PTAB

IPR2015-01205

Akorn, Inc. v. SENJU PHARMACEUTICAL CO., LTD

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1. Case Identification

2. Patent Overview

  • Title: Compositions Containing Difluprednate
  • Brief Description: The ’319 patent describes ophthalmic, nasal, or ear drop compositions in the form of an oil-in-water emulsion. The emulsion comprises the steroid difluprednate, an oil, water, and an emulsifier to create a stable and effective delivery vehicle.

3. Grounds for Unpatentability

Ground 1: Claims 1-4, 6-10, 12-14, and 18 are obvious over the ’848 patent in view of Ding.

  • Prior Art Relied Upon: Kimura (Patent 5,556,848) and Ding (WO 95/31211).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of Kimura and Ding disclosed all elements of the challenged claims.
      • Kimura disclosed using the steroid difluprednate in an ophthalmic suspension for treating eye inflammation. However, Kimura’s suspensions suffered from known drawbacks, including large particle size (up to 75 μm) causing ocular irritation, poor physical stability (caking and settling), and inconsistent dosing.
      • Ding disclosed a superior vehicle for poorly water-soluble drugs: an oil-in-water emulsion for ophthalmic use that solved the very problems inherent in suspensions. Ding’s emulsions, which contained castor oil, water, and the emulsifier polysorbate 80, were taught to be physically stable, provide a high comfort level, and have low irritation potential. Ding explicitly taught that its emulsion vehicle was suitable for steroids like prednisolone acetate (a structural analog to difluprednate).
      • Combining Kimura’s active ingredient (difluprednate) with Ding’s superior vehicle (an oil-in-water emulsion) would result in the claimed invention. Independent claim 18, which recites difluprednate, castor oil, water, and polysorbate 80, is directly readable on this combination. Independent claim 1 is broader but also met for the same reasons. The dependent claims reciting component ratios (claims 2-4), specific surfactants (claims 6-9), and an oil-in-water type emulsion (claims 10, 12-14) were all alleged to be obvious variations achievable through routine optimization or direct teachings from Ding.
    • Motivation to Combine (for §103 grounds): A person of ordinary skill in the art (POSA) would combine the teachings of Kimura and Ding to solve the well-known problems of irritation, instability, and poor bioavailability associated with Kimura's difluprednate suspension. Ding expressly provided the solution by teaching a comfortable, stable, and effective emulsion vehicle for ophthalmic steroids, thereby improving dose uniformity and patient comfort.
    • Expectation of Success (for §103 grounds): A POSA would have a reasonable expectation of success because Kimura established difluprednate as a safe and effective ophthalmic steroid, and Ding taught that its emulsion vehicle was suitable for such steroids. The components and methods for creating the emulsion were well-known, and the ’319 patent itself concedes the emulsion is prepared "according to a known method."
    • Key Aspects: Petitioner preemptively rebutted anticipated arguments of nonobviousness based on objective indicia. Petitioner argued that any evidence of "unexpectedly superior results" presented by the Patent Owner during prosecution was flawed because it compared the claimed emulsion to Kimura's inferior suspension, rather than to the closest prior art, which Petitioner asserted is Ding's emulsion. Furthermore, the improved bioavailability and reduced irritation of an emulsion over a suspension were well-documented phenomena in the prior art and thus would have been entirely expected by a POSA, not surprising.

4. Key Claim Construction Positions

Petitioner proposed constructions for several key terms based on their plain and ordinary meaning in the context of the patent and the prior art.

  • "Emulsion": An immiscible mixture of oil and water, stabilized by an emulsifier. Petitioner contended this term covers both oil-in-water and water-in-oil types, but that the patent focuses on oil-in-water (O/W) emulsions, where oil is dispersed in a continuous water phase. This construction is central to applying Ding, which explicitly discloses O/W emulsions.
  • "Emulsifier" and "Surfactant": An "emulsifier" is a chemical agent that promotes the formation of and stabilizes an emulsion. A "surfactant" is a type of emulsifier. This interpretation allows polysorbate 80, a surfactant disclosed in Ding, to satisfy the "emulsifier" limitation of the claims.
  • "Parts by weight": This phrase represents the ratio of the weight of a given component (e.g., oil, water) to the weight of difluprednate. Petitioner argued that the ranges recited in dependent claims 2-4 were not critical and would have been arrived at by a POSA through routine optimization of the formulation taught by the combined references.

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-4, 6-10, 12-14, and 18 of the ’319 patent as unpatentable.