## United States Court of Appeals for the Federal Circuit

04-1506

WARNER-LAMBERT COMPANY, Plaintiff-Appellee, and SCHWARZ PHARMA, INC. and SCHWARZ PHARMA AG, Plaintiffs-Appellees,

v.
TEVA PHARMACEUTICALS USA, INC., Defendant-Appellant.

Joseph M. O’Malley, Jr. , Fitzpatrick, Cella, Harper & Scinto, of New York, New York, argued for plaintiff-appellee, Warner- Lambert Company. With him on the brief were Bruce M. Wexler , Herbert W. Rea , Joshua I. Rothman and Andrew M. Grodin

. Brian M. Poissant , Jones Day, of New York, New York, for plaintiffs-appellees, Schwarz Pharma AG, et al. With him on the brief were Francis D. Cerrito and Daniel L. Malone

. Henry C. Dinger , Goodwin Procter LLP, of Bo ston, Massachusetts, argued for defendant-appellant. With him on the brief were David M. Hashmall , Mark I. Koffsky and Dominique T. Hussey , of New York, New York. Of counsel was Kenneth A. Cohen , of Boston, Massachusetts. Appealed from: United States District Court for the District of New Jersey Senior District Judge Di ckinson R. Debevoise

## United States Court of Appeals for the Federal Circuit

04-1506 WARNER-LAMBERT COMPANY, Plaintiff-Appellee, and SCHWARZ PHARMA, INC. and SCHWARZ PHARMA AG, Plaintiffs-Appellees,

v. TEVA PHARMACEUTICALS USA, INC., Defendant-Appellant.

__________________________ DECIDED: August 11, 2005

__________________________ Before SCHALL, LINN, and PROST, Circuit Judges

. SCHALL, Circuit Judge

. Teva Pharmaceuticals USA, Inc. (“Tev a”) appeals from the final judgment of the United States District Court for the District of New Jersey that (1) U.S. Patent No. 4,743,450 (“the ’450 patent”) owned by Warne r-Lambert Company (“Warner-Lambert”) was not invalid by reason of non-enablement; (2 ) Teva infringes the ’450 patent; and (3) the ’450 patent is not unenforceable by reason of inequitable conduct. Warner-Lambert Co. v. Teva Pharm. USA, Inc. , No. 99-922 (D.N.J. July 15, 2004) (“Final Judgment”); Warner-Lambert Co. v. Teva Pharm. USA, Inc. , No. 99-922, 2004 WL 1498162 (D.N.J.June 29, 2004) (“ Ben c h Trial Opinio n ”); Warner-Lambert Co. v. Teva Pharm. USA, Inc. , 289 F. Supp. 2d 515 ( D .N.J. 2003) (“ Summary Judgment ”). The court granted summary judgment on the enablement and infringement issues. Its ruling on the inequitab l e conduct iss ue followed a bench trial. We see no error in the court’s ruling that the ’450 patent is not unenforceable by r eason of in equitable c onduct. We conclude, however, that because there are genuine issues of ma terial fact, the court erred i n granting summary judgment in favor of Warne r-Lambert on the issues of enablement and infringement. We th us affirm-in

- part and re verse-in-part and re mand the case to the district court for fu rther proceedings. BACKGROUND
I. The ’450 patent relates to angiotension converting enzyme (“ACE”) inhibitors and their methods of manufacture. A C E inhibitors comprise a class of chemical compound s that have antihypertensive pr operties and are consequently usef ul in phar maceuticals aimed at treating hypertension. There are numerous types of ACE inhibitors —such as enalapril, quinapril, and captop ril, to name a few—and di fferent hypertension drugs incorporate different A C E inhibitors. The first drug to use an ACE inhibitor reached the market in the early 1980s. It was developed us ing the ACE inhibitor known as captopril. The drug was expens ive, however, and exhibited adv erse side effects. Pharmaceutica l companies consequently continued search ing for other suitable ACE inhibit o r formulations that did not have the same si de effects as the captopril formulation.

04-1506 2Merck & Co. (“Me rck”) and Warner-Lambert we re two of these companies. Their efforts to develop a suitable hypertensi on drug using an ACE inhibit o r form th e backdrop of this case.
A. Merck directed its re search efforts to drug formulations incorporating the ACE inhibitor known as enalapril. In its pure fo rm, enalapril is a stable compound. However, Merck quic k ly disc overed that enalapril bec omes unstable when co mbined with variou s

exc i pients commonly used in drug formulations. 1 In particular, Merck found that enalapril suffered fro m two forms of degr adation, cyclization and hydrolysis. Although initially uns ure of t he particular reaction mechanism, the Merck scientists determined that the cyclization was caused by some type of intra-molecular nucleophilic attack, which resulted in the enalapr il compound converting int o an unusable by product known as dik e topiperazine. Degr adation by hy drolysis occurred when water reacted with the ACE inhibitor’s ester si de chain. The Merck formulation team was most concerned with the cyclization problem because, in addition to no team member ever having c onfront ed it prior to wo rking with enalapril, no documentation of the problem could be found in t he pertinent literature. In search of a solution to the cyclization problem , Me rck’s formulation team first turned to pH investigations. 2 This basically consisted of adjus ting the pH of enalapril in solution and then determining whether there were any corresponding improvements in stability,

1 Exc i pients are substances other t han the active ingredient that, for a variety of reasons, are added to the fo rmulation in manufacturing the drug. 2 pH is a measure of a solution’s acid ity. A solution with a pH below 7.0 is considered acidic, while a s o lution with a pH abov e 7.0 is cons idered bas ic. Acidity increases as pH decreases.

04-1506 3i.e., whether the amount of degr adation by cyclization decr eased. The team found that cyclization decreased at higher (more basic) pH levels. Fo r commercial viability , however, the end pr oduct had to be in a solid stat e. When the team tried adding appropriate pH buffers to solid enalapril, t hey found that the buffe rs did not have the same stabilizing effect. Merck’s formulation team consequently abandoned the pH studies and undertook the much more time-consuming task of fi guring out how to chemically block the cyclization reaction. The team eventually hy pothesized that it might be possible to bloc k the reaction by converting enalapril, which is an acid, to its sodium salt. The leader of the team—Dr. Gerald S. Brenner—explained the hypothesis as follows: Our feeling was that we coul d inhibit the cyclizat ion by converting OH, which is a fairly good leading group[,] to a much poorer leading group, an d that poor leading group would be ONA. In other words, c onverting enalapril, which is an acid, t o its sodium salt. So that was our working hypothesis that we could inhibi t cyclization by converting the acid group to an ONA group, a sodium salt. Bench Tria l Opinion , 2004 WL 1498162, at *4. Implementing t h is idea pr oved to be both complicated and time co nsuming, but Merck eventual ly devised a successful method in which sodium bicarb onate was used to convert enalap ril into its s odium salt. As hypothesized, Merck found th at the cyclization of enalapril was significantly reduced in its sodiu m salt form. 3 In total, it took Merck somewher e bet ween three and four years to develop a stable enalapril salt. The stabilized formula tion consisted of, among other things,

3 The Merck formulatio n team also st abilized enalapril from degrad a tion b y hydrolysis. This was presumably achieved by the addition of some exc i pient, but the record is not clear. In any event, it appears that degradation by cyclization presented Merck with much more of a problem than degradation by hydrolysis.

04-1506 4enalapril m a leate, sodium bica rbonate, and lactose. Mer ck obtained approval from the Food and Drug Administration (“FDA”) to mark et thi s formulation on Dec e mber 24, 1985. Shortly thereafter, in January of 1986, Merck began selling it as Vasotec®. Merck’s next decis ion was whether to seek patent protection for its process or to maintain it as a trade secret. It appeared at this point that all of the ingredients of Vasotec® were in the public domain. However, Merck concluded that competitors would not be able to figure out the process for making Vaso tec ® from its ingredients alone— namely, the process used to sta b il ize enalapril against cyc lization. Merck therefore chose to retain the sodium bicar bonate stabilizatio n process as a trade secre t and to forgo patent protection.
B. Around the same time that Merck was in vestigating the viabi lity of an enalaprilbased drug formulation, Warner-Lambert was investigating drug formulations using t h e ACE inhibitor known as quinapril. Warner-Lam bert’s in itial experiences with quinapril in many respects paralleled Merc k’s experienc es with enalapril. In particular, the scientists at Warner-Lambert discovered that quinapril suffered from degradation by both cycliz ation and hydrolysis

. The War ner-Lambert team also disc overed that quinapril s u ffered from an additional form of oxidative degradation, marked by discoloration of the quinapril. Apparently, over time, a white qui napril t ablet would discolor by changing to a pink or purple colo r. However, as with Merck, the WarnerLambert scientists were most concerned wit h figuring out how to minimize the degradation caused by cyclization.

04-1506 5Warner-Lambert’s quinapril formula tion team, as had Merck’s enalapril formulation team, initially looked to pH solu tions to the cyclization problem. They did this by diss olving quinapril in solution and t hen adjusting the pH of the resulting solution to determi ne if it affected stability. The fo rmulation team discovered that, in solution, cyclization was reduc ed at higher pH levels. Quinapril, lik e enal april, is an acid, and so the team needed to add alkaline excipients in order to reach these higher pH levels. One of the alkaline excipients used was s odium bica rbonate. During this time, the Warner-Lambert scientists were aware of Vasotec® and had ev en conduct ed some pH tests on it. In fact, a Warner-Lambert memorandum dated May 7, 1986, stated that Vasotec® had a pH of 6.5 in solution and t hat it was obtained thr ough the inclusion of sodium bic a rbonate. Howev e r, the Warner-Lambert scient ists soon learned the same thing with respect to quinapril as the Merck scientists had learned earlier with respect to enala p ril— namely, that while p H adjustments worked to stabilize the ACE inhib i tor in solution, the stability did not car r y over to the solid form. Therefore, sometime around May of 1986, the Warner-Lambert formula tion team abandoned pH adjustment studies and began looking for other solutions to the cyclization stability problem. This led W a rner-Lambert into th e second stage of its cyclizatio n investigation. Howev e r, unlik e the Merck team, the Warner-Lambert team did not open an investigation at this time into the reac tion pathway of the cyclization degradation process. Instead, the Warner-Lambert te am began “one-to-one exc i pient compatibility studies.” This bas ically involv ed mixing quinapril with various excipients and then studying the stability of quinapril over time. Us ing this method, the Warner-Lambert

04-1506 6team eventually determined that a formula tion of magnesium c a rbonate and lactose created a stable quinapril drug. 4 On February 24, 1987, five scientists from Warner-Lambert—Michael Harris, Gerard Hokanson, Kuchi Murthy, Robert Re isch, and Frank W a ldman—filed a patent application seeking protection for their st abiliz ed ACE in hib i tor formulation. The application issued as the ’450 patent on M a y 10, 1988, and was assigned t o WarnerLambert. Warner-Lambert also filed a New Drug Ap plication (“NDA”) with the FDA seek ing permission to market its quina pril formulation, which it named Ac cupril®. Pursuant to the Hatch-Waxman Amendments to the Federal F ood, Dr ug, and Cos m etic Act, Warner-Lambert notifi ed the FDA that A ccupril® was covered by the ’450 patent. 5 T h e FDA subsequently list ed the ’450 patent in the FDA’s “Approved Drug Products with Therapeutic Equiv a lence Evaluations” publicati on, commonly referred to as “the Orange Book.” Warner-Lambert obtai ned FDA approval of its quina pril fo rmulation in Novemb er of 1991, and began marketing it as Accupril®.
II. Teva entered the pict ure on J a nuary 15, 19 99, whe n it filed an Abbreviated Ne w Drug Application (“ANDA”) with t he FDA, seek ing approval to market a generic version

4 The Warner-Lambert scientists attri buted the reduction in degradation b y cyclization and disc oloration t o the ma gnesium c a rbonate and the r e duction in degradation by hydrolysis to the l a ctose. 5 “The applicant shall file with t he applic ation the patent number and the expiration date of any patent which claims the drug for which the applicant submitted the application or whic h claims a method of using suc h drug and with respect to which a claim of patent infringement could reasonably be asser t ed if a person not lic ensed by the owner engaged in the manufacture, use, or sale of the drug.” 21 U.S.C. § 355(b)(1) (2000).

04-1506 7of Warner-Lambert’s Accupril®. More specif ically, Tev a sought to manufacture and sell a generic hypertension drug formu lation containing the active ingredient quinap ril hydrochloride, as well as magnesium carb onate and lactose exci pients. In connection with its ANDA, and pursuant to the requirements of the Hatch-Waxman Amendments, Teva filed what is termed a “paragraph IV certif ication.” This is a certification by the ANDA applicant that any patents pertinent to the generic formulation are either “invalid or will not be infringed by the m anufacture, us e, or sale of the new drug for which the application is submitted.” 21 U.S.C. § 355(j)(2)(A)(vii)(IV) (2000). Teva’s par agraph IV certification did not state that its generic formulation woul d not infringe the ’450 patent, but it did assert that the ’450 patent was invalid under 35 U.S.C. §§ 102 and 103. On March 2, 1999, Warner-Lambert responded to Teva’s paragraph IV certification by suing Teva in the District of New Jersey for infri ngement of the ’450 patent. Warner-Lambert specifically allege d that, by filing its ANDA, Teva infringed th e ’450 patent under 35 U.S.C. § 271(e)(2)(A) (2000). 6 (Warner-Lambert appears to have later narrowed its suit to allege infringement of claims 1, 4-10, 12, 16, and 17.) Claims 1 and 16 are the only independent claims. Claim 1 is a composition claim, and reads: A pharmaceutical composition which contains: (a) a drug component which comp rises a suitable amount of an ACE inhibitor which is susceptible to cyclization, hydrolysis, and discoloration, (b) a suitable amount of an al kali or alkaline earth metal carbonate to inhibit cyclization and discolorat i on, and (c) a suitable amount of a sacch aride to inhibit hydroly s is.

6 Section 271(e)(2)(A) makes it an ac t of infringement to “submit . . . an application under section 505(j) of the Federal Food, Drug, and Cosmetic Act . . . for a drug claim ed in a patent or the use of wh ich is claimed in a patent . . . .”

04-1506 8’450 patent , col. 5, l. 52 to col. 6, l. 2. Claim 16 is directed at the method of stabilizin g the ACE inhibitor form ulation. It reads: A process for stabilizin g an ACE inhib i tor drug against cyclizatio n which com p rises the step of contacting the drug with: (a) a suitable amount of an al kali or alkaline earth-metal carbonate and, (b) one or more saccharides. Id. col. 6, ll. 54-63. In its answer Teva initially conceded that its ANDA filing constituted an act of infringement of the ’450 patent. (Answer ¶ 8.) However, Te va asserted two affirmative defenses, invalidity for “failure to meet one or more of the conditions for patentability specified in Part II of Title 35 of the United States Code” ( Id. ¶ 14), and invalidity for anticipation and/or obviousness under 35 U.S.C. §§ 102 and 103 ( Id. ¶ 16). Based on information Teva obtained during discovery, the di strict court later granted Tev a leave t o amend its pleadings t o deny infringement ( Amended Answer ¶ 20) and to assert a third affirmative defense of unenforceabil ity due to inequitable conduct ( Id. ¶ 21). After discovery, various summary judgment motions were filed on the issues of infringement, invalidit y , and un enforceability. Teva m o ved for s u mmary judgment that its quinapril hydrochloride formu lation did not infringe compos ition c l aims 1, 4- 10, or 12 of the ’450 patent. Teva also m o ved fo r summary judgment of unenforceab ility due to inequitable conduct. 7 Warner-Lambert, in turn, mov ed for summary judgment that claims 1, 4-10, 12, 16, and 17 were valid, enforceable, an d infringed. In addition, although T e va did not move for summary judgment of invalidity, Teva asserted invalidit y

7 Teva filed s e veral other motions n o t relevant to this appeal.

04-1506 9by reason of obvious ness, non-enablemen t, and lack of utility, in oppos ition to WarnerLambert’s motion for summary judgment of validity. On October 2, 2003, the dis t rict court granted Warne r-Lambert summary judgment of infringement, conc luding that no reasonable juror could find that Teva’s formulation did not infringe claims 1, 4- 10, 12, 16, and 17 of the ’450 patent. Summary Judgment , 289 F. Supp. 2d at 527. In doing so, the court rejected Teva’s contention that Warner-Lambert had failed to produce evidenc e s howing th at the lactos e in Teva ’s formulation inhibited hydrolysis, id. at 524, or that the m agnesium carbonate in Teva’s formulation inhibited cyclization and discoloration, id. at 526-27. The district court also granted War ner-Lambert’s motion fo r summary judgment of validity with respect to claim s 1, 4-10, and 12. Id. at 528. Spec ifically, the court concluded that claims 1, 4-10, and 12 were not obviou s in view of Vasotec®. Id. The court reasoned that, although Vas o tec® contained lactose, there was “no evid ence that the lactose contained in Merck’s Vasote c composition serves [Warner-Lambert’s claimed] function of inhibiting hydrolysis or that Warner-Lambert’s in ventors thought that it did.” Id. Claims 16 and 17, however, do not hav e the limitation re quiring that the lactose inhibit hydrolys is. Rather, they mere ly require “one or more saccharides.” This difference, the court c onclud ed, created a genuine is s ue of mat e rial fact as to whether claims 16 and 17 were obvious in view of Vasotec®. The court therefore denied Warner-Lambert’s motion for su mmary judgment of validity with respect to claims 16 and 17. Id. at 531-32. The court did not sa y anything about the enablement is sue. 8

8 Although it is not clear whether t he district court actually ruled on the issue, the court did make passing reference to T e va’s utilit y defense. Summary Judgment , 289 F. Supp. 2d at 528. In any even t, Teva does not argue utility o n appeal.

04-1506 10Finally, the district cour t denied both parties’ motions for summary judgment on the issue of inequitable conduc t. Teva’s allegation was t hat Warner-Lambert committed inequitable conduct by failing to disclose t he existence of Merck’s Vas o tec® to the Patent and Trademark Office (“PTO”). Id. at 532. The court c oncluded that, although the existence of Vasotec® was of high mate riality, it could not be determined on the record before the court whether Warner- Lambert intentionally had withheld this information in an effort to deceive the PTO. Id. at 536-43. After the district court disposed of the s u mmary judgment motions, Sc hwarz Pharma, Inc. and Schwarz Pha rma AG. (“Schwarz”), exclus ive licens ees of the ’450 patent, filed a motion to intervene. The court granted Schwarz’s motion on April 12,
2004. Warner-Lambert Co. v. Teva Phar m. USA, Inc. , No. 99-0922 (D.N.J. Apr. 12, 2004) (“Order Granti ng Schwar z Pharma, Inc. ’s and Schwarz Pharma AG’s Motion to Intervene”). A bench trial was subsequently held on th e issues of inequitable conduct and invalidity of claims 16 and 17. The court concluded that claims 16 and 17 were not invalid by reason of anticipation or obviousness. 9 Bench Trial Opinion , 2004 WL 1498162, at *21. T he court also conc luded that Warner-Lam bert did not commit inequitable conduct and that the ’450 patent was therefore enforceable. Id. at *10-14. With respect to inequitable conduct, after hear ing testimony from in ventors of the ’450 patent, the court found that, although the existenc e of Vasotec® was material, 10 the

9 Teva does not appeal eit her of these two rulings. 10 After trial, it appeared the court found Vas o tec® a bit less material than it did at the summary judgment stage of the proceedings

. See Ben c h Trial Opinio n , 2004 WL 1498162, at *10 (“Whether Vasotec was as ‘highly material’ as stated in [the

04-1506 11evidenc e did not show clearly and conv inci ngly that Warner-Lambert intentionally withheld the existenc e of Vasotec® in order to deceive the PTO. Id. at *14. In particular, the court cr edited the testimony of Dr. Murthy and Dr. Ha rris, who stated that the Warner-Lambert formulation team simply lost interest in Vaso tec® and, specifica lly, its sodium bicarbonate excipien t, after their initial pH inve stigations failed to yield a stable quinapril formulation. Id. at *12-14. In addition, t he court found that th e WarnerLambert inventors did not intend the claims to inc l ude bica rbonates, only carbonates. Id. at *13. Having found no inequitable conduct with respec t to claims 16 and 17, the district court entered judgment that, through the filing of its ANDA, Teva infrin ged claims 1, 4-10, 12, 16, and 17 of the ’450 patent. Teva now appeals f r om the final judgm ent of the district court. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1). DISCUSSI ON On appeal, Teva challenges the district court’s grant of su mmary judgment in favor of Warner-Lambert on the issues of enablem ent and inf r ingement. Teva als o challenges the district court’ s holding, following trial, t hat the ’450 patent is not unenforceable by reas on of inequitable conduc t. We address each of these contentions in turn, beginning with the summary judgment issues. I. We review a district court’ s decision on s u mmary judgment de novo

. Bus. Objects, S.A. v. Micro s trategy, Inc. , 393 F.3d 1366, 1371 (Fed. Cir. 2005); Conoshenti

(Cont.’d. . . .) summary judgment] opinion is s ubject to questi on in view of the facts developed at the trial.”).

04-1506 12v. Pub. Serv. Elec. & Gas Co. , 364 F.3d 135, 140 (3d Cir. 2004). Summary judgment must be granted “if the pleadings, deposi tions, a n swers to interrogatories, and admissions on file, together with the affidavits , if any, show that there is no genuin e issue as to any material fact and that the moving party is entitl ed to a judgment as a matter of l a w.” Fed. R. Civ. P. 56(c). In applying this standard, “[t]he evidence of the non-movant is to be believ ed, and all justifi able inferences are to be drawn in [the nonmovant’s] favor.” Anderson v. Liberty Lobby, Inc. , 477 U.S. 242, 255 (1986).
A. Teva first challenges the district cour t’s grant of Warne r-Lambert’s motion for summary judgment of validity. Before the district court, Teva opposed WarnerLambert’s motion on the ground t hat genuine issues of material fact remai ned as to, among other things, whether the ’450 pat ent was enabled. (Teva’s Opp’n to WarnerLambert’s Mot. for Summ. J. of Va lidity at 7-14.) Teva’s prim ary contention was that “ a person of ordinary skill in the art of pharmaceutical formulati on would nee d to resort to undue experimentation in or der to practice the cl aimed inventions.” ( Id. at 12.) Teva supported this contention with a statement by its expert witness, Dr. Joseph B. Schwartz, that one of skill in the art w ould need to pe rform numerous exp e r iments in order to practice the claimed invention. The district court thereafter granted WarnerLambert’s motion for summary judgment of valid ity wit h respect to claims 1, 4-10, and 12. However, the court’s decision, whil e t horoughly addressing Teva’s obviousness defense, does not appear to address Teva’s enablement defense. See Summary Judgment , 289 F. Supp. 2d at 528 (“In light of Teva’s experts’ affidavits affirming the

04-1506 13lack of obviousness of the saacharide [sic] clai m limitation Warner-Lambert is entitled to summary judgment of validity of claims 1, 4-10 and 12 of the ’450 patent.”). On appeal, Teva contends that sufficient issues of fact remain regarding enablement so as to preclude s u mmary judgment of validity for Warner-Lambert. In particular, Teva maintains that the ’ 450 patent is not enabled because the patent’s written des cription does not teac h a person of skill in t he art how to make and use the full scope of the invention without undue experim entation. That, according to Teva, is because, while the patent claims numerous co mbinations of ACE inhib i tors, alkali or alkaline earth metal carbonates, and saccharides , the specification only dis c loses two working examples, both of which are bas ed on the same gener al combination of enalapril hydrochloride, magnes ium carbonate, and lactose. Moreover, Teva continues, the specific ation is so lacking in guidanc e that, outside of the one combination disclos ed in the patent’s examp l es, a person of skill in the art could not practice the invention without undue experimentation. Accordingly, Teva asks us to vacate the district court’s decision and remand for resolution of whethe r one skilled in the ar t would be required t o exercis e undue experimentat ion before practicing t he claimed invention. In respons e, Warner-Lambert contends that the district court properly granted its motion for summary judgment of validity. First, Warner-Lambert argues that Teva has not presented compet ent evidence showing a gen uine issue of fact as to whether th e ’450 patent’s spec ification failed t o provide s u fficient guidance. Warner-Lambert asserts that the only ev idence offered by Teva consists of two lega lly and technicall y incompetent expert reports by Dr. Schwartz. Warner-Lambert assert s that the reports are legally incompetent because they are uns worn. Second, Warner-Lambert contends

04-1506 14that the written description, particularly th e two working examples for 5 and 40 mg quinapril formulations, see ’450 patent, col. 4, l. 57 to co l. 5, l. 12, provide sufficient guidance so as to enable the full scope of the claims. Warner-Lambert also asserts that we should not consider some of Teva’s argu ments, such as the a lleg ed u npredictability of the art, because they were not pr operly raised before t he district court. The enablement provision of the Patent Act requires t hat the patentee provide a written description of the invention “in such full, clear, concise, and exact terms as to enable any person sk illed in the ar t to whic h it pertains, or with which it is most nearly connected, to make and use the same.” 35 U.S.C. § 112, ¶ 1 (2000). The purpose of this requirement is to ensure that “the public knowledge is enriched by the patent specification to a degree at least commens urate with the scope of the claims.” Nat’l Recovery Techs., Inc. v. Magnetic Separation Sys., Inc. , 166 F.3d 119 0, 1195-96 (Fed. Cir. 1999); see also Don a ld S. Ch isum, 3 Ch isum on Patents § 7. 01 (2002). Accordingly, we have held that t he spec ific ation must provide s u fficient teaching suc h that one skilled in the art could make and us e the full scope of t he invention without undue experimentation. CFMT, Inc. v. Yieldup Int’l Corp. , 349 F

. 3d 1333, 1338 (Fed. Cir. 2003); Genentech, Inc. v. Novo Nordisk A/S , 108 F.3d 1361, 1365 (Fed. Cir. 1997); In re Wands , 858 F.2d 731, 736-37 (Fed. Cir. 1988). “The key word is ‘undue,’ not experimentation.’” Wands , 858 F.2d at 737 (citation omitted) . That is, the specification need only teach those aspects of the invention that one skill ed in t he art could not figure out without undue experimentation. See, e.g. , Nat’l Recovery Techs. , 166 F.3d at 1196 (“The scope of enablement . . . is that which is disc losed in the specification plus the scope of what wo uld be kn o w n to on e of ordina ry skill in t he art without undu e

04-1506 15experimentation.”); Wands , 858 F.2d at 736-37 (“Enablement is not preclu ded by the necessity for some experimentation such as routine screening.”). Although the ultimate determination of w hether one sk illed in the art could make and use the claimed invention without undue experi mentation is a legal one, it is based on underlying findings of fact. CFMT , 349 F.3d at 1337. Further more, “[w]hether undue experimentation is needed is not a single, simple factual determination, but rather is a conclus i on reached by weighing m any factual cons ider ations.” Wands , 858 F.2d at 737. Some of these considerations , commonly referred to as “the Wands factors,” include “(1) the quantity of experimentation necess a ry , (2) the amount of direction or guidanc e presented, (3) the presence or absence of wo rking examples, (4) the nature of the inventio n, (5) the state of the prior art, (6) the relative skill of those in the art, (7) the predictabilit y or unpredictabi lity of the art, and (8) the breadth of the claims. ” Id. ; see also Amgen, Inc. v. Chugai Pharm. Co. , 927 F.2d 1200, 1213 (Fed. Cir. 1991) (stating that the Wands factors “are illustrative, not mandator y” and that what is relevant to a n enablement determination depends upon the facts of the particular case). At the outset, we find the issue of enabl ement difficult to review becaus e the district court did not address it in its dec ision granting Warner-Lambert’s summary judgment motion. We have no wa y of knowing what t he distri ct court thought of Teva’s enablement defense or why the cour t did not address the issue in its decision. In short, we are being asked to review an incomplete record. Not knowing the reasoning of the district court, we have nevertheless consider ed the arg u ments of t he parties, reviewed the limited record before us, and now c o nc lude that Teva has presented fact-based arguments in support of its enabl ement defense that are deservi ng of consideration by

04-1506 16the district court. Spe c ifical ly, Te va has arg ued that, a t t he time of filin g for the ’4 50 patent, one of skill in t he art would have had to resort to undue experimentation in order to make the claimed f o rmulations not disclos ed in the patent’s t w o working examples. In oppos ition to Warner-Lambert’s motion fo r summary judgment, Teva supported this contention with declar a tions from its expert witnesses, Dr. Schwartz, who stated that one of skill in the art woul d need to undertake a range of experimentation in order to practice the claimed invention. (Teva O pp’n to Warner-Lambert Mot. for Summ. J. of Validity at 9, 13.) 11 Acc o rdingly, we reverse the grant of summary judgment on WarnerLambert’s motion for validity and remand to the district court for further proceedings on the issue of enablem ent. See Nazomi Communications, In c. v. ARM Holdings, PLC , 403 F.3d 1364, 1371-73 (Fed. Cir. 2005) (remanding issues of claim construction and infringement based in part on t he district cour t’s failure to provide sufficient reasoning for its decision).
B. Teva next challenges the dist rict court’s grant of summary judgment of infringement in favor of Warner -Lambert. Before the district court, Teva asserted three main non-infringement defenses. The first defens e related to the function of lactose in

11 We do not address Warner-Lambert’ s argument regardi ng the legal and technical c o mpetency of Dr. Schwartz’s ex pert reports. These types of evidentiar y issues are most appropriately ad dressed in the first instance by the trial court. On the other hand, we reject War ner-Lambert’s assertion that Teva waive d so me of its enablement arguments, such as the unpredictability of the art, by not raising them before the trial court. In this case, it was su ffi cient that Teva raised the general issue of enablement. See Interactive Gift Ex press, Inc. v. CompuServe Inc. , 256 F.3d 1323, 1346 (Fed. Cir. 2001) (stating that, in general, it is the claim or issue that must be pressed before the tri a l court, not the underlying arguments in support of that claim or issue); see also Stratoflex, Inc. v. Aeroquip Corp. , 713 F.2d 1530, 1540 (Fed. Cir. 1983) (“We sit to review judg ments, not opinions.”).

04-1506 17Teva’s for m ulation and whether it inhibite d degradation by hy drolysis. The second and third defenses related to magnesium carbonat e and, specifically, w hether it served t o inhibit degradation by cyclization and discolorati on in Teva’s formulation. The district court rejected all three of these arguments. With respect to Teva’s first defense, the c ourt concluded t hat Warner-Lambert submitted evidenc e sufficient to show that the lactose in Teva’s formulati on inhibited hydrolysis. The cour t cited Tev a ’s “Final Development Report,” which stated that the lactose monohydrate “excipi ent serves as a filler and will also inhibi t hydrolysis of the active raw material .” Summary Judgment , 289 F. Supp. 2d at 522-23 (emphasis in original). This report, t he court noted, was subsequently approved by Teva’s Sen i or Vice-President of Research and Development. Id. at 523. In additi on, as part of its ANDA, the court noted that Teva submitt ed an “Excipient Function Report,” which similarly st ated that the lactose serves to “inhibit hydrolysis of the raw material.” Id. Finally, the court found that Teva could not r easonably deny that it designed its generic formulation with the ’450 patent fully in mind. That, according to the court, was because the ’450 patent was listed in one of Teva’s internal data bases as a patent covering Warner-Lambert’s Accupril® product. Furthe rmore, the court noted, Teva’s formulation team met i n January of 1998 to discuss whether , in addition to a formulation containing magnesium carbonate and lactose, the team should also “develop a totally different formulation in parallel to our current formulation to avoid any potential patent issues with our current strategy.” Id. at 524. With respect to Teva’s second two defens es, relating to the functions served b y magnesium carbonate in c onnection with c yclizat ion and disc olor ation, the district court

04-1506 18first addressed Warner-Lambert’ s argument that the defenses were untimely. WarnerLambert argued that Teva shou ld be precluded from assert ing the defenses because it did not dis c lose them in response to Warn er-Lambert’s contention interrogatories. In addition, considering discovery had since cl osed, Warner-Lambert believed it would be prejudiced by allowing the defens es. The c o urt found that Warner-Lambert’s argument had “cons iderable merit” and that “[a]t the very least the circumstances require[d] that Teva’s mot i on for sum m ary judgment be deni ed to giv e Warner-Lambert the opportunity to take dis c overy on the issue . . . .” Id. at 526. Howev e r, the court decided to nevertheless address the defenses becaus e it found them to lack merit. Id. The court reasoned that Teva chose to “use[] magnesium carbonate becaus e . . . it ensured chemical and phys i cal stab ilit y.” Id. Indeed, the court noted, Teva specifically represented to t he FDA that magnesium carbonate “s tabilize[d]” its quinapril formulation. Further, the court continued, “[b]ecause lactose is claimed to inhib i t hydrolysis, magnesium carbonate must be the inhibitor of the only two other kinds of degradation, cyclization and discoloration. ” Id. The court found support for this conclus i on in the deposition te stimony of Teva’s Director of Analytical Research & Development, who stated that the magnesi um carbonate in t he generic formulation served to “inhibit[] D.P. forma tion” (which is t he quinapril impurity formed by cyclization). Id. at 527. The court therefore conclud ed t hat “no reasonable f a ct-finder could find that lactose in Teva’s quinapril formulations does not inhibit hydroly s is, and no such fac t finder could find that the magnesium carb onate in T e va’s quinapril formulations doe s not inhibit cyclizati on and discoloration.” Id. Accor d ingly, the court denied Tev a ’s

04-1506 19motion for summary judgment of non-infringem ent of claims 1, 4-10, and 12, and granted Warner-Lambert’s motion for summary j udgment of infringement of claims 1, 4- 10, 12, 16, and 17. On appeal, Teva contends t he district court erred bec a u se Warner-Lambert failed to make out a prima f a cie c a se of infringement with r e s pect to c l aims 1, 4-10, and 12. 12 Teva spec ifically ma in tains that Warner- Lambert did not present evidence showing (1 ) that the quinapril in T e va’s formulation is s u sceptible to oxidativ e discoloration, or (2) that any oxidative discoloration that does occur is inhibited by the magnesium carbonate. Teva asserts that , as evidenc ed by the depositi on statement of Mr. Reisch, an inventor on the ’450 patent, discoloration of quinapril can be caused by a variety of factors besides oxidation. Teva similarl y asserts that any discoloratio n could be inhibited by exc i pients other than magnesium carbonate. Gi ven Warner-Lambert’s lack of evidenc e on these issues, and considering that the case wa s before the district court on Warner-Lambert’s motion for summary judgm ent of infringement, Teva contends, the district court should have given Teva the reas onable inferences that any dis c oloration of the quinapril was caused by some process other than oxidat ion, and that some

exc i pient other than magnesium carbonate could be re sponsible for inhibiting any oxidative discoloration that did occur. In respons e, Warner-Lambert argues that t he district court’s dec ision should be affirmed because T e va did not timely discl ose its discoloration defens e. In the alternative, Warner-Lambert contends the evidence shows that, in the absence of magnesium carbonate, the quinapr il in Tev a ’s product exhibits degradation by oxidativ e

12 Teva does not challenge the dist rict court’s summary judgment of infringement with respect to claims 16 and 17.

04-1506 20discoloration. Schwarz, t he intervening plaintiff and ex clusive licensee of the ’450 patent, als o argues that the district court improperly construed the term “discoloration” to mean “oxidative dis c oloration” instead of just “change in color.” 13 A determination as to patent infri ngement is a two-step process. PC Co nne c tor Solutio n s L L C v. SmartDisk Corp. , 406 F.3d 1359, 1362 (Fed. Cir. 2005). First, the court must construe the claims. Id. Second, the court must compare the accused product or process to the properly construed claims. Id. The first step is a question of law and the second s t ep is a question of fact. SmithKline Beec ham Corp. v. Apotex Corp. , 403 F.3d 1331, 1337 (Fed. Cir. 2005). In fringement may be found only where the accused product or process contains each lim itation of the claim, either literally or under the doctrine of equivalent s. Deering Precision Instrume nts, L.L.C. v. Vector Distrib. Sys., Inc. , 347 F.3d 1314, 1324 (Fed. Cir. 2003). In this case, the first issu e is whether the district c ourt erred in construing “discoloration” to mean “oxidativ e discoloration” instead of just “change in color.” We do not think that it did. As the court noted in its summary judgment ru ling, the only type of discoloration referred to in the ’450 patent is ox idative disc oloration. Summary Judgment , 289 F. Supp. 2d at 524. The Backgr ound s e ction of the patent, for example, lists cycliz ation, hydrolysis, and “oxidatio n to form products having often unwanted coloration,” as the three types of degradation exhibited by ACE inhibitors. ’450 patent, col. 1, ll. 9-12. The spec ification then goes on t o di sc lose one emb odiment that withstands “oxidative, hydrolyt ic, and cycliz ation degradation.” Id. col. 1, ll. 20-22; see

13 In its reply brief, Teva argues t hat we should not allow Sc hwarz t o challenge t he district court’s claim construc tion because it did not intervene until after the summary judgment ruling on infringement. We do not need to address Teva’s argument because, either way, we think the district court c onstrued the claims correctly.

04-1506 21also id. col. 1, ll. 29-35 (touting one advantage of the inv ention as being “no detectable oxidative discoloration”). Additionally, the parties previous ly stipulated that “discoloration” referre d to oxidative discolor a tion. Warner-Lambert Co. v

. T e va Pharm. USA, Inc. , No. 99-922 (D.N.J. May 7, 2002) (“S tipulation and Order”) (“The phrase ‘a suitable amount of an ACE inhibitor which is susceptible to cyclization, hydrolysis, and discoloration’ in Claim 1 of the ’450 patent means ‘an amount of an ACE inhibitor having antihypertensive properties having the structural capacit y to cyclize via internal nucleophilic attack, hydrolyze a side chain ester, and undergo oxidative dis c oloration , wherein the amount of such ACE inhibitor is suffi cient to treat hypertension or congestive heart failure.’” (emphasis added)). Therefore, we conclude that embodiments of claims 1, 4-10, and 12, must include an ACE inhib i tor that is susceptible to oxidativ e discoloration, and mu st also include an alkali or alkaline earth metal carbonate (or bicarbonate) 14 that inhibits oxidative d i scoloration. Having confirmed the proper construction of claims 1, 4-10, and 12, we ne xt must determine whether the district court erred i n concluding that no reasonable juror could find non- infringement. We turn first to Teva’s content ion that the district c ourt erred because Warner-Lambert failed to show that the quinapril in Teva’s formulation is susceptible to oxidativ e discoloration. The c ourt stated that “[o]xidat ion is almost all the time the source of dis c oloration,” and that w hen disc oloration does occur, it is “obviou s and is detected by the unaided eye” thr ough a pink or purple color change. Summary Judgment , 289 F. S upp. 2d at 526. This findi ng is supported by the record. For

14 Our prior decisio n in Schwarz Pharma, Inc. v. Warner-Lambert Co. , No. 03-1384, 95 Fed. Appx. 994, 997-99 (Fed. Cir. Jan. 29, 2004), construed “alkali or alkaline earth metal carbonates,” as used in the claims of the ’450 patent, to include both carbonate and bicarbonate ions.

04-1506 22example, T e va’s Analytical Research and Development R eport showed that a quinapril hydrochloride sample “changed color [over time ] from white to a light purple color.” (J.A. 12671.) Similar observations were docu mented in Teva’s l ab notebooks. (J.A. 12821.) Teva argues that this was still insu fficient evidenc e because it submitted evidenc e establishing that “it is impossi ble to determine whether discoloration i s oxidative from an observable color change.” (Reply Br. of Teva at 26.) Howev e r, Warner-Lambert only needed to show that the color change made it more likely than no t that oxidation had occ u rred. See Liberty Lobby , 477 U.S. at 252 (“[T]h e inquiry involved in a ruling on a motion for summary judgment . . . implicates the s ubstantive evidentiary standard of proof that would apply at the trial on the merits.”). 15 We believe WarnerLambert satisfied this burden. W a rner-Lam bert cites to a “Compr ehensiv e Summary of Quinapril,” in whic h it appeared generally un derstood that quinapril, in the absence of a suitable st abilizing agent, suffere d from oxidative discoloration. (J.A. 1174.) Teva has given us no reason to believe its quinapr il should behave any differently than the quinapril st udied and used by W a r ner-Lambert. Teva points to deposition testimony of one of the co-inventors on the ’450 patent, Mr. Reisch. When ask ed if a c h ange in color indic a ted that oxidat ion had oc curred, he responded, “not definitively.” However, Mr. Reisch went on to state that oxidation was t he “most likely” cause of a pink coloration. Q: What is the purpose for det ermining the color of these samples? A: The color is considered undesirable.

15 A claim for patent infringement mu st be proven by a preponderanc e of the evidenc e, Advanced Cardiovasc ular Sys., Inc. v. Scim ed Life Sys., Inc. , 261 F.3d 1329, 1336 (Fed. Cir. 2001), which s i mply requires prov ing that infringement was more likely than not to have occurred.

04-1506 23Q: Is a change in color r e lated to the level of oxidation for the quinapr il? A: Most likely. Q: And what is the mos t lik ely relationship of color t o oxidation in quinapril? A: I don’t understand. Q: Well, you start with white, correct? A: Right. Q: If you do this test and you see pink, does that make it more likely or less likely that the quinapril has undergone oxidation? A: It makes it more likely. (July 20, 2000 Dep. of Robert G. Reisch at 50.) In sum, Teva’s bald assertion that some thing els e could be res p onsible for the color change is not s u fficient to rebut Warner-Lambert’s prima facie showing that the color change is more than likely due to oxidation. Liberty Lobby , 477 U.S. at 252 (stating that, after the mo ving party makes out a prima facie showing , the party opposing s u mmary judgment must come forward with more than a scintilla of evidenc e to create a genuine is sue of material fact). Therefore, because Warner-Lambert made

a prima facie showing that the quin april in Tev a ’s formulation was susc eptible t o oxidative discoloration, and because Tev a f a iled to respond with specific evidence to the contrary, we hold that no reasonable ju ror could conclude that the quinapril in Teva’s formulation was not susceptible to oxidative dis c oloration. Howev e r, Teva also contends the dist rict court erred because, even if the quinapril in its formulation is susceptible t o oxidativ e discoloration, Warner-Lambert failed to pr oduce evidence showing that th e magnes ium carbon ate in the formulation inhibited the discoloration. We agree with T e va that W a rner-Lambert failed to make out

a prima facie case as to this claim limitation. In that regard, we note the following portion of the court’s decision:

04-1506 24Warner-Lambert’s inventor s found that magnesium carbonate inhibited [oxidative] di scoloration. Likewise, Teva never obs erved disc oloration in its magnesium car bonatebased formulation. It used magn esium carbonate because it concluded that it ens ured chemical and phy si cal stability. It represented to the FDA that magnesium carbonat e “stabilizes” its quina pril formulation. Because lact ose is claimed to inhibit hydr olysis, magnesium car bonate must be the inhibitor of the only tw o other kinds of degradation, cyclization and discoloration

. Summary Judgment , 289 F. Supp. 2d at 526 (emphasis added). We do not think this reasoning supports the grant of summary judgment in favor of Warner-Lambert. It may very well be that the magnesiu m carbonate inhibits oxidative di s c oloration. However, it may also be that some other exc i pien t in the formulation is responsible. Cf. Fisher , 427 F.2d at 838-39 (stating that many chemical r eactions are unpredictable). The point is that Warner-Lambert, the party who bears t he burden of proving infringement by a preponderance of the evidenc e, has not presented evidence to show that it is in fact the magnesium carbonate that serves this particul ar stabilizing function. It is true that Warner-Lambert presented evidence showing t hat the lactose inhibits hydrolysis and that the magnesium carbonate i nhibits cyclization. T hat does not necessarily mean, though, that the magnesium ca rbonate also inhibits oxidative discoloration. Accordingly, at this stage of the proceedings, drawing all reasonable inferen c es in favor of Teva, we must conclude that genuine i ssues of fact remain as to whether the magnesium carbonate in Tev a ’s formulation inhibits oxidativ e disco lor a tion of the quinapril. In reaching our conc lusion, we of fer no views as to Warner-Lambert’s argument that Teva should be procedurally barred from asserting its discoloration defense. The district court seemed to agree with Warner- Lambert that the defense was untimely and

04-1506 25prejudicial to Warner-Lambert. Nevertheless, the district c ourt chose to dis pose of the defense on its merits. Having reversed the di strict court’s judgment on the merits, we leave to the sound discretion of the district court the matter of how to most appropriate l y proceed on remand. II. Teva also challenges the district court’s finding, following a benc h trial, that the ’450 patent is not une nforceable by reason of inequitable conduc t. Inequitable conduc t occurs when a patentee breaches his or her duty to the PTO of “candor, good faith, and honesty.” Molins PLC v. Textron, Inc. , 48 F.3d 1172, 1178 (Fed. Cir. 1995). This can occur through “affirmative misrepresentations of a material fact, failure to disclos e material information, or submission of fa lse information, coupled with an intent to deceive.” Id. “One who alleges inequitable conduct arising from a failure to disclos e prior art must offer clear and convincing pr oof of the materiality of the prior art, knowledge chargeable to the a pplic ant of that prior art and of its materiality, and the applicant’s failure to disclose the prior art, coupled wit h an intent to mislead the PTO.” Id. ; see als o Duro-Last, Inc. v. C u stom Seal, Inc. , 321 F.3d 1098, 1109-10 ( F ed. Cir. 2003). We review the district court’s fi ndings of fact for cle a r error an d the ultimate determination of whet her inequit able condu ct occurred for abuse of discretion. DuroLast , 321 F.3d at 1110. “A finding [of fact] is ‘clearly erroneous’ when although there is evidenc e t o support it, the reviewing court on the entire evidence is left with the definite and firm conviction that a mistake has been committed.” Am. Pelagic Fish ing Co., L.P. v. United States , 379 F.3d 1363, 1371 (Fed. Cir. 2004) (cit ation omitted). “An abuse of

04-1506 26discretion may be establis hed under Federal Circu it law by showing th at the court made a clear error of judgment in weighing the re levant factors or ex ercised its discretion based on an error of law or clear ly erroneous fact finding.” Int’l Rectifier Corp. v. Samsung Elecs. Co. , 361 F.3d 1355, 1359 (Fed. Cir. 2004) (citation omitted). Teva’s argument before the district court was that the inventors of the ’450 p a tent committed inequ itable conduct b y failin g to discl os e the e x istence of Merck’s Vasotec ® to the PTO during prosecution of the ’450 pat ent. In its decision denying the parties ’ cross motions for summary judgment on the issue, the court co ncluded that while Vasotec® was highly material, 16 genuine is sues of fa ct remained as to whether t he Warner-Lambert inventors withheld information re lating to Vasotec® with the intent to deceive the PTO. Summary Jud g ment , 289 F. Supp. 2d at 536-4 3. The court therefore held a bench trial to determine whether su ch a deceptive intent accompanied the inventors’ f a ilure to disclose Vas o tec®. At the end of the trial, t he court concluded that there was no such deceptive intent and consequently granted Warner-Lambert judgment of no inequitable conduct. Bench Trial Opinio n , 2004 WL 1498162, at *13-14. In reaching its decision, t he district court stated that it had not fully appreciated the signific ance of Warner-Lambert’s tw o- stage quinapril investi gation until hearing Warner-Lambert’s witnesses testify at trial. Id. at *12. In particula r, the testimony of Dr. Murthy and Dr. Harris, two of the inventors listed on the ’450 patent, indic a ted to the court that Warner-Lambert’s formulation team was only interested in Vas o tec® d u ring the first investigatory stage, involving the pH studies, and that, even at this stage, their interest was limited to “ascertaining the pH of the Vas o tec tabl et in solution. ” Id. The

16 As noted above, see note 10, supra , after trial, the district court backed away from this conclusion somewhat.

04-1506 27court noted that Warner-Lambert’s formulation team knew Vasotec® contained sodium bicarbonat e. However, the c ourt found, the team did not know how sodium bicarbonat e was used to stabilize enalapril. Id. at *12-13. Warner-Lambert abandoned the pH studies sometime in May 1986, and soon ther eafter commenced the second stage of i t s investigation, involving one-to-o ne exc i pient compatability studies. By June or July of 1986, the court stated, “Vasotec and its use of sodium bicar bonate were no lon ger of interest to Warner- Lambert’s scientists[.]” Id. at *12. Therefore, considering that it was the compatibility studies that ultimately resulted in the discovery of the stable quinapril, magnesium carbonate, and lactose formulati on, the court found that the inv e ntors simply did not consider Vasotec® relevant to their invention when they filed for patent protection. Id. at *13-14. The district court acknowledged that Dr. Murthy, a co-inventor of the ’450 patent, made som e rather inc u lpatory st atements in his deposition. Id. at *11. In particular, he stated that at the time he and his co-inventors were prepari ng t o file the ’450 patent’s application, they disc ussed Vas o tec® and dec ided not to disclose it to their patent attorney. Id. However, at trial, Dr. Murthy st ated that he had made a mistake in his deposition testimony: Here’s what I recall today, your Honor. At the time when I testified to this was b a ck in 200 1. . . . I was trying to recall events that took place about 14 y ears. And it was true that we discuss ed about sodium bicarbonate, and we disc ussed it with Enalapril and Merck’s [V asotec®] at the beginning of our program. But after we ran exp e riments, sodium bicarbonat e at different levels and different methods or incorporation, we were not successful in stabiliz in g this product. Sodium bicarbonate did not help us in any way. So the whole sodium bic a rbonate, and Enalapril, and Vasotec ® fell off the table as-- after we stabiliz ed o u r product with magnesium carbonate and lactose. And so we did not--it's

04-1506 28true that I-- I did testify to this effect, but afte r reflecting on it, it just--I was mixed up with the dat es at the time. It was true, we did disc uss about this, but that was the beginning of the program and not at the time of the filing. The discus s ions took place much earlier, at t he beginning of the program. Id. Dr. Harris, another co-inventor of the ’450 patent, also testified that he did not recall any discus s ions of Vasotec® after the team abandoned t he pH studies. Id. a t * 1 2

. T h e court found both of these inventors to be “com pletely credible witnesses,” noting that neither of them were still em ploy ees at Warner-Lambert. Id. Teva argued that the Warner-Lambert sci entists must have known Vasotec ® wa s material, considering that claims 16 and 17, as or iginally filed, referred only to “alkali or alkaline earth metal salts,” and therefore read on formulati ons comprising enalapril a n d sodium bic a rbonate (two of t he key ingredients of Vasotec®). Howev e r, the district court rejected this argument, finding that mere knowledge of sodium bicarbonate as one of the ingredients of Vasotec® in no way in formed the Warner-Lambert scientists as to how s odium bicarbonate was us ed to stabilize enalapril. Id. at * 12-13. This, the court stated, was confirmed by t he fact that the Warner-Lam bert team only used sodiu m bicarbonat e to adjust pH during t he first phase of the investigat ion. Merck, on the other hand, utiliz ed sodium bicarbona te for a much different purpose, to convert enalapril maleate into its sodium salt form. Id. at *13. The district court’s conclusion was also not affected by our intervening dec ision of January 29, 2004, in Schwarz Pharma , in whic h we construed “carbonate” in the ’450 patent to include “bicarbonate.” 95 Fed. Appx. at 997-99. The court reiterated that the subjective intent of the patentees was not to claim sodium bicarbonate or the Vasotec ® formulation. Rather, “[b]ased on their su cc ess with magnesium carbonate and failur e

04-1506 29with sodium bicarbonate, they were thinking only in terms of an exc i pient possessed of the carbonate ion.” B ench Trial Opinion , 2004 WL 1498162, at *13. The court therefore concluded that “[t]he evidence does not support Teva’s argument that failure to disclos e Vasotec®, which cont ained sodium bicarbo nate, was intended to deceive the PTO.” Id. at *14. On appeal, Teva cont ends the district c ourt abused its discretio n in not finding inequitable conduct. Teva’s primary argument is that the court failed to appreciate the difference between what the ’450 patent discloses and what it c l aims. In particular , while the working examples of the patent only disc lose the quinapril, magnesium carbonate, and lactose formulation, Teva asse rts that the claims cover much more, including enalapril stabiliz ed by sodium bic a rbonate a nd lactose (i.e. the Vasotec® formulation). Teva further asserts that the patentees, knowing claims 16 and 17 actually read on Vas o tec®, inte ntionally withheld its existenc e from the PT O in order to gain allowance of the broadly drafted claims. Therefore, Teva contend s that an inference of intent to deceive the PTO is war r anted under our decision in Critikon, Inc. v. Becton Dic kinson Vas c ular Access, Inc. , 120 F.3d 125 3, 1257 (Fed. Cir. 1987), where we held that “a patentee facing a high level of mate riality and c l ear proof that it knew or should have known of that materiality, can expect to find it difficult to establish ‘subjective good faith’ sufficient to prevent t he drawing of an infe rence of intent to mislead.” In addition, Teva contends that the submission of an oath by the ’450 patentees, stating that they were the first to invent a method of stabiliz ing ena lapr il, constitutes an independent basis fo r finding inequitable conduct.

04-1506 30Teva urges us to reject Warner- Lambert’s explanation for not disclosing Vasotec®, i.e., Warner-Lambert’ s argument that, while their formulation team knew of Vasotec®, they did not know how sodium bi carbonat e was used to stabilize enala p ril against cy clization. Teva argu es that the story is not believable, becaus e the claims read on Vasotec® irrespective of whether t he ’450 patentees actually knew how Merc k used sodium bicarbonate to st abilize enalapril. T hat, according to Teva, is becaus e claim 16 places no limitation on how the excipien ts stabilize the ACE in hibit o r; it simply recites a m e thod of “c ontacting” an ACE inhibitor with an “alk ali or alkaline earth metal carbonate” and “one or more sa ccharides.” Therefore, while War ner-Lambert may not have kno w n how Mer ck stabiliz e d enalapril, Teva arg ues that the ingred ie nts of the Vasotec® formulation (i.e. enalapril and s odium bicarbonate) remained relevan t throughout prosecution of claims 16 and 17. In response, Warner-Lambert first argues that Teva is not entitled to a finding of inequitable conduct because it has not been “f rank and fair” with the court in its representations, and, a party may not seek equitable relief if it has unclean hands. 17 I n any event, Warner-Lambert maintains that Vasote c® is not material to claims 16 and 17 because the claims require more than just “c ontacting an ACE inhibitor a carb onate an d a saccharide.” They also require that t he alkali or alkaline ea rth metal carbonate stabiliz e the ACE inhibitor agains t cyclization. And, because its inventors did not know that sodiu m bicarbon ate had a stabiliz ing effect on the ena lapril in Vas o tec®, Warner-

17 In particular, Warner-Lambert argues that Teva has made various factual misrepresentations to this court. For ex ample, Warner-Lambert states that Tev a repeatedly characterizes the dist rict court as having found Vasotec® “highly material,” even though that statement wa s made in the court’s summa ry judgment decision and was subsequently called into doubt in the court’s bench trial opinion.

04-1506 31Lambert asserts that the district court proper ly found that Vasotec® was not material. 18 Warner-Lambert similarly maintains that, even if Vas o tec® was mate rial, the district court found that its inventors did not withhold Vas o tec® with the intent to deceive the PTO. In addition, Wa rner-Lambert argues that this fin d ing invo lv ed numero u s credib ilit y determinations, made after hearing liv e testimony at trial. Warner -Lambert asserts that Merck’s de cision to maintain its method of stabiliz ing Vasotec® as a trade secret further demonstrates that the ’450 invent ors did not know the r o le sodium bicarbonat e played in Vasotec® and, cons equently, had no intent to deceive the PTO in not disclos ing Vasotec®. Finally, W a rner-Lambert contends t hat Teva’s “false oath” argument should not be considered because it was not raised below. We cannot say the district court erred on the inequitable conduct issue. In particular, we cannot say that the court clear ly erred in finding that the Warner-Lambert inventors did not intend to deceiv e the PTO in not disclosing the existence of Vasotec®. It is true that “[d]irect evi dence of intent or proof of deliberate scheming is rarely available in instances of inequitable con duct,” and that “intent may [therefore] be inferred from the surrounding circ umstances.” Critikon , 120 F.3d at 1256. It is also true that “[t]he more mate rial t he omission or the misrepresentat ion, the lower the level of intent required to establish i nequitable conduct . . . .” Id. However, determining whether there was intent to deceive is still a c ont extua l e x e r cise, and “materiality does not presume intent, which is a separ ate and es s ential c o mponent of inequitab l e conduct.”

18 Warner-Lambert notes that, while the dist rict court initially considered Vasotec® a “highly ma terial” reference, Summary Judgment , 289 F. Supp. 2d at 536, the court backed off this statement after hear ing fro m Dr. Murthy and Dr. Harris during the bench t r ial, Bench Trial Opin ion , 2004 WL 1498162, at *10 (“Whether Vasotec was as ‘highly material’ as stat ed in [the summary judgment] opini on is subject t o question in view of the facts developed at the trial.”).

04-1506 32GFI, Inc. v

. Franklin Corp. , 265 F.3d 1268, 1274 (Fed. Cir. 2001). To be sure, “a patentee facing a high level of materiality and clear proof that it knew or should hav e known of that materiality, can expect to find it difficult to establish ‘subjective good faith’ sufficient to prevent the drawing of an inference of intent to mislead,” Critikon , 120 F.3d at 1257, but our case law does not foreclose the possibility, id. (“No single factor or combination of factors can be said always to require an inference of intent t o mislead[.]”)

. Therefore, while “smoking gun” ev idence is not require d in order to fin d intent to deceive, “the involv ed conduct, viewed in light of all the evidenc e, including evidenc e indicative of good faith , must indicate sufficient cul pability to require a finding of intent to deceive.” Kingsd o wn Med. Consultant s Ltd. v. Hollister, Inc. , 863 F.2d 867, 876 (Fed. Cir. 1988) ( en banc ) (emphasis added); see also Par agon Podiatry Lab., Inc. V. KLM Labs., Inc. , 984 F.2d 1182, 1189-90 (Fed. Cir. 1993). In this case, Vasotec® is of relatively high materiality. 19 Claim 16, for example, recites a method of contacting an ACE inhibi tor with an alkali or alkaline earth metal carbonate and a sacc haride, and the Vasot e c® formulation inc l udes enalap r il, sodium bicarbonat e, and a saccharide. Claim 16 therefore, at least on its face, appears to read on much of the Vasotec® formulation. 20 However, after hearing all the evidence and, specifically, the testimony of Dr. Murthy and Dr. Harris, the tr ial court concluded that the

19 It is not clear exactly how material the district court considered Vasotec®. The court characterized it as “highly ma terial” at the summary judgment stage, Summary Judgment , 289 F. Supp. 2d at 536, but then seemed to back off this statement after hearing the ev idence presented at trial, Bench Trial Opin ion , 2004 WL 1498162, at *10 (“Whether Vaso tec was as ‘highly material’ as stated in [the summary judgment] opinion is s ubject to question in v i ew of the facts developed at the trial.”). 20 That is bec ause claim 16 appear s to simply claim the ingredients used to make the ACE inhibit o r formulation. It does not, for example, place lim itations on h o w the ingredients are specif ically c o mbined or what it is t hat the ingredients do to stabiliz e the ACE inhibitor.

04-1506 33inventors acted with subjective good faith in not disclosing Vasot e c®. The court found that they did not disc lose Vasotec® because, at the t i me of filing for the ’450 patent, they simply did not think it had any relevance to their application. In other words, they did not appreciate its materiality. See Molins , 48 F.3d at 1178 (holding that the patentee must be aware of both the reference and its materi ality). They knew Vasotec ® contained sodium bicarbonat e, but they did not know how sodium bicarbonat e functioned in Vasotec® or that “alkali or alkaline earth metal carbonate” include d bicarbonat e. Bench Trial Opin ion , 2004 WL 14981 62, at *11-12 (f inding Dr. Murthy and Dr. Harris “completely credible” witnesses). We cannot say that the district court committed clear error in assessing the credi bility of these witne sses and finding an absence of deceitful intent. Teva argues that, even assuming the Wa rner-Lambert scientists did not know how to stabilize Vaso tec®, the patentees still committed inequit able cond u c t because claims 16 and 17 nev ertheless read on Vasotec®. This, according to Teva, is because the claims simply require “contacting” an ACE inhibitor with a metal carbonate and a saccharide. Teva als o points out that the or iginally filed c l aim s were n o t limited to carbonates , but merely referred to “alkali and alkaline earth metal salts ,” and that this court’s decision in Schwarz Pharma construed “carbonate” to include “bicarbonate.” The problem with this argument is that t he district court, afte r hearing testimony and making credibility determinations, found t hat the Warner-Lambert scientists did not use sodium bicarbonate for anything other t han adjusting the pH of quinapril during the stage one investigations, and that their subsequent failure to disclose Vasotec® was the result of their good-faith belief that Vasotec® did not relate to their claimed invention.

04-1506 34Id. at *12. Dr. Murthy specifically testified to the fact that he did not think claims 16 or 17 included sodium bicarbonate: Because I took [“[a] suitable am ount of an alkali or alkaline earth metal salt”] to mean mo stly carbonates because those are the ones that worked. There was no bicarbonat e that has worke d for us in our efforts to stabilize the product, so we did not have any bicarbonate in mind.

. . . . We do not--we did not have in mind sodium bicarbonate, otherwise we would have been very s pecific about it. Because our experiments with s odium bicarbonate did not help us in the stabilizing of quina pril. So we didn’t --at least I did not have in m i nd sodi um bicarbonate and to prevent cyclization of quinapril. Id. at *13-14. In short, based on the testi m ony presented at tri a l , the court concl u ded that the Warner-Lambert in ventors were concerned only with c a rbonate ions, had no intention of claiming bicarbonates, and cons equently had no intent to deceive the PTO in not disclosing Vas o tec®. Id. In keeping within our role as an appellate court of review, we cannot say that t he district court committed clear error in making these findings. See Ander son v. Bes s emer City , 470 U.S. 564, 575 (1985) (“[W]hen a trial judge’s finding is bas ed on his decision to cr edit the testimony of one of two or more witnesses, each of whom has to ld a coherent and facially pl ausible story that is not contradicted by extrinsic evidenc e, that finding, if not interna lly inc onsistent, can virtually never be clear error.”); LNP En g’g Plastic s , Inc. v. Miller Waste, Inc. , 275 F.3d 1347, 1361 (Fed. Cir. 2001) (“[T]he district court’s de termination on intent in this cas e depends heavily on the assess ment of wit ness testimony at trial. This court may not reassess, and indeed is incapable of reassessing, witness c r edibility and motive issues o n review.”).

04-1506 35Teva also argues that th is case is analogous to Critikon , where we reversed a district court’s finding of no inequitable condu ct, and that we must consequently reverse the court’s finding in t h is case as well. We di sagree. We first reiter ate that there is no bright line test for determi ning whether inequit able conduct occurred; each case must be assess ed independently. I n any event, how ev er, the facts of this case ar e distinguishable from those in Critikon . In that case, the evidence showed that the patentee was not only “intimatel y familiar” with the withheld prio r a r t, but was repeatedly confronted with it and knew of its particular relevance to the PTO examiner. Critikon , 120 F.3d at 1256-57. In addition, the patent ee “made no effort to offer a good faith explanation of why [the prior art] was never cited, but merely offered conclusory statements that t he reference was cumulative.” Id. at 1257. H e re, by contrast, the district court’s finding s do not su ggest that the patente e s were “in t imately familiar” with Vasotec® or knew of its potential relevance to the PTO. On the c ontrary, the evidence, particularly with respect to Warner-Lambert’ s abandonment of Vasotec® after the failed pH studies, suggests that the patentees had only limite d familiarit y with the Vasotec ® formulation. This is not surprising c ons idering that Merck maintained its sodium bicarbonat e stabilization process as a trade se cret. Perhaps most importantly though, unlik e the situation in Critikon , Warner-Lambert, through Dr . Murthy and Dr. Harris, offered a plausible, good faith explanation for why Vasotec® was not cited to the PTO. Accordingly, given the district c ourt’s view of the ev idence, we do not think the facts of this case necessarily require a finding of intent to deceive.

04-1506 36CONCLUS ION We hold that there are genuine issues of material fact as to enablement and infringement of the ’450 patent . We therefor e reverse the district court’ s grant of summary judgment on the issue of enablement with respect to claims 1, 4- 10, 12, 16, and 17, and on the issue of in fringement of claims 1, 4- 10, and 12, the claims wit h respect to which Tev a challenges the judgment of infringement. The case is remanded to the distri ct court for further proceedings on those issues. However, we see no error in the district court’s determination that t he ’450 patent is not unenforceable by reason of inequitable conduct

. We therefore affirm the court’ s judgment on that issue. COSTS Each party shall bear its own costs. AFFIRMED-IN-PART , R E VER SED -IN

- PAR T , and REM A NDED

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