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Duramed Pharmaceuticals, Inc. v. Paddock Laboratories

June 2, 2010


The opinion of the court was delivered by: Sand, J.


In this patent infringement action, Plaintiff Duramed Pharmaceuticals, Inc. (now Teva Women's Health, Inc.) ("Duramed") brings a motion for partial summary judgment, and Defendant Paddock Laboratories, Inc. ("Paddock") brings a motion for summary judgment of non-infringement. Duramed holds a patent that it contends covers its product Cenestin, a conjugated estrogen tablet used in hormone replacement therapy. Duramed contends that Paddock infringed its patent when Paddock sought to manufacture and market a generic version of Cenestin. In order to succeed on its patent infringement claim, Duramed must prove that the "moisture barrier coating" ("MBC") in Paddock's tablet is equivalent to Cenestin's MBC. Paddock counters that Duramed's actions in prosecuting its patent before the Patent and Trademark Office ("PTO") estop Duramed from asserting equivalency.

The Court finds that the doctrine of prosecution history estoppel bars Duramed from relying on the doctrine of equivalents to prove infringement, thereby defeating Duramed's patent infringement claim. Accordingly, Duramed's motion is denied, and Paddock's motion is granted in part.

I. Background

The products in question in this case are conjugated estrogen pills used in hormone replacement therapy to treat menopause symptoms. In the early 1990s, the FDA withdrew its approval for generic versions of Wyeth Pharmaceutical's patented conjugated estrogen product Premarin due to concerns that overly rapid dissolution of the pills could be harmful. (Duramed 56.1 ¶ 24.) In response, Duramed's inventors sought to create a pill with a suitable dissolution profile to compete with Premarin. They did so by designing a pill that controlled the release rate of the estrogen, prevented the estrogen from disintegrating through contact with excess water during storage, and limited stress on the pill's moisture barrier coating to prevent cracking. (Duramed 56.1 ¶¶ 10-19.)

On July 25, 1996, Duramed applied for a patent on its invention. The patent application included one independent claim, claim 1, and 27 additional dependent claims. In the independent claim, Duramed originally claimed a tablet using any type of moisture barrier coating. (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074850) (claiming "[a] pharmaceutical composition . . . wherein said solid unit dosage form is coated with a moisture barrier coating."). Dependent claim 7 of the original patent application also specifically claimed "[a] pharmaceutical composition of claim 1 wherein said moisture barrier coating comprises ethylcellulose." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074851.) Duramed then withdrew certain claims, and the patent examiner then rejected all remaining claims, including claim 1 and claim 7, as obvious in light of U.S. Patent No. 5,547,948 ("Barcomb"). (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074895-96.) The examiner explained that "Barcomb teaches . . . tablets having at least one coating . . . . Such coatings would read on the instantly claimed ethyl cellulose as a moisture barrier." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074895-96.)

On November 30, 1998, the patent examiner conducted an in-person interview with Duramed, and suggested three amendments that would enable it to overcome the prior art and secure the patent. The interview summary stated that the "examiner suggests amending claim 1 to require the tablet to be substantially free of 'inorganic excipients' (which lead to cracking of coat) and insert limitations of claims 7 and 9 into claim 1. These limitations overcome[] art and render[] claims allowable." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074900.) The examiner's suggestion was thus that Duramed insert three further limitations into its overly broad independent claim to make the claim more specific: (1) the pill must be substantially free of inorganic excipients; (2) the pill must have a "moisture barrier coating compris[ing] ethylcellulose" (from dependent claim 7); and (3) the pill must comprise "about 30-70% gel-forming organic excipient and about 30-70% non-gel forming organic excipient by weight (from dependent claim 9). (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074851, 900.)

Duramed made the three suggested amendments "[i]n response to the Office Action dated June 4, 1998 [(the rejection)] and an Examiner's interview of November 30, 1998." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074902.) Dependent claims 7 and 9 were deleted, and their limitations were added to the independent claim. (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074902.) In support of its amendments, Duramed argued that "the indication that a moisture barrier may be used [in the prior art Barcomb patent] does not suggest, or read upon, the claimed use of ethyl cellulose as a moisture barrier in combination with the claimed formulations comprising conjugated estrogens coated onto organic excipients, forming compositions having less than about 2.5% free water, which are coated with a moisture barrier over the tableted formulation." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074906) (emphases in original). In response to Duramed's amendments, the examiner allowed certain amended claims, including the independent claim. (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074908.) In the notice of allowability mailed December 23, 1998, the examiner remarked that "applicants have adopted the suggestion made at the personal interview of November 30, 1998." (Paddock Ex. 36, '638 file history, DPI_CENESTIN0074911.)

The PTO granted U.S. Patent 5,908,638 ("the '638 patent") on June 1, 1999. Duramed began selling Cenestin that same year, and it was the only "modified-release conjugated estrogen alternative to Premarin" on the market at the time. (Duramed 56.1 ¶ 31.)

In October 2008, Paddock filed an Abbreviated New Drug Application ("ANDA") with the Food and Drug Administration ("FDA"), which sought approval to sell a generic version of Duramed's Cenestin tablets. (Duramed 56.1 ¶ 38.) Under the Hatch-Waxman Act,*fn1 a company may seek expedited approval to market a generic version of a drug previously approved by the FDA by filing an ANDA. Bayer AG v. Elan Pharm. Research Corp., 212 F.3d 1241, 1244 (Fed. Cir. 2000) (citation omitted). If the generic company can show "bioequivalence" between its proposed generic drug and the previously approved drug, it may forego safety and efficacy studies. Id. (citation omitted). Paddock's ANDA certified that Duramed's patent was invalid and that the patent would not be infringed by Paddock's generic drug, and Paddock submitted statutorily required notice letters to Duramed explaining its position. (Compl. ¶¶ 11-15.)

In March 2009, Duramed brought this patent infringement action against Paddock. By filing this lawsuit, Duramed obtained an automatic 30-month stay of FDA approval for Paddock's proposed generic drug. See 21 U.S.C. § 355(j)(5)(B)(iii); 21 C.F.R. § 314.107(b)(3). The automatic stay remains in effect until the district court enters a judgment of non-infringement or patent invalidity, or the expiration of thirty months, whichever occurs first. See 21 U.S.C. § 355(j)(5)(B)(iii)(I); 21 C.F.R. § 314.107(b)(3).

The parties agree that the MBC in Paddock's proposed generic tablets does not literally infringe the '638 patent. (Duramed 56.1 ¶ 51.) The '638 patent teaches a moisture barrier comprising ethylcellulose, while Paddock's proposed generic tablets use a polyvinyl alcohol ("PVA") MBC, marketed under the name Opadry AMB. Because Paddock's MBC does not literally infringe Duramed's patent, Duramed must rely on the doctrine of equivalents to succeed on its patent infringement claim. "[F]or a court to find infringement, the plaintiff must show the presence of every element or its substantial equivalent in the accused device. A patentee must prove that the accused product contain(s) each limitation of the claim or its equivalent." Terlep v. Brinkmann Corp., 418 F.3d 1379, 1384 (Fed. Cir. 2005) (citation and internal quotation marks omitted). Paddock argues that Duramed abandoned all equivalents to ethylcellulose MBCs pursuant to the doctrine of prosecution history estoppel.

II. Standard of Review

Summary judgment is warranted "if the pleadings, depositions, answers to interrogatories, and admissions on file, together with the affidavits, if any, show that there is no genuine issue as to any material fact and that the moving party is entitled to judgment as a matter of law." Fed. R. Civ. P. 56(c). A material fact is one that might affect the outcome of a suit under governing law. Kinsella v. Rumsfeld, 320 F.3d 309, 311 (2d Cir. 2003). A "genuine" issue exists when "the evidence is such that a reasonable jury could return a verdict for the nonmoving party." Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 248 (1986). When deciding cross-motions for summary judgment, the Court analyzes each motion on its own merits, drawing all reasonable inferences in the light most favorable to the nonmoving party. ...

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