United States Court of Appeals 

for the Federal Circuit

__________________________ 

CEPHALON, INC. AND CIMA LABS, INC.,

Plaintiffs-Appellants, 

v.

WATSON PHARMACEUTICALS, INC., WATSON 

LABORATORIES, INC. AND WATSON PHARMA, 

INC.,

Defendants-Appellees. 

__________________________ 

2011-1325

__________________________ 

Appeal from the United States District Court for the 

District of Delaware in No. 08-CV-0330, Judge Sue L. 

Robinson. 

___________________________ 

Decided: February 14, 2013

___________________________ 

CAROLYN JACOBS CHACHKIN, Wilmer Cutler Pickering 

Hale and Dorr, LLP, of Washington, DC, argued for 

plaintiffs-appellants. With her on the brief were WILLIAM 

G. MCELWAIN and JACOB S. OYLE; and WILLIAM F. LEE

and MARK C. FLEMING, of Boston, Massachusetts. 

JAMES K. STRONSKI, Crowell & Moring, LLP, of New 

York, New York, argued for defendants-appellees. With 
CEPHALON v. WATSON PHARMA 2

him on the brief were CHIEMI D. SUZUKI and JACOB Z.

ZAMBRZYCKI. 

__________________________ 

Before REYNA, BRYSON,

∗ and WALLACH, Circuit Judges. 

WALLACH, Circuit Judge. 

This action arises out of the filing of an Abbreviated 

New Drug Application (“ANDA”) by Watson Pharmaceuticals, Inc., Watson Laboratories, Inc., and Watson Pharma, 

Inc. (collectively, “Watson”) for a generic version of 

FENTORA®. In response to Watson’s ANDA filing, 

Cephalon, Inc. and CIMA Labs, Inc. (collectively, “Cephalon”) instituted this patent infringement suit at the 

United States District Court for the District of Delaware 

asserting U.S. Patent Nos. 6,200,604 (“the ’604 patent”)

and 6,974,590 (“the ’590 patent”). After a bench trial, the 

district court found that Watson’s ANDA products did not 

infringe and held the asserted patents invalid for lack of 

enablement. Cephalon, Inc. v. Watson Pharms., Inc., 769 

F. Supp. 2d 729, 761 (D. Del. 2011). We reverse on the 

issue of enablement because Watson failed as a matter of 

law to show with clear and convincing evidence that

Cephalon’s patents require undue experimentation to 

practice the invention. As to the noninfringement finding, 

the district court did not clearly err. Thus, we reverse–

in–part and affirm–in–part. 

I.

A. Background of the Invention

The ’604 and ’590 patents (“Khankari patents”) generally relate to a method of drug delivery. The most 

common method of drug delivery occurs through the

∗ Judge Bryson assumed senior status on January 7, 2013.

 
3 CEPHALON v. WATSON PHARMA

gastrointestinal system upon oral administration. The 

Khankari patents, however, utilize a different route—

drug delivery via the mucous membrane lining or mucosa 

in the oral cavity. 

Oral mucosal drug delivery offers advantages. For instance, the oral mucosal route provides direct access to 

the bloodstream without having to travel through the 

gastrointestinal tract, which allows the drug to avoid the 

“first pass effect”—the percentage of drug lost to metabolization in the liver. As a result, drug delivery across the 

oral mucosa potentially provides patients with rapid onset 

of action at a lower dosage. 

B. The Claimed Invention

The Khankari patents1 disclose methods to administer a tablet (or other dosage form) comprising fentanyl2 or 

other pharmaceutical agents. Such tablets include effervescent agents used as penetration enhancers, which

influence drug absorption across the buccal, sublingual, 

and gingival mucosae.3 ’590 patent col. 2 ll. 13–15. The 

Khankari patents also disclose the use of an additional 

pH adjusting substance in combination with an effervescent agent for promoting the absorption of drugs. Id. col. 3 

ll. 18–20.

1 The inventors of the Khankari patents are as 

follows: Drs. Sathasivan Indiran Pather, Rajentra K. 

Khankari, Jonathan D. Eichman, Joseph R. Robinson,

and John Hontz. 

2

 Fentanyl is an opioid analgesic or painkiller and a 

Schedule II controlled substance, 21 U.S.C. § 812(c) 

Schedule II(b)(6), with high lipophilicity. 3 Different areas of the mouth are given different names. For example, the buccal mucosa is along the 

inside of the cheek, the sublingual mucosa is under the 

tongue, and the gingival mucosa is between the lips and 

gum. 

 
CEPHALON v. WATSON PHARMA 4

An “effervescent agent” includes at least one compound that evolves gas. Id. col. 2 ll. 44–45. The preferred 

effervescent agents evolve gas by means of a chemical 

reaction triggered by exposure of the effervescent agent 

(an effervescent couple) to water and/or saliva in the 

mouth. Id. col. 2 ll. 45–48. This reaction is most often the 

result of a soluble acid source, like citric acid, reacting 

with a source of carbon dioxide that is mostly basic, like 

an alkaline carbonate or bicarbonate.4 Id. col. 2 ll. 48–51, 

59. Carbon dioxide gas is evolved as a result of this 

reaction. Id. col. 2 ll. 51–52. The dosage form preferably 

includes an effervescent couple comprising both the acid 

source and a source for carbon dioxide. Id. col. 4. ll. 23–27.

The effervescent reaction occurring in the mouth affects the pH level of the saliva. Generally, pH levels can 

influence the relative concentrations of the ionized and 

un-ionized forms of the drug, which in turn, affects the 

dissolution of the drug in the saliva and absorption of the 

drug across the oral mucosa. Id. col. 3 ll. 20–24. The pH 

of solutions in which an effervescent agent has dissolved 

is slightly acidic due to the evolution of carbon dioxide. Id.

col. 3 ll. 24–25. Specifically, when carbon dioxide dissolves in saliva, it forms a weak acid (carbonic acid) that 

reduces salival pH. The carbonic acid thereafter dissociates into carbon dioxide and water; the carbon dioxide is 

released as gas, causing the pH to slowly rise providing 

4 The acid sources may be any which are safe 

for human consumption and generally include food acids, 

acid, and hydrite antacids such as: citric, tartaric, amalic, 

fumeric, adipic, and succinics. ’590 patent col. 2 ll. 56-60. 

Carbonate sources include dry solid carbonate and bicarbonate salt such as, preferably, sodium bicarbonate, 

sodium carbonate, potassium bicarbonate, potassium 

carbonate, magnesium carbonate, and the like. Id. col. 2 

ll. 60–64. Reactants which evolve oxygen or other gasses 

and which are safe for human consumption are also 

included. Id. col. 2 ll. 64–65.

 
5 CEPHALON v. WATSON PHARMA

for the initial low pH level suitable for dissolution and the 

eventual high pH level ideal for absorption. Thus, incorporating a pH adjusting substance in combination with 

effervescent agents may lead to an increase in the rate 

and extent of absorption of an active drug. Id. col. 3 ll. 18–

20. According to the Khankari patents, suitable pHadjusting substances include, but are not limited to, any 

of the acids or bases disclosed as effervescent compounds. 

Id. col. 3 ll. 47–55. 

Other pharmaceutical ingredients are preferably incorporated into the dosage form of the invention for a 

variety of purposes, including aiding disintegration. 

“Disintegrants may comprise up to about 20 weight 

percent” of the composition and, preferably, between 2% 

and 10% of the composition. Id. col. 4 ll. 41–51. 

“[S]uitable non-effervescent disintegration agents” may be 

used. Id. col. 4 l. 43. Excipient fillers “desirably will also 

assist in the rapid dissolution of the dosage form in the 

mouth.” Id. col. 5 ll. 28–32. Mannitol is listed among the 

(non-limiting) examples of such excipient fillers. Id.

The ’604 patent was filed on June 8, 1999 and issued 

on March 13, 2001. Priority is claimed to its provisional 

patent application (No. 60/079,652) filed on March 27, 

1998. The ’590 patent was filed on February 20, 2002 and 

issued on December 13, 2005. The ’590 patent claims 

priority to the ’604 patent’s application, and as a result, 

the patents share a common disclosure.

Claim 1 of the ’604 patent is the sole independent 

claim of that patent, and reads as follows: 

1. A method of administering at least one systemically distributable pharmaceutical agent across 

the oral mucosa comprising:

a) providing a solid oral dosage form including a 

pharmaceutically effective amount of an orally 
CEPHALON v. WATSON PHARMA 6

administerable medicament; and at least one effervescent agent in an amount sufficient to increase absorption of said orally administerable 

medicament across the oral mucosa; wherein said 

orally administerable medicament is not substantially encompassed by or dispersed in a material 

that prevents absorption of said medicament 

across the oral mucosa;

b) placing said solid oral dosage form in the mouth 

of a patient so that saliva in said patient’s mouth 

activates said at least one effervescent agent in 

said tablet; and

c) holding said solid oral dosage form and the dissolving contents of said solid oral dosage form in 

the mouth of a patient whereby said at least one 

effervescent agent promotes absorption of said 

orally administerable medicament across the oral 

mucosa. 

’604 patent col. 7 ll. 11–31 (emphasis added). The ’590 

patent expressly discloses fentanyl as the pharmaceutical 

agent. The ’590 patent recites one independent claim as 

follows:

1. A method of administration of fentanyl to a 

mammal across the oral mucosa thereof, said 

method comprising:

providing a solid oral dosage form comprising fentanyl or a pharmaceutically acceptable salt thereof and at least one saliva activated effervescent 

agent in an amount sufficient to increase absorption of said fentanyl or pharmaceutically acceptable salt thereof across said oral mucosa, at least 

one pH adjusting substance, and wherein said 

amount of said at least one effervescent agent is 

between about 5% by weight and about 80% by 
7 CEPHALON v. WATSON PHARMA

weight; and buccally, sublingually or gingivally 

administrating said solid oral dosage form to said 

mammal.

’590 patent col. 7 ll. 2–13 (emphasis added). 

C. Procedural History

Cephalon is the holder of the New Drug Application 

for fentanyl buccal tablets, sold under the trade name 

FENTORA®5 for the treatment of breakthrough cancer 

pain. The Khankari patents were listed in the FDA’s 

Orange Book in connection with this New Drug Application. See 21 U.S.C. § 355(b)(1). On July 10, 2007, Watson 

filed an ANDA for FDA approval to sell a generic counterpart of FENTORA® (“ANDA product”).6 Watson’s actions 

invoked the Hatch–Waxman Act, which establishes a 

procedure called a “Paragraph IV certification,” 21 U.S.C. 

§ 355(j)(2)(A)(vii)(IV), by which an entity that seeks to 

market a generic counterpart of a patented drug product 

or method of use, before the patent has expired, may 

challenge the patent before actually marketing the drug.7 

In response, on June 2, 2008, Cephalon instituted the 

underlying action in district court against Watson, first 

asserting the Khankari patents, and in a subsequent 

5 FENTORA® contains fentanyl citrate, mannitol, sodium starch glycolate, magenesium stearate, citric 

acid, sodium bicarbonate, and sodium carbonate. The 

sodium bicarbonate and citric acid are an effervescent 

couple that react to evolve carbon dioxide. 6 Watson’s ANDA products contain the active 

ingredient fentanyl citrate and the inactive ingredients

mannitol, sodium starch glycolate, potassium bicarbonate, 

and magnesium stearate. 

7 A Paragraph IV certification “is defined as an 

act of infringement for litigation purposes.” SanofiSynthelabo v. Apotex, Inc., 550 F.3d 1075, 1078 (Fed. Cir.

2008); see 21 U.S.C. § 355(j)(2)(A)(vii)(IV); 35 U.S.C. § 

271(e).

 
CEPHALON v. WATSON PHARMA 8

Complaint filed on September 25, 2009, asserting U.S. 

Patent No. 6,264,981 (“the ’981 patent”). The two actions 

were consolidated, and the district court held a bench trial

between May 10 and May 17, 2010. 8

In an opinion issued on March 11, 2011, the district 

court concluded that Cephalon did not prove, by a preponderance of the evidence, that Watson’s ANDA products 

infringe either of the Khankari patents under the district 

court’s claim construction. Cephalon, 769 F. Supp. 2d at 

761. The district court also held that Watson proved, by 

clear and convincing evidence, that the Khankari patents 

were invalid for lack of enablement. Id. Further, the 

district court determined that Watson failed to show that 

the asserted patents were invalid as anticipated or obvious in view of prior art. Id. Cephalon timely appeals. 

This court has jurisdiction under 28 U.S.C. § 1295(a)(1). 

II.

Cephalon raises the following issues on appeal: (1) 

whether the district court erred in ruling that Watson had 

carried its burden of proving by clear and convincing 

evidence that the asserted patents were invalid for lack of 

enablement; and (2) whether the district court erred in 

failing to consider Cephalon’s literal infringement contentions and ruling that Watson does not infringe the asserted claims. This court addresses these issues seriatim.

A. The District Court Committed Error in Holding 

That the Khankari Patents Were Invalid for Lack of 

Enablement

Enablement is a question of law that we review without deference, based on underlying factual inquiries that 

we review for clear error. MagSil Corp. v. Hitachi Global 

Storage Techs., Inc., 687 F.3d 1377, 1380 (Fed. Cir. 2012). 

8 The ’981 patent is not at issue in this appeal.

 
9 CEPHALON v. WATSON PHARMA

To satisfy section 112 of the 1952 Patent Act, the specification must enable a person of ordinary skill in the art to 

make and use the invention. 35 U.S.C. § 112, ¶1.9 This 

requirement is met when at the time of filing the application one skilled in the art, having read the specification, 

could practice the invention without “undue experimentation.” In re Wands, 858 F.2d 731, 736–37 (Fed. Cir. 1988). 

Whether undue experimentation is required “is not a 

single, simple factual determination, but rather is a 

conclusion reached by weighing many factual considerations.” ALZA Corp. v. Andrx Pharms., LLC, 603 F.3d 935, 

940 (Fed. Cir. 2010) (citing Wands, 858 F.2d at 737). 

The following factors may be considered when determining if a disclosure requires undue experimentation:

(1) the quantity of experimentation necessary, (2) 

the amount of direction or guidance presented, (3) 

the presence or absence of working examples, (4) 

the nature of the invention, (5) the state of the 

prior art, (6) the relative skill of those in the art, 

(7) the predictability or unpredictability of the art, 

and (8) the breadth of the claims.

Wands, 858 F.2d at 737 (“Wands factors”); Enzo Biochem, 

Inc. v. Calgene, Inc., 188 F.3d 1362, 1372 (Fed. Cir. 1999) 

(“The Wands factors, when applied from the proper temporal perspective . . . are a useful methodology for determining enablement . . . .”). These factors while 

illustrative are not mandatory. Enzo Biochem, Inc., 188

F.3d at 1371. What is relevant depends on the facts, and 

although experimentation must not be undue, a reasona9 Paragraph 1 of 35 U.S.C. § 112 was replaced 

with newly designated § 112(a) when § 4(c) of the Leahy–

Smith America Invents Act, Pub. L. No. 112–29, took 

effect on September 16, 2012. Because this case was filed 

before that date, we will refer to the pre-AIA version of § 

112.

 
CEPHALON v. WATSON PHARMA 10

ble amount of routine experimentation required to practice a claimed invention does not violate the enablement 

requirement. Id. The burden of proof here is on Watson to 

show that the Khankari patents are invalid for lack of 

enablement by clear and convincing evidence. See Auto. 

Tech. Int’l, Inc. v. BMW of N. Am., Inc., 501 F.3d 1274, 

1281 (Fed. Cir. 2007). 

The district court construed “effervescent agent” as 

recited in claim 1 of both Khankari patents to require, in 

part, “at least one compound that evolves gas by means of 

an effervescent reaction.” Cephalon, 769 F. Supp. 2d at 

744 (emphasis added). In particular, the district court 

acknowledged the “singularity” of the term “agent” and 

concluded that “effervescent agent” referred to a single 

compound. Id. at 743–44. Watson argued against this 

construction contending that the asserted patents describe “effervescent agent” synonymously with “effervescent couple.” Id. at 737. Focusing on “couple,” Watson 

posited that “effervescent agent” therefore requires a 

combination of two or more compounds that evolve gas. 

Id. While the parties do not appeal the district court’s 

claim construction, contentions surrounding the distinction between effervescent “agent” and “couple” persist. 

Specific to the enablement inquiry, the parties do not 

dispute that the Khankari patents are enabling as to an 

effervescent “couple” generating the claimed effervescent 

reaction, where the soluble acid source and the effervescent agent (carbonate source) are in the same tablet or 

other dosage form. Instead, the dispute arises from the 

district court’s claim construction requiring effervescent 

“agent” to be “at least one compound” that evolves gas. 

This “single compound effervescent agent” construction 

requires the soluble acid source to be in a separate tablet 

or dosage form from the effervescent agent. In addition, 

in order to achieve the claimed effervescent reaction, this 
11 CEPHALON v. WATSON PHARMA

construction requires these separate dosage forms to be

co-administered. 

The district court held that the Khankari patents 

lacked enabling disclosures illustrating a dosage form

having only the single compound effervescent agent. 

Cephalon, 769 F. Supp. 2d at 753–54. Specifically, it held 

that the disclosures lacked teachings directed to formulating and co-administering two separate dosage forms—one 

including a soluble acid source and the other containing 

the effervescent agent—to achieve an effervescent reaction. Id. at 753. The lack of disclosure of such methods of 

co-administration would, according to the court, necessitate undue experimentation to practice the invention. Id.

Cephalon on appeal contends that its expert, Dr. Robert O. Williams, testified that a skilled artisan could 

easily calculate the required amount of acid and coadminister a soluble acid source, which may be a separate 

tablet, a film, or a liquid, with the tablet containing the 

effervescent agent. Likewise, Cephalon argues that the 

Khankari patents describe multiple embodiments using 

effervescent formulations for fentanyl citrate along with

different amounts of sodium carbonate. According to 

Cephalon, the specification also discloses many different 

soluble acid sources and many different sources of carbonate, which can be combined into a nearly limitless 

number of acid/carbonate pairs that would generate the 

desired effervescent reaction. Indeed, Cephalon propounds Dr. Williams’s testimony that “it would be routine 

given what’s in the patent[s] about how to actually create 

the effervescence to use in the invention.” J.A. 6424, 

1383:20–22. 

Watson argues that the district court properly considered all the evidence and credited its expert, Dr. Russell 

Mumper. In addition, Watson contends the Khankari

patents do not provide specific parameters to conduct 
CEPHALON v. WATSON PHARMA 12

experiments to calculate a method of co-administration

and that Cephalon failed to produce evidence showing a 

successful co-administration method. Specifically, according to Watson, Cephalon should have produced evidence 

showing a successful effervescent reaction in the same 

area of the mouth between two co-administered tablets 

containing the acid and base compounds. 

As an initial matter, the district court determined 

that Watson established a “prima facie” case of lack of 

enablement and that Cephalon failed to “rebut” Watson’s 

prima facie case. Cephalon, 769 F. Supp. 2d at 751, 754. 

Actually, the burden of proof was Watson’s alone. Because we must presume a patent enabled, the challenger 

bears the burden, throughout the litigation, of proving 

lack of enablement by clear and convincing evidence. 

Morton Int’l, Inc. v. Cardinal Chem. Co., 5 F.3d 1464, 

1469–70 (Fed. Cir. 1993). Hence, there is no formal 

burden-shifting framework when addressing the issue of 

enablement. Accordingly, we examine whether Watson 

met its burden of proof and determine that it did not. 

Watson’s evidence on enablement was based heavily

on Dr. Mumper’s testimony. Dr. Mumper stated that 

“formulation of fentanyl with some couple in a tablet that 

would be administered into the mouth and must react 

with some externally applied acid . . . would be very 

difficult” and “complicated” and “would require I think the 

partnering with a clinician to talk about the timing effects 

and volume effects and how this would actually be translated to a patient actually doing this. I don’t know.” J.A. 

6337–38, 1184:17–1186:19. Dr. Mumper’s ipse dixit

statements that co-administration would be “difficult” and 

“complicated,” however, cannot be enough to constitute

clear and convincing evidence. See Ashland Oil, Inc. v. 

Delta Resins & Refractories, Inc., 776 F.2d 281, 294 (Fed. 

Cir. 1985) (“Lack of factual support for expert opinion 

going to factual determinations, however, may render the 
13 CEPHALON v. WATSON PHARMA

testimony of little probative value in a validity determination.”). Despite the district court’s finding according 

credibility to Dr. Mumper, his testimony is largely unsupported, and therefore, carries little weight in this analysis. 

The district court’s reliance on Cephalon’s expert testimony does not rescue Dr. Mumper’s unsubstantiated 

statements. Referring to inventor testimony regarding 

“drinking orange juice [as the soluble acid source] following administration of a[n effervescent agent],” Dr. Williams testified:

I think one of skill in the art, knowing in that example orange juice contains citric acid, would be 

able to calculate the amount of citric acid and put 

. . . [an effervescent agent] in a second, fastdissolve film or quick-dissolve tablet or something, 

to do a concomitant administration of [the] two 

dosage forms . . . .

J.A. 6424, 1383:1–2, 5–10. He further posited that creating an effervescent reaction by co-administering the two 

dosage forms would require “routine” experimentation. 

J.A. 6424, 1383:20–22. On cross examination, Dr. Williams explained the potential need for in vitro experiments and a formulator to work with a clinician to 

determine the parameters for co-administering a soluble 

acid source with an effervescent agent. J.A. 6424–25, 

1384:25–1385:7. According to the district court, Dr. 

Williams’s testimony regarding the potential need for 

experiments provided additional support for Dr. 

Mumper’s opinion that undue experimentation was 

required. Cephalon, 769 F. Supp. 2d at 753. The district 

court’s emphasis on the mere fact that experimentation 

may be necessary is misplaced, however. 

The question of undue experimentation is a matter of 

degree, and what is required is that the amount of exper-
CEPHALON v. WATSON PHARMA 14

imentation not be “unduly extensive.” Chiron Corp. v. 

Genentech, Inc., 363 F.3d 1247, 1253 (Fed. Cir. 2004) 

(quoting PPG Indus., Inc. v. Guardian Indus., Corp., 75 

F.3d 1558, 1564 (Fed. Cir. 1996)). For example, the fact 

that a clinician’s involvement may be necessary to determine effective amounts of the single compound effervescent agent and its corresponding soluble acid source does 

not itself constitute undue experimentation. See OrthoMcNeil Pharm., Inc. v. Mylan Labs., Inc., 520 F.3d 1358, 

1365–66 (Fed. Cir. 2008) (“[E]ven if clinical trials informed the anticonvulsively effective amount, this record 

does not show that extensive or ‘undue’ tests would be 

required to practice the invention.”). In addition, extensive experimentation does not necessarily render the 

experiments unduly extensive where the experiments 

involve repetition of known or commonly used techniques. 

See Johns Hopkins Univ. v. CellPro, Inc., 152 F.3d 1342, 

1360 (Fed. Cir. 1998) (finding that the difficulty in producing certain antibodies could not be attributed to the 

shortcomings in the disclosure of the patent at issue, but 

rather, the difficulty was attributed to the technique 

commonly used during experimentation that generally 

required repetition). Thus, the focus “is not merely quantitative, since a considerable amount of experimentation 

is permissible, if it is merely routine, or if the specification 

in question provides a reasonable amount of guidance . . . 

.” PPG Indus., Inc., 75 F.3d at 1564 (citation and quotation omitted). 

Permissible experimentation is, nevertheless, not 

without bounds. This court has held that experimentation was unreasonable, for example, where it was found 

that eighteen months to two years’ work was required to 

practice the patented invention. See, e.g., White Consol. 

Indus., Inc. v. Vega Servo-Control, Inc., 713 F.2d 788, 791 

(Fed. Cir. 1983). Likewise, we have held that the amount 

of experimentation would be undue where: (1) the specifi-
15 CEPHALON v. WATSON PHARMA

cation lacks guidance by teaching away from the subject 

matter that was eventually claimed; and (2) there is 

evidence of the patentee’s own failures to make and use 

the later claimed invention at the time of the application. 

See, e.g., AK Steel Corp. v. Sollac, 344 F.3d 1234, 1244 

(Fed. Cir. 2003). Hence, the mere potential need for 

clinical work, without more, is not dispositive in this case. 

Rather, Watson had the burden to show by way of testimony or documentary evidence the amount of experimentation needed to calculate a formulation for coadministering a soluble acid source in one form of dosage 

with a carbonate source in another form to achieve the 

claimed effervescent reaction. See Moba, B.V. v. Diamond 

Automation, Inc., 325 F.3d 1306, 1321 (Fed. Cir. 2003) 

(finding that there was no record evidence recounting the 

amount of experimentation one of skill in the art would 

require to develop the claimed invention based on the 

patent’s disclosure). As Cephalon avers, the Khankari 

patents describe multiple embodiments using effervescent 

formulations for fentanyl citrate (acid) alongside different 

amounts of sodium carbonate (base). Nonetheless, Watson has not presented evidence showing why these formulations for a “couple” do not provide sufficient guidance for 

a skilled artisan to calculate formulations for single 

compound effervescent agents. See United States v. Telectronics, Inc., 857 F.2d 778, 786 (Fed. Cir. 1988) (“Since 

one embodiment is admittedly disclosed in the specification, along with the general manner in which its current 

range was ascertained, we are convinced that other permutations of the invention could be practiced by those 

skilled in the art without undue experimentation.”). Nor 

does Watson show that the resulting experimentation in 

this case would be excessive, e.g., that it would involve 

testing for an unreasonable length of time. See White 

Consol. Indus., Inc., 713 F.2d at 791. Unsubstantiated 

statements indicating that experimentation would be 
CEPHALON v. WATSON PHARMA 16

“difficult” and “complicated” are not sufficient. In light of 

the lack of evidence on the record of undue experimentation, the district court erred as a matter of law in holding 

that Watson proved its case on enablement by clear and 

convincing evidence.10 

Watson had the burden of proof to show that the 

Khankari patents lacked enabling disclosures. Watson

failed to carry its burden.11 The evidence on the record 

does not sufficiently show that the experimentation 

10 The district court also predicated its decision 

on the inventors’ testimony that they could not “name any 

single-compound effervescent on the stand” and that they 

were “only in possession of a method for creating effervescence using a formulation containing both an acid and a 

base.” Cephalon, 769 F. Supp. 2d at 751. These statements nevertheless do not contradict the fact that the 

record lacks evidence directed to whether the experimentation necessary would be unduly extensive. Accordingly, 

they carry little probative value here. 11 The district court focused on the evidence 

Watson presented on enablement—Dr. Mumper’s testimony. As the district court acknowledged, Dr. “Mumper 

did not specifically analyze many of the Wands factors at 

trial.” Cephalon, 769 F. Supp. 2d at 752 n. 29. Rather, Dr. 

Mumper’s testimony was limited to the opinion that the 

necessary experimentation would be “difficult” and “complicated.” Nevertheless, the district court mentions that 

“there is no genuine question as to the lack of direction or 

guidance (on co-administration) in the patent or the 

absence of working examples (factors 2 and 3).” Id. The 

district court also states that “[t]he nature of the invention, state of the art, relative skill in the art and claim 

scope (factors 4 to 7) were addressed by Watson within 

the context of its obviousness arguments and Markman

briefing.” Id. Although analysis of the Wands factors is 

instructive, the district court’s cursory consideration of 

these factors is not dispositive in this case. Even assuming the district court’s findings were accurate, the record 

still lacks evidence of undue experimentation. 

 
17 CEPHALON v. WATSON PHARMA

necessary to co-administer a soluble acid source with a 

single compound effervescent agent would be unduly 

extensive. Thus, we reverse the district court’s nonenablement determination.

B. The District Court Did Not Clearly Err in Finding

Noninfringement of the Khankari Patents

Infringement is a question of fact that, after a bench 

trial, we review for clear error. Alza Corp. v. Mylan Labs., 

Inc., 464 F.3d 1286, 1289 (Fed. Cir. 2006). A factual 

finding is clearly erroneous when, despite some supporting evidence, we are left with a definite and firm conviction that the district court was in error. Id. To prove 

infringement, the patentee must show that an accused 

product embodies all limitations of the claim either literally or by the doctrine of equivalents. TIP Sys., LLC v. 

Phillips & Brooks/Gladwin, Inc., 529 F.3d 1364, 1379 

(Fed. Cir. 2008); see also Tech. Licensing Corp. v. Videotek, Inc., 545 F.3d 1316, 1327 (Fed. Cir. 2008) (stating 

that, to prove infringement, the patentee has the burden 

of persuasion by a preponderance of the evidence). If any 

claim limitation is absent from the accused device, there 

is no literal infringement as a matter of law. TIP Sys., 529 

F.3d at 1379. 

To support a finding of infringement under the doctrine of equivalents, a patentee must provide particularized testimony and linking argument with respect to the 

“function, way, result” test. Tex. Instruments Inc. v. 

Cypress Semiconductor Corp., 90 F.3d 1558, 1566–67 

(Fed. Cir. 1996). The “essential inquiry” in any determination under the equivalents doctrine is whether “the 

accused product or process contain[s] elements identical 

or equivalent to each claimed element of the patented 

invention.” Warner-Jenkinson Co., Inc. v. Hilton Davis 

Chem. Co., 520 U.S. 17, 40 (1997). We have assessed the 

insubstantiality of an alleged equivalent by applying the 
CEPHALON v. WATSON PHARMA 18

function-way-result test as set forth in Union Paper–Bag 

Machine Co. v. Murphy, 97 U.S. 120, 125 (1877), which 

asks whether an element of an accused product “performs 

substantially the same function in substantially the same 

way to obtain the same result” as an element of the patented invention. See, e.g., TIP Sys., 529 F.3d at 1376. 

With respect to the disputed limitation, “at least one 

[saliva activated] effervescent agent in an amount sufficient to increase absorption . . . across [the] oral mucosa,” 

the district court found Cephalon failed to prove that 

Watson’s ANDA products meet this limitation. Cephalon, 

769 F. Supp. 2d at 748 (brackets in original). Significantly, the district court’s construction of this limitation

required that the effervescent agent is “saliva activated,” 

and the parties’ dispute centered on whether potassium 

bicarbonate and mannitol in the ANDA products reacted 

to generate an effervescent reaction. Id. at 743, 748. In 

particular, the district court noted that Cephalon’s expert, 

Dr. Bernard Olsen, testified that he conducted pH experiments on the ANDA products and found mannitol to be 

acidic in water; the more concentrated the mannitol, the 

more acidic the solution. Id. at 748. The district court 

however found that Cephalon presented no evidence 

regarding the acidity of mannitol in artificial saliva—that 

there is no evidence of record regarding the properties of 

human saliva and how, for example, mannitol may react 

in it. Id. 

Cephalon argues that it focused on water and not saliva because the Khankari patents explicitly state that 

the preferred effervescent agents evolve gas upon exposure to water and/or to saliva. Cephalon also argues that 

at various points during the course of litigation Watson

represented that the reaction required of the effervescent 

agent may occur in either saliva or in water. The district 

court nevertheless credited Dr. Mumper, Watson’s expert, 

who concluded that: 
19 CEPHALON v. WATSON PHARMA

I looked at Dr. Olsen’s data of mannitol in water 

where he showed that increasing concentrations of 

mannitol in water led to a correspondingly decrease in pH. And I think the important point 

that I’ll make on here is that . . . it’s in water. 

And so what Dr. Olsen has showed is that mannitol is acidic in water; and Dr. Williams asserts 

that mannitol is therefore the acidic agent and is 

reacting with potassium bicarbonate. I think the 

important piece of information that is missing [in 

this case] is what the potential or alleged acidity 

of mannitol in either artificial saliva or, even more 

important, in the human mouth . . . and there is 

no evidence that mannitol would be acidic under 

those conditions.” 

J.A. 6335, 1174:1–16. Cephalon does not dispute this fact, 

and we find no clear error in the district court’s finding of 

noninfringement based on Watson’s expert testimony. 

Therefore, Cephalon has failed to prove that this limitation is practiced by the ANDA product, either literally or 

under the doctrine of equivalents. Because Cephalon has 

failed to prove the ANDA products infringe the “at least 

one [saliva activated] effervescent agent . . .” limitation, 

we need not discuss the remaining disputed limitations. 

Accordingly, the district court’s noninfringement finding 

is affirmed. 

III.

Because this court concludes that Watson failed to 

prove by clear and convincing evidence that the Khankari 

patents—covering a dosage form having a single compound effervescent agent—were invalid for lack enablement, we reverse that portion of the district court’s 

decision. As to the district court’s finding of noninfringement, we affirm. 

REVERSED–IN–PART and AFFIRMED–IN–PART
CEPHALON v. WATSON PHARMA 20

Each party shall bear its own costs.