IP Law Daily Infringement ruling over time-release muscle relaxant was based on erroneous claim construction
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Thursday, January 4, 2018

Infringement ruling over time-release muscle relaxant was based on erroneous claim construction

By Thomas Long, J.D.

Because the federal district court in Wilmington, Delaware, made a claim construction error, its ruling that a generic version of the muscle relaxant drug AMRIX® infringed two patents covering the brand-name drug has been vacated by the U.S. Court of Appeals for the Federal Circuit. In the appellate court’s view, the district court should have construed the claim term "extended release coating" to require a continuous outer film, as taught by the intrinsic evidence. The district court had rejected the defendant’s argument that the generic product’s "matrix" time-release system did not infringe the "membrane-based" system described by the patents. The infringement determination depended on the district court’s finding that the generic product met the claim limitation. Therefore, the infringement finding was vacated and the case was remanded for further proceedings in light of the correct claim construction (Aptalis Pharmatech, Inc. v. Apotex Inc., January 4, 2018, Stoll, K.).

Patents-in-suit. Plaintiffs Aptalis Pharmatech, Inc., and Ivax International GmbH filed suit against generic drug makers Apotex Inc. and Apotex Corp. (collectively, "Apotex") after Apotex filed an Abbreviated New Drug Application seeking approval to market its generic drug. The plaintiffs owned U.S. Patent Nos. 7,790,199 ("the ’199 patent") and 7,829,121 ("the ’121 patent"), both titled "Modified Release Dosage Forms of Skeletal Muscle Relaxants." The extended release formulation disclosed by the patents allowed patients to obtain relief from muscle spasms for 24 hours from a single dose of the medication, rather than the three daily doses required with prior art formulations.

Sharing a common specification, the patents-in-suit were directed to oral formulations of the skeletal muscle relaxant drug cyclobenzaprine hydrochloride ("cyclobenzaprine") having extended release coatings. They disclosed "a modified release, multi-particulate dosage form of a skeletal muscle relaxant comprising one or more bead populations which provides an extended release profile of the active under in vitro conditions closely mimicking the profile simulated from pharmaco-kinetic modeling." Claim 1 described, among other things, an extended release coating comprising a water-insoluble polymer membrane surrounding the core particle of the extended release bead. The parties referred to this extended release profile as a "membrane system." Generally, in a membrane system, a water insoluble polymer coating was applied onto an active-containing core.

Accused generic product. Apotex produced a generic product consisting of an alternative extended release profile, referred to as a "matrix system." In a matrix system, a water insoluble polymer was mixed together with the drug and compacted into a tablet. The Apotex generic product contained a water-insoluble polymer used to provide extended release of cyclobenzaprine. According to Apotex’s correspondence with the Food and Drug Administration, the generic product and AMRIX® used distinct drug release mechanisms and formulation strategy. In addition, Apotex represented that the pellets encapsulated inside AMRIX® used a membrane-reservoir system to control the drug release rate, whereas Apotex’s products used a polymeric matrix-based dosage form. The distinction between these extended release profiles was the key issue in the infringement suit.

Claim construction. The parties disputed the meaning of the language "an extended release coating comprising a water insoluble polymer membrane surrounding said core," which was found in every asserted claim. Because the district court issued its claim construction order, the parties stipulated that part of the disputed term—"a water insoluble polymer membrane surrounding said core"—meant "a water insoluble polymer covering that surrounds the active core." The district court subsequently construed "extended release coating," the remainder of the disputed claim term, as "[a] layer of any substance that is applied onto the surface of another, the purpose of which is to delay the release of a drug in order to maintain the drug at therapeutically effective concentrations over an extended period of time." Applying this claim construction, the district court found that Apotex’s generic product contained an extended release coating and infringed the asserted claims of the ’199 and ’121 patents. Apotex appealed the claim construction and the infringement finding.

The Federal Circuit began its analysis by noting that the claim language recited an "extended release coating comprising a water insoluble polymer membrane surrounding said [active-containing] core" (emphases added). In the appellate court’s view, it was clear that the coating must surround the core. This connoted a continuous coating—that is, one that covered the entire surface of the core. Because the extended release coating was to surround the core, the claim language suggested that the coating must be located outside of the core. The appellate court therefore adopted a construction requiring a "continuous outer film applied onto the surface of the active-containing core." This construction was bolstered by the fact that the specification made frequent references to applying the extended release coating "onto" the active-containing core. In addition, the specification demonstrated that the inventors were able to describe a non-continuous coating when they so desired, because the specification referred to prior art that disclosed the application of a water impermeable coating onto a core followed by the creation of apertures in the coating. Moreover, the prosecution history contained a declaration indicating that the patented formulation involved a continuous film.

Accordingly, the Federal Circuit concluded that the district court erred in construing the claims, and it vacated and remanded the district court’s infringement finding for further proceedings consistent with the correct claim construction.

The case is No. 2017-1344.

Attorneys: John R. Lane (Fish & Richardson, PC) for Aptalis Pharmatech, Inc. and Ivax International GmbH. William R. Zimmerman (Knobbe, Martens, Olson & Bear, LLP) for Apotex Inc. and Apotex Corp.

Companies: Aptalis Pharmatech, Inc.; Ivax International GmbH; Apotex Inc.; Apotex Corp.

MainStory: TopStory Patent FedCirNews

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