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.
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.
Carmichael, Carmichael IP, PLLC, Tysons, VA, for amicus
curiae FlatWing Pharmaceuticals, LLC.
Reyna, Bryson, and Stoll, Circuit Judges.
BRYSON, CIRCUIT JUDGE.
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.
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
'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.
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
4. The method of claim 1, wherein said infection is
6. The method of claim 4, wherein said onychomycosis is tinea
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.
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
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.
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.
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.
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.
support of that argument, Anacor cited an article by Dr. Rina
Segal ("Segal"). 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.
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 ...