U.S. patent application number 09/863693 was filed with the patent office on 2002-05-23 for method for making multispecific antibodies having heteromultimeric and common components.
This patent application is currently assigned to Genentech, Inc.. Invention is credited to Arathoon, W. Robert, Carter, Paul J., Merchant, Anne M., Presta, Leonard G..
Application Number | 20020062010 09/863693 |
Document ID | / |
Family ID | 26724321 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020062010 |
Kind Code |
A1 |
Arathoon, W. Robert ; et
al. |
May 23, 2002 |
Method for making multispecific antibodies having heteromultimeric
and common components
Abstract
The invention relates to a method of preparing heteromultimeric
polypeptides such as bispecific antibodies, bispecific
immunoadhesins and antibody-immunoadhesin chimeras. The invention
also relates to the heteromultimers prepared using the method.
Generally, the method provides a multispecific antibody having a
common light chain associated with each heteromeric polypeptide
having an antibody binding domain. Additionally the method futher
involves introducing into the multispecific antibody a specific and
complementary interaction at the interface of a first polypeptide
and the interface of a second polypeptide, so as to promote
heteromultimer formation and hinder homomultimer formation; and/or
a free thiol-containing residue at the interface of a first
polypeptide and a corresponding free thiol-containing residue in
the interface of a second polypeptide, such that a non-naturally
occurring disulfide bond is formed between the first and second
polypeptide. The method allows for the enhanced formation of the
desired heteromultimer relative to undesired heteromultimers and
homomultimers.
Inventors: |
Arathoon, W. Robert; (San
Mateo, CA) ; Carter, Paul J.; (San Francisco, CA)
; Merchant, Anne M.; (San Bruno, CA) ; Presta,
Leonard G.; (San Francisco, CA) |
Correspondence
Address: |
GENENTECH, INC.
1 DNA WAY
SOUTH SAN FRANCISCO
CA
94080
US
|
Assignee: |
Genentech, Inc.
|
Family ID: |
26724321 |
Appl. No.: |
09/863693 |
Filed: |
May 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09863693 |
May 23, 2001 |
|
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09070166 |
Apr 30, 1998 |
|
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60046816 |
May 2, 1997 |
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Current U.S.
Class: |
530/388.1 ;
435/326; 435/69.1; 435/70.21 |
Current CPC
Class: |
C07K 2317/24 20130101;
C07K 16/2812 20130101; C07K 2317/622 20130101; C07K 2317/31
20130101; C07K 2319/00 20130101; C07K 16/2869 20130101; C07K 16/32
20130101; C07K 2317/52 20130101; C07K 16/00 20130101; C07K 2317/624
20130101; C07K 16/2809 20130101 |
Class at
Publication: |
530/388.1 ;
435/70.21; 435/69.1; 435/326 |
International
Class: |
C12P 021/02; C12P
021/04; C12N 005/06; C07K 016/00 |
Claims
What is claimed is:
1. A method of preparing a multispecific antibody comprising a
first polypeptide and at least one additional polypeptide, wherein
(a) the first polypeptide comprises a multimerization domain
forming an interface positioned to interact with an interface of a
multimerization domain of the additional polypeptide, (b) the first
and additional polypeptides each comprise a binding domain, the
binding domain comprising a heavy chain and a light chain, wherein
the variable light chains of the first and additional polypeptides
comprise a common sequence, the method comprising the steps of: (I)
culturing a host cell comprising nucleic acid encoding the first
polypeptide and additional polypeptide, and the variable light
chain, wherein the culturing is such that the nucleic acid is
expressed; and (ii) recovering the multispecific antibody from the
host cell culture.
2. The method of claim 1, wherein the nucleic acid encoding the
first polypeptide or the nucleic acid encoding the additional
polypeptide, or both, has been altered from the original nucleic
acid to encode the interface or a portion thereof.
3. The method of claim 2 wherein the multimerization domains of one
of the first or additional polypeptides, or both, are altered to
comprise a free thiol-containing residue which is positioned to
interact with a free thiol-containing residue of the interface of
the other of the first or additional polypeptide such that a
disulfide bond is formed between the first and additional
polypeptides, wherein the nucleic acid encoding the first
polypeptide has been altered from the original nucleic acid to
encode the free thiol-containing residue or the nucleic acid
encoding the additional polypeptide has been altered from the
original nucleic acid to encode the free thiol-containing residue,
or both.
4. The method of claim 1 wherein the multimerization domains of the
first and additional polypeptides comprise a
protuberance-into-cavity interaction, wherein the method further
comprises: generating a protuberance by altering the original
nucleic acid encoding the first polypeptide to encode an import
residue having a larger side chain volume than the original
residue, and generating a cavity by altering the original nucleic
acid encoding the additional polypeptide to encode an import
residue having a smaller side chain volume than the original
residue.
5. The method of claim 4, wherein the steps of generating a
protuberance or generating a cavity, or both, occurs by phage
display selection.
6. The method of claim 4 wherein the import residue having a larger
side chain volume than the original residue is selected from the
group consisting of arginine (R), phenylalanine (F), tyrosine (Y),
tryptophan (W), isoleucine (I) and leucine (L).
7. The method of claim 4 wherein the import residue having a
smaller side chain volume than the original residue is selected
from the group consisting of glycine (G), alanine (A), serine (S),
threonine (T), and valine (V), and wherein the import residue is
not cysteine (C).
8. The method of claim 1 wherein the first and additional
polypeptide each comprise an antibody constant domain.
9. The method of claims 8 wherein the first and additional
polypeptide each comprise an antibody constant domain selected from
the group consisting of a C.sub.H3 domain and an IgG.
10. The method of claim 1 wherein the heteromultimer is a
multispecific immunoadhesin.
11. The method of claim 1 wherein step (I) is preceded by a step
wherein the nucleic acid encoding the first and additional
polypeptide is introduced into the host cell.
12. A heteromultimer prepared by the method of claim 1.
13. A multispecific antibody comprising a first polypeptide and at
least one additional polypeptide which meet at an interface,
wherein (a) the first polypeptide comprises a multimerization
domain forming an interface positioned to interact with an
interface of a multimerization domain of the additional
polypeptide; and (b) the first and additional polypeptides each
comprise a binding domain, the binding domain comprising a variable
heavy chain and a variable light chain, wherein the variable light
chain of the first and additional polypeptides comprise a common
sequence.
14. The multispecific antibody of claim 13, wherein the nucleic
acid encoding the first polypeptide or the nucleic acid encoding
the additional polypeptide, or both, has been altered from the
original nucleic acid to encode the interface or a portion
thereof.
15. The multispecific antibody of claim 14 wherein the first
polypeptide interface comprises a free thiol-containing residue
which is positioned to interact with a free thiol-containing
residue of the interface of the additional polypeptide such that a
disulfide bond is formed between the first and additional
polypeptides, wherein the nucleic acid encoding the first
polypeptide has been altered from the original nucleic acid to
encode the free thiol-containing residue or the nucleic acid
encoding the additional polypeptide has been altered from the
original nucleic acid to encode the free thiol-containing residue,
or both.
16. The multispecific antibody of claim 14 wherein the interface of
the multimerization domains of the first and an additional
polypeptide comprise a protuberance and cavity, respectively.
17. The multispecific antibody of claim 16 wherein the protuberance
and cavity are generated by alterations in which naturally
occurring amino acids are imported into the first and additional
polypeptides.
18. A composition comprising the multispecific antibody of claim 13
and a carrier.
19. A host cell comprising nucleic acid encoding the heteromultimer
of claim 13.
20. The host cell of claim 19 wherein the host cell is a mammalian
cell.
21. A method of preparing a multispecific antibody comprising: (a)
selecting a first nucleic acid encoding a first polypeptide
comprising an amino acid residue in the interface of the first
polypeptide is replaced with an amino acid residue on an additional
polypeptide, and selecting at least one additional nucleic acid
encoding at least one additional polypeptide so that the amino acid
residue on the additional polypeptide specifically interacts with
the amino acid residue on the first polypeptide, thereby generating
a stable interaction between the first and additional polypeptides;
(b) selecting a light chain encoding nucleic acid sequence, wherein
the light chain is meant to associate with the binding region of
each first and additional polypeptide of the multispecific
antibody; (c) introducing into a host cell the first and additional
nucleic acids and the light chain-encoding nucleic acid, and
culturing the cell so that expression of the first and additional
nucleic acids and the light chain-encoding nucleic acid occurs to
form the bispecifc antibody; (d) recovering the multispecific
antibody from the cell culture.
22. The method of claim 21, wherein at least one of the first and
additional nucleic acids of step (a) are altered from the original
nucleic acid to encode an amino acid in the interface that
interacts with an amino acid of the first or additional amino acid
residue thereby generating the stable interaction.
23. The method of claim 22 wherein the altering comprises
generating a protuberance-into-cavity interaction at the interface
between the first and additional polypeptides.
24. The method of claim 22 wherein the alterating comprises
importing a free thiol-containing residue into the first or
additional polypeptide or both, such that the free thiol-containg
residues interact to form a disulfide bond between the first and
additional polypeptides.
25. The method of claim 21 wherein the first and additional
polypeptide each comprise an antibody constant domain.
26. The method of claim 25 wherein the antibody constant domain is
a C.sub.H3 domain.
27. The method of claim 26 wherein the antibody constant domain is
from a human IgG.
28. A method of measuring the formation of a heteromultimeric
multispecific antibody comprising a first and at least one
additional polypeptide from a mixture of polypeptides, wherein (a)
the first and additional polypeptides meet at an interface of a
multimerization domain of each of the first and additional
polypeptides, (b) the interface of the first polypeptide comprises
a free thiol-containing residue which is positioned to interact
with a free thiol-containing residue of the interface of the
additional polypeptide such that a disulfide bond is formed, the
method comprising the steps of: (i) causing each of the
multispecific antibodies to migrate in a gel matrix; and (ii)
determining the relative amount of a band corresponding to the
multispecific antibody having a non-naturally occurring disulfide
bond between the first and additional polypeptides, and a slower
migrating band corresponding to a heteromultimer lacking
non-naturally occurring disulfide bonds between the first and
additional polypeptide.
29. The method of claim 28 wherein the multimerization domains
encode a protuberance-into-cavity interation at the interface,
thereby promoting a specific interaction between the first and
additional polypeptides.
Description
RELATED APPLICATIONS
[0001] This application is a non-provisional application filed
under 37 CFR 1.53(b) (1), claiming priority under 35 USC 119(e) to
provisional application No. 60/046,816, filed May 2, 1997 the
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a method for making multispecific
antibodies having heteromultimeric heavy chain components and
common light chain components such as bispecific antibodies,
bispecific immunoadhesins, as well as antibody-immunoadhesin
chimeras and the heteromultimeric polypeptides made using the
method.
BACKGROUND OF THE INVENTION
[0003] Bispecific Antibodies
[0004] Bispecific antibodies (BsAbs) which have binding
specificities for at least two different antigens have significant
potential in a wide range of clinical applications as targeting
agents for in vitro and in vivo immunodiagnosis and therapy, and
for diagnostic immunoassays.
[0005] In the diagnostic areas, bispecific antibodies have been
very useful in probing the functional properties of cell surface
molecules and in defining the ability of the different Fc receptors
to mediate cytotoxicity (Fanger et al., Crit. Rev. Immunol.
12:101-124 (1992)). Nolan et al., Biochem. Biophys. Acta. 1040:1-11
(1990) describe other diagnostic applications for BsAbs. In
particular, BsAbs can be constructed to immobilize enzymes for use
in enzyme immunoassays. To achieve this, one arm of the BsAb can be
designed to bind to a specific epitope on the enzyme so that
binding does not cause enzyme inhibition, the other arm of the BsAb
binds to the immobilizing matrix ensuring a high enzyme density at
the desired site. Examples of such diagnostic BsAbs include the
rabbit anti-IgG/anti-ferritin BsAb described by Hammerling et al.,
J. Exp. Med. 128:1461-1473 (1968) which was used to locate surface
antigens. BsAbs having binding specificities for horse radish
peroxidase (HRP) as well as a hormone have also been developed.
Another potential immunochemical application for BsAbs involves
their use in two-site immunoassays. For example, two BsAbs are
produced binding to two separate epitopes on the analyte
protein--one BsAb binds the complex to an insoluble matrix, the
other binds an indicator enzyme (see Nolan et al., supra).
[0006] Bispecific antibodies can also be used for in vitro or in
vivo immunodiagnosis of various diseases such as cancer
(Songsivilai et al., Clin. Exp. Immunol. 79:315 (1990)). To
facilitate this diagnostic use of the BsAb, one arm of the BsAb can
bind a tumor associated antigen and the other arm can bind a
detectable marker such as a chelator which tightly binds a
radionuclide. Using this approach, Le Doussal et al. made a BsAb
useful for radioimmunodetection of colorectal and thryoid
carcinomas which had one arm which bound a carcinoembryonic antigen
(CEA) and another arm which bound diethylenetriaminepentacetic acid
(DPTA). See Le Doussal et al., Int. J. Cancer Suppl. 7:58-62 (1992)
and Le Doussal et al., J. Nucl. Med. 34:1662-1671 (1993). Stickney
et al. similarly describe a strategy for detecting colorectal
cancers expressing CEA using radioimmunodetection. These
investigators describe a BsAb which binds CEA as well as
hydroxyethylthiourea-benzyl-EDTA (EOTUBE). See Stickney et al.,
Cancer Res. 51:6650-6655 (1991).
[0007] Bispecific antibodies can also be used for human therapy in
redirected cytotoxicity by providing one arm which binds a target
(e.g. pathogen or tumor cell) and another arm which binds a
cytotoxic trigger molecule, such as the T-cell receptor or the
Fc.gamma. receptor. Accordingly, bispecific antibodies can be used
to direct a patient's cellular immune defense mechanisms
specifically to the tumor cell or infectious agent. Using this
strategy, it has been demonstrated that bispecific antibodies which
bind to the Fc.gamma.RIII (i.e. CD16) can mediate tumor cell
killing by natural killer (NK) cell/large granular lymphocyte (LGL)
cells in vitro and are effective in preventing tumor growth in
vivo. Segal et al., Chem. Immunol. 47:179 (1989) and Segal et al.,
Biologic Therapy of Cancer 2(4) DeVita et al. eds. J. B.
Lippincott, Philadelphia (1992) p. 1. Similarly, a bispecific
antibody having one arm which binds Fc.gamma.RIII and another which
binds to the HER2 receptor has been developed for therapy of
ovarian and breast tumors that overexpress the HER2 antigen.
(Hseih-Ma et al. Cancer Research 52:6832-6839 (1992) and Weiner et
al. Cancer Research 53:94-100 (1993)). Bispecific antibodies can
also mediate killing by T cells. Normally, the bispecific
antibodies link the CD3 complex on T cells to a tumor-associated
antigen. A fully humanized F(ab').sub.2 BsAb consisting of anti-CD3
linked to anti-p185.sup.HER2 has been used to target T cells to
kill tumor cells overexpressing the HER2 receptor. Shalaby et al.,
J. Exp. Med. 175(1):217 (1992). Bispecific antibodies have been
tested in several early phase clinical trials with encouraging
results. In one trial, 12 patients with lung, ovarian or breast
cancer were treated with infusions of activated T-lymphocytes
targeted with an anti-CD3/anti-tumor (MOC31) bispecific antibody.
deLeij et al. Bispecific Antibodies and Targeted Cellular
Cytotoxicity, Romet-Lemonne, Fanger and Segal Eds., Lienhart (1991)
p. 249. The targeted cells induced considerable local lysis of
tumor cells, a mild inflammatory reaction, but no toxic side
effects or anti-mouse antibody responses. In a very preliminary
trial of an anti-CD3/anti-CD19 bispecific antibody in a patient
with B-cell malignancy, significant reduction in peripheral tumor
cell counts was also achieved. Clark et al. Bispecific Antibodies
and Targeted Cellular Cytotoxicity, Romet-Lemonne, Fanger and Segal
Eds., Lienhart (1991) p. 243. See also Kroesen et al., Cancer
Immunol. Immunother. 37:400-407 (1993), Kroesen et al., Br. J.
Cancer 70:652-661 (1994) and Weiner et al., J. Immunol. 152:2385
(1994) concerning therapeutic applications for BsAbs.
[0008] Bispecific antibodies may also be used as fibrinolytic
agents or vaccine adjuvants. Furthermore, these antibodies may be
used in the treatment of infectious diseases (e.g. for targeting of
effector cells to virally infected cells such as HIV or influenza
virus or protozoa such as Toxoplasma gondii), used to deliver
immunotoxins to tumor cells, or target immune complexes to cell
surface receptors (see Fanger et al., supra).
[0009] Use of BsAbs has been effectively hindered by the difficulty
of obtaining BsAbs in sufficient quantity and purity.
Traditionally, bispecific antibodies were made using
hybrid-hybridoma technology (Millstein and Cuello, 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 (see FIG. 1A).
The purification of the correct molecule, which is usually done by
affinity chromatography steps, is rather cumbersome, and the
product yields are low. See, for example, (Smith, W., et al. (1992)
Hybridoma 4:87-98; and Massimo, Y. S., et al. (1997) J. Immunol.
Methods 201:57-66). Accordingly, techniques for the production of
greater yields of BsAb have been developed. To achieve chemical
coupling of antibody fragments, 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 BsAb. The BsAbs
produced can be used as agents for the selective immobilization of
enzymes.
[0010] 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
BsAb F(ab').sub.2 molecule having one arm which binds p185.sup.HER2
and another arm which binds CD3. Each Fab' fragment was separately
secreted from E. coli. and subjected to directed chemical coupling
in vitro to form the BsAb. The BsAb thus formed was able to bind to
cells overexpressing the HER2 receptor and normal human T cells, as
well as trigger the lytic activity of human cytotoxic lymphocytes
against human breast tumor targets. See also Rodrigues et al., Int.
J. Cancers (Suppl.) 7:45-50 (1992).
[0011] Various techniques for making and isolating BsAb fragments
directly from recombinant cell cultures have also been described.
For example, bispecific F(ab').sub.2 heterodimers 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 anti-CD3 and
anti-interleukin-2 receptor (IL-2R) antibodies by gene fusion. The
antibody homodimers were reduced at the hinge region to form
monomers and then reoxidized to form the antibody heterodimers. The
BsAbs were found to be highly effective in recruiting cytotoxic T
cells to lyse HuT-102 cells in vitro. The advent of the "diabody"
technology described by Hollinger et al., PNAS (USA) 90:6444-6448
(1993) has provided an alternative mechanism for making BsAb
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 BsAb fragments
by the use of single chain Fv (sFv) dimers has also been reported.
See Gruber et al. J. Immunol. 152: 5368 (1994). These researchers
designed an antibody which comprised the V.sub.H and V.sub.L
domains of an antibody directed against the T cell receptor joined
by a 25 amino acid residue linker to the V.sub.H and V.sub.L
domains of an anti-fluorescein antibody. The refolded molecule
bound to fluorescein and the T cell receptor and redirected the
lysis of human tumor cells that had fluorescein covalently linked
to their surface.
[0012] It is apparent that several techniques for making bispecific
antibody fragments which can be recovered directly from recombinant
cell culture have been reported. However, full length BsAbs may be
preferable to BsAb fragments for many clinical applications because
of their likely longer serum half-life and possible effector
functions.
[0013] Immunoadhesins
[0014] Immunoadhesins (Ia's) are antibody-like molecules which
combine the binding domain of a protein such as a cell-surface
receptor or a ligand (an "adhesin") with the effector functions of
an immunoglobulin constant domain. Immunoadhesins can possess many
of the valuable chemical and biological properties of human
antibodies. Since immunoadhesins can be constructed from a human
protein sequence with a desired specificity linked to an
appropriate human immunoglobulin hinge and constant domain (Fc)
sequence, the binding specificity of interest can be achieved using
entirely human components. Such immunoadhesins are minimally
immunogenic to the patient, and are safe for chronic or repeated
use.
[0015] Immunoadhesins reported in the literature include fusions of
the T cell receptor (Gascoigne et al., Proc. Natl. Acad. Sci. USA
84:2936-2940 (1987)); CD4 (Capon et al., Nature 337:525-531 (1989);
Traunecker et al., Nature 339:68-70 (1989); Zettmeissl et al., DNA
Cell Biol. USA 9:347-353 (1990); and Byrn et al., Nature
344:667-670 (1990)); L-selectin or homing receptor (Watson et al.,
J. Cell. Biol. 110:2221-2229 (1990); and Watson et al., Nature
349:164-167 (1991)); CD44 (Aruffo et al., Cell 61:1303-1313
(1990)); CD28 and B7 (Linsley et al., J. Exp. Med. 173:721-730
(1991)); CTLA-4 (Lisley et al., J. Exp. Med. 174:561-569 (1991));
CD22 (Stamenkovic et al., Cell 66:1133-1144 (1991)); TNF receptor
(Ashkenazi et al., Proc. Natl. Acad. Sci. USA 88:10535-10539
(1991); Lesslauer et al., Eur. J. Immunol. 27:2883-2886 (1991); and
Peppel et al., J. Exp. Med. 174:1483-1489 (1991)); NP receptors
(Bennett et al., J. Biol. Chem. 266:23060-23067 (1991)); inteferon
.gamma. receptor (Kurschner et al., J. Biol. Chem. 267:9354-9360
(1992)); 4-1BB (Chalupny et al., PNAS (USA) 89:10360-10364 (1992))
and IgE receptor .alpha. (Ridgway and Gorman, J. Cell. Biol. Vol.
115, Abstract No. 1448 (1991)).
[0016] Examples of immunoadhesins which have been described for
therapeutic use include the CD4-IgG immunoadhesin for blocking the
binding of HIV to cell-surface CD4. Data obtained from Phase I
clinical trials in which CD4-IgG was administered to pregnant women
just before delivery suggests that this immunoadhesin may be useful
in the prevention of maternal-fetal transfer of HIV. Ashkenazi et
al., Intern. Rev. Immunol. 10:219-227 (1993). An immunoadhesin
which binds tumor necrosis factor (TNF) has also been developed.
TNF is a proinflammatory cytokine which has been shown to be a
major mediator of septic shock. Based on a mouse model of septic
shock, a TNF receptor immunoadhesin has shown promise as a
candidate for clinical use in treating septic shock (Ashkenazi et
al., supra). Immunoadhesins also have non-therapeutic uses. For
example, the L-selectin receptor immunoadhesin was used as an
reagent for histochemical staining of peripheral lymph node high
endothelial venules (HEV). This reagent was also used to isolate
and characterize the L-selectin ligand (Ashkenazi et al.,
supra).
[0017] If the two arms of the immunoadhesin structure have
different specificities, the immunoadhesin is called a "bispecific
immunoadhesin" by analogy to bispecific antibodies. Dietsch et al.,
J. Immunol. Methods 162:123 (1993) describe such a bispecific
immunoadhesin combining the extracellular domains of the adhesion
molecules, E-selectin and P-selectin. Binding studies indicated
that the bispecific immunoglobulin fusion protein so formed had an
enhanced ability to bind to a myeloid cell line compared to the
monospecific immunoadhesins from which it was derived.
[0018] Antibody-Immunoadhesin Chimeras
[0019] Antibody-immunoadhesin (Ab/Ia) chimeras have also been
described in the literature. These molecules combine the binding
region of an immunoadhesin with the binding domain of an
antibody.
[0020] Berg et al., PNAS (USA) 88:4723-4727 (1991) made a
bispecific antibody-immunoadhesin chimera which was derived from
murine CD4-IgG. These workers constructed a tetrameric molecule
having two arms. One arm was composed of CD4 fused with an antibody
heavy-chain constant domain along with a CD4 fusion with an
antibody alight-chain constant domain. The other arm was composed
of a complete heavy-chain of an anti-CD3 antibody along with a
complete light-chain of the same antibody. By virtue of the CD4-IgG
arm, this bispecific molecule binds to CD3 on the surface of
cytotoxic T cells. The juxtaposition of the cytotoxic cells and
HIV-infected cells results in specific killing of the latter
cells.
[0021] While Berg et al. supra describe a bispecific molecule that
was tetrameric in structure, it is possible to produce a trimeric
hybrid molecule that contains only one CD4-IgG fusion. See Chamow
et al., J. Immunol. 153:4268 (1994). The first arm of this
construct is formed by a humanized anti-CD3 K light chain and a
humanized anti-CD3 .gamma. heavy chain. The second arm is a CD4-IgG
immunoadhesin which combines part of the extracellular domain of
CD4 responsible for gp120 binding with the Fc domain of IgG. The
resultant Ab/Ia chimera mediated killing of HIV-infected cells
using either pure cytotoxic T cell preparations or whole peripheral
blood lymphocyte (PBL) fractions that additionally included Fc
receptor-bearing large granular lymphocyte effector cells.
[0022] In the manufacture of the multispecific antibody
heteromultimers, it is desirable to increase the yields of the
desired heteromultimer over the homomultimer(s). The current method
of choice for obtaining Fc-containing BsAb remains the hybrid
hybridoma, in which two antibodies are coexpressed (Milstein and
Cuello, Nature 305:537-540 (1983)).
[0023] In hybrid hybridomas, heavy (H) chains typically form
homodimers as well as the desired heterodimers. Additionally, light
(L) chains frequently mispair with non-cognate heavy chains. Hence,
coexpression of two antibodies may produce up to ten heavy and
light chain pairings (Suresh, M. R., et al. Methods Enzymol.
121:210-228 (1986)). These unwanted chain pairings compromise the
yield of the BsAb and inevitably impose significant, and sometimes
insurmountable, purification challenges (Smith, et al. (1992)
supra; and Massimo, et al. (1997) supra).
[0024] Antibody heavy chains have previously been engineered to
drive heterodimerization by introducing sterically complementary
mutations in multimerization domains at the C.sub.H3 domain
interface (Ridgway et al. Protein Eng. 9:617-621 (1996)) and
optimization by phage display as described herein. Chains
containing the modified C.sub.H3 domains yield up to approximately
90% heterodimer as judged by formation of an antibody/immunoadhesin
hybrid (Ab/Ia). Heterodimerized heavy chains may still mispair with
the non-cognate light chain, thus hampering recovery of the BsAb of
interest.
SUMMARY OF THE INVENTION
[0025] This application describes a strategy which serves to
enhance the formation of a desired heteromultimeric bispecific
antibody from a mixture of monomers by engineering an interface
between a first and second polypeptide for hetero-oligomerization
and by providing a common variable light chain to interact with
each of the heteromeric variable heavy chain regions of the
bispecific antibody. There are three possible hetero- and
homomultimers that can form from a first and second polypeptide,
each of which is, in turn, associated with a first and second light
chain, respectively. This gives rise to a total of ten possible
chain pairings (FIG. 1A). A method of enhancing the formation of
the desired heteromultimer can greatly enhance the yield over
undesired heteromultimers and homomultimers.
[0026] The preferred interface between a first and second
polypeptide of the heteromultimeric antibody comprises at least a
part of the C.sub.H3 domain of an antibody constant domain. The
domain of each of the first and second polypeptides that interacts
at the interface is called the multimerization domain. Preferably,
the multimerization domain promotes interaction between a specific
first polypeptide and a second polypeptide, thereby increasing the
yield of desired heteromultimer (FIG. 1B). Interaction may be
promoted at the interface by the formation of
protuberance-into-cavity complementary regions; the formation of
non-naturally occurring disulfide bonds; leucine zipper;
hydrophobic regions; and hydrophilic regions. "Protuberances" are
constructed by replacing small amino acid side chains from the
interface of the first polypeptide with larger side chains (e.g.
tyrosine or tryptophan). Compensatory "cavities" of identical or
similar size to the protuberances are optionally created on the
interface of the second polypeptide by replacing large amino acid
side chains with smaller ones (e.g. alanine or threonine). Where a
suitably positioned and dimensioned protuberance or cavity exists
at the interface of either the first or second polypeptide, it is
only necessary to engineer a corresponding cavity or protuberance,
respectively, at the adjacent interface. Non-naturally occurring
disulfide bonds are constructed by replacing on the first
polypeptide a naturally occurring amino acid with a free
thiol-containing residue, such as cysteine, such that the free
thiol interacts with another free thiol-containing residue on the
second polypeptide such that a disulfide bond is formed between the
first and second polypeptides (FIG. 1B).
[0027] Single chain Fv fragments from a large non-immunized phage
display library (Vaughan, T. J. et al. (1996) Nature Biotechnology
14:309-314, herein incorporated by reference in its entirety)
revealed V-gene usage in which V.sub.H and V.sub.L sequences
derived from certain germline V-gene segments predominated.
families predominated in the repertoire. Examples of chain
promiscuity in the repertoire were noted in which a particular
heavy or light chain is found in combination with different partner
chains (Vaughan, T. J. et al. (1996) supra).
[0028] It is disclosed herein that the preparation of a desired
heteromultimeric multispecific antibody is enhanced when a common
light chain is provided to pair with each of the variable heavy
chains of the multispecific antibody. Use of a common variable
light chain reduces the number of monomers that must correctly pair
to form the antigen binding domains by limiting the number of light
chains from two or more light chains (in a bispecific or
multispecific antibody, respectively, prior to disclosure of the
instant invention) to one light chain (in a multispecific antibody
of the invention, see FIG. 1C).
[0029] Accordingly, the invention relates to a method of preparing
a heteromultimeric multispecific antibody, the antibody comprising
1) a first polypeptide and a second polypeptide (and additional
polypeptides accord to the multiplicity of the antibody) which meet
at an interface, wherein the first and additional polypeptides
(i.e., a first and second polypeptide) each include a
multimerization domain forming an interface between the first and
second (or at least one additional) polypeptides, and the
multimerization domains promote stable interaction between first
and additional polypeptides, and 2) a binding domain in each of the
first and at least one additional polypeptide (i.e. a second
polypeptide), each binding domain comprising a variable heavy chain
and a variable light chain, wherein the variable light chain of the
first polypeptide and the variable light chain of the second
polypeptide have a common amino acid sequence, which common
sequence has an amino acid sequence identity to an original light
chain of each of the polypeptides of at least 80%, preferably at
least 90%, more preferably at least 95% and most preferably 100%
sequence identity. The method comprises the steps of
[0030] (i) culturing a host cell comprising nucleic acid encoding
the first polypeptide, the second polypeptide, and the common light
chain wherein the culturing is such that the nucleic acid is
expressed; and
[0031] (ii) recovering the multispecific antibody from the host
cell culture;
[0032] In a related embodiment of the invention the nucleic acid
encoding the first polypeptide or the nucleic acid encoding the
second polypeptide, or both, has been altered from the original
nucleic acid to encode the interface or a portion thereof.
[0033] In another embodiment of the method, the interface of the
first polypeptide comprises a free thiol-containing residue which
is positioned to interact with a free thiol-containing residue of
the interface of the second polypeptide such that a disulfide bond
is formed between the first and second polypeptides. According to
the invention, the nucleic acid encoding the first polypeptide has
been altered from the original nucleic acid to encode the free
thiol-containing residue or the nucleic acid encoding the second
polypeptide has been altered from the original nucleic acid to
encode the free thiol-containing residue, or both.
[0034] In another embodiment of the method, the nucleic acid
encoding both the first polypeptide and at least one additional
polypeptide (i.e., a second polypeptide) are altered to encode the
protuberance and cavity, respectively. Preferably the first and
second polypeptides each comprise an antibody constant domain such
as the C.sub.H3 domain of a human IgG.sub.1.
[0035] In another aspect, the invention provides a heteromultimer
(such as a bispecific antibody, bispecific immunoadhesin or
antibody/immunoadhesin chimera) comprising a first polypeptide and
a second polypeptide which meet at an interface. The interface of
the first polypeptide comprises a multimerization domain which is
positioned to interact with a multimerization domain on the at
least one additional polypeptide (i.e., a second polypeptide) to
form an interface between the first and second polypeptide. In
preferred embodiments of the invention, the multimerization domains
are altered to promote interaction between a specific first
polypeptide and a specific second polypeptide, which alterations
include, but are not limited to, the generation of a protuberance
or cavity, or both; the generation of non-naturally occurring
disulfide bonds; the generation of complementary hydrophobic
regions; and the generation of complementary hydrophilic regions.
The heteromultimeric multispecfic antibody may be provided in the
form of a composition further comprising a pharmaceutically
acceptable carrier.
[0036] The invention also relates to a host cell comprising nucleic
acid encoding the heteromultimeric multispecific antibody of the
preceding paragraph wherein the nucleic acid encoding the first
polypeptide and at least one additional polypeptide (i.e., a second
polypeptide) is present in a single vector or in separate vectors.
The host cell can be used in a method of making a heteromultimeric
multispecific antibody which involves culturing the host cell so
that the nucleic acid is expressed, and recovering the
heteromultimeric antibody from the cell culture.
[0037] In yet a further aspect, the invention provides a method of
preparing a heteromultimeric multispecific antibody comprising:
[0038] (a) selecting a first nucleic acid encoding a first
polypeptide comprising an amino acid residue in the interface of
the first polypeptide that is positioned to interact with an amino
acid residue of interface of at least one additional polypeptide.
In an embodiment the nucleic acid is altered from the original to
encode the interacting amino acid residues. In another embodiment,
the first nucleic acid is altered to encode an amino acid residue
having a larger side chain volume, thereby generating a
protuberance on the first polypeptide;
[0039] (b) altering a second nucleic acid encoding a second
polypeptide so that an amino acid residue in the interface of the
second polypeptide is replaced with an amino acid residue having a
smaller side chain volume, thereby generating a cavity in the
second polypeptide, wherein the protuberance is positioned to
interact with the cavity;
[0040] (c) introducing into a host cell the first and second
nucleic acids and culturing the host cell so that expression of the
first and second nucleic acid occurs; and
[0041] (d) recovering the heteromultimeric antibody formed from the
cell culture
[0042] It may also be desirable to construct a multispecific
antibody (such as a bispecific antibody) that incorporates a
previously identified antibody. Under these circumstances it is
desirable to identify a heavy chain that when paired with the
original light chain will bind specifically to a second antigen of
interest. The methods of Figini et al. (Figini, M. et al. (1994) J.
Mol. Biol. 239:68-78, herein incorporated by reference in its
entirety) may be used to identify such a heavy chain. First a phage
library would be treated with guanidine hydrochloride to dissociate
the original light chain. Next, the heavy chains displayed on phage
would be reconstituted with the light chain of interest by removing
the denaturant (such as by dialysis). Panning against the second
antigen of interest would then be conducted to identify the desired
heavy chain. The invention further embodies a multispecific
antibody prepared by this method of selecting a heavy chain to pair
with a chosen light chain, nucleic acid encoding the antibody, and
a host cell comprising the nucleic acid.
[0043] The invention provides a mechanism for increasing the yields
of the heteromultimer over other unwanted end-products such as
undesired heteromultimers and/or homomultimers (see FIG. 1A-1C).
Preferably, the yields of the desired heteromultimer recovered from
recombinant cell culture are at least greater than 80% by weight
and preferably greater than 90% by weight compared to the
by-product undesired heterodimer or homomultimer(s).
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIGS. 1A-1C. FIG. 1A is a diagram of the formation of
Fc-containing bispecific antibodies when no engineering is
performed to enhance heteromultimerization over
homomultimerization. FIG. 1B is a diagram showing pairing that
occurs when heavy (H) chains are engineered such that desired
heteromultimerization is favored over undesired
heteromultimerization over homomultimerization. FIG. 1C is a
diagram showing pairing that occurs when antibodies are chosen
which share the same light (L) chain to circumvent the problem of
light chains pairing with non-cognate heavy chains.
[0045] FIGS. 2A-2C. FIG. 2A diagrams a selection scheme for
C.sub.H3 heterodimer using phage display vector, pRA2. Phage
displaying stable C.sub.H3 heterodimers are captured using an
antibody directed to the gD flag. FIG. 2B diagrams a dicistronic
operon in which C.sub.H3 expressed from a synthetic gene is
co-secreted with a second copy of C.sub.H3 expressed from the
natural gene (Ellison et al. Nucleic Acids Res. 10:4071-4079
(1982)) as a fusion protein with M13 gene III protein. The
synthetic C.sub.H3 gene is preceded by a sequence encoding a
peptide derived from herpes simplex virus glycoprotein D (gD flag,
Lasky, L. A. and Dowbenko, D. J. (1984) DNA 3:23-29; Berman, P. W.
et al., (1985) Science 227:1490-1492 and a cleavage (G) site for
the site-specific protease, Genenase I (Carter, P. et al. (1989)
Proteins: Structure, Function and Genetics 6:240-248). FIG. 2C is
the nucleic acid sequence of the dicistronic operon (SEQ ID NO:1)
of FIG. 2B in which the residues in the translated C.sub.H3 genes
are numbered according to the Eu system of Kabat et al. In
Sequences of Proteins of Immunological Interest, 5th ed. vol. 1,
pp. 688-696, NIH, Bethesda, Md. (1991). Protuberance mutation T366W
is shown, as are the residues targeted for randomization in the
natural C.sub.H3 gene (366, 368, and 407).
[0046] FIGS. 3A-3C. FIGS. 3A and 3B are bar graphs of the results
of scanning densitometric analysis of SDS-PAGE of protein
A-purified products from cotransfection of antibody (Ab) heavy and
light chains with immunoadhesin (Ia). Data presented are the mean
of two independent experiments. The x-axis indicates the ratios of
input DNA by mass (Ia:H:L) and the y-axis indicates the percentage
of each type of product multimer with respect to total product
protein. FIG. 3C is a diagram of the possible product
multimers.
[0047] FIG. 4 is a comparison of the V.sub.L sequences of eight
different antibodies with specificities for Axl, Rse, IgER, Ob-R,
and VEGF. The position of the antigen binding CDR residues
according to sequence definition (Kabat et al. (1991) supra) or
structural definition (Chothia, C. and Lesk, A. M. J. Mol. Biol.
(1987) 196:901-917) are shown by underlining and #, respectively.
Residues that differ from the Axl.78 sequence are shown by double
underlining.
[0048] FIG. 5 is a comparison of the heavy and light chains of
selected anti-Ob-R and anti-HER3 clones. Shown are the V.sub.H and
the common V.sub.L sequences of anti-Ob-R clone 26 and anti-HER3
clone 18 used to construct a bispecific antibody.
[0049] FIG. 6 is a matrix representing the amino acid sequence
identity between the light chains of antibodies raised to HER3
versus the light chains of antibodies raised to Ob-R. Antibodies
having light chains with 100% sequence identity are indicated in
blackened boxes. Antibodies having light chains with 98-99%
sequence identity are indicated in white boxes. The antibody clone
identity is indicated below the matrix.
I. Definitions
[0050] In general, the following words or phrases have the
indicated definitions when used in the description, examples, and
claims:
[0051] A "heteromultimer", "heteromultimeric polypeptide", or
"heteromultimeric multispecific antibody" is a molecule comprising
at least a first polypeptide and a second polypeptide, wherein the
second polypeptide differs in amino acid sequence from the first
polypeptide by at least one amino acid residue. Preferably, the
heteromultimer has binding specificity for at least two different
ligands or binding sites. The heteromultimer can comprise a
"heterodimer" formed by the first and second polypeptide or can
form higher order tertiary structures where polypeptides in
addition to the first and second polypeptide are present. Exemplary
structures for the heteromultimer include heterodimers (e.g. the
bispecific immunoadhesin described by Dietsch et al., supra),
heterotrimers (e.g. the Ab/Ia chimera described by Chamow et al.,
supra), heterotetramers (e.g. a bispecific antibody) and further
oligomeric structures.
[0052] As used herein, "multimerization domain" refers to a region
of each of the polypeptides of the heteromultimer. The
"multimerization domain" promotes stable interaction of the
chimeric molecules within the heteromultimer complex. Preferably,
the multimerization domain promotes interaction between a specific
first polypeptide and a specific second polypeptide, thereby
enhancing the formation of the desired heteromultimer and
substantially reducing the probability of the formation of
undesired heteromultimers or homomultimers. The multimerization
domains may interact via an immunoglobulin sequence, leucine
zipper, a hydrophobic region, a hydrophilic region, or a free thiol
which forms an intermolecular disulfide bond between the chimeric
molecules of the chimeric heteromultimer. The free thiol may be
introduced into the interface of one or more interacting
polypeptides by substituting a naturally occurring residue of the
polypeptide with, for example, a cysteine at a position allowing
for the formation of a disulfide bond between the polypeptides. The
multimerization domain may comprise an immunoglobulin constant
region. A possible multimerization domain useful in the present
invention is disclosed in PCT/US90/06849 (herein incorporated by
reference in its entirety) in which hybrid immunoglobulins are
described. In addition a multimerization region may be engineered
such that steric interactions not only promote stable interaction,
but further promote the formation of heterodimers over homodimers
from a mixture of monomers. See, for example, PCT/US96/01598
(herein incorporated by reference in its entirety) in which a
"protuberance-into-cavity" strategy is disclosed for an interface
between a first and second polypeptide for hetero-oligomerization.
"Protuberances" are constructed by replacing small amino acid side
chains from the interface of the first polypeptide with larger side
chains (e.g. tyrosine or tryptophan). Compensatory "cavities" of
identical or similar size to the protuberances are optionally
created on the interface of the second polypeptide by replacing
large amino acid side chains with smaller ones (e.g. alanine or
threonine). The immunoglobulin sequence preferably, but not
necessarily, is an immunoglobulin constant domain. The
immunoglobulin moiety in the chimeras of the present invention may
be obtained from IgG.sub.1, IgG.sub.2, IgG.sub.3 or IgG.sub.4
subtypes, IgA, IgE, IgD or IgM, but preferably IgG.sub.1,
IgG.sub.2, IgG.sub.3 or IgG.sub.4.
[0053] By "free thiol-containing compound" is meant a compound that
can be incorporated into or reacted with an amino acid of a
polypeptide interface of the invention such that the free thiol
moiety of the compound is positioned to interact with a free thiol
of moiety at the interface of additional polypeptide of the
invention to form a disulfide bond. Preferably, the free
thiol-containing compound is cysteine.
[0054] The term "epitope tagged" when used herein refers to a
chimeric polypeptide comprising the entire chimeric heteroadhesin,
or a fragment thereof, fused to a "tag polypeptide". The tag
polypeptide has enough residues to provide an epitope against which
an antibody can be made, yet is short enough such that it does not
interfere with activity of the chimeric heteroadhesin. The tag
polypeptide preferably is fairly unique so that the antibody
thereagainst does not substantially cross-react with other
epitopes. Suitable tag polypeptides generally have at least 6 amino
acid residues and usually between about 8-50 amino acid residues
(preferably between about 9-30 residues). An embodiment of the
invention encompasses a chimeric heteroadhesin linked to an epitope
tag, which tag is used to detect the adhesin in a sample or recover
the adhesin from a sample.
[0055] As used herein, "common light chain" or "common amino acid
sequence of the light chain" refers to the amino acid sequence of
the light chain in the multispecific antibody of the invention.
Panels of antibodies were generated against at least two different
antigens by panning a phage display library such as that described
by Vaughan, et al. (1996) supra, herein incorporated by reference
in its entirety with particular reference to the method of
selection of the phagemid library). The light chain sequences were
compared with respect to the variable light chain amino acid
sequences. Useful light chains from the compared panels are those
having amino acid sequence identity of at least 80%, preferably at
least 90%, more preferably at least 95%, and most preferably 100%
identity. A common light chain sequence is a sequence designed to
be an approximation of the two compared light chain sequences.
Where the compared light chains are 100% sequence identical at the
amino acid level, the common light chain is identical to the light
chains from the selected library clones, even though the light
chain functions in a different binding domain of the multispecific
antibody. Where the compared light chains differ as described
above, the common light chain may differ from one or the other, or
both, of the compared light chains from the library clones. In a
case in which the common light chain differs from one or the other,
or both of the library clones, it is preferred that the differing
residues occur outside of the antigen binding CDR residues of the
antibody light chain. For example, the position of the antigen
binding CDR residues may be determined according to a sequence
definition (Kabat et al. (1991) supra) or structural definition
(Chothia and Lesk (1987) J. Mol. Biol. 196:901-917).
[0056] As used herein, "amino acid sequence identity" refers to the
percentage of the amino acids of one sequence are the same as the
amino acids of a second amino acid sequence. 100% sequence identity
between polypeptide chains means that the chains are identical.
[0057] As used herein, "polypeptide" refers generally to peptides
and proteins having more than about ten amino acids. Preferably,
mammalian polypeptides (polypeptides that were originally derived
from a mammalian organism) are used, more preferably those which
are directly secreted into the medium. Examples of bacterial
polypeptides include, e.g., alkaline phosphatase and
.beta.-lactamase. Examples of mammalian polypeptides include
molecules such as renin, a growth hormone, including human growth
hormone; 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; inhibin; activin; vascular
endothelial growth factor (VEGF); receptors for hormones or growth
factors; integrin; 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 such as NGF-.beta.; 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, including TGF-.beta.1, TGF-.beta.2,
TGF-.beta.3, TGF-.beta.4, or TGF-.beta.5; 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
CD-3, CD-4, CD-8, and CD-19; 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; addressing;
regulatory proteins; antibodies; and fragments of any of the
above-listed polypeptides.
[0058] The "first polypeptide" is any polypeptide which is to be
associated with a second polypeptide. The first and second
polypeptide meet at an "interface" (defined below). In addition to
the interface, the first polypeptide may comprise one or more
additional domains, such as "binding domains" (e.g. an antibody
variable domain, receptor binding domain, ligand binding domain or
enzymatic domain) or antibody constant domains (or parts thereof)
including C.sub.H2, C.sub.H1 and C.sub.L domains. Normally, the
first polypeptide will comprise at least one domain which is
derived from an antibody. This domain conveniently is a constant
domain, such as the C.sub.H3 domain of an antibody and can form the
interface of the first polypeptide. Exemplary first polypeptides
include antibody heavy chain polypeptides, chimeras combining an
antibody constant domain with a binding domain of a heterologous
polypeptide (i.e. an immunoadhesin, see definition below), receptor
polypeptides (especially those which form dimers with another
receptor polypeptide, e.g., interleukin-8 receptor (IL-8R) and
integrin heterodimers (e.g. LFA-1 or GPIIIb/IIIa)), ligand
polypeptides (e.g. nerve growth factor (NGF), neurotrophin-3
(NT-3), and brain-derived neurotrophic factor (BDNF)-see Arakawa et
al. J. Biol. Chem. 269(45): 27833-27839 (1994) and Radziejewski et
al. Biochem. 32(48): 1350 (1993)) and antibody variable domain
polypeptides (e.g. diabodies). The preferred first polypeptide is
selected from an antibody heavy chain fused to a constant domain of
an immunoglobulin, wherein the constant domain has been altered at
the interface to promote preferential interaction with a second
polypeptide of the invention.
[0059] The "second polypeptide" is any polypeptide which is to be
associated with the first polypeptide via an "interface". In
addition to the interface, the second polypeptide may comprise
additional domains such as a "binding domain" (e.g. an antibody
variable domain, receptor binding domain, ligand binding domain or
enzymatic domain), or antibody constant domains (or parts thereof)
including C.sub.H2, C.sub.H1 and C.sub.L domains. Normally, the
second polypeptide will comprise at least one domain which is
derived from an antibody. This domain conveniently is a constant
region, such as the C.sub.H3 domain of an antibody and can form the
interface of the second polypeptide. Exemplary second polypeptides
include antibody heavy chain polypeptides, chimeras combining an
antibody constant domain with a binding domain of a heterologous
polypeptide (i.e. an immunoadhesin, see definition below), receptor
polypeptides (especially those which form dimers with another
receptor polypeptide, e.g., interleukin-8 receptor (IL-8R) and
integrin heterodimers (e.g. LFA-1 or GPIIIb/IIIa)), ligand
polypeptides (e.g. nerve growth factor (NGF), neurotrophin-3
(NT-3), and brain-derived neurotrophic factor (BDNF)-see Arakawa et
al. J. Biol. Chem. 269(45):27833-27839 (1994) and Radziejewski et
al. Biochem. 32(48):1350 (1993)) and antibody variable domain
polypeptides (e.g. diabodies). The preferred second polypeptide is
selected from an antibody heavy chain fused to a constant domain of
an immunoglobulin, wherein the constant domain has been altered at
the interface to promote preferential interaction with a first
polypeptide of the invention.
[0060] A "binding domain" comprises any region of a polypeptide
which is responsible for selectively binding to a molecule of
interest (e.g. an antigen, ligand, receptor, substrate or
inhibitor) Exemplary binding domains include an antibody variable
domain, receptor binding domain, ligand binding domain and an
enzymatic domain. In preferred embodiments, the binding domain
includes an immunoglobulin heavy chain and light chain. According
to the bispecific antibodies of the invention and the method of
making them, the light chain for each binding domain of the
bispecific antibody is a common light chain, thereby avoiding the
formation of undesired hetermultimers in which mispairing of heavy
and light chains occurs.
[0061] The term "antibody" as it refers to the invention shall mean
a polypeptide containing one or more domains that bind an epitope
on an antigen of interest, where such domain(s) are derived from or
have sequence identity with the variable region of an antibody.
Examples of antibodies include full length antibodies, antibody
fragments, single chain molecules, bispecific or bifunctional
molecules, diabodies, chimeric antibodies (e.g. humanized and
PRIMATIZED.TM. antibodies), and immunoadhesins. "Antibody
fragments" include Fv, Fv', Fab, Fab', and F(ab').sub.2
fragments.
[0062] "Humanized" forms of non-human (e.g. rodent or primate)
antibodies are specific chimeric immunoglobulins, immunoglobulin
chains or fragments thereof 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 complementary determining region (CDR) of the
recipient are replaced by residues from a CDR of a non-human
species (donor antibody) such as mouse, rat, rabbit or 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, the humanized antibody may comprise residues which are
found neither in the recipient antibody nor in the imported CDR or
framework sequences. These modifications are made to further refine
and maximize 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 CDR regions 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
preferably also will comprise at least a portion of an
immunoglobulin constant region (Fc), typically that of a human
immunoglobulin. The humanized antibody includes a PRIMATIZED.TM.
antibody wherein the antigen-binding region of the antibody is
derived from an antibody produced by immunizing macaque monkeys
with the antigen of interest.
[0063] A "multispecific antibody" is a molecule having 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-interferon-.alpha.(IFN-.alpha.)/anti-hybridoma
idiotype, 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 no 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 (see
Fanger et al., supra); 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, anti-CEA/anti-.beta.-galactosidase (see Nolan
et al., supra). Examples of trispecific antibodies include
anti-CD3/anti-CD4/anti-CD37, anti-CD3/anti-CD5/anti-CD37 and
anti-CD3/anti-CD8/anti-CD37.
[0064] As used herein, the term "immunoadhesin" designates
antibody-like molecules which combine the "binding domain" of a
heterologous protein (an "adhesin", e.g. a receptor, ligand or
enzyme) with the effector functions of immunoglobulin constant
domains. Structurally, the immunoadhesins comprise a fusion of the
adhesin amino acid sequence with the desired binding specificity
which is other than the antigen recognition and binding site
(antigen combining site) of an antibody (i.e. is "heterologous")
and an immunoglobulin constant domain sequence. The immunoglobulin
constant domain sequence in the immunoadhesin may be obtained from
any immunoglobulin, such as IgG.sub.1, IgG.sub.2, IgG.sub.3, or
IgG.sub.4 subtypes, IgA, IgE, IgD or IgM.
[0065] The term "ligand binding domain" as used herein refers to
any native cell-surface receptor or any region or derivative
thereof retaining at least a qualitative ligand binding ability,
and preferably the biological activity of a corresponding native
receptor. In a specific embodiment, the receptor is from a
cell-surface polypeptide having an extracellular domain which is
homologous to a member of the immunoglobulin supergenefamily. Other
typical receptors, are not members of the immunoglobulin
supergenefamily but are nonetheless specifically covered by this
definition, are receptors for cytokines, and in particular
receptors with tyrosine kinase activity (receptor tyrosine
kinases), members of the hematopoietin and nerve growth factor
receptor superfamilies, and cell adhesion molecules, e.g. (E-, L-
and P-) selectins.
[0066] The term "receptor binding domain" is used to designate any
native ligand for a receptor, including cell adhesion molecules, or
any region or derivative of such native ligand retaining at least a
qualitative receptor binding ability, and preferably the biological
activity of a corresponding native ligand. This definition, among
others, specifically includes binding sequences from ligands for
the above-mentioned receptors.
[0067] As used herein the phrase "multispecific immunoadhesin"
designates immunoadhesins (as hereinabove defined) having at least
two binding specificities (i.e. combining two or more adhesin
binding domains). Multispecific immunoadhesins can be assembled as
heterodimers, heterotrimers or heterotetramers, essentially as
disclosed in WO 89/02922 (published Apr. 6, 1989), in EP 314,317
(published May 3, 1989), and in U.S. Pat. No. 5,116,964 issued May
2, 1992. Preferred multispecific immunoadhesins are bispecific.
Examples of bispecific immunoadhesins include
CD4-IgG/TNFreceptor-IgG and CD4-IgG/L-selectin-IgG. The last
mentioned molecule combines the lymph node binding function of the
lymphocyte homing receptor (LHR, L-selectin), and the HIV binding
function of CD4, and finds potential application in the prevention
or treatment of HIV infection, related conditions, or as a
diagnostic.
[0068] An "antibody-immunoadhesin chimera (Ab/Ia chimera)"
comprises a molecule which combines at least one binding domain of
an antibody (as herein defined) with at least one immunoadhesin (as
defined in this application). Exemplary Ab/Ia chimeras are the
bispecific CD4-IgG chimeras described by Berg et al., supra and
Chamow et al., supra.
[0069] The "interface" comprises those "contact" amino acid
residues (or other non-amino acid groups such as carbohydrate
groups, NADH, biotin, FAD or haem group) in the first polypeptide
which interact with one or more "contact" amino acid residues (or
other non-amino acid groups) in the interface of the second
polypeptide. The preferred interface is a domain of an
immunoglobulin such as a variable domain or constant domain (or
regions thereof), however the interface between the polypeptides
forming a heteromultimeric receptor or the interface between two or
more ligands such as NGF, NT-3 and BDNF are included within the
scope of this term. The preferred interface comprises the C.sub.H3
domain of an immunoglobulin which preferably is derived from an IgG
antibody and most preferably a human IgG.sub.1antibody.
[0070] An "original" amino acid residue is one which is replaced by
an "import" residue which can have a smaller or larger side chain
volume than the original residue. The import amino acid residue can
be a naturally occurring or non-naturally occurring amino acid
residue, but preferably is the former. "Naturally occurring" amino
acid residues are those residues encoded by the genetic code and
listed in Table 1 of PCT/US96/01598, herein incorporated by
reference in its entirety. By "non-naturally occurring" amino acid
residue is meant a residue which is not encoded by the genetic
code, but which is able to covalently bind adjacent amino acid
residue(s) in the polypeptide chain. Examples of non-naturally
occurring amino acid residues are norleucine, ornithine, norvaline,
homoserine and other amino acid residue analogues such as those
described in Ellman et al., Meth. Enzym. 202:301-336 (1991), for
example. 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, this involves
chemically activating a suppressor tRNA with a non-naturally
occurring amino acid residue followed by in vitro transcription and
translation of the RNA. The method of the instant invention
involves replacing at least one original amino acid residue, but
more than one original residue can be replaced. Normally, no more
than the total residues in the interface of the first or second
polypeptide will comprise original amino acid residues which are
replaced. The preferred original residues for replacement are
"buried". By "buried" is meant that the residue is essentially
inaccessible to solvent. The preferred import residue is not
cysteine to prevent possible oxidation or mispairing of disulfide
bonds.
[0071] By "original nucleic acid" is meant the nucleic acid
encoding a polypeptide of interest which can be altered to encode
within the multimerization domain amino acids whose side chains
interact at the interface between the first and second polypeptide
promoting stable interaction between the polypeptides. Such
alterations may generate without limitation such stable
interactions as protuberance-into-cavity, non-naturally occurring
disulfide bonds, leucine zipper, hydrophobic interactions, and
hydrophilic interations. Preferably, the alteration is chosen which
promotes specific interaction between a first and second
polypeptide of interest and effectively excludes interactions that
result in undesired heteromer pairing or the formation of homomers.
The original or starting nucleic acid may be a naturally occurring
nucleic acid or may comprise a nucleic acid which has been
subjected to prior alteration (e.g. a humanized antibody fragment).
By "altering" the nucleic acid is meant that the original nucleic
acid is genetically engineered or mutated by inserting, deleting or
replacing at least one codon encoding an amino acid residue of
interest. Normally, a codon encoding an original residue is
replaced by a codon encoding an import residue. Techniques for
genetically modifying a DNA in this manner have been reviewed in
Mutagenesis: a Practical Approach, M. J. McPherson, Ed., (IRL
Press, Oxford, UK. (1991), and include site-directed mutagenesis,
cassette mutagenesis and polymerase chain reaction (PCR)
mutagenesis, for example.
[0072] The protuberance, cavity, or free thiol (such as a cysteine
residue for disulfide bond formation) can be "introduced" into the
interface of the first or second polypeptide by synthetic means,
e.g. by recombinant techniques, in vitro peptide synthesis, those
techniques for introducing non-naturally occurring amino acid
residues previously described, by enzymatic or chemical coupling of
peptides or some combination of these techniques. According, the
protuberance, cavity or free thiol which is "introduced" is
"non-naturally occurring" or "non-native", which means that it does
not exist in nature or in the original polypeptide (e.g. a
humanized monoclonal antibody).
[0073] Preferably the import amino acid residue for forming the
protuberance has a relatively small number of "rotamers" (e.g.
about 3-6). A "rotamer" is an energetically favorable conformation
of an amino acid side chain. The number of rotamers of the various
amino acid residues are reviewed in Ponders and Richards, J. Mol.
Biol. 193:775-791 (1987).
[0074] "Isolated" heteromultimer means heteromultimer which has
been identified and separated and/or recovered from a component of
its natural cell culture environment. Contaminant components of its
natural environment are materials which would interfere with
diagnostic or therapeutic uses for the heteromultimer, and may
include enzymes, hormones, and other proteinaceous or
nonproteinaceous solutes. In preferred embodiments, the
heteromultimer will be purified (1) to greater than 95% by weight
of protein 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.
[0075] The heteromultimers of the present invention are generally
purified to substantial homogeneity. The phrases "substantially
homogeneous", "substantially homogeneous form" and "substantial
homogeneity" are used to indicate that the product is substantially
devoid of by-products originated from undesired polypeptide
combinations (e.g. homomultimers). Expressed in terms of purity,
substantial homogeneity means that the amount of by-products does
not exceed 10%, and preferably is below 5%, more preferably below
1%, most preferably below 0.5%, wherein the percentages are by is
weight.
[0076] 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, a ribosome binding site, and
possibly, other as yet poorly understood sequences. Eukaryotic
cells are known to utilize promoters, polyadenylation signals, and
enhancers.
[0077] 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 accord with conventional practice.
II. Preparation of the Heteromultimer
[0078] 1. Preparation of the Starting Materials
[0079] As a first step, the first and second polypeptide (and any
additional polypeptides forming the heteromultimer) are selected.
Normally, the nucleic acid encoding these polypeptides needs to be
isolated so that it can be altered to encode the protuberance or
cavity, or both, as herein defined. However, the mutations can be
introduced using synthetic means, e.g. by using a peptide
synthesizer. Also, in the case where the import residue is a
non-naturally occurring residue, the method of Noren et al., supra
is available for making polypeptides having such substitutions.
Additionally, part of the heteromultimer is suitably made
recombinantly in cell culture and other part(s) of the molecule are
made by those techniques mentioned above.
[0080] Techniques for isolating antibodies and preparing
immunoadhesins follow. However, it will be appreciated that the
heteromultimer can be formed from, or incorporate, other
polypeptides using techniques which are known in the art. For
example, nucleic acid encoding a polypeptide of interest (e.g. a
ligand, receptor or enzyme) can be isolated from a cDNA library
prepared from tissue believed to possess the polypeptide mRNA and
to express it at a detectable level. Libraries are screened with
probes (such as antibodies or oligonucleotides of about 20-80
bases) designed to identify the gene of interest or the protein
encoded by it. Screening the cDNA or genomic library with the
selected probe may be conducted using standard procedures as
described in chapters 10-12 of Sambrook et al., Molecular Cloning:
A Laboratory Manual (New York: Cold Spring Harbor Laboratory Press,
1989).
[0081] (I) Antibody preparation
[0082] Several techniques for the production of antibodies have
been described which include the traditional hybridoma method for
making monoclonal antibodies, recombinant techniques for making
antibodies (including chimeric antibodies, e.g. humanized
antibodies), antibody production in transgenic animals and the
recently described phage display technology for preparing "fully
human" antibodies. These techniques shall be described briefly
below.
[0083] Polyclonal antibodies to the antigen of interest generally
can be raised in animals by multiple subcutaneous (sc) or
intraperitoneal (ip) injections of the antigen and an adjuvant. It
may be useful to conjugate the antigen (or a fragment containing
the target amino acid sequence) 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. Animals are immunized
against the immunogenic conjugates or derivatives by combining 1 mg
of 1 .mu.g of conjugate (for rabbits or mice, respectively) with 3
volumes of Freud's complete adjuvant and injecting the solution
intradermally at multiple sites. One month later the animals are
boosted with 1/5 to {fraction (1/10)} the original amount of
conjugate in Freud's complete adjuvant by subcutaneous injection at
multiple sites. 7 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 used to enhance
the immune response.
[0084] Monoclonal antibodies are obtained from a population of
substantially homogeneous antibodies using the hybridoma method
first described by Kohler and Milstein, Nature 256:495 (1975) or
may be made by recombinant DNA methods (Cabilly et al., U.S. Pat.
No. 4,816,567). In the hybridoma method, a mouse or other
appropriate host animal, such as hamster, 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)). 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. Preferred myeloma cells are
those that fuse efficiently, support stable high level expression
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
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); and
Brodeur et al., Monoclonal Antibody Production Techniques and
Applications, pp.51-63, Marcel Dekker, Inc., New York, 1987). See,
also, Boerner et al., J. Immunol., 147(1):86-95 (1991) and WO
91/17769, published Nov. 28, 1991, for techniques for the
production of human monoclonal antibodies. Culture medium in which
hybridoma cells are growing is assayed for production of monoclonal
antibodies directed against the antigen of interest. 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). The binding affinity
of the monoclonal antibody can, for example, be determined by the
Scatchard analysis of Munson and Pollard, Anal. Biochem. 107:220
(1980). 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.59-104 (Academic Press, 1986). Suitable
culture media for this purpose include, for example, Dulbecco's
Modified Eagle's Medium or RPMI-1640 medium. In addition, the
hybridoma cells may be grown in vivo as ascites tumors in an
animal. 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.
[0085] 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 90:2551-255 (1993); Jakobovits et al.,
Nature 362:255-258 (1993); Fishwild, D. M., et al. (1996) Nat.
Biotech 14:845-851; and Mendez, M. J., et al. (1997) Nat. Genetics
15:146-156).
[0086] 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), using the antigen of interest to select for a suitable
antibody or antibody fragment. 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 (Mark
et al., Bio/Technol. 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); Griffiths, A. D., et al. (1994) EMBO J.
13:3245-3260; and Vaughan, et al. (1996) supra). Thus, these
techniques are viable alternatives to traditional monoclonal
antibody hybridoma techniques for isolation of "monoclonal"
antibodies (especially human antibodies) which are encompassed by
the present invention.
[0087] DNA encoding the antibodies of the invention 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 murine
antibodies) The hybridoma cells of the invention 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 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. 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,
Morrison et al., Proc. Nat. Acad. Sci. 81:6851 (1984). In that
manner, "chimeric" antibodies are prepared that have the binding
specificity of an anti-antigen monoclonal antibody herein.
[0088] Methods for humanizing non-human antibodies are well known
in the art. Generally, a humanized antibody has one or more amino
acid residues introduced into it from a source which is non-human.
Humanization can be performed essentially 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
(Cabilly, supra), 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. It is 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
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 consensus and import sequence so that the desired antibody
characteristic, such as increased affinity for the target
antigen(s), is achieved. For further details see WO 92/22653,
published Dec 23, 1992.
[0089] (ii) Immunoadhesin Preparation
[0090] Immunoglobulins (Ig) and certain variants thereof are known
and many have been prepared in recombinant cell culture. For
example, see U.S. Pat. No. 4,745,055; EP 256,654; Faulkner et al.,
Nature 298:286 (1982); EP 120,694; EP 125,023; Morrison, J. Immun.
123:793 (1979); Kohler et al., Proc. Natl. Acad. Sci. USA 77:2197
(1980); Raso et al., Cancer Res. 41:2073 (1981); Morrison et al.,
Ann. Rev. Immunol. 2:239 (1984); Morrison, Science 229:1202 (1985);
Morrison et al., Proc. Natl. Acad. Sci. USA 81:6851 (1984); EP
255,694; EP 266,663; and WO 88/03559. Reassorted immunoglobulin
chains also are known. See, for example, U.S. Pat. No. 4,444,878;
WO 88/03565; and EP 68,763 and references cited therein.
[0091] Chimeras constructed from an adhesin binding domain sequence
linked to an appropriate immunoglobulin constant domain sequence
(immunoadhesins) are known in the art. Immunoadhesins reported in
the literature include fusions of the T cell receptor (Gascoigne et
al., Proc. Natl. Acad. Sci. USA 84:2936-2940 (1987)); CD4 (Capon et
al., Nature 337:525-531 (1989); Traunecker et al., Nature 339:68-70
(1989); Zettmeissl et al., DNA Cell Biol. USA 9:347-353 (1990); and
Byrn et al., Nature 344:667-670 (1990)); L-selectin (homing
receptor) (Watson et al., J. Cell. Biol. 110:2221-2229 (1990); and
Watson et al., Nature 349:164-167 (1991)); CD44 (Aruffo et al.,
Cell 61:1303-1313 (1990)); CD28 and B7 (Linsley et al., J. Exp.
Med. 173:721-730 (1991)); CTLA-4 (Lisley et al., J. Exp. Med.
174:561-569 (1991)); CD22 (Stamenkovic et al., Cell 66:1133-1144
(1991)); TNF receptor (Ashkenazi et al., Proc. Natl. Acad. Sci. USA
88:10535-10539 (1991); Lesslauer et al., Eur. J. Immunol.
27:2883-2886 (1991); and Peppel et al., J. Exp. Med. 174:1483-1489
(1991)); and IgE receptor .alpha. (Ridgway and Gorman, J. Cell.
Biol. Vol. 115, Abstract No. 1448 (1991)).
[0092] The simplest and most straightforward immunoadhesin design
combines the binding domain(s) of the adhesin (e.g. the
extracellular domain (ECD) of a receptor) with the hinge and Fc
regions of an immunoglobulin heavy chain. Ordinarily, when
preparing the immunoadhesins of the present invention, nucleic acid
encoding the binding domain of the adhesin will be fused
C-terminally to nucleic acid encoding the N-terminus of an
immunoglobulin constant domain sequence, however N-terminal fusions
are also possible.
[0093] Typically, in such fusions the encoded chimeric polypeptide
will retain at least functionally active hinge, C.sub.H2 and
C.sub.H3 domains of the constant region of an immunoglobulin heavy
chain. Fusions are also made to the C-terminus of the Fc portion of
a constant domain, or immediately N-terminal to the C.sub.H1 of the
heavy chain or the corresponding region of the light chain. The
precise site at which the fusion is made is not critical;
particular sites are well known and may be selected in order to
optimize the biological activity, secretion, or binding
characteristics of the Ia.
[0094] In a preferred embodiment, the adhesin sequence is fused to
the N-terminus of the Fc domain of immunoglobulin G.sub.1
(IgG.sub.1). It is possible to fuse the entire heavy chain constant
region to the adhesin sequence. However, more preferably, a
sequence beginning in the hinge region just upstream of the papain
cleavage site which defines IgG Fc chemically (i.e. residue 216,
taking the first residue of heavy chain constant region to be 114),
or analogous sites of other immunoglobulins is used in the fusion.
In a particularly preferred embodiment, the adhesin amino acid
sequence is fused to (a) the hinge region and C.sub.H2 and C.sub.H3
or (b) the C.sub.H1, hinge, C.sub.H2 and C.sub.H3 domains, of an
IgG.sub.1, IgG.sub.2, or IgG.sub.3 heavy chain. The precise site at
which the fusion is made is not critical, and the optimal site can
be determined by routine experimentation.
[0095] For bispecific immunoadhesins, the immunoadhesins are
assembled as multimers, and particularly as heterodimers or
heterotetramers. Generally, these assembled immunoglobulins will
have known unit structures. A basic four chain structural unit is
the form in which IgG, IgD, and IgE exist. A four chain unit is
repeated in the higher molecular weight immunoglobulins; IgM
generally exists as a pentamer of four basic units held together by
disulfide bonds. IgA globulin, and occasionally IgG globulin, may
also exist in multimeric form in serum. In the case of multimer,
each of the four units may be the same or different.
[0096] Various exemplary assembled immunoadhesins within the scope
herein are schematically diagrammed below:
[0097] (a) AC.sub.L-AC.sub.L;
[0098] (b) AC.sub.H-[AC.sub.H, AC.sub.L-AC.sub.H,
AC.sub.L-V.sub.HC.sub.H, or V.sub.LC.sub.L-AC.sub.H];
[0099] (c) AC.sub.L-AC.sub.H-[AC.sub.L-AC.sub.H,
AC.sub.L-V.sub.HC.sub.H, V.sub.LC.sub.L-AC.sub.H, or
V.sub.LC.sub.L-V.sub.HC.sub.H];
[0100] (d) AC.sub.L-V.sub.HC.sub.H-[AC.sub.H, or
AC.sub.L-V.sub.HC.sub.H, or V.sub.LC.sub.L-AC.sub.H];
[0101] (e) V.sub.LC.sub.L-AC.sub.H-[AC.sub.L-V.sub.HC.sub.H, or
V.sub.LC.sub.L-AC.sub.H]; and
[0102] (f) [A-Y].sub.n-[V.sub.LC.sub.L-V.sub.HC.sub.H].sub.2,
[0103] wherein each A represents identical or different adhesin
amino acid sequences;
[0104] V.sub.L is an immunoglobulin light chain variable
domain;
[0105] V.sub.H is an immunoglobulin heavy chain variable
domain;
[0106] C.sub.L is an immunoglobulin light chain constant
domain;
[0107] C.sub.H is an immunoglobulin heavy chain constant
domain;
[0108] n is an integer greater than 1;
[0109] Y designates the residue of a covalent cross-linking
agent.
[0110] In the interests of brevity, the foregoing structures only
show key features; they do not indicate joining (J) or other
domains of the immunoglobulins, nor are disulfide bonds shown.
However, where such domains are required for binding activity, they
shall be constructed to be present in the ordinary locations which
they occupy in the immunoglobulin molecules.
[0111] Alternatively, the adhesin sequences can be inserted between
immunoglobulin heavy chain and light chain sequences, such that an
immunoglobulin comprising a chimeric heavy chain is obtained. In
this embodiment, the adhesin sequences are fused to the 3' end of
an immunoglobulin heavy chain in each arm of an immunoglobulin,
either between the hinge and the C.sub.H2 domain, or between the
C.sub.H2 and C.sub.H3 domains. Similar constructs have been
reported by Hoogenboom, et al., Mol. Immunol. 28:1027-1037
(1991).
[0112] An immunoglobulin light chain might be present either
covalently associated to an adhesin-immunoglobulin heavy chain
fusion polypeptide, or directly fused to the adhesin. In the former
case, DNA encoding an immunoglobulin light chain is typically
coexpressed with the DNA encoding the adhesin-immunoglobulin heavy
chain fusion protein. Upon secretion, the hybrid heavy chain and
the light chain will be covalently associated to provide an
immunoglobulin-like structure comprising two disulfide-linked
immunoglobulin heavy chain-light chain pairs. Methods suitable for
the preparation of such structures are, for example, disclosed in
U.S. Pat. No. 4,816,567, issued Mar. 28, 1989.
[0113] In a preferred embodiment, the immunoglobulin sequences used
in the construction of the immunoadhesins of the present invention
are from an IgG immunoglobulin heavy chain constant domain. For
human immunoadhesins, the use of human IgG.sub.1 and IgG.sub.3
immunoglobulin sequences is preferred. A major advantage of using
IgG.sub.1 is that IgG.sub.1, immunoadhesins can be purified
efficiently on immobilized protein A. In contrast, purification of
IgG.sub.3 requires protein G, a significantly less versatile
medium. However, other structural and functional properties of
immunoglobulins should be considered when choosing the Ig fusion
partner for a particular immunoadhesin construction. For example,
the IgG.sub.3 hinge is longer and more flexible, so it can
accommodate larger "adhesin" domains that may not fold or function
properly when fused to IgG.sub.1. Another consideration may be
valency; IgG immunoadhesins are bivalent homodimers, whereas Ig
subtypes like IgA and IgM may give rise to dimeric or pentameric
structures, respectively, of the basic Ig homodimer unit. For
immunoadhesins designed for in vivo application, the
pharmacokinetic properties and the effector functions specified by
the Fc region are important as well. Although IgG.sub.1, IgG.sub.2
and IgG.sub.4 all have in vivo half-lives of 21 days, their
relative potencies at activating the complement system are
different. IgG.sub.4 does not activate complement, and IgG.sub.2 is
significantly weaker at complement activation than IgG.sub.1.
Moreover, unlike IgG.sub.1, IgG.sub.2 does not bind to Fc receptors
on mononuclear cells or neutrophils. While IgG.sub.3 is optimal for
complement activation, its in vivo half-life is approximately one
third of the other IgG isotypes. Another important consideration
for immunoadhesins designed to be used as human therapeutics is the
number of allotypic variants of the particular isotype. In general,
IgG isotypes with fewer serologically-defined allotypes are
preferred. For example, IgG.sub.1, has only four
serologically-defined allotypic sites, two of which (G1m and 2) are
located in the Fc region; and one of these sites, G1m1, is
non-immunogenic. In contrast, there are 12 serologically-defined
allotypes in IgG3, all of which are in the Fc region; only three of
these sites (G3m5, 11 and 21) have one allotype which is
nonimmunogenic. Thus, the potential immunogenicity of a .gamma.3
immunoadhesin is greater than that of a .gamma.1 immunoadhesin.
[0114] Immunoadhesins are most conveniently constructed by fusing
the cDNA sequence encoding the adhesin portion in-frame to an Ig
cDNA sequence. However, fusion to genomic Ig fragments can also be
used (see, e.g. Gascoigne et al., supra; Aruffo et al., Cell
61:1303-1313 (1990); and Stamenkovic et al., Cell 66:1133-1144
(1991)). The latter type of fusion requires the presence of Ig
regulatory sequences for expression. cDNAs encoding IgG heavy-chain
constant regions can be isolated based on published sequences from
cDNA libraries derived from spleen or peripheral blood lymphocytes,
by hybridization or by polymerase chain reaction (PCR) techniques.
The cDNAs encoding the "adhesin" and the Ig parts of the
immunoadhesin are inserted in tandem into a plasmid vector that
directs efficient expression in the chosen host cells.
[0115] 2. Generating a Protuberance and/or Cavity
[0116] As a first step to selecting original residues for forming
the protuberance and/or cavity, the three-dimensional structure of
the heteromultimer is obtained using techniques which are well
known in the art such as X-ray crystallography or NMR. Based on the
three-dimensional structure, those skilled in the art will be able
to identify the interface residues.
[0117] The preferred interface is the C.sub.H3 domain of an
immunoglobulin constant domain. The interface residues of the
C.sub.H3 domains of IgG, IgA, IgD, IgE and IgM have been identified
(see, for example, PCT/US96/01598, herein incorporated by reference
in its entirety), including those which are optimal for replacing
with import residues; as were the interface residues of various IgG
subtypes and "buried" residues. The basis for engineering the
C.sub.H3 interface is that X-ray crystallography has demonstrated
that the intermolecular association between human IgG, heavy chains
in the Fc region includes extensive protein/protein interaction
between C.sub.H3 domains whereas the glycosylated C.sub.H2 domains
interact via their carbohydrate (Deisenhofer, Biochem. 20:2361-2370
(1981)). In addition there are two inter-heavy chain disulfide
bonds which are efficiently formed during antibody expression in
mammalian cells unless the heavy chain is truncated to remove
C.sub.H2 and C.sub.H3 domains (King et al., Biochem. J. 281:317
(1992)). Thus, heavy chain assembly appears to promote disulfide
bond formation rather than vice versa. Taken together these
structural and functional data led to the hypothesis that antibody
heavy chain association is directed by the C.sub.H3 domains. It was
further speculated that the interface between C.sub.H3 domains
might be engineered to promote formation of heteromultimers of
different heavy chains and hinder assembly of corresponding
homomultimers. The experiments described herein demonstrated that
it was possible to promote the formation of heteromultimers over
homomultimers using this approach. Thus, it is possible to generate
a polypeptide fusion comprising a polypeptide of interest and the
C.sub.H3 domain of an antibody to form a first or second
polypeptide. The preferred C.sub.H3 domain is derived from an IgG
antibody, such as an human IgG.sub.1.
[0118] Those interface residues which can potentially constitute
candidates for forming the protuberance or cavity are identified.
It is preferable to select "buried" residues to be replaced. To
determine whether a residue is buried, the surface accessibility
program of Lee et al. J. Mol. Biol. 55:379-400 (1971) can be used
to calculate the solvent accessibility (SA) of residues in the
interface. Then, the SA for the residues of each of the first and
second polypeptide can be separately calculated after removal of
the other polypeptide. The difference in SA of each residue between
the monomer and dimer forms of the interface can then be calculated
using the equation: SA (dimer)-SA (monomer). This provides a list
of residues which lose SA on formation of the dimer. The SA of each
residue in the dimer is compared to the theoretical SA of the same
amino acid in the tripeptide Gly-X-Gly, where X=the amino acid of
interest (Rose et al. Science 229:834-838 (1985)). Residues which
(a) lost SA in the dimer compared to the monomer and (b) had an SA
less than 26% of that in their corresponding tripeptide are
considered as interface residues. Two categories may be delineated:
those which have an SA<10% compared to their corresponding
tripeptide (i.e. "buried") and those which have 25%>SA>10%
compared to their corresponding tripeptide (i.e. "partially
buried") (see Table 1, below).
1TABLE 1 SA Lost Monomer .fwdarw. Dimer % Tripeptide Residue
Polypeptide Polypeptide Polypeptide Polypeptide No..sup..dagger. A
B A B Q347 22.1 31.0 25.0 26.5 Y349 79.8 83.9 5.2 5.7 L351 67.4
77.7 3.9 2.0 S354 53.4 52.8 11.3 11.7 E357 43.7 45.3 0.4 1.3 S364
21.5 15.1 0.5 1.4 T366 29.3 25.8 0.0 0.1 L368 25.5 29.7 1.0 1.1
K370 55.8 62.3 11.5 11.0 T394 64.0 58.5 0.6 1.4 V397 50.3 49.5 13.2
11.0 D399 39.7 33.7 5.7 5.7 F405 53.7 52.1 0.0 0.0 Y407 89.1 90.3
0.0 0.0 K409 86.8 92.3 0.7 0.6 T411 4.3 7.5 12.7 9.8
.sup..dagger.residue numbering as in IgG crystal structure
(Deisenhofer, Biochemistry 20:2361-2370 (1981)).
[0119] The effect of replacing residues on the polypeptide chain
structure can be studied using a molecular graphics modeling
program such as the Insight.TM. program (Biosym Technologies).
Using the program, those buried residues in the interface of the
first polypeptide which have a small side chain volume can be
changed to residues having a larger side chain volume (i.e. a
protuberance), for example. Then, the residues in the interface of
the second polypeptide which are in proximity to the protuberance
are examined to find a suitable residue for forming the cavity.
Normally, this residue will have a large side chain volume and is
replaced with a residue having a smaller side chain volume. In
certain embodiments, examination of the three-dimensional structure
of the interface will reveal a suitably positioned and dimensioned
protuberance on the interface of the first polypeptide or a cavity
on the interface of the second polypeptide. In these instances, it
is only necessary to model a single mutant, i.e., with a
synthetically introduced protuberance or cavity.
[0120] With respect to selecting potential original residues for
replacement where the first and second polypeptide each comprise a
C.sub.H3 domain, the C.sub.H3/C.sub.H3 interface of human IgG.sub.1
involves sixteen residues on each domain located on four
anti-parallel .beta.-strands which buries 1090 .ANG..sup.2 from
each surface (Deisenhofer, supra) and Miller, J. Mol. Biol. 216:965
(1990)). Mutations are preferably targeted to residues located on
the two central anti-parallel .beta.-strands. The aim is to
minimize the risk that the protuberances which are created can be
accommodated by protruding into surrounding solvent rather than by
compensatory cavities in the partner C.sub.H3 domain.
[0121] Once the preferred original/import residues are identified
by molecular modeling, the amino acid replacements are introduced
into the polypeptide using techniques which are well known in the
art. Normally the DNA encoding the polypeptide is genetically
engineered using the techniques described in Mutagenesis: a
Practical Approach, supra.
[0122] Oligonucleotide-mediated mutagenesis is a preferred method
for preparing substitution variants of the DNA encoding the first
or second polypeptide. This technique is well known in the art as
described by Adelman et al., DNA, 2:183 (1983). Briefly, first or
second polypeptide DNA is altered by hybridizing an oligonucleotide
encoding the desired mutation to a DNA template, where the template
is the single-stranded form of a plasmid or bacteriophage
containing the unaltered or native DNA sequence of heteromultimer.
After hybridization, a DNA polymerase is used to synthesize an
entire second complementary strand of the template that will thus
incorporate the oligonucleotide primer, and will code for the
selected alteration in the heteromultimer DNA.
[0123] Cassette mutagenesis can be performed as described Wells et
al. Gene 34:315 (1985) by replacing a region of the DNA of interest
with a synthetic mutant fragment generated by annealing
complimentary oligonucleotides. PCR mutagenesis is also suitable
for making variants of the first or second polypeptide DNA. While
the following discussion refers to DNA, it is understood that the
technique also finds application with RNA. The PCR technique
generally refers to the following procedure (see Erlich, Science,
252:1643-1650 (1991), the chapter by R. Higuchi, p. 61-70).
[0124] This invention also encompasses, in addition to the
protuberance or cavity mutations, amino acid sequence variants of
the heteromultimer which can be prepared by introducing appropriate
nucleotide changes into the heteromultimer DNA, or by synthesis of
the desired heteromultimer polypeptide. Such variants include, for
example, deletions from, or insertions or substitutions of,
residues within the amino acid sequences of the first and second
polypeptides forming the heteromultimer. Any combination of
deletion, insertion, and substitution is made to arrive at the
final construct, provided that the final construct possesses the
desired antigen-binding characteristics. The amino acid changes
also may alter post-translational processes of the heteromultimer,
such as changing the number or position of glycosylation sites.
[0125] A useful method for identification of certain residues or
regions of the heteromultimer polypeptides that are preferred
locations for mutagenesis is called "alanine scanning mutagenesis,"
as described by Cunningham and Wells, Science, 244:1081-1085
(1989). Here, a residue or group of target residues are identified
(e.g. charged residues such as arg, asp, his, lys, and glu) and
replaced by a neutral or negatively charged amino acid (most
preferably alanine or polyalanine) to affect the interaction of the
amino acids with the surrounding aqueous environment in or outside
the cell. Those domains demonstrating functional sensitivity to the
substitutions then are refined by introducing further or other
variants at or for the sites of substitution. Thus, while the site
for introducing an amino acid sequence variation is predetermined,
the nature of the mutation per se need not be predetermined.
[0126] Normally the mutations will involve conservative amino acid
replacements in non-functional regions of the heteromultimer.
Exemplary mutations are shown in Table 2.
2 TABLE 2 Original Exemplary Preferred Residue Substitutions
Substitutions Ala (A) Val; Leu; Ile Val Arg (R) Lys; Gln; Asn Lys
Asn (N) Gln; His; Lys; Gln Arg Asp (D) Glu Glu Cys (C) Ser Ser Gln
(Q) Asn Asn Glu (E) Asp Asp Gly (G) Pro; Ala Ala His (H) Asn; Gln;
Lys; Arg Arg Ile (I) Leu; Val; Met; Leu Ala; Phe; Norleucine Leu
(L) Norleucine; Ile; Ile Val; Met; Ala; Phe Lys (K) Arg; Gln; Asn
Arg Met (M) Leu; Phe; Ile Leu Phe (F) Leu; Val; Ile; Leu Ala; Tyr
Pro (P) Ala Ala Ser (S) Thr Thr Thr (T) Ser Ser Trp (W) Tyr; Phe
Tyr Tyr (Y) Trp; Phe; Thr; Phe Ser Val (V) Ile; Leu; Met; Leu Phe;
Ala; Norleucine
[0127] Covalent modifications of the heteromultimer polypeptides
are included within the scope of this invention. Covalent
modifications of the heteromultimer can be introduced into the
molecule by reacting targeted amino acid residues of the
heteromultimer or fragments thereof with an organic derivatizing
agent that is capable of reacting with selected side chains or the
N- or C-terminal residues. Another type of covalent modification of
the heteromultimer polypeptide included within the scope of this
invention comprises altering the native glycosylation pattern of
the polypeptide. By altering is meant deleting one or more
carbohydrate moieties found in the original heteromultimer, and/or
adding one or more glycosylation sites that are not present in the
original heteromultimer. Addition of glycosylation sites to the
heteromultimer polypeptide is conveniently accomplished by altering
the amino acid sequence such that it contains one or more 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 original heteromultimer sequence (for O-linked
glycosylation sites). For ease, the heteromultimer amino acid
sequence is preferably altered through changes at the DNA level,
particularly by mutating the DNA encoding the heteromultimer
polypeptide at preselected bases such that codons are generated
that will translate into the desired amino acids. Another means of
increasing the number of carbohydrate moieties on the
heteromultimer polypeptide is by chemical or enzymatic coupling of
glycosides to the polypeptide. These methods are described in WO
87/05330 published Sep. 11, 1987, and in Aplin and Wriston, CRC
Crit. Rev. Biochem., pp. 259-306 (1981). Removal of carbohydrate
moieties present on the heteromultimer may be accomplished
chemically or enzymatically.
[0128] Another type of covalent modification of heteromultimer
comprises linking the heteromultimer polypeptide 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. Nos. 4,640,835; 4,496,689; 4,301,144; 4,670,417;
4,791,192 or 4,179,337.
[0129] Since it is often difficult to predict in advance the
characteristics of a variant heteromultimer, it will be appreciated
that some screening of the recovered variant will be needed to
select the optimal variant.
[0130] 3. Expression of Heteromultimer Having Common Light
Chains
[0131] Following mutation of the DNA and selection of the common
light chain as disclosed herein, the DNA encoding the molecules is
expressed using recombinant techniques which are widely available
in the art. Often, the expression system of choice will involve a
mammalian cell expression vector and host so that the
heteromultimer is appropriately glycosylated (e.g. in the case of
heteromultimers comprising antibody domains which are
glycosylated). However, the molecules can also be produced in the
prokaryotic expression systems elaborated below. Normally, the host
cell will be transformed with DNA encoding both the first
polypeptide, the second polypeptide, the common light chain
polypeptide, and other polypeptide(s) required to form the
heteromultimer, on a single vector or independent vectors. However,
it is possible to express the first polypeptide, second
polypeptide, and common light chain polypeptide (the heteromultimer
components) in independent expression systems and couple the
expressed polypeptides in vitro.
[0132] The nucleic acid(s) (e.g., cDNA or genomic DNA) encoding the
heteromultimer and common light chain is inserted into a replicable
vector for further cloning (amplification of the DNA) or for
expression. 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.
[0133] The polypeptides of the heteromultimer components may be
produced as fusion polypeptides with a signal sequence or other
polypeptide having a specific cleavage site at the N-terminus of
the mature protein or polypeptide. In general, the signal sequence
may be a component of the vector, or it may be a part of the DNA
that is inserted into the vector. 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, the signal sequence may be 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, the latter described in U.S. Pat. No.
5,010,182 issued Apr. 23, 1991), or acid phosphatase leader, the C.
albicans glucoamylase leader (EP 362,179 published Apr. 4, 1990),
or the signal described in WO 90/13646 published Nov. 15, 1990. In
mammalian cell expression the native signal sequence (e.g., the
antibody or adhesin presequence that normally directs secretion of
these molecules from human cells in vivo) is satisfactory, although
other mammalian signal sequences may be suitable as well as viral
secretory leaders, for example, the herpes simplex gD signal. The
DNA for such precursor region is ligated in reading frame to DNA
encoding the polypeptides forming the heteromultimer.
[0134] 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).
[0135] Expression and cloning vectors should 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. 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
(Southern et al., J. Molec. Appl. Genet. 1:327 (1982)),
mycophenolic acid (Mulligan et al., Science 209:1422 (1980)) or
hygromycin (Sugden et al., Mol. Cell. Biol. 5:410-413 (1985)). The
three examples given above employ bacterial genes under eukaryotic
control to convey resistance to the appropriate drug G418 or
neomycin (geneticin), xgpt (mycophenolic acid), or hygromycin,
respectively.
[0136] Another example of suitable selectable markers for mammalian
cells are those that enable the identification of cells competent
to take up the heteromultimer nucleic acid, such as DHFR or
thymidine kinase. The mammalian cell transformants are placed under
selection pressure that only the transformants are uniquely adapted
to survive by virtue of having taken up the marker. Selection
pressure is imposed by culturing the transformants under conditions
in which the concentration of selection agent in the medium is
successively changed, thereby leading to amplification of both the
selection gene and the DNA that encodes heteromultimer. Increased
quantities of heteromultimer are synthesized from the amplified
DNA. Other examples of amplifiable genes include metallothionein-I
and -II, preferably primate metallothionein genes, adenosine
deaminase, ornithine decarboxylase, etc.
[0137] 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, prepared and propagated as described by Urlaub and
Chasin, Proc. Natl. Acad. Sci. USA 77:4216 (1980). The transformed
cells are then exposed to increased levels of methotrexate. This
leads to the synthesis of multiple copies of the DHFR gene, and,
concomitantly, multiple copies of other DNA comprising the
expression vectors, such as the DNA encoding the components of the
heteromultimer. This amplification technique can be used with any
otherwise suitable host, e.g., ATCC No. CCL61 CHO-K1,
notwithstanding the presence of endogenous DHFR if, for example, a
mutant DHFR gene that is highly resistant to Mtx is employed (EP
117,060).
[0138] Alternatively, host cells (particularly wild-type hosts that
contain endogenous DHFR) transformed or co-transformed with DNA
sequences encoding heteromultimer, 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.
[0139] 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); Kingsman et al., Gene 7:141 (1979); or Tschemper et al.,
Gene 10:157 (1980)). 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.
[0140] In addition, vectors derived from the 1.6 .mu.m circular
plasmid pKD1 can be used for transformation of Kluyveromyces
yeasts. Bianchi et al., Curr. Genet. 12:185 (1987). More recently,
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)).
[0141] Expression and cloning vectors usually contain a promoter
that is recognized by the host organism and is operably linked to
the heteromultimer nucleic acid. A large number of promoters
recognized by a variety of potential host cells are well known.
These promoters are operably linked to heteromultimer-encoding DNA
by removing the promoter from the source DNA by restriction enzyme
digestion and inserting the isolated promoter sequence into the
vector.
[0142] Promoters suitable for use with prokaryotic hosts include
the .beta.-lactamase and lactose promoter systems (Chang et al.,
Nature 275:615 (1978); and Goeddel et al., Nature 281:544 (1979)),
alkaline phosphatase, a tryptophan (trp) promoter system (Goeddel,
Nucleic Acids Res., 8:4057 (1980) and EP 36,776) and hybrid
promoters such as the tac promoter (deBoer et al., Proc. Natl.
Acad. Sci. USA 80:21-25 (1983)). However, other known bacterial
promoters are suitable. Their nucleotide sequences have been
published, thereby enabling a skilled worker operably to ligate
them to DNA encoding the heteromultimer (Siebenlist et al., Cell
20:269 (1980)) using linkers or adaptors to supply any required
restriction sites. Promoters for use in bacterial systems also will
contain a Shine-Dalgarno (S.D.) sequence operably linked to the DNA
encoding the heteromultimer.
[0143] 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 CXCAAT region where X 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.
[0144] Examples of suitable promoting sequences for use with yeast
hosts include the promoters for 3-phosphoglycerate kinase (Hitzeman
et al., J. Biol. Chem. 255:2073 (1980)) or other glycolytic enzymes
(Hess et al., J. Adv. Enzyme Reg. 7:149 (1968); and Holland,
Biochemistry 17:4900 (1978)), such as enolase,
glyceraldehyde-3-phosphate dehydrogenase, hexokinase, pyruvate
decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase,
3-phosphoglycerate mutase, pyruvate kinase, triosephosphate
isomerase, phosphoglucose isomerase, and glucokinase.
[0145] 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
Hitzeman et al., EP 73,657A. Yeast enhancers also are
advantageously used with yeast promoters.
[0146] Heteromultimer 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 (UK
2,211,504 published Jul. 5, 1989), 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 or from heat-shock
promoters.
[0147] 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. Fiers et al., Nature
273:113 (1978); Mulligan and Berg, Science 209:1422-1427 (1980);
Pavlakis et al., Proc. Natl. Acad. Sci. USA 78:7398-7402 (1981).
The immediate early promoter of the human cytomegalovirus is
conveniently obtained as a HindIII E restriction fragment.
Greenaway et al., Gene 18:355-360 (1982). 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. See also Gray et
al., Nature 295:503-508 (1982) on expressing cDNA encoding immune
interferon in monkey cells; Reyes et al., Nature 297:598-601 (1982)
on expression of human .beta.-interferon cDNA in mouse cells under
the control of a thymidine kinase promoter from herpes simplex
virus; Canaani and Berg, Proc. Natl. Acad. Sci. USA 79:5166-5170
(1982) on expression of the human interferon l gene in cultured
mouse and rabbit cells; and Gorman et al., Proc. Natl. Acad. Sci.
USA 79:6777-6781 (1982) on expression of bacterial CAT sequences in
CV-1 monkey kidney cells, chicken embryo fibroblasts, Chinese
hamster ovary cells, HeLa cells, and mouse NIH-3T3 cells using the
Rous sarcoma virus long terminal repeat as a promoter.
[0148] Transcription of DNA encoding the heteromultimer components
by higher eukaryotes is often increased by inserting an enhancer
sequence into the vector. Enhancers are relatively orientation and
position independent, having been found 5' (Laimins et al., Proc.
Natl. Acad. Sci. USA 78:993 (1981)) and 3' (Lusky et al., Mol. Cell
Bio. 3:1108 (1983)) to the transcription unit, within an intron
(Banerji et al., Cell 33:729 (1983)), as well as within the coding
sequence itself (Osborne et al., Mol. Cell Bio. 4:1293 (1984)).
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 heteromultimer-encoding sequence, but is
preferably located at a site 5' from the promoter.
[0149] 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
heteromultimer.
[0150] Construction of suitable vectors containing one or more of
the above listed components employs standard ligation techniques.
Isolated plasmids or DNA fragments are cleaved, tailored, and
religated in the form desired to generate the plasmids
required.
[0151] For analysis to confirm correct sequences in plasmids
constructed, the ligation mixtures are used to transform E. coli
K12 strain 294 (ATCC 31,446) and successful transformants selected
by ampicillin or tetracycline resistance where appropriate.
Plasmids from the transformants are prepared, analyzed by
restriction endonuclease digestion, and/or sequenced by the method
of Messing et al., Nucleic Acids Res. 9:309 (1981) or by the method
of Maxam et al., Methods in Enzymology 65:499 (1980).
[0152] Particularly useful in the practice of this invention are
expression vectors that provide for the transient expression in
mammalian cells of DNA encoding heteromultimer. In general,
transient expression involves the use of an expression vector that
is able to replicate efficiently in a host cell, such that the host
cell accumulates many copies of the expression vector and, in turn,
synthesizes high levels of a desired polypeptide encoded by the
expression vector. Sambrook et al., supra, pp. 16.17-16.22.
Transient expression systems, comprising a suitable expression
vector and a host cell, allow for the convenient positive
identification of polypeptides encoded by cloned DNAs, as well as
for the rapid screening of heteromultimers having desired binding
specificities/affinities or the desired gel migration
characteristics relative to heteromultimers or homomultimers
lacking the non-natural disulfide bonds generated according to the
instant invention.
[0153] Other methods, vectors, and host cells suitable for
adaptation to the synthesis of the heteromultimer in recombinant
vertebrate cell culture are described in Gething et al., Nature
293:620-625 (1981); Mantei et al., Nature 281:40-46 (1979); EP
117,060; and EP 117,058. A particularly useful plasmid for
mammalian cell culture expression of the heteromultimer is pRK5 (EP
307,247) or pSVI6B (PCT pub. no. WO 91/08291 published June 13,
1991).
[0154] The choice of host cell line for the expression of
heteromultimer depends mainly on the expression vector. Another
consideration is the amount of protein that is required. Milligram
quantities often can be produced by transient transfections. For
example, the adenovirus EIA-transformed 293 human embryonic kidney
cell line can be transfected transiently with pRK5-based vectors by
a modification of the calcium phosphate method to allow efficient
heteromultimer expression. CDM8-based vectors can be used to
transfect COS cells by the DEAE-dextran method (Aruffo et al., Cell
61:1303-1313 (1990); and Zettmeissl et al., DNA Cell Biol. (US)
9:347-353 (1990)). If larger amounts of protein are desired, the
immunoadhesin can be expressed after stable transfection of a host
cell line. For example, a pRK5-based vector can be introduced into
Chinese hamster ovary (CHO) cells in the presence of an additional
plasmid encoding dihydrofolate reductase (DHFR) and conferring
resistance to G418. Clones resistant to G418 can be selected in
culture. These clones are grown in the presence of increasing
levels of DHFR inhibitor methotrexate and clones are selected in
which the number of gene copies encoding the DHFR and
heteromultimer sequences is co-amplified. If the immunoadhesin
contains a hydrophobic leader sequence at its N-terminus, it is
likely to be processed and secreted by the transfected cells. The
expression of immunoadhesins with more complex structures may
require uniquely suited host cells. For example, components such as
light chain or J chain may be provided by certain myeloma or
hybridoma host cells (Gascoigne et al., supra; and Martin et al.,
J. Virol. 67:3561-3568 (1993)).
[0155] Other suitable host cells for cloning or expressing the
vectors herein are prokaryote, yeast, or other 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 Apr. 12, 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.
Strain W3110 is a particularly preferred host or parent host
because it is a common host strain for recombinant DNA product
fermentations. Preferably, the host cell should secrete minimal
amounts of proteolytic enzymes. For example, strain W3110 may be
modified to effect a genetic mutation in the genes encoding
proteins, with examples of such hosts including E. coli W3110
strain 27C7. The complete genotype of 27C7 is tonA.DELTA. ptr3
phoA.DELTA.E15 .DELTA.(argF-lac)169 ompT.DELTA. degP41kan.sup.r.
Strain 27C7 was deposited on Oct. 30, 1991 in the American Type
Culture Collection as ATCC No. 55,244. Alternatively, the strain of
E. coli having mutant periplasmic protease disclosed in U.S. Pat.
No. 4,946,783 issued Aug. 7, 1990 may be employed. Alternatively,
methods of cloning, e.g., PCR or other nucleic acid polymerase
reactions, are suitable.
[0156] In addition to prokaryotes, eukaryotic microbes such as
filamentous fungi or yeast are suitable cloning or expression hosts
for heteromultimer-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 (Beach and Nurse, Nature 290:140
(1981); EP 139,383 published May 2, 1985); Kluyveromyces hosts
(U.S. Pat. No. 4,943,529; Fleer et al., supra) such as, e.g., K.
lactis (MW98-8C, CBS683, CBS4574; Louvencourt et al., J.
Bacteriol., 737 (1983)), 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; Van den Berg et al.,
supra), K. thermotolerans, and K. marxianus; yarrowia (EP 402,226);
Pichia pastoris (EP 183,070; Sreekrishna et al., J. Basic
Microbiol. 28:265-278 (1988)); Candida; Trichoderma reesia (EP
244,234); Neurospora crassa (Case et al., Proc. Natl. Acad. Sci.
USA 76:5259-5263 (1979)); Schwanniomyces such as Schwanniomyces
occidentalis (EP 394,538 published Oct. 31, 1990); and filamentous
fungi such as, e.g., Neurospora, Penicillium, Tolypocladium (WO
91/00357 published Jan. 10, 1991), and Aspergillus hosts such as A.
nidulans (Ballance et al., Biochem. Biophys. Res. Commun.
112:284-289 (1983); Tilburn et al., Gene 26:205-221 (1983); Yelton
et al., Proc. Natl. Acad. Sci. USA 81:1470-1474 (1984)) and A.
niger (Kelly and Hynes, EMBO J. 4:475-479 (1985)).
[0157] Suitable host cells for the expression of glycosylated
heteromultimer are derived from multicellular organisms. Such host
cells are capable of complex processing and glycosylation
activities. In principle, any higher eukaryotic cell culture is
workable, whether from vertebrate or invertebrate culture. 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. See, e.g., Luckow et al., Bio/Technology
6:47-55 (1988); Miller et al., in Genetic Engineering, Setlow et
al., eds., Vol. 8 (Plenum Publishing, 1986), pp. 277-279; and Maeda
et al., Nature 315:592-594 (1985). 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.
[0158] Plant cell cultures of cotton, corn, potato, soybean,
petunia, tomato, and tobacco can be utilized as hosts. Typically,
plant cells are transfected by incubation with certain strains of
the bacterium Agrobacterium tumefaciens, which has been previously
manipulated to contain the heteromultimer DNA. During incubation of
the plant cell culture with A. tumefaciens, the DNA encoding the
heteromultimer is transferred to the plant cell host such that it
is transfected, and will, under appropriate conditions, express the
heteromultimer DNA. In addition, regulatory and signal sequences
compatible with plant cells are available, such as the nopaline
synthase promoter and polyadenylation signal sequences. Depicker et
al., J. Mol. Appl. Gen. 1:561 (1982). In addition, DNA segments
isolated from the upstream region of the T-DNA 780 gene are capable
of activating or increasing transcription levels of
plant-expressible genes in recombinant DNA-containing plant tissue.
EP 321,196 published Jun. 21, 1989.
[0159] The preferred hosts are vertebrate cells, and propagation of
vertebrate cells in culture (tissue culture) has become a routine
procedure in recent years (Tissue Culture, Academic Press, Kruse
and Patterson, editors (1973)). 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 and Chasin, 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); TRI 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).
[0160] Host cells are transfected with the above-described
expression or cloning vectors of this invention and cultured in
conventional nutrient media modified as appropriate for inducing
promoters, selecting transformants, or amplifying the genes
encoding the desired sequences. Depending on the host cell used,
transfection is done using standard techniques appropriate to such
cells. The calcium treatment employing calcium chloride, as
described in section 1.82 of Sambrook et al., supra, or
electroporation is generally used for prokaryotes or other cells
that contain substantial cell-wall barriers. Infection with
Agrobacterium tumefaciens is used for transformation of certain
plant cells, as described by Shaw et al., Gene 23:315 (1983) and WO
89/05859 published Jun. 29, 1989. In addition, plants may be
transfected using ultrasound treatment as described in WO 91/00358
published Jan. 10, 1991.
[0161] For mammalian cells without such cell walls, the calcium
phosphate precipitation method of Graham and van der Eb, Virology
52:456-457 (1978) is preferred. General aspects of mammalian cell
host system transformations have been described by Axel in U.S.
Pat. No. 4,399,216 issued Aug. 16, 1983. Transformations into yeast
are typically carried out according to the method of Van Solingen
et al., J. Bact. 130:946 (1977) and Hsiao et al., Proc. Natl. Acad.
Sci. (USA) 76:3829 (1979). However, other methods for introducing
DNA into cells, such as by nuclear microinjection, electroporation,
bacterial protoplast fusion with intact cells, or polycations,
e.g., polybrene, polyornithine, etc., may also be used. For various
techniques for transforming mammalian cells, see Keown et al.,
Methods in Enzymology (1989), Keown et al., Methods in Enzymology
185:527-537 (1990), and Mansour et al., Nature 336:348-352
(1988).
[0162] Prokaryotic cells used to produce the heteromultimer
polypeptide of this invention are cultured in suitable media as
described generally in Sambrook et al., supra.
[0163] The mammalian host cells used to produce the heteromultimer
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 and
Wallace, Meth. Enz. 58:44 (1979), Barnes and Sato, Anal. Biochem.
102:255 (1980), U.S. Pat. Nos. 4,767,704; 4,657,866; 4,927,762; or
4,560,655; WO 90/03430; WO 87/00195; U.S. Pat. Re. 30,985; or U.S.
Pat. No. 5,122,469, the disclosures of all of which are
incorporated herein by reference, 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), nucleosides (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.
[0164] In general, principles, protocols, and practical techniques
for maximizing the productivity of mammalian cell cultures can be
found in Mammalian Cell Biotechnology: a Practical Approach, M.
Butler, ed., IRL Press, 1991.
[0165] The host cells referred to in this disclosure encompass
cells in culture as well as cells that are within a host
animal.
[0166] 4. Recovery of the Heteromultimer
[0167] The heteromultimer preferably is generally recovered from
the culture medium as a secreted polypeptide, although it also may
be recovered from host cell lysate when directly produced without a
secretory signal. If the heteromultimer is membrane-bound, it can
be released from the membrane using a suitable detergent solution
(e.g. Triton-X 100).
[0168] When the heteromultimer is produced in a recombinant cell
other than one of human origin, it is completely free of proteins
or polypeptides of human origin. However, it is necessary to purify
the heteromultimer from recombinant cell proteins or polypeptides
to obtain preparations that are substantially homogeneous as to
heteromultimer. As a first step, the culture medium or lysate is
normally centrifuged to remove particulate cell debris.
[0169] Heterodimers having antibody constant domains can be
conveniently purified by hydroxylapatite chromatography, gel
electrophoresis, dialysis, or affinity chromatography, with
affinity chromatography being the preferred purification technique.
Where the heteromultimer 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 Sepharose, 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 polypeptide to be recovered. The suitability of
protein A as an affinity ligand depends on the species and isotype
of the immunoglobulin Fc domain that is used in the chimera.
Protein A can be used to purify immunoadhesins 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. The conditions
for binding an immunoadhesin to the protein A or G affinity column
are dictated entirely by the characteristics of the Fc domain; that
is, its species and isotype. Generally, when the proper ligand is
chosen, efficient binding occurs directly from unconditioned
culture fluid. One distinguishing feature of immunoadhesins is
that, for human .gamma.1 molecules, the binding capacity for
protein A is somewhat diminished relative to an antibody of the
same Fc type. Bound immunoadhesin can be efficiently eluted either
at acidic pH (at or above 3.0), or in a neutral pH buffer
containing a mildly chaotropic salt. This affinity chromatography
step can result in a heterodimer preparation that is >95%
pure.
[0170] 5. Uses for a Heteromultimeric Multispecific Antibody Having
Common Light Chains
[0171] Many therapeutic applications for the heteromultimer are
contemplated. For example, the heteromultimer can be used for
redirected cytotoxicity (e.g. to kill tumor cells), as a vaccine
adjuvant, for delivering thrombolytic agents to clots, for
converting enzyme activated prodrugs at a target site (e.g. a
tumor), for treating infectious diseases, targeting immune
complexes to cell surface receptors, or for delivering immunotoxins
to tumor cells. For example, tumor vasculature targeting has been
accomplished by targeting a model endothelial antigen, class II
major histocompatibility complex, with an antibody-ricin
immunotoxin (Burrows, F. J. and Thorpe, P. E. (1993) Proc Natl Acad
Sci USA 90:8996-9000). Significantly greater efficacy was achieved
by combining the anti-endothelial immunotoxin with a second
immunotoxin directed against the tumor cells themselves (Burrows,
F. J. and Thorpe, P. E. (1993) supra). Recently, tissue factor was
successfully targeted to tumor vasculature using a bispecific
antibody, triggering local thrombosis that resulted in significant
anti-tumor efficacy (Huang, X. et al. (1997) Science 275:547-550).
In addition, bispecific diabodies have been used successfully to
direct cytotoxic T-cells to kill target breast tumor cells and
B-cell lymphoma cells in vitro (Zhu, Z. et al. (1996)
Bio/Technology 14:192-196; and Holliger, P. et al. (1996) Protein
Engin. 9:299-305).
[0172] Therapeutic formulations of the heteromultimer are prepared
for storage by mixing the heteromultimer 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
cake 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; low molecular weight (less than about 10 residues)
polypeptides; proteins, such as serum albumin, gelatin, or
immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone;
amino acids such as glycine, glutamine, asparagine, arginine or
lysine; monosaccharides, disaccharides, and other carbohydrates
including glucose, mannose, or dextrins; chelating agents such as
EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming
counterions such as sodium; and/or nonionic surfactants such as
Tween, Pluronics or polyethylene glycol (PEG).
[0173] The heteromultimer also may be entrapped in microcapsules
prepared, for example, by coacervation techniques or by interfacial
polymerization (for example, hydroxymethylcellulose or
gelatin-microcapsules and poly-[methylmethacylate] microcapsules,
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, supra.
[0174] The heteromultimer to be used for in vivo administration
must be sterile. This is readily accomplished by filtration through
sterile filtration membranes, prior to or following lyophilization
and reconstitution. The heteromultimer ordinarily will be stored in
lyophilized form or in solution.
[0175] Therapeutic heteromultimer compositions generally are placed
into a container having a sterile access port, for example, an
intravenous solution bag or vial having a stopper pierceable by a
hypodermic injection needle.
[0176] The route of heteromultimer administration is in accord with
known methods, e.g., injection or infusion by intravenous,
intraperitoneal, intracerebral, intramuscular, intraocular,
intraarterial, or intralesional routes, or by sustained release
systems as noted below. The heteromultimer is administered
continuously by infusion or by bolus injection.
[0177] Suitable examples of sustained-release preparations include
semipermeable matrices of solid hydrophobic polymers containing the
protein, which matrices are in the form of shaped articles, e.g.,
films, or microcapsules. Examples of sustained-release matrices
include polyesters, hydrogels (e.g.,
poly(2-hydroxyethyl-methacrylate) as described by Langer et al., J.
Biomed. Mater. Res. 15:167-277 (1981) and Langer, Chem. Tech.
12:98-105 (1982) or poly(vinylalcohol)), polylactides (U.S. Pat.
No. 3,773,919, EP 58,481), copolymers of L-glutamic acid and gamma
ethyl-L-glutamate (Sidman et al., Biopolymers 22:547-556 (1983)),
non-degradable ethylene-vinyl acetate (Langer et al., supra),
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 (EP 133,988).
[0178] 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 proteins 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 protein 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.
[0179] Sustained-release heteromultimer compositions also include
liposomally entrapped heteromultimer. Liposomes containing
heteromultimer are prepared by methods known per se: DE 3,218,121;
Epstein et al., Proc. Natl. Acad. Sci. USA 82:3688-3692 (1985);
Hwang et al., Proc. Natl. Acad. Sci. USA 77:4030-4034 (1980); EP
52,322; EP 36,676; EP 88,046; EP 143,949; EP 142,641; Japanese
patent application 83-118008; U.S. Pat. Nos. 4,485,045 and
4,544,545; and EP 102,324. Ordinarily the liposomes are of the
small (about 200-800 Angstroms) unilamellar type in which the lipid
content is greater than about 30 mol. % cholesterol, the selected
proportion being adjusted for the optimal heteromultimer
therapy.
[0180] An effective amount of heteromultimer to be employed
therapeutically will depend, for example, upon the therapeutic
objectives, the route of administration, and the condition of the
patient. Accordingly, it will be necessary for the therapist to
titer the dosage and modify the route of administration as required
to obtain the optimal therapeutic effect. A typical daily dosage
might range from about 1 .mu.g/kg to up to 10 mg/kg or more,
depending on the factors mentioned above. Typically, the clinician
will administer heteromultimer until a dosage is reached that
achieves the desired effect. The progress of this therapy is easily
monitored by conventional assays.
[0181] The heteromultimers described herein can also be used in
enzyme immunoassays. To achieve this, one arm of the heteromultimer
can be designed to bind to a specific epitope on the enzyme so that
binding does not cause enzyme inhibition, the other arm of the
heteromultimer can be designed to bind to the immobilizing matrix
ensuring a high enzyme density at the desired site. Examples of
such diagnostic heteromultimers include those having specificity
for IgG as well as ferritin, and those having binding specificities
for horse radish peroxidase (HRP) as well as a hormone, for
example.
[0182] The heteromultimers can be designed for use in two-site
immunoassays. For example, two bispecific heteromultimers are it
produced binding to two separate epitopes on the analyte
protein--one heteromultimer binds the complex to an insoluble
matrix, the other binds an indicator enzyme.
[0183] Heteromultimers can also be used for in vitro or in vivo
immunodiagnosis of various diseases such as cancer. To facilitate
this diagnostic use, one arm of the heteromultimer can be designed
to bind a tumor associated antigen and the other arm can bind a
detectable marker (e.g. a chelator which binds a radionuclide). For
example, a heteromultimer having specificities for the tumor
associated antigen CEA as well as a bivalent hapten can be used for
imaging of colorectal and thryroid carcinomas. Other
non-therapeutic, diagnostic uses for the heteromultimer will be
apparent to the skilled practitioner.
[0184] For diagnostic applications, at least one arm of the
heteromultimer typically will be labeled directly or indirectly
with a detectable moiety. The detectable moiety can be any one
which is capable of producing, either directly or indirectly, a
detectable signal. For example, the detectable moiety may be a
radioisotope, such a s .sup.3H, .sup.14C, .sup.32p, .sup.35S, or
.sup.125I; a fluorescent or chemiluminescent compound, such as
fluorescein isothiocyanate, rhodamine, or luciferin; or an enzyme,
such as alkaline phosphatase, beta-galactosidase or horseradish
peroxidase (HRP).
[0185] Any method known in the art for separately conjugating the
heteromultimer to the detectable moiety may be employed, including
those methods described by Hunter et al., Nature 144:945 (1962);
David et al., Biochemistry 13:1014 (1974); Pain et al., J. Immunol.
Meth. 40:219 (1981); and Nygren, J. Histochem. and Cytochem. 30:407
(1982)
[0186] The heteromultimers 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).
[0187] Competitive binding assays rely on the ability of a labeled
standard to compete with the test sample analyte for binding with a
limited amount of heteromultimer. The amount of analyte in the test
sample is inversely proportional to the amount of standard that
becomes bound to the heteromultimer. To facilitate determining the
amount of standard that becomes bound, the heteromultimers
generally are insolubilized before or after the competition, so
that the standard and analyte that are bound to the heteromultimers
may conveniently be separated from the standard and analyte which
remain unbound.
[0188] The heteromultimers are particularly useful for sandwich
assays which involve the use of two molecules, each capable of
binding to a different immunogenic portion, or epitope, of the
sample to be detected. In a sandwich assay, the test sample analyte
is bound by a first arm of the heteromultimer which is immobilized
on a solid support, and thereafter a second arm of the
heteromultimer binds to the analyte, thus forming an insoluble
three part complex. See, e.g., U.S. Pat. No. 4,376,110. The second
arm of the heteromultimer 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.
[0189] Below are examples of specific embodiments for carrying out
the present invention. The examples are offered for illustrative
purposes only, and are not intended to limit the scope of the
present invention in any way.
[0190] All publications, patents and patent applications cited
herein, whether supra or infra, are hereby incorporated by
reference in their entirety.
EXAMPLES
[0191] A strategy is presented for preparing Fc-containing BsAb
(FIG. 1C). In this strategy, we have engineered the C.sub.H3 domain
of antibody heavy chains so that they heterodimerize but do not
homodimerize. This was accomplished by installing inter-chain
disulfide bonds in the C.sub.H3 domain in conjunction with
sterically complimentary mutations obtained by rational design
(Ridgway et al., supra (1996)) and phage display selection as
described herein. Use of a single light chain for both antigen
binding specificities circumvents the problem of light chain
mispairing (FIG. 1A-1C). Antibodies with the same light chain were
readily isolated by panning a very large human scFv library
(Vaughan, T. J., et al., (1996) supra).
Example 1
[0192] Generation of Protuberance-into-cavity Heteromultimer
Immunoadhesins
[0193] The C.sub.H3 interface between the humanized
anti-CD3/CD4-IgG chimera previously described by Chamow et al. J.
Immunol. 153:4268 (1994) was engineered to maximize the percentage
of heteromultimers which could be recovered.
Protuberance-into-cavity and wild-type C.sub.H3 variants were
compared in their ability to direct the formation of a humanized
antibody-immunoadhesin chimera (Ab/Ia) anti-CD3/CD4-IgG.
[0194] Thus, mutations were constructed in the C.sub.H3 domain of
the humanized anti-CD3 antibody heavy chain and in CD4-IgG by
site-directed mutagenesis using mismatched oligonucleotides (Kunkel
et al., Methods Enzymol. 154:367 (1987) and P. Carter, in
Mutagenesis: a Practical Approach, M. J. McPherson, Ed., IRL Press,
Oxford, UK, pp. 1-25 (1991)) and verified by dideoxynucleotide
sequencing (Sanger et al., Proc. Natl. Acad. Sci. USA 74:5463
(1977)). See Table 3 below.
3 TABLE 3 C.sub.H3 of anti-CD3 C.sub.H3 of CD4-IgG Most Preferred
Mutants T366Y Y407T T366W Y407A F405A T394W Y407T T366Y T366Y:F405A
T394W:Y407T T366W:F405W T394S:Y407A F405W:Y407A T366W:T394S
Preferred Mutants F405W T394S
[0195] Residue T366 is within hydrogen-bonding distance of residue
Y407 on the partner C.sub.H3 domain. Indeed the principal
intermolecular contact to residue T366 is to residue Y407 and vice
versa. One protuberance-into-cavity pair was created by inverting
these residues with the reciprocal mutations of T366Y in one
C.sub.H3 domain and Y407T in the partner domain thus maintaining
the volume of side chains at the interface. Mutations are denoted
by the wild-type residue followed by the position using the Kabat
numbering system (Kabat et al. (1991) supra) and then the
replacement residue in single-letter code. Multiple mutations are
denoted by listing component single mutations separated by a
colon.
[0196] Phagemids encoding anti-CD3 light (L) and heavy (H) chain
variants (Shalaby et al., J. Exp. Med. 175:217 (1992) and Rodrigues
et al., Int. J. Cancer (Suppl.) 7:45 (1992)) were co-transfected
into human embryonic kidney cells, 293S, together with a CD4-IgG
variant encoding phagemid (Byrn et al., Nature 344:667 (1990)) as
previously described (Chamow et al., J. Immunol. 153:4268 (1994)).
The total amount of transfected phagemid DNAs was fixed whereas the
ratio of different DNAs was varied to maximize the yield of Ab/Ia
chimera. The ratio (by mass) of Ia : heavy chain : light chain
input DNAs (15 .mu.g total) was varied as follows: 8:1:3; 7:1:3;
6:1:3; 5:1:3; 4:1:3; 3:1:3; 1:0:0; 0:1:3.
[0197] The products were affinity purified using Staphylococcal
protein A (ProSep A, BioProcessing Ltd, UK) prior to analysis by
SDS-PAGE followed by scanning LASER densitometry. Excess light over
heavy chain DNA was used to avoid the light chain from being
limiting. The identity of products was verified by electroblotting
on to PVDF membrane (Matsudaira, J. Biol. Chem. 262:10035 (1987))
followed by amino terminal sequencing.
[0198] Co-transfection of phagemids for light chain together with
those for heavy chain and Ia incorporating wild-type C.sub.H3
resulted in a mixture of Ab/Ia chimera, IgG and Ia homodimer
products as expected (Chamow et al., J. Immunol. 153:4268 (1994)).
The larger the fraction of input DNA encoding antibody heavy plus
light chains or Ia the higher the fraction of corresponding
homodimers recovered. An input DNA ratio of 6:1:3 of Ia:H:L yielded
54.5% Ab/Ia chimera with similar fractions of Ia homodimer (22.5%)
and IgG (23.0%). These ratios are in good agreement with those
expected from equimolar expression of each chain followed by random
assortment of heavy chains with no bias being introduced by the
method of analysis: 50% Ab/Ia chimera, 25% Ia homodimer and 25%
IgG.
[0199] In contrast to chains containing wild-type C.sub.H3, Ab/Ia
chimera was recovered in yields of up to 92% from cotransfections
in which the anti-CD3 heavy chain and CD4-IgG Ia contained the
Y407T cavity and T366Y protuberance mutations, respectively.
Similar yields of antibody/immunoadhesin chimera were obtained if
these reciprocal mutations were installed with the protuberance on
the heavy chain and the cavity in the Ia. In both cases monomer was
observed for the chain containing the protuberance but not the
cavity. Without being limited to any one theory, it is believed
that the T366Y protuberance is more disruptive to homodimer
formation than the Y407T cavity. The fraction of Ab/Ia hybrid was
not significantly changed by increasing the size of both
protuberance and cavity (Ab T366W, Ia Y407A). A second protuberance
and cavity pair (Ab F405A, Ia T394W) yielded up to 71% Ab/Ia
chimera using a small fraction of Ia input DNA to offset the
unanticipated proclivity of the Ia T394W protuberance variant to
homodimerize. Combining the two independent
protuberance-into-cavity mutant pairs (Ab T366Y:F405A, Ia
T394W:Y407T) did not improve the yield of Ab/Ia hybrid over the Ab
T366Y, Ia Y407T pair.
[0200] The fraction of Ab/Ia chimera obtained with T366Y and Y407T
mutant pair was virtually independent of the ratio of input DNAs
over the range tested. Furthermore the contaminating species were
readily removed from the Ab/Ia chimera by ion exchange
chromatography (0-300 mM NaCl in 20 mM Tris-HCl, pH8.0) on a mono S
HR 5/5 column (Pharmacia, Piscataway, N.J.). This augurs well for
the preparation of larger quantities Ab/Ia chimeras using stable
cell lines where the relative expression levels of Ab and Ia are
less readily manipulated than in the transient expression
system.
[0201] The protuberance-into-cavity mutations identified are
anticipated to increase the potential applications of Fc-containing
BsAb by reducing the complexity of the mixture of products obtained
from a possible ten major species (Suresh et al., Methods Enzymol.
121:210 (1990)) down to four or less (FIGS. 1A-1B). It is expected
that the T366Y and Y407T mutant pair will be useful for generating
heteromultimers of other human IgG isotypes (such as IgG.sub.2,
IgG.sub.3 or IgG.sub.4) since T366 and Y407 are fully conserved and
other residues at the C.sub.H3 domain interface of IgG.sub.1, are
highly conserved.
Example 2
[0202] Generation of Non-naturally Occurring Disulfide Linkages in
Heteromultimeric Immunoadhesins
[0203] A. Design of C.sub.H3 Inter-chain Disulfide Bonds.
[0204] Three criteria were used to identify pairs of residues for
engineering a disulfide bond between partner C.sub.H3 domains: i)
The C.alpha. separation preferably is similar to those found in
natural disulfide bonds (5.0 to 6.8 .ANG.) (Srinivasan, N., et al.,
Int. J. Peptides Protein Res. 36:147-155 (1990)). Distances of up
to 7.6 .ANG. were permitted to allow for main chain movement and to
take into account the uncertainty of atomic positions in the low
resolution crystal structure (Deisenhofer, Biochemistry
20:2361-2370 (1981)). ii) The C.alpha. atoms should be on different
residues on the two C.sub.H3 domains. iii) The residues are
positioned to permit disulfide bonding (Srinivasan, N., et al.,
(1990) supra).
[0205] B. Modeling of Disulfide Bonds.
[0206] Disulfide bonds were modeled into the human IgG.sub.1 Fc
(Deisenhofer, supra) as described for humAb4D5-Fv (Rodrigues et
al., Cancer Res. 55:63-70 (1995)) using Insight II release 95.0
(Biosym/MSI).
[0207] C. Construction of C.sub.H3 Variants.
[0208] Mutations were introduced into the C.sub.H3 domain of a
humanized anti-CD3 heavy chain or CD4-IgG by site-directed
mutagenesis (Kunkel, et al., Methods Enzymol. 154:367-382 (1987))
using the following synthetic oligonucleotides:
4 Y349C, 5' CTCTTCCCGAGATGGGGGCAGGGTGCACACCTGTGG 3' (SEQ. ID NO: 1)
S354C, 5' CTCTTCCCGACATGGGGGCAG 3' (SEQ. ID NO: 2) E356C, 5'
GGTCATCTCACACCGGGATGG 3' (SEQ. ID NO: 3) E357C, 5'
CTTGGTCATACATTCACGGGATGG 3' (SEQ. ID NO: 4) L351C, 5'
CTCTTCCCGAGATGGGGGACAGGTGTACAC 3' (SEQ. ID NO: 5) D399C, 5'
GCCGTCGGAACACAGCACGGG 3' (SEQ. ID NO: 6) K392C, 5'
CTGGGAGTCTAGAACGGGAGGCGTGGTACAGTAGTTGTT 3' (SEQ. ID NO: 7) T394C,
5' GTCGGAGTCTAGAACGGGAGGACAGGTCTTGTA 3' (SEQ. ID NO: 8) V397C, 5'
GTCGGAGTCTAGACAGGGAGG 3' (SEQ. ID NO: 9) D399S, 5'
GCCGTCGGAGCTCAGCACGGG 3' (SEQ. ID NO: 10) K392S, 5'
GGGAGGCGTGGTGCTGTAGTTGTT 3' (SEQ. ID NO: 11) C231S:C234S
5'GTTCAGGTGCTGGGCTCGGTGGGCTTGTGTGAGTTTTG 3' (SEQ. ID NO: 12)
[0209] Mutations are denoted by the amino acid residue and number
(Eu numbering scheme of Kabat et al., supra (1991), followed by the
replacement amino acid. Multiple mutations are represented by the
single mutation separated by a colon. Mutants were verified by
dideoxynucleotide sequencing (Sanger et al., supra (1977)) using
Sequenase version 2.0 (United States Biochemicals, Cleveland,
Ohio).
[0210] D. An Inter-chain Disulfide Enhances Heterodimer
Formation.
[0211] Six pairs of molecules containing inter-chain disulfide
bonds in the C.sub.H3 domain ("disulfide-C.sub.H3" variants; v1-v6,
Table 4) were compared with parent molecules in their ability to
direct the formation of an Ab/Ia hybrid, anti-CD3/CD4-IgG (Chamow
et al., supra (1994)). Plasmids encoding CD4-IgG and anti-CD3 heavy
chain variants were co-transfected into 293S cells, along with an
excess of plasmid encoding the anti-CD3 light chain. The yield of
heterodimer was optimized by transfecting with a range of Ia:H
chain:L chain DNA ratios. The Ab/Ia heterodimer, IgG and Ia
homodimer products were affinity-purified using Staphylococcal
protein A and quantified by SDS-PAGE and scanning laser
densitometry (Ridgway et al., supra (1996)).
[0212] Each disulfide-C.sub.H3 pair gave rise to three major
species, similar to the parent molecules. However, Ab/Ia
heterodimer from disulfide-C.sub.H3 variants was shifted in
electrophoretic mobility, consistent with formation of an
inter-chain disulfide in the C.sub.H3 domain. Further evidence of
disulfide bond formation was provided by the inter-chain disulfides
in the hinge. Covalently bonded Ab/Ia hybrids were observed by
SDS-PAGE for disulfide-C.sub.H3 variants but not for molecules with
wildtype C.sub.H3 domains in which hinge cysteines were mutated to
serine. Disulfide-C.sub.H3 variants were prepared and designated
Y349C/S354'C, Y349C/E356'C, Y349C/E357'C, L351C/E354'C,
T394C/E397'C, and D399C/K392C. Only one variant (D399C/K392'C)
substantially increased the yield of Ab/Ia hybrid over wildtype
(76% vs. 52%, respectively) as determined by SDS-PAGE analysis of
the variants. Mutations are denoted by the amino acid residue and
number (Eu numbering scheme of Kabat et al. (1991) supra), followed
by the replacement amino acid. Mutations in the first and second
copies of C.sub.H3 come before and after the slash, respectively.
Residues in the second copy of C.sub.H3 are designated with a prime
('). This improvement apparently reflects disulfide bond formation
rather than replacement of residues K392 and D399, since the
mutations K392S/D399'S gave both a similar Ab/Ia yield and Ab/Ia
electrophoretic mobility relative to wildtype. Homodimers migrated
similarly to those with wildtype Fc domains, demonstrating
preferential engineered inter-chain disulfide bond formation in the
C.sub.H3 domain of heterodimers. All disulfide-C.sub.H3 variants
were expressed at approximately the same level as the parent
molecules in 293S cells.
[0213] E. Disulfides combined with protuberance-into-cavity
engineering increases the yield of heterodimer to 95%. The best
disulfide pair increased the percent of heterodimer to 76% and the
protuberance-into-cavity strategy increased the percent of
heterodimer to 87% (Table 4; see also Ridgway et al., (1996)
supra). These two strategies rely on different principles to
increase the probability of generating heterodimer. Therefore, we
combined the two strategies, anticipating further improvement in
the yield of heterodimer. Two of the modeled disulfides, containing
L351C or T394C, could potentially form disulfide-bonded homodimers
as well as disulfide-bonded heterodimers (L351C/S354'C and
T394C/V397'C), thus decreasing their utility. The remaining four
disulfide pairs were installed into the phage-selected heterodimer
(variants v9-v16) and assayed for the yield of heterodimer (Table
4). Yields of approximately 95% heterodimer were obtained. Again,
the heterodimer showed an electrophoretic mobility shift compared
to wildtype and v8 variants.
5TABLE 4 Yields of Heterodimers from C.sub.H3 Variants Yield of
Mutations heterodimer Variant Subunit A Subunit B (%) wildtype --
-- 52 v1 Y349C S354C 58 v2 Y349C E356C 61 v3 Y349C E357C 61 v4
L351C E354C 58 v5 T394C E397C 58 v6 D399C K392C 76 v7 D399S L392S
56 v8 T366W T366S:L368A:Y407V 87 v9 T366W:D399C
T366S:L368A:K392C:Y407V 87 v11 S354C:T366W Y349C:T366S:L368A:Y407V
94 v12 E356C:T366W Y349C:T366S:L368A:Y407V 96.sup.A v13 E357C:T366W
Y349C:T366S:L368A:Y407V 95 v14 T366W:K392C T366S:D399C:L368A:Y407V
91 v15 Y349C:T366W S354C:T366S:L368A:Y407V 96 v16 Y349C:T366W
E356C:T366S:L368A:Y407V 92 v17 Y349C:T366W E357C:T366S:L368A:Y407V
92 .sup.AApproximately half of the Ab/Ia heterodimer was disulfide
bonded and half was not.
Example 3
[0214] Structure-guided Phage Display Selection for Complementary
Mutations that Enhance Protein-protein Interaction in
Heteromultimers
[0215] The following strategy is useful in the selection of
complementary mutations in polypeptides that interact at an
interface via a multimerization domain. The strategy is illustrated
below as it applies to the selection of complementary
protuberance-into-cavity mutations. However, the example is not
meant to be limiting and the strategy may be similarly applied to
the selection of mutations appropriate for the formation of
non-naturally occurring disulfide bonds, leucine zipper motifs,
hydrophobic interactions, hydrophilic interactions, and the
like.
[0216] A. Phage Display Selection.
[0217] A phage display strategy was developed for the selection of
stable C.sub.H3 heterodimers and is diagrammed in FIG. 2. The
selection uses a protuberance mutant, T366W (Ridgway et al., supra
(1996)), fused to a peptide flag (gD peptide flag, for example,
Lasky, L. A. and Dowbenko, D. J. (1984) DNA 3:23-29; and Berman, P.
W., et al. (1985) Science 227:1490-1492) that is coexpressed with a
second copy of C.sub.H3 fused to M13 gene III protein. A library of
cavity mutants was created in this second copy of C.sub.H3 by
randomization of the closest neighboring residues to the
protuberance on the first C.sub.H3 domain. Phage displaying stable
C.sub.H3 heterodimers were then captured using an anti-flag Ab.
[0218] A C.sub.H3 phage display library of 1.1.times.10.sup.5
independent clones was constructed by replacement of a segment of
the natural C.sub.H3 gene with a PCR fragment. The fragment was
obtained by PCR amplification using degenerate primers to randomize
positions 366, 368 and 407 using standard techniques.
[0219] After 2 to 5 rounds of selection, the fraction of full
length clones was 90%, 60%, 50% and 10%, respectively, as judged by
agarose gel electrophoresis of single-stranded DNA. Phagemids
containing full length clones were gel-purified after 5 rounds of
selection. Two thousand transformants were obtained after
retransforming XL1-BLUE.TM. cells (Stratagene).
[0220] A mean of >10.sup.6 copies of each clone was used per
round of panning. Thus, numerous copies of each clone in the
library were likely available for selection, even though some
deletion mutants arose during panning.
[0221] After 7 rounds of panning, the C.sub.H3 mutants obtained
approached a consensus amino acid sequence at the randomized
residues. Virtually all clones had serine or threonine at residue
366 indicating a very strong preference for a .beta.-hydroxyl at
this position. A strong preference for hydrophobic residues was
observed for residues 368 and 407, with valine and alanine
predominating. Six different amino acid combinations were recovered
at least twice, including the triple mutant, T366S:L368A:Y407V,
which was recovered 11 times. None of these phage selectants has an
identical sequence to a previously designed heterodimer,
T366W/Y407'A (Ridgway, J. B. B., et al., (1996), supra. The phage
selectants may be less tightly packed than the wild-type C.sub.H3
homodimer as judged by a 40-80 .ANG..sup.3reduction in total side
chain volume of the domain interface residues.
[0222] C.sub.H3 variants encoded on the expression plasmid pAK19
(Carter et al. 1992) were introduced into E. coli strain 33B6,
expressed, and secreted from E. coli grown to high cell density in
a fermentor. The T366S:L368A:Y407V mutant purified by
DEAE-Sepharose FF, ABx and Resource S chromatography gave a single
major band following SDS-PAGE. Other C.sub.H3 variants were
recovered with similar purity. The molecular masses of wild-type
C.sub.H3 and T366S:L368A:Y407V, T366W and Y407A variants determined
by high resolution electrospray mass spectrometry were as
expected.
[0223] B. Phage-selected Heterodimer Stability.
[0224] The stability of C.sub.H3 heterodimers was first assessed by
titrating corresponding phage with guanidine hydrochloride,
followed by dilution and quantification of residual heterodimer by
enzyme-linked immunosorbent assay (ELISA). The guanidine
hydrochloride denaturation assay with C.sub.H3-phage provides a
means to screen selectants rapidly.
[0225] Phage were prepared from individual clones following 7
rounds of selection and also from the control vector, pRA1.
Briefly, phagemids in XL1-BLUE.TM. were used to inoculate 25 ml LB
broth containing 50 .mu.g/ml carbenicillin and 10 .mu.g/ml
tetracycline in the presence of 10.sup.9 pfu/ml M13K07 and
incubated overnight at 37.degree. C. The cells were pelleted by
centrifugation (6000 g, 10 min, 4.degree. C.) Phage were recovered
from the supernatant by precipitation with 5 ml 20% (w/v) PEG, 2.5
M NaCl followed by centrifugation (12000 g, 10 min, 4.degree. C.)
and then resuspended in 1 ml PBS. 180 .mu.l 0-6 M guanidine
hydrochloride in PBS was added to 20 .mu.l phage preparations and
incubated for 5.0 min at approximately .about.25.degree. C.
Aliquots (20 .mu.l) of each phage sample were then diluted 10-fold
with water. The presence of C.sub.H3 heterodimer was assayed by
ELISA using 5B6-coated plates and detecting the phage with an
anti-M13 polyclonal Ab conjugated to horseradish peroxidase, using
o-phenylenediamine as the substrate. The reaction was quenched by
the addition of 50 .mu.l 2.5 M H.sub.2SO.sub.4 and the absorbance
measured at 492 nm. The absorbance data were plotted against the
guanidine hydrochloride concentration during the melt and fitted to
a 4 parameter model by a non-linear least squares method using
Kaleidagraph 3.0.5 (Synergy Software).
[0226] The most frequently recovered heterodimer,
T366W/T366'S:L368'A:Y407- 'V, is similar in stability to other
phage-selected heterodimers. This phage-selected heterodimer is
significantly more stable than the designed heterodimer,
T366W/Y407'A but less stable than the wild-type C.sub.H3. All
C.sub.H3 variants, both individually and in combination, were found
to be dimers by size exclusion chromatography under the conditions
that these same molecules were studied by calorimetry (1.75 mg/ml,
in phosphate-buffered saline (PBS)). The only exception was the
T366S:L368A:Y407V mutant alone which had a slightly shorter
retention time than C.sub.H3 dimers.
[0227] A 1:1 mixture of T366W, protuberance, and T366S:L368A:Y407V,
cavity, mutants melts with a single transition at 69.4.degree. C.,
consistent with subunit exchange and formation of a stable
heterodimer. In contrast, the T366W protuberance homodimer is much
less stable than the T366W/T366'S:L368'A:Y407'V
protuberance-into-cavity heterodimer (.DELTA.T.sub.m=-15.0.degree.
C.). The T366S:L368A:Y407V cavity mutant on its own is prone to
aggregate upon heating and does not undergo a smooth melting
transition.
[0228] The designed cavity mutant, Y407A, melts at 58.8.degree. C.
and 65.4.degree. C. in the absence and presence of the T366W
protuberance mutant, respectively. This is consistent with subunit
exchange and formation of a T366W/Y407'A heterodimer that has
greater stability than either T366W (.DELTA.T.sub.m=11.0.degree.
C.) or Y407A (.DELTA.T.sub.m=6.6.degree. C.) homodimers. The
phage-selected heterodimer, T366W/T366'S:L368'A:Y407'V, is more
stable than the designed heterodimer, T366W/Y407'A,
(.DELTA.T.sub.m=4.0.degree. C.), but is less stable than the
wild-type C.sub.H3 homodimer (.DELTA.T.sub.m=-11.0.degree- .
C.).
[0229] C. Multimerization of a Phage-selected Antibody
Immunoadhesin (Ab/Ia) in vivo.
[0230] Phage-selected and designed C.sub.H3 mutants were compared
in their ability to direct the formation of an Ab/Ia hybrid,
anti-CD3/CD4-IgG in vivo (Chamow et al., (1994), supra. This was
accomplished by coexpression of humanized anti-CD3 light (L) and
heavy chains together with CD4-IgG. Formation of heterodimers and
homodimers was assessed by protein A purification followed by
SDS-PAGE and scanning laser densitometry (Ridgway, et al., (1996),
supra). Comparable yields of Ab/Ia hybrid were recovered from
cotransfections in which the anti-CD3 heavy chain contained the
designed protuberance mutation, T366W, and the Ia contained either
the phage-selected mutations, T366S:L368A:Y407V, or designed cavity
mutation, Y407A (FIG. 3).
[0231] Phage-selected and designed C.sub.H3 mutants were next
evaluated in their propensity to form homodimers. The protuberance
mutation, T366W, is apparently very disruptive to homodimerization
since cotransfection of corresponding antibody heavy and light
chains leads to an excess of HL monomers (may include non
disulfide-bonded IgG) over IgG. In contrast, IgG but no HL monomers
are observed for the same antibody containing wild-type C.sub.H3
domains. The cavity mutations, T366S:L368A:Y407V, are somewhat
disruptive to homodimerization since transfection of the
corresponding phagemid leads to a mixture of predominantly Ia
dimers with some Ia monomers. The cavity mutation, Y407A, is
minimally disruptive to homodimerization as judged by the presence
of Ia dimers but no Ia monomers following transfection of the
corresponding phagemid.
[0232] The phage display selection strategy described herein allows
the selection in favor of C.sub.H3 mutants that form stable
heterodimers and selection against mutants that form stable
homodimers. The counter selection against homodimers occurs because
"free" C.sub.H3 mutants will compete with the flagged C.sub.H3 knob
mutant for binding to available C.sub.H3 mutant-gene III fusion
protein. The free C.sub.H3 mutants arise as a result of the amber
mutation between the natural C.sub.H3 gene and M13 gene III. In an
amber suppressor host such as XL1-Blue, both C.sub.H3-gene III
fusion protein and corresponding free C.sub.H3 will be
secreted.
[0233] Guanidine hydrochloride denaturation proved to be a useful
tool for the preliminary screening of the stability of C.sub.H3
heterodimers on phage. Phage maintain infectivity for E. coli even
after exposure to 5 M guanidine hydrochloride (Figini et al., J.
Mol. Biol. 239:68-78 (1994)). Thus, guanidine may also be useful to
increase the stringency of mutant selection.
[0234] Rational design and screening of phage display libraries are
complementary approaches to remodeling a domain interface of a
homodimer to promote heterodimerization. In the case of C.sub.H3
domains, designed mutants identified domain interface residues that
could be recruited to promote heterodimerization. Phage display was
then used here to search permutations of 3 residues neighboring a
fixed protuberance for combinations that most efficiently form
heterodimers. Phage selectants are useful to facilitate further
rational redesign of the domain interface, while the phage
selection strategy described herein demonstrates its usefulness for
remodeling protein-protein interfaces.
Example 4
[0235] Generation and Assembly of Hetermultimeric Antibodies or
Antibody/Immunoadhesins having Common Light Chains
[0236] A. Identification of Antibodies that Share the Same Light
Chain: Comparison of Antibody Libraries Raised to Eleven
Antigens.
[0237] A large human single chain Fv (scFv) antibody library
(Vaughan et al. (1996), supra) was panned for antibodies specific
for eleven antigens including Axl(human receptor tyrosine kinase
ECD), GCSF-R (human granulocyte colony stimulating factor receptor
ECD), IgE (murine IgE), IgE-R (human IgE receptor .alpha.-chain),
MPL (human thrombopoietin receptor tyrosine kinase ECD), MusK
(human muscle specific receptor tyrosine kinase ECD), NpoR (human
orphan receptor NpoR ECD), Rse (human receptor tyrosine kinase,
Rse, ECD), HER3 (human receptor tyrosine kinase HER3/c-erbB3 ECD),
Ob-R (human leptin receptor ECD), and VEGF (human vascular
endothelial growth factor) where ECD refers to the extracellular
domain. The nucleotide sequence data for scFv fragments from
populations of antibodies raised to each antigen was translated to
derive corresponding protein sequences. The V.sub.L sequences were
then compared using the program "align" with the algorithm of Feng
and Doolittle (1985, 1987, 1990) to calculate the percentage
identity between all pairwise combinations of chains (Feng, D. F.
and Doolittle, R. F. (1985) J. Mol. Evol. 21:112-123; Feng, D. F.
and Doolittle, R. F. (1987) J. Mol. Evol. 25:351-360; and Feng, D.
F. and Doolittle, R. F. (1990) Methods Enzymol. 183:375-387). The
percent sequence identity results of each pairwise light chain
amino acid sequence comparison were arranged in matrix format (see
Appendix).
[0238] For most pairwise comparisons, at least one common light
chain sequence was found. Table 5 is a comparison of the V.sub.L
chains showing the frequencies of scFv sharing identical light
chains (100% identity) determined by alignment of 117 V.sub.L amino
acid sequences. For example, the entry 4/9 (HER3.times.Ob-R,
highlighted in a black box), denotes that 4 clones that bind HER3
were found to share their V.sub.L sequence with one or more
anti-Ob-R clones, whereas 9 clones binding the Ob-R share their
V.sub.L sequence with one or more anti-HER3 clones. The entries on
the diagonal represent the number of antibody clones within a
population that share a V.sub.L sequence with one or more clones in
the population. For example, examination of the MPL clones revealed
5 clones that shared their V.sub.L sequence with one or more other
MPL clones. In the cases where no common light chain sequence was
observed, such as for (IgE.times.Axl) or (NpoR.times.IgE-R), the
number of fragments compared for at least one specificity was very
small (5 or less). Given the number of common light chains found,
it is likely that common light chains can be found for any V.sub.L
comparison if a sufficient number of clones are compared.
[0239] The amino acid sequences of light chains were examined for
the positions of amino acid residue differences when the sequence
identity relative to a chosen common light chain was 98% and 99%.
FIG. 4 is a comparison of V.sub.L sequences of eight different
antibodies with specificities for Axl (clone Axl.78), Rse (clones
Rse.23, Rse.04, Rse.20, and Rse.15), IgER (clone IgER.MAT2C1G11),
Ob-R (clone obr.4), and VEGF (clone vegf.5). The position of the
antigen binding CDR residues according to a sequence definition
(Kabat, G. A., et al. (1991) supra) or structural definition
(Chothia and Lesk, (1987) J. Mol. Biol. 196:901-917) are shown by
underlining and #, respectively. Light chain residues that differ
from the Axl.78 sequence are shown by double underlining. Of the 9
light chains compared, 6 are identical. The light chains of Rse.04
and obr.4 (approximately 99% sequence identity) differ by one
residue outside of the antigen binding CDRs. The light chain of
Rse.20 (approximately 98% sequence identity) differs by two
residues outside of the antigen binding CDRs. The amino acid
residue changes may have little or no affect on antigen binding.
Thus, the sequence similarity of these light chains makes them
candidates for the common light chain of the invention.
Alternatively, according to the invention, such light chains having
98-99% sequence identity with the light chain of a prospective
paired scFv (Axl.78, for example) may be substituted with the
paired light chain and retain binding specificity.
[0240] B. Identification of Antibodies that Share the Same Light
Chain: Anti-Ob-R and Anti-HER3 Clones.
[0241] ScFv fragments that bound human leptin receptor (Ob-R) or
the extracellular domain of the HER3/c-erbB3 gene product (HER3)
were obtained by three rounds of panning using a large human scFv
phage library (Vaughan et al. (1996), supra). Leptin receptor-IgG
and HER3-IgG (10 .mu.g in 1 ml PBS were used to coat separate
Immunotubes (Nunc; Maxisorp) overnight at 4.degree. C. Panning and
phage rescue were then performed as described by Vaughan et al.
(1996), supra, with the following modifications. A humanized
antibody, huMAb4D5-8 (Carter, P. et al. (1992) PNAS USA
89:4285-4289) or humanized anti-IgE (Presta, L. et al. (1993) J.
Immunol. 151:2623-2632) at a concentration of 1 mg/ml was included
in each panning step to absorb Fc-binding phage. In addition,
panning in solution (Hawkins, R. E., et al. (1992) J. Mol. Biol.
226:889-896) was also used to identify scFv binding leptin
receptor. The leptin receptor was separated from the Fc by
site-specific proteolysis of leptin receptor-IgG with the
engineered protease, Genenase (Carter, P., et al. (1989) Proteins:
Structure, Function and Genetics 6:240-248) followed by protein A
Sepharose chromatography. The leptin receptor was biotinylated and
used at a concentration of 100 nM, 25 nM and 5nM for the first,
second, and third rounds of panning, respectively. Phage binding
biotinylated antigen were captured using streptavidin-coated
paramagnetic beads (Dynabeads, Dynal, Oslo, Norway).
[0242] Clones from rounds 2 and 3 of each panning were screened by
phage and scFv ELISA using the corresponding antigen and also a
control immunoadhesin or antibody. The diversity of
antigen-positive clones was analyzed by PCR-amplification of the
scFv insert using the primers, fdtetseq and PUC reverse (Vaughan et
al. (1996), supra) and by digestion with BstNI (Marks et al. (1991)
supra). One to five clones per BstNI fingerprint were then
cycle-sequenced using fluorescent dideoxy chain terminators
(Applied Biosystems) using PCR heavy link and myc seq 10 primers
(Vaughan et al. (1996), supra). Samples were analyzed using an
Applied Biosystems Automated DNA Sequencer and sequences analyzed
using SeqEd. It is also noted that the quanidine hydrochloride
antibody denaturation and in vitro chain shuffling method of Figini
combined with phage display selection is useful as a method of
selecting antibodies having the same light chain (Figini, M. et al.
(1994), supra, herein incorporated by reference in its
entirety).
[0243] Using the method described above, eleven different anti-HER3
clones and 18 anti-Ob-R clones (11 form panning using coated
antigen and 7 from panning with biotinylated antigen) were
obtained. The clones were sequenced by standard techniques to
determine the sequences of the light chains associated with each
binding domain (FIG. 5). The sequences are the V.sub.H and common
V.sub.L sequences of the anti-Ob-R clone 26 and anti-HER3 clone 18
used to construct a bispecific antibody (see below). The residues
are numbered according to (Kabat, E. A., et al. (1991) supra). The
position of the antigen binding CDR residues according to a
sequence definition (Kabat et al. (1991) supra) or structural
definition (Chothia and Lesk, (1987) J. Mol. Biol. (1987)
196:901-917) are shown by underlining and overlining, respectively.
Identity between residues in the V.sub.H sequences is indicated by
*.
[0244] The sequences of the light chains were compared for multiple
anti-HER3 clones relative to multiple anti-Ob-R clones (FIG. 6 and
Table 5). It was observed that four out of eleven anti-HER3 clones
share identical V.sub.L with one or more anti-Ob-R receptor clones.
Conversely, nine out of eighteen anti-Ob-R clones share the same
V.sub.L as one of the anti-HER3 clones.
6TABLE 5 Shared V.sub.L usage by scFv against different target
antigens Antigen # Specificity scFv Axl GCSF-R IgE IgE-R MPL MusK
NpoR Rse HER3 Ob-R VEGF Axl 12 2 2/2 0/0 1/1 2/3 1/1 0/0 3/5 2/2
2/5 1/1 GCSF-R 11 0 1/1 2/2 2/3 1/1 2/2 2/3 2/2 3/3 2/3 IgE 2 0 1/1
1/1 0/0 1/1 1/1 1/1 1/1 0/0 IgE-R 4 0 1/1 0/0 1/1 2/3 1/1 1/1 1/1
MPL 23 5 5/3 3/2 5/8 7/5 5/9 2/2 MusK 3 0 1/1 1/2 2/2 1/1 1/2 NpoR
5 0 1/1 2/2 2/2 1/2 Rse 20 7 7/4 5/8 2/1 HER3 11 3 1 4/4 Ob-R 18 7
1/2 VEGF 8 2
[0245] C. Construction of Bispecific Antibodies Having a Common
Light Chain: Anti-Ob-R/Anti-HER3
[0246] Altered C.sub.H3 first and second polypeptides having the
complementary protuberances and cavities as well as the
non-naturally occurring disulfide bonds between the first and
second polypeptides were used in the construction of a
Fc-containing bispecific antibody. The V.sub.L from anti-Ob-R clone
#26 and anti-HER3 clone #18 which share the same light chain
according were used to prepare the bispecific antibody according to
the procedures disclosed herein.
[0247] This antibody had an electrophoretic mobility shift in
apparent molecular weight relative to a bispecific antibody that
differed only by a lack of alterations for generating non-natural
disulfide bonds. An 8% SDS-PAGE gel of heterodimeric antibody
variants with and without non-naturally occurring disulfide bonds
showed a mobility shift from approximately 160 apparent MW for wild
type heterodimer to approximately 142 apparent MW for a heterodimer
having one non-natural disulfide bond. The MW shift was sufficient
to allow determination of the percent of each variant that
successfully formed the non-natural disulfide bond.
[0248] The antibody had a binding specificity for both Ob-R and for
HER3. Ob-R binding was demonstrated in an ELISA assay with Ob-R
present as Ob-R-Ig fusion protein. The antibody bound HER3-IgG as a
second binding component in the same assay.
[0249] Expression and purification of a bispecific antibody
immunoadhesin variants was performed as follows. Human embryonic
kidney 293S cells were transfected with three plasmid DNAs,
encoding anti-CD3 light chain, anti-CD3 IgG.sub.1 heavy chain or
CD4IgG. For each transfection, the ratio of light chain-encoding
DNA to heavy chain-encoding DNA was 3:1 so that light-chain would
not be limiting for assembly of anti-CD3 IgG. Additionally, because
the immunoadhesin is poorly expressed, the ratio of immunoadhesin
encoding plasmid was added in excess to heavy chain encoding
plasmid. The ratios tested ranged from 3:1:3 through 8:1:3 for
immunoadhesin:heavy chain:light chain phagemids. 10 .mu.g total
plasmid DNA were then co-transfected into 293S cells by means of
calcium phosphate precipitation (Gorman, C., DNA Cloning, Vol II.
D. M. Glover, Ed. IRL Press, Oxford, p 143 (1985)), washing cells
with PBS prior to transfection. Fc-containing proteins were
purified from cell supernatants using immobilized protein A (ProSep
A, BioProcessing Ltd., UK) and buffer-exchanged into PBS.
Iodoacetamide was added to protein preparations to a final
concentration of 50 mM to prevent reshuffling of disulfide
bonds.
[0250] Protein samples were electrophoresed on 8% polyacrylamide
gels (Novex) and visualized by staining with Serva blue. Gels were
de-stained leaving a faint background in an effort to allow
visualization and quantitation of minor contaminants. Dried gels
were scanned with the scanning densitometer (GS-670, BioRad) and
protein products were quantitated with Molecular Analyst
software.
[0251] Non-natural (engineered) disulfide bonds introduced into the
Q.sub.H3 domain has been disclosed herein to enhance heterodimer
formation. One pair of polypeptides, K392C/D399'C, enhanced
heterodimer formation by generating up to 76% heterodimer (Table 4,
variant v6). Moreover, when combined with the
protuberance-into-cavity technology, approximately 95% heterodimer
was obtained (Table 4 variants v11, v12, v13, and v15). Thus, the
method of the invention of increasing specific protein/protein
interaction between the first and second polypeptides of a
bispecific antibody increases the yield of desired heteromultimer
and minimizes the formation of undesired heteromultimers or
homomultimers.
[0252] In addition, the method of characterizing the product
heteromultimers by electrophoretic mobility analysis allows for the
determination of the relative amount of desired heteromultimers
relative to undesired products.
[0253] Selection of a common light chain as described herein
further increases yield of the desired heteromultimer by
eliminating the possibility of mispairing between variable heavy
chains and light chains of a multispecific antibody.
[0254] The instant invention is shown and described herein in what
is considered to be the most practical, and the preferred
embodiments. It is recognized, however, that departures may be made
therefrom which are within the scope of the invention, and that
obvious modifications will occur to one skilled in the art upon
reading this disclosure. All references provided herein are herein
incorporated by reference in their entirety.
* * * * *