PTAB

IPR2015-01205

Akorn Inc v. Senju Pharmaceutical Co Ltd

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Compositions Containing Difluprednate
  • Brief Description: The ’319 patent relates to ophthalmic, nasal, or ear drop emulsions comprising the steroid difluprednate, an oil, water, and an emulsifier. The compositions are intended for treating inflammation and allergies.

3. Grounds for Unpatentability

Ground 1: Obviousness over Kimura and Ding - Claims 1-4, 6-10, 12-14, and 18 are obvious over Kimura 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 every element of the challenged claims. Kimura taught using the steroid difluprednate in an ophthalmic suspension, but its formulations suffered from known drawbacks like large particle size causing irritation, poor stability (caking), and inconsistent dosing. Ding taught a superior ophthalmic emulsion vehicle—specifically containing castor oil, water, and polysorbate 80—designed to solve these exact problems for poorly water-soluble drugs, including steroids. Petitioner asserted that substituting Kimura’s active drug into Ding’s well-known and advantageous vehicle rendered the claimed emulsion obvious. For the dependent claims, Petitioner argued that a Person of Ordinary Skill in the Art (POSITA) would arrive at the claimed component ratios (claims 2-4) through routine optimization by combining the exemplary difluprednate concentration from Kimura with the exemplary emulsion formulations of Ding. Similarly, Ding’s explicit use of polysorbate 80 met the surfactant limitations (claims 6-9), and its disclosure of dispersing an oil phase in water taught the claimed oil-in-water type emulsion (claims 10 and 12-14).
    • Motivation to Combine: A POSITA would combine the references to solve the well-documented problems of Kimura’s suspension. The art recognized that aqueous suspensions caused ocular irritation, had poor bioavailability, and were physically unstable. Ding provided a known solution by teaching an emulsion vehicle that offered improved comfort, dose uniformity, and better drug penetration for steroids. The desire to formulate a known effective drug (Kimura’s difluprednate) into a known superior delivery vehicle (Ding’s emulsion) to achieve predictable benefits provided a strong motivation to combine.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success. Ding explicitly taught that its emulsion was suitable for poorly water-soluble steroids like prednisolone acetate, a close structural and functional analog to difluprednate. The process of preparing an emulsion by combining an oil phase with an aqueous phase was a standard, well-understood technique requiring no more than ordinary skill. The ’319 patent itself conceded that its composition is prepared "according to a known method." Therefore, achieving a stable and effective difluprednate emulsion was a predictable result.
    • Key Aspects: The core of the petition's argument was that the claimed invention represented a simple substitution of one known element (difluprednate) into another known system (an ophthalmic emulsion vehicle) to obtain predictable results and solve known problems, which is the hallmark of obviousness. Petitioner also contended that the Patent Owner’s arguments of unexpected results during prosecution were flawed because they failed to compare the invention to the closest prior art (Ding) and because improved bioavailability was an expected outcome of using an emulsion over a suspension.

4. Key Claim Construction Positions

  • "Emulsion": Petitioner proposed the plain and ordinary meaning: a mixture of two or more immiscible liquids (e.g., oil and water) where one is dispersed in the other and stabilized by an emulsifier. This construction was central to arguing that Ding, which teaches an oil-in-water composition, was directly applicable prior art.
  • "Emulsifier" and "Surfactant": Petitioner argued that an "emulsifier" is a chemical agent that promotes and stabilizes an emulsion, and that the term encompasses "surfactants," as stated in the ’319 patent’s specification. This construction allowed Petitioner to map Ding’s disclosure of polysorbate 80 (a known surfactant) directly onto the "emulsifier" limitation of independent claim 1 and the more specific surfactant limitations of claims 6-9.
  • "Parts by weight": Petitioner asserted this term should be understood to represent a ratio of the weight of a given component (oil, water, or emulsifier) to the weight of difluprednate. This construction was necessary for Petitioner to demonstrate, through calculations, how combining exemplary concentrations from Kimura and Ding would result in ratios falling within the ranges recited in dependent claims 2-4.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-4, 6-10, 12-14, and 18 of Patent 6,114,319 as unpatentable under 35 U.S.C. §103.