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Anacor Pharmaceuticals, Inc. v. Iancu

United States Court of Appeals, Federal Circuit

May 14, 2018


          Appeal from the United States Patent and Trademark Office, Patent Trial and Appeal Board in No. IPR2015-01776.

          Michael N. Kennedy, Covington & Burling LLP, Washington, DC, argued for appellant. Also represented by Evan Smith Krygowski, Andrea Gay Reister.

          Sarah E. Craven, Office of the Solicitor, United States Patent and Trademark Office, Alexandria, VA, argued for intervenor. Also represented by Nathan K. Kelley, Thomas W. Krause, Lore A. Unt.

          James Carmichael, Carmichael IP, PLLC, Tysons, VA, for amicus curiae FlatWing Pharmaceuticals, LLC.

          Before Reyna, Bryson, and Stoll, Circuit Judges.


         This is an appeal from a decision of the Patent Trial and Appeal Board in an inter partes review proceeding. The Board held all of the claims of a patent owned by Anacor Pharmaceuticals, Inc., to be unpatentable for obviousness. Anacor has appealed with respect to only one of the rejected claims. We affirm.



         The patent in suit, U.S. Patent No. 7, 582, 621 ("the '621 patent") is entitled "Boron-containing Small Molecules." The patent is directed to the use of 1, 3-dihydro-5-fluoro-1-hydroxy-2, 1-benzoxaborole, also known as tavaborole, to treat fungal infections. In particular, the patent teaches the use of tavaborole as a topical treatment for fungal infections that develop under fingernails and toenails. When applied topically, tavaborole can penetrate the nail plate and treat the underlying fungal infection.

         The '621 patent teaches that tavaborole can be used to treat a fungal infection known as onychomycosis, which is a disease of the nail that is responsible for approximately half of all nail disorders in humans. '621 patent, col. 28, ll. 18-20. Onychomycosis can be caused by a variety of yeasts and molds, but it is most frequently caused by dermatophytes, a group of fungi that includes the genus Trichophyton and the species Trichophyton rubrum ("T. rubrum"). Id., col. 28, ll. 23-27. Onychomycosis is also sometimes caused by another fungus, a yeast known as Candida albicans ("C. albicans").[1]

         The single claim of the '621 patent that is at issue in this appeal is claim 6, which depends from claims 1 and 4. The three related claims recite as follows:

1. A method of treating an infection in an animal, said method comprising administering to the animal a therapeutically effective amount of 1, 3-dihydro-5-fluoro-1-hydroxy-2, 1-benzoxaborole, or a pharmaceutically acceptable salt thereof, sufficient to treat said infection.
4. The method of claim 1, wherein said infection is onychomycosis.
6. The method of claim 4, wherein said onychomycosis is tinea unguium.

Id., col. 67, ll. 34-38; id., col. 68, ll. 20-21; id., col. 68, ll. 25-26. Tinea unguium is the term for onychomycosis that is caused by a dermatophyte. Id., col. 28, ll. 24-25.


         In 2015, the Coalition for Affordable Drugs X LLC filed a petition requesting inter partes review of all 12 claims of the '621 patent. The Board instituted review and found that the claims would have been obvious in light of the combination of Int'l Pat. Appl. No. PCT/GB95/01206 ("Austin") and U.S. Pat. Appl. No. 10/077, 521 ("Brehove"). Both Austin and Brehove teach the use of boron heterocycles as antifungal agents that inhibit C. albicans, among other fungi. Boron heterocy- cles are organic compounds that contain both boron and carbon in a ring structure.[2]

         Austin teaches the use of oxaboroles-boron heterocy-cles that include a five-member ring containing three carbon atoms, one oxygen atom, and one boron atom-as fungicides. Austin discloses tavaborole as one of a small group of oxaboroles that were tested for antifungal activity and teaches that tavaborole is a highly effective agent that inhibits a variety of fungi, including C. albicans.

         Brehove teaches the use of boron heterocycles in a topical composition to treat onychomycosis. Specifically, two dioxaborinanes-boron heterocycles that include a six-member ring containing three carbon atoms, two oxygen atoms, and one boron atom-were determined through in vitro testing to have powerful potency against C. albicans. Brehove also reports the results of five in vivo tests, each involving a single individual, in which the individual's onychomycosis was successfully treated by the topical application of Brehove's two dioxaborinanes. Brehove does not identify whether each individual's onychomycosis was caused by C. albicans or some other microorganism, such as a dermatophyte.

         The petition posited that the combination of Austin and Brehove would have rendered all the claims of the '621 patent obvious. According to the petition, a person of ordinary skill would have had a reason to combine Austin and Brehove because the compounds in both references are boron heterocycles that are effective as fungicides and, in particular, in inhibiting C. albicans. The petition argued that a skilled artisan would have expected that those compounds would share other fungicidal activity, such as treating onychomycosis caused by dermatophytes. In addressing claim 6, the petition referred to Brehove's in vivo tests, which reported the successful use of Bre-hove's compounds to treat onychomycosis, a condition that is most often caused by dermatophytes. In addition, the petition pointed out that tavaborole has a lower molecular weight than the Brehove compounds, and would therefore be expected to be more likely than those compounds to penetrate the nail barrier at lower concentrations.

         In its patent owner's response, Anacor argued that the combination of Austin and Brehove would not disclose treating onychomycosis caused by a dermatophyte, and that a person of ordinary skill would not have combined Austin and Brehove because they concern structurally different compounds. In addition, Anacor argued that a person of ordinary skill would not have had an expectation of success in treating a dermatophyte infection with tavaborole, because such a person "could not have predicted activity against dermatophytes based on activity against a yeast such as C. albicans."

         In support of that argument, Anacor cited an article by Dr. Rina Segal ("Segal").[3] Among other things, Anacor noted that the Segal article reported that a compound known as terbinafine was very effective against dermato- phytes but had "variable and species-dependent" effectiveness against different species of the Candida genus.

         The petitioner also relied on Segal, introducing that article during the deposition of the petitioner's expert, Dr. Narasimha Murthy. In his deposition, Dr. Murthy explained that terbinafine was effective against both derma-tophytes and various Candida species. Dr. Murthy testified that the information in the Segal article supported his opinion that a person of ordinary skill would have understood that "most ...

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