PTAB

IPR2018-00170

FlatWing Pharmaceuticals LLC v. Anacor Pharmaceuticals Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Boron-Containing Small Molecules
  • Brief Description: The ’290 patent discloses methods for treating onychomycosis (toenail fungus) in humans caused by Trichophyton rubrum or Trichophyton mentagrophytes. The method involves topically administering a pharmaceutical composition containing the boron-based compound tavaborole.

3. Grounds for Unpatentability

Ground 1: Obviousness over Austin and Brehove - Claims 1, 4, 7, and 9-10 are obvious over Austin in view of Brehove.

  • Prior Art Relied Upon: Austin (International Publication No. WO 1995/033754) and Brehove (Application # 2002/0165121).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Austin disclosed the claimed active ingredient, tavaborole (1,3-dihydro-5-fluoro-1-hydroxy-2,1-benzoxaborole), and taught its effectiveness as a fungicide against pathogens like Candida albicans. Brehove taught the topical application of different boron-containing compounds to treat human onychomycosis caused by the same pathogens recited in the patent. Petitioner asserted that the claim limitation requiring the method to be "effective to inhibit an aminoacyl tRNA synthetase" was an inherent property of tavaborole's known mechanism of action and not a patentable distinction.
    • Motivation to Combine: A POSITA would combine Austin and Brehove for several reasons. First, both references taught using boron-containing compounds as effective fungicides. Second, both demonstrated efficacy against Candida albicans, which a POSITA would recognize as predictive of efficacy against other onychomycosis-causing fungi. Third, tavaborole from Austin possessed a significantly lower molecular weight than the compounds in Brehove, which would motivate a POSITA to substitute it to achieve better penetration of the nail plate.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because the compounds in Austin and Brehove shared structural similarities (boron heterocycles) and similar fungicidal activity. Furthermore, Brehove demonstrated that an industrial biocide could be safely repurposed for topical human use, mitigating any concern about using the tavaborole compound disclosed in Austin.

Ground 2: Obviousness over Austin, Brehove, and Samour - Claims 2-3, 5-6, 8, and 11-12 are obvious over Austin in view of Brehove and Samour.

  • Prior Art Relied Upon: Austin (WO 1995/033754), Brehove (Application # 2002/0165121), and Samour (Patent 6,224,887).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground built upon the combination of Austin and Brehove to address dependent claims reciting specific formulation details. Samour was introduced because it taught topical nail lacquer compositions for treating onychomycosis with improved physical properties. Specifically, Samour disclosed formulations containing a 5% w/w active ingredient (as required by claims 2 and 5) and the use of carriers such as ethanol and propylene glycol (as required by claims 3 and 6).
    • Motivation to Combine: The motivation was to incorporate the superior active ingredient from Austin (tavaborole) into a known, effective, and durable delivery system for treating onychomycosis. While Brehove provided the general method, Samour provided a specific, optimized nail lacquer formulation that a POSITA would look to for formulating the active compound. This represented a simple substitution of one known antifungal agent for another within an established formulation.
    • Expectation of Success: A POSITA would expect success because formulating active ingredients into topical carriers was a routine and well-understood practice. Samour provided a proven template for a nail lacquer, and Austin taught that a 5% concentration was within its preferred range for tavaborole. The combination was merely the application of known techniques to known compounds for a predictable result.

  • Additional Grounds: Petitioner asserted additional obviousness challenges (Grounds 3 and 4) that were structurally parallel to Grounds 1 and 2. These grounds substituted Freeman (WO 2003/009689), which taught treating onychomycosis with other boron-based compounds, for Brehove and relied on the same theories of motivation and substitution.

4. Key Claim Construction Positions

  • "1,3-dihydro-5-fluoro-1-hydroxy-2,1-benzoxaborole": Petitioner contended this compound, recited in all challenged claims, is the exact same compound disclosed in Austin as 5-fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole, also known as tavaborole. This construction was central to establishing that the primary prior art reference, Austin, disclosed the core inventive element.
  • "inhibit": Petitioner identified that the patent owner defined "inhibiting" during prosecution as "the partial or full blockade of an editing domain of a tRNA synthetase." This construction was used to support the argument that this claimed function is an inherent, unpatentable property of tavaborole when used to treat onychomycosis.

5. Key Technical Contentions (Beyond Claim Construction)

  • Inherency of Mechanism of Action: A central technical contention spanning multiple grounds was that the claimed step of "inhibit[ing] an aminoacyl tRNA synthetase" is not a patentable limitation but rather an inherent result of topically applying tavaborole to treat onychomycosis. Petitioner argued that this is the scientifically understood mechanism by which tavaborole functions as an antifungal agent. Therefore, combining Austin's compound with Brehove's or Freeman's method would necessarily and inherently result in the inhibition of the synthetase, making the limitation obvious.

6. Relief Requested

  • Petitioner requested institution of an inter partes review (IPR) and a final written decision finding claims 1-12 of the ’290 patent unpatentable under 35 U.S.C. §103, followed by their cancellation.