PTAB

IPR2014-00377

Purdue Pharma LP v. Depomed Inc

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Gastric Retentive Oral Dosage Forms
  • Brief Description: The ’280 patent relates to a controlled-release oral dosage form for high-solubility drugs. The dosage form comprises a solid polymeric matrix of one or more hydrophilic, swellable polymers designed to swell in the stomach to a size that promotes gastric retention during the fed mode.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1, 8-9, 13-14, and 45-46 by Baveja

  • Prior Art Relied Upon: Baveja, S.K. et al., “Zero-order release hydrophilic matrix tablets of β-adrenergic blockers,” International Journal of Pharmaceutics, 39 (1987) 39-45.
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Baveja, a 1987 journal article, explicitly discloses every compositional element of independent claim 1. Baveja describes controlled-release tablets made from a solid matrix of hydroxypropylmethylcellulose (HPMC), a swellable polymer, and a highly soluble drug (alprenolol HCl or metoprolol tartrate). The drug-to-polymer weight ratios disclosed in Baveja (e.g., 1:2 and 1:3) fall squarely within the claimed range of 15:85 to 80:20. Petitioner further contended that the functional limitations of claim 1—swelling to a size sufficient for gastric retention, retaining at least 40% of the drug after one hour, releasing substantially all of the drug, and remaining substantially intact—are inherent properties of Baveja's disclosed formulations. This was supported by expert testimony and new dissolution and swelling studies performed on re-creations of Baveja's formulations.
    • Key Aspects: Petitioner emphasized that Baveja was not considered by the Examiner during the original prosecution.

Ground 2: Anticipation of Claims 1, 8-9, 13-14, and 45-46 by Colombo

  • Prior Art Relied Upon: Colombo, P. et al., “Drug release modulation by physical restrictions of matrix swelling,” International Journal of Pharmaceutics, 63 (1990) 43-48.
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Colombo (1990) discloses a controlled-release oral dosage form comprising the high-solubility drug diltiazem HCl dispersed in an HPMC matrix. The disclosed drug-to-polymer weight ratio of approximately 1:1 falls within the claimed range. Petitioner asserted that Colombo’s tablets, which swell continuously and remain intact for over six hours, inherently meet the functional requirements for gastric retention when administered in the fed mode. Data in Colombo shows the tablets retain approximately 65% of the drug after one hour, satisfying the “at least 40%” limitation. The arguments for dependent claims followed from the disclosure of HPMC as the polymer.

Ground 3: Obviousness of Claims 1, 8-9, 13-15, 45, and 46 over Baveja in view of the ’837 and ’548 Patents

  • Prior Art Relied Upon: Baveja, Shell (Patent 5,582,837), and Klimesch (Patent 4,871,548).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that even if Baveja’s disclosure of certain functional properties is considered inherent rather than explicit, a person of ordinary skill in the art (POSA) would have found it obvious to arrive at the claimed invention. Baveja provides the core formulation of a high-solubility drug in a swellable HPMC matrix at the claimed ratios. The ’837 and ’548 patents remedy any alleged deficiency by explicitly teaching the gastric-retentive properties of such HPMC-based formulations.
    • Motivation to Combine: A POSA starting with Baveja’s formulation to achieve controlled release would be motivated to consult references like the ’837 and ’548 patents to optimize and confirm gastric retention. The ’837 patent explicitly teaches that swellable particles of alkyl-substituted celluloses (like HPMC) will swell to a size that promotes retention in the stomach, particularly in the fed mode, and will maintain their physical integrity. Similarly, the ’548 patent teaches that high molecular weight cellulose ethers provide gastric retention and swell extensively. The combination addresses the common goal of creating a gastric-retentive dosage form using known, predictable polymer technology.
    • Expectation of Success: A POSA would have had a high expectation of success because combining these teachings involves using well-known polymers (HPMC) for their known properties (swelling, controlled release, gastric retention) to achieve a predictable result.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including grounds based on Colombo in view of the ’837 and ’548 patents, and various combinations including Kim (a 1995 journal article on PEO matrices) and the ’453 patent (disclosing PEO formulations).

4. Key Claim Construction Positions

  • "releases substantially all of said drug": For the purposes of the petition, Petitioner proposed construing this term and its variants (e.g., "within about ten hours") to mean "at least 80% of the drug has been released." This construction was based on a similar construction adopted by a district court for a related patent and was argued as critical to demonstrating that the prior art met the release profile limitations.
  • "gastric fluid": Petitioner adopted a prior district court construction, defining the term as "[b]oth the fluid in the stomach and simulated or artificial fluids recognized by those skilled in the art as a suitable model for the fluid of the human stomach."

5. Key Technical Contentions (Beyond Claim Construction)

  • Inherent Properties: A central technical contention across multiple grounds was that the claimed functional limitations (e.g., swelling to a size exceeding the pyloric diameter, retaining >40% drug at one hour, remaining intact) are not novel inventive features but are inherent properties of the prior art compositions. Petitioner argued that discovering a previously unappreciated property of an old composition does not make that old composition patentable.

6. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 8-15, 43, 45, and 46 of the ’280 patent as unpatentable under 35 U.S.C. §§ 102 and/or 103.