is valid

upon issuance, 35 U.S.C. § 282, and included within the presumption of validity is a

presumption of non-obviousness. Structural Rubber Prods. Co. v. Park Rubber Co.,

749 F.2d 707, 714 (Fed. Cir. 1984). Since we must presume a patent valid, the patent

challenger bears the burden of proving the factual elements of invalidity by clear and

convincing evidence. 5 That burden of proof never shifts to the patentee to prove

validity. Hybritech Inc. v. Monoclonal Antibodies, Inc., 802 F.2d 1367, 1375 (Fed. Cir.

1986). “The presumption [of validity] remains intact and [the burden of proof remains]

on the challenger throughout the litigation, and the clear and convincing standard does

not change.” Id.

It is true that once a challenger has presented a prima facie case of invalidity, the

patentee has the burden of going forward with rebuttal evidence. See Mas-Hamilton

Group v. LaGard, Inc., 156 F.3d 1206, 1216 (Fed. Cir. 1998) (citing Hybritech, 802 F.2d

at 1376); Cable Elec. Prods. Inc. v. Genmark, Inc., 770 F.2d 1015, 1022 (Fed. Cir.

1985) (“[I]f evidence is presented establishing a prima facie case of invalidity, the

opponent of invalidity must come forward with evidence to counter the prima facie

5
The “clear and convincing” standard is an intermediate standard which lies
somewhere in between the “beyond a reasonable doubt” and the “preponderance of the
evidence” standards of proof. Addington v. Texas, 441 U.S. 418, 425 (1979); see also
SSIH Equip. S.A. v. United States Int’l Trade Comm’n, 718 F.2d 365, 380-81 (Fed. Cir.
1983) (Nies, J., additional views). Although an exact definition is elusive, “clear and
convincing evidence” has been described as evidence that “place[s] in the ultimate
factfinder an abiding conviction that the truth of its factual contentions are highly
probable.” Colorado v. New Mexico, 467 U.S. 310, 316 (1984) (internal quotations
omitted).

2006-1261 16
challenge to the presumption of section 282.”). But, all that means is that even though a

patentee never must submit evidence to support a conclusion by a judge or jury that a

patent remains valid, once a challenger introduces evidence that might lead to a

conclusion of invalidity—what we call a prima facie case—the patentee “would be well

advised to introduce evidence sufficient to rebut that of the challenger.” Orthokinetics,

Inc. v. Safety Travel Chairs, Inc., 806 F.2d 1565, 1570 (Fed. Cir. 1986).

However, this requirement does not “in substance shift the burden of

persuasion,” Cable Elec., 770 F.2d at 1022, because “the presumption of validity

remains intact and the ultimate burden of proving invalidity remains with the challenger

throughout the litigation.” Mas-Hamilton Group, 156 F.3d at 1216; see also Innovative

Scuba Concepts, Inc. v. Feder Indus., Inc., 26 F.3d 1112, 1115 (Fed. Cir. 1994);

Ashland Oil, Inc. v. Delta Resins & Refractories, Inc., 776 F.2d 281, 287 (Fed. Cir.

1985). The trial court has the responsibility to determine whether the challenger has

met its burden by clear and convincing evidence by considering the totality of the

evidence, including any rebuttal evidence presented by the patentee. Stratoflex, Inc. v.

Aeroquip Corp., 713 F.2d 1530, 1534 (Fed. Cir. 1983).

The basis (as opposed to the mere existence) of an examiner’s initial finding of

prima facie obviousness of an issued patent is therefore, at most only one factual

consideration that the trial court must consider in context of the totality of the evidence

“in determining whether the party asserting invalidity has met its statutory burden by

clear and convincing evidence.” Fromson, 755 F.2d at 1555. It does not, however,

lessen or otherwise affect the burden of proof, nor does it require that unless the

patentee introduces evidence of secondary considerations to establish non-

2006-1261 17
obviousness, the patent challenger will necessarily prevail.

C.

The underlying factual determinations made by the trial court that this court must

review for clear error include (1) the scope and content of the prior art, (2) the level of

ordinary skill in the art, (3) the differences between the claimed invention and the prior

art, and (4) objective indicia of non-obviousness. Graham v. John Deere Co., 383 U.S.

1, 17 (1966). We start by noting that the parties stipulated to many of the facts, but

disagree as to the ultimate legal outcome of obviousness based upon those facts. The

parties do not dispute that benzene sulphonate was known in the art at the time of the

inventions claimed in the ’909 and ’303 patents. Pfizer admitted that several

publications, including the Berge article, were prior art to claims 1-3 of the ’303 patent

and pertinent to the problem the inventors sought to overcome. Neither party disputes

the district court’s characterization of the ordinarily skilled artisan.

Further, there is really no dispute as to the scope of the ’909 patent and the

differences between it and the claimed invention. The ’909 patent specifically states

that the pharmaceutically-acceptable salts of amlodipine “are those formed from acids

which form non-toxic acid addition salts containing pharmaceutically-acceptable

anions.” ’909 patent col.2 ll.3-6. The ’909 patent lists a genus of pharmaceutically-

acceptable anions “such as the hydrochloride, hydrobromide, sulphate, phosphate or

acid phosphate, acetate, maleate, fumarate, lactate, tartrate, citrate and gluconate.”

’909 patent col.2 ll.6-9. The only examples of acid addition salts of amlodipine are

maleates. The ’909 patent does not expressly disclose the benzene sulphonate anion

nor salts formed from benzene sulphonic acid or a larger class of sulphonic acids in

2006-1261 18
general. But, while neither the claims nor the written description of the ’909 patent

expressly disclose amlodipine besylate or the benzene sulphonate anion, neither do

they exclude amlodipine besylate or the benzene sulphonate anion. Rather, the only

limitations placed on the anion are that it is pharmaceutically-acceptable, and that in salt

form, it is able to produce a non-toxic acid addition salt. Thus, as the district court found

and the parties agree, the ’909 patent claims literally encompass amlodipine besylate.

By statute, a claimed invention is unpatentable if the differences between it 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.” 35 U.S.C.

§ 103(a). Subsumed within the Graham factors is a subsidiary requirement articulated

by this court that where, as here, all claim limitations are found in a number of prior art

references, the burden falls on the challenger of the patent to show by clear and

convincing evidence that a skilled artisan would have been motivated to combine the

teachings of the prior art references to achieve the claimed invention, and that the

skilled artisan would have had a reasonable expectation of success in doing so. DyStar

Textilfarben GmbH v. C.H. Patrick Co., 464 F.3d 1356, 1360 (Fed. Cir. 2006); Velander

v. Garner, 348 F.3d 1359, 1363 (Fed. Cir. 2003). Here, the parties vigorously disagree.

A difficulty in the district court’s opinion arises because, in assuming a prima

facie case of obviousness, the district court did not fully address whether Apotex

showed by clear and convincing evidence that a skilled artisan would have been

motivated to combine the teachings of the prior art references relied on, especially the

’909 patent and Berge, to achieve the claimed invention. However, the district court’s

omission in this case is harmless error because evidence of record easily satisfies us

2006-1261 19
that a reasonable fact-finder could only conclude that Apotex has shown by clear and

convincing evidence that the skilled artisan would indeed have been so motivated to

combine the prior art to produce the besylate salt of amlodipine. The record also

satisfies us that, contrary to the district court’s finding, a reasonable fact-finder could

only conclude that the skilled artisan would have had a reasonable expectation of

success with the besylate salt form of amlodipine for the reasons elaborated, post.

Motivation to Combine Prior Art References to Achieve the Claimed Invention

Pfizer does not argue that there was no motivation to combine the prior art

references per se. Rather, Pfizer argues that (1) the ’909 patent does not suggest or

motivate the skilled artisan to make amlodipine besylate because none of the anions

listed in the ’909 patent have a cyclic structure as does besylate, and (2) even if the

’909 patent were combined with Berge, the skilled artisan would not have been

motivated to make amlodipine besylate because Berge shows that besylate was

actually one of the most rarely used anions in the pharmaceutical industry, as only

0.25% of approved drugs as of 1974 were besylate salts. Finally, Pfizer asserts that

other prior art references relied upon by Apotex are not relevant because the examples

of besylate salts disclosed in these references are limited to pharmaceuticals unrelated

to amlodipine.

We reject Pfizer’s first argument, since a suggestion, teaching, or motivation to

combine the relevant prior art teachings to achieve the claimed invention does not have

to be found explicitly in the prior art references sought to be combined, but rather “may

be found in any number of sources, including common knowledge, the prior art as a

whole, or the nature of the problem itself.” DyStar, 464 F.3d at 1361; see also Ormco

2006-1261 20
Corp. v. Align Tech., Inc., 463 F.3d 1299, 1307-08 (Fed. Cir. 2006). In other words, it is

irrelevant that none of the anions specifically listed in the ’909 patent have a cyclic

structure, because the motivation to make amlodipine besylate here is gleaned not only

from the prior art as a whole rather than the ’909 patent alone, but also from the nature

of the problems encountered with the amlodipine maleate tablet formulations sought to

be solved by the inventors of the ’303 patent. In this regard, testimony of record

evidences that one skilled in the art would have been motivated to choose an anion

having a different structure than that of maleate. The maleate salt ion is acyclic and

consists of a double bond between the carbon atoms, whereas the besylate salt ion is

cyclic and lacks the same double bond. Early in development, Pfizer discovered that

amlodipine maleate was susceptible to degradation from a Michael addition reaction in

which the double bond of maleate underwent an addition reaction causing the formation

of degradation products. Apotex avers that unrebutted testimony from its expert, which

we find compelling, supports an inference that the skilled artisan actually would have

been encouraged, rather than discouraged, to choose an anion without the same

double bond, such as benzene sulphonate, in order to avoid the Michael addition

reaction. Thus, the fact that none of the anions listed in the ’909 patent have a cyclic

structure is hardly dispositive to the question of whether the skilled artisan would have

been motivated to combine the prior art references to achieve amlodipine besylate.

We similarly are not persuaded by Pfizer’s second argument, as clear and

convincing evidence shows that a skilled artisan would have been motivated to combine

the ’909 patent and Berge to make amlodipine besylate. Pfizer’s expert, Dr. Anderson,

testified that there were an unlimited number of anions, many of which could be used to

2006-1261 21
form pharmaceutically-acceptable acid addition salts. Yet a reasonable fact-finder could

not accept Dr. Anderson’s testimony that the number of acceptable anions was

“unlimited.” Of course, new salts can always be made or attempted. However,

irrefutable evidence shows that a skilled chemist at the time would simply make known

pharmaceutically-acceptable salts of whatever active ingredient with which he or she

was working at the time. Indeed, Mr. Davison, an inventor of the ’303 patent, testified

that it “would have been a mistake” to choose a novel anion. Rather, “part and parcel of

pharmaceutically accepted[] was to look in pharmacopoeias and compendia” to find an

anion having “precedence for use within the pharmaceutical industry.” Dr. Anderson

similarly admitted in his testimony that it would have been logical to use Berge’s list of

FDA-approved anions to produce a drug formulation:

Court: What if I sic my phalanx of zealous scientists on that list and then
come up with a product. Would that be a logical thing for me to do?
The Witness: It would be logical to try that.

This is true especially given the fact that the genus of FDA-approved anions at the time

was small, i.e., only 53. That benzene sulphonate was only used in creating 0.25% of

FDA-approved drugs is not highly probative, much less dispositive. Indeed, beyond

hydrochloride, which was used in approximately 43% of approved drugs, almost all

other salts could be characterized as “rarely used.” See Berge, Table 1 (showing that

40 out of 53 anions were used in less than 1% of drugs and 23 out of 53 were used in

0.25% or less of drugs).

But the outcome of this case need not rest heavily on the size of the genus of

pharmaceutically-acceptable anions disclosed by Berge because clear and convincing

evidence establishes that, out of the list of 53 anions, one of ordinary skill in the art

would have favorably considered benzene sulphonate because of its known acid

2006-1261 22
strength, solubility, and other known chemical characteristics as reported in several

other publications Pfizer has admitted are prior art. Schmidt discloses that aryl

sulphonic acids, such as benzene sulphonic acids, considerably increase the solubility

of pharmaceuticals containing one or more basically reacting nitrogen atoms. ’612

patent col.2 ll.14-41. Spiegel specifically identifies besylate as the preferred

pharmaceutically-acceptable acid addition salt form of a pharmaceutical compound.

’637 patent col.2 ll.38-39. Other patents not before the examiner during prosecution of

the ’303 patent also point to benzene sulphonate. U.S. Patent 3,970,662 to Carabateas

(1976) (“Carabateas”) discloses an intermediate dihydropyridine compound useful in the

form of an acid addition salt derived from benzene sulphonate. ’662 patent col.3 ll.35-

49 & col.4 ll.20-24. U.S. Patent 4,432,987 to Barth (1984) (“Barth”), assigned to Pfizer,

discloses the besylate acid addition salt form of a pharmaceutical composition having

excellent pharmacokinetic properties, near-optimal solubility, and improved stability.

’987 patent col.2 ll.45-46. Taken together, these references provide ample motivation to

narrow the genus of 53 pharmaceutically-acceptable anions disclosed by Berge to a

few, including benzene sulphonate.

The district court ignored the significance of these other prior art references

suggesting the besylate salt because the pharmaceuticals disclosed in those prior art

references were not described as useful to treat hypertension or angina, as is

amlodipine. By not considering these references in its obviousness analysis, however,

the district court clearly erred. As here, the besylate acid addition salt form was

described in these prior art references as useful in promoting stability and solubility, as

well as improving other physicochemical characteristics. That none of these references

2006-1261 23
discloses a medication for treating hypertension or angina like amlodipine is therefore

unimportant, if not actually irrelevant. As Pfizer concedes, the besylate part of the acid

addition salt has no therapeutic effect, but merely serves as a means to deliver the

amlodipine part of the molecule to the body. Prior art disclosing the use of benzene

sulphonate for improving the bioavailability of other pharmaceuticals—especially a

dihydropyridine as disclosed by Carabateas—is therefore highly relevant in weighing

the factors relating to obviousness.

Considering all of the evidence, we hold that a reasonable fact-finder could only

conclude that Apotex indeed produced clear and convincing evidence that one skilled in

the art, facing the problems including the stickiness of the tablet form of the maleate

acid addition salt, would have been motivated to combine the teachings of the ’909

patent, Berge, and other prior art, to produce the besylate salt of amlodipine.

Reasonable Expectation of Success

As noted above, the district court found that the skilled artisan would have had no

expectation of success in making a besylate salt of amlodipine because there was no

reliable way to predict the influence of a particular salt species on the active part of the

compound. We cannot reject the district court’s finding that in 1986, it was generally

unpredictable as to whether a particular salt would form and what its exact properties

would be. The problem with the district court’s ultimate conclusion of non-obviousness

based on that factual finding, however, is that case law is clear that obviousness cannot

be avoided simply by a showing of some degree of unpredictability in the art so long as

there was a reasonable probability of success. See In re Corkill, 771 F.2d 1496, 1500

(Fed. Cir. 1985) (“Although [the inventor] declared that it cannot be predicted how any

2006-1261 24
candidate will work in a detergent composition, but that it must be tested, this does not

overcome [the prior art’s] teaching that hydrated zeolites will work.”); see also Brown &

Williamson Tobacco Corp. v. Philip Morris Inc., 229 F.3d 1120, 1125 (Fed. Cir. 2000);

Merck & Co., Inc. v. Biocraft Labs., Inc., 874 F.2d 804, 809 (Fed. Cir. 1989); In re Merck

& Co., Inc., 800 F.2d 1091, 1097 (Fed. Cir. 1986). Indeed, a rule of law equating

unpredictability to patentability, applied in this case, would mean that any new salt—

including those specifically listed in the ’909 patent itself—would be separately

patentable, simply because the formation and properties of each salt must be verified

through testing. This cannot be the proper standard since the expectation of success

need only be reasonable, not absolute. Merck, 874 F.2d at 809; In re O’Farrell, 853

F.2d 894, 903 (Fed. Cir. 1988).

The evidence would convince a reasonable finder of fact that the skilled artisan

would have had that reasonable expectation of success that an acid addition salt of

besylate would form and would work for its intended purpose. See In re Rinehart, 531

F.2d 1048, 1053-54 (C.C.P.A. 1976). Specifically, the evidence clearly shows that as

soon as tablet processing problems arose with the amlodipine maleate tablet

formulations, Dr. Wells readily compiled a list of seven alternative anions—including the

besylate—each of which he expected would form an amlodipine acid addition salt:

Q. And one of the reasons why you chose these various salts [sic], or
suggested these various salts [sic], is because you expected that they
would be able to make a salt of them, correct?
A. There was an expectation, but that wasn’t guaranteed.

But, once again, only a reasonable expectation of success, not a guarantee, is needed.

O’Farrell, 853 F.2d at 903; Brown & Williamson, 229 F.3d at 1125. That reasonable

expectation of success is further amply reflected in Dr. Wells’ further testimony that he

2006-1261 25
expected these seven amlodipine acid addition salts would show improved

physicochemical characteristics over the maleate salt, including improved stability and

non-stickiness:

Q. And when you chose these salts . . . you believed that if you could,
in fact, make an amlodipine salt out of them, these might be a cure for the
problems you were having with maleate, correct?
A. Indeed.

We also note that the ’909 patent placed no limitations on the acid addition salt

whatsoever, except that it be non-toxic and formed from an acid containing a

pharmaceutically-acceptable anion. Accordingly, the ’909 patent contained a strong

suggestion that any and all pharmaceutically-acceptable anions would form non-toxic

acid addition salts and would work for their intended purpose—that is, to improve

bioavailability of the active ingredient amlodipine and to improve handling and storage

of amlodipine. Indeed, in proceedings before this court in Pfizer v. Dr. Reddy’s

Laboratories involving the ’909 patent, Pfizer downplayed any difference between

amlodipine maleate and any other acid addition salt form of amlodipine, including the

besylate, prompting this court to observe that the sole active ingredient is amlodipine,

and that it acts the same in the human body whether administered as a besylate salt or

as a maleate salt. 359 F.3d at 1366.

Finally, there is a suggestion in Pfizer’s supplemental filing with the FDA that it

was known that the besylate salt of amlodipine would work for its intended purpose:

“We feel that the change in salt form [from maleate to besylate] is justified since

benzenesulfonate is a commercially acceptable salt, as exemplified by the tranquilizer

mesoridazine (Serentil).” Thus, although Dr. Wells testified that it was not guaranteed

whether amlodipine besylate would form and what its salient characteristics would be,

2006-1261 26
“this does not overcome [the prior art’s] teaching that [amlodipine besylate] will work.”

Corkill, 771 F.2d at 1500.

Considering all of the evidence, we conclude that the district court clearly erred in

finding that Apotex failed to produce clear and convincing evidence that one skilled in

the art would have had a reasonable expectation of success with the besylate salt of

amlodipine.

“Obvious-to-Try”

To be sure, “to have a reasonable expectation of success, one must be

motivated to do more than merely to vary all parameters or try each of numerous

possible choices until one possibly arrived at a successful result, where 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.” Medichem, S.A. v. Rolabo, S.L., 437

F.3d 1157, 1165 (Fed. Cir. 2006) (internal quotations omitted). Pfizer argues that, if

anything, amlodipine in its besylate salt form would at most be “obvious to try,” i.e., to

vary all parameters or try each of numerous possible choices to see if a successful

result was obtained. O’Farrell, 853 F.2d at 903.

Parties before this court often complain that holdings of obviousness were based

on the impermissible “obvious to try” standard, and this court has accordingly struggled

to strike a balance between the seemingly conflicting truisms that, under 35 U.S.C.

§ 103, “obvious to try” is not the proper standard by which to evaluate obviousness, In

re Antonie, 559 F.2d 618, 620 (C.C.P.A. 1977), but that, under O’Farrell and other

precedent, absolute predictability of success is not required. 853 F.2d at 903.

Reconciling the two is particularly germane to a situation where, as here, a formulation

2006-1261 27
must be tested by routine procedures to verify its expected properties. The question

becomes then, when the skilled artisan must test, how far does that need for testing go

toward supporting a conclusion of non-obviousness?

As we have said before, “[e]very case, particularly those raising the issue of

obviousness under section 103, must necessarily be decided upon its own facts.” In re

Jones, 958 F.2d 347, 350 (Fed. Cir. 1992). Consequently, courts cannot decide the

obviousness or non-obviousness of a patent claim by proxy. Undue dependence on

mechanical application of a few maxims of law, such as “obvious to try,” that have no

bearing on the facts certainly invites error as decisions on obviousness must be

narrowly tailored to the facts of each individual case. As we stated in DyStar,

Obviousness is a complicated subject requiring sophisticated analysis,
and no single case lays out all facets of the legal test. [There is] danger
inherent in focusing on isolated dicta rather than gleaning the law of a
particular area from careful reading of the full text of a group of related
precedents for all they say that is dispositive and for what they hold. When
parties . . . do not engage in such careful, candid, and complete legal
analysis, much confusion about the law arises and, through time, can be
compounded.

464 F.3d at 1367. On the facts of this case, however, we are satisfied that clear and

convincing evidence shows that it would have been not merely obvious to try benzene

sulphonate, but would have been indeed obvious to make amlodipine besylate.

First, this is not the case where there are “numerous parameters” to try. Rather,

the only parameter to be varied is the anion with which to make the amlodipine acid

addition salt. Although we recognize some degree of unpredictability of salt formation,

see, e.g., Sanofi-Synthelabo v. Apotex, Inc., 470 F.3d 1368, 1379 (Fed. Cir. 2006), the

mere possibility that some salts may not form does not demand a conclusion that those

that do are necessarily non-obvious. This is especially true here, where (1) as noted

2006-1261 28
above, the skilled artisan had a reasonable (although not guaranteed) expectation that

amlodipine besylate would form; (2) Pfizer conceded in prior litigation that the type of

salt had no effect on the therapeutic effect of the active ingredient, amlodipine, and was

practically interchangeable, Pfizer v. Dr. Reddy’s Labs., 359 F.3d at 1365-66; and (3)

numerous other publications (described above) clearly directed the skilled artisan to a

pharmaceutically-acceptable acid addition salt made from benzene sulphonate,

including, significantly, the Carabateas patent which taught the besylate acid addition

salt form of another dihydropyridine pharmaceutical compound.

Second, this is not the case where the prior art teaches merely to pursue a

“general approach that seemed to be a promising field of experimentation” or “gave only

general guidance as to the particular form of the claimed invention or how to achieve it.”

O’Farrell, 853 F.2d at 903; Medichem, 437 F.3d at 1167. Here, as admitted by Mr.

Davison, in selecting an acid addition salt formulation, one skilled in the art looked to

pharmacopoeias and compendia to find a salt that was previously approved by the FDA

and used successfully within the pharmaceutical industry. Berge clearly pointed the

skilled artisan to 53 anions that, as of 1974, were pharmaceutically acceptable. As Dr.

Wells’ testimony and the Carabateas patent demonstrated, one of ordinary skill in the

art was capable of further narrowing that list of 53 anions to a much smaller group,

including benzene sulphonate, with a reasonable expectation of success.

Finally, Pfizer protests that a conclusion that amlodipine besylate would have

been obvious disregards its “discovery” because it was obtained through the use of trial

and error procedures. While the pharmaceutical industry may be particularly adversely

impacted by application of an “obvious to try” analysis, see, e.g., In re Merck, 800 F.2d

2006-1261 29
at 1100 (Baldwin, J., dissenting), that Pfizer had to verify through testing the expected

traits of each acid addition salt is of no consequence because it does not compel a

conclusion of non-obviousness here. In coming to this conclusion, we have not ignored

the fact that “[p]atentability shall not be negatived by the manner in which the invention

was made.” 35 U.S.C. § 103(a). Nor are we ignorant of the fact that reference to

“routine testing” or “routine experimentation” is disfavored. See, e.g., In re Yates, 663

F.2d 1054, 1056 n.4 (C.C.P.A. 1981) (“The Solicitor . . . argues that it is ‘not unobvious

to discover optimum or workable ranges by routine experimentation.’ In many

instances, this may be true. The problem, however, with such ‘rules of patentability’

(and the ever-lengthening list of exceptions which they engender) is that they tend to

becloud the ultimate legal issue—obviousness—and exalt the formal exercise of

squeezing new factual situations into preestablished pigeonholes. Additionally, the

emphasis upon routine experimentation is contrary to the last sentence of section 103.”)

(internal citation omitted); In re Saether, 492 F.2d 849, 854 (C.C.P.A. 1974) (“In his

argument that ‘mere routine experimentation’ was involved in determining the optimized

set of characteristics, the solicitor overlooks the last sentence of 35 U.S.C. § 103 . . . .

Here we are concerned with the question of whether the claimed invention would have

been obvious at the time it was made to a person having ordinary skill in the art—not

how it was achieved.”) (internal citation omitted); In re Fay, 347 F.2d 597, 602 (C.C.P.A.

1965) (“[W]e do not agree that ‘routine experimentation’ negatives patentability. The

last sentence of section 103 states that ‘patentability shall not be negatived by the

manner in which the invention was made.’ To support the board’s decision that ‘routine

experimentation within the teachings of the art’ will defeat patentability requires a

2006-1261 30
primary determination of whether or not appellants’ experimentation comes within the

teachings of the art. Whether the subsequent experimentation is termed ‘routine’ or not

is of no consequence.”).

However, on the particularized facts of this case, consideration of the “routine

testing” performed by Pfizer is appropriate because the prior art provided not only the

means of creating acid addition salts but also predicted the results, which Pfizer merely

had to verify through routine testing. Merck, 874 F.2d at 809. The evidence shows that,

upon making a new acid addition salt, it was routine in the art to verify the expected

physicochemical characteristics of each salt, including solubility, pH, stability,

hygroscopicity, and stickiness, and Pfizer’s scientists used standard techniques to do

so. These type of experiments used by Pfizer’s scientists to verify the physicochemical

characteristics of each salt are not equivalent to the trial and error procedures often

employed to discover a new compound where the prior art gave no motivation or

suggestion to make the new compound nor a reasonable expectation of success. This

is not to say that the length, expense, and difficulty of the techniques used are

dispositive since many techniques that require extensive time, money, and effort to

carry out may nevertheless be arguably “routine” to one of ordinary skill in the art.

Rather, our conclusion here relies on the fact that one skilled in the art would have had

a reasonable expectation of success at the time the invention was made, and merely

had to verify that expectation. Cf. Velander v. Garner, 348 F.3d 1359, 1368 (Fed. Cir.

2003) (that one skilled in the art would view variability in producing fibrinogen in

transgenic mammals as evidence that “expense, time and effort” would be involved did

not equate to a conclusion that success was unlikely). Simply put, to conclude that

2006-1261 31
amlodipine besylate would have been obvious, “the prior art, common knowledge, or the

nature of the problem, viewed through the eyes of an ordinary artisan” merely had to

suggest reacting amlodipine base with benzene sulphonic acid to form the besylate acid

addition salt, and that that acid addition salt form would work for its intended purpose.

DyStar, 464 F.3d at 1361. They did. See O’Farrell, 853 F.2d at 904.

We find this case analogous to the optimization of a range or other variable

within the claims that flows from the “normal desire of scientists or artisans to improve

upon what is already generally known.” In re Peterson, 315 F.3d 1325, 1330 (Fed. Cir.

2003) (determining where in a disclosed set of percentage ranges the optimum

combination of percentages lies is prima facie obvious). In In re Aller, 220 F.2d 454,

456 (C.C.P.A. 1955), our predecessor court set forth the rule that the discovery of an

optimum value of a variable in a known process is usually obvious. See also In re

Boesch, 617 F.2d 272, 276 (C.C.P.A. 1980) (“[D]iscovery of an optimum value of a

result effective variable in a known process is ordinarily within the skill of the art.”).

Similarly, we hold that the optimization of the acid addition salt formulation for an active

pharmaceutical ingredient would have been obvious where as here the acid addition

salt formulation has no effect on the therapeutic effectiveness of the active ingredient

and the prior art heavily suggests the particular anion used to form the salt. Cf. In re

Geisler, 116 F.3d 1465, 1470 (Fed. Cir. 1997) (“‘[I]t is not inventive to discover the

optimum or workable ranges by routine experimentation.’” (quoting Aller, 220 F.2d at

456)); In re Kulling, 897 F.2d 1147, 1149 (Fed. Cir. 1990) (finding no clear error in

Board of Patent Appeals and Interferences’ conclusion that the amount of eluent to be

used in a washing sequence was a matter of routine optimization known in the pertinent

2006-1261 32
prior art and therefore obvious). Indeed, the logical line of testing was to react benzene

sulphonate with amlodipine to confirm the presence of a salt, and then to verify that the

physicochemical properties of amlodipine besylate were adequate, particularly the trait

of sufficient non-stickiness. The experimentation needed, then, to arrive at the subject

matter claimed in the ’303 patent was “nothing more than routine” application of a well-

known problem-solving strategy, Merck, 874 F.2d at 809, and we conclude, “the work of

a skilled [artisan], not of an inventor.” DyStar, 464 F.3d at 1371; see also In re Luck,

476 F.2d 650, 652-53 (C.C.P.A. 1973) (use of routine testing to identify optimum

amounts of silane to be employed in a lamp coating, without establishing a critical upper

limit or demonstrating any unexpected result, lies within the ambit of the ordinary skill in

the art); In re Esterhoy, 440 F.2d 1386, 1389 (C.C.P.A. 1971) (“One skilled in the art

would thus manifestly operate the Switzer et al. process under conditions most

desirable for maximum and efficient concentration of the acid. The conditions recited in

the claims appear to us to be only optimum and easily ascertained by routine

experimentation.”); In re Swentzel, 219 F.2d 216, 219 (C.C.P.A. 1955) (“It may well be

that the size represents the largest particles suitable for appellant’s purpose, but the

determination of that desired size under the present circumstances involves nothing

more than routine experimentation and exercise of the judgment of one skilled in the

art.”); In re Swain, 156 F.2d 246, 247-48 (C.C.P.A. 1946) (“In the absence of a proper

showing of an unexpected and superior result over the disclosure of the prior art, no

invention is involved in a result obtained by experimentation.”).

Thus, while patentability of an invention is not negated by the manner in which it

was made, “the converse is equally true: patentability is not imparted where ‘the prior

2006-1261 33
art would have suggested to one of ordinary skill in the art that this process should be

carried out and would have a reasonable likelihood of success.’” Merck, 874 F.2d at

809 (quoting In re Dow Chem. Co., 837 F.2d 469, 473 (Fed. Cir. 1988)). For these

reasons, we hold that Apotex introduced clear and convincing evidence that a skilled

artisan would have had a reasonable expectation of success with the besylate salt form

of amlodipine at the time the invention was made. Accordingly, we agree with the

district court that a prima facie case of obviousness was established with regard to the

claims of the ’303 patent, albeit for different reasons.

Secondary Considerations

Before we turn to the remaining conflict between the parties—the district court’s

consideration of the objective indicia of non-obviousness—we must first address the

district court’s reference in its bench opinion to Pfizer’s business decision to switch its

commercial product from an amlodipine maleate formulation to an amlodipine besylate

formulation, apparently as evidence of non-obviousness. See Bench Order Tr. at 6:21-

7:1 (“Pfizer is a big company, which by this time had a large investment in amlodipine

maleate. . . . A decision to switch to some other product, or even to abandon the entire

product, is the corporate equivalent of turning the Queen Mary.”); Bench Order Tr. at

18:17-21 (“Pfizer would not have changed from the maleate, into which it had invested

both time and research dollars, to seek out a very strange and rare besylate salt, absent

an extremely good reason.”). The district court’s reliance on this “objective

consideration” seems suspect as there is no evidence in the appellate record to support

the implicit finding that Pfizer ever considered abandoning amlodipine or stood to lose

significant time and investment dollars. Indeed, we are not ignorant of the fact that

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pharmaceutical companies are in the business of research and development. We

therefore disregard the district court’s findings on this point as clearly erroneous, or in

any event insufficiently probative of non-obviousness to overcome the evidence of the

prior art teachings.

Evidence of unexpected results can be used to rebut a prima facie case of

obviousness. Peterson, 315 F.3d at 1330. The district court found that, while

amlodipine besylate was not superior to amlodipine maleate in every category of

physicochemical properties, it nonetheless “clearly and unexpectedly illustrates a

superior combination of properties when compared to” amlodipine maleate. 6 With

regard to solubility, the ’303 patent discloses that amlodipine besylate has a solubility of

4.6 mg/ml at pH 6.6, whereas amlodipine maleate has a solubility of 4.5 mg/ml at pH

4.8. The district court stated that any product having a solubility greater than 1.0 mg/ml

is acceptable, and that “[t]he rest is sound and fury.” Bench Order Tr. at 11:10. We

conclude from this statement that the district court did not find that the solubility of

amlodipine besylate was materially superior, much less “unexpectedly superior” to the

solubility of amlodipine maleate. Similarly, we also conclude that the district court did

not rely on non-hygroscopicity as a secondary consideration. Thus, the two allegedly

unexpected and superior properties remaining are drug stability and tablet processing.

With respect to stability, the district court found that the ’303 patent provided an

ordinal listing of several tested salts descending in rank order from the most stable to
6
We reject Apotex’s assertion that the district court erred by giving weight
to the commercial success of Norvasc®. The district court relied on the production of
billions of amlodipine besylate tablets by Pfizer as evidence of non-stickiness rather
than commercial success. Apotex’s arguments with regard to an alleged absence of a
“nexus” between the claimed features and the sales of Norvasc® are therefore
irrelevant.

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the least stable, where the besylate salt was the most stable of the eight salts tested,

and the maleate salt was the sixth most stable salt. The district court also found that

amlodipine besylate was “sufficiently nonsticky to obtain commercial processability.”

Pfizer asserts that these improvements have significant practical value and are

indicative of non-obviousness.

In contrast, Apotex asserts that the district court committed several errors when

assessing secondary considerations. Specifically, Apotex asserts that the district court

erred by comparing amlodipine besylate only to the maleate preferred embodiment

disclosed in the ’909 patent rather than the entire genus of amlodipine salts claimed

therein. Apotex also asks this court to discount Pfizer’s evidence of unexpectedly

superior properties because the stability and drug processing properties of amlodipine

besylate are neither “unexpected” nor “surprising.” Finally, Apotex asserts that even if

amlodipine besylate exhibits a better combination of solubility, pH, stability, non-

hygroscopicity, and non-stickiness properties than other members of the genus of

amlodipine salts, this purported superiority of amlodipine besylate is not significant

enough as a matter of law to make it non-obvious. Apotex argues that amlodipine is the

active ingredient and the sole source of therapeutic effects of amlodipine besylate,

whereas the besylate is merely a means of delivering the amlodipine part of the

molecule. Thus, Apotex asserts, any salt need only exhibit adequate physicochemical

characteristics in order to serve its purpose of delivering the amlodipine. Apotex

contends that the record here demonstrates that the amlodipine maleate tablet also

performs these same functions. The issue before us is whether, based upon the

evidence as a whole, Pfizer’s showing of superior results was sufficiently unexpected so

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as to rebut Apotex’s showing of a prima facie case of obviousness.

While we agree that the teaching of a prior art patent is not limited to its preferred

embodiment, see Merck, 874 F.2d at 807 (“the fact that a specific [embodiment] is

taught to be preferred is not controlling, since all disclosures of the prior art, including

unpreferred embodiments, must be considered”), the other amlodipine salts of which

Apotex complains (i.e., amlodipine tosylate and amlodipine mesylate) were not

expressly recited in the ’909 patent or elsewhere in the prior art. Thus, the district

court’s obligation to consider the entire range of prior art compounds would have been

satisfied here by its comparison of the closest prior art compound to amlodipine

besylate. Kao Corp. v. Unilever United States, Inc., 441 F.3d 963, 970 (Fed. Cir. 2006)

(“‘[W]hen unexpected results are used as evidence of nonobviousness, the results must

be shown to be unexpected compared with the closest prior art.’” (quoting In re Baxter

Travenol Labs., 952 F.2d 388, 392 (Fed. Cir. 1991)). However, there is precious little (if

any) evidence to support any implicit finding by the district court that amlodipine maleate

is actually the closest prior art compound to amlodipine besylate. Indeed, the prior art

of Schmidt, Spiegel, Carabateas, and Barth, discussed above, evidences that one

skilled in the art would expect an acid addition salt made from benzene sulphonate to

have good physicochemical properties.

Another defect in the district court’s reasoning is its failure to recognize that by

definition, any superior property must be unexpected to be considered as evidence of

non-obviousness. In re Chupp, 816 F.2d 643, 646 (Fed. Cir. 1987). Thus, in order to

properly evaluate whether a superior property was unexpected, the court should have

considered what properties were expected. Merck, 874 F.2d at 808. Here, Pfizer’s

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evidence must fail because the record is devoid of any evidence of what the skilled

artisan would have expected. We will not simply presume that the skilled artisan would

have expected that amlodipine besylate would have the same characteristics as

amlodipine maleate, because as Pfizer asserts, its properties are not absolutely

predictable. Further, Dr. Wells’ testimony reflects the fact that he believed that

amlodipine besylate would solve the problems of amlodipine maleate. Unrebutted

testimony from Apotex’s expert evidences that, given the range of 53 anions disclosed

by Berge, one skilled in the art would expect those anions to provide salts having a

range of properties, some of which would be superior, and some of which would be

inferior, to amlodipine maleate. Pfizer has simply failed to prove that the results are

unexpected. Boesch, 617 F.2d at 278.

Finally, we do not see the trial court’s finding that amlodipine besylate had

adequate physicochemical characteristics as sufficient to uphold the court’s ultimate

holding of unexpected superiority. Pfizer rejected amlodipine maleate not because it

failed to exhibit an adequate combination of solubility, pH, stability in capsule form, and

non-hygroscopicity, but because it could not be easily manufactured because of

stickiness and limited stability of amlodipine maleate in the preferred commercial form of

a tablet. The district court wrongly relied on the fact that the “besylate salt works”

because considerable evidence shows that amlodipine maleate also worked for its

intended purpose and even did so in human clinical trials, even though somewhat

inferior in ease of tableting and projected shelf-life. At most, then, Pfizer engaged in

routine, verification testing to optimize selection of one of several known and clearly

suggested pharmaceutically-acceptable salts to ease its commercial manufacturing and

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marketing of the tablet form of the therapeutic amlodipine. Creating a “product or

process that is more desirable, for example because it is stronger, cheaper, cleaner,

faster, lighter, smaller, more durable, or more efficient . . . to enhance commercial

opportunities . . . is universal—and even common-sensical.” DyStar, 464 F.3d at 1368.

Amlodipine besylate is obvious on the facts of this case because the ’909 patent

suggested—and Dr. Wells expected—that every other potential salt form of amlodipine

would be adequate for its intended purpose, i.e., to increase bioavailability of

amlodipine, and would solve the stickiness problem of the maleate salt. The fact that

amlodipine besylate was the best of the seven acid addition salts actually tested proves

nothing more than routine optimization that would have been obvious to one of ordinary

skill in the art. See Aller, 220 F.2d at 456 (“[E]ven though applicant’s modification

results in great improvement and utility over the prior art, it may still not be patentable if

the modification was within the capabilities of one skilled in the art.”). These facts lead

us to conclude that the resulting commercial embodiment claimed in the ’303 patent,

amlodipine besylate, does not satisfy the standards of patentability.

Alternatively, we hold that even if Pfizer showed that amlodipine besylate exhibits

unexpectedly superior results, this secondary consideration does not overcome the

strong showing of obviousness in this case. Although secondary considerations must

be taken into account, they do not necessarily control the obviousness conclusion.

Newell Cos., Inc. v. Kenney Mfg. Co., 864 F.2d 757, 768 (Fed. Cir. 1988). Here, the

record establishes such a strong case of obviousness that Pfizer’s alleged unexpectedly

superior results are ultimately insufficient. Id. at 769.

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 From our de novo assessment of the determination below on obviousness in

view of all of the evidence and for the reasons articulated above, we conclude that the

district court erred in holding that the claims of the ’303 patent would not have been

obvious.

III. CONCLUSION

Because we find claims 1-3 of the ’303 patent invalid for obviousness, we find it

unnecessary to address Apotex’s assertion that Pfizer engaged in inequitable conduct

during prosecution of the ’303 patent and that its patent should therefore be declared

unenforceable. For the aforementioned reasons, the district court’s judgment is

reversed.

REVERSED.

LINN, Circuit Judge, concurs in the result.

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