PTAB

IPR2018-00168

FlatWing Pharmaceuticals, LLC v. Anacor Pharmaceuticals, Inc.

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1. Case Identification

2. Patent Overview

  • Title: Boron-Containing Small Molecules
  • Brief Description: The ’938 patent claims a method of treating human onychomycosis (a fungal toenail infection) 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 and 2 are obvious over Austin in view of Brehove.

  • Prior Art Relied Upon: Austin (WO 1995/033754) and Brehove (Application # 2002/0165121).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Austin disclosed the exact compound claimed in the ’938 patent, tavaborole, and identified it as a preferred antifungal effective against Candida albicans, a known cause of onychomycosis. Brehove taught the topical application of other boron-containing compounds to treat human onychomycosis, including infections caused by T. rubrum and T. mentagrophytes (as recited in dependent claim 2). Brehove also demonstrated that its boron compounds, used as industrial biocides (BioborJF®), were safe and effective for human topical treatment.
    • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine the teachings by substituting the superior, low-molecular-weight antifungal (tavaborole from Austin) for the active ingredients in Brehove's therapeutic method. The motivation stemmed from seeking a more effective treatment; tavaborole's lower molecular weight suggested better nail penetration, and its known efficacy against C. albicans was predictive of efficacy against other onychomycosis pathogens. Brehove provided real-world proof that an industrial fungicide could be successfully and safely adapted for human therapeutic use, overcoming potential concerns.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because both references involved using boron-based compounds as fungicides. The structural similarities and disclosed antifungal activity against onychomycosis-causing pathogens indicated that substituting tavaborole into Brehove’s topical formulation would successfully treat the claimed infection.

Ground 2: Obviousness over Austin and Freeman - Claims 1 and 2 are obvious over Austin in view of Freeman.

  • Prior Art Relied Upon: Austin (WO 1995/033754) and Freeman (WO 2003/009689).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground presented Freeman as an alternative to Brehove. Like Brehove, Freeman disclosed methods of treating onychomycosis in humans by topically applying boron-containing compounds (specifically, phenyl boronic acid and its derivatives). Freeman explicitly identified T. rubrum as a target pathogen. As in the first ground, Austin supplied the specific compound, tavaborole, and demonstrated its high antifungal potency.
    • Motivation to Combine: The motivation was nearly identical to that in Ground 1: a POSITA would replace the active ingredient in Freeman (phenyl boronic acid) with the structurally similar and highly potent tavaborole from Austin to create an improved topical treatment. The motivation was to use a known, effective compound in an established therapeutic method. Freeman's disclosure of treating the specific pathogens recited in the ’938 patent provided a direct link.
    • Expectation of Success: A POSITA would expect success for similar reasons as in Ground 1. Both Austin and Freeman taught that boron compounds are effective antifungals. Given tavaborole's structural similarity to Freeman's compounds and its demonstrated potency, a POSITA would reasonably expect that its incorporation into Freeman's topical treatment methods would be effective against the target pathogens.

Ground 3: Obviousness over Austin, Brehove/Freeman, and Samour - Claims 3-6 are obvious over Austin in view of Brehove, Freeman, and Samour.

  • Prior Art Relied Upon: Austin (WO 1995/033754), Brehove (Application # 2002/0165121), Freeman (WO 2003/009689), and Samour (Patent 6,224,887).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground added Samour to the combinations in Grounds 1 and 2 to teach the specific formulation limitations in dependent claims 3-6. Specifically, claim 3 requires a 5% w/w solution of tavaborole, and claims 4 and 6 require the inclusion of ethanol and propylene glycol. Samour disclosed topical nail lacquer formulations for treating onychomycosis that contained a 5% active ingredient (econazole), ethanol, and propylene glycol.
    • Motivation to Combine: A POSITA, having already been motivated to use tavaborole as the active ingredient per Grounds 1 and 2, would look to the art for suitable formulation strategies. Samour provided an exemplary and effective nail lacquer formulation. A POSITA would be motivated to use Samour's established and durable formulation, including its specific concentration and excipients (ethanol, propylene glycol), with the chosen active ingredient, tavaborole. This represents a simple combination of known elements to achieve a predictable result.
    • Expectation of Success: A POSITA would reasonably expect that formulating tavaborole according to Samour's teachings would be successful. Samour taught that its formulation provides good physical properties and diffusion for an active antifungal. Since Austin and Freeman disclosed concentration ranges that encompassed 5% (e.g., Austin's "especially from 5 to 30%"), and the use of carriers like ethanol and propylene glycol was conventional, a POSITA would expect the resulting composition to be stable and effective.

4. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-6 of the ’938 patent as unpatentable under 35 U.S.C. §103.