Endo Pharmaceutical Inc v. Depomed Inc

1. Case Identification

• Case #: IPR2014-00652
• Patent #: 6,723,340
• Filed: April 17, 2014
• Petitioner(s): Endo Pharmaceuticals, Inc.
• Patent Owner(s): Depomed, Inc.
• Challenged Claims: 1-5 and 10-13

2. Patent Overview

• Title: Controlled Release Gastric Retentive Drug Dosage Form
• Brief Description: The ’340 patent discloses a controlled-release oral tablet designed for gastric retention. The tablet uses a solid monolithic matrix comprising a combination of poly(ethylene oxide) (PEO) and hydroxypropyl methylcellulose (HPMC) that swells in gastric fluid to a size large enough to be retained in the stomach for prolonged drug release.

3. Grounds for Unpatentability

Ground 1: Obviousness over Shell 1998 Alone - Claims 1-5 and 10-13

• Prior Art Relied Upon: Shell 1998 (International Publication No. WO 98/55107).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Shell 1998 taught all elements of the challenged claims. It described controlled-release dosage forms with a water-swellable polymeric matrix for gastric retention, using a combination of polymers including PEO and HPMC. Petitioner asserted that Shell 1998 also disclosed the claimed molecular weight ranges for PEO (e.g., 4.5M to 10M daltons), viscosity ranges for HPMC (e.g., 100 to 110,000 centipoise), and the required high water solubility for the active drug.
  • Motivation to Combine (N/A): This ground relied on a single reference.
  • Expectation of Success: Petitioner contended that since Shell 1998 explicitly taught combining PEO with an alkyl-substituted cellulose (like HPMC) to create a swellable matrix for gastric retention, a person of ordinary skill in the art (POSA) would have had a high expectation of success in arriving at the claimed subject matter.

Ground 2: Obviousness over Shell 1998 in view of Papadimitriou - Claims 1-5 and 10-13

• Prior Art Relied Upon: Shell 1998 (WO 98/55107) and Papadimitriou (Papadimitriou et al., Swelling Studies on Mixtures of Two Hydrophilic Excipients, S.T.P. Pharma. Sciences, 1993).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Shell 1998 provided the primary framework for a gastric-retentive system using swellable polymers. Papadimitriou was cited as teaching the specific use and swelling properties of binary mixtures of HPMC and PEO for sustained drug delivery. Petitioner asserted that Papadimitriou disclosed PEO and HPMC grades with molecular weights and viscosities squarely within the ranges claimed in the ’340 patent, confirming the suitability of these specific polymers for the application taught in Shell 1998.
  • Motivation to Combine: A POSA, starting with Shell 1998’s teaching of using polymer combinations, would combine its teachings with Papadimitriou because both references shared the common goal of achieving sustained drug release via a swellable polymeric matrix. Papadimitriou provided detailed, empirical data on the swelling behavior of the exact PEO/HPMC combination suggested by Shell 1998.
  • Expectation of Success: The combination was a predictable application of known technologies. Papadimitriou’s successful results with PEO/HPMC mixtures would have given a POSA a strong expectation of success when applying those mixtures to the gastric-retentive system of Shell 1998.

Ground 3: Obviousness over Shell ’837 in view of Papadimitriou - Claims 1-5 and 10-13

• Prior Art Relied Upon: Shell ’837 (Patent 5,582,837) and Papadimitriou (1993 journal article).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Shell ’837 taught a sustained-release dosage form using an alkyl-substituted cellulose (specifically disclosing HPMC) that swells to promote gastric retention. While Shell ’837 focused on cellulose polymers, Petitioner argued it created the same essential framework as Shell 1998. Papadimitriou was again relied upon for its teachings on combining HPMC with PEO to control swelling and drug release properties.
  • Motivation to Combine: A POSA would combine Shell ’837 and Papadimitriou to optimize the swelling properties of the gastric-retentive dosage form. Knowing from Shell ’837 that a swelling HPMC matrix provides gastric retention, a POSA would have looked to related art like Papadimitriou for methods of modifying that matrix, such as by adding PEO, to fine-tune the release profile as taught by Papadimitriou.
  • Expectation of Success: Given that both references operated in the predictable field of polymer science for drug delivery, a POSA would have a reasonable expectation that adding PEO (as studied in Papadimitriou) to the HPMC matrix of Shell ’837 would successfully modify its properties without undue experimentation.
• Additional Grounds: Petitioner asserted additional obviousness challenges based on combinations of Shell ’790 (Patent 5,007,790) in view of Papadimitriou, and the ’548 patent (Patent 4,871,548) in view of Papadimitriou, relying on similar motivations to combine to optimize swellable, gastric-retentive polymer matrices.

4. Key Claim Construction Positions

• "to swell upon contact with gastric fluid to a size large enough to promote gastric retention": Petitioner did not propose a formal construction but argued this limitation should be construed consistently with constructions of similar terms in related litigation involving other Depomed patents. For the purposes of the IPR, Petitioner adopted a construction where the dosage form increases in size due to water ingress such that it remains in the stomach for several hours, while noting it believed the term was indefinite in the co-pending litigation.

5. Key Technical Contentions (Beyond Claim Construction)

• Inherent Properties of Known Compositions: A central contention was that the ’340 patent claimed a well-known pharmaceutical composition (a drug in a PEO/HPMC matrix) by reciting its inherent or functional properties, such as specific swelling rates, viscosity values, and the resulting gastric retention. Petitioner argued that the discovery of a previously unappreciated property of a prior art composition does not render that old composition patentable, and that the claimed properties were already appreciated by those skilled in the art before the patent's filing.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-5 and 10-13 of the ’340 patent as unpatentable under 35 U.S.C. §103.