United States Court of Appeals 

for the Federal Circuit ______________________ 

GILEAD SCIENCES, INC.,

Plaintiff-Cross-Appellant

v.

MERCK & CO., INC., MERCK SHARP & DOHME 

CORP., IONIS PHARMACEUTICALS, INC.,

Defendants-Appellants

______________________ 

2016-2302, 2016-2615

______________________ 

Appeals from the United States District Court for the 

Northern District of California in No. 5:13-cv-04057-BLF, 

Judge Beth Labson Freeman.

______________________ 

Decided: April 25, 2018 

______________________ 

 JUANITA ROSE BROOKS, Fish & Richardson, PC, San 

Diego, CA, argued for plaintiff-cross-appellant. Also 

represented by CRAIG E. COUNTRYMAN, JONATHAN ELLIOT 

SINGER; ELIZABETH M. FLANAGAN, DEANNA JEAN REICHEL, 

Minneapolis, MN; ROBERT M. OAKES, Wilmington, DE;

EDMUND HIRSCHFELD, E. JOSHUA ROSENKRANZ, Orrick, 

Herrington & Sutcliffe LLP, New York, NY.

 JEFFREY A. LAMKEN, MoloLamken LLP, Washington, 

DC, argued for defendants-appellants. Also represented 

by JAMES A. BARTA, SARAH JUSTINE NEWMAN, MICHAEL 
2 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

GREGORY PATTILLO, JR.; SARA MARGOLIS, New York, NY; 

JESSAMYN SHELI BERNIKER, STANLEY E. FISHER, BRUCE 

GENDERSON, JESSICA PALMER RYEN, Williams & Connolly 

LLP, Washington, DC; MITCHELL EPNER, STEPHEN S.

RABINOWITZ, Hughes Hubbard & Reed LLP, New York, 

NY.

______________________ 

Before TARANTO, CLEVENGER, and CHEN, Circuit Judges.

TARANTO, Circuit Judge. 

This case involves two patents relating to treatments 

for Hepatitis C. Merck & Co., Inc. and Ionis Pharmaceuticals, Inc. (formerly Isis Pharmaceuticals, Inc.) collaborated on research in the area and eventually obtained 

U.S. Patent Nos. 7,105,499 and 8,481,712. The patents, 

whose specifications are materially the same for present 

purposes, describe and claim classes of compounds, identified by structural formulas, and the administration of 

therapeutically effective amounts of such compounds. 

Gilead Sciences, Inc., developed its own Hepatitis C 

treatments—marketed now as Solvadi® and Harvoni®, 

both based on the compound sofosbuvir. 

Gilead filed this action against Merck & Co., its subsidiary Merck Sharp & Dohme Corp., and Ionis (collectively, “Merck” unless the context indicates reference just 

to Merck & Co. and/or Merck Sharp). Gilead sought a 

declaratory judgment that Merck’s ’499 and ’712 patents 

are invalid and that Gilead is not infringing by its activities involving its sofosbuvir products. Merck counterclaimed for infringement.

Gilead eventually stipulated to infringement based on 

the district court’s claim construction, which is not challenged on appeal. A jury trial was held on Gilead’s challenges to the patents as invalid for lack of both an 

adequate written description and enablement of the 

asserted claims (claims 1–2 of the ’499 patent and claims 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 3

1–3, 5, 7, and 9-11 of the ’712 patent) as well as Gilead’s 

closely related defense that Merck did not actually invent 

the subject matter but derived it from another inventor, 

employed by Gilead’s predecessor. The jury ruled for 

Merck and awarded damages.

The district court then held a bench trial on Gilead’s 

equitable defenses, including unenforceability against 

Gilead based on the allegation that Merck had unclean 

hands regarding the patents. The district court ruled for 

Gilead, finding both pre-litigation business misconduct 

and litigation misconduct attributable to Merck, and it 

barred Merck from asserting the patents against Gilead. 

Gilead Scis., Inc. v. Merck & Co., No. 13-cv-04057-BLF, 

2016 WL 3143943, at *39 (N.D. Cal. June 6, 2016). Having so concluded, the district court subsequently deemed 

moot Gilead’s motion for judgment as a matter of law of 

invalidity for lack of adequate written description and 

enablement. The court also awarded attorney’s fees, 

relying on the finding of unclean hands.

Merck appeals the unenforceability judgment based 

on unclean hands. Gilead cross-appeals the denial of 

judgment as a matter of law of invalidity, but it asks us to 

reach that issue only if we set aside the unenforceability 

judgment. We have jurisdiction under 28 U.S.C. 

§ 1295(a)(1). We affirm the judgment based on unclean 

hands, concluding that it is sufficiently supported by 

findings that withstand review for clear error. We therefore do not reach the issues raised by Gilead’s conditional 

cross-appeal. 

I 

A 

In 1998, Merck and Isis began collaborating on finding a way to block propagation of the Hepatitis C virus 

(HCV) by impeding the synthesis of its RNA. J.A. 20291. 

The collaborators sought a molecule that would have two 
4 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

properties. First, an enzyme involved in RNA assembly 

(NS5B polymerase) would recognize the molecule as a 

building block and add it to the growing RNA chain 

during replication of the virus’s RNA. Second, the addition of this molecule would effectively stop further RNA 

assembly before completion and, hence, end RNA replication and prevent viral propagation.

Starting in 2001, the two collaborators filed a series of 

patent applications related to antiviral agents for Hepatitis C. Dr. Phillipe Durette, a Merck chemist who had 

become a patent attorney, was central to their initial 

patenting efforts. J.A. 20301. A provisional patent application dated January 22, 2001, summarizes the invention 

as “a method for inhibiting hepatitis C virus (HCV) NS5B 

polymerase, a method for inhibiting HCV replication, 

and/or a method for treating HIV infection” by administering a “therapeutically effective amount of a compound 

of structural formula I.” J.A. 25808. It sets forth and 

claims large families of possible structures in Markush 

format: it displays a number of configurations of nucleic 

acid derivatives and shows variables at a number of 

locations in the structures (e.g., different bases, different 

molecules attached to the sugar ring), the variables each 

stated to represent any of a substantial number of possible constituents. J.A. 25803–980.

The same is true of Merck’s two January 2002 applications under the Patent Cooperation Treaty (PCT applications). J.A. 24832, 26913. One of those became Merck’s 

July 2003 U.S. application 10/250,873, which issued as 

the ’499 patent. J.A. 150, 27227. A non-provisional U.S. 

application filed in January 2002 led to the 2007 application that issued as the ’712 patent. J.A. 223. The number 

of possible combinations within the Markush groups is 

very large. 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 5

One instance of the formulas in the written description, from the 2003 application that issued as the ’499 

patent, is: 

structural formula III which is of the stereochemical configuration: 

wherein B is 

D is N, CH, C—CN, C—NO2, C—C1-3 alkyl, C—

NHCONH2, C—CONR11R11, C—CSNR11R11, 

C—COOR11, C-hydroxy, C—C1-3 alkoxy, Camino, C—C1-4 alkylamino, C-di(C1-4 alkyl)amino, C-halogen, C-(1,3-6oxazol-2-yl), C-

(1,3-thiazol-2-yl), or C-(imidazol-2-yl); wherein 

alkyl is unsubstituted or substituted with one 

to three groups independently selected from 

halogen, amino, hydroxy, carboxy, and

C1-3 alkoxy;

W is O or S;

Y is H, C1-10 alkylcarbonyl, P3O9H4, P2O6H3, or 

P(O)R9R10; 

R1 is hydrogen, CF3, or C1-4 alkyl and one of R2 

and R3 is OH or C1-4 alkoxy and the other of R2 

and R3 is selected from the group consisting of 
6 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

hydrogen,

hydroxy,

fluoro, 

C1-3 alkyl,

trifluoromethyl, 

C1-8 alkylcarbonyloxy,

C1-3 alkoxy, and

amino; or

R2 is hydrogen, CF3, or C1-4 alkyl and one of R1 and 

R3 is OH or C1-4 alkoxy and the other of R1 and R3 

is selected from the group consisting of 

hydrogen,

hydroxy,

fluoro, 

C1-3 alkyl,

trifluoromethyl, 

C1-8 alkylcarbonyloxy,

C1-3 alkoxy, and

amino; or

R1 and R2 together with the carbon atom to which 

they are attached form a 3- to 6-membered 

saturated monocyclic ring system optionally 

containing a heteroatom selected from O, S, 

and NC0-4 alkyl;

R6 is H, OH, SH, NH2, C1-4 alkylamino, di(C1-4 alkyl)amino, C3-6 cycloalkylamino, halogen, C1-4 

alkyl, C1-4 alkoxy, or CF3; 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 7

R5 is H, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-4 

alkylamino, CF3, or halogen;

R7 is hydrogen, amino, C1-4 alkylamino, C3-6 cycloalkylamino, or di(C1-4 alkyl)amino;

each R11 is independently H or C1-6 alkyl;

R8 is H, halogen, CN, carboxy, C1-4 alkyloxycarbonyl, N3, amino, C1-4 alkylamino, di(C1-4 alkyl)amino, hydroxy, C1-6 alkoxy, C1-6 alkylthio, 

C1-6 alkylsulfonyl, or (C1-4 alkyl)0-2 aminomethyl; and

R9 and R10 are each independently hydroxy, 

OCH2CH2SC(═O)t-butyl, or OCH2O(C═O)iPr;

with the provisos that (a) when R1 is hydrogen and 

R2 is fluoro, then R3 is not hydrogen, trifluoromethyl, fluoro, C1-3 alkyl, amino, or C1-3 

alkoxy; (b) when R1 is hydrogen and R2 is fluoro, hydroxy, or C1-3 alkoxy, then R3 is not hydrogen or fluoro; and (c) when R1 is hydrogen 

and R2 is hydroxy, then R3 is not β-hydroxy.

’499 Patent, col. 13, line 5 through col. 14, line 17 (emphases added to highlight terms of particular interest for this 

case); J.A. 27245–47.1 

Various claims appeared in Merck’s patent applications based on that structural formula or related ones, 

including claims 6 and 8 of the January 2001 provisional, 

J.A. 25954–56, claims 6 and 8 of the PCT application that 

 

1 The top figure shows the key elements of the nucleoside. B is the base, shown in the next two figures in 

single-ring (pyrimidine) and double-ring (purine) versions. 

R1 and R2 are located at the 2′ (carbon) position on the 

ring, with R1 at the 2′ “up” location and R2 at the 2′ 

“down” location. R3 is at the 3′ position. 
8 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

issued as the ’499 patent, J.A. 25036–38, and claim 44 of 

that same application, which was added, substituting for 

earlier claims, immediately upon filing the U.S. version in 

July 2003, J.A. 27482–83. The 2003-added claim 44 of the 

2003 application, for example, recites the above structural 

formula but is limited to the single-ring bases shown 

above (pyrimidine bases, such as cytosine and uracil). It

therefore omits the above-quoted language concerning D, 

R7, and R8, which appear only on the double-ring bases 

shown above (purine bases, such as adenine and guanine). 

Id.

Claim 44 of the 2003 application and its PCT counterpart, like the structural formula III, encompasses, among 

the large number of possible combinations of values of the 

variables, structures having (i) a single-ring base, (ii) a 

methyl (C1 alkyl) in the R1 position, and (iii) a fluoro in 

the R2 or R3 position. J.A. 25036–38, 27482–83. A subgenus with those characteristics—which embraces both a 

metabolite of Gilead’s sofosbuvir and an earlier identified

compound that was modified to arrive at sofosbuvir, and 

which Merck eventually focused on in new claims in 

2005—is central in this case.

B 

In 2002, a pharmaceutical company called Pharmasset, which was later acquired by Gilead, was researching 

Hepatitis C treatments. When one of Merck’s early 

applications was published that year, Pharmasset reviewed the application, looking for “loopholes.” J.A. 20048

(533). After reviewing Merck’s application, Jeremy Clark, 

a chemist at Pharmasset, proposed the compound PSI6130 (the compound that led to sofosbuvir). Id. (533–534). 

PSI-6130 had a single-ring base (cytosine), a methyl in 

the 2′ up position, and a fluoro in the 2′ down position. 

J.A. 24619, 24826. Pharmasset synthesized and tested 

PSI-6130 by May 2003. J.A. 20040 (504). It was the first 

compound made by Pharmasset that was active against 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 9

Hepatitis C. J.A. 20050–51 (544–45). PSI-6130 led to 

sofosbuvir, which has the same methyl and fluoro substituents as PSI-6130 but contains uracil, rather than 

cytosine, as its base. J.A. 19913–17, 19951 (401). 

Pharmasset filed a patent application for Mr. Clark’s 

invention in May 2003. J.A. 20042 (511–12). The application was published in January 2005. The published 

application, the “Clark Application,” described and 

claimed (in 129 claims) a range of structures, including 

both single-ring (pyrimidine) and double-ring (purine) 

bases, and methods of using them for treatment of various 

conditions, including Hepatitis C. J.A. 23709–86. Among 

the many specifically described and claimed structures 

was PSI-6130. J.A. 23727 (application ¶ 168), 23756 

(claim 26). The application issued in September 2008 as 

U.S. Patent No. 7,429,572, with only 19 claims, which 

cover PSI-6130. J.A. 29947–87. 

C 

In February 2005, the month after the January 2005 

publication of the Clark Application, Merck, through Dr. 

Durette, filed a narrowing amendment in the 2003 application that eventually issued as the ’499 patent. J.A. 

28318–21. Merck canceled all pending claims and substituted two narrower claims (claims 53 and 54). The claims 

issued as claims 1 and 2 of the ’499 patent on September 

12, 2006. 

Claim 1 of the ’499 patent is representative. It states: 

1. A method of treating hepatitis C virus (HCV) 

infection comprising administering to a mammal 

in need of such treatment a therapeutically effective amount of a compound of structural formula 

III, or a pharmaceutically acceptable salt or acyl 

derivatives thereof, 
10 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

wherein B is 

W is O or S; 

Y is H, C1-10 alkylcarbonyl, P3O9H4, P2O6H3, or 

P(O)R9R10; 

R1 is CF3, or C1-4 alkyl and one of R2 and R3 is OH 

or C1-4 alkoxy and the other of R2 and R3 is 

fluoro; 

R6 is H, OH, SH, NH2, C1-4 alkylamino, di(C1-4 alkyl)amino, C3-6 cycloalkylamino, halogen, C1-4 

alkyl, C1-4 alkoxy, or CF3; 

R5 is H, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-4 

alkylamino, CF3, or halogen; and 

R9 and R10 are each independently hydroxy, 

OCH2CH2SC(═O)t-butyl, or OCH2O(C═O)iPr. 

’499 Patent, col. 137, line 2 through col. 138, line 16.

Merck seems to accept that the ’499 patent claims include 

PSI-6130. Merck Br. 18. Gilead characterizes the claim 

as “target[ing]” PSI-6130. Gilead Br. 16, 18.

We will elaborate below on the connection of Pharmasset’s work on PSI-6130 with Dr. Durette, Merck, and 

Merck’s 2005 claim amendments for what became the ’499 

patent. Those connections, together with Dr. Durette’s 

eventual testimony about those connections, came to be

the basis of the district court’s ultimate determination 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 11

that Merck had unclean hands, precluding patent enforcement against Gilead. 

D

In February 2007, a few months after the ’499 patent 

issued, Merck’s Dr. Durette filed the application that 

ultimately issued as the ’712 patent. J.A. 24147. The 

original claims of that application were quite different 

from PSI-6130, J.A. 24336–41, and Dr. Durette immediately substituted two claims that were closer, but that the 

parties here do not contend covered PSI-6130, J.A. 24150–

53. It appears undisputed that after April 2007 Dr. 

Durette did not participate in prosecuting the ’712 application. Merck Br. 18; see e.g., J.A. 24369–70 (April 2007 

filing by the attorney who took over responsibility for 

prosecuting the application from Dr. Durette). 

In 2010, Pharmasset published an article in the Journal of Medicinal Chemistry describing “sofosbuvir” (PSI7977) to treat HCV. J.A. 31990–2007. In 2011, attorney 

Jeffrey Bergman took over prosecuting the ’712 application for Merck. J.A. 32383. Merck amended the ’712 

application to include new claims. J.A. 24394–410. The 

’712 patent issued on July 9, 2013.

Claim 1 of the ’712 patent is representative. It states: 

1. A compound having the formula:

or a pharmaceutically acceptable salt thereof,

wherein: 

B is: 
12 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

L is CH or N;

E is N or CR5; 

W is O or S;

R1 is C2-4 alkenyl, C2-4 alkynyl, or C1-4 alkyl optionally substituted with amino, hydroxy, or 1 to 3 

fluorine atoms; R3 is hydroxy or C1-4 alkoxy; 

and R2 is selected from the group consisting of 

halogen,

C1-4 alkyl, optionally substituted with 1 to 3 

fluorine atoms,

C1-10 alkoxy, optionally substituted with C1-3 

alkoxy or 1 to 3 fluorine atoms,

C2-6 alkenyloxy, 

C1-4 alkylthio,

C1-8 alkylcarbonyloxy,

aryloxycarbonyl,

azido,

amino,

C1-4 alkylamino, and

di(C1-4 alkyl)amino;

R4 and R6 are each independently H, OH, SH, 

NH2, C1-4 alkylamino, di(C1-4 alkyl)amino, C3-6 

cycloalkylamino, halogen, C1-4 alkyl, C1-4 

alkoxy, or CF3; 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 13

R5 is H, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-4 

alkylamino, CF3, or halogen;

R12 and R13 are each independently hydrogen or 

methyl.

’712 Patent, col. 143, lines 2–54. The parties characterize 

these claims, which embrace a single-ring base with 

methyl up and fluoro down at the 2′ position in the sugar, 

as covering metabolites of sofosbuvir, produced in the 

body after administration of sofosbuvir. Merck Br. 18; 

Gilead Br. 19. As noted above, in this case Gilead ultimately stipulated to infringement of the asserted claims 

of the ’712 and ’499 patents based on the district court’s 

claim construction. 

II

After a bench trial on Gilead’s equitable defenses, the 

district court held that Merck could not enforce the two 

patents at issue here against Gilead because its conduct 

gave it unclean hands. Gilead, 2016 WL 3143943, at *39. 

The court rested that determination on its findings of 

both pre-litigation business misconduct and litigation 

misconduct attributable to Merck. Id. at *27. The court 

balanced the equities and applied its determination to 

both patents. Id. at *37–39. 

The Supreme Court has articulated the governing legal standard. In Keystone Driller Co. v. General Excavator Co., the Court explained that a determination of 

unclean hands may be reached when “misconduct” of a 

party seeking relief “has immediate and necessary relation to the equity that he seeks in respect of the matter in 

litigation,” i.e., “for such violations of conscience as in 

some measure affect the equitable relations between the 

parties in respect of something brought before the court.” 

290 U.S. 240, 245 (1933). In Precision Instrument Manufacturing Co. v. Automotive Maintenance Machinery Co., 

the Court stated that the doctrine “closes the doors of a 
14 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

court of equity to one tainted with inequitableness or bad 

faith relative to the matter in which he seeks relief, 

however improper may have been the behavior of the 

defendant,” and requires that claimants “have acted fairly 

and without fraud or deceit as to the controversy in issue.” 324 U.S. 806, 814–15 (1945). The Court added that 

the doctrine “necessarily gives wide range to the equity 

court’s use of discretion in refusing to aid the unclean 

litigant.” Id. at 815; see also Northbay Wellness Grp., Inc. 

v. Beyries, 789 F.3d 956, 960 (9th Cir. 2015) (explaining 

need for equitable balancing).2 

Merck invokes the term “material” to describe the 

kind of connection between misconduct and the litigation 

that the Supreme Court’s formulations require. But 

Merck has not identified how that term helpfully refines 

the Supreme Court’s standard in a way that is relevant to 

this case. See Merck Br. 39–43. For purposes of this case, 

which involves clear misconduct in breaching commitments to a third party and clear misconduct in litigation, 

the “immediate and necessary relation” standard, in its 

natural meaning, generally must be met if the conduct 

normally would enhance the claimant’s position regarding 

legal rights that are important to the litigation if the 

impropriety is not discovered and corrected. Merck cites 

no authority holding such misconduct to be outside Keystone’s scope. Nor does Merck deny that the standard can 

cover at least some misconduct that ultimately fails to 

affect the litigation, as when it is discovered before it 

 

2 The doctrine of unclean hands is not patentspecific, but its application to patents has some distinctive 

features affecting the patent system. We need not choose 

between Ninth Circuit and Federal Circuit law on the 

subject here. The parties have identified no differences 

pertinent to this case, and they have not identified what 

law they contend controls in this appeal. 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 15

bears fruit, as long as its objective potential to have done 

so is sufficient. 

Significantly, this is not a case in which it is clear that

the identified misconduct could not reasonably have 

enhanced the claimant’s legal position as to either the 

creation or the enforcement of the legal rights at issue. 

Nor is this a case involving alleged deficiencies in communications with the PTO during patent prosecution, for 

which this court’s inequitable-conduct decisions, e.g., 

Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 

1276 (Fed. Cir. 2011) (en banc), set important limits on 

conclusions of unenforceability through that doctrine.3 In 

the circumstances present in this case, we see no genuine 

issue about the governing legal standard, but only its 

application. 

We conclude that the district court made findings that 

have adequate support in the evidence and that, taken 

together, justify the equitable determination of unclean 

hands as a defense to enforcement in this case. In so 

concluding, we apply deferential standards of review, as 

Merck itself urges. We review the district court’s ruling 

for abuse of discretion, which means that we review 

factual findings only for clear error. See Merck Br. 37 

(citing Northbay, 789 F.3d at 959). 

Our decision rests only on the totality of the evidencesupported misconduct we summarize, not individual 

elements alone and not every finding of the district court. 

We are conscious, as any court presented with a defense 

 

3 We therefore have no occasion in this case to consider issues that may arise in seeking to ensure that the 

unclean-hands doctrine operates in harmony with, and 

does not override, this court’s inequitable-conduct standards governing unenforceability challenges based on 

prosecution communications with the PTO.
16 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

of unclean hands must be, both of the judicial system’s 

vital commitment to the standards of probity protected by 

the doctrine and, also, of the potential for misuse of this

necessarily flexible doctrine by parties who would prefer 

to divert attention away from dry, technical, and complex 

merits issues toward allegations of misconduct based on 

relatively commonplace disputes over credibility. Having 

those considerations in mind, we do not find a sufficient 

basis to set aside the district court’s determination of 

unclean hands under the applicable deferential standard

of review. 

A 

The district court found, with adequate evidentiary

support, two related forms of pre-litigation business 

misconduct attributable to Merck. First, Dr. Durette 

learned of Pharmasset’s PSI-6130 structure by participating, at Merck’s behest, in a conference call with Pharmasset representatives, violating a clear “firewall” 

understanding between Pharmasset and Merck that call 

participants not be involved in related Merck patent 

prosecutions. Second, Merck continued to use Dr. Durette 

in the related patent prosecutions even after the call. The 

district court also found, with adequate evidentiary 

support, a direct connection to the ultimate patent litigation involving sofosbuvir. Thus, Dr. Durette’s knowledge 

of PSI-6130, acquired improperly, influenced Merck’s 

filing of narrowed claims, a filing that held the potential 

for expediting patent issuance and for lowering certain 

invalidity risks. Those findings establish serious misconduct, violating clear standards of probity in the circumstances, that led to the acquisition of the less risky ’499 

patent and, thus, was immediately and necessarily related to the equity of giving Merck the relief of patent enforcement it seeks in this litigation.
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 17

1 

The business misconduct found in this case grows out 

of Merck’s dealings with Pharmasset. In the early 2000s, 

the two companies discussed possible business arrangements that would include work on “discovery and development of antiviral agents against . . . hepatitis C virus.” 

Gilead, 2016 WL 3143943, at * 6. They entered into a 

non-disclosure agreement in January 2001. Id. 

In September 2003, Pharmasset gave Merck certain 

information about Pharmasset’s NS5B Nucleoside Inhibitor, i.e., PSI-6130. Id.; J.A. 32161–81. In October 2003, 

the companies signed a Material Transfer Agreement 

under which Pharmasset would give Merck the “Pharmasset HCV NS5B Nucleoside Inhibitor” for Merck to 

evaluate. Gilead, 2016 WL 3143943, at *7; J.A. 30077–83. 

The Agreement allowed Merck to test PSI-6130 as long as 

it did not try to discern the compound’s chemical structure. Gilead, 2016 WL 3143943, at *7; J.A. 30078 ¶ 3.1. 

In January 2004, Merck asked Pharmasset to furnish 

more information to a “firewalled” Merck medicinal 

chemist—meaning that the chemist was “firewalled” from 

Merck’s own Hepatitis C program. Gilead, 2016 WL 

3143943, at *7–8; J.A. 32183–86. Pharmasset agreed to 

provide information to Merck’s chemist, Dr. Ashton, on 

the conditions that the information was subject to the 

2001 non-disclosure agreement and, what is critical here, 

that it was to be shared only on a “‘fire walled’ basis.” 

J.A. 22921–22; Gilead, 2016 WL 3143943, at *7–8. In 

February 2004, Merck’s “firewalled” chemist determined

that “PSI6130 and its relatives represent a potentially 

good fit with Merck’s existing anti-HCV portfolio arising 

from the Isis collaboration.” J.A. 22918–19. 

Merck and Pharmasset then scheduled, for March 17, 

2004, a conference call during which Pharmasset would 

disclose the structure of PSI-6130. J.A. 23706–07; see 

Gilead, 2016 WL 3143943, at *8. Merck planned to have 
18 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

Dr. Durette, Merck’s patent prosecutor for what became 

the ’499 patent, “view the structure” during the call. J.A. 

23706–07; Gilead, 2016 WL 3143943, at *8; see also J.A. 

19945 (375) (Dr. Durette’s supervisor asked him to participate in the call). The district court found that Dr. Durette knew before the call “that any information he 

learned about Pharmasset’s PSI-6130 nucleoside analog 

compound would overlap with the subject matter of his 

patent prosecution docket for Merck, thereby creating a 

conflict.” Gilead, 2016 WL 3143943, at *9. 

On the March 17, 2004 call, before disclosing the compound’s structure, Pharmasset confirmed the importance 

of the firewall to it by asking whether the two participating Merck employees (Dr. Durette and Dr. Pon) were 

within the firewall separating Merck call participants 

from related Merck HCV patenting efforts. Id.; J.A. 

31544–45; J.A. 19947 (382). At some point in the call, the 

Merck participants said that they were within the firewall. Gilead, 2016 WL 3143943, at *9–10; J.A. 31544–45; 

J.A. 19960 (435). Pharmasset’s notes from the call, however, also indicate some disclosure by Dr. Durette of a 

conflict issue for him: “It’s a problem for Phil Durette; he 

needs to have a conversation with his supervisor; ‘seems 

quite related to things that I’m involved with.’ . . . [H]e is 

personally conflicted; not the company.” J.A. 31545; see

Gilead, 2016 WL 3143943, at *9–10. The PSI-6130 structure was disclosed during the call. Id. at *9.

After the March 17, 2004 call, Dr. Durette stopped 

participating in the work of the Merck team dealing with 

Pharmasset. J.A. 19944 (373). But Merck kept him 

working as the prosecuting attorney for its patent applications related to nucleosides that inhibit Hepatitis C 

virus replication. Gilead, 2016 WL 3143943, at *10 

(“Instead of withdrawing from prosecution, Dr. Durette 

continued to prosecute Merck’s HCV patent applications 

and write new claims that targeted Pharmasset’s work.”). 

The court found that neither Merck nor Dr. Durette 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 19

provided any explanation as to why he was not removed 

from further prosecution of the Merck patent applications. 

Id.

Those facts support the district court’s findings of serious business misconduct. Merck sent Dr. Durette to 

participate in the March 2004 call despite the clear firewall and the fact that “Merck . . . knew that Pharmasset’s 

compound was an NS5B polymerase inhibitor just like its 

own compounds from the Merck-Isis collaboration.” Id. at 

*28. “Dr. Durette’s involvement with Merck’s HCV patents violated the understanding the parties had about 

their firewall obligations, which excluded anyone involved 

with Merck’s internal HCV program.” Id. And after the 

call, it was “wrong for Merck to allow Dr. Durette to 

continue to prosecute” the Merck applications: he continued prosecution of the application that became the ’499 

patent, and in 2007 he filed (and immediately amended) 

the application that became the ’712 patent. Id.4

 

4 The court added that Merck’s own “corporate policy forb[ade] Merck’s patent prosecutors from participating 

in licensing discussions in an area related to their prosecution work.” Id. at *9 (citing J.A. 22341 (38–39)); see id.

at *28; J.A. 22374 (170–71). That policy, as we note 

below, confirms the connection between (a) Merck’s patent 

prosecutor learning the structure of PSI-6130 during the 

March 2004 call and (b) Merck’s patenting and the resulting litigation. To the extent that the district court suggested that the violation of Merck’s internal policy was an 

independent basis for finding wrongful conduct, even 

apart from the violation of the firewall understanding, we 

see no basis for such a suggestion. A patent-obtaining 

firm may legitimately have such a policy simply to avoid 

having its later litigation position weakened by exposure 

to information gained from licensing discussions. Violation of such a policy would be a wrong to the firm but not 
20 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

2 

The district court found, with sufficient basis, that the 

wrongful business conduct had the required connection to 

this patent litigation. Id. at *29. As laid out above, in 

February 2005, a month after the publication of Pharmasset’s Clark Application, Dr. Durette amended the Merck 

application that ultimately issued as the ’499 patent by

canceling the broad genus claims and substituting claims 

that narrowed the scope to a subgenus focused on the key 

features of PSI-6130. Id. at *11. The district court found 

that “Dr. Durette would not have written new claims to 

cover PSI-6130 in February 2005 but for his improper 

participation on the March 17, 2004 patent due diligence 

call and learning the structure of PSI-6130 ahead of the 

structure being published.” Id.

Given that Dr. Durette learned of the PSI-6130 structure in March 2004 (as is now conceded), the district court 

could readily find that his knowledge from the call played 

a significant role in his actual process of decision-making 

that led him to file claims focusing on that and similar 

structures. Dr. Durette admitted during his deposition 

that participation in the March 2004 call, which he at the 

time denied, “would have tainted [his] judgment as to 

what claims to pursue in the Merck/Isis collaboration.” 

J.A. 22341 (38). The timing of Merck’s February 2005 

amendment, which occurred just one month after the 

structure of PSI-6130 was published in January 2005, 

supports the inference, as the district court put it, that 

Merck was deliberately “wait[ing].” Gilead, 2016 WL 

3143943, at *11 (“Dr. Durette waited to amend the 

claims . . . until Clark application was published”). Dr. 

Durette provided support for the inference of a taint when 

 

to the potential licensee, or the judicial system, in the 

absence of other understandings, such as the firewall 

understanding here.
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 21

he stated in his deposition that failing to keep participants in the March 2004 call separate from the patent 

prosecutors “could raise issues down the road on the 

patent that would issue based on the attorneys prosecuting of those patents.” J.A. 22374 (171).5

The additional finding that Dr. Durette would not 

otherwise have made the February 2005 amendment is 

not clearly erroneous. Dr. Durette’s testimony at his 

deposition greatly downplayed the role of the sole prominent candidate for an independent cause of the February 

2005 amendment, namely, the January 2005 Clark Application. In doing so, Dr. Durette gave testimony that is 

capable of being read as suggesting that the Clark Application alone would not have led him to amend the claims. 

J.A. 22344–46. Significantly, Merck did not present 

evidence that would compel a finding, or even meaningfully argue for a finding, that even if Dr. Durette personally 

had not made the February 2005 amendment, others at 

Merck lacking the earlier knowledge of PSI-6130 would 

have done something equivalent so as to break any causal 

connection between the business misconduct and the 

patent-rights benefits associated with the amendment. 

See Defs.’ [Proposed] Findings of Fact and Conclusions of 

Law Regarding Gilead’s Equitable Defenses, Gilead Scis., 

Inc. v. Merck & Co., Inc., et al., Case No. 5:13-cv-04057-

 

5 The timing of the amendment undermines a different, but ultimately immaterial, finding of the district 

court—that Merck violated the non-disclosure agreement 

with Pharmasset. E.g., Gilead, 2016 WL 3143943, at *10, 

*27, *29. The only identified forbidden use of information 

covered by the agreement—Dr. Durette’s February 2005 

claim amendment focusing on PSI-6130—did not occur 

until the information was publicly disclosed in the Clark 

Application. The disclosure ended the information’s 

protection by the agreement. J.A. 32152 ¶ 3(ii).
22 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

BLF, D.I. 407 at 27–28 (¶¶ 113–15) (N.D. Cal. Apr. 22, 

2016) (brackets in document name in original). 

Although Merck stresses that even the pre-February 

2005 claims included PSI-6130 and similar structures, Dr. 

Durette explained the benefits to a patentee’s legal position from a narrowing amendment of this sort. “It would 

expedite prosecution.” J.A. 22347 (62); see J.A. 19945

(376) (“the Examiner would have less subject matter to 

. . . search”). Relatedly, “limiting the scope” of the claims 

would mean “fewer opportunities for prior art to . . . 

present an issue of patentability” under 35 U.S.C. §§ 102 

and 103. J.A. 22347 (62). That would be so during prosecution and also in a litigation challenge. And a narrowing 

amendment can reduce a patentee’s risk on other invalidity issues, such as the risk that breadth can create under 

the requirement that the “full scope” of a claim be enabled. See, e.g., Amgen Inc. v. Sanofi, 872 F.3d 1367, 1375

(Fed. Cir. 2017). Such risks can be reduced even if, as 

here, the resulting claim still covers a large, though less 

large, number of compounds. 

In these circumstances, we see no error in the district 

court’s determination that the pre-litigation business 

misconduct we have summarized was immediately and 

necessarily related to the equity of Merck’s obtaining 

enforcement of its patent in this litigation.

B

The district court also found, with adequate evidentiary support, essentially two forms of litigation misconduct involving Dr. Durette as a witness and attributable 

to Merck. First, in his deposition, where he appeared 

partly as Merck’s corporate witness on issues to which the 

March 2004 call was relevant, Dr. Durette gave testimony 

that he did not participate in the March 2004 call—

testimony that was later conceded to be false and that the 

court found to be intentionally so. Second, both in the 

deposition and then at trial, Dr. Durette, in support of 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 23

Merck’s validity positions, gave testimony about the role 

the January 2005 Clark Application played in Dr. Durette’s filing of the February 2005 amendment that the 

court found so incredible as to be intentionally false. The 

intentional testimonial falsehoods qualify as the kind of 

misconduct that can, in these circumstances, support a 

determination of unclean hands. The court also found, 

with adequate evidentiary support, that the false testimony, in both respects, bore on the origin story of the 

February 2005 amendment, which was relevant to the 

invalidity issues in the litigation and hence immediately 

and necessarily related to the equity of the patentenforcement relief Merck seeks in this case. 

1 

In 2015, during the discovery phase of this case, 

Merck designated Dr. Durette as its corporate witness 

under Fed. R. Civ. P. 30(b)(6) on certain issues, even 

though he had retired from Merck in 2010. Gilead, 2016 

WL 3143943, at *12; J.A. 22335 (15–16), 22377 (181–84); 

J.A. 22214. In particular, Merck designated him to represent the corporation regarding the prosecution of the

application that issued as the ’499 patent. Gilead, 2016 

WL 3143943, at *12; J.A. 22214–16 (¶¶ 15–21). Dr. 

Durette was not Merck’s representative regarding the 

2007 application that issued as the ’712 patent, id. 

(¶¶ 20–21), though he filed that application. 

On May 8, 2015, Gilead deposed Dr. Durette in both 

his personal and his representative capacities. J.A. 

22331–83. Near the end of the deposition, Dr. Durette 

stated that his answers regarding the ’499 patent would 

not differ according to the capacity in which he was testifying. J.A. 22377 (183–84). Merck’s counsel represented 

both Merck and Dr. Durette at the deposition. Gilead, 

2016 WL 3143943, at *12; J.A. 22333 (7). Dr. Durette 

testified that, in preparation for his deposition, he met 

with Merck’s outside counsel for six to seven hours on 
24 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

each of two days and spent eight to ten additional hours 

on his own. Gilead, 2016 WL 3143943, at *12; J.A. 22334

(10–11).

Dr. Durette gave two different answers about whether 

he participated in the March 17, 2004 call with Pharmasset. Near the start of the deposition, J.A. 22336 (19), and 

toward the end of the deposition, J.A. 22374–75 (172–73), 

he repeatedly said that he did not recall participating. 

But during a portion of the deposition not long after it 

started (corresponding to about nine pages of the transcript), Dr. Durette repeatedly stated, definitively, that he 

did not participate. J.A. 22339–41 (30–38); see, e.g., J.A. 

22339 (31) (“sure” that he was not involved in any discussion with Pharmasset in March 2004 where he was told of 

PSI-6130’s structure); J.A. 22341 (37) (“I never participated in a due diligence meeting on March 17 . . . . I did not 

participate in any meeting of due diligence on March 17”). 

One reason that he was so sure, he said, was that it would 

have violated Merck policy to allow his participation and 

to keep him on the related patent prosecutions. J.A. 

22341 (38–39), 22373–74 (168–72); 22382 (202). On the 

basis of those definitive denials, the district court found 

that “[w]hen asked about the March 17, 2004, call at the 

deposition, Dr. Durette denied ever having been on such a 

call. When asked whether he was sure that he was not on 

the March 17, 2004, call, Dr. Durette unequivocally 

answered yes.” Gilead, 2016 WL 3143943, at *12.

That denial of participation was false, as came to be 

undisputed by Merck, and acknowledged by Dr. Durette,

at trial. See id. at *14; J.A. 19937–38 (344–47). The 

district court found the falsity of the deposition denial of 

participation to be intentional. Gilead, 2016 WL 3143943, 

at *29–31. We cannot deem that state-of-mind finding to 

be clearly erroneous, given the district court’s direct 

observation of Dr. Durette at the trial; the documentary 

evidence of his participation, including pre-participation 

emails (some that he reviewed during his deposition); and 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 25

the sufficiently supported findings that aspects of his 

testimony were “inconsistent, contradictory, and untruthful.” Id. at *29; see id. at *12–16. 

Regarding the role of the January 2005 Clark Application in Dr. Durette’s decision to file new claims in 

February 2005, Dr. Durette downplayed that role in ways 

that the district court reasonably found incredible. Most 

starkly, at his deposition, he stated that he simply did not 

recall whether he saw the Clark Application before filing 

the February 2005 amendment and hence could not state 

that it played a role in the amendment. See id. at *16;

J.A. 22343–44 (48–52), 22348–49 (66–69). 

Before trial, the court denied Merck’s motion to exclude all evidence post-dating 2002 from the jury trial 

regarding invalidity—a denial not separately challenged 

as incorrect here. J.A. 19220–22 (denying exclusion 

because the information was relevant to invalidity issues). 

Once that motion was denied, Merck itself indicated that 

it would call Dr. Durette as a witness. J.A. 19404 (42) 

(Merck explaining that Dr. Durette is “planning to come 

and testify in our case”). Gilead then took the opportunity 

to call Dr. Durette first, cross-examining him before 

Merck conducted its direct examination regarding validity 

issues, including the origin of the February 2005 amendment. 

In his trial testimony, Dr. Durette continued to downplay the role of the Clark Application, though to a lesser 

extent than during the deposition. See Gilead, 2016 WL 

3143943, at *16. Explaining his decision to file the 

amendment, he stressed that he narrowed the claims to 

“expedite” examination, id. at *17; J.A. 19944–45 (371–

75), and said that “he amended the ’499 claims to focus on 

‘get[ting] allowance on the subject matter that was most 

important to the [Merck-Isis] collaboration,’” Gilead, 2016 

WL 3143943, at *17; J.A. 19952 (404). He also testified, 

however, that he had “bec[o]me convinced that it was the 
26 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

publication of the [Clark] [A]pplication that led [him] to 

reexamine” the prosecution of the application that became 

the ’499 patent and file the February 2005 amendment. 

J.A. 19949 (390–91); Gilead, 2016 WL 3143943, at *16. 

The district court could reasonably find that, by stating 

that it was surrounding circumstances that so convinced 

him, not his own recollection, Dr. Durette was continuing 

to minimize the actual role of the Clark Application and 

what he learned in the March 2004 call, i.e., the role of 

Pharmasset’s work, in his amendment decision for Merck. 

As already noted above, the court reasonably found that 

he had in mind the information he learned in the March 

2004 call, that he was waiting for publication of PSI6130’s structure to avoid violating the non-disclosure 

agreement, and that he filed the February 2005 amendment once publication of the Clark Application occurred. 

In light of those findings, it was also reasonable for the 

district court to find Dr. Durette’s trial testimony a misleading effort to downplay the role of Pharmasset’s work 

in the February 2005 amendment.

The district court found that “Dr. Durette’s changing 

and evasive explanations for why he narrowed the claims 

undermine his testimony” and that “his testimony [was]

not credible.” Id. at *17. It found that Dr. Durette’s 

testimony that “he amended the ’499 claims to focus on 

‘get[ting] allowance on the subject matter that was most 

important to the [Merck-Isis] collaboration’ is contrary to 

the evidence and is not credible because Merck never 

tested any of the claimed compounds” until after the 

Clark Application was published. Id. The testimony 

downplaying the role of Pharmasset’s work—published in 

the Clark Application, first disclosed to Dr. Durette in 

March 2004—the court found “not credible” and “false.” 

Id. 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 27

2 

The district court properly charged Merck with the 

consequences of the testimony, at the deposition and at 

the trial, that the court found to be intentionally false. Id.

at *29 (“[T]he record shows that . . . [Dr. Durette’s] testimony was sponsored by Merck.”). As already noted, not 

only did Merck’s counsel appear as counsel for Dr. Durette at his deposition, and prepare him for it, but Dr. 

Durette was Merck’s official corporate representative on 

matters (the origin of the ’499 patent) to which the testimony at issue was relevant. As also already noted, Dr. 

Durette appeared at trial after Merck indicated that it 

was going to call him to testify about invalidity matters, 

to which the testimony at issue here had been held relevant.

The testimony, relevant to issues in the case and reasonably found to be intentionally false, had an immediate 

and necessary relation to the equity of the patentenforcement relief Merck seeks in this litigation. The 

district court held that the origin of the February 2005 

amendment, and hence Dr. Durette’s testimony about 

that, was relevant to the invalidity issues to be tried. Id.

at *14 (“At trial, Dr. Durette provided key testimony for 

Merck on validity issues, including written description of 

the ’499 Patent.”); id. at *32 (determining that the testimony was “directed at and supported Merck’s validity 

arguments, and went to the heart of significant issues in 

this case”). The verdict form made explicit that lack of 

written description and lack of enablement were tied to 

the defense of “derivation from Jeremy Clark” (the Pharmasset inventor of PSI-6130)—the latter to be addressed 

only if the jury found either lack of an adequate written 

description or lack of enablement. J.A. 21066–75. 

Merck’s own policy of separating patent prosecutors from 

discussions like the ones held with Pharmasset is confirmation that Merck recognized, as Dr. Durette testified, 

that the origin of patent claims could matter in eventual
28 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

litigation over those claims. See J.A. 22341 (39–40). In 

this case, downplaying the role of the Clark Application 

(and the March 2004 call) naturally served to aid Merck’s 

case that it did not derive the claimed inventions from 

Pharmasset’s Jeremy Clark. In these circumstances, the 

district court could reasonably determine that the testimony at issue here held a significant potential to give 

Merck an advantage in the litigation, satisfying the 

Keystone standard.

C 

We see no reversible error in the district court’s balancing of the equities. Gilead, 2016 WL 3143943, at *37–

39. As to the ’499 patent, the equity balance follows 

directly from the determinations already described: the 

misconduct leading to the February 2005 amendment and 

the misconduct involved in the litigation defense of the 

resulting patent claims. On appeal, we have relied on a 

more limited set of wrongful conduct than recited in the 

district court’s opinion, see supra nn.4–5, but we do not 

think that the equitable balance is altered by that narrowing. The conduct we have affirmed as wrongful is so 

clearly the core of the district court’s analysis that we 

have no doubt that the equitable balancing by the district 

court would have been the same if it had limited its 

wrongful-conduct findings to those we have recited. On 

these facts, there is no abuse of discretion. 

As the district court recognized, the question for the 

’712 patent is closer, but we also see no abuse of discretion 

in the district court’s ultimate conclusion that the unclean 

hands defense extends to that patent as well. The district 

court connected the ’712 patent to one portion of Merck’s 

improper conduct: once Dr. Durette improperly learned 

PSI-6130’s structure through participating in the March 

2004 call at Merck’s behest, Merck kept him in his patentprosecution role—which, as noted, included filing the 

2007 application that issued as the ’712 patent, as well as 
GILEAD SCIENCES, INC. v. MERCK & CO., INC. 29

the initial substitute claims, after the (tainted) ’499 

patent had already issued. Id. at *10–11. While the 

district court said that its “finding of improper business 

conduct related to the March 2004 call was not considered 

by the Court in determining whether unclean hands 

prevented enforcement of the ’712 Patent,” id. at *36 n.5, 

that statement does not refer to the retention of Dr. 

Durette as the lead prosecutor of HCV applications, 

including the one that eventually issued as the ’712 

patent, and the court relied on that improper retention. 

E.g., id. at *10–11. The district court relied on the connection between the two patents: “Dr. Durette played a 

key role in the prosecution of both the ’499 and ’712 

Patents. He was responsible for filing the application 

that eventually matured as the ’712 Patent and this 

application shares the same specification as the ’499 

Patent.” Id. at *36.

More importantly, the district court, turning from the 

business misconduct to the litigation misconduct, reasonably concluded that “Merck’s litigation misconduct infects 

the entire lawsuit, including the enforceability of the ’712 

Patent.” Id. at *32. “[T]he untruthful testimony offered 

by Dr. Durette in his deposition and at trial was not 

incidental, but rather was directed at and supported 

Merck’s validity arguments, and went to the heart of 

significant issues in this case.” Id. The validity issues 

were largely the same for the two patents, focused on the 

common specification of the two patents and how that 

specification bore on written-description support for and 

enablement of claims in the two patents that have closely 

related scope. As indicated above, the jury verdict form 

tied both of those issues, for both patents, to the question 

of “derivation from Jeremy Clark” (the Pharmasset inventor of PSI-6130, disclosed in March 2004 and published in 

the Clark Application). J.A. 21066–75. Thus, the litigation misconduct “infected this entire case, covering both 

patents-in-suit.” Gilead, 2016 WL 3143943, at *36. We 
30 GILEAD SCIENCES, INC. v. MERCK & CO., INC. 

conclude that, contrary to Merck’s suggestion, the district 

court set forth a sufficient explanation of the ’712 patent’s 

connection to Merck’s misconduct.

Merck argues that even where there is misconduct related to one patent, “that does not defeat claims under 

another patent simply because they were ‘brought . . . in 

the same lawsuit.’” Merck Br. 69. We agree; but the 

assertion does not undermine the district court’s ruling 

here. The Supreme Court’s decisions in Keystone and 

Precision Instruments, dealing with findings of unclean 

hands when multiple patents were at issue in the litigation and the alleged misconduct related to a subset of the 

patents, are instructive. In both cases, the Supreme 

Court applied the finding of unclean hands to all of the 

patents. Keystone, 290 U.S. at 246–47; Precision Instruments, 324 U.S. at 819. The district court in the present 

case had sufficient reason to find that both patents were 

tainted by the patentee’s misconduct, especially the 

litigation misconduct. Thus, we see no abuse of discretion 

with respect to either the ’499 patent or the ’712 patent.

III

Because the district court did not abuse its discretion 

in applying the doctrine of unclean hands, we affirm. 

Costs awarded to Gilead.

AFFIRMED