  United States Court of Appeals
      for the Federal Circuit
              __________________________

                (Serial No. 10/082,772)
IN RE PETER DROGE, NICOLE CHRIST, AND ELKE
                  LORBACH
           __________________________

                      2011-1600
              __________________________

    Appeal from the United States Patent and Trademark
Office, Board of Patent Appeals and Interferences.
               ___________________________

             Decided: September 21, 2012
             ___________________________

    JONATHAN S. FRANKLIN, Fulbright & Jaworski L.L.P.,
of Washington, DC, argued for appellants. With him on
the brief were STEVEN L. HIGHLANDER and SHEILA
KADURA, of Austin, Texas.

    MARY L. KELLY, Associate Solicitor, United States
Patent and Trademark Office, of Alexandria, Virginia,
argued for the Director of the United States Patent and
Trademark Office. With her on the brief were RAYMOND
T. CHEN, Solicitor, and KRISTI L. R. SAWERT, Associate
Solicitor. Of counsel was AMY J. NELSON.
                __________________________

Before NEWMAN, MOORE, and O’MALLEY, Circuit Judges.
IN RE DROGE                                               2


MOORE, Circuit Judge.
    Peter Droge, Nicole Christ, and Elke Lorbach (collec-
tively, Droge) appeal from the decision by the Board of
Patent Appeals and Interferences (Board) affirming the
rejection of claims 29, 30, 32-39, 43-51, and 58 of U.S.
Patent Application No. 10/082,772 (’772 application) as
obvious under 35 U.S.C. § 103. Because the Board cor-
rectly held that the claims would have been obvious over
the prior art, we affirm.
                       BACKGROUND
    The ’772 application is directed to methods and com-
positions for recombining DNA in a eukaryotic cell (i.e., a
cell with a nucleus), such as a human cell. The term
“recombinant DNA” generally refers to DNA from one or
more sources with a sequence that does not occur in
nature. A process called “molecular cloning” is one way to
create recombinant DNA molecules and direct their
replication within a living host cell. This process involves
inserting foreign DNA into a carrier, called a “vector,” and
then introducing the vector into a host cell. The vector
can insert both its DNA and any foreign DNA into the
host cell’s DNA. When the host cell replicates, the vector
with its foreign DNA also replicates. This allows for the
production of a large quantity of the foreign DNA, which
can be used in a wide variety of applications, such as
production of recombinant proteins.
    Viruses that infect bacteria, called bacteriophages, are
commonly used as vectors. One well-known example is
called “bacteriophage λ.” In bacteriophage λ-based vector
systems, a protein called “bacteriophage λ integrase” (or
derivatives thereof) induces and facilitates DNA recombi-
nation. Naturally occurring (wild-type) bacteriophage λ
integrase is called “Int.”
3                                              IN RE DROGE



    One feature of bacteriophage λ that makes it a useful
vector is its ability to perform sequence-specific recombi-
nation, which means that DNA may be inserted, deleted,
or rearranged at a specific location on the target cell’s
DNA. Bacteriophage λ does this by using recognition
sites, which are short sections of DNA that act as guide-
posts for the vector’s insertion into the host cell’s DNA.
During recombination, the recognition site region of the
vector’s DNA will align with a complementary recognition
site region on the host cell’s DNA. The Int enzyme then
cuts both the vector’s and the host cell’s DNA and facili-
tates insertion of the vector’s DNA into the host cell’s
DNA. The DNA recognition sites used in bacterio-
phage λ-based vector systems are referred to as attB,
attP, attR, and attL.
    The Board affirmed the rejection of independent claim
29 of the ’772 application, which the parties agree is
representative of the claims on appeal, as obvious over the
combination of U.S. Patent No. 6,143,530 (Crouzet) and
an article by Christ & Droge (two of the three inventors of
the ’772 application). Claim 29 covers a method of recom-
bining DNA in a eukaryotic cell using modified versions of
wild-type Int. The particular Int mutants used in the
claimed method are called Int-h and Int-h/218. The
claimed recombination method is sequence-specific,
facilitating recombination at either the attB and attP or
the attR and attL recognition sites. Claim 29 recites:
    A method of sequence specific recombination of
    DNA in a eukaryotic cell, comprising:
        (a) providing said eukaryotic cell, said cell
    comprising a first DNA segment integrated into
    the genome of said cell, said first DNA segment
    comprising an [attB, attP, attL, or attR sequence
    or derivative thereof] . . . ;
IN RE DROGE                                                4


        (b) introducing a second DNA segment into
    said cell . . . ;
        (c) further comprising providing to said cell a
    modified bacteriophage lambda integrase Int,
    wherein said modified Int is Int-h or Int-h/218,
    which induces sequence specific recombination
    through said attB and attP or attR and attL se-
    quences.
’772 application, cl.29 (emphasis added).
    The Crouzet reference discloses methods of making
therapeutic DNA molecules using sequence-specific
recombination either in a host cell or in vitro. Crouzet,
col.3 ll.30-34, 59-61. Specifically, Crouzet discloses a
method that uses bacteriophage λ and wild-type Int
protein to insert a foreign DNA sequence into a host cell
using the attB and attP recognition sites. Id. col.4 ll.21-
52, col.5 ll.32-41. Crouzet also teaches that this method
“may be carried out in any type of cell host,” such as
“bacteria or eukaryotic cells (yeasts, animal cells, plant
cells).” Id. col.9 ll.48-60. Crouzet does not disclose use of
modified integrases.
    The Christ & Droge article discloses that the modified
integrase proteins Int-h and Int-h/218 mediate sequence-
specific recombination in prokaryotic cells (i.e., cells with
no nucleus). This reference teaches that, compared to
wild-type Int, the modified proteins Int-h and Int-h/218
have the advantage of an increased binding affinity for
core binding sites present in the att regions. Christ &
Droge also discloses that Int-h and Int-h/218 can perform
recombination in vivo even in the absence of certain
protein co-factors that assist with recombination, such as
the integration host factor (IHF). IHF is present in
prokaryotic cells but not in eukaryotic cells.
5                                              IN RE DROGE



    Based on the teachings of these references, the Board
concluded that because “the wild-type integrase works in
eukaryotic cells, the ordinary artisan would have had a
reasonable expectation of success that [Int-h and
Int-h/218] would also function at some level in eukaryotic
cells.” The Board considered a declaration from one of the
inventors, Dr. Droge (Droge Declaration), which set out
reasons why a person of ordinary skill in the art would
not have had a reasonable expectation of success in using
Int-h and Int-h/218 to induce recombination in eukaryotic
cells. The Board, however, concluded that an article by
Brenda J. Lange-Gustafson and Howard A Nash (Lange-
Gustafson) refuted the assertions in the Droge Declara-
tion. The Board thus held that claim 29 would have been
obvious over the combination of Crouzet and Christ &
Droge. Droge now appeals the Board’s obviousness rejec-
tion of the ’772 application claims. We have jurisdiction
under 28 U.S.C. § 1295(a)(4).
                       DISCUSSION
    Whether an invention would have been obvious under
35 U.S.C. § 103 is a question of law based on underlying
findings of fact. In re Gartside, 203 F.3d 1305, 1316 (Fed.
Cir. 2000). We review the Board’s legal conclusions de
novo and its factual findings for substantial evidence. Id.
Substantial evidence is “such relevant evidence as a
reasonable mind might accept as adequate to support a
conclusion.” Id. at 1312 (citation omitted).
    Droge does not dispute that the Crouzet and Chris &
Droge references, taken together, teach every limitation of
the claimed method. Instead, Droge argues that a person
of ordinary skill in the art would not have had a reason-
able expectation of success in combining the teachings of
these references. Specifically, Droge argues that Christ &
Droge’s disclosure of using the modified integrase proteins
IN RE DROGE                                              6


Int-h and Int-h/218 to facilitate recombination in prokary-
otic cells would not lead a skilled artisan to expect that
these integrases would also work in eukaryotic cells.
Droge contends that the Christ & Droge article teaches
away from the claimed invention because it states that
the recombinant activity of Int-h and Int-h/218 decreases
in the absence of protein co-factors such as IHF, which are
present in prokaryotic cells but not in eukaryotic cells.
    Droge also argues that, even if the combination of
Crouzet with Christ & Droge makes out a prima facie case
of obviousness, the Droge Declaration rebutted it with
additional evidence that a skilled artisan would not have
had a reasonable expectation of success in using Int-h or
Int-h/218 to recombine DNA in eukaryotic cells. The
Droge Declaration explains that the ability of modified
integrases to promote recombination in prokaryotic cells
may be due to two features of those cells: (1) specific
prokaryotic protein co-factors that assist with recombina-
tion, such as IHF; and (2) the particular three-
dimensional structure of DNA in prokaryotic cells. The
Droge Declaration states that it was not obvious that
Int-h and Int-h/218 would work in eukaryotic cells be-
cause they had only been shown to work on DNA with the
three-dimensional structure found in prokaryotic cells
(negatively supercoiled). The declaration states that, at
the time of invention, it was unclear whether these modi-
fied integrases would work on the topologically relaxed
DNA in mammalian cells. Thus, Droge argues the
Board’s rejection should be reversed.
    We conclude that substantial evidence supports the
Board’s determination that a person of ordinary skill in
the art would have had a reasonable expectation of suc-
cess when combining Crouzet and Christ & Droge.
Crouzet discloses that wild-type bacteriophage λ integrase
Int can induce site-specific DNA recombination using the
7                                                IN RE DROGE



attB and attP recognition sites. Crouzet, col.4 ll.21-52, 32-
41. Crouzet further discloses that wild-type Int can
induce recombination in both prokaryotic and eukaryotic
host cells, including animal cells. Id. col.9 ll.48-60 (“The
method according to the invention may be carried out in
any type of cell host. Such hosts can be, in particular,
bacteria or eukaryotic cells (yeasts, animal cells, plant
cells), and the like.”). Although Crouzet does not teach
the use of the modified integrases Int-h and Int-h/218, the
Christ & Droge article supplies this missing element.
Christ & Droge also supplies a motivation to use Int-h
and Int-h/218 in the method taught in Crouzet—these
modified integrases have increased affinity for core bind-
ing sites in the att regions, even in the absence of IHF.
J.A. 773 (“Hence, Int-h/218 exhibits an enhanced ability
to execute recombination on wild-type att sites in the
absence of accessory factors IHF and Xis.”).
    The Lange-Gustafson article provides additional evi-
dence in support of the Board’s determination that a
skilled artisan would have a reasonable expectation of
success. Lange-Gustafson discloses that Int-h “sponsors
reduced but significant levels” of recombination in the
absence of IHF and that, “in the absence of IHF, Int-h
recombines supercoiled and nonsupercoiled [DNA] identi-
cally.” J.A. 889. The article directly contradicts the
assertion in the Droge Declaration that a skilled artisan
would not expect the modified integrases Int-h and
Int-h/218 to work in eukaryotic cells based on the three-
dimensional structure of DNA in those cells. Indeed,
Lange-Gustafson states that Int-h recombines DNA
“identically” regardless of whether its three-dimensional
structure is supercoiled or topologically relaxed. The
Christ & Droge article similarly concludes that neither
supercoiling nor IHF are necessary. J.A. 769 (“Neither
IN RE DROGE                                                 8


supercoiling of attP nor the presence of IHF seems to be
required for catalysis of these chemical reactions.”).
    These disclosures provide substantial evidence sup-
porting the Board’s finding that a person of ordinary skill
in the art would have had a reasonable expectation of
success for using the modified integrases disclosed in
Christ & Droge in place of wild-type Int in the method
taught in Crouzet. “Obviousness does not require abso-
lute predictability of success . . . all that is required is a
reasonable expectation of success.” In re Kubin, 561 F.3d
1351, 1360 (Fed. Cir. 2009) (citing In re O’Farrell, 853
F.2d 894, 903-04 (Fed. Cir. 1988)). Because the references
disclose that wild-type Int mediates recombination in
eukaryotic cells and that Int-h and Int-h/218 can perform
recombination even in the absence of IHF, the Board’s
fact finding that a skilled artisan would have had a rea-
sonable expectation that Int-h and Int-h/218 would medi-
ate recombination in eukaryotic host cells is supported by
substantial evidence. Accordingly, we hold that the Board
correctly concluded that the ’772 claims at issue on appeal
would have been obvious over the prior art. We have
considered Droge’s remaining arguments on appeal and
find them to be without merit.
                        AFFIRMED
