U.S. patent application number 12/402374 was filed with the patent office on 2010-02-25 for antibody variants.
Invention is credited to Yvonne M. Chen, Henry B. Lowman, Yves Muller.
Application Number | 20100047236 12/402374 |
Document ID | / |
Family ID | 22324963 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100047236 |
Kind Code |
A1 |
Chen; Yvonne M. ; et
al. |
February 25, 2010 |
ANTIBODY VARIANTS
Abstract
Antibody variants of parent antibodies are disclosed which have
one or more amino acids inserted in a hypervariable region of the
parent antibody and a binding affinity for a target antigen which
is at least about two fold stronger than the binding affinity of
the parent antibody for the antigen.
Inventors: |
Chen; Yvonne M.; (San Mateo,
CA) ; Lowman; Henry B.; (El Granada, CA) ;
Muller; Yves; (Zepernick, DE) |
Correspondence
Address: |
Genentech, Inc.;Attn: Wendy M. Lee
1 DNA Way
South San Francisco
CA
94080-4990
US
|
Family ID: |
22324963 |
Appl. No.: |
12/402374 |
Filed: |
March 11, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11552445 |
Oct 24, 2006 |
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12402374 |
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10624153 |
Jul 21, 2003 |
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11552445 |
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09440781 |
Nov 16, 1999 |
6632926 |
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10624153 |
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60108945 |
Nov 18, 1998 |
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Current U.S.
Class: |
424/133.1 ;
435/69.6; 530/387.3 |
Current CPC
Class: |
C07K 2317/565 20130101;
A61P 27/02 20180101; C07K 2317/92 20130101; C07K 2317/56 20130101;
C07K 16/22 20130101; A61K 38/00 20130101; A61P 29/00 20180101; A61P
43/00 20180101; C07K 16/24 20130101; B65H 2801/87 20130101; C07K
2317/24 20130101; A61P 9/10 20180101; A61P 11/00 20180101; C07K
2299/00 20130101; A61P 35/00 20180101; C07K 2317/55 20130101; C07K
16/005 20130101; A61P 17/06 20180101; A61P 5/14 20180101; C07K
16/00 20130101; C07K 2317/73 20130101; C07K 2317/14 20130101; C07K
2317/76 20130101; A61P 9/00 20180101; A61P 27/06 20180101 |
Class at
Publication: |
424/133.1 ;
530/387.3; 435/69.6 |
International
Class: |
A61K 39/00 20060101
A61K039/00; C07K 16/00 20060101 C07K016/00; C12P 21/06 20060101
C12P021/06 |
Claims
1. An antibody variant of a parent antibody, which antibody variant
comprises an amino acid insertion in a hypervariable region of the
parent antibody and has a binding affinity for a target antigen
which is at least about two fold stronger than the binding affinity
of the parent antibody for said antigen, wherein the hypervariable
region is the Complementarity Determining Region (CDR) H3 of a
heavy chain variable domain.
2-3. (canceled)
4. The antibody variant of claim 1 wherein about one to about 30
amino acid residues have been inserted in the hypervariable region
of the parent antibody.
5. The antibody variant of claim 4 wherein about two to about ten
amino acid residues have been inserted in the hypervariable region
of the parent antibody.
6. The antibody variant of claim 1 which has a binding affinity for
said antigen that is at least about five fold stronger than the
binding affinity of the parent antibody for said antigen.
7. The antibody variant of claim 1 wherein the antibody variant has
a potency in a biological activity assay which is at least about 20
fold greater than the potency of the parent antibody in the
biological activity assay.
8. The antibody variant of claim 7 wherein the potency of the
antibody variant in the biological activity assay is at least about
50 fold greater than the potency of the parent antibody in the
biological activity assay.
9. The antibody variant of claim 1 wherein the parent antibody is a
humanized antibody.
10. The antibody variant of claim 1 wherein the parent antibody is
a human antibody.
11. The antibody variant of claim 1 wherein at least one of the
inserted residues has a net positive charge or a net negative
charge.
12. The antibody variant of claim 11 wherein at least one of the
inserted residues is arginine or lysine.
13. The antibody variant of claim 1 wherein the insertion is
adjacent to residue number 100 of the heavy chain variable domain
of the parent antibody, utilizing the variable domain residue
numbering as in Kabat.
14. The antibody variant of claim 13 wherein the insertion consists
of about three inserted amino acid residues.
15-17. (canceled)
18. A composition comprising the antibody variant of claim 1 and a
pharmaceutically acceptable carrier.
19-28. (canceled)
29. A process of producing an antibody variant comprising culturing
a host cell that expresses the antibody variant of claim 1.
30. The process of claim 29 further comprising recovering the
antibody variant from the host cell culture.
31. The process of claim 30 wherein the antibody variant is
recovered from the host cell culture medium.
Description
[0001] This is a continuation application claiming priority to U.S.
application Ser. No. 10/624,153, filed Jul. 21, 2003, which is a
continuation application of U.S. application Ser. No. 09/440,781,
issued Oct. 14, 2003 as U.S. Pat. No. 6,632,926, which is a
non-provisional application filed under 37 CFR 1.53(b) claiming
priority to provisional application 60/108,945 filed Nov. 18, 1998,
the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to antibody variants. In
particular, antibody variants of parent antibodies are disclosed
which have one or more amino acids inserted in a hypervariable
region of the parent antibody and a binding affinity for a target
antigen which is at least about two fold stronger than the binding
affinity of the parent antibody for the antigen.
[0004] 2. Description of Related Art
[0005] Antibodies are proteins, which exhibit binding specificity
to a specific antigen. Native antibodies are usually
heterotetrameric glycoproteins of about 150,000 daltons, composed
of two identical light (L) chains and two identical heavy (H)
chains. Each light chain is linked to a heavy chain by one covalent
disulfide bond, while the number of disulfide linkages varies
between the heavy chains of different immunoglobulin isotypes. Each
heavy and light chain also has regularly spaced intrachain
disulfide bridges. Each heavy chain has at one end a variable
domain (V.sub.H) followed by a number of constant domains. Each
light chain has a variable domain at one end (V.sub.L) and a
constant domain at its other end; the constant domain of the light
chain is aligned with the first constant domain of the heavy chain,
and the light chain variable domain is aligned with the variable
domain of the heavy chain. Particular amino acid residues are
believed to form an interface between the light and heavy chain
variable domains.
[0006] The term "variable" refers to the fact that certain portions
of the variable domains differ extensively in sequence among
antibodies and are responsible for the binding specificity of each
particular antibody for its particular antigen. However, the
variability is not evenly distributed through the variable domains
of antibodies. It is concentrated in three segments called
Complementarity Determining Regions (CDRs) both in the light chain
and the heavy chain variable domains. The more highly conserved
portions of the variable domains are called the framework regions
(FR). The variable domains of native heavy and light chains each
comprise four FR regions, largely adopting a .beta.-sheet
configuration, connected by three CDRs, which form loops
connecting, and in some cases forming part of, the .beta.-sheet
structure. The CDRs in each chain are held together in close
proximity by the FR regions and, with the CDRs from the other
chain, contribute to the formation of the antigen binding site of
antibodies (see Kabat et al., Sequences of Proteins of
Immunological Interest, 5th Ed. Public Health Service, National
Institutes of Health, Bethesda, Md. (1991)).
[0007] The constant domains are not involved directly in binding an
antibody to an antigen, but exhibit various effector functions.
Depending on the amino acid sequence of the constant region of
their heavy chains, antibodies or immunoglobulins can be assigned
to different classes. There are five major classes of
immunoglobulins:
[0008] IgA, IgD, IgE, IgG and IgM, and several of these may be
further divided into subclasses (isotypes), e.g. IgG1, IgG2, IgG3,
and IgG4; IgA1 and IgA2. The heavy chain constant regions that
correspond to the different classes of immunoglobulins are called
.alpha., .delta., .epsilon., .gamma., and .mu., respectively. Of
the various human immunoglobulin classes, only human IgG1, IgG2,
IgG3 and IgM are known to activate complement.
[0009] In vivo, affinity maturation of antibodies is driven by
antigen selection of higher affinity antibody variants which are
made primarily by somatic hypermutagenesis. A "repertoire shift"
also often occurs in which the predominant germline genes of the
secondary or tertiary response are seen to differ from those of the
primary or secondary response.
[0010] Various research groups have attempted to mimic the affinity
maturation process of the immune system, by introducing mutations
into antibody genes in vitro and using affinity selection to
isolate mutants with improved affinity. Such mutant antibodies can
be displayed on the surface of filamentous bacteriophage and
antibodies can be selected by their affinity for antigen or by
their kinetics of dissociation (off-rate) from antigen. Hawkins et
al. J. Mol. Biol. 226:889-896 (1992). CDR walking mutagenesis has
been employed to affinity mature human antibodies which bind the
human envelope glycoprotein gp120 of human immunodeficiency virus
type 1 (HIV-1) (Barbas I I I et al. PNAS (USA) 91: 3809-3813
(1994); and Yang et al. J. Mol. Biol. 254:392-403 (1995)); and an
anti-c-erbB-2 single chain Fv fragment (Schier et al. J. Mol. Biol.
263:551567 (1996)). Antibody chain shuffling and CDR mutagenesis
were used to affinity mature a high-affinity human antibody
directed against the third hypervariable loop of HIV (Thompson et
al. J. Mol. Biol. 256:77-88 (1996)). Balint and Larrick Gene
137:109-118 (1993) describe a technique they coin "parsimonious
mutagenesis" which involves computer-assisted
oligodeoxyribonucleotide-directed scanning mutagenesis whereby all
three CDRs of a variable region gene are simultaneously and
thoroughly searched for improved variants. Wu et al. affinity
matured an .alpha.v.beta.3-specific humanized antibody using an
initial limited mutagenesis strategy in which every position of all
six CDRs was mutated followed by the expression and screening of a
combinatorial library including the highest affinity mutants (Wu et
al. PNAS (USA) 95: 6037-6-42 (1998)). Phage antibodies are reviewed
in Chiswell and McCafferty TIBTECH 10:80-84 (1992); and Rader and
Barbas I I I Current Opinion in Biotech. 8:503-508 (1997). In each
case where mutant antibodies with improved affinity compared to a
parent antibody are reported in the above references, the mutant
antibody has amino acid substitutions in a CDR.
SUMMARY OF THE INVENTION
[0011] Unlike the affinity matured antibodies of the above
references, the present invention provides an antibody variant of a
parent antibody, which antibody variant comprises an amino acid
insertion in or adjacent to a hypervariable region of the parent
antibody and has a binding affinity for a target antigen which is
at least about two fold stronger than the binding affinity of the
parent antibody for the antigen.
[0012] The invention further provides an antibody variant
comprising a heavy chain variable domain, wherein CDR H3 of the
heavy chain variable domain comprises the amino acid sequence of
CDR H3 of a variant selected from the group consisting of Y0239-19
(SEQ ID NO:85); Y0239-8 (SEQ ID NO:53); Y0240-1 (SEQ ID NO:86);
Y0239-12 (SEQ ID NO:78); Y0239-9 (SEQ ID NO:54); and Y0261-6 (SEQ
ID NO:89). These CDR H3 sequences may, for example, be provided in
the heavy chain variable domain sequence of SEQ ID NO: 98 or 99;
see FIG. 1B). Preferably, the antibody variant further comprises a
light chain variable domain and binds VEGF antigen with stronger
binding affinity than Y0192 (see FIGS. 1A and 1B; SEQ ID NO's 95
and 96).
[0013] The invention further provides a method for producing an
antibody variant comprising introducing an amino acid residue in or
adjacent to a hypervariable region of a parent antibody, wherein
the antibody variant has a binding affinity for a target antigen
which is at least about two fold stronger than the binding affinity
of the parent antibody for said antigen.
[0014] Additionally, the invention provides a method for making an
antibody variant, comprising the steps of:
[0015] (a) identifying potential amino acid interactions between a
hypervariable region of a parent antibody and a target antigen;
[0016] (b) preparing a variant of the parent antibody comprising
introducing an amino acid residue in or adjacent to the
hypervariable region of the parent antibody, wherein the introduced
amino acid residue contributes to the potential amino acid
interactions in (a); and
[0017] (c) selecting an antibody variant prepared as in (b) which
has a stronger binding affinity for the antigen than the parent
antibody.
[0018] Various forms of the antibody variant are contemplated
herein. For example, the antibody variant may be a full length
antibody (e.g. having a human immunoglobulin constant region) or an
antibody fragment (e.g. a F(ab').sub.2). Furthermore, the antibody
variant may be labeled with a detectable label, immobilized on a
solid phase and/or conjugated with a heterologous compound (such as
a cytotoxic agent).
[0019] Diagnostic and therapeutic uses for the antibody variant are
contemplated. In one diagnostic application, the invention provides
a method for determining the presence of an antigen of interest
comprising exposing a sample suspected of containing the antigen to
the antibody variant and determining binding of the antibody
variant to the sample. For this use, the invention provides a kit
comprising the antibody variant and instructions for using the
antibody variant to detect the antigen.
[0020] The invention further provides: isolated nucleic acid
encoding the antibody variant; a vector comprising the nucleic
acid, optionally, operably linked to control sequences recognized
by a host cell transformed with the vector; a host cell transformed
with the vector; a process for producing the antibody variant
comprising culturing this host cell so that the nucleic acid is
expressed and, optionally, recovering the antibody variant from the
host cell culture (e.g. from the host cell culture medium).
[0021] The invention also provides a composition comprising the
antibody variant and a pharmaceutically acceptable carrier or
diluent. This composition for therapeutic use is sterile and may be
lyophilized.
[0022] The invention further provides a method for treating a
mammal comprising administering an effective amount of the antibody
variant to the mammal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIGS. 1A and 1B show a sequence alignment of the light chain
variable region (FIG. 1A) and heavy chain variable region (FIG. 1B)
of several variants of the humanized anti-VEGF antibody F(ab)-12.
The parental Fab-phage clone Y0192 contains light chain mutations
which do not significantly affect antigen binding affinity, and has
been described (WO98/45331). Another variant, Y0238-3, contains
mutations in CDR H1 which improve antigen-binding (WO98/45331).
Variant Y0239-19 contains the "VNERK" motif identified in
selections from CDR H3 insertion libraries described herein.
Variant Y0313-2 contains the CDR H1 mutations of Y0238-3 combined
with the CDR H3 mutations of Y0239-19. Differences from F(ab)-12
are highlighted with shaded boxes. The sequence identifiers in
FIGS. 1A and 1B are as follows: F(ab)-12 light chain variable
domain (SEQ ID NO:94); Y0192, Y0238-3, Y0239-19 and Y0313-2 light
chain variable domain (SEQ ID NO:95); F(ab)-12 and Y0192 heavy
chain variable domain (SEQ ID NO:96); Y0238-3 heavy chain variable
domain (SEQ ID NO:97); Y0239-19 heavy chain variable domain (SEQ ID
NO:98); and Y0313-2 heavy chain variable domain (SEQ ID NO:99).
[0024] FIG. 2 shows the inhibition of VEGF activity in a cell-based
bioassay by Fab, F(ab)-12 and Fab variant Y0313-2.
[0025] FIG. 3 shows a portion of the three-dimensional model of
F(ab)-12 in complex with VEGF as determined by x-ray
crystallography (Muller et al. Structure 6(9): 1153-1167 (1998)).
The main chain trace of the CDR H3 region of the antibody is
depicted as a magenta ribbon at right. A surface rendering of a
portion of VEGF is depicted at left, with several proximal residues
highlighted in red (acidic) or purple (basic). The side chain of
D41 of VEGF can be seen as a site of potential interaction with a
hypothetical insertion peptide placed into the CDR H3.
[0026] FIG. 4 shows a superposition of portions of the
three-dimensional model of F(ab)-12 in complex with VEGF (both
molecules in gray; Muller et al., supra) with a model of the
insertion variant Fab Y0313-2 (green) in complex with VEGF
(yellow). The latter model is based on x-ray crystallographic
determination of the variant complex structure described herein.
The figure illustrates that little structural change is observed in
the complex as compared with the F(ab)-12 complex, except in the
immediate vicinity of the mutations V104, N104a, E104b, R104c, and
K105.
[0027] FIG. 5 shows a comparison of portions of the
three-dimensional model of F(ab)-12 in complex with VEGF (at right;
Muller et al., supra) with a model of Fab Y0313-2 in complex with
VEGF (at left) as described herein. In each case, VEGF is shown in
yellow, and the respective Fab is shown in green. In the Y0313-2
complex, it can be seen that V104 and R104c make new contacts with
VEGF.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. Definitions
[0028] The term "antibody" is used in the broadest sense and
specifically covers monoclonal antibodies (including full length
monoclonal antibodies), polyclonal antibodies, multispecific
antibodies (e.g., bispecific antibodies), and antibody fragments so
long as they exhibit the desired biological activity.
[0029] The term "hypervariable region" when used herein refers to
the regions of an antibody variable domain which are hypervariable
in sequence and/or form structurally defined loops. The
hypervariable region comprises amino acid residues from a
"complementarity determining region" or "CDR" (i.e. residues 24-34
("CDR L1"), 50-56 ("CDR L2") and 89-97 ("CDR L3") in the light
chain variable domain and 31-35 ("CDR H1"), 50-65 ("CDR H2") and
95-102 ("CDR H3") in the heavy chain variable domain; Kabat et al.,
Sequences of Proteins of Immunological Interest, 5th Ed. Public
Health Service, National Institutes of Health, Bethesda, Md.
(1991)) and/or those residues from a "hypervariable loop" (i.e.
residues 26-32 ("loop L1"), 50-52 ("loop L2") and 91-96 ("loop L3")
in the light chain variable domain and 26-32 ("loop H1"), 53-55
("loop H2") and 96-101 ("loop H3") in the heavy chain variable
domain; Chothia and Lesk J. Mol. Biol. 196:901-917 (1987)). In both
cases, the variable domain residues are numbered according to Kabat
et al., supra. "Framework" or "FR" residues are those variable
domain residues other than the hypervariable region residues as
herein defined.
[0030] The expression "variable domain residue numbering as in
Kabat" refers to the numbering system used for heavy chain variable
domains or light chain variable domains of the compilation of
antibodies in Kabat et al., Sequences of Proteins of Immunological
Interest, 5th Ed. Public Health Service, National Institutes of
Health, Bethesda, Md. (1991). Using this numbering system, the
actual linear amino acid sequence may contain fewer or additional
amino acids corresponding to a shortening of, or insertion into, a
FR or CDR of the variable domain. For example, a heavy chain
variable domain may include a single amino acid insert (residue 52a
according to Kabat) after residue 52 of CDR H2 and inserted
residues (e.g. residues 82a, 82b, and 82c, etc according to Kabat)
after heavy chain FR residue 82. The Kabat numbering of residues
may be determined for a given antibody by alignment at regions of
homology of the sequence of the antibody with a "standard" Kabat
numbered sequence.
[0031] "Antibody fragments" comprise a portion of a full length
antibody, generally the antigen binding or variable region thereof.
Examples of antibody fragments include Fab, Fab', F(ab').sub.2, and
Fv fragments; diabodies; linear antibodies; single-chain antibody
molecules; and multispecific antibodies formed from antibody
fragments.
[0032] The term "monoclonal antibody" as used herein refers to an
antibody obtained from a population of substantially homogeneous
antibodies, i.e., the individual antibodies comprising the
population are identical except for possible naturally occurring
mutations that may be present in minor amounts. Monoclonal
antibodies are highly specific, being directed against a single
antigenic site. Furthermore, in contrast to conventional
(polyclonal) antibody preparations which typically include
different antibodies directed against different determinants
(epitopes), each monoclonal antibody is directed against a single
determinant on the antigen. The modifier "monoclonal" indicates the
character of the antibody as being obtained from a substantially
homogeneous population of antibodies, and is not to be construed as
requiring production of the antibody by any particular method. For
example, the monoclonal antibodies to be used in accordance with
the present invention may be made by the hybridoma method first
described by Kohler et al., Nature 256:495 (1975), or may be made
by recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567).
The "monoclonal antibodies" may also be isolated from phage
antibody libraries using the techniques described in Clackson et
al., Nature 352:624-628 (1991) and Marks et al., J. Mol. Biol.
222:581-597 (1991), for example.
[0033] The monoclonal antibodies herein specifically include
"chimeric" antibodies (immunoglobulins) in which a portion of the
heavy and/or light chain is identical with or homologous to
corresponding sequences in antibodies derived from a particular
species or belonging to a particular antibody class or subclass,
while the remainder of the chain(s) is identical with or homologous
to corresponding sequences in antibodies derived from another
species or belonging to another antibody class or subclass, as well
as fragments of such antibodies, so long as they exhibit the
desired biological activity (U.S. Pat. No. 4,816,567; and Morrison
et al., Proc. Natl. Acad. Sci. USA 81:6851-6855 (1984)).
[0034] "Humanized" forms of non-human (e.g., murine) antibodies are
chimeric antibodies which contain minimal sequence derived from
non-human immunoglobulin. For the most part, humanized antibodies
are human immunoglobulins (recipient antibody) in which residues
from a hypervariable region of the recipient are replaced by
residues from a hypervariable region of a non-human species (donor
antibody) such as mouse, rat, rabbit or nonhuman primate having the
desired specificity, affinity, and capacity. In some instances, Fv
framework region (FR) residues of the human immunoglobulin are
replaced by corresponding non-human residues. Furthermore,
humanized antibodies may comprise residues which are not found in
the recipient antibody or in the donor antibody. These
modifications are made to further refine antibody performance. In
general, the humanized antibody will comprise substantially all of
at least one, and typically two, variable domains, in which all or
substantially all of the hypervariable loops correspond to those of
a non-human immunoglobulin and all or substantially all of the FR
regions are those of a human immunoglobulin sequence. The humanized
antibody optionally also will comprise at least a portion of an
immunoglobulin constant region (Fc), typically that of a human
immunoglobulin. For further details, see Jones et al., Nature
321:522-525 (1986); Riechmann et al., Nature 332:323-329 (1988);
and Presta, Curr. Op. Struct. Biol. 2:593-596 (1992).
[0035] "Single-chain Fv" or "sFv" antibody fragments comprise the
V.sub.H and V.sub.L domains of antibody, wherein these domains are
present in a single polypeptide chain. Generally, the Fv
polypeptide further comprises a polypeptide linker between the
V.sub.H and V.sub.L domains which enables the sFv to form the
desired structure for antigen binding. For a review of sFv see
Pluckthun in The Pharmacology of Monoclonal Antibodies, vol. 113,
Rosenburg and Moore eds. Springer-Verlag, New York, pp. 269-315
(1994).
[0036] The term "diabodies" refers to small antibody fragments with
two antigen-binding sites, which fragments comprise a heavy chain
variable domain (V.sub.H) connected to a light chain variable
domain (V.sub.L) in the same polypeptide chain (V.sub.H-V.sub.L).
By using a linker that is too short to allow pairing between the
two domains on the same chain, the domains are forced to pair with
the complementary domains of another chain and create two
antigen-binding sites. Diabodies are described more fully in, for
example, EP 404,097; WO 93/11161; and Hollinger et al., Proc. Natl.
Acad. Sci. USA 90:6444-6448 (1993).
[0037] The expression "linear antibodies" when used throughout this
application refers to the antibodies described in Zapata et al.
Protein Eng. 8(10):1057-1062 (1995). Briefly, these antibodies
comprise a pair of tandem Fd segments
(V.sub.H-C.sub.H1-V.sub.H-C.sub.H1) which form a pair of antigen
binding regions. Linear antibodies can be bispecific or
monospecific.
[0038] A "parent antibody" is an antibody comprising an amino acid
sequence which lacks, or is deficient in, one or more amino acid
residues in or adjacent to one or more hypervariable regions
thereof compared to an antibody variant as herein disclosed. Thus,
the parent antibody has a shorter hypervariable region than the
corresponding hypervariable region of an antibody variant as herein
disclosed. The parent polypeptide may comprise a native sequence
(i.e. a naturally occurring) antibody (including a
naturally-occurring allelic variant) or an antibody with
pre-existing amino acid sequence modifications (such as other
insertions, deletions and/or substitutions) of a
naturally-occurring sequence. Preferably the parent antibody is a
humanized antibody or a human antibody.
[0039] As used herein, "antibody variant" refers to an antibody
which has an amino acid sequence which differs from the amino acid
sequence of a parent antibody. Preferably, the antibody variant
comprises a heavy chain variable domain or a light chain variable
domain having an amino acid sequence which is not found in nature.
Such variants necessarily have less than 100% sequence identity or
similarity with the parent antibody. In a preferred embodiment, the
antibody variant will have an amino acid sequence from about 75% to
less than 100% amino acid sequence identity or similarity with the
amino acid sequence of either the heavy or light chain variable
domain of the parent antibody, more preferably from about 80% to
less than 100%, more preferably from about 85% to less than 100%,
more preferably from about 90% to less than 100%, and most
preferably from about 95% to less than 100%. Identity or similarity
with respect to this sequence is defined herein as the percentage
of amino acid residues in the candidate sequence that are identical
(i.e. same residue) with the parent antibody residues, after
aligning the sequences and introducing gaps, if necessary, to
achieve the maximum percent sequence identity. None of N-terminal,
C-terminal, or internal extensions, deletions, or insertions into
the antibody sequence outside of the variable domain shall be
construed as affecting sequence identity or similarity. The
antibody variant is generally one which has a longer hypervariable
region (by one or more amino acid residues; e.g. by about one to
about 30 amino acid residues and preferably by about two to about
ten amino acid residues) than the corresponding hypervariable
region of a parent antibody.
[0040] An "amino acid alteration" refers to a change in the amino
acid sequence of a predetermined amino acid sequence. Exemplary
alterations include insertions, substitutions and deletions.
[0041] An "amino acid insertion" refers to the introduction of one
or more amino acid residues into a predetermined amino acid
sequence
[0042] The amino acid insertion may comprise a "peptide insertion"
in which case a peptide comprising two or more amino acid residues
joined by peptide bond(s) is introduced into the predetermined
amino acid sequence. Where the amino acid insertion involves
insertion of a peptide, the inserted peptide may be generated by
random mutagenesis such that it has an amino acid sequence which
does not exist in nature.
[0043] The inserted residue or residues may be "naturally occurring
amino acid residues" (i.e. encoded by the genetic code) and
selected from the group consisting of: alanine (Ala); arginine
(Arg); asparagine (Asn); aspartic acid (Asp); cysteine (Cys);
glutamine (Gln); glutamic acid (Glu); glycine (Gly); histidine (H
is); isoleucine (Ile): leucine (Leu); lysine (Lys); methionine
(Met); phenylalanine (Phe); proline (Pro); serine (Ser); threonine
(Thr); tryptophan (Trp); tyrosine (Tyr); and valine (Val).
[0044] Insertion of one or more non-naturally occurring amino acid
residues is also encompassed by the definition of an amino acid
insertion herein. A "non-naturally occurring amino acid residue"
refers to a residue, other than those naturally occurring amino
acid residues listed above, which is able to covalently bind
adjacent amino acid residues(s) in a polypeptide chain. Examples of
non-naturally occurring amino acid residues include norleucine,
ornithine, norvaline, homoserine and other amino acid residue
analogues such as those described in Ellman et al. Meth. Enzym.
202:301-336 (1991). To generate such non-naturally occurring amino
acid residues, the procedures of Noren et al. Science 244:182
(1989) and Ellman et al., supra, can be used. Briefly, these
procedures involve chemically activating a suppressor tRNA with a
non-naturally occurring amino acid residue followed by in vitro
transcription and translation of the RNA.
[0045] An amino acid insertion "in a hypervariable region" refers
to the introduction of one or more amino acid residues within a
hypervariable region amino acid sequence.
[0046] An amino acid insertion "adjacent a hypervariable region"
refers to the introduction of one or more amino acid residues at
the N-terminal and/or C-terminal end of a hypervariable region,
such that at least one of the inserted amino acid residues forms a
peptide bond with the N-terminal or C-terminal amino acid residue
of the hypervariable region in question.
[0047] An "amino acid substitution" refers to the replacement of an
existing amino acid residue in a predetermined amino acid sequence
with another different amino acid residue.
[0048] The term "potential amino acid interactions" refers to
contacts or energetically favorable interactions between one or
more amino acid residues present in an antigen and one or more
amino acid residues which do not exist in a parent antibody but can
be introduced therein so as to increase the amino acid contacts
between the antigen and an antibody variant comprising those
introduced amino acid residue(s). Preferably the amino acid
interactions of interest are selected from the group consisting of
hydrogen bonding, van der Waals interactions and ionic
interactions
[0049] The term "target antigen" herein refers to a predetermined
antigen to which both a parent antibody and antibody variant as
herein defined bind. The target antigen may be polypeptide,
carbohydrate, nucleic acid, lipid, hapten or other naturally
occurring or synthetic compound. Preferrably, the target antigen is
a polypeptide. While the antibody variant binds the target antigen
with better binding affinity than the parent antibody, the parent
antibody generally has a binding affinity (K.sub.d) value for the
target antigen of no more than about 1.times.10.sup.-5M, and
preferably no more than about 1.times.10.sup.-6M.
[0050] An "isolated" antibody is one which has been identified and
separated and/or recovered from a component of its natural
environment. Contaminant components of its natural environment are
materials which would interfere with diagnostic or therapeutic uses
for the antibody, and may include enzymes, hormones, and other
proteinaceous or nonproteinaceous solutes. In preferred
embodiments, the antibody will be purified (1) to greater than 95%
by weight of antibody as determined by the Lowry method, and most
preferably more than 99% by weight, (2) to a degree sufficient to
obtain at least 15 residues of N-terminal or internal amino acid
sequence by use of a spinning cup sequenator, or (3) to homogeneity
by SDS-PAGE under reducing or nonreducing conditions using
Coomassie blue or, preferably, silver stain. Isolated antibody
includes the antibody in situ within recombinant cells since at
least one component of the antibody's natural environment will not
be present. Ordinarily, however, isolated antibody will be prepared
by at least one purification step.
[0051] "Treatment" refers to both therapeutic treatment and
prophylactic or preventative measures. Those in need of treatment
include those already with the disorder as well as those in which
the disorder is to be prevented.
[0052] A "disorder" is any condition that would benefit from
treatment with the antibody variant. This includes chronic and
acute disorders or diseases including those pathological conditions
which predispose the mammal to the disorder in question.
[0053] "Mammal" for purposes of treatment refers to any animal
classified as a mammal, including humans, domestic and farm
animals, nonhuman primates, and zoo, sports, or pet animals, such
as dogs, horses, cats, cows, etc.
[0054] The term "cytotoxic agent" as used herein refers to a
substance that inhibits or prevents the function of cells and/or
causes destruction of cells. The term is intended to include
radioactive isotopes (e.g., I.sup.131, I.sup.125, Y.sup.90 and
Re.sup.186), chemotherapeutic agents, and toxins such as
enzymatically active toxins of bacterial, fungal, plant or animal
origin, or fragments thereof.
[0055] A "chemotherapeutic agent" is a chemical compound useful in
the treatment of cancer. Examples of chemotherapeutic agents
include Adriamycin, Doxorubicin, 5-Fluorouracil, Cytosine
arabinoside ("Ara-C"), Cyclophosphamide, Thiotepa, Taxotere
(docetaxel), Busulfan, Cytoxin, Taxol, Methotrexate, Cisplatin,
Melphalan, Vinblastine, Bleomycin, Etoposide, Ifosfamide, Mitomycin
C, Mitoxantrone, Vincreistine, Vinorelbine, Carboplatin,
Teniposide, Daunomycin, Caminomycin, Aminopterin, Dactinomycin,
Mitomycins, Esperamicins (see U.S. Pat. No. 4,675,187), Melphalan
and other related nitrogen mustards.
[0056] The term "prodrug" as used in this application refers to a
precursor or derivative form of a pharmaceutically active substance
that is less cytotoxic to tumor cells compared to the parent drug
and is capable of being enzymatically activated or converted into
the more active parent form. See, e.g., Wilman, "Prodrugs in Cancer
Chemotherapy" Biochemical Society Transactions, 14, pp. 375-382,
615th Meeting Belfast (1986) and Stella et al., "Prodrugs: A
Chemical Approach to Targeted Drug Delivery," Directed Drug
Delivery, Borchardt et al., (ed.), pp. 247-267, Humana Press
(1985). The prodrugs of this invention include, but are not limited
to, phosphate-containing prodrugs, thiophosphate-containing
prodrugs, sulfate-containing prodrugs, peptide-containing prodrugs,
D-amino acid-modified prodrugs, glycosylated prodrugs,
beta-lactam-containing prodrugs, optionally substituted
phenoxyacetamide-containing prodrugs or optionally substituted
phenylacetamide-containing prodrugs, 5-fluorocytosine and other
5-fluorouridine prodrugs which can be converted into the more
active cytotoxic free drug. Examples of cytotoxic drugs that can be
derivatized into a prodrug form for use in this invention include,
but are not limited to, those chemotherapeutic agents described
above.
[0057] The word "label" when used herein refers to a detectable
compound or composition which is conjugated directly or indirectly
to the antibody. The label may be itself be detectable (e.g.,
radioisotope labels or fluorescent labels) or, in the case of an
enzymatic label, may catalyze chemical alteration of a substrate
compound or composition which is detectable.
[0058] By "solid phase" is meant a non-aqueous matrix to which the
antibody of the present invention can adhere. Examples of solid
phases encompassed herein include those formed partially or
entirely of glass (e.g. controlled pore glass), polysaccharides
(e.g., agarose), polyacrylamides, polystyrene, polyvinyl alcohol
and silicones. In certain embodiments, depending on the context,
the solid phase can comprise the well of an assay plate; in others
it is a purification column (e.g. an affinity chromatography
column). This term also includes a discontinuous solid phase of
discrete particles, such as those described in U.S. Pat. No.
4,275,149.
[0059] A "liposome" is a small vesicle composed of various types of
lipids, phospholipids and/or surfactant which is useful for
delivery of a drug (such as the antibody variants disclosed herein
and, optionally, a chemotherapeutic agent) to a mammal. The
components of the liposome are commonly arranged in a bilayer
formation, similar to the lipid arrangement of biological
membranes.
[0060] An "isolated" nucleic acid molecule is a nucleic acid
molecule that is identified and separated from at least one
contaminant nucleic acid molecule with which it is ordinarily
associated in the natural source of the antibody nucleic acid. An
isolated nucleic acid molecule is other than in the form or setting
in which it is found in nature. Isolated nucleic acid molecules
therefore are distinguished from the nucleic acid molecule as it
exists in natural cells. However, an isolated nucleic acid molecule
includes a nucleic acid molecule contained in cells that ordinarily
express the antibody where, for example, the nucleic acid molecule
is in a chromosomal location different from that of natural
cells.
[0061] The expression "control sequences" refers to DNA sequences
necessary for the expression of an operably linked coding sequence
in a particular host organism. The control sequences that are
suitable for prokaryotes, for example, include a promoter,
optionally an operator sequence, and a ribosome binding site.
Eukaryotic cells are known to utilize promoters, polyadenylation
signals, and enhancers.
[0062] Nucleic acid is "operably linked" when it is placed into a
functional relationship with another nucleic acid sequence. For
example, DNA for a presequence or secretory leader is operably
linked to DNA for a polypeptide if it is expressed as a preprotein
that participates in the secretion of the polypeptide; a promoter
or enhancer is operably linked to a coding sequence if it affects
the transcription of the sequence; or a ribosome binding site is
operably linked to a coding sequence if it is positioned so as to
facilitate translation. Generally, "operably linked" means that the
DNA sequences being linked are contiguous, and, in the case of a
secretory leader, contiguous and in reading phase. However,
enhancers do not have to be contiguous. Linking is accomplished by
ligation at convenient restriction sites. If such sites do not
exist, the synthetic oligonucleotide adaptors or linkers are used
in accordance with conventional practice.
[0063] As used herein, the expressions "cell," "cell line," and
"cell culture" are used interchangeably and all such designations
include progeny. Thus, the words "transformants" and "transformed
cells" include the primary subject cell and cultures derived
therefrom without regard for the number of transfers. It is also
understood that all progeny may not be precisely identical in DNA
content, due to deliberate or inadvertent mutations. Mutant progeny
that have the same function or biological activity as screened for
in the originally transformed cell are included. Where distinct
designations are intended, it will be clear from the context.
II. Modes for Carrying out the Invention
[0064] The invention herein relates to a method for making an
antibody variant. The parent antibody or starting antibody is
prepared using techniques available in the art for generating such
antibodies. Exemplary methods for generating antibodies are
described in more detail in the following sections.
[0065] The parent antibody is directed against a target antigen of
interest. Preferably, the target antigen is a biologically
important polypeptide and administration of the antibody to a
mammal suffering from a disease or disorder can result in a
therapeutic benefit in that mammal. However, antibodies directed
against nonpolypeptide antigens (such as tumor-associated
glycolipid antigens; see U.S. Pat. No. 5,091,178) are also
contemplated.
[0066] Where the antigen is a polypeptide, it may be a
transmembrane molecule (e.g. receptor) or ligand such as a growth
factor. Exemplary antigens include molecules such as renin; a
growth hormone, including human growth hormone and bovine growth
hormone; growth hormone releasing factor; parathyroid hormone;
thyroid stimulating hormone; lipoproteins; alpha-1-antitrypsin;
insulin A-chain; insulin B-chain; proinsulin; follicle stimulating
hormone; calcitonin; luteinizing hormone; glucagon; clotting
factors such as factor VIIIC, factor IX, tissue factor, and von
Willebrands factor; anti-clotting factors such as Protein C; atrial
natriuretic factor; lung surfactant; a plasminogen activator, such
as urokinase or human urine or tissue-type plasminogen activator
(t-PA); bombesin; thrombin; hemopoietic growth factor; tumor
necrosis factor-alpha and -beta; enkephalinase; RANTES (regulated
on activation normally T-cell expressed and secreted); human
macrophage inflammatory protein (MIP-1-alpha); a serum albumin such
as human serum albumin; Muellerian-inhibiting substance; relaxin
A-chain; relaxin B-chain; prorelaxin; mouse gonadotropin-associated
peptide; a microbial protein, such as beta-lactamase; DNase; IgE; a
cytotoxic T-lymphocyte associated antigen (CTLA), such as CTLA-4;
inhibin; activin; vascular endothelial growth factor (VEGF);
receptors for hormones or growth factors; protein A or D;
rheumatoid factors; a neurotrophic factor such as bone-derived
neurotrophic factor (BDNF), neurotrophin-3, -4, -5, or -6 (NT-3,
NT-4, NT-5, or NT-6), or a nerve growth factor; platelet-derived
growth factor (PDGF); fibroblast growth factor such as aFGF and
bFGF; epidermal growth factor (EGF); transforming growth factor
(TGF) such as TGF-alpha and TGF-beta; insulin-like growth factor-I
and -II (IGF-I and IGF-II); des(1-3)-IGF-I (brain IGF-I),
insulin-like growth factor binding proteins; CD proteins such as
CD3, CD4, CD8, CD19 and CD20; erythropoietin; osteoinductive
factors; immunotoxins; a bone morphogenetic protein (BMP); an
interferon such as interferon-alpha, -beta, and -gamma; colony
stimulating factors (CSFs), e.g., M-CSF, GM-CSF, and G-CSF;
interleukins (ILs), e.g., IL-1 to IL-10; superoxide dismutase;
T-cell receptors; surface membrane proteins; decay accelerating
factor; viral antigen such as, for example, a portion of the AIDS
envelope; transport proteins; homing receptors; addressins;
regulatory proteins; integrins such as CD11a, CD11b, CD11c, CD18,
an ICAM, VLA-4 and VCAM; a tumor associated antigen such as HER2,
HER3 or HER4 receptor; and fragments of any of the above-listed
polypeptides.
[0067] Preferred molecular targets for antibodies encompassed by
the present invention include CD proteins such as CD3, CD4, CD8,
CD19, CD20 and CD34; members of the ErbB receptor family such as
the EGF receptor, HER2, HER3 or HER4 receptor; cell adhesion
molecules such as LFA-1, Mac1, p150, 95, VLA-4, ICAM-1, VCAM and
.alpha.v/.beta.3 integrin including either alpha or beta subunits
thereof (e.g. anti-CD11a, anti-CD18 or anti-CD11b antibodies);
growth factors such as VEGF; IgE; blood group antigens; flk2/flt3
receptor; obesity (OB) receptor; mpl receptor; CTLA-4; protein C
etc.
[0068] The antigen used to generate an antibody may be isolated
from a natural source thereof, or may be produced recombinantly or
made using other synthetic methods. Alternatively, cells comprising
native or recombinant antigen can be used as immunogens for making
antibodies.
[0069] The parent antibody may have pre-existing strong binding
affinity for the target antigen. For example, the parent antibody
may bind the antigen of interest with a binding affinity (K.sub.d)
value of no more than about 1.times.10.sup.-7 M, preferably no more
than about 1.times.10.sup.-8 M and most preferably no more than
about 1.times.10.sup.-9 M.
[0070] Antibody "binding affinity" may be determined by equilibrium
methods (e.g. enzyme-linked immunoabsorbent assay (ELISA) or
radioimmunoassay (RIA)), or kinetics (e.g. BIACORE.TM. analysis;
see Example 1 below), for example.
[0071] Also, the antibody may be subjected to other "biological
activity assays", e.g., in order to evaluate its "potency" or
pharmacological activity and potential efficacy as a therapeutic
agent. Such assays are known in the art and depend on the target
antigen and intended use for the antibody. Examples include the
keratinocyte monolayer adhesion assay and the mixed lymphocyte
response (MLR) assay for CD11a (see WO98/23761); tumor cell growth
inhibition assays (as described in WO 89/06692, for example);
antibody-dependent cellular cytotoxicity (ADCC) and
complement-mediated cytotoxicity (CDC) assays (U.S. Pat. No.
5,500,362); agonistic activity or hematopoiesis assays (see WO
95/27062); tritiated thymidine incorporation assay; and alamar blue
assay to measure metabolic activity of cells in response to a
molecule such as VEGF (See Example 1 below).
[0072] The amino acid sequence of the parent antibody is altered so
as to generate an antibody variant which has a stronger binding
affinity for the target antigen than the parent antibody. The
antibody variant preferably has a binding affinity for the target
antigen which is at least about two fold stronger (e.g. from about
two fold to about 1000 fold or even to about 10,000 fold improved
binding affinity), preferably at least about five fold stronger,
and preferably at least about ten fold or 100 fold stronger, than
the binding affinity of the parent antibody for the antigen. The
enhancement in binding affinity desired or required may depend on
the initial binding affinity of the parent antibody.
[0073] Where the assay used is a biological activity assay, the
antibody variant preferably has a potency in the biological
activity assay of choice which is at least about two fold greater
(e.g. from about two fold to about 1000 fold or even to about
10,000 fold improved potency), preferably at least about 20 fold
greater, more preferably at least about 50 fold greater, and
sometimes at least about 100 fold or 200 fold greater, than the
biological activity of the parent antibody in that assay.
[0074] To generate the antibody variant, one or more amino acid
residues are introduced or inserted in or adjacent to one or more
of the hypervariable regions of the parent antibody. Generally, one
will insert one or more amino acid residues in a CDR of the parent
antibody. The number of residues to be inserted may be from about
one residue to about 30 amino acid residues, e.g. from about two to
about ten amino acid residues. In deciding the number of residues
to be inserted, one may take into account the range of lengths of
the hypervariable region in question in known antibodies. For
example, for the first hypervariable region of a light chain
variable domain, the hypervariable region is preferably "CDR L1"
according to Kabat et al., supra, e.g. having an overall length
from about nine amino acid residues to about 20 residues, including
the inserted amino acid residue(s). With respect to the second
hypervariable region of a light chain variable domain, the
hypervariable region is preferably "CDR L2" according to Kabat et
al., supra, e.g. having an overall length from about five amino
acid residues to about ten residues, including the inserted amino
acid residue(s). In relation to the third hypervariable region of a
light chain variable domain, the hypervariable region is preferably
"CDR L3" according to Kabat et al., supra, e.g. having an overall
length from about seven amino acid residues to about 20 residues,
including the inserted amino acid residue(s).
[0075] Preferably, the antibody variant has one or more amino acid
residues inserted in a hypervariable region of the heavy chain
variable region, most preferably CDR H3. If this hypervariable
region is chosen, preferably the inserted amino acid residues are
between residue numbers 97 and 102 (e.g., adjacent to, and
preferably C-terminal in sequence to, residue number 100) of the
heavy chain variable domain of the parent antibody, utilizing the
variable domain residue numbering as in Kabat.
[0076] In deciding upon the number of amino acid residues to
insert, one may take into account the desired length of the altered
hypervariable region. For example, for the first hypervariable
region of a heavy chain variable domain, the hypervariable region
is preferably the stretch of residues from the "loop H1" of Chothia
et al, supra, combined with the stretch of residues considered to
constitute "CDR H1" according to Kabat et al., supra. Thus, this
first hypervariable loop of the heavy chain variable domain may
have an overall length from about eight amino acid residues to
about 20 residues including the inserted amino acid residue(s). In
relation to the second hypervariable region of a heavy chain
variable domain, the hypervariable region is preferably "CDR H2"
according to Kabat et al., supra, e.g. having an overall length
from about 14 amino acid residues to about 25 residues, including
the inserted amino acid residue(s). Finally, in relation to the
third hypervariable region of a heavy chain variable domain, the
hypervariable region is preferably "CDR H3" according to Kabat et
al., supra, e.g. having an overall length from about six amino acid
residues to about 30 residues, including the inserted amino acid
residue(s).
[0077] Antibody variants with inserted amino acid residue(s) in a
hypervariable region thereof may be prepared randomly, especially
where the starting binding affinity of the parent antibody for the
target antigen is such that randomly produced antibody variants can
be readily screened. For example, phage display provides a
convenient method of screening such random variants.
[0078] The invention also provides a more systematic method for
making antibody variants. This method involves the following
general steps, usually performed sequentially:
[0079] (a) identifying potential amino acid interactions between a
hypervariable region of a parent antibody and a target antigen;
[0080] (b) preparing a variant of the parent antibody by
introducing an amino acid residue in or adjacent to the
hypervariable region of the parent antibody, wherein the introduced
amino acid residue contributes to the potential amino acid
interactions in (a); and
[0081] (c) selecting an antibody variant prepared as in (b) which
has a stronger binding affinity for the antigen than the parent
antibody.
[0082] According to step (a) of this method, one may analyze a
molecular model of the parent antibody complexed with antigen. The
molecular model may be obtained from an X-ray crystal or nuclear
magnetic resonance (NMR) structure of this complex. See, e.g., Amit
et al. Science 233:747-753 (1986); and Muller et al. Structure
6(9): 1153-1167 (1998)). Alternatively, computer programs can be
used to create molecular models of antibody/antigen complexes (see,
e.g., Levy et al. Biochemistry 28:7168-7175 (1989); Bruccoleri et
al. Nature 335: 564-568 (1998); and Chothia et al. Science 233:
755-758 (1986)), where a crystal structure is not available.
[0083] In the preferred method, one analyzes the molecular model of
the antigen/antibody complex and identifies potential areas for
increasing energetically favorable interactions between the antigen
and a hypervariable region of the antibody. For example, one may
identify potential polar interactions (e.g. ion pairs and/or
hydrogen-bonding); non-polar interactions (such as Van der Waals
attractions and/or hydrophobic interactions); and/or covalent
interactions (e.g. disulfide bond(s)) between one or more amino
acid residues of the antigen and one or more amino acid residues
which can be inserted in or adjacent to a hypervariable region of
the antibody. Preferably at least one of the inserted residues has
a net positive charge or a net negative charge. For example, at
least one of the inserted residues may be a positively charged
residue, preferably arginine or lysine.
[0084] Examples of side chains typically having positive charge are
lysine, arginine, and histidine. Examples of side chains typically
having negative charge are aspartic acid and glutamic acid. These
side chains may undergo ionic interactions (positive residues
paired with negative residues), as well as polar interactions with
side chains having polar functional groups: tryptophan, serine,
threonine, tyrosine, cysteine, tyrosine, asparagine, and glutamine.
In addition, polar or ionic interactions may be mediated through
intervening solvent (such as water) or solute (e.g. phosphate or
sulfate) molecules.
[0085] Examples of residues which may be involved in hydrophobic
interactions, or non-polar Van der Waals interactions, are
typically alanine, valine, leucine, isoleucine, proline,
phenylalanine, tryptophan, methionine, and tyrosine; however, the
non-polar side chains of other residues, such as lysine or
arginine, may also participate in such interactions. Aromatic side
chains such as phenylalanine, tyrosine, and tryptophan may form
aromatic (pi) stacking interactions, or may act as hydrogen-bond
acceptors.
[0086] In addition, the main chain atoms of any residue (including
glycine) may undergo Van der Waals or hydrophobic interactions; and
the atoms nitrogen and carbonyl oxygen of the main chain, may
undergo polar (hydrogen-bonding) interactions. In some cases, a
covalent bond (disulfide) may be formed from a cysteine residue of
the antibody with a cysteine residue of the antigen.
[0087] Finally, post-translational modifications (e.g.,
glycosylation or phosphorylation) or a prosthetic group (e.g., heme
or zinc finger) may provide additional functional groups
(carboxylate or phosphate oxygens; zinc or iron atoms) for
interaction between antibody and antigen.
[0088] Thus, one may, for example, introduce one or more charged
amino acid residues in or adjacent to a hypervariable region of the
parent antibody in an appropriate three dimensional location, such
that the introduced residue or residues are able to form ion
pair(s) with one or more oppositely charged residues in the
antigen. Similarly, one can create hydrogen-bonding pair(s), Van
der Waals interactions, etc., by introducing appropriate amino acid
residues in an appropriate location in or adjacent to a
hypervariable region of the antibody.
[0089] The antibody variant may comprise additional alterations,
such as amino acid deletions or substitutions in the hypervariable
region of the antibody in which the insertion is made. This is
shown in the example below, wherein the hypervariable region was
modified by both amino acid substitutions as well as amino acid
insertions.
[0090] In general, any inserted amino acid residue or inserted
peptide will need to exit the existing antibody polypeptide chain
at a residue position (x), extend to a point sufficiently near to
the site of a new contact such that some portion of the amino acid
side chain or main chain of the peptide can form an interaction,
and return to reenter the existing antibody polypeptide chain at a
position (y) (where y>x in the linear sequence).
[0091] It is desirable that the inserted amino acid residue or
peptide not significantly perturb the structure of the antibody in
a global or local sense, beyond the vicinity of the newly inserted
amino acid residue or peptide. In particular, the inserted amino
acid residue or peptide preferably does not distort the FR residues
of the antibody, or residues of the antibody or antigen involved in
existing contacts. This may be evaluated in an actual or modeled
complex.
[0092] If both exit/reentry residues (x and y) lack significant
intramolecular and intermolecular contacts (i.e., both within the
antibody, and between antibody and antigen), then an amino acid or
peptide insertion may be accomplished by adding a peptide segment
between residues x and y, leaving residues x and y unchanged.
Alternatively, either or both residues x and y may be deleted and
replaced by a peptide segment of >2 residues.
[0093] Often, residues x and y, and/or intervening residues in the
parent antibody, may be involved in significant intramolecular and
intermolecular contacts. In this case, these interactions may be
maintained or replaced with residues contributing similar
interactions, while allowing for an inserted residue or peptide to
exit and reenter the chain. This may be accomplished by
substituting the two residues x and y and/or intervening residues
in the parent antibody with random residues, which can be
subsequently subjected to affinity screening (or screening for
other biological activities) to identify variants with improved
affinity.
[0094] This systematic method is illustrated in FIG. 3 for example,
where residues D41 and E42 in the VEGF antigen were identified as
potential candidates for interacting with introduced residues in
CDR H3 of the heavy chain variable domain of the parent
antibody.
[0095] Thus, as illustrated in FIGS. 4 and 5, D41 of the VEGF
antigen is able to form an ion pair with inserted residue R104c in
CDR H3 of variant antibody Y0313-2 of the Example below. FIG. 5
further shows how residue V104 in variant antibody Y0313-2 is able
to form a hydrophobic interaction with residues 93 to 95 of the
VEGF antigen. Thus, it can be seen that one identifies potential
areas where the contacts between antigen and antibody can be
improved, so as to increase the affinity of the antibody
variant.
[0096] Generally one makes changes in hypervariable regions
proximal to antigen when the antigen and antibody are complexed
together. For example, the hypervariable region of the parent
antibody which may be modified as disclosed herein generally has
one or more amino acid residues within about 20 .ANG. of one or
more amino acid residues of the antigen. The hypervariable region
to be altered herein may be one which, in the parent antibody, does
not make significant contact with antigen (i.e. a non-contacting
hypervariable region can be modified to become a contacting
hypervariable region). Preferably however, the hypervariable region
to be modified does contact antigen and the method herein serves to
increase the contacts between the antigen and the
already-contacting hypervariable region.
[0097] In another embodiment, one may identify hypervariable region
residues which interact with antigen by alanine-scanning
mutagenesis of the antigen and/or parent antibody (Muller et al.
Structure 6(9): 1153-1167 (1998)) or by other means. Hypervariable
regions identified as contacting antigen are candidates for amino
acid insertion(s) as herein disclosed.
[0098] Nucleic acid molecules encoding amino acid sequence variants
are prepared by a variety of methods known in the art. These
methods include, but are not limited to, oligonucleotide-mediated
(or site-directed) mutagenesis, PCR mutagenesis, and cassette
mutagenesis of an earlier prepared variant or a non-variant version
of the parent antibody. The preferred method for making variants is
site directed mutagenesis (see, e.g., Kunkel, Proc. Natl. Acad.
Sci. USA 82:488 (1985)). Moreover, a nucleic acid sequence can be
made synthetically, once the desired amino acid sequence is arrived
at conceptually. One can also make the antibody variant by peptide
synthesis, peptide ligation or other methods.
[0099] Following production of the antibody variant, the activity
of that molecule relative to the parent antibody may be determined.
As noted above, this may involve determining the binding affinity
and/or other biological activities of the antibody. In a preferred
embodiment of the invention, a panel of antibody variants are
prepared and are screened for binding affinity for the antigen
and/or potency in one or more biological activity assays. One or
more of the antibody variants selected from an initial screen are
optionally subjected to one or more further biological activity
assays to confirm that the antibody variant(s) have improved
activity in more than one assay.
[0100] One preferred method of making and screening insertion
mutants involves displaying antibody variants on the surface of
filamentous bacteriophage and selecting antibody variants based on
their affinity for antigen, by their kinetics of dissociation
(off-rate) from antigen, or some other screen for antibody affinity
or potency. This was the method used to identify antibody variants
with enhanced biological activity in the Example below.
[0101] Aside from the above insertions in the hypervariable region
of the parent antibody one may make other alterations in the amino
acid sequences of one or more of the hypervariable regions. For
example, the above amino acid insertions may be combined with
deletions or substitutions of other hypervariable region residues.
Moreover, one or more alterations (e.g. substitutions) of FR
residues may be introduced in the parent antibody where these
result in an improvement in the binding affinity of the antibody
variant for the antigen. Examples of framework region residues to
modify include those which non-covalently bind antigen directly
(Amit et al. Science 233:747-753 (1986)); interact with/effect the
conformation of a CDR (Chothia et al. J. Mol. Biol. 196:901-917
(1987)); and/or participate in the V.sub.L-V.sub.H interface (EP
239 400B1). Such amino acid sequence alterations may be present in
the parent antibody, may be made simulateously with the amino acid
insertion(s) herein or may be made after a variant with an amino
acid insertion is generated.
[0102] The antibody variants may be subjected to other
modifications, oftentimes depending on the intended use of the
antibody. Such modifications may involve further alteration of the
amino acid sequence, fusion to heterologous polypeptide(s) and/or
covalent modification. With respect to amino acid sequence
alterations, exemplary modifications are elaborated above. For
example, any cysteine residue not involved in maintaining the
proper conformation of the antibody variant also may be
substituted, generally with serine, to improve the oxidative
stability of the molecule and prevent aberrant cross linking.
Conversely, cysteine bond(s) may be added to the antibody to
improve its stability (particularly where the antibody is an
antibody fragment such as an Fv fragment). Another type of amino
acid variant has an altered glycosylation pattern. This may be
achieved by deleting one or more carbohydrate moieties found in the
antibody, and/or adding one or more glycosylation sites that are
not present in the antibody. Glycosylation of antibodies is
typically either N-linked or O-linked. N-linked refers to the
attachment of the carbohydrate moiety to the side chain of an
asparagine residue. The tripeptide sequences asparagine-X-serine
and asparagine-X-threonine, where X is any amino acid except
proline, are the recognition sequences for enzymatic attachment of
the carbohydrate moiety to the asparagine side chain. Thus, the
presence of either of these tripeptide sequences in a polypeptide
creates a potential glycosylation site. O-linked glycosylation
refers to the attachment of one of the sugars N-aceylgalactosamine,
galactose, or xylose to a hydroxyamino acid, most commonly serine
or threonine, although 5-hydroxyproline or 5-hydroxylysine may also
be used. Addition of glycosylation sites to the antibody is
conveniently accomplished by altering the amino acid sequence such
that it contains one or more of the above-described tripeptide
sequences (for N-linked glycosylation sites). The alteration may
also be made by the addition of, or substitution by, one or more
serine or threonine residues to the sequence of the original
antibody (for O-linked glycosylation sites).
[0103] Techniques for producing antibodies, which may be the parent
antibody and therefore require modification according to the
techniques elaborated herein, follow:
[0104] A. Antibody Preparation
[0105] (i) Antigen Preparation
[0106] Soluble antigens or fragments thereof, optionally conjugated
to other molecules, can be used as immunogens for generating
antibodies. For transmembrane molecules, such as receptors,
fragments of these (e.g. the extracellular domain of a receptor)
can be used as the immunogen. Alternatively, cells expressing the
transmembrane molecule can be used as the immunogen. Such cells can
be derived from a natural source (e.g. cancer cell lines) or may be
cells which have been transformed by recombinant techniques to
express the transmembrane molecule. Other antigens and forms
thereof useful for preparing antibodies will be apparent to those
in the art.
[0107] (ii) Polyclonal Antibodies
[0108] Polyclonal antibodies are preferably raised in animals by
multiple subcutaneous (sc) or intraperitoneal (ip) injections of
the relevant antigen and an adjuvant. It may be useful to conjugate
the relevant antigen to a protein that is immunogenic in the
species to be immunized, e.g., keyhole limpet hemocyanin, serum
albumin, bovine thyroglobulin, or soybean trypsin inhibitor using a
bifunctional or derivatizing agent, for example, maleimidobenzoyl
sulfosuccinimide ester (conjugation through cysteine residues),
N-hydroxysuccinimide (through lysine residues), glutaraldehyde,
succinic anhydride, SOCl.sub.2, or R.sup.1N.dbd.C.dbd.NR, where R
and R.sup.1 are different alkyl groups.
[0109] Animals are immunized against the antigen, immunogenic
conjugates, or derivatives by combining, e.g., 100 .mu.g or 5 .mu.g
of the protein or conjugate (for rabbits or mice, respectively)
with 3 volumes of Freund's complete adjuvant and injecting the
solution intradermally at multiple sites. One month later the
animals are boosted with 1/5 to 1/10 the original amount of peptide
or conjugate in Freund's complete adjuvant by subcutaneous
injection at multiple sites. Seven to 14 days later the animals are
bled and the serum is assayed for antibody titer. Animals are
boosted until the titer plateaus. Preferably, the animal is boosted
with the conjugate of the same antigen, but conjugated to a
different protein and/or through a different cross-linking reagent.
Conjugates also can be made in recombinant cell culture as protein
fusions. Also, aggregating agents such as alum are suitably used to
enhance the immune response.
[0110] (iii) Monoclonal Antibodies
[0111] Monoclonal antibodies may be made using the hybridoma method
first described by Kohler et al., Nature, 256:495 (1975), or may be
made by recombinant DNA methods (U.S. Pat. No. 4,816,567).
[0112] In the hybridoma method, a mouse or other appropriate host
animal, such as a hamster or macaque monkey, is immunized as
hereinabove described to elicit lymphocytes that produce or are
capable of producing antibodies that will specifically bind to the
protein used for immunization. Alternatively, lymphocytes may be
immunized in vitro. Lymphocytes then are fused with myeloma cells
using a suitable fusing agent, such as polyethylene glycol, to form
a hybridoma cell (Goding, Monoclonal Antibodies: Principles and
Practice, pp. 59-103 (Academic Press, 1986)).
[0113] The hybridoma cells thus prepared are seeded and grown in a
suitable culture medium that preferably contains one or more
substances that inhibit the growth or survival of the unfused,
parental myeloma cells. For example, if the parental myeloma cells
lack the enzyme hypoxanthine guanine phosphoribosyl transferase
(HGPRT or HPRT), the culture medium for the hybridomas typically
will include hypoxanthine, aminopterin, and thymidine (HAT medium),
which substances prevent the growth of HGPRT-deficient cells.
[0114] Preferred myeloma cells are those that fuse efficiently,
support stable high-level production of antibody by the selected
antibody-producing cells, and are sensitive to a medium such as HAT
medium. Among these, preferred myeloma cell lines are murine
myeloma lines, such as those derived from MOPC-21 and MPC-11 mouse
tumors available from the Salk Institute Cell Distribution Center,
San Diego, Calif. USA, and SP-2 or X63-Ag8-653 cells available from
the American Type Culture Collection, Rockville, Md. USA. Human
myeloma and mouse-human heteromyeloma cell lines also have been
described for the production of human monoclonal antibodies
(Kozbor, J. Immunol., 133:3001 (1984); Brodeur et al., Monoclonal
Antibody Production Techniques and Applications, pp. 51-63 (Marcel
Dekker, Inc., New York, 1987)).
[0115] Culture medium in which hybridoma cells are growing is
assayed for production of monoclonal antibodies directed against
the antigen. Preferably, the binding specificity of monoclonal
antibodies produced by hybridoma cells is determined by
immunoprecipitation or by an in vitro binding assay, such as
radioimmunoassay (RIA) or enzyme-linked immunoabsorbent assay
(ELISA).
[0116] After hybridoma cells are identified that produce antibodies
of the desired specificity, affinity, and/or activity, the clones
may be subcloned by limiting dilution procedures and grown by
standard methods (Goding, Monoclonal Antibodies: Principles and
Practice, pp. 59-103 (Academic Press, 1986)). Suitable culture
media for this purpose include, for example, D-MEM or RPMI-1640
medium. In addition, the hybridoma cells may be grown in vivo as
ascites tumors in an animal.
[0117] The monoclonal antibodies secreted by the subclones are
suitably separated from the culture medium, ascites fluid, or serum
by conventional immunoglobulin purification procedures such as, for
example, protein A-Sepharose, hydroxylapatite chromatography, gel
electrophoresis, dialysis, or affinity chromatography.
[0118] DNA encoding the monoclonal antibodies is readily isolated
and sequenced using conventional procedures (e.g., by using
oligonucleotide probes that are capable of binding specifically to
genes encoding the heavy and light chains of the monoclonal
antibodies). The hybridoma cells serve as a preferred source of
such DNA. Once isolated, the DNA may be placed into expression
vectors, which are then transfected into host cells such as E. coli
cells, simian COS cells, Chinese Hamster Ovary (CHO) cells, or
myeloma cells that do not otherwise produce immunoglobulin protein,
to obtain the synthesis of monoclonal antibodies in the recombinant
host cells. Recombinant production of antibodies will be described
in more detail below.
[0119] In a further embodiment, antibodies or antibody fragments
can be isolated from antibody phage libraries generated using the
techniques described in McCafferty et al., Nature, 348:552-554
(1990). Clackson et al., Nature, 352:624-628 (1991) and Marks et
al., J. Mol. Biol., 222:581-597 (1991) describe the isolation of
murine and human antibodies, respectively, using phage libraries.
Subsequent publications describe the production of high affinity
(nM range) human antibodies by chain shuffling (Marks et al.,
Bio/Technology, 10:779-783 (1992)), as well as combinatorial
infection and in vivo recombination as a strategy for constructing
very large phage libraries (Waterhouse et al., Nuc. Acids. Res.,
21:2265-2266 (1993)). Thus, these techniques are viable
alternatives to traditional monoclonal antibody hybridoma
techniques for isolation of monoclonal antibodies.
[0120] The DNA also may be modified, for example, by substituting
the coding sequence for human heavy- and light-chain constant
domains in place of the homologous murine sequences (U.S. Pat. No.
4,816,567; Morrison, et al., Proc. Natl. Acad. Sci. USA, 81:6851
(1984)), or by covalently joining to the immunoglobulin coding
sequence all or part of the coding sequence for a
non-immunoglobulin polypeptide.
[0121] Typically such non-immunoglobulin polypeptides are
substituted for the constant domains of an antibody, or they are
substituted for the variable domains of one antigen-combining site
of an antibody to create a chimeric bivalent antibody comprising
one antigen-combining site having specificity for an antigen and
another antigen-combining site having specificity for a different
antigen.
[0122] (iv) Humanized and Human Antibodies
[0123] A humanized antibody has one or more amino acid residues
introduced into it from a source which is non-human. These
non-human amino acid residues are often referred to as "import"
residues, which are typically taken from an "import" variable
domain. Humanization can be essentially performed following the
method of Winter and co-workers (Jones et al., Nature, 321:522-525
(1986); Riechmann et al., Nature, 332:323-327 (1988); Verhoeyen et
al., Science, 239:1534-1536 (1988)), by substituting rodent CDRs or
CDR sequences for the corresponding sequences of a human antibody.
Accordingly, such "humanized" antibodies are chimeric antibodies
(U.S. Pat. No. 4,816,567) wherein substantially less than an intact
human variable domain has been substituted by the corresponding
sequence from a non-human species. In practice, humanized
antibodies are typically human antibodies in which some CDR
residues and possibly some FR residues are substituted by residues
from analogous sites in rodent antibodies.
[0124] The choice of human variable domains, both light and heavy,
to be used in making the humanized antibodies is very important to
reduce antigenicity. According to the so-called "best-fit" method,
the sequence of the variable domain of a rodent antibody is
screened against the entire library of known human variable domain
sequences. The human sequence which is closest to that of the
rodent is then accepted as the human FR for the humanized antibody
(Sims et al., J. Immunol., 151:2296 (1993); Chothia et al., J. Mol.
Biol., 196:901 (1987)). Another method uses a particular FR derived
from the consensus sequence of all human antibodies of a particular
subgroup of light or heavy chains. The same FR may be used for
several different humanized antibodies (Carter et al., Proc. Natl.
Acad. Sci. USA, 89:4285 (1992); Presta et al., J. Immunol.,
151:2623 (1993)).
[0125] It is further important that antibodies be humanized with
retention of high affinity for the antigen and other favorable
biological properties. To achieve this goal, according to a
preferred method, humanized antibodies are prepared by a process of
analysis of the parental sequences and various conceptual humanized
products using three-dimensional models of the parental and
humanized sequences. Three-dimensional immunoglobulin models are
commonly available and are familiar to those skilled in the art.
Computer programs are available which illustrate and display
probable three-dimensional conformational structures of selected
candidate immunoglobulin sequences. Inspection of these displays
permits analysis of the likely role of the residues in the
functioning of the candidate immunoglobulin sequence, i.e., the
analysis of residues that influence the ability of the candidate
immunoglobulin to bind its antigen. In this way, FR residues can be
selected and combined from the recipient and import sequences so
that the desired antibody characteristic, such as increased
affinity for the target antigen(s), is achieved. In general, the
CDR residues are directly and most substantially involved in
influencing antigen binding.
[0126] Alternatively, it is now possible to produce transgenic
animals (e.g., mice) that are capable, upon immunization, of
producing a full repertoire of human antibodies in the absence of
endogenous immunoglobulin production. For example, it has been
described that the homozygous deletion of the antibody heavy-chain
joining region (J.sub.H) gene in chimeric and germ-line mutant mice
results in complete inhibition of endogenous antibody production.
Transfer of the human germ-line immunoglobulin gene array in such
germ-line mutant mice will result in the production of human
antibodies upon antigen challenge. See, e.g., Jakobovits et al.,
Proc. Natl. Acad. Sci. USA, 90:2551 (1993); Jakobovits et al.,
Nature, 362:255-258 (1993); Bruggermann et al., Year in Immuno.,
7:33 (1993); and Duchosal et al. Nature 355:258 (1992). Human
antibodies can also be derived from phage-display libraries
(Hoogenboom et al., J. Mol. Biol., 227:381 (1991); Marks et al., J.
Mol. Biol., 222:581-597 (1991); Vaughan et al. Nature Biotech
14:309 (1996)).
[0127] (v) Antibody Fragments
[0128] Various techniques have been developed for the production of
antibody fragments. Traditionally, these fragments were derived via
proteolytic digestion of intact antibodies (see, e.g., Morimoto et
al., Journal of Biochemical and Biophysical Methods 24:107-117
(1992) and Brennan et al., Science, 229:81 (1985)). However, these
fragments can now be produced directly by recombinant host cells.
For example, the antibody fragments can be isolated from the
antibody phage libraries discussed above. Alternatively, Fab'-SH
fragments can be directly recovered from E. coli and chemically
coupled to form F(ab').sub.2 fragments (Carter et al.,
Bio/Technology 10:163-167 (1992)). According to another approach,
F(ab').sub.2 fragments can be isolated directly from recombinant
host cell culture. Other techniques for the production of antibody
fragments will be apparent to the skilled practitioner. In other
embodiments, the antibody of choice is a single chain Fv fragment
(scFv). See WO 93/16185.
[0129] (vi) Multispecific Antibodies
[0130] Multispecific antibodies have binding specificities for at
least two different antigens. While such molecules normally will
only bind two antigens (i.e. bispecific antibodies, BsAbs),
antibodies with additional specificities such as trispecific
antibodies are encompassed by this expression when used herein.
Examples of BsAbs include those with one arm directed against a
tumor cell antigen and the other arm directed against a cytotoxic
trigger molecule such as anti-Fc.gamma.RI/anti-CD15,
anti-p185.sup.HER2/Fc.gamma.RIII (CD16), anti-CD3/anti-malignant
B-cell (1D10), anti-CD3/anti-p185.sup.HER2, anti-CD3/anti-p97,
anti-CD3/anti-renal cell carcinoma, anti-CD3/anti-OVCAR-3,
anti-CD3/L-D1 (anti-colon carcinoma), anti-CD3/anti-melanocyte
stimulating hormone analog, anti-EGF receptor/anti-CD3,
anti-CD3/anti-CAMA1, anti-CD3/anti-CD19, anti-CD3/MoV18,
anti-neural cell ahesion molecule (NCAM)/anti-CD3, anti-folate
binding protein (FBP)/anti-CD3, anti-pan carcinoma associated
antigen (AMOC-31)/anti-CD3; BsAbs with one arm which binds
specifically to a tumor antigen and one arm which binds to a toxin
such as anti-saporin/anti-Id-1, anti-CD22/anti-saporin,
anti-CD7/anti-saporin, anti-CD38/anti-saporin, anti-CEA/anti-ricin
A chain, anti-CEA/anti-vinca alkaloid; BsAbs for converting enzyme
activated prodrugs such as anti-CD30/anti-alkaline phosphatase
(which catalyzes conversion of mitomycin phosphate prodrug to
mitomycin alcohol); BsAbs which can be used as fibrinolytic agents
such as anti-fibrin/anti-tissue plasminogen activator (tPA),
anti-fibrin/anti-urokinase-type plasminogen activator (uPA); BsAbs
for targeting immune complexes to cell surface receptors such as
anti-low density lipoprotein (LDL)/anti-Fc receptor (e.g.
Fc.gamma.RI, Fc.gamma.RII or Fc.gamma.RIII); BsAbs for use in
therapy of infectious diseases such as anti-CD3/anti-herpes simplex
virus (HSV), anti-T-cell receptor:CD3 complex/anti-influenza,
anti-Fc.gamma.R/anti-HIV; BsAbs for tumor detection in vitro or in
vivo such as anti-CEA/anti-EOTUBE, anti-CEA/anti-DPTA,
anti-p185.sup.HER2/anti-hapten; BsAbs as vaccine adjuvants; and
BsAbs as diagnostic tools such as anti-rabbit IgG/anti-ferritin,
anti-horse radish peroxidase (HRP)/anti-hormone,
anti-somatostatin/anti-substance P, anti-HRP/anti-FITC. Examples of
trispecific antibodies include anti-CD3/anti-CD4/anti-CD37,
anti-CD3/anti-CD5/anti-CD37 and anti-CD3/anti-CD8/anti-CD37.
Bispecific antibodies can be prepared as full length antibodies or
antibody fragments (e.g. F(ab').sub.2 bispecific antibodies).
[0131] Methods for making bispecific antibodies are known in the
art. Traditional production of full length bispecific antibodies is
based on the coexpression of two immunoglobulin heavy chain-light
chain pairs, where the two chains have different specificities
(Millstein et al., Nature, 305:537-539 (1983)). Because of the
random assortment of immunoglobulin heavy and light chains, these
hybridomas (quadromas) produce a potential mixture of 10 different
antibody molecules, of which only one has the correct bispecific
structure. Purification of the correct molecule, which is usually
done by affinity chromatography steps, is rather cumbersome, and
the product yields are low. Similar procedures are disclosed in WO
93/08829, and in Traunecker et al., EMBO J., 10:3655-3659
(1991).
[0132] According to a different approach, antibody variable domains
with the desired binding specificities (antibody-antigen combining
sites) are fused to immunoglobulin constant domain sequences. The
fusion preferably is with an immunoglobulin heavy chain constant
domain, comprising at least part of the hinge, CH2, and CH3
regions. It is preferred to have the first heavy-chain constant
region (CH1) containing the site necessary for light chain binding,
present in at least one of the fusions. DNAs encoding the
immunoglobulin heavy chain fusions and, if desired, the
immunoglobulin light chain, are inserted into separate expression
vectors, and are co-transfected into a suitable host organism. This
provides for great flexibility in adjusting the mutual proportions
of the three polypeptide fragments in embodiments when unequal
ratios of the three polypeptide chains used in the construction
provide the optimum yields. It is, however, possible to insert the
coding sequences for two or all three polypeptide chains in one
expression vector when the expression of at least two polypeptide
chains in equal ratios results in high yields or when the ratios
are of no particular significance.
[0133] In a preferred embodiment of this approach, the bispecific
antibodies are composed of a hybrid immunoglobulin heavy chain with
a first binding specificity in one arm, and a hybrid immunoglobulin
heavy chain-light chain pair (providing a second binding
specificity) in the other arm. It was found that this asymmetric
structure facilitates the separation of the desired bispecific
compound from unwanted immunoglobulin chain combinations, as the
presence of an immunoglobulin light chain in only one half of the
bispecific molecule provides for a facile way of separation. This
approach is disclosed in WO 94/04690. For further details of
generating bispecific antibodies see, for example, Suresh et al.,
Methods in Enzymology, 121:210 (1986).
[0134] According to another approach described in WO96/27011, the
interface between a pair of antibody molecules can be engineered to
maximize the percentage of heterodimers which are recovered from
recombinant cell culture. The preferred interface comprises at
least a part of the C.sub.H3 domain of an antibody constant domain.
In this method, one or more small amino acid side chains from the
interface of the first antibody molecule are replaced with larger
side chains (e.g. tyrosine or tryptophan). Compensatory "cavities"
of identical or similar size to the large side chain(s) are created
on the interface of the second antibody molecule by replacing large
amino acid side chains with smaller ones (e.g. alanine or
threonine). This provides a mechanism for increasing the yield of
the heterodimer over other unwanted end-products such as
homodimers.
[0135] Bispecific antibodies include cross-linked or
"heteroconjugate" antibodies. For example, one of the antibodies in
the heteroconjugate can be coupled to avidin, the other to biotin.
Such antibodies have, for example, been proposed to target immune
system cells to unwanted cells (U.S. Pat. No. 4,676,980), and for
treatment of HIV infection (WO 91/00360, WO 92/200373, and EP
03089). Heteroconjugate antibodies may be made using any convenient
cross-linking methods. Suitable cross-linking agents are well known
in the art, and are disclosed in U.S. Pat. No. 4,676,980, along
with a number of cross-linking techniques.
[0136] Techniques for generating bispecific antibodies from
antibody fragments have also been described in the literature. For
example, bispecific antibodies can be prepared using chemical
linkage. Brennan et al., Science, 229: 81 (1985) describe a
procedure wherein intact antibodies are proteolytically cleaved to
generate F(ab').sub.2 fragments. These fragments are reduced in the
presence of the dithiol complexing agent sodium arsenite to
stabilize vicinal dithiols and prevent intermolecular disulfide
formation. The Fab' fragments generated are then converted to
thionitrobenzoate (TNB) derivatives. One of the Fab'-TNB
derivatives is then reconverted to the Fab'-thiol by reduction with
mercaptoethylamine and is mixed with an equimolar amount of the
other Fab'-TNB derivative to form the bispecific antibody. The
bispecific antibodies produced can be used as agents for the
selective immobilization of enzymes.
[0137] Recent progress has facilitated the direct recovery of
Fab'-SH fragments from E. coli, which can be chemically coupled to
form bispecific antibodies. Shalaby et al., J. Exp. Med., 175:
217-225 (1992) describe the production of a fully humanized
bispecific antibody F(ab').sub.2 molecule. Each Fab' fragment was
separately secreted from E. coli and subjected to directed chemical
coupling in vitro to form the bispecific antibody. The bispecific
antibody thus formed was able to bind to cells overexpressing the
ErbB2 receptor and normal human T cells, as well as trigger the
lytic activity of human cytotoxic lymphocytes against human breast
tumor targets.
[0138] Various techniques for making and isolating bispecific
antibody fragments directly from recombinant cell culture have also
been described. For example, bispecific antibodies have been
produced using leucine zippers. Kostelny et al., J. Immunol.,
148(5):1547-1553 (1992). The leucine zipper peptides from the Fos
and Jun proteins were linked to the Fab' portions of two different
antibodies by gene fusion. The antibody homodimers were reduced at
the hinge region to form monomers and then re-oxidized to form the
antibody heterodimers. This method can also be utilized for the
production of antibody homodimers. The "diabody" technology
described by Hollinger et al., Proc. Natl. Acad. Sci. USA,
90:6444-6448 (1993) has provided an alternative mechanism for
making bispecific antibody fragments. The fragments comprise a
heavy-chain variable domain (V.sub.H) connected to a light-chain
variable domain (V.sub.L) by a linker which is too short to allow
pairing between the two domains on the same chain. Accordingly, the
V.sub.H and V.sub.L domains of one fragment are forced to pair with
the complementary V.sub.L and V.sub.H domains of another fragment,
thereby forming two antigen-binding sites. Another strategy for
making bispecific antibody fragments by the use of single-chain Fv
(sFv) dimers has also been reported. See Gruber et al., J.
Immunol., 152:5368 (1994).
[0139] Antibodies with more than two valencies are contemplated.
For example, trispecific antibodies can be prepared. Tutt et al. J.
Immunol. 147: 60 (1991).
[0140] (vii) Effector Function Engineering
[0141] It may be desirable to modify the antibody of the invention
with respect to effector function, so as to enhance the
effectiveness of the antibody in treating cancer, for example. For
example cysteine residue(s) may be introduced in the Fc region,
thereby allowing interchain disulfide bond formation in this
region. The homodimeric antibody thus generated may have improved
internalization capability and/or increased complement-mediated
cell killing and antibody-dependent cellular cytotoxicity (ADCC).
See Caron et al., J. Exp Med. 176:1191-1195 (1992) and Shopes, B.
J. Immunol. 148:2918-2922 (1992). Homodimeric antibodies with
enhanced anti-tumor activity may also be prepared using
heterobifunctional cross-linkers as described in Wolff et al.
Cancer Research 53:2560-2565 (1993). Alternatively, an antibody can
be engineered which has dual Fc regions and may thereby have
enhanced complement lysis and ADCC capabilities. See Stevenson et
al. Anti-Cancer Drug Design 3:219-230 (1989).
[0142] (viii) Immunoconjugates
[0143] The invention also pertains to immunoconjugates comprising
the antibody described herein conjugated to a cytotoxic agent such
as a chemotherapeutic agent, toxin (e.g. an enzymatically active
toxin of bacterial, fungal, plant or animal origin, or fragments
thereof), or a radioactive isotope (i.e., a radioconjugate).
[0144] Chemotherapeutic agents useful in the generation of such
immunoconjugates have been described above. Enzymatically active
toxins and fragments thereof which can be used include diphtheria A
chain, nonbinding active fragments of diphtheria toxin, exotoxin A
chain (from Pseudomonas aeruginosa), ricin A chain, abrin A chain,
modeccin A chain, alpha-sarcin, Aleurites fordii proteins, dianthin
proteins, Phytolaca americana proteins (PAPI, PAPII, and PAP-S),
momordica charantia inhibitor, curcin, crotin, sapaonaria
officinalis inhibitor, gelonin, mitogellin, restrictocin,
phenomycin, enomycin and the tricothecenes. A variety of
radionuclides are available for the production of radioconjugate
antibodies. Examples include .sup.212Bi, .sup.131I, .sup.131In,
.sup.90Y and .sup.186Re.
[0145] Conjugates of the antibody and cytotoxic agent are made
using a variety of bifunctional protein coupling agents such as
N-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP),
iminothiolane (IT), bifunctional derivatives of imidoesters (such
as dimethyl adipimidate HCL), active esters (such as disuccinimidyl
suberate), aldehydes (such as glutareldehyde), bis-azido compounds
(such as bis (p-azidobenzoyl) hexanediamine), bis-diazonium
derivatives (such as bis-(p-diazoniumbenzoyl)-ethylenediamine),
diisocyanates (such as tolyene 2,6-diisocyanate), and bis-active
fluorine compounds (such as 1,5-difluoro-2,4-dinitrobenzene). For
example, a ricin immunotoxin can be prepared as described in
Vitetta et al. Science 238: 1098 (1987). Carbon-14-labeled
1-isothiocyanatobenzyl-3-methyldiethylene triaminepentaacetic acid
(MX-DTPA) is an exemplary chelating agent for conjugation of
radionucleotide to the antibody. See WO94/11026.
[0146] In another embodiment, the antibody may be conjugated to a
"receptor" (such streptavidin) for utilization in tumor
pretargeting wherein the antibody-receptor conjugate is
administered to the patient, followed by removal of unbound
conjugate from the circulation using a clearing agent and then
administration of a "ligand" (e.g. avidin) which is conjugated to a
cytotoxic agent (e.g. a radionucleotide).
[0147] (ix) Immunoliposomes
[0148] The antibody variants disclosed herein may also be
formulated as immunoliposomes. Liposomes containing the antibody
are prepared by methods known in the art, such as described in
Epstein et al., Proc. Natl. Acad. Sci. USA, 82:3688 (1985); Hwang
et al., Proc. Natl Acad. Sci. USA, 77:4030 (1980); and U.S. Pat.
Nos. 4,485,045 and 4,544,545. Liposomes with enhanced circulation
time are disclosed in U.S. Pat. No. 5,013,556.
[0149] Particularly useful liposomes can be generated by the
reverse phase evaporation method with a lipid composition
comprising phosphatidylcholine, cholesterol and PEG-derivatized
phosphatidylethanolamine (PEG-PE). Liposomes are extruded through
filters of defined pore size to yield liposomes with the desired
diameter. Fab' fragments of the antibody of the present invention
can be conjugated to the liposomes as described in Martin et al. J.
Biol. Chem. 257: 286-288 (1982) via a disulfide interchange
reaction. A chemotherapeutic agent (such as Doxorubicin) is
optionally contained within the liposome. See Gabizon et al. J.
National Cancer Inst.81(19)1484 (1989)
[0150] (x) Antibody Dependent Enzyme Mediated Prodrug Therapy
(ADEPT)
[0151] The antibody of the present invention may also be used in
ADEPT by conjugating the antibody to a prodrug-activating enzyme
which converts a prodrug (e.g. a peptidyl chemotherapeutic agent,
see WO81/01145) to an active anti-cancer drug. See, for example, WO
88/07378 and U.S. Pat. No. 4,975,278.
[0152] The enzyme component of the immunoconjugate useful for ADEPT
includes any enzyme capable of acting on a prodrug in such a way so
as to covert it into its more active, cytotoxic form.
[0153] Enzymes that are useful in the method of this invention
include, but are not limited to, alkaline phosphatase useful for
converting phosphate-containing prodrugs into free drugs;
arylsulfatase useful for converting sulfate-containing prodrugs
into free drugs; cytosine deaminase useful for converting non-toxic
5-fluorocytosine into the anti-cancer drug, 5-fluorouracil;
proteases, such as serratia protease, thermolysin, subtilisin,
carboxypeptidases and cathepsins (such as cathepsins B and L), that
are useful for converting peptide-containing prodrugs into free
drugs; D-alanylcarboxypeptidases, useful for converting prodrugs
that contain D-amino acid substituents; carbohydrate-cleaving
enzymes such as beta-galactosidase and neuraminidase useful for
converting glycosylated prodrugs into free drugs; beta-lactamase
useful for converting drugs derivatized with beta-lactams into free
drugs; and penicillin amidases, such as penicillin V amidase or
penicillin G amidase, useful for converting drugs derivatized at
their amine nitrogens with phenoxyacetyl or phenylacetyl groups,
respectively, into free drugs. Alternatively, antibodies with
enzymatic activity, also known in the art as "abzymes", can be used
to convert the prodrugs of the invention into free active drugs
(see, e.g., Massey, Nature 328: 457-458 (1987)). Antibody-abzyme
conjugates can be prepared as described herein for delivery of the
abzyme to a tumor cell population.
[0154] The enzymes of this invention can be covalently bound to the
antibody variant by techniques well known in the art such as the
use of the heterobifunctional crosslinking reagents discussed
above. Alternatively, fusion proteins comprising at least the
antigen binding region of an antibody of the invention linked to at
least a functionally active portion of an enzyme of the invention
can be constructed using recombinant DNA techniques well known in
the art (see, e.g., Neuberger et al., Nature, 312: 604-608
(1984)).
[0155] (xi) Antibody-Salvage Receptor Binding Epitope Fusions.
[0156] In certain embodiments of the invention, it may be desirable
to use an antibody fragment, rather than an intact antibody, to
increase tumor penetration, for example. In this case, it may be
desirable to modify the antibody fragment in order to increase its
serum half life. This may be achieved, for example, by
incorporation of a salvage receptor binding epitope into the
antibody fragment (e.g. by mutation of the appropriate region in
the antibody fragment or by incorporating the epitope into a
peptide tag that is then fused to the antibody fragment at either
end or in the middle, e.g., by DNA or peptide synthesis).
[0157] The salvage receptor binding epitope preferably constitutes
a region wherein any one or more amino acid residues from one or
two loops of a Fc domain are transferred to an analogous position
of the antibody fragment. Even more preferably, three or more
residues from one or two loops of the Fc domain are transferred.
Still more preferred, the epitope is taken from the CH2 domain of
the Fc region (e.g., of an IgG) and transferred to the CH1, CH3, or
V.sub.H region, or more than one such region, of the antibody.
Alternatively, the epitope is taken from the CH2 domain of the Fc
region and transferred to the C.sub.L region or V.sub.L region, or
both, of the antibody fragment. See, e.g., U.S. Pat. No. 5,739,277,
issued Apr. 14, 1998.
[0158] (xii) Covalent Modifications
[0159] Covalent modifications of the antibody are included within
the scope of this invention. They may be made by chemical synthesis
or by enzymatic or chemical cleavage of the antibody, if
applicable. Other types of covalent modifications of the antibody
are introduced into the molecule by reacting targeted amino acid
residues of the antibody with an organic derivatizing agent that is
capable of reacting with selected side chains or the N- or
C-terminal residues.
[0160] Removal of any carbohydrate moieties present on the antibody
may be accomplished chemically or enzymatically. Chemical
deglycosylation requires exposure of the antibody to the compound
trifluoromethanesulfonic acid, or an equivalent compound. This
treatment results in the cleavage of most or all sugars except the
linking sugar (N-acetylglucosamine or N-acetylgalactosamine), while
leaving the antibody intact. Chemical deglycosylation is described
by Hakimuddin, et al. Arch. Biochem. Biophys. 259:52 (1987) and by
Edge et al. Anal. Biochem., 118:131 (1981). Enzymatic cleavage of
carbohydrate moieties on antibodies can be achieved by the use of a
variety of endo- and exo-glycosidases as described by Thotakura et
al. Meth. Enzymol. 138:350 (1987).
[0161] Another type of covalent modification of the antibody
comprises linking the antibody to one of a variety of
nonproteinaceous polymers, e.g., polyethylene glycol, polypropylene
glycol, or polyoxyalkylenes, in the manner set forth in U.S. Pat.
No. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or
4,179,337.
[0162] B. Vectors, Host Cells and Recombinant Methods
[0163] The invention also provides isolated nucleic acid encoding
an antibody variant as disclosed herein, vectors and host cells
comprising the nucleic acid, and recombinant techniques for the
production of the antibody variant.
[0164] For recombinant production of the antibody variant, the
nucleic acid encoding it is isolated and inserted into a replicable
vector for further cloning (amplification of the DNA) or for
expression. DNA encoding the monoclonal antibody variant is readily
isolated and sequenced using conventional procedures (e.g., by
using oligonucleotide probes that are capable of binding
specifically to genes encoding the heavy and light chains of the
antibody variant). Many vectors are available. The vector
components generally include, but are not limited to, one or more
of the following: a signal sequence, an origin of replication, one
or more marker genes, an enhancer element, a promoter, and a
transcription termination sequence.
[0165] (i) Signal Sequence Component
[0166] The antibody variant of this invention may be produced
recombinantly not only directly, but also as a fusion polypeptide
with a heterologous polypeptide, which is preferably a signal
sequence or other polypeptide having a specific cleavage site at
the N-terminus of the mature protein or polypeptide. The
heterologous signal sequence selected preferably is one that is
recognized and processed (i.e., cleaved by a signal peptidase) by
the host cell. For prokaryotic host cells that do not recognize and
process the native antibody signal sequence, the signal sequence is
substituted by a prokaryotic signal sequence selected, for example,
from the group of the alkaline phosphatase, penicillinase, lpp, or
heat-stable enterotoxin II leaders. For yeast secretion the native
signal sequence may be substituted by, e.g., the yeast invertase
leader, .alpha. factor leader (including Saccharomyces and
Kluyveromyces .alpha.-factor leaders), or acid phosphatase leader,
the C. albicans glucoamylase leader, or the signal described in WO
90/13646. In mammalian cell expression, mammalian signal sequences
as well as viral secretory leaders, for example, the herpes simplex
gD signal, are available.
[0167] The DNA for such precursor region is ligated in reading
frame to DNA encoding the antibody variant.
[0168] (ii) Origin of Replication Component
[0169] Both expression and cloning vectors contain a nucleic acid
sequence that enables the vector to replicate in one or more
selected host cells. Generally, in cloning vectors this sequence is
one that enables the vector to replicate independently of the host
chromosomal DNA, and includes origins of replication or
autonomously replicating sequences. Such sequences are well known
for a variety of bacteria, yeast, and viruses. The origin of
replication from the plasmid pBR322 is suitable for most
Gram-negative bacteria, the 2.mu. plasmid origin is suitable for
yeast, and various viral origins (SV40, polyoma, adenovirus, VSV or
BPV) are useful for cloning vectors in mammalian cells. Generally,
the origin of replication component is not needed for mammalian
expression vectors (the SV40 origin may typically be used only
because it contains the early promoter).
[0170] (iii) Selection Gene Component
[0171] Expression and cloning vectors may contain a selection gene,
also termed a selectable marker. Typical selection genes encode
proteins that (a) confer resistance to antibiotics or other toxins,
e.g., ampicillin, neomycin, methotrexate, or tetracycline, (b)
complement auxotrophic deficiencies, or (c) supply critical
nutrients not available from complex media, e.g., the gene encoding
D-alanine racemase for Bacilli.
[0172] One example of a selection scheme utilizes a drug to arrest
growth of a host cell. Those cells that are successfully
transformed with a heterologous gene produce a protein conferring
drug resistance and thus survive the selection regimen. Examples of
such dominant selection use the drugs neomycin, mycophenolic acid
and hygromycin.
[0173] Another example of suitable selectable markers for mammalian
cells are those that enable the identification of cells competent
to take up the antibody nucleic acid, such as DHFR, thymidine
kinase, metallothionein-I and -II, preferably primate
metallothionein genes, adenosine deaminase, ornithine
decarboxylase, etc.
[0174] For example, cells transformed with the DHFR selection gene
are first identified by culturing all of the transformants in a
culture medium that contains methotrexate (Mtx), a competitive
antagonist of DHFR. An appropriate host cell when wild-type DHFR is
employed is the Chinese hamster ovary (CHO) cell line deficient in
DHFR activity.
[0175] Alternatively, host cells (particularly wild-type hosts that
contain endogenous DHFR) transformed or co-transformed with DNA
sequences encoding antibody, wild-type DHFR protein, and another
selectable marker such as aminoglycoside 3'-phosphotransferase
(APH) can be selected by cell growth in medium containing a
selection agent for the selectable marker such as an
aminoglycosidic antibiotic, e.g., kanamycin, neomycin, or G418. See
U.S. Pat. No. 4,965,199.
[0176] A suitable selection gene for use in yeast is the trp1 gene
present in the yeast plasmid YRp7 (Stinchcomb et al., Nature,
282:39 (1979)). The trp1 gene provides a selection marker for a
mutant strain of yeast lacking the ability to grow in tryptophan,
for example, ATCC No. 44076 or PEP4-1. Jones, Genetics, 85:12
(1977). The presence of the trp1 lesion in the yeast host cell
genome then provides an effective environment for detecting
transformation by growth in the absence of tryptophan. Similarly,
Leu2-deficient yeast strains (ATCC 20,622 or 38,626) are
complemented by known plasmids bearing the Leu2 gene.
[0177] In addition, vectors derived from the 1.6 .mu.m circular
plasmid pKD1 can be used for transformation of Kluyveromyces
yeasts. Alternatively, an expression system for large-scale
production of recombinant calf chymosin was reported for K. lactis.
Van den Berg, Bio/Technology, 8:135 (1990). Stable multi-copy
expression vectors for secretion of mature recombinant human serum
albumin by industrial strains of Kluyveromyces have also been
disclosed. Fleer et al., Bio/Technology, 9:968-975 (1991).
[0178] (iv) Promoter Component
[0179] Expression and cloning vectors usually contain a promoter
that is recognized by the host organism and is operably linked to
the antibody nucleic acid. Promoters suitable for use with
prokaryotic hosts include the phoA promoter, beta-lactamase and
lactose promoter systems, alkaline phosphatase, a tryptophan (trp)
promoter system, and hybrid promoters such as the tac promoter.
However, other known bacterial promoters are suitable. Promoters
for use in bacterial systems also will contain a Shine-Dalgarno
(S.D.) sequence operably linked to the DNA encoding the
antibody.
[0180] Promoter sequences are known for eukaryotes. Virtually all
eukaryotic genes have an AT-rich region located approximately 25 to
30 bases upstream from the site where transcription is initiated.
Another sequence found 70 to 80 bases upstream from the start of
transcription of many genes is a CNCAAT region where N may be any
nucleotide. At the 3' end of most eukaryotic genes is an AATAAA
sequence that may be the signal for addition of the poly A tail to
the 3' end of the coding sequence. All of these sequences are
suitably inserted into eukaryotic expression vectors.
[0181] Examples of suitable promoting sequences for use with yeast
hosts include the promoters for 3-phosphoglycerate kinase or other
glycolytic enzymes, such as enolase, glyceraldehyde-3-phosphate
dehydrogenase, hexokinase, pyruvate decarboxylase,
phospho-fructokinase, glucose-6-phosphate isomerase,
3-phosphoglycerate mutase, pyruvate kinase, triosephosphate
isomerase, phosphoglucose isomerase, and glucokinase.
[0182] Other yeast promoters, which are inducible promoters having
the additional advantage of transcription controlled by growth
conditions, are the promoter regions for alcohol dehydrogenase 2,
isocytochrome C, acid phosphatase, degradative enzymes associated
with nitrogen metabolism, metallothionein,
glyceraldehyde-3-phosphate dehydrogenase, and enzymes responsible
for maltose and galactose utilization. Suitable vectors and
promoters for use in yeast expression are further described in EP
73,657. Yeast enhancers also are advantageously used with yeast
promoters.
[0183] Antibody transcription from vectors in mammalian host cells
is controlled, for example, by promoters obtained from the genomes
of viruses such as polyoma virus, fowlpox virus, adenovirus (such
as Adenovirus 2), bovine papilloma virus, avian sarcoma virus,
cytomegalovirus, a retrovirus, hepatitis-B virus and most
preferably Simian Virus 40 (SV40), from heterologous mammalian
promoters, e.g., the actin promoter or an immunoglobulin promoter,
from heat-shock promoters, provided such promoters are compatible
with the host cell systems.
[0184] The early and late promoters of the SV40 virus are
conveniently obtained as an SV40 restriction fragment that also
contains the SV40 viral origin of replication. The immediate early
promoter of the human cytomegalovirus is conveniently obtained as a
HindIII E restriction fragment. A system for expressing DNA in
mammalian hosts using the bovine papilloma virus as a vector is
disclosed in U.S. Pat. No. 4,419,446. A modification of this system
is described in U.S. Pat. No. 4,601,978. Alternatively, the rous
sarcoma virus long terminal repeat can be used as the promoter.
[0185] (v) Enhancer Element Component
[0186] Transcription of a DNA encoding the antibody of this
invention by higher eukaryotes is often increased by inserting an
enhancer sequence into the vector. Many enhancer sequences are now
known from mammalian genes (globin, elastase, albumin,
alpha-fetoprotein, and insulin). Typically, however, one will use
an enhancer from a eukaryotic cell virus. Examples include the SV40
enhancer on the late side of the replication origin (bp 100-270),
the cytomegalovirus early promoter enhancer, the polyoma enhancer
on the late side of the replication origin, and adenovirus
enhancers. See also Yaniv, Nature 297:17-18 (1982) on enhancing
elements for activation of eukaryotic promoters. The enhancer may
be spliced into the vector at a position 5' or 3' to the
antibody-encoding sequence, but is preferably located at a site 5'
from the promoter.
[0187] (vi) Transcription Termination Component
[0188] Expression vectors used in eukaryotic host cells (yeast,
fungi, insect, plant, animal, human, or nucleated cells from other
multicellular organisms) will also contain sequences necessary for
the termination of transcription and for stabilizing the mRNA. Such
sequences are commonly available from the 5' and, occasionally 3',
untranslated regions of eukaryotic or viral DNAs or cDNAs. These
regions contain nucleotide segments transcribed as polyadenylated
fragments in the untranslated portion of the mRNA encoding the
antibody. One useful transcription termination component is the
bovine growth hormone polyadenylation region. See WO94/11026 and
the expression vector disclosed therein.
[0189] (vii) Selection and Transformation of Host Cells
[0190] Suitable host cells for cloning or expressing the DNA in the
vectors herein are the prokaryote, yeast, or higher eukaryote cells
described above. Suitable prokaryotes for this purpose include
eubacteria, such as Gram-negative or Gram-positive organisms, for
example, Enterobacteriaceae such as Escherichia, e.g., E. coli,
Enterobacter, Erwinia, Klebsiella, Proteus, Salmonella, e.g.,
Salmonella typhimurium, Serratia, e.g., Serratia marcescans, and
Shigella, as well as Bacilli such as B. subtilis and B.
licheniformis (e.g., B. licheniformis 41P disclosed in DD 266,710
published 12 Apr. 1989), Pseudomonas such as P. aeruginosa, and
Streptomyces. One preferred E. coli cloning host is E. coli 294
(ATCC 31,446), although other strains such as E. coli B, E. coli
X1776 (ATCC 31,537), and E. coli W3110 (ATCC 27,325) are suitable.
These examples are illustrative rather than limiting.
[0191] In addition to prokaryotes, eukaryotic microbes such as
filamentous fungi or yeast are suitable cloning or expression hosts
for antibody-encoding vectors. Saccharomyces cerevisiae, or common
baker's yeast, is the most commonly used among lower eukaryotic
host microorganisms. However, a number of other genera, species,
and strains are commonly available and useful herein, such as
Schizosaccharomyces pombe; Kluyveromyces hosts such as, e.g., K.
lactis, K. fragilis (ATCC 12,424), K. bulgaricus (ATCC 16,045), K.
wickeramii (ATCC 24,178), K. waltii (ATCC 56,500), K. drosophilarum
(ATCC 36,906), K. thermotolerans, and K. marxianus; yarrowia (EP
402,226); Pichia pastoris (EP 183,070); Candida; Trichoderma reesia
(EP 244,234); Neurospora crassa; Schwanniomyces such as
Schwanniomyces occidentalis; and filamentous fungi such as, e.g.,
Neurospora, Penicillium, Tolypocladium, and Aspergillus hosts such
as A. nidulans and A. niger.
[0192] Suitable host cells for the expression of glycosylated
antibody are derived from multicellular organisms. Examples of
invertebrate cells include plant and insect cells. Numerous
baculoviral strains and variants and corresponding permissive
insect host cells from hosts such as Spodoptera frugiperda
(caterpillar), Aedes aegypti (mosquito), Aedes albopictus
(mosquito), Drosophila melanogaster (fruitfly), and Bombyx mori
have been identified. A variety of viral strains for transfection
are publicly available, e.g., the L-1 variant of Autographa
californica NPV and the Bm-5 strain of Bombyx mori NPV, and such
viruses may be used as the virus herein according to the present
invention, particularly for transfection of Spodoptera frugiperda
cells. Plant cell cultures of cotton, corn, potato, soybean,
petunia, tomato, and tobacco can also be utilized as hosts.
[0193] However, interest has been greatest in vertebrate cells, and
propagation of vertebrate cells in culture (tissue culture) has
become a routine procedure. Examples of useful mammalian host cell
lines are monkey kidney CV1 line transformed by SV40 (COS-7, ATCC
CRL 1651); human embryonic kidney line (293 or 293 cells subcloned
for growth in suspension culture, Graham et al., J. Gen Virol.
36:59 (1977)); baby hamster kidney cells (BHK, ATCC CCL 10);
Chinese hamster ovary cells/-DHFR (CHO, Urlaub et al., Proc. Natl.
Acad. Sci. USA 77:4216 (1980)); mouse sertoli cells (TM4, Mather,
Biol. Reprod. 23:243-251 (1980)); monkey kidney cells (CV1 ATCC CCL
70); African green monkey kidney cells (VERO-76, ATCC CRL-1587);
human cervical carcinoma cells (HELA, ATCC CCL 2); canine kidney
cells (MDCK, ATCC CCL 34); buffalo rat liver cells (BRL 3A, ATCC
CRL 1442); human lung cells (W138, ATCC CCL 75); human liver cells
(Hep G2, HB 8065); mouse mammary tumor (MMT 060562, ATCC CCL51);
TR1 cells (Mather et al., Annals N.Y. Acad. Sci. 383:44-68 (1982));
MRC 5 cells; FS4 cells; and a human hepatoma line (Hep G2).
[0194] Host cells are transformed with the above-described
expression or cloning vectors for antibody production and cultured
in conventional nutrient media modified as appropriate for inducing
promoters, selecting transformants, or amplifying the genes
encoding the desired sequences.
[0195] (viii) Culturing the Host Cells
[0196] The host cells used to produce the antibody variant of this
invention may be cultured in a variety of media. Commercially
available media such as Ham's F10 (Sigma), Minimal Essential Medium
((MEM), (Sigma), RPMI-1640 (Sigma), and Dulbecco's Modified Eagle's
Medium ((DMEM), Sigma) are suitable for culturing the host cells.
In addition, any of the media described in Ham et al., Meth. Enz.
58:44 (1979), Barnes et al., Anal. Biochem. 102:255 (1980), U.S.
Pat. Nos. 4,767,704; 4,657,866; 4,927,762; 4,560,655; or 5,122,469;
WO 90/03430; WO 87/00195; or U.S. Pat. No. Re. 30,985 may be used
as culture media for the host cells. Any of these media may be
supplemented as necessary with hormones and/or other growth factors
(such as insulin, transferrin, or epidermal growth factor), salts
(such as sodium chloride, calcium, magnesium, and phosphate),
buffers (such as HEPES), nucleotides (such as adenosine and
thymidine), antibiotics (such as GENTAMYCIN.TM. drug), trace
elements (defined as inorganic compounds usually present at final
concentrations in the micromolar range), and glucose or an
equivalent energy source. Any other necessary supplements may also
be included at appropriate concentrations that would be known to
those skilled in the art. The culture conditions, such as
temperature, pH, and the like, are those previously used with the
host cell selected for expression, and will be apparent to the
ordinarily skilled artisan.
[0197] (ix) Antibody Purification
[0198] When using recombinant techniques, the antibody variant can
be produced intracellularly, in the periplasmic space, or directly
secreted into the medium. If the antibody variant is produced
intracellularly, as a first step, the particulate debris, either
host cells or lysed fragments, is removed, for example, by
centrifugation or ultrafiltration. Carter et al., Bio/Technology
10:163-167 (1992) describe a procedure for isolating antibodies
which are secreted to the periplasmic space of E. coli. Briefly,
cell paste is thawed in the presence of sodium acetate (pH 3.5),
EDTA, and phenylmethylsulfonylfluoride (PMSF) over about 30 min.
Cell debris can be removed by centrifugation. Where the antibody
variant is secreted into the medium, supernatants from such
expression systems are generally first concentrated using a
commercially available protein concentration filter, for example,
an Amicon or Millipore Pellicon ultrafiltration unit. A protease
inhibitor such as PMSF may be included in any of the foregoing
steps to inhibit proteolysis and antibiotics may be included to
prevent the growth of adventitious contaminants.
[0199] The antibody composition prepared from the cells can be
purified using, for example, hydroxylapatite chromatography, gel
electrophoresis, dialysis, and affinity chromatography, with
affinity chromatography being the preferred purification technique.
The suitability of protein A as an affinity ligand depends on the
species and isotype of any immunoglobulin Fc domain that is present
in the antibody variant. Protein A can be used to purify antibodies
that are based on human .gamma.1, .gamma.2, or .gamma.4 heavy
chains (Lindmark et al., J. Immunol. Meth. 62:1-13 (1983)). Protein
G is recommended for all mouse isotypes and for human .gamma.3
(Guss et al., EMBO J. 5:15671575 (1986)). The matrix to which the
affinity ligand is attached is most often agarose, but other
matrices are available. Mechanically stable matrices such as
controlled pore glass or poly(styrenedivinyl)benzene allow for
faster flow rates and shorter processing times than can be achieved
with agarose. Where the antibody variant comprises a C.sub.H3
domain, the Bakerbond ABX.TM.resin (J. T. Baker, Phillipsburg,
N.J.) is useful for purification. Other techniques for protein
purification such as fractionation on an ion-exchange column,
ethanol precipitation, Reverse Phase HPLC, chromatography on
silica, chromatography on heparin SEPHAROSEI chromatography on an
anion or cation exchange resin (such as a polyaspartic acid
column), chromatofocusing, SDS-PAGE, and ammonium sulfate
precipitation are also available depending on the antibody variant
to be recovered.
[0200] C. Pharmaceutical Formulations
[0201] Therapeutic formulations of the antibody variant are
prepared for storage by mixing the antibody variant having the
desired degree of purity with optional physiologically acceptable
carriers, excipients or stabilizers (Remington's Pharmaceutical
Sciences 16th edition, Osol, A. Ed. (1980)), in the form of
lyophilized formulations or aqueous solutions. Acceptable carriers,
excipients, or stabilizers are nontoxic to recipients at the
dosages and concentrations employed, and include buffers such as
phosphate, citrate, and other organic acids; antioxidants including
ascorbic acid and methionine; preservatives (such as
octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride;
benzalkonium chloride, benzethonium chloride; phenol, butyl or
benzyl alcohol; alkyl parabens such as methyl or propyl paraben;
catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low
molecular weight (less than about 10 residues) polypeptide;
proteins, such as serum albumin, gelatin, or immunoglobulins;
hydrophilic polymers such as polyvinylpyrrolidone; amino acids such
as glycine, glutamine, asparagine, histidine, arginine, or lysine;
monosaccharides, disaccharides, and other carbohydrates including
glucose, mannose, or dextrins; chelating agents such as EDTA;
sugars such as sucrose, mannitol, trehalose or sorbitol;
salt-forming counter-ions such as sodium; metal complexes (e.g.,
Zn-protein complexes); and/or non-ionic surfactants such as
TWEEN.TM., PLURONICS.TM. or polyethylene glycol (PEG).
[0202] The formulation herein may also contain more than one active
compound as necessary for the particular indication being treated,
preferably those with complementary activities that do not
adversely affect each other. For example, it may be desirable to
further provide an immunosuppressive agent. Such molecules are
suitably present in combination in amounts that are effective for
the purpose intended.
[0203] The active ingredients may also be entrapped in microcapsule
prepared, for example, by coacervation techniques or by interfacial
polymerization, for example, hydroxymethylcellulose or
gelatin-microcapsule and poly-(methylmethacylate) microcapsule,
respectively, in colloidal drug delivery systems (for example,
liposomes, albumin microspheres, microemulsions, nano-particles and
nanocapsules) or in macroemulsions. Such techniques are disclosed
in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed.
(1980).
[0204] The formulations to be used for in vivo administration must
be sterile. This is readily accomplished by filtration through
sterile filtration membranes.
[0205] Sustained-release preparations may be prepared. Suitable
examples of sustained-release preparations include semipermeable
matrices of solid hydrophobic polymers containing the antibody
variant, which matrices are in the form of shaped articles, e.g.,
films, or microcapsule. Examples of sustained-release matrices
include polyesters, hydrogels (for example,
poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)),
polylactides (U.S. Pat. No. 3,773,919), copolymers of L-glutamic
acid and ethyl-L-glutamate, non-degradable ethylene-vinyl acetate,
degradable lactic acid-glycolic acid copolymers such as the LUPRON
DEPOT.TM. (injectable microspheres composed of lactic acid-glycolic
acid copolymer and leuprolide acetate), and
poly-D-(-)-3-hydroxybutyric acid. While polymers such as
ethylene-vinyl acetate and lactic acid-glycolic acid enable release
of molecules for over 100 days, certain hydrogels release proteins
for shorter time periods. When encapsulated antibodies remain in
the body for a long time, they may denature or aggregate as a
result of exposure to moisture at 37.degree. C., resulting in a
loss of biological activity and possible changes in immunogenicity.
Rational strategies can be devised for stabilization depending on
the mechanism involved. For example, if the aggregation mechanism
is discovered to be intermolecular S--S bond formation through
thio-disulfide interchange, stabilization may be achieved by
modifying sulfhydryl residues, lyophilizing from acidic solutions,
controlling moisture content, using appropriate additives, and
developing specific polymer matrix compositions.
[0206] D. Non-Therapeutic Uses for the Antibody Variant
[0207] The antibody variants of the invention may be used as
affinity purification agents. In this process, the antibodies are
immobilized on a solid phase such a Sephadex resin or filter paper,
using methods well known in the art. The immobilized antibody
variant is contacted with a sample containing the antigen to be
purified, and thereafter the support is washed with a suitable
solvent that will remove substantially all the material in the
sample except the antigen to be purified, which is bound to the
immobilized antibody variant. Finally, the support is washed with
another suitable solvent, such as glycine buffer, pH 5.0, that will
release the antigen from the antibody variant.
[0208] The variant antibodies may also be useful in diagnostic
assays, e.g., for detecting expression of an antigen of interest in
specific cells, tissues, or serum.
[0209] For diagnostic applications, the antibody variant typically
will be labeled with a detectable moiety. Numerous labels are
available which can be generally grouped into the following
categories:
[0210] (a) Radioisotopes, such as .sup.35S, .sup.14C, .sup.125I,
.sup.3H, and .sup.131I. The antibody variant can be labeled with
the radioisotope using the techniques described in Current
Protocols in Immunology, Volumes 1 and 2, Coligen et al., Ed.
Wiley-Interscience, New York, N.Y., Pubs. (1991) for example and
radioactivity can be measured using scintillation counting.
[0211] (b) Fluorescent labels such as rare earth chelates (europium
chelates) or fluorescein and its derivatives, rhodamine and its
derivatives, dansyl, Lissamine, phycoerythrin and Texas Red are
available. The fluorescent labels can be conjugated to the antibody
variant using the techniques disclosed in Current Protocols in
Immunology, supra, for example. Fluorescence can be quantified
using a fluorimeter.
[0212] (c) Various enzyme-substrate labels are available and U.S.
Pat. No. 4,275,149 provides a review of some of these. The enzyme
generally catalyzes a chemical alteration of the chromogenic
substrate which can be measured using various techniques. For
example, the enzyme may catalyze a color change in a substrate,
which can be measured spectrophotometrically. Alternatively, the
enzyme may alter the fluorescence or chemiluminescence of the
substrate. Techniques for quantifying a change in fluorescence are
described above. The chemiluminescent substrate becomes
electronically excited by a chemical reaction and may then emit
light which can be measured (using a chemiluminometer, for example)
or donates energy to a fluorescent acceptor. Examples of enzymatic
labels include luciferases (e.g., firefly luciferase and bacterial
luciferase; U.S. Pat. No. 4,737,456), luciferin,
2,3-dihydrophthalazinediones, malate dehydrogenase, urease,
peroxidase such as horseradish peroxidase (HRPO), alkaline
phosphatase, beta-galactosidase, glucoamylase, lysozyme, saccharide
oxidases (e.g., glucose oxidase, galactose oxidase, and
glucose-6-phosphate dehydrogenase), heterocyclic oxidases (such as
uricase and xanthine oxidase), lactoperoxidase, microperoxidase,
and the like. Techniques for conjugating enzymes to antibodies are
described in O'Sullivan et al., Methods for the Preparation of
Enzyme-Antibody Conjugates for use in Enzyme Immunoassay, in
Methods in Enzym. (ed J. Langone & H. Van Vunakis), Academic
press, New York, 73:147-166 (1981).
[0213] Examples of enzyme-substrate combinations include, for
example:
[0214] (i) Horseradish peroxidase (HRPO) with hydrogen peroxidase
as a substrate, wherein the hydrogen peroxidase oxidizes a dye
precursor (e.g., orthophenylene diamine (OPD) or
3,3',5,5'-tetramethyl benzidine hydrochloride (TMB));
[0215] (ii) alkaline phosphatase (AP) with para-Nitrophenyl
phosphate as chromogenic substrate; and
[0216] (iii) beta-D-galactosidase (beta-D-Gal) with a chromogenic
substrate (e.g., p-nitrophenyl-beta-D-galactosidase) or fluorogenic
substrate 4-methylumbelliferyl-beta-D-galactosidase.
[0217] Numerous other enzyme-substrate combinations are available
to those skilled in the art. For a general review of these, see
U.S. Pat. Nos. 4,275,149 and 4,318,980.
[0218] Sometimes, the label is indirectly conjugated with the
antibody variant. The skilled artisan will be aware of various
techniques for achieving this. For example, the antibody variant
can be conjugated with biotin and any of the three broad categories
of labels mentioned above can be conjugated with avidin, or vice
versa. Biotin binds selectively to avidin and thus, the label can
be conjugated with the antibody variant in this indirect manner.
Alternatively, to achieve indirect conjugation of the label with
the antibody variant, the antibody variant is conjugated with a
small hapten (e.g., digoxin) and one of the different types of
labels mentioned above is conjugated with an anti-hapten antibody
variant (e.g., anti-digoxin antibody). Thus, indirect conjugation
of the label with the antibody variant can be achieved.
[0219] In another embodiment of the invention, the antibody variant
need not be labeled, and the presence thereof can be detected using
a labeled antibody which binds to the antibody variant.
[0220] The antibodies of the present invention may be employed in
any known assay method, such as competitive binding assays, direct
and indirect sandwich assays, and immunoprecipitation assays. Zola,
Monoclonal Antibodies: A Manual of Techniques, pp. 147-158 (CRC
Press, Inc. 1987).
[0221] Competitive binding assays rely on the ability of a labeled
standard to compete with the test sample analyze for binding with a
limited amount of antibody variant. The amount of antigen in the
test sample is inversely proportional to the amount of standard
that becomes bound to the antibodies. To facilitate determining the
amount of standard that becomes bound, the antibodies generally are
insolubilized before or after the competition, so that the standard
and analyze that are bound to the antibodies may conveniently be
separated from the standard and analyze which remain unbound.
[0222] Sandwich assays involve the use of two antibodies, each
capable of binding to a different immunogenic portion, or epitope,
of the protein to be detected. In a sandwich assay, the test sample
analyze is bound by a first antibody which is immobilized on a
solid support, and thereafter a second antibody binds to the
analyze, thus forming an insoluble three-part complex. See, e.g.,
U.S. Pat. No. 4,376,110. The second antibody may itself be labeled
with a detectable moiety (direct sandwich assays) or may be
measured using an anti-immunoglobulin antibody that is labeled with
a detectable moiety (indirect sandwich assay). For example, one
type of sandwich assay is an ELISA assay, in which case the
detectable moiety is an enzyme.
[0223] For immunohistochemistry, the tumor sample may be fresh or
frozen or may be embedded in paraffin and fixed with a preservative
such as formalin, for example.
[0224] The antibodies may also be used for in vivo diagnostic
assays. Generally, the antibody variant is labeled with a
radionuclide (such as .sup.111In, .sup.99Tc, .sup.14C, .sup.131I,
.sup.125I, .sup.3H, .sup.32P or .sup.35S) so that the tumor can be
localized using immunoscintiography.
[0225] E. Diagnostic Kits
[0226] As a matter of convenience, the antibody variant of the
present invention can be provided in a kit, i.e., a packaged
combination of reagents in predetermined amounts with instructions
for performing the diagnostic assay. Where the antibody variant is
labeled with an enzyme, the kit will include substrates and
cofactors required by the enzyme (e.g., a substrate precursor which
provides the detectable chromophore or fluorophore). In addition,
other additives may be included such as stabilizers, buffers (e.g.,
a block buffer or lysis buffer) and the like. The relative amounts
of the various reagents may be varied widely to provide for
concentrations in solution of the reagents which substantially
optimize the sensitivity of the assay. Particularly, the reagents
may be provided as dry powders, usually lyophilized, including
excipients which on dissolution will provide a reagent solution
having the appropriate concentration.
[0227] F. In Vivo Uses for the Antibody Variant
[0228] For therapeutic applications, the antibody variants of the
invention are administered to a mammal, preferably a human, in a
pharmaceutically acceptable dosage form such as those discussed
above, including those that may be administered to a human
intravenously as a bolus or by continuous infusion over a period of
time, by intramuscular, intraperitoneal, intra-cerebrospinal,
subcutaneous, intra-articular, intrasynovial, intrathecal, oral,
topical, or inhalation routes. The antibodies also are suitably
administered by intra-tumoral, peri-tumoral, intra-lesional, or
peri-lesional routes, to exert local as well as systemic
therapeutic effects. The intra-peritoneal route is expected to be
particularly useful, for example, in the treatment of ovarian
tumors. In addition, the antibody variant is suitably administered
by pulse infusion, particularly with declining doses of the
antibody variant. Preferably the dosing is given by injections,
most preferably intravenous or subcutaneous injections, depending
in part on whether the administration is brief or chronic.
[0229] For the prevention or treatment of disease, the appropriate
dosage of antibody variant will depend on the type of disease to be
treated, the severity and course of the disease, whether the
antibody variant is administered for preventive or therapeutic
purposes, previous therapy, the patient's clinical history and
response to the antibody variant, and the discretion of the
attending physician. The antibody variant is suitably administered
to the patient at one time or over a series of treatments.
[0230] The example herein concerns an anti-VEGF antibody. Anti-VEGF
antibodies are useful in the treatment of various neoplastic and
non-neoplastic diseases and disorders. Neoplasms and related
conditions that are amenable to treatment include breast
carcinomas, lung carcinomas, gastric carcinomas, esophageal
carcinomas, colorectal carcinomas, liver carcinomas, ovarian
carcinomas, thecomas, arrhenoblastomas, cervical carcinomas,
endometrial carcinoma, endometrial hyperplasia, endometriosis,
fibrosarcomas, choriocarcinoma, head and neck cancer,
nasopharyngeal carcinoma, laryngeal carcinomas, hepatoblastoma,
Kaposi's sarcoma, melanoma, skin carcinomas, hemangioma, cavernous
hemangioma, hemangioblastoma, pancreas carcinomas, retinoblastoma,
astrocytoma, glioblastoma, Schwannoma, oligodendroglioma,
medulloblastoma, neuroblastomas, rhabdomyosarcoma, osteogenic
sarcoma, leiomyosarcomas, urinary tract carcinomas, thyroid
carcinomas, Wilm's tumor, renal cell carcinoma, prostate carcinoma,
abnormal vascular proliferation associated with phakomatoses, edema
(such as that associated with brain tumors), and Meigs'
syndrome.
[0231] Non-neoplastic conditions that are amenable to treatment
include rheumatoid arthritis, psoriasis, atherosclerosis, diabetic
and other proliferative retinopathies including retinopathy of
prematurity, retrolental fibroplasia, neovascular glaucoma,
age-related macular degeneration, thyroid hyperplasias (including
Grave's disease), corneal and other tissue transplantation, chronic
inflammation, lung inflammation, nephrotic syndrome, preeclampsia,
ascites, pericardial effusion (such as that associated with
pericarditis), and pleural effusion.
[0232] Age-related macular degeneration (AMD) is a leading cause of
severe visual loss in the elderly population. The exudative form of
AMD is characterized by choroidal neovascularization and retinal
pigment epithelial cell detachment. Because choroidal
neovascularization is associated with a dramatic worsening in
prognosis, the VEGF antibodies of the present invention are
expected to be especially useful in reducing the severity of
AMD.
[0233] Depending on the type and severity of the disease, about 1
.mu.g/kg to 15 mg/kg (e.g., 0.1-20 mg/kg) of antibody variant is an
initial candidate dosage for administration to the patient,
whether, for example, by one or more separate administrations, or
by continuous infusion. A typical daily dosage might range from
about 1 .mu.g/kg to 100 mg/kg or more, depending on the factors
mentioned above. For repeated administrations over several days or
longer, depending on the condition, the treatment is sustained
until a desired suppression of disease symptoms occurs. However,
other dosage regimens may be useful. The progress of this therapy
is easily monitored by conventional techniques and assays.
[0234] The antibody variant composition will be formulated, dosed,
and administered in a fashion consistent with good medical
practice. Factors for consideration in this context include the
particular disorder being treated, the particular mammal being
treated, the clinical condition of the individual patient, the
cause of the disorder, the site of delivery of the agent, the
method of administration, the scheduling of administration, and
other factors known to medical practitioners. The "therapeutically
effective amount" of the antibody variant to be administered will
be governed by such considerations, and is the minimum amount
necessary to prevent, ameliorate, or treat a disease or disorder.
The antibody variant need not be, but is optionally formulated with
one or more agents currently used to prevent or treat the disorder
in question. The effective amount of such other agents depends on
the amount of antibody variant present in the formulation, the type
of disorder or treatment, and other factors discussed above. These
are generally used in the same dosages and with administration
routes as used hereinbefore or about from 1 to 99% of the
heretofore employed dosages.
[0235] G. Articles of Manufacture
[0236] In another embodiment of the invention, an article of
manufacture containing materials useful for the treatment of the
disorders described above is provided. The article of manufacture
comprises a container and a label. Suitable containers include, for
example, bottles, vials, syringes, and test tubes. The containers
may be formed from a variety of materials such as glass or plastic.
The container holds a composition which is effective for treating
the condition and may have a sterile access port (for example the
container may be an intravenous solution bag or a vial having a
stopper pierceable by a hypodermic injection needle). The active
agent in the composition is the antibody variant. The label on, or
associated with, the container indicates that the composition is
used for treating the condition of choice. The article of
manufacture may further comprise a second container comprising a
pharmaceutically-acceptable buffer, such as phosphate-buffered
saline, Ringer's solution and dextrose solution. It may further
include other materials desirable from a commercial and user
standpoint, including other buffers, diluents, filters, needles,
syringes, and package inserts with instructions for use.
Example 1
[0237] In this example, antibody variants containing randomized
peptide inserts within the antibody CDRs are prepared by phage
display which substantially improve the affinity of a humanized Fab
for VEGF. Crystallography suggests that these changes result in an
increased contact area with antigen.
[0238] VEGF:Fab X-ray Co-Crystal Structure: A crystal structure of
the complex between the VEGF antigen and anti-VEGF parent antibody
was prepared as described in Muller et al., Structure
6(9):1153-1167 (1998). The conclusion that the three VH CDRs are
the main determinants of Fab binding to VEGF is supported by the
high-resolution crystal structure of the VEGF:Fab (v36) complex. In
addition, the major energetic determinants largely coincide with
the principal contacting residues of the Fab in the complex.
[0239] Several randomized libraries were designed with a peptide
insertion placed in the antigen-contacting CDRs which, from the
crystal structure, were expected to increase the potential contact
between the antibody and the antigen.
[0240] Design of CDR Random Loop-Insertion Libraries: Based upon
inspection of the VEGF:Fab crystal structure, it was postulated
that additional contacts, contributing additional binding energy
between the Fab and VEGF, could be generated through the addition
of peptide inserts within one or more CDRs of the Fab. Because the
nature and relative contributions of such additional interactions
would be difficult to predict, randomized loop sequences (Xn) were
directly inserted into each of the four CDRs proximal to the
existing VEGF binding site using NNS codons, and a frameshifted Fab
vector as template. The length of loop was chosen based upon
distances in the crystal structure between exit/entry points of the
loop on the hypervariable region and possible interaction sites on
the surface of VEGF. In addition, one or more residues within each
loop were deleted in some of these templates, as judged necessary
to accommodate the new peptide loop.
[0241] Three such loops were designed for VH1, including insertions
of 4, 5, or 6 residues between Y27 and T28. In VH2, two inserted
peptides of 3 or 4 residues were placed between Y54 and T55. Also
in VH2, a 6-residue random peptide was used to replace residues T55
and H56. In VH3, a 4-residue or 5-residue peptide was used to
replace G104, and a 5-residue or 6-residue peptide was used to
replace residues G104 and S105. Finally, in VL3, a random peptide
of either 4 or 6 residues was inserted between S92 and T93.
[0242] Second-Generation Selections of anti-VEGF Libraries:
Templates for random mutagenesis were constructed starting from the
Fab-g3 phagemid pY0192 (WO98/45331) and frameshift oligonucleotides
(which prevent expression of a functional template Fab): YC-82,
YC-85, YC-89, YC-92, YC-94, and YC-97 (Table 1).
TABLE-US-00001 TABLE 1 Frameshift oligos for CDR-insert template
mutagenesis Oligo SEQ. # Region Sequence ID NO: YC-82 VL3 C TGT CAA
CAG TAT AGC T ACC SEQ. ID GTG CCG TGG ACG NO: 1 YC-85 VH1 GCA GCT
TCT GGC TAT G ACC SEQ. ID TTC ACC AAC TAT G NO: 2 YC-89 VH2 GA TGG
ATT AAC ACC TAT G ACC SEQ. ID GGT GAA CCG ACC NO: 3 YC-92 VH2 GA
TGG ATT AAC ACC TAT T GAA SEQ. ID CCG ACC TAT GCT G NO: 4 YC-94 VH3
G TAC CCG CAC TAT TAT G AGC SEQ. ID AGC CAC TGG TAT TTC NO: 5 YC-97
VH3 G TAC CCG CAC TAT TAT G AGC SEQ. ID CAC TGG TAT TTC NO: 6
[0243] The corresponding randomization oligonucleotides (which
employ NNS at the sites targeted for randomization) were YC-83,
YC-84 in VL3; YC-86, YC-87, YC-88 in VH1; YC-90, YC91 and YC-93 in
VH2; and YC-95, YC-96, YC-98, YC-99 in VH3. See Table 2 below.
TABLE-US-00002 TABLE 2 Random oligos for CDR-insert library
constructions Oligo # Region (Comments) Sequence SEQ ID NO: YC-83
VL3 (insert 4 C TGT CAA CAG TAT AGC NNS NNS NNS SEQ. ID residues)
NNS ACC GTG CCG TGG ACG NO: 7 YC-84 VL3 (insert 6 C TGT CAA CAG TAT
AGC NNS NNS NNS SEQ. ID residues) NNS NNS NNS ACC GTG CCG TGG ACG
NO: 8 YC-86 VH1 (insert 4 GCA GCT TCT GGC TAT NNS NNS NNS SEQ. ID
residues) NNS ACC TTC ACC AAC TAT G NO: 9 YC-87 VH1 (insert 5 GCA
GCT TCT GGC TAT NNS NNS NNS SEQ. ID residues) NNS NNS ACC TTC ACC
AAC TAT G NO: 10 YC-88 VH1 (insert 6 GCA GCT TCT GGC TAT NNS NNS
NNS SEQ. ID residues) NNS NNS NNS ACC TTC ACC AAC TAT G NO: 11
YC-90 VH2 (insert 3 GA TGG ATT AAC ACC TAT NNS NNS NNS SEQ. ID
residues) ACC GGT GAA CCG ACC NO: 12 YC-91 VH2 (insert 4 GA TGG ATT
AAC ACC TAT NNS NNS NNS SEQ. ID residues) NNS ACC GGT GAA CCG ACC
NO: 13 YC-93 VH2 (insert 6 GA TGG ATT AAC ACC TAT NNS NNS NNS SEQ.
ID residues) NNS NNS NNS GAA CCG ACC TAT GCT G NO: 14 YC-95 VH3
(insert 4 G TAC CCG CAC TAT TAT NNS NNS NNS SEQ. ID residues) NNS
AGC AGC CAC TGG TAT TTC NO: 15 YC-96 VH3 (insert 5 G TAC CCG CAC
TAT TAT NNS NNS NNS SEQ. ID residues) NNS NNS AGC AGC CAC TGG TAT
TTC NO: 16 YC-98 VH3 (insert 5 G TAC CCG CAC TAT TAT NNS NNS NNS
SEQ. ID residues) NNS NNS AGC CAC TGG TAT TTC NO: 17 YC-99 VH3
(insert 6 G TAC CCG CAC TAT TAT NNS NNS NNS SEQ. ID residues) NNS
NNS NNS AGC CAC TGG TAT TTC NO: 18
[0244] The resulting transformants yielded libraries with
complexities ranging from 6.times.10.sup.7 to 5.times.10.sup.8
suggesting that the libraries were comprehensive in covering all
possible variants.
[0245] Each library was sorted separately for the first round;
thereafter, libraries with the same site of insertion were combined
and sorted together as one. Therefore, library YC-83 was combined
with library YC-84; library YC-86 with libraries YC-87 and YC-88;
library YC-90 with YC-91; library YC-95 with YC-96; and library
YC-98 with YC-99. These libraries were sorted essentially as
described in WO98/45331, except the incubation with PBS/TWEEN
20.RTM. buffer after phage binding was carried out as described in
Table 3.
TABLE-US-00003 TABLE 3 Conditions for secondary selections of Fab
variants round of incubation time incubation selection (hr)
incubation solution temp. (.degree. C.) 1 0 0 room temp. 2 1 ELISA
buffer room temp. 3 2 1 .mu.M VEGF/ELISA room temp. 4 18 1 .mu.M
VEGF/ELISA room temp. 5 37 1 .mu.M VEGF/ELISA room temp. 6 17
hr@R.T./30 h@ same as above room temp./ 37.degree. C. 37.degree. C.
7 63 same as above 37.degree. C. 8 121 same as above 37.degree.
C.
[0246] ELISA buffer contained 0.5% bovine serum albumin and 0.05%
TWEEN 20.RTM. in PBS. VEGF was included in the incubation buffer to
minimize rebinding of phage to VEGF coated on the surface of the
plate.
[0247] Sorting of some of these libraries yielded VEGF-binding
phage enrichments over 5 to 8 rounds of selection. After five to
eight rounds of selections, ten to twenty clones from each library
were isolated from carbenicillin containing plates harboring E.
coli (XL1) colonies which had been infected with an eluted phage
pool. Colonies were isolated and grown with helper phage to obtain
single-stranded DNA for sequencing. Clones were picked from those
libraries that enriched for DNA sequencing. The results are shown
in Table 4. Libraries showing no enrichment were not sequenced.
TABLE-US-00004 TABLE 4 Summary of CDR Insertion Libraries No. of
added Oligos Site of residues Stop oligo Insert oligo CDR Insertion
Net Total YC-85 YC-86 H1 Y27{circumflex over ( )}T28 4 4 YC-85
YC-87 H1 Y27{circumflex over ( )}T28 5 5 YC-85 YC-88 H1
Y27{circumflex over ( )}T28 6 6 YC-89 YC-90 H2 Y54{circumflex over
( )}T55 3 3 YC-89 YC-91 H2 Y54{circumflex over ( )}T55 4 4 YC-92
YC-93 H2 Y54{circumflex over ( )}E57 4 6 YC-94 YC-95 H3
Y103{circumflex over ( )}S105 3 4 YC-94 YC-96 H3 Y103{circumflex
over ( )}S105 4 5 YC-97 YC-98 H3 Y103{circumflex over ( )}S106 3 5
YC-97 YC-99 H3 Y103{circumflex over ( )}S106 4 6 YC-82 YC-83 L3
S92{circumflex over ( )}T93 4 4 YC-82 YC-84 L3 S92{circumflex over
( )}T93 6 6
[0248] For VH1, only library YC-86 showed enrichment. Sequencing
revealed that, although a 4-residue insert was designed in this
library, all of the sequenced clones contained no net insertion,
but instead point mutations at T28 and F29. This suggests that this
antibody is relatively intolerant of insertions in this
hypervariable region.
[0249] A similar result was seen for the VH2 libraries, where only
library YC-90 showed enrichment. Again, clones found were either
wild-type (Y0192) or a point mutant, Y54W. This suggests that this
antibody is also relatively intolerant of insertions in the VH2
CDR.
[0250] Again, a similar result was obtained for the VL3 libraries.
In this case, only library YC-83 showed enrichment, and the
selected clones had point mutations at T93 and/or V94, rather than
the designed insertion. This suggests that this antibody is also
relatively intolerant of insertions in the VL3 CDR.
[0251] In contrast, two VH3 libraries showed enrichment: YC-95 and
YC-98. Moreover, sequencing of selected clones showed that the Fab
variants indeed contained insertion sequences.
[0252] Amino acid sequences of anti-VEGF variants from the various
libraries are shown in Tables 5-15 below. The sequence of the
randomized region only is shown as deduced from DNA sequencing.
Sites where randomized inserted sequences were made are shown in
bold. An asterisk denotes a contaminating phagemid from another
library.
TABLE-US-00005 TABLE 5 Protein sequences of anti-VEGF variants from
library YC-86 Round 7 (VEGF eluted phage) VH1 sequence (# clones/
Name (residues 26-35) SEQ ID NO: 10) Y0241-1 GYDFTNYGIN SEQ. ID NO:
19 4 Y0241-6 GYDYTNYGIN SEQ. ID NO: 20 3 Y0241-7 GYDWTNYGIN SEQ. ID
NO: 21 3
TABLE-US-00006 TABLE 6 Protein sequences of anti-VEGF variants from
library YC-90 Round 7 (VEGF eluted phage) VH2 sequence (# clones/
Name (residues 50-62) SEQ ID NO: 10) Y0242-1 WINTWTGEPTYAA SEQ. ID
NO: 22 4 *Y0192 6
TABLE-US-00007 TABLE 7 Protein sequences of anti-VEGF variants from
library YC-83 Round 7 (VEGF eluted phage) VH3 sequence (# clones/
Name (residues 89-97) SEQ ID NO: 9) Y0241-2 QQYSATPWT SEQ. ID NO:
23 1 Y0241-3 QQYSNVPWT SEQ. ID NO: 24 3 Y0241-4 QQYSAVPWT SEQ. ID
NO: 25 4 Y0241-5 QQYSSVPWT SEQ. ID NO: 26 1
TABLE-US-00008 TABLE 8 Protein sequences of anti-VEGF variants from
library YC-95 Round 5 (VEGF eluted phage) VH3 sequence (# (residues
99-111) + clones/ Name insertions SEQ ID NO: 10) Y0228-1
YPHYYAKERSSHWYFDV SEQ. ID NO: 27 1 Y0228-2 YPHYYVGETSSHWYFDV SEQ.
ID NO: 28 1 Y0228-3 YPHYYARDRSSHWYFDV SEQ. ID NO: 29 1 Y0228-4
YPHYYERDGKSSHWYFDV SEQ. ID NO: 30 1 Y0228-5 YPHYYRNEKSSHWYFDV SEQ.
ID NO: 31 1 Y0228-6 YPHYYVGEQSSHWYFDV SEQ. ID NO: 32 1 Y0228-7
YPHYYQRDRSSHWYFDV SEQ. ID NO: 33 1 Y0228-8 YPHYYQKQSKSSHWYFDV SEQ.
ID NO: 34 1 Y0228-9 YPHYYQNEGPSSHWYFDV SEQ. ID NO: 35 1 Y0228-10
YPHYYGNHRSSHWYFDV SEQ. ID NO: 36 1
TABLE-US-00009 TABLE 9 Protein sequences of anti-VEGF variants from
library YC-95 Round 5 (HCl eluted phage) VH3 sequence (# (residues
99-111) + clones/ Name insertions SEQ ID NO: 10) Y0229-1
YPHYYRTEKSSHWYFDV SEQ. ID NO: 37 1 Y0229-2 YPHYYLKDRSSHWYFDV SEQ.
ID NO: 38 1 Y0229-4 YPHYYQDEKSSHWYFDV SEQ. ID NO: 39 1 Y0229-5
YPHYYVGEKSSHWYFDV SEQ. ID NO: 40 1 Y0229-6 YPHYYRDERSSHWYFDV SEQ.
ID NO: 41 1 Y0229-7 YPHYYTYDKSSHWYFDV SEQ. ID NO: 42 1 Y0229-8
YPHYYHTRGGSSHWYFDV SEQ. ID NO: 43 1 Y0229-9 YPHYYLNDKSSHWYFDV SEQ.
ID NO: 44 1 Y0229-10 YPHYYYRDRSSHWYFDV SEQ. ID NO: 45 1 *Y0239-1
1
TABLE-US-00010 TABLE 10 Protein sequences of anti-VEGF variants
from library YC-95 Round 7 (HCl eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0239-1
YPHYYRNERSSHWYFDV SEQ. ID NO: 46 1 Y0239-2 YPHYYKNDKSSHWYFDV SEQ.
ID NO: 47 1 Y0239-3 YPHYYLADRSSHWYFDV SEQ. ID NO: 48 1 Y0239-4
YPHYYVNERSSHWYFDV SEQ. ID NO: 49 1 Y0239-5 YPHYYLKDKSSHWYFDV SEQ.
ID NO: 50 1 Y0239-6 YPHYYLKDGRSSHWYFDV SEQ. ID NO: 51 1 Y0239-7
YPHYYERDGRSSHWYFDV SEQ. ID NO: 52 1 Y0239-8 YPHYYLRDGRSSHWYFDV SEQ.
ID NO: 53 1 Y0239-9 YPHYYLGESSHWYFDV SEQ. ID NO: 54 1 Y0239-10
YPHYYLGEKSSHWYFDV SEQ. ID NO: 55 1
TABLE-US-00011 TABLE 11 Protein sequences of anti-VEGF variants
from library YC-95 Round 8 (HCl eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0261-1
YPHYYLKDRRSSHWYFDV SEQ. ID NO: 56 2 Y0261-2 YPHYYLKDGMSSHWYFDV SEQ.
ID NO: 57 2 *Y0239-4 1 *Y0239-9 5
TABLE-US-00012 TABLE 12 Protein sequences of anti-VEGF variants
from library YC-98 Round 5 (VEGF eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0228-11
YPHYYEKQRKSHWYFDV SEQ. ID NO: 58 1 Y0228-12 YPHYYKEDKKSHWYFDV SEQ.
ID NO: 59 1 Y0228-13 YPHYYSHQKRSHWYFDV SEQ. ID NO: 60 1 Y0228-14
YPHYYSGERESHWYFDV SEQ. ID NO: 61 1 Y0228-15 YPHYYQSEGRSHWYFDV SEQ.
ID NO: 62 1 Y0228-16 YPHYYSVEGGSHWYFDV SEQ. ID NO: 63 1 Y0228-17
YPHYYPSPRGSHWYFDV SEQ. ID NO: 64 1 Y0228-18 YPHYYQRNGKSHWYFDV SEQ.
ID NO: 65 1 Y0228-19 YPHYYAREGGSHWYFDV SEQ. ID NO: 66 1 Y0228-20
YPHYYSNERKSHWYFDV SEQ. ID NO: 67 1
TABLE-US-00013 TABLE 13 Protein sequences of anti-VEGF variants
from library YC-98 Round 5 (HCl eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0229-11
YPHYYRGDRKSHWYFDV SEQ. ID NO: 68 1 Y0229-12 YPHYYSDEKKSHWYFDV SEQ.
ID NO: 69 1 Y0229-13 YPHYYRSQRKSHWYFDV SEQ. ID NO: 70 1 Y0229-14
YPHYYAWRDRRSHWYFDV SEQ. ID NO: 71 1 Y0229-15 YPHYYANRERKSHWYFDV
SEQ. ID NO: 72 1 Y0229-16 YPHYYVNDKTSHWYFDV SEQ. ID NO: 73 1
Y0229-17 YPHYYVEETESHWYFDV SEQ. ID NO: 74 1 Y0229-18
YPHYYEKERKSHWYFDV SEQ. ID NO: 75 1 Y0229-19 YPHYYSHERVSHWYFDV SEQ.
ID NO: 76 1
TABLE-US-00014 TABLE 14 Protein sequences of anti-VEGF variants
from library YC-98 Round 7 (HCl eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0239-11
YPHYYRDERESHWYFDV SEQ. ID NO: 77 1 Y0239-12 YPHYYAHEKKSHWYFDV SEQ.
ID NO: 78 1 Y0239-13 YPHYYLKDRKSHWYFDV SEQ. ID NO: 79 1 Y0239-14
YPHYYQHDRTSHWYFDV SEQ. ID NO: 80 1 Y0239-15 YPHYYVTDRKSHWYFDV SEQ.
ID NO: 81 1 Y0239-16 YPHYYLRDKKSHWYFDV SEQ. ID NO: 82 1 Y0239-17
YPHYYSHERKSHWYFDV SEQ. ID NO: 83 1 Y0239-18 YPHYYLNERKSHWYFDV SEQ.
ID NO: 84 1 Y0239-19 YPHYYVNERKSHWYFDV SEQ. ID NO: 85 2 Y0240-1
YPHYYLTDHKSHWYFDV SEQ. ID NO: 86 1
TABLE-US-00015 TABLE 15 Protein sequences of anti-VEGF variants
from library YC-98 Round 8 (HCl eluted phage) VH3 sequence (#
(residues 99-111) + clones/ Name insertions SEQ ID NO: 10) Y0261-4
YPHYYLKDGKKSHWYFDV SEQ. ID NO: 87 1 Y0261-5 YPHYYRRDKKSHWYFDV SEQ.
ID NO: 88 1 Y0261-6 YPHYYLKDKKSHWYFDV SEQ. ID NO: 89 1 Y0261-7
YPHYYLHDRKSHWYFDV SEQ. ID NO: 90 1 Y0261-8 YPHYYLSDKKSHWYFDV SEQ.
ID NO: 91 1 Y0239-19 YPHYYVNERKSHWYFDV SEQ. ID NO: 92 1 *Y0230- 1
13 *Y0230- 3 16
[0253] In order to quantify relative antigen-binding affinities,
several anti-VEGF variants' DNA were transformed into E. coli
strain 34B8, expressed as Fab, and purified by passing the
periplasmic shockate through a protein G column (Pharmacia) as
described in WO98/45331.
[0254] CDR combination Variant Y0313-2: An attempt was made to
improve antigen binding affinity by combining a previously
discovered CDR VH2 mutation with an insertion variant described
here. A mutagenic oligonucleotide, YC-107 (Table 16) was used to
combine insertion mutations found in CDR VH3, from clone Y0239-19,
with VH2 CDR mutations T28D/N31H from clone Y0243-1 (WO98/45331) of
CDR VH2.
TABLE-US-00016 TABLE 16 Mutagenesis oligo for adding a CDR
insertion peptide Oligo # Region (Comments) Sequence SEQ. ID NO:
YC-107 VH3 (insert VNERK TAC CCG CAC TAT TAT SEQ. ID NO: 93 from
library GTG AAC GAG CGG AAG YC-98) AGC CAC TGG TAT TTC
[0255] The resulting combined CDR variant was designated Y0313-2. A
Fab protein sample was prepared as described above for BIACORE.TM.
analysis.
[0256] BIACORE.TM. Analysis: The VEGF-binding affinities of Fab
fragments were calculated from association and dissociation rate
constants measured using a BIACORE.TM.-2000 surface plasmon
resonance system (BIACORE.TM., Inc., Piscataway, N.J.). A biosensor
chip was activated for covalent coupling of VEGF using
N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)
and N-hydroxysuccinimide (NHS) according to the supplier's
(BIACORE.TM., Inc., Piscataway, N.J.) instructions. VEGF(8-109) was
buffered exchanged into 20 mM sodium acetate, pH 4.8 and diluted to
approximately 50 .mu.g/mL. Aliquots of VEGF were injected at a flow
rate of 2 .mu.L/min to achieve approximately 700-1400 response
units (RU) of coupled protein. A solution of 1 M ethanolamine was
injected as a blocking agent.
[0257] For kinetics measurements, two-fold serial dilutions of Fab
were injected in PBS/TWEEN buffer (0.05% TWEEN 20.TM. in phosphate
buffered saline) at 25.degree. C. at a flow rate of 10 .mu.L/min.
Equilibrium dissociation constants, Kd's from SPR measurements were
calculated as koff/kon (Table 17).
TABLE-US-00017 TABLE 17 Kinetics of Fab-VEGF binding from BIACORE
.TM. measurements. Variant Kon(10.sup.4/M/s) koff(10.sup.-4/s)
Kd(nM) Kd(wt)/Kd(mut) Y0192 4.1 1.21 2.9 -1- Y0241-4 4.4 1.41 3.2
0.9 Y0241-7 4.6 1.28 3.0 1.0 Y0241-6 4.7 1.29 2.7 1.1 Y0242-1 4.7
0.86 1.8 1.6 Y0239-19 3.6 0.10 0.30 9.7 Y0239-8 3.8 0.18 0.50 5.8
Y0240-1 2.5 0.13 0.50 5.8 Y0239-2 3.6 1.64 4.6 0.6 Y0239-12 5.7
0.34 0.6 4.8 Y0239-9 3.97 0.19 0.5 6.0 Y0261-6 4.4 0.25 0.6 5.0
Y0313-2 3.11 0.11 0.36 8.0
[0258] Results of SPR measurements demonstrated that affinity is
mainly enhanced through a slower dissociation rate (as opposed to
faster association).
[0259] For the insertion variant Y0239-19, an approximately 10-fold
improvement in binding affinity was observed (Table 17). However,
addition of the VH1 mutations did not further improve affinity, as
indicated for the variant Y0313-2.
[0260] Cell-Based Assay of VEGF: Two Fab variants of the anti-VEGF
antibody were tested for their ability to antagonize VEGF
(recombinant; version 1-165) in induction of the growth of HuVECs
(human umbilical vein endothelial cells). The alamar blue assay (H.
Gazzano-Santoro, et al. J Immunol Methods 202:163-171 (1997)) was
used to measure the metabolic activity of cells in response to
VEGF.
[0261] Two Fab variants of the anti-VEGF antibody were tested for
their ability to antagonize VEGF (recombinant; version 1-165)
activity in induction of the growth of HuVECs (human umbilical vein
endothelial cells). HuVEC cells are seeded (1500/well) in a 96 well
microtiter plate in complete medium (Cell Systems, Kirkland, Wash.)
that has been coated with Cell Systems attachment factor. The cells
are allowed to attach for 24 hrs. On day 2, VEGF and Fab are
diluted in assay medium (DMEM/F12 +pennicillin/streptomycin, 0.1%
gelatin). For the antibody experiments, a constant concentration of
5 ng/ml VEGF is added to all the wells followed by the addition of
various concentrations of anti-VEGF Fab (approximately 10 .mu.g/ml
and dilutions). The VEGF and Fab incubate with the HUVEC cells for
2 days, after which 25 .mu.l of alamar blue is added. Following a 4
hr incubation period, fluorescence is read on a Cytoflour
Fluorescence Plate reader. The media used for these assays is from
Cell Systems.
[0262] The results (FIG. 2) show that the insertion variant Y0313-2
Fab has roughly 100-fold enhanced potency over the original
humanized antibody, F(ab)-12.
[0263] Crystallization and X-Ray Structure Determination of the
Insert-Fab Y0313-2 in complex with VEGF: Crystals of VEGF in
complex with the Fab fragment Y0313-2 were grown at room
temperature by vapor diffusion using the hanging drop method.
Crystallization buffer containing 0.1 M sodium chloride, 20 mM Tris
at pH 7.5, and the VEGF:Fab complex at a concentration of 8 mg/ml
was mixed with an equal amount of reservoir solution (15% PEG 4000,
5% isopropanol, 0.1 M MES, pH 6.0, 0.2 M Citrate, 0.2 M Ammonium
sulfate and 1 mM SPADNS
(2-(p-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulphonic
acid)). The resulting crystals belong to the monoclinic space group
P2 with cell parameters of a=107.6 .ANG., b=65.8 .ANG., c=123.8
.ANG., and .beta.=93.4.degree. and contain one VEGF-dimer bound to
two Fab fragments in the asymmetric unit.
[0264] Prior to flash cooling with liquid nitrogen, crystals were
dipped into artificial mother liquor containing 20% glycerol. One
diffraction data set was collected from a single crystal at 100 K
on a CCD detector at the Advanced Light Source (Berkeley, Calif.).
The data were processed using MOSFLM (Leslie, A MOSFLM Users Guide,
MRC-LMB, Cambridge (1994)) and programs of the CCP4 suite
(Collaborative Computing Project No. 4 Acta Crystallog. sect. D,
50: 760-763 (1994)). The final data set was of good quality
(Rsym=7.4%) with a completeness of 94.5% for all reflections
between 25 .ANG. and 2.8 .ANG. resolution.
[0265] Initial phases for the complex were obtained by molecular
replacement, using the constant domains and the variable domains of
the Fab fragment F(ab)-12 as separate search models. A model of the
receptor binding domain of VEGF could be placed unambiguously in a
resulting difference density map.
[0266] Refinement of the model with program X-PLOR (Bruenger et al.
Science 235: 458-460.(1987)) resulted in a final R-value of 21.2%
with an R-free of 26.6% using all data between 2.8 .ANG. and 25
.ANG..
[0267] New Antibody-Antigen Contacts in the Insert-Fab Complex with
VEGF: The results of x-ray crystallography show that the
introduction of the insert (Asn 104a, Glu 104b and Arg 104c (note:
numbering of Y0313-2 residues is sequential with inserted residues
given a letter, rather than according to Kabat et al., supra)
together with the two substitutions (G104V and S105K) enclosing it,
increases the total amount of buried surface in the interface
between VEGF and the antibody by about 20% (see FIG. 4), as
compared with the structure of the F(ab)-12 complex (Muller et al.,
Structure 6(9):1153-1167 (1998)). The main contributors for the
enlargement of the contact area are residues Val 104 and Arg 104c.
Together, these two residues account for additional 220 .ANG..sup.2
of buried surface on the Fab fragment. The side chain of Val 104 is
packing tightly against the main chain of residues 93 to 95 of
VEGF. The newly introduced Arg 104c forms a charged interaction
with the carboxyl group of Asp 41 of VEGF and is also in contact
with the phenyl ring of Tyr 39 (see FIG. 5). Minor contributions to
the interface are made by the side chain of Lys 105 which is in the
vicinity of the VEGF residues Glu 44 and Tyr 45. The side chains of
residues Asn 104a and Glu 104b are pointing away from the interface
and neither of them contributes significantly to the interface
between the Fab fragment and VEGF.
Sequence CWU 1
1
99132DNAartificial sequencesequence is synthesized 1ctgtcaacag
tatagctacc gtgccgtgga cg 32232DNAartificial sequencesequence is
synthesized 2gcagcttctg gctatgacct tcaccaacta tg 32333DNAartificial
sequencesequence is synthesized 3gatggattaa cacctatgac cggtgaaccg
acc 33434DNAartificial sequencesequence is synthesized 4gatggattaa
cacctattga accgacctat gctg 34535DNAartificial sequencesequence is
synthesized 5gtacccgcac tattatgagc agccactggt atttc
35632DNAartificial sequencesequence is synthesized 6gtacccgcac
tattatgagc cactggtatt tc 32743DNAartificial sequencesequence is
synthesized 7ctgtcaacag tatagcnnsn nsnnsnnsac cgtgccgtgg acg
43849DNAartificial sequencesequence is synthesized 8ctgtcaacag
tatagcnnsn nsnnsnnsnn snnsaccgtg ccgtggacg 49943DNAartificial
sequencesequence is synthesized 9gcagcttctg gctatnnsnn snnsnnsacc
ttcaccaact atg 431046DNAartificial sequencesequence is synthesized
10gcagcttctg gctatnnsnn snnsnnsnns accttcacca actatg
461149DNAartificial sequencesequence is synthesized 11gcagcttctg
gctatnnsnn snnsnnsnns nnsaccttca ccaactatg 491241DNAartificial
sequencesequence is synthesized 12gatggattaa cacctatnns nnsnnsaccg
gtgaaccgac c 411344DNAartificial sequencesequence is synthesized
13gatggattaa cacctatnns nnsnnsnnsa ccggtgaacc gacc
441451DNAartificial sequencesequence is synthesized 14gatggattaa
cacctatnns nnsnnsnnsn nsnnsgaacc gacctatgct 50g 511546DNAartificial
sequencesequence is synthesized 15gtacccgcac tattatnnsn nsnnsnnsag
cagccactgg tatttc 461646DNAartificial sequencesequence is
synthesized 16gtacccgcac tattatnnsn nsnnsnnsag cagccactgg tatttc
461746DNAartificial sequencesequence is synthesized 17gtacccgcac
tattatnnsn nsnnsnnsnn sagccactgg tatttc 461849DNAartificial
sequencesequence is synthesized 18gtacccgcac tattatnnsn nsnnsnnsnn
snnsagccac tggtatttc 491910PRTartificial sequencesequence is
synthesized 19Gly Tyr Asp Phe Thr Asn Tyr Gly Ile Asn1 5
102010PRTartificial sequencesequence is synthesized 20Gly Tyr Asp
Tyr Thr Asn Tyr Gly Ile Asn1 5 102110PRTartificial sequencesequence
is synthesized 21Gly Tyr Asp Trp Thr Asn Tyr Gly Ile Asn1 5
102213PRTartificial sequencesequence is synthesized 22Trp Ile Asn
Thr Trp Thr Gly Glu Pro Thr Tyr Ala Ala1 5 10239PRTartificial
sequencesequence is synthesized 23Gln Gln Tyr Ser Ala Thr Pro Trp
Thr1 5249PRTartificial sequencesequence is synthesized 24Gln Gln
Tyr Ser Asn Val Pro Trp Thr1 5259PRTartificial sequencesequence is
synthesized 25Gln Gln Tyr Ser Ala Val Pro Trp Thr1
5269PRTartificial sequencesequence is synthesized 26Gln Gln Tyr Ser
Ser Val Pro Trp Thr1 52717PRTartificial sequencesequence is
synthesized 27Tyr Pro His Tyr Tyr Ala Lys Glu Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val2817PRTartificial sequencesequence is
synthesized 28Tyr Pro His Tyr Tyr Val Gly Glu Thr Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val2917PRTartificial sequencesequence is
synthesized 29Tyr Pro His Tyr Tyr Ala Arg Asp Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3018PRTartificial sequencesequence is
synthesized 30Tyr Pro His Tyr Tyr Glu Arg Asp Gly Lys Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val3117PRTartificial sequencesequence is
synthesized 31Tyr Pro His Tyr Tyr Arg Asn Glu Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3217PRTartificial sequencesequence is
synthesized 32Tyr Pro His Tyr Tyr Val Gly Glu Gln Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3317PRTArtificial Sequencesequence is
synthesized 33Tyr Pro His Tyr Tyr Gln Arg Asp Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3418PRTartificial sequencesequence is
synthesized 34Tyr Pro His Tyr Tyr Gln Lys Gln Ser Lys Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val3518PRTartificial sequencesequence is
synthesized 35Tyr Pro His Tyr Tyr Gln Asn Glu Gly Pro Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val3617PRTartificial sequencesequence is
synthesized 36Tyr Pro His Tyr Tyr Gly Asn His Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3717PRTartificial sequencesequence is
synthesized 37Tyr Pro His Tyr Tyr Arg Thr Glu Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3817PRTartificial sequencesequence is
synthesized 38Tyr Pro His Tyr Tyr Leu Lys Asp Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val3917PRTartificial sequencesequence is
synthesized 39Tyr Pro His Tyr Tyr Gln Asp Glu Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4017PRTartificial sequencesequence is
synthesized 40Tyr Pro His Tyr Tyr Val Gly Glu Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4117PRTartificial sequencesequence is
synthesized 41Tyr Pro His Tyr Tyr Arg Asp Glu Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4217PRTartificial sequencesequence is
synthesized 42Tyr Pro His Tyr Tyr Thr Tyr Asp Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4318PRTartificial sequencesequence is
synthesized 43Tyr Pro His Tyr Tyr His Thr Arg Gly Gly Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val4417PRTartificial sequencesequence is
synthesized 44Tyr Pro His Tyr Tyr Leu Asn Asp Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4517PRTartificial sequencesequence is
synthesized 45Tyr Pro His Tyr Tyr Tyr Arg Asp Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4617PRTartificial sequencesequence is
synthesized 46Tyr Pro His Tyr Tyr Arg Asn Glu Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4717PRTartificial sequencesequence is
synthesized 47Tyr Pro His Tyr Tyr Lys Asn Asp Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4817PRTartificial sequencesequence is
synthesized 48Tyr Pro His Tyr Tyr Leu Ala Asp Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val4917PRTartificial sequencesequence is
synthesized 49Tyr Pro His Tyr Tyr Val Asn Glu Arg Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val5017PRTArtificial Sequencesequence is
synthesized 50Tyr Pro His Tyr Tyr Leu Lys Asp Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val5118PRTartificial sequencesequence is
synthesized 51Tyr Pro His Tyr Tyr Leu Lys Asp Gly Arg Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val5218PRTartificial sequencesequence is
synthesized 52Tyr Pro His Tyr Tyr Glu Arg Asp Gly Arg Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val5318PRTartificial sequencesequence is
synthesized 53Tyr Pro His Tyr Tyr Leu Arg Asp Gly Arg Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val5416PRTartificial sequencesequence is
synthesized 54Tyr Pro His Tyr Tyr Leu Gly Glu Ser Ser His Trp Tyr
Phe Asp1 5 10 15Val5517PRTartificial sequencesequence is
synthesized 55Tyr Pro His Tyr Tyr Leu Gly Glu Lys Ser Ser His Trp
Tyr Phe1 5 10 15Asp Val5618PRTartificial sequencesequence is
synthesized 56Tyr Pro His Tyr Tyr Leu Lys Asp Arg Arg Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val5718PRTartificial sequencesequence is
synthesized 57Tyr Pro His Tyr Tyr Leu Lys Asp Gly Met Ser Ser His
Trp Tyr1 5 10 15Phe Asp Val5817PRTartificial sequencesequence is
synthesized 58Tyr Pro His Tyr Tyr Glu Lys Gln Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val5917PRTartificial sequencesequence is
synthesized 59Tyr Pro His Tyr Tyr Lys Glu Asp Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val6017PRTartificial sequencesequence is
synthesized 60Tyr Pro His Tyr Tyr Ser His Gln Lys Arg Ser His Trp
Tyr Phe1 5 10 15Asp Val6117PRTartificial sequencesequence is
synthesized 61Tyr Pro His Tyr Tyr Ser Gly Glu Arg Glu Ser His Trp
Tyr Phe1 5 10 15Asp Val6217PRTartificial sequencesequence is
synthesized 62Tyr Pro His Tyr Tyr Gln Ser Glu Gly Arg Ser His Trp
Tyr Phe1 5 10 15Asp Val6317PRTartificial sequencesequence is
synthesized 63Tyr Pro His Tyr Tyr Ser Val Glu Gly Gly Ser His Trp
Tyr Phe1 5 10 15Asp Val6417PRTartificial sequencesequence is
synthesized 64Tyr Pro His Tyr Tyr Pro Ser Pro Arg Gly Ser His Trp
Tyr Phe1 5 10 15Asp Val6517PRTartificial sequencesequence is
synthesized 65Tyr Pro His Tyr Tyr Gln Arg Asn Gly Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val6617PRTartificial sequencesequence is
synthesized 66Tyr Pro His Tyr Tyr Ala Arg Glu Gly Gly Ser His Trp
Tyr Phe1 5 10 15Asp Val6717PRTartificial sequencesequence is
synthesized 67Tyr Pro His Tyr Tyr Ser Asn Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val6817PRTartificial sequencesequence is
synthesized 68Tyr Pro His Tyr Tyr Arg Gly Asp Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val6917PRTartificial sequencesequence is
synthesized 69Tyr Pro His Tyr Tyr Ser Asp Glu Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val7017PRTartificial sequencesequence is
synthesized 70Tyr Pro His Tyr Tyr Arg Ser Gln Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val7118PRTartificial sequencesequence is
synthesized 71Tyr Pro His Tyr Tyr Ala Trp Arg Asp Arg Arg Ser His
Trp Tyr1 5 10 15Phe Asp Val7218PRTartificial sequencesequence is
synthesized 72Tyr Pro His Tyr Tyr Ala Asn Arg Glu Arg Lys Ser His
Trp Tyr1 5 10 15Phe Asp Val7317PRTartificial sequencesequence is
synthesized 73Tyr Pro His Tyr Tyr Val Asn Asp Lys Thr Ser His Trp
Tyr Phe1 5 10 15Asp Val7417PRTartificial sequencesequence is
synthesized 74Tyr Pro His Tyr Tyr Val Glu Glu Thr Glu Ser His Trp
Tyr Phe1 5 10 15Asp Val7517PRTartificial sequencesequence is
synthesized 75Tyr Pro His Tyr Tyr Glu Lys Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val7617PRTartificial sequencesequence is
synthesized 76Tyr Pro His Tyr Tyr Ser His Glu Arg Val Ser His Trp
Tyr Phe1 5 10 15Asp Val7717PRTartificial sequencesequence is
synthesized 77Tyr Pro His Tyr Tyr Arg Asp Glu Arg Glu Ser His Trp
Tyr Phe1 5 10 15Asp Val7817PRTartificial sequencesequence is
synthesized 78Tyr Pro His Tyr Tyr Ala His Glu Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val7917PRTartificial sequencesequence is
synthesized 79Tyr Pro His Tyr Tyr Leu Lys Asp Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8017PRTartificial sequencesequence is
synthesized 80Tyr Pro His Tyr Tyr Gln His Asp Arg Thr Ser His Trp
Tyr Phe1 5 10 15Asp Val8117PRTartificial sequencesequence is
synthesized 81Tyr Pro His Tyr Tyr Val Thr Asp Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8217PRTartificial sequencesequence is
synthesized 82Tyr Pro His Tyr Tyr Leu Arg Asp Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8317PRTartificial sequencesequence is
synthesized 83Tyr Pro His Tyr Tyr Ser His Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8417PRTartificial sequencesequence is
synthesized 84Tyr Pro His Tyr Tyr Leu Asn Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8517PRTartificial sequencesequence is
synthesized 85Tyr Pro His Tyr Tyr Val Asn Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8617PRTartificial sequencesequence is
synthesized 86Tyr Pro His Tyr Tyr Leu Thr Asp His Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8718PRTartificial sequencesequence is
synthesized 87Tyr Pro His Tyr Tyr Leu Lys Asp Gly Lys Lys Ser His
Trp Tyr1 5 10 15Phe Asp Val8817PRTartificial sequencesequence is
synthesized 88Tyr Pro His Tyr Tyr Arg Arg Asp Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val8917PRTartificial sequencesequence is
synthesized 89Tyr Pro His Tyr Tyr Leu Lys Asp Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val9017PRTartificial sequencesequence is
synthesized 90Tyr Pro His Tyr Tyr Leu His Asp Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val9117PRTartificial sequencesequence is
synthesized 91Tyr Pro His Tyr Tyr Leu Ser Asp Lys Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val9217PRTartificial sequencesequence is
synthesized 92Tyr Pro His Tyr Tyr Val Asn Glu Arg Lys Ser His Trp
Tyr Phe1 5 10 15Asp Val9345DNAartificial sequencesequence is
synthesized 93tacccgcact attatgtgaa cgagcggaag agccactggt atttc
4594110PRTartificial sequencesequence is synthesized 94Asp Ile Gln
Met Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Val1 5 10 15Gly Asp Arg
Val Thr Ile Thr Cys Ser Ala Ser Gln Asp Ile Ser 20 25 30Asn Tyr Leu
Asn Trp Tyr Gln Gln Lys Pro Gly Lys Ala Pro Lys 35 40 45Val Leu Ile
Tyr Phe Thr Ser Ser Leu His Ser Gly Val Pro Ser 50 55 60Arg Phe Ser
Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile 65 70 75Ser Ser Leu
Gln Pro Glu Asp Phe Ala Thr Tyr Tyr Cys Gln Gln 80 85 90Tyr Ser Thr
Val Pro Trp Thr Phe Gly Gln Gly Thr Lys Val Glu 95 100 105Ile Lys
Arg Thr Val 11095110PRTartificial sequencesequence is synthesized
95Asp Ile Gln Leu Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Val1 5 10
15Gly Asp Arg Val Thr Ile Thr Cys Arg Ala Asn Glu Gln Leu Ser 20 25
30Asn Tyr Leu Asn Trp Tyr Gln Gln Lys Pro Gly Lys Ala Pro Lys 35 40
45Val Leu Ile Tyr Phe Thr Ser Ser Leu His Ser Gly Val Pro Ser 50 55
60Arg Phe Ser Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile 65 70
75Ser Ser Leu Gln Pro Glu Asp Phe Ala Thr Tyr Tyr Cys Gln Gln 80 85
90Tyr Ser Thr Val Pro Trp Thr Phe Gly Gln Gly Thr Lys Val Glu 95
100 105Ile Lys Arg Thr Val 11096118PRTartificial sequencesequence
is synthesized 96Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val
Gln Pro Gly1 5 10 15Gly Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Tyr
Thr Phe Thr 20 25 30Asn Tyr Gly Met Asn Trp Val Arg Gln Ala Pro Gly
Lys Gly Leu 35 40 45Glu Trp Val Gly Trp Ile Asn Thr Tyr Thr Gly Glu
Pro Thr Tyr 50 55 60Ala Ala Asp Phe Lys Arg Arg Phe Thr Phe Ser Leu
Asp Thr Ser 65 70 75Lys Ser Thr Ala Tyr Leu Gln Met Asn Ser Leu Arg
Ala Glu Asp 80 85 90Thr Ala Val Tyr Tyr Cys Ala Lys Tyr
Pro His Tyr Tyr Gly Ser 95 100 105Ser His Trp Tyr Phe Asp Val Trp
Gly Gln Gly Thr Leu 110 11597118PRTartificial sequencesequence is
synthesized 97Glu Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln
Pro Gly1 5 10 15Gly Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Tyr Asp
Phe Thr 20 25 30His Tyr Gly Met Asn Trp Val Arg Gln Ala Pro Gly Lys
Gly Leu 35 40 45Glu Trp Val Gly Trp Ile Asn Thr Tyr Thr Gly Glu Pro
Thr Tyr 50 55 60Ala Ala Asp Phe Lys Arg Arg Phe Thr Phe Ser Leu Asp
Thr Ser 65 70 75Lys Ser Thr Ala Tyr Leu Gln Met Asn Ser Leu Arg Ala
Glu Asp 80 85 90Thr Ala Val Tyr Tyr Cys Ala Lys Tyr Pro His Tyr Tyr
Gly Ser 95 100 105Ser His Trp Tyr Phe Asp Val Trp Gly Gln Gly Thr
Leu 110 11598121PRTartificial sequencesequence is synthesized 98Glu
Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly1 5 10 15Gly
Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Tyr Thr Phe Thr 20 25 30Asn
Tyr Gly Met Asn Trp Val Arg Gln Ala Pro Gly Lys Gly Leu 35 40 45Glu
Trp Val Gly Trp Ile Asn Thr Tyr Thr Gly Glu Pro Thr Tyr 50 55 60Ala
Ala Asp Phe Lys Arg Arg Phe Thr Phe Ser Leu Asp Thr Ser 65 70 75Lys
Ser Thr Ala Tyr Leu Gln Met Asn Ser Leu Arg Ala Glu Asp 80 85 90Thr
Ala Val Tyr Tyr Cys Ala Lys Tyr Pro His Tyr Tyr Val Asn 95 100
105Glu Arg Lys Ser His Trp Tyr Phe Asp Val Trp Gly Gln Gly Thr 110
115 120Leu99121PRTartificial sequencesequence is synthesized 99Glu
Val Gln Leu Val Glu Ser Gly Gly Gly Leu Val Gln Pro Gly1 5 10 15Gly
Ser Leu Arg Leu Ser Cys Ala Ala Ser Gly Tyr Asp Phe Thr 20 25 30His
Tyr Gly Met Asn Trp Val Arg Gln Ala Pro Gly Lys Gly Leu 35 40 45Glu
Trp Val Gly Trp Ile Asn Thr Tyr Thr Gly Glu Pro Thr Tyr 50 55 60Ala
Ala Asp Phe Lys Arg Arg Phe Thr Phe Ser Leu Asp Thr Ser 65 70 75Lys
Ser Thr Ala Tyr Leu Gln Met Asn Ser Leu Arg Ala Glu Asp 80 85 90Thr
Ala Val Tyr Tyr Cys Ala Lys Tyr Pro His Tyr Tyr Val Asn 95 100
105Glu Arg Lys Ser His Trp Tyr Phe Asp Val Trp Gly Gln Gly Thr 110
115 120Leu
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