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  Pharmaceutical Patents  

 

Title:  Antibodies to Dkk-1
United States Patent: 
7,709,611
Issued: 
May 4, 2010

Inventors:
 Li; Ji (Thousand Oaks, CA), Shen; Wenyan (Thousand Oaks, CA), Lu; Hsieng Sen (Westlake Village, CA), Richards; William Gleason (Thousand Oaks, CA)
Assignee:
  Amgen Inc. (Thousand Oaks, CA)
Appl. No.:
 11/197,665
Filed:
 August 4, 2005


 

Pharm Bus Intell & Healthcare Studies


Abstract

The present invention provides antibodies and immunologically functional fragments thereof that specifically bind Dkk-1 polypeptides. The subject antibodies and fragments bind with high affinity to a conformational epitope located in the carboxy region of the Dkk-1 protein. Methods for preparing such antibodies or fragments thereof as well as physiologically acceptable compositions containing the antibodies or fragments are also provided. Use of the antibodies and fragments to treat various diseases including bone disorders, inflammatory diseases, neurological diseases, ocular diseases, renal diseases, pulmonary diseases and skin diseases are also disclosed.

Description of the Invention

Overview

The present invention provides novel compositions comprising antibodies and antigen-binding sites of immunoglobulins specific for Dkk-1 (e.g., a polypeptide consisting of amino acids 32 to 266 of SEQ ID NO:2 or a polypeptide consisting of amino acids 32 to 272 of SEQ ID NO:4). Some of these antibodies and antibody fragments can cross-react with Dkk-1 from several mammalian sources, including rat, mouse and human Dkk-1. Some of the antibodies and fragments have higher affinity for Dkk-1 from one species than another (e.g., some antibodies and fragments have higher affinity for human Dkk-1 as compared to rat or murine Dkk-1; other antibodies have higher affinity for rat or murine Dkk-1 as compared to human Dkk-1). The invention also provides novel neutralizing antibodies, including chimeric, humanized and human antibodies, as well as antibodies and immunologically functional fragments thereof, that bind a conformational epitope in human Dkk-1. Nucleic acids encoding the antibodies and fragments are also disclosed, as well as methods for expressing the antibodies using these nucleic acids. In another aspect, the invention relates to molecules (e.g., immunologically functional fragments and polypeptides) that are capable of exhibiting immunological binding properties of antibody antigen-binding sites.

The antibodies and immunologically functional fragments that are disclosed herein have a variety of utilities. Some of the antibodies and fragments, for instance, are useful in specific binding assays, affinity purification of Dkk-1 or its ligands and in screening assays to identify other antagonists of Dkk-1 activity. Certain of the antibodies can be used to treat various diseases that are associated with the activity of Dkk-1. Some antibodies and fragments can thus be used in a variety of treatments related to bone such as increasing bone mineral density, synthesis of new bone, treatment of systemic bone loss (e.g., bone erosions), bone repair, and treatments for various forms of arthritis. Some antibodies can also be used to increase osteoclast activity and induce bone resorption. Certain of the antibodies and fragments that are disclosed, however, can be used to treat a variety of diverse diseases that are unrelated to bone diseases. As described in greater detail below, examples of such diseases include those in which it is desirable to promote stem cell renewal (e.g., diabetes and diseases of the muscle), inflammatory diseases (e.g., Crohn's and inflammatory bowel disease), neurological diseases, ocular diseases, renal diseases, and various skin disorders.

III. Antibodies and Immunologically Functional Fragments

A variety of selective binding agents useful for regulating the activity of Dkk-1 are provided. These agents include, for instance, antibodies and immunologically functional fragments thereof that contain an antigen binding domain (e.g., single chain antibodies, domain antibodies, immunoadhesions, and polypeptides with an antigen binding region) and specifically bind to a Dkk-1 polypeptide (e.g., a human, rat and/or murine Dkk-1 polypeptide). Some of the agents, for example, are useful in inhibiting the binding of Dkk-1 to LRP5 and/or LRP6, and can thus be used to stimulate one or more activities associated with Wnt signaling.

A. Naturally Occurring Antibody Structure

Some of the binding agents that are provided have the structure typically associated with naturally occurring antibodies. The structural units of these antibodies typically comprise one or more tetramers, each composed of two identical couplets of polypeptide chains, though some species of mammals also produce antibodies having only a single heavy chain. In a typical antibody, each pair or couplet includes one full-length "light" chain (in certain embodiments, about 25 kDa) and one full-length "heavy" chain (in certain embodiments, about 50-70 kDa). Each individual immunoglobulin chain is composed of several "immunoglobulin domains," each consisting of roughly 90 to 110 amino acids and expressing a characteristic folding pattern. These domains are the basic units of which antibody polypeptides are composed. The amino-terminal portion of each chain typically includes a variable domain that is responsible for antigen recognition. The carboxy-terminal portion is more conserved evolutionarily than the other end of the chain and is referred to as the "constant region" or "C region." Human light chains generally are classified as kappa and lambda light chains, and each of these contains one variable domain and one constant domain. Heavy chains are typically classified as mu, delta, gamma, alpha, or epsilon chains, and these define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. IgG has several subtypes, including, but not limited to, IgG.sub.1, IgG.sub.2, IgG.sub.3, and IgG.sub.4. IgM subtypes include IgM.sub.1 and IgM.sub.2. IgA subtypes include IgA.sub.1 and IgA.sub.2. In humans, the IgA and IgD isotypes contain four heavy chains and four light chains; the IgG and IgE isotypes contain two heavy chains and two light chains; and the IgM isotype contains five heavy chains and five light chains. The heavy chain C region typically comprises one or more domains that may be responsible for effector function. The number of heavy chain constant region domains will depend on the isotype. IgG heavy chains, for example, each contain three C region domains known as C.sub.H1, C.sub.H2 and C.sub.H3. The antibodies that are provided can have any of these isotypes and subtypes. In certain embodiments of the invention, the anti-Dkk-1 antibody is of the IgG1, IgG.sub.2 or IgG.sub.4 subtype.

In full-length light and heavy chains, the variable and constant regions are joined by a "J" region of about 12 or more amino acids, with the heavy chain also including a "D" region of about 10 more amino acids. See, e.g., Fundamental Immunology, 2nd ed., Ch. 7 (Paul, W., ed.) 1989, New York: Raven Press (hereby incorporated by reference in its entirety for all purposes). The variable regions of each light/heavy chain pair typically form the antigen binding site.

Variable regions of immunoglobulin chains generally exhibit the same overall structure, comprising relatively conserved framework regions (FR) joined by three hypervariable regions, more often called "complementarity determining regions" or CDRs. The CDRs from the two chains of each heavy chain/light chain pair mentioned above typically are aligned by the framework regions to form a structure that binds specifically with a specific epitope on the target protein (e.g., Dkk-1). From N-terminal to C-terminal, naturally-occurring light and heavy chain variable regions both typically conform with the following order of these elements: FR1, CDR1, FR2, CDR2, FR3, CDR3 and FR4. A numbering system has been devised for assigning numbers to amino acids that occupy positions in each of these domains. This numbering system is defined in Kabat Sequences of Proteins of Immunological Interest (1987 and 1991, National Institutes of Health, Bethesda, Md.), or Chothia & Lesk, 1987, J. Mol. Biol. 196: 901-917; Chothia et al., 1989, Nature 342: 878-883.

Specific examples of some of the full length light and heavy chains of the antibodies that are provided and their corresponding nucleotide and amino acid sequences are summarized in Table 1 (see Original Patent).

Each of the light chains listed in Table 1 can be combined with any of the heavy chains shown in Table 1 to form an antibody. Examples of such combinations include L1 combined with H1-H10, or L2 combined with H1-H10 and L3 combined with H1-H10 (i.e., L1H1, L1H2, L1H3, L1H4, L1H5, L1H6, L1H7, L1H8, L1H9, L1H10, L2H1, L2H2, L2H3, L2H4, L2H5, L2H6, L2H7, L2H8, L2H9, L2H10, L3H1, L3H2, L3H3, L3H4, L3H5, L3H6, L3H7, L3H8, L3H9, and L3H10. In some instances, the antibodies include at least one heavy chain and one light chain from those listed in Table 1. In other instances, the antibodies contain two identical light chains and two identical heavy chains. As an example, an antibody or immunologically functional fragment may include two L1 light chains and two H1 heavy chains, or two L2 light chains and two H3 heavy chains, or two L2 light chains and two H4 heavy chains or two L2 and two H5 heavy chains and other similar combinations of pairs of light chains and pairs of heavy chains as listed in Table 1.

As a specific example of such antibodies, in one embodiment, the anti-Dkk-1 antibody is a monoclonal antibody derived from rats. Exemplary antibodies capable of binding to the aforementioned conformational epitope are the monoclonal antibodies 11H10 and 1F11 (see, examples below), each of which comprises a light chain and a heavy chain. The complete light chain of 11H10 is encoded by the nucleotide sequence shown in SEQ ID NO:9, and the complete heavy chain of 11H10 by the nucleotide sequence shown in SEQ ID NO:11. The corresponding light and heavy chain amino acid sequences of 11H10 are shown, respectively, in SEQ ID NOS:10 and 12. Residues 1-20 of SEQ ID NO:10 and residues 1-19 of SEQ ID NO:12 correspond to the signal sequences of these the light and heavy chains of 11H10, respectively. The amino acid sequence of the light chain without the signal sequence is shown in SEQ ID NO:82; the amino acid sequence of the heavy chain lacking the signal sequence is shown in SEQ ID NO:89.

Thus, in one aspect of the foregoing embodiment, the heavy chain may consist of amino acids 20-465 of SEQ ID NO:12 (i.e., H1, corresponding to SEQ ID NO:89), and in another aspect of this embodiment, the light chain may consist of amino acids 21-234 of SEQ ID NO:10 (i.e., L1, corresponding to SEQ ID NO:82). In yet another aspect of this embodiment, the antibody comprises both a heavy chain consisting of amino acids 20-465 of SEQ ID NO:12 and a light chain consisting of amino acids 21-234 of SEQ ID NO:10. In some instances, the antibody consists of two identical heavy chains each consisting of amino acids 20-465 of SEQ ID NO:12 and two identical light chains each consisting of amino acids 21-234 of SEQ ID NO:10. Another specific example is an antibody that includes the light chain L2 (SEQ ID NO:26) and the heavy chain H2 (SEQ ID NO:34). The coding sequences for these light and heavy chains are presented respectively, in SEQ ID NOS:25 and 33. These antibodies may include two identical heavy and light chains. The other heavy chain and light chains listed in Table 1 can be combined in a similar fashion.

Other antibodies that are provided are variants of antibodies formed by combination of the heavy and light chains shown in Table 1 and comprise light and/or heavy chains that each have at least 70%, 75%, 80%, 85%, 90%, 95%, 97% or 99% identity to the amino acid sequences of these chains. In some instances, such antibodies include at least one heavy chain and one light chain, whereas in other instances the such variant forms contain two identical light chains and two identical heavy chains.

B. Variable Domains of Antibodies

Also provided are antibodies that comprise a light chain variable region selected from the group consisting of VL1, VL2, VL3 and/or a heavy chain variable region selected from the group consisting of VH1-VH10 as shown in Table 2 (see Original Patent), and immunologically functional fragments, derivatives, muteins and variants of these light chain and heavy chain variable regions.

Antibodies of this type can generally be designated by the formula "VLxVHy," where "x" is the number of the light chain variable region and "y" corresponds to the number of the heavy chain variable region as listed in Table 2. In general, x and y are each 1 or 2.

Thus, VL2VH1 refers to an antibody with a light chain variable region domain comprising the amino acid sequence of VL2 and a heavy chain variable region comprising the amino acid sequence of VH1. The antibodies that are provided thus include, but are not limited to, those having the following form: VL1VH1, VL1VH2, VL1VH3, VL1VH4, VL1VH5, VL1VH6, VL1VH7, VL1VH8, VL1VH9, VL1VH10, VL2VH1, VL2VH2, VL2VH3, VL2VH4, VL2VH5, VL2VH6, VL2VH7, VL2VH8, VL2VH9, VL2VH10, VL3VH1, VL3VH2, VL3VH3, VL3VH4, VL3VH5, VL3VH6, VL3VH7, VL3VH8, VL3VH9, and VL3VH10. In some instances, the foregoing antibodies include two light chain variable region domains and two heavy chain variable region domains (e.g. VL1.sub.2VH1.sub.2 etc.)

As a specific example of such antibodies, certain antibodies or immunologically functional fragments thereof comprise the variable region of the light chain or the variable region of the heavy chain of 11H10, wherein the light chain variable region consists of amino acids 21-127 of SEQ ID NO:10 (i.e., VL1, corresponding to SEQ ID NO:84) and the heavy chain variable region consists of amino acids 20-139 of SEQ ID NO:12 (i.e., VH1, corresponding to SEQ ID NO:91). In one aspect of this embodiment, the antibody consists of two identical heavy chains and two identical light chains.

Also provided, for instance, is an antibody comprising a light chain variable region that consists of amino acids 21-127 of SEQ ID NO:10 or an antigen-binding or an immunologically functional fragment thereof and further comprising a heavy chain variable region that consists of amino acids 20-139 of SEQ ID NO:12.

Certain antibodies comprise a light chain variable domain comprising a sequence of amino acids that differs from the sequence of a light chain variable domain selected from L1, L2 or L3 at only 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 amino acid residues, wherein each such sequence difference is independently either a deletion, insertion or substitution of one amino acid. The light chain variable region in some antibodies comprises a sequence of amino acids that has at least 70%, 75%, 80%, 85%, 90%, 95%, 97% or 99% sequence identity to the amino acid sequences of the light chain variable region of VL1, VL2 or VL3.

Some antibodies that are provided comprise a heavy chain variable domain comprising a sequence of amino acids that differs from the sequence of a heavy chain variable domain selected from H1-H10 at only 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 amino acid residues, wherein each such sequence difference is independently either a deletion, insertion or substitution of one amino acid. The heavy chain variable region in some antibodies comprises a sequence of amino acids that has at least 70%, 75%, 80%, 85%, 90%, 95%, 97% or 99% sequence identity to the amino acid sequences of the heavy chain variable region of VH1, VH2, VH3, VH4, VH5, VH6, VH7, VH8, VH9, VH10. Still other antibodies or immunologically functional fragments include variant forms of a variant light chain and a variant heavy chain as just described.

C. CDRs of Antibodies

Complementarity determining regions (CDRs) and framework regions (FR) of a given antibody may be identified using the system described by Kabat et al. in Sequences of Proteins of Immunological Interest, 5th Ed., US Dept. of Health and Human Services, PHS, NIH, NIH Publication no. 91-3242, 1991. Certain antibodies that are disclosed herein comprise one or more amino acid sequences that are identical or have substantial sequence identity to the amino acid sequences of one or more of the CDRs as summarized in Table 3 (see Original Patent).

The antibodies and immunological functional fragments that are provided can include one, two, three, four, five or all six of the CDRs listed above. Some antibodies or fragments include both the light chain CDR3 and the heavy chain CDR3. Certain antibodies have variant forms of the CDRs listed in Table 3, with one or more (i.e., 2, 3, 4, 5 or 6) of the CDRs each having at least 80%, 85%, 90% or 95% sequence identity to a CDR sequence listed in Table 3. For example, the antibody or fragment can include both a light chain CDR3 and a heavy chain CDR3 that each have at least 80%, 85%, 90% or 95% sequence identity to the light chain CDR3 sequence and the heavy chain CDR3, respectively, listed in Table 3. The CDR sequences of some of the antibodies that are provided may also differ from the CDR sequences listed in Table 3 such that the amino acid sequence for any given CDR differs from the sequence listed in Table 3 by no more than 1, 2, 3, 4 or 5 amino acid residues. Differences from the listed sequences usually are conservative substitutions (see below).

As a specific example, the antibodies and immunologically functional fragments that are provided may comprise one or more of the following CDR sequences from the 11H10 light chain:

CDR1: amino acids 44-54 of SEQ ID NO:10, which also corresponds to SEQ ID NO:70 (encoded by nucleotides 130-162 of SEQ ID NO:9 (SEQ ID NO:85) or SEQ ID NO:69);

CDR2: amino acids 70-76 of SEQ ID NO:10, which also corresponds to SEQ ID NO:72 (encoded by nucleotides 208-228 of SEQ ID NO:9 (SEQ ID NO:86) or SEQ ID NO:71);

CDR3: amino acids 109-117 of SEQ ID NO:10, which also corresponds to SEQ ID NO:74 (encoded by nucleotides 325-351 of SEQ ID NO:9 (SEQ ID NO:87) or SEQ ID NO:73);

Additional antibodies and immunologically functional immunoglobulin fragments of the invention may comprise one or more of the following CDR sequences from the 11H10 heavy chain:

CDR1: amino acids 50-54 of SEQ ID NO:12, which also corresponds with SEQ ID NO:76 (encoded by nucleotides 148-162 of SEQ ID NO:11 (SEQ ID NO:92) or SEQ ID NO:75);

CDR2: amino acids 69-85 of SEQ ID NO:12, which also corresponds with SEQ ID NO:78 (encoded by nucleotides 205-255 of SEQ ID NO:11 (SEQ ID NO:93) or SEQ ID NO:77);

CDR3: and amino acids 118-128 of SEQ ID NO:12, which also corresponds with SEQ ID NO:80 (encoded by nucleotides 352-384 of SEQ ID NO:11 (SEQ ID NO:94) or SEQ ID NO:79).

Polypeptides comprising one or more of the light or heavy chain CDRs may be produced by using a suitable vector to express the polypeptides in a suitable host cell as described in greater detail below.

The heavy and light chain variable regions and the CDRs that are disclosed in Table 2 and 3 (see Original Patent) can be used to prepare any of the various types of immunologically functional fragments that are known in the art including, but not limited to, domain antibodies, Fab fragments, Fab' fragments, F(ab').sub.2 fragments, Fv fragments, single-chain antibodies and scFvs.

D. Antibodies and Binding Epitopes

When an antibody is said to bind an epitope within specified residues, such as Dkk-1, for example, what is meant is that the antibody specifically binds to a polypeptide consisting of the specified residues (e.g., a specified segment of Dkk-1). Such an antibody does not necessarily contact every residue within Dkk-1. Nor does every single amino acid substitution or deletion within Dkk-1 necessarily significantly affect binding affinity. Epitope specificity of an antibody can be determined in variety of ways. One approach, for example, involves testing a collection of overlapping peptides of about 15 amino acids spanning the sequence of Dkk-1 and differing in increments of a small number of amino acids (e.g., 3 amino acids). The peptides are immobilized within the wells of a microtiter dish. Immobilization can be effected by biotinylating one terminus of the peptides. Optionally, different samples of the same peptide can be biotinylated at the N and C terminus and immobilized in separate wells for purposes of comparison. This is useful for identifying end-specific antibodies. Optionally, additional peptides can be included terminating at a particular amino acid of interest. This approach is useful for identifying end-specific antibodies to internal fragments of Dkk-1. An antibody or immunologically functional fragment is screened for specific binding to each of the various peptides. The epitope is defined as occurring with a segment of amino acids that is common to all peptides to which the antibody shows specific binding. Details regarding a specific approach for defining an epitope is set forth in Example 6.

Antibodies and functional fragments thereof that bind to a conformational epitope that is located in the carboxy-terminal portion of Dkk-1 (see FIG. 1 (see Original Patent)) are also provided. The carboxy-terminus of Dkk-1 contains several cysteine residues that form a cluster of disulfide bonds which create several loops. The invention provides antibodies that bind to two of these loops, thereby neutralizing the ability of Dkk-1 to suppress Wnt activity. Exemplary antibodies capable of binding to the aforementioned conformational epitope are the monoclonal antibodies 11H10 and 1F11, each of which comprises a light chain and a heavy chain. The complete light chain of 11H10 is encoded by the nucleotide sequence shown in SEQ ID NO:9, and the complete heavy chain of 11H10 by the nucleotide sequence shown in SEQ ID NO:11. The corresponding light and heavy chain amino acid sequences of 11H10 (including signal sequences) are shown, respectively, in SEQ ID NOS:10 and 12. The mature forms without the signal sequences correspond to SEQ ID NOS: 82 and 89.

The epitope comprising these two loops is formed by disulfide bonds between cysteine residues 220 and 237 of SEQ ID NO:2 and between cysteine residues 245 and 263 of SEQ ID NO:2. The body of the two loops that form the epitope thus includes amino acids 221-236 and 246-262 of SEQ ID NO:2. Segments within this loop that are involved in binding include amino acids 221-229 of SEQ ID NO:2 and amino acids 246-253 of SEQ ID NO:2. Thus, certain antibodies and fragments that are provided herein specifically bind to the foregoing region(s). Some of the antibodies and fragments, for instance, bind to a peptide comprising or consisting of amino acids 221 to 262 of SEQ ID NO:2.

In one aspect of the invention, peptides comprising or consisting of amino acids 221-229 and/or 246-253 of SEQ ID NO:2 are provided. Other peptides comprise or consist of amino acids 221-236 and/or 246-262 of SEQ ID NO:2. Still other peptides that are provided comprise or consist of the region from 221 to 262 of SEQ ID NO:2 or amino acids 221-253 of SEQ ID NO:2. Such peptides are shorter than the full-length protein sequence of a native Dkk-1 (e.g., the peptides may include one or more of the forgoing regions and be 8, 9, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25, 30, 40, 50, 75, 100, 150, or 200 amino acids in length). These peptides may be fused to another peptide to increase immunogenicity and thus be in the form of a fusion protein.

E. Competing Antibodies

Antibodies and immunologically functional fragments thereof that compete with one the exemplified antibodies or functional fragments for specific binding to Dkk-1 are also provided. Such antibodies and fragments may also bind to the same epitope as one of the exemplified antibodies. Antibodies and fragments that compete with or bind to the same epitope as the exemplified antibody or fragment are expected to show similar functional properties. The exemplified antibodies and fragment include those described above, including those with the heavy and light chains, variable region domains and CDRs listed in Tables 1-3. Competing antibodies or immunologically functional fragments can include those that bind to the epitope described in the section on antibodies and epitopes above.

As a specific example, some competing antibodies or fragments include those that specifically bind a Dkk-1 protein consisting of amino acids 32 to 266 of SEQ ID NO:2 or amino acids 32 to 272 of SEQ ID NO:4 and can prevent or reduce the binding to human Dkk-1 of an antibody that consists of two identical heavy chains and two identical light chains, wherein said heavy chains consist of amino acids 20-465 of SEQ ID NO:12 and said light chains consist of amino acids 21-234 of SEQ ID NO:10. Other competing antibodies prevent or reduce the binding to human Dkk-1 of an antibody that consists of two identical heavy chains and two identical light chains such as those listed in Table 1.

F. Monoclonal Antibodies

The antibodies that are provided include monoclonal antibodies that bind to Dkk-1. Monoclonal antibodies may be produced using any technique known in the art, e.g., by immortalizing spleen cells harvested from the transgenic animal after completion of the immunization schedule. The spleen cells can be immortalized using any technique known in the art, e.g., by fusing them with myeloma cells to produce hybridomas. Myeloma cells for use in hybridoma-producing fusion procedures preferably are non-antibody-producing, have high fusion efficiency, and enzyme deficiencies that render them incapable of growing in certain selective media which support the growth of only the desired fused cells (hybridomas). Examples of suitable cell lines for use in mouse fusions include Sp-20, P3-X63/Ag8, P3-X63-Ag8.653, NS1/1.Ag 4 1, Sp210-Ag14, FO, NSO/U, MPC-11, MPC11-X45-GTG 1.7 and S194/5XXO Bul; examples of cell lines used in rat fusions include R210.RCY3, Y3-Ag 1.2.3, IR983F and 4B210. Other cell lines useful for cell fusions are U-266, GM1500-GRG2, LICR-LON-HMy2 and UC729-6.

In some instances, a hybridoma cell line is produced by immunizing an animal (e.g., a transgenic animal having human immunoglobulin sequences) with a Dkk-1 immunogen; harvesting spleen cells from the immunized animal; fusing the harvested spleen cells to a myeloma cell line, thereby generating hybridoma cells; establishing hybridoma cell lines from the hybridoma cells, and identifying a hybridoma cell line that produces an antibody that binds a Dkk-1 polypeptide. Such hybridoma cell lines, and anti-Dkk-1 monoclonal antibodies produced by them, are encompassed by the present invention.

Monoclonal antibodies secreted by a hybridoma cell line can be purified using any technique known in the art. Hybridomas or mAbs may be further screened to identify mAbs with particular properties, such as the ability to block a Wnt induced activity. Examples of such screens are provided in the examples below.

G. Chimeric and Humanized Antibodies

Chimeric and humanized antibodies based upon the foregoing sequences are also provided. Monoclonal antibodies for use as therapeutic agents may be modified in various ways prior to use. One example is a "chimeric" antibody, which is an antibody composed of protein segments from different antibodies that are covalently joined to produce functional immunoglobulin light or heavy chains or immunologically functional portions thereof. Generally, a portion of the heavy chain and/or light chain is identical with or homologous to a corresponding sequence in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is/are identical with or homologous to a corresponding sequence in antibodies derived from another species or belonging to another antibody class or subclass. For methods relating to chimeric antibodies, see, for example, U.S. Pat. No. 4,816,567; and Morrison et al., Proc. Natl. Acad. Sci. USA 81:6851-6855 (1985), which are hereby incorporated by reference. CDR grafting is described, for example, in U.S. Pat. Nos. 6,180,370, 5,693,762, 5,693,761, 5,585,089, and 5,530,101, which are all hereby incorporated by reference for all purposes.

Generally, the goal of making a chimeric antibody is to create a chimera in which the number of amino acids from the intended patient species is maximized. One example is the "CDR-grafted" antibody, in which the antibody comprises one or more complementarity determining regions (CDRs) from a particular species or belonging to a particular antibody class or subclass, while the remainder of the antibody chain(s) is/are identical with or homologous to a corresponding sequence in antibodies derived from another species or belonging to another antibody class or subclass. For use in humans, the V region or selected CDRs from a rodent antibody often are grafted into a human antibody, replacing the naturally-occurring V regions or CDRs of the human antibody.

One useful type of chimeric antibody is a "humanized" antibody. Generally, a humanized antibody is produced from a monoclonal antibody raised initially in a non-human animal. Certain amino acid residues in this monoclonal antibody, typically from non-antigen recognizing portions of the antibody, are modified to be homologous to corresponding residues in a human antibody of corresponding isotype. Humanization can be performed, for example, using various methods by substituting at least a portion of a rodent variable region for the corresponding regions of a human antibody (see, e.g., U.S. Pat. Nos. 5,585,089, and 5,693,762; Jones et al., 1986, Nature 321:522-25; Riechmann et al., 1988, Nature 332:323-27; Verhoeyen et al., 1988, Science 239:1534-36),

In one aspect of the invention, the CDRs of the light and heavy chain variable regions of the antibodies provided herein (see Table 3) are grafted to framework regions (FRs) from antibodies from the same, or a different, phylogenetic species. For example, the CDRs of the light and heavy chain variable regions of the 11H10 antibody can be grafted to consensus human FRs. To create consensus human FRs, FRs from several human heavy chain or light chain amino acid sequences may be aligned to identify a consensus amino acid sequence. In other embodiments, the FRs of the 11H10 antibody heavy chain or light chain are replaced with the FRs from a different heavy chain or light chain. In one aspect of the invention, rare amino acids in the FRs of the heavy and light chains of anti-Dkk-1 antibody are not replaced, while the rest of the FR amino acids are replaced. A "rare amino acid" is a specific amino acid that is in a position in which this particular amino acid is not usually found in an FR. Alternatively, the grafted variable regions from the 11H10 antibody may be used with a constant region that is different from the constant region of 11H10. In other embodiments of the invention, the grafted variable regions are part of a single chain Fv antibody.

In certain embodiments, constant regions from species other than human can be used along with the human variable region(s) to produce hybrid antibodies.

H. Fully Human Antibodies

Fully human antibodies are also provided. Methods are available for making fully human antibodies specific for a given antigen without exposing human beings to the antigen ("fully human antibodies"). One means for implementing the production of fully human antibodies is the "humanization" of the mouse humoral immune system. Introduction of human immunoglobulin (Ig) loci into mice in which the endogenous Ig genes have been inactivated is one means of producing fully human monoclonal antibodies (MAbs) in mouse, an animal that can be immunized with any desirable antigen. Using fully human antibodies can minimize the immunogenic and allergic responses that can sometimes be caused by administering mouse or mouse-derivatized Mabs to humans as therapeutic agents.

Fully human antibodies can be produced by immunizing transgenic animals (usually mice) that are capable of producing a repertoire of human antibodies in the absence of endogenous immunoglobulin production. Antigens for this purpose typically have six or more contiguous amino acids, and optionally are conjugated to a carrier, such as a hapten. See, for example, Jakobovits et al., 1993, Proc. Natl. Acad. Sci. USA 90:2551-2555; Jakobovits et al., 1993, Nature 362:255-258; and Bruggermann et al., 1993, Year in Immunol. 7:33. In one example of such a method, transgenic animals are produced by incapacitating the endogenous mouse immunoglobulin loci encoding the mouse heavy and light immunoglobulin chains therein, and inserting into the mouse genome large fragments of human genome DNA containing loci that encode human heavy and light chain proteins. Partially modified animals, which have less than the full complement of human immunoglobulin loci, are then cross-bred to obtain an animal having all of the desired immune system modifications. When administered an immunogen, these transgenic animals produce antibodies that are immunospecific for the immunogen but have human rather than murine amino acid sequences, including the variable regions. For further details of such methods, see, for example, WO96/33735 and WO94/02602, which are hereby incorporated by reference. Additional methods relating to transgenic mice for making human antibodies are described in U.S. Pat. Nos. 5,545,807; 6,713,610; 6,673,986; 6,162,963; 5,545,807; 6,300,129; 6,255,458; 5,877,397; 5,874,299 and 5,545,806; in PCT publications WO91/10741, WO90/04036, and in EP 546073B1 and EP 546073A1, all of which are hereby incorporated by reference in their entirety for all purposes.

The transgenic mice described above, referred to herein as "HuMab" mice, contain a human immunoglobulin gene minilocus that encodes unrearranged human heavy (.mu. and .gamma.) and .kappa. light chain immunoglobulin sequences, together with targeted mutations that inactivate the endogenous .mu. and .kappa. chain loci (Lonberg et al., 1994, Nature 368: 856-859). Accordingly, the mice exhibit reduced expression of mouse IgM or .kappa. and in response to immunization, and the introduced human heavy and light chain transgenes undergo class switching and somatic mutation to generate high affinity human IgG .kappa. monoclonal antibodies (Lonberg et al., supra.; Lonberg and Huszar, 1995, Intern. Rev. Immunol., 13: 65-93; Harding and Lonberg, 1995, Ann. N.Y. Acad. Sci 764: 536-546). The preparation of HuMab mice is described in detail in Taylor et al., 1992, Nucleic Acids Research, 20: 6287-6295; Chen et al., 1993, International Immunology 5: 647-656; Tuaillon et al., 1994, J. Immunol. 152: 2912-2920; Lonberg et al., 1994, Nature 368: 856-859; Lonberg, 1994, Handbook of Exp. Pharmacology 113: 49-101; Taylor et al., 1994, International Immunology 6: 579-591; Lonberg and Huszar, 1995, Intern. Rev. Immunol. 13: 65-93; Harding and Lonberg, 1995, Ann. N.Y Acad. Sci. 764: 536-546; Fishwild et al., 1996, Nature Biotechnology 14: 845-851; the foregoing references are hereby incorporated by reference in their entirety for all purposes. See further U.S. Pat. Nos. 5,545,806; 5,569,825; 5,625,126; 5,633,425; 5,789,650; 5,877,397; 5,661,016; 5,814,318; 5,874,299; and 5,770,429; as well as U.S. Pat. No. 5,545,807; International Publication Nos. WO 93/1227; WO 92/22646; and WO 92/03918, the disclosures of all of which are hereby incorporated by reference in their entirety for all purposes. Technologies utilized for producing human antibodies in these transgenic mice are disclosed also in WO 98/24893, and Mendez et al., 1997, Nature Genetics 15: 146-156, which are hereby incorporated by reference. For example, the HCo7 and HCo12 transgenic mice strains can be used to generate human anti-Dkk-1 antibodies.

Using hybridoma technology, antigen-specific human MAbs with the desired specificity can be produced and selected from the transgenic mice such as those described above. Such antibodies may be cloned and expressed using a suitable vector and host cell, or the antibodies can be harvested from cultured hybridoma cells.

Fully human antibodies can also be derived from phage-display libraries (as disclosed in Hoogenboom et al., 1991, J. Mol. Biol. 227:381; and Marks et al., 1991, J. Mol. Biol. 222:581). Phage display techniques mimic immune selection through the display of antibody repertoires on the surface of filamentous bacteriophage, and subsequent selection of phage by their binding to an antigen of choice. One such technique is described in PCT Publication No. WO99/10494 (hereby incorporated by reference), which describes the isolation of high affinity and functional agonistic antibodies for MPL- and msk-receptors using such an approach.

I. Bispecific or Bifunctional Antibodies

The antibodies that are provided also include bispecific and bifunctional antibodies that include one or more CDRs or one or more variable regions as described above. A bispecific or bifunctional antibody in some instances is an artificial hybrid antibody having two different heavy/light chain pairs and two different binding sites. Bispecific antibodies may be produced by a variety of methods including, but not limited to, fusion of hybridomas or linking of Fab' fragments. See, e.g., Songsivilai & Lachmann, 1990, Clin. Exp. Immunol. 79: 315-321; Kostelny et al., 1992, J. Immunol. 148: 1547-1553.

J. Various Other Forms

Some of the antibodies or immunologically functional fragments that are provided are variant forms of the antibodies and fragments disclosed above (e.g., those having the sequences listed in Tables 1-3). For instance, some of the antibodies or fragments are ones having one or more conservative amino acid substitutions in one or more of the heavy or light chains, variable regions or CDRs listed in Tables 1-3.

Naturally-occurring amino acids may be divided into classes based on common side chain properties: 1) hydrophobic: norleucine, Met, Ala, Val, Leu, Ile; 2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln; 3) acidic: Asp, Glu; 4) basic: His, Lys, Arg; 5) residues that influence chain orientation: Gly, Pro; and 6) aromatic: Trp, Tyr, Phe. Conservative amino acid substitutions may involve exchange of a member of one of these classes with another member of the same class. Conservative amino acid substitutions may encompass non-naturally occurring amino acid residues, which are typically incorporated by chemical peptide synthesis rather than by synthesis in biological systems. These include peptidomimetics and other reversed or inverted forms of amino acid moieties.

Non-conservative substitutions may involve the exchange of a member of one of the above classes for a member from another class. Such substituted residues may be introduced into regions of the antibody that are homologous with human antibodies, or into the non-homologous regions of the molecule.

In making such changes, according to certain embodiments, the hydropathic index of amino acids may be considered. The hydropathic profile of a protein is calculated by assigning each amino acid a numerical value ("hydropathy index") and then repetitively averaging these values along the peptide chain. Each amino acid has been assigned a hydropathic index on the basis of its hydrophobicity and charge characteristics. They are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine/cystine (+2.5); methionine (+1.9); alanine (+1.8); glycine (-0.4); threonine (-0.7); serine (-0.8); tryptophan (-0.9); tyrosine (-1.3); proline (-1.6); histidine (-3.2); glutamate (-3.5); glutamine (-3.5); aspartate (-3.5); asparagine (-3.5); lysine (-3.9); and arginine (-4.5).

The importance of the hydropathic profile in conferring interactive biological function on a protein is understood in the art (see, for example, Kyte et al., 1982, J. Mol. Biol. 157:105-131). It is known that certain amino acids may be substituted for other amino acids having a similar hydropathic index or score and still retain a similar biological activity. In making changes based upon the hydropathic index, in certain embodiments, the substitution of amino acids whose hydropathic indices are within .+-.2 is included. In some aspects of the invention, those which are within .+-.1 are included, and in other aspects of the invention, those within .+-.0.5 are included.

It is also understood in the art that the substitution of like amino acids can be made effectively on the basis of hydrophilicity, particularly where the biologically functional protein or peptide thereby created is intended for use in immunological embodiments, as in the present case. In certain embodiments, the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with its immunogenicity and antigen-binding or immunogenicity, that is, with a biological property of the protein.

The following hydrophilicity values have been assigned to these amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0.+-.1); glutamate (+3.0.+-.1); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); threonine (-0.4); proline (-0.5.+-.1); alanine (-0.5); histidine (-0.5); cysteine (-1.0); methionine (-1.3); valine (-1.5); leucine (-1.8); isoleucine (-1.8); tyrosine (-2.3); phenylalanine (-2.5) and tryptophan (-3.4). In making changes based upon similar hydrophilicity values, in certain embodiments, the substitution of amino acids whose hydrophilicity values are within .+-.2 is included, in other embodiments, those which are within .+-.1 are included, and in still other embodiments, those within .+-.0.5 are included. In some instances, one may also identify epitopes from primary amino acid sequences on the basis of hydrophilicity. These regions are also referred to as "epitopic core regions."

Exemplary conservative amino acid substitutions are set forth in Table 4 (see Original Patent).

A skilled artisan will be able to determine suitable variants of polypeptides as set forth herein using well-known techniques. One skilled in the art may identify suitable areas of the molecule that may be changed without destroying activity by targeting regions not believed to be important for activity. The skilled artisan also will be able to identify residues and portions of the molecules that are conserved among similar polypeptides. In further embodiments, even areas that may be important for biological activity or for structure may be subject to conservative amino acid substitutions without destroying the biological activity or without adversely affecting the polypeptide structure.

Additionally, one skilled in the art can review structure-function studies identifying residues in similar polypeptides that are important for activity or structure. In view of such a comparison, one can predict the importance of amino acid residues in a protein that correspond to amino acid residues important for activity or structure in similar proteins. One skilled in the art may opt for chemically similar amino acid substitutions for such predicted important amino acid residues.

One skilled in the art can also analyze the three-dimensional structure and amino acid sequence in relation to that structure in similar polypeptides. In view of such information, one skilled in the art may predict the alignment of amino acid residues of an antibody with respect to its three dimensional structure. One skilled in the art may choose not to make radical changes to amino acid residues predicted to be on the surface of the protein, since such residues may be involved in important interactions with other molecules. Moreover, one skilled in the art may generate test variants containing a single amino acid substitution at each desired amino acid residue. These variants can then be screened using assays for Dkk-1 neutralizing activity, (see examples below) thus yielding information regarding which amino acids can be changed and which must not be changed. In other words, based on information gathered from such routine experiments, one skilled in the art can readily determine the amino acid positions where further substitutions should be avoided either alone or in combination with other mutations.

A number of scientific publications have been devoted to the prediction of secondary structure. See Moult, 1996, Curr. Op. in Biotech. 7:422-427; Chou et al., 1974, Biochemistry 13:222-245; Chou et al., 1974, Biochemistry 113:211-222; Chou et al., 1978, Adv. Enzymol. Relat. Areas Mol. Biol. 47:45-148; Chou et al., 1979, Ann. Rev. Biochem. 47:251-276; and Chou et al., 1979, Biophys. J. 26:367-384. Moreover, computer programs are currently available to assist with predicting secondary structure. One method of predicting secondary structure is based upon homology modeling. For example, two polypeptides or proteins that have a sequence identity of greater than 30%, or similarity greater than 40% often have similar structural topologies. The recent growth of the protein structural database (PDB) has provided enhanced predictability of secondary structure, including the potential number of folds within a polypeptide's or protein's structure. See Holm et al., 1999, Nucl. Acid. Res. 27:244-247. It has been suggested (Brenner et al., 1997, Curr. Op. Struct. Biol. 7:369-376) that there are a limited number of folds in a given polypeptide or protein and that once a critical number of structures have been resolved, structural prediction will become dramatically more accurate.

Additional methods of predicting secondary structure include "threading" (Jones, 1997, Curr. Opin. Struct. Biol. 7:377-87; Sippl et al., 1996, Structure 4:15-19), "profile analysis" (Bowie et al., 1991, Science 253:164-170; Gribskov et al., 1990, Meth. Enzym. 183:146-159; Gribskov et al., 1987, Proc. Nat. Acad. Sci. 84:4355-4358), and "evolutionary linkage" (See Holm, 1999, supra; and Brenner, 1997, supra).

In some embodiments of the invention, amino acid substitutions are made that: (1) reduce susceptibility to proteolysis, (2) reduce susceptibility to oxidation, (3) alter binding affinity for forming protein complexes, (4) alter ligand or antigen binding affinities, and/or (4) confer or modify other physicochemical or functional properties on such polypeptides. For example, single or multiple amino acid substitutions (in certain embodiments, conservative amino acid substitutions) may be made in the naturally-occurring sequence. Substitutions can be made in that portion of the antibody that lies outside the domain(s) forming intermolecular contacts). In such embodiments, conservative amino acid substitutions can be used that do not substantially change the structural characteristics of the parent sequence (e.g., one or more replacement amino acids that do not disrupt the secondary structure that characterizes the parent or native antibody). Examples of art-recognized polypeptide secondary and tertiary structures are described in Proteins, Structures and Molecular Principles (Creighton, Ed.), 1984, W. H. New York: Freeman and Company; Introduction to Protein Structure (Branden and Tooze, eds.), 1991, New York: Garland Publishing; and Thornton et at., 1991, Nature 354: 105, which are each incorporated herein by reference.

The invention also encompasses glycosylation variants of the inventive antibodies wherein the number and/or type of glycosylation site(s) has been altered compared to the amino acid sequences of the parent polypeptide. In certain embodiments, antibody protein variants comprise a greater or a lesser number of N-linked glycosylation sites than the native antibody. An N-linked glycosylation site is characterized by the sequence: Asn-X-Ser or Asn-X-Thr, wherein the amino acid residue designated as X may be any amino acid residue except proline. The substitution of amino acid residues to create this sequence provides a potential new site for the addition of an N-linked carbohydrate chain. Alternatively, substitutions that eliminate or alter this sequence will prevent addition of an N-linked carbohydrate chain present in the native polypeptide. For example, the glycosylation can be reduced by the deletion of an Asn or by substituting the Asn with a different amino acid. In other embodiments, one or more new N-linked sites are created. Antibodies typically have a N-linked glycosylation site in the Fc region. For example, the 11H10 antibody described herein has an N-linked glycosylation site at amino acid 315 (SEQ ID NO:12).

Additional preferred antibody variants include cysteine variants wherein one or more cysteine residues in the parent or native amino acid sequence are deleted from or substituted with another amino acid (e.g., serine). Cysteine variants are useful, inter alia when antibodies must be refolded into a biologically active conformation. Cysteine variants may have fewer cysteine residues than the native antibody, and typically have an even number to minimize interactions resulting from unpaired cysteines.

The heavy and light chains, variable regions domains and CDRs that are disclosed can be used to prepare polypeptides that contain an antigen binding region that can specifically bind to a Dkk-1 polypeptide. For example, one or more of the CDRs listed in Table 3 can be incorporated into a molecule (e.g., a polypeptide) covalently or noncovalently to make an immunoadhesion. An immunoadhesion may incorporate the CDR(s) as part of a larger polypeptide chain, may covalently link the CDR(s) to another polypeptide chain, or may incorporate the CDR(s) noncovalently. The CDR(s) enable the immunoadhesion to bind specifically to a particular antigen of interest (e.g., a Dkk-1 polypeptide or epitope thereof).

Mimetics (e.g., peptide mimetics" or "peptidomimetics") based upon the variable region domains and CDRs that are described herein are also provided. These analogs can be peptides, non-peptides or combinations of peptide and non-peptide regions. Fauchere, 1986, Adv. Drug Res. 15: 29; Veber and Freidinger, 1985, TINS p. 392; and Evans et al., 1987, J. Med. Chem. 30: 1229, which are incorporated herein by reference for any purpose. Peptide mimetics that are structurally similar to therapeutically useful peptides may be used to produce a similar therapeutic or prophylactic effect. Such compounds are often developed with the aid of computerized molecular modeling. Generally, peptidomimetics of the invention are proteins that are structurally similar to an antibody displaying a desired biological activity, such as here the ability to specifically bind Dkk-1, but have one or more peptide linkages optionally replaced by a linkage selected from: --CH.sub.2NH--, --CH.sub.2S--, --CH.sub.2--CH.sub.2--, --CH.dbd.CH-(cis and trans), --COCH.sub.2--, --CH(OH)CH.sub.2--, and --CH.sub.2SO--, by methods well known in the art. Systematic substitution of one or more amino acids of a consensus sequence with a D-amino acid of the same type (e.g., D-lysine in place of L-lysine) may be used in certain embodiments of the invention to generate more stable proteins. In addition, constrained peptides comprising a consensus sequence or a substantially identical consensus sequence variation may be generated by methods known in the art (Rizo and Gierasch, 1992, Ann. Rev. Biochem. 61: 387), incorporated herein by reference), for example, by adding internal cysteine residues capable of forming intramolecular disulfide bridges which cyclize the peptide.

Derivatives of the antibodies and immunologically functional fragments that are described herein are also provided. The derivatized antibody or fragment may comprise any molecule or substance that imparts a desired property to the antibody or fragment, such as increased half-life in a particular use. The derivatized antibody can comprise, for example, a detectable (or labeling) moiety (e.g., a radioactive, colorimetric, antigenic or enzymatic molecule, a detectable bead (such as a magnetic or electrodense (e.g., gold) bead), or a molecule that binds to another molecule (e.g., biotin or streptavidin)), a therapeutic or diagnostic moiety (e.g., a radioactive, cytotoxic, or pharmaceutically active moiety), or a molecule that increases the suitability of the antibody for a particular use (e.g., administration to a subject, such as a human subject, or other in vivo or in vitro uses). Examples of molecules that can be used to derivatize an antibody include albumin (e.g., human serum albumin) and polyethylene glycol (PEG). Albumin-linked and PEGylated derivatives of antibodies can be prepared using techniques well known in the art. In one embodiment, the antibody is conjugated or otherwise linked to transthyretin (TTR) or a TTR variant. The TTR or TTR variant can be chemically modified with, for example, a chemical selected from the group consisting of dextran, poly(n-vinyl pyrrolidone), polyethylene glycols, propropylene glycol homopolymers, polypropylene oxide/ethylene oxide co-polymers, polyoxyethylated polyols and polyvinyl alcohols.

Other derivatives include covalent or aggregative conjugates of anti-Dkk-1 antibodies, or fragments thereof, with other proteins or polypeptides, such as by expression of recombinant fusion proteins comprising heterologous polypeptides fused to the N-terminus or C-terminus of an anti-Dkk-1 antibody polypeptide. For example, the conjugated peptide may be a heterologous signal (or leader) polypeptide, e.g., the yeast alpha-factor leader, or a peptide such as an epitope tag. Anti-Dkk-1 antibody-containing fusion proteins can comprise peptides added to facilitate purification or identification of the anti-Dkk-1 antibody (e.g., poly-His). An anti-Dkk-1 antibody polypeptide also can be linked to the FLAG peptide as described in Hopp et al., Bio/Technology 6:1204, 1988, and U.S. Pat. No. 5,011,912. The FLAG peptide is highly antigenic and provides an epitope reversibly bound by a specific monoclonal antibody (mAb), enabling rapid assay and facile purification of expressed recombinant protein. Reagents useful for preparing fusion proteins in which the FLAG peptide is fused to a given polypeptide are commercially available (Sigma, St. Louis, Mo.).

Oligomers that contain one or more anti-Dkk-1 antibody polypeptides may be employed as Dkk-1 antagonists. Oligomers may be in the form of covalently-linked or non-covalently-linked dimers, trimers, or higher oligomers. Oligomers comprising two or more anti-Dkk-1 antibody polypeptides are contemplated for use, with one example being a homodimer. Other oligomers include heterodimers, homotrimers, heterotrimers, homotetramers, heterotetramers, etc.

One embodiment is directed to oligomers comprising multiple anti-Dkk-1 antibody polypeptides joined via covalent or non-covalent interactions between peptide moieties fused to the anti-Dkk-1 antibody polypeptides. Such peptides may be peptide linkers (spacers), or peptides that have the property of promoting oligomerization. Leucine zippers and certain polypeptides derived from antibodies are among the peptides that can promote oligomerization of anti-Dkk-1 antibody polypeptides attached thereto, as described in more detail below.

In particular embodiments, the oligomers comprise from two to four anti-Dkk-1 antibody polypeptides. The anti-Dkk-1 antibody moieties of the oligomer may be in any of the forms described above, e.g., variants or fragments. Preferably, the oligomers comprise anti-Dkk-1 antibody polypeptides that have Dkk-1 binding activity.

In one embodiment, an oligomer is prepared using polypeptides derived from immunoglobulins. Preparation of fusion proteins comprising certain heterologous polypeptides fused to various portions of antibody-derived polypeptides (including the Fc domain) has been described, e.g., by Ashkenazi et al., 1991, PNAS USA 88:10535; Byrn et al., 1990, Nature 344:677; and Hollenbaugh et al., 1992 "Construction of Immunoglobulin Fusion Proteins", in Current Protocols in Immunology, Suppl. 4, pages 10.19.1-10.19.11.

One embodiment of the present invention is directed to a dimer comprising two fusion proteins created by fusing a Dkk-1 binding fragment of an anti-Dkk-1 antibody to the Fc region of an antibody. The dimer can be made by, for example, inserting a gene fusion encoding the fusion protein into an appropriate expression vector, expressing the gene fusion in host cells transformed with the recombinant expression vector, and allowing the expressed fusion protein to assemble much like antibody molecules, whereupon interchain disulfide bonds form between the Fc moieties to yield the dimer.

The term "Fc polypeptide" as used herein includes native and mutein forms of polypeptides derived from the Fc region of an antibody. Truncated forms of such polypeptides containing the hinge region that promotes dimerization also are included. Fusion proteins comprising Fc moieties (and oligomers formed therefrom) offer the advantage of facile purification by affinity chromatography over Protein A or Protein G columns.

One suitable Fc polypeptide, described in PCT application WO 93/10151 and U.S. Pat. Nos. 5,426,048 and 5,262,522 (each of which is hereby incorporated by reference), is a single chain polypeptide extending from the N-terminal hinge region to the native C-terminus of the Fc region of a human IgG1 antibody. Another useful Fc polypeptide is the Fc mutein described in U.S. Pat. No. 5,457,035 and in Baum et al., 1994, EMBO J. 13:3992-4001. The amino acid sequence of this mutein is identical to that of the native Fc sequence presented in WO 93/10151, except that amino acid 19 has been changed from Leu to Ala, amino acid 20 has been changed from Leu to Glu, and amino acid 22 has been changed from Gly to Ala. The mutein exhibits reduced affinity for Fc receptors.

In other embodiments, the variable portion of the heavy and/or light chains of an anti-Dkk-1 antibody such as disclosed herein may be substituted for the variable portion of an antibody heavy and/or light chain.

Alternatively, the oligomer is a fusion protein comprising multiple anti-Dkk-1 antibody polypeptides, with or without peptide linkers (spacer peptides). Among the suitable peptide linkers are those described in U.S. Pat. Nos. 4,751,180 and 4,935,233.

Another method for preparing oligomeric anti-Dkk-1 antibody derivatives involves use of a leucine zipper. Leucine zipper domains are peptides that promote oligomerization of the proteins in which they are found. Leucine zippers were originally identified in several DNA-binding proteins (Landschulz et al., 1988, Science 240:1759), and have since been found in a variety of different proteins. Among the known leucine zippers are naturally occurring peptides and derivatives thereof that dimerize or trimerize. Examples of leucine zipper domains suitable for producing soluble oligomeric proteins are described in PCT application WO 94/10308, and the leucine zipper derived from lung surfactant protein D (SPD) described in Hoppe et al., 1994, FEBS Letters 344:191, hereby incorporated by reference. The use of a modified leucine zipper that allows for stable trimerization of a heterologous protein fused thereto is described in Fanslow et al., 1994, Semin. Immunol. 6:267-78. In one approach, recombinant fusion proteins comprising an anti-Dkk-1 antibody fragment or derivative fused to a leucine zipper peptide are expressed in suitable host cells, and the soluble oligomeric anti-Dkk-1 antibody fragments or derivatives that form are recovered from the culture supernatant.

Some antibodies that are provided have a binding affinity (K.sub.a) for Dkk-1 of at least 10.sup.4 or 10.sup.5/M.times.seconds measured, for instance, as described in the examples below. Other antibodies have a k.sub.a of at least 10.sup.6, 10.sup.7, 10.sup.8 or 10.sup.9/M.times.seconds. Certain antibodies that are provided have a low disassociation rate. Some antibodies, for instance, have a K.sub.off of 1.times.10.sup.-4s.sup.-1, 1.times.10.sup.-5s.sup.-1 or lower. In another embodiment, the K.sub.off is the same as an antibody having the following combinations of variable region domains VL1VH1, VL1VH2, VL1VH3, VL1VH4, VL1VH5, VL1VH6, VL1VH7, VL1VH8, VL1VH9, VL1VH10, VL2VH1, VL2VH2, VL2VH3, VL2VH4, VL2VH5, VL2VH6, VL2VH7, VL2VH8, VL2VH9, VL2VH10, VL3VH1, VL3VH2, VL3VH3, VL3VH4, VL3VH5, VL3VH6, VL3VH7, VL3VH8, VL3VH9, VL3VH10.

In another aspect, the present invention provides an anti-Dkk-1 antibody having a half-life of at least one day in vitro or in vivo (e.g., when administered to a human subject). In one embodiment, the antibody has a half-life of at least three days. In another embodiment, the antibody or portion thereof has a half-life of four days or longer. In another embodiment, the antibody or portion thereof has a half-life of eight days or longer. In another embodiment, the antibody or antigen-binding portion thereof is derivatized or modified such that it has a longer half-life as compared to the underivatized or unmodified antibody. In another embodiment, the antibody contains point mutations to increase serum half life, such as described in WO 00/09560, published Feb. 24, 2000, incorporated by reference.

IV. Nucleic Acids

Nucleic acids that encode one or both chains of an antibody of the invention, or a fragment, derivative, mutein, or variant thereof, polynucleotides sufficient for use as hybridization probes, PCR primers or sequencing primers for identifying, analyzing, mutating or amplifying a polynucleotide encoding a polypeptide, anti-sense nucleic acids for inhibiting expression of a polynucleotide, and complementary sequences of the foregoing are also provided. The nucleic acids can be any length. They can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 125, 150, 175, 200, 250, 300, 350, 400, 450, 500, 750, 1,000, 1,500, 3,000, 5,000 or more nucleotides in length, and/or can comprise one or more additional sequences, for example, regulatory sequences, and/or be part of a larger nucleic acid, for example, a vector. The nucleic acids can be single-stranded or double-stranded and can comprise RNA and/or DNA nucleotides, and artificial variants thereof (e.g., peptide nucleic acids).

Nucleic acids that encode the epitope to which certain of the antibodies provided herein bind are also provided. Thus, some nucleic acids encode amino acids 221-229 and/or 246-253 of SEQ ID NO:2 are included, as are nucleic acids that encode amino acids 221-236 and/or 246-262 of SEQ ID NO:2 and those that encode amino acids 221 to 262 of SEQ ID NO:2 or amino acids 221-253 of SEQ ID NO:2. Nucleic acids encoding fusion proteins that include these peptides are also provided.

DNA encoding antibody polypeptides (e.g., heavy or light chain, variable domain only, or full length) may be isolated from B-cells of mice that have been immunized with Dkk-1 or an immunogenic fragment thereof. The DNA may be isolated by conventional procedures such as polymerase chain reaction (PCR). Phage display is another example of a known technique whereby derivatives of antibodies may be prepared. In one approach, polypeptides that are components of an antibody of interest are expressed in any suitable recombinant expression system, and the expressed polypeptides are allowed to assemble to form antibody molecules.

Exemplary nucleic acids that encode the light and heavy chains, variable regions and CDRs of the antibodies and immunologically functional fragments that are provided are listed in Tables 1-3 above. Due to the degeneracy of the genetic code, each of the polypeptide sequences listed in Tables 1-3 is also encoded by a large number of other nucleic acid sequences besides those listed in Tables 1-3. The present invention provides each degenerate nucleotide sequence encoding each antibody of the invention.

The invention further provides nucleic acids that hybridize to other nucleic acids (e.g., nucleic acids comprising a nucleotide sequence listed in Tables 1-3) under particular hybridization conditions. Methods for hybridizing nucleic acids are well-known in the art. See, e.g., Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6. As defined herein, a moderately stringent hybridization condition uses a prewashing solution containing 5.times. sodium chloride/sodium citrate (SSC), 0.5% SDS, 1.0 mM EDTA (pH 8.0), hybridization buffer of about 50% formamide, 6.times.SSC, and a hybridization temperature of 55.degree. C. (or other similar hybridization solutions, such as one containing about 50% formamide, with a hybridization temperature of 42.degree. C.), and washing conditions of 60.degree. C., in 0.5.times.SSC, 0.1% SDS. A stringent hybridization condition hybridizes in 6.times.SSC at 45.degree. C., followed by one or more washes in 0.1.times.SSC, 0.2% SDS at 68.degree. C. Furthermore, one of skill in the art can manipulate the hybridization and/or washing conditions to increase or decrease the stringency of hybridization such that nucleic acids comprising nucleotide sequences that are at least 65, 70, 75, 80, 85, 90, 95, 98 or 99% identical to each other typically remain hybridized to each other.

The basic parameters affecting the choice of hybridization conditions and guidance for devising suitable conditions are set forth by, for example, Sambrook, Fritsch, and Maniatis (1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., chapters 9 and 11; and Current Protocols in Molecular Biology, 1995, Ausubel et al., eds., John Wiley & Sons, Inc., sections 2.10 and 6.3-6.4), and can be readily determined by those having ordinary skill in the art based on, for example, the length and/or base composition of the DNA.

Changes can be introduced by mutation into a nucleic acid, thereby leading to changes in the amino acid sequence of a polypeptide (e.g., an antibody or antibody derivative of the invention) that it encodes. Mutations can be introduced using any technique known in the art. In one embodiment, one or more particular amino acid residues are changed using, for example, a site-directed mutagenesis protocol. In another embodiment, one or more randomly selected residues is changed using, for example, a random mutagenesis protocol. However it is made, a mutant polypeptide can be expressed and screened for a desired property.

Mutations can be introduced into a nucleic acid without significantly altering the biological activity of a polypeptide that it encodes. For example, one can make nucleotide substitutions leading to amino acid substitutions at non-essential amino acid residues. Alternatively, one or more mutations can be introduced into a nucleic acid that selectively change the biological activity of a polypeptide that it encodes. For example, the mutation can quantitatively or qualitatively change the biological activity. Examples of quantitative changes include increasing, reducing or eliminating the activity. Examples of qualitative changes include changing the antigen specificity of an antibody.

In another aspect, the present invention provides nucleic acid molecules that are suitable for use as primers or hybridization probes for the detection of nucleic acid sequences of the invention. A nucleic acid molecule of the invention can comprise only a portion of a nucleic acid sequence encoding a full-length polypeptide of the invention, for example, a fragment that can be used as a probe or primer or a fragment encoding an active portion (e.g., a Dkk-1 binding portion) of a polypeptide of the invention.

Probes based on the sequence of a nucleic acid of the invention can be used to detect the nucleic acid or similar nucleic acids, for example, transcripts encoding a polypeptide of the invention. The probe can comprise a label group, e.g., a radioisotope, a fluorescent compound, an enzyme, or an enzyme co-factor. Such probes can be used to identify a cell that expresses the polypeptide.

In another aspect, the present invention provides vectors comprising a nucleic acid encoding a polypeptide of the invention or a portion thereof (e.g., a fragment containing one or more CDRs or one or more variable region domains). Examples of vectors include, but are not limited to, plasmids, viral vectors, non-episomal mammalian vectors and expression vectors, for example, recombinant expression vectors. The recombinant expression vectors of the invention can comprise a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell. The recombinant expression vectors include one or more regulatory sequences, selected on the basis of the host cells to be used for expression, which is operably linked to the nucleic acid sequence to be expressed. Regulatory sequences include those that direct constitutive expression of a nucleotide sequence in many types of host cells (e.g., SV40 early gene enhancer, Rous sarcoma virus promoter and cytomegalovirus promoter), those that direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences, see Voss et al., 1986, Trends Biochem. Sci. 11:287, Maniatis et al., 1987, Science 236:1237, incorporated by reference herein in their entireties), and those that direct inducible expression of a nucleotide sequence in response to particular treatment or condition (e.g., the metallothionin promoter in mammalian cells and the tet-responsive and/or streptomycin responsive promoter in both prokaryotic and eukaryotic systems (see id.). It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc. The expression vectors of the invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as described herein.

In another aspect, the present invention provides host cells into which a recombinant expression vector of the invention has been introduced. A host cell can be any prokaryotic cell (for example, E. coli) or eukaryotic cell (for example, yeast, insect, or mammalian cells (e.g., CHO cells)). Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques. For stable transfection of mammalian cells, it is known that, depending upon the expression vector and transfection technique used, only a small fraction of cells may integrate the foreign DNA into their genome. In order to identify and select these integrants, a gene that encodes a selectable marker (e.g., for resistance to antibiotics) is generally introduced into the host cells along with the gene of interest. Preferred selectable markers include those which confer resistance to drugs, such as G418, hygromycin and methotrexate. Cells stably transfected with the introduced nucleic acid can be identified by drug selection (e.g., cells that have incorporated the selectable marker gene will survive, while the other cells die), among other methods.

V. Preparation of Antibodies

The non-human antibodies that are provided can be, for example, derived from any antibody-producing animal, such as mouse, rat, rabbit, goat, donkey, or non-human primate (such as monkey (e.g., cynomologous or rhesus monkey) or ape (e.g., chimpanzee)). Non-human antibodies can be used, for instance, in in vitro cell culture and cell-culture based applications, or any other application where an immune response to the antibody does not occur or is insignificant, can be prevented, is not a concern, or is desired. In certain embodiments of the invention, the antibodies may be produced by immunizing with full-length Dkk-1 or with the carboxy-terminal half of Dkk-1. Alternatively, the certain non-human antibodies may be raised by immunizing with amino acids 221-236 and/or amino acids 246-262 of SEQ ID NO:2, which are segments of human Dkk-1 that form part of the epitope to which certain antibodies provided herein bind (e.g., the 11H10, see FIG. 1). The antibodies may be polyclonal, monoclonal, or may be synthesized in host cells by expressing recombinant DNA.

Fully human antibodies may be prepared as described above by immunizing transgenic animals containing human immunoglobulin loci or by selecting a phage display library that is expressing a repertoire of human antibodies.

The monoclonal antibodies (mAbs) of the invention can be produced by a variety of techniques, including conventional monoclonal antibody methodology, e.g., the standard somatic cell hybridization technique of Kohler and Milstein, 1975, Nature 256: 495. Alternatively, other techniques for producing monoclonal antibodies can be employed, for example, the viral or oncogenic transformation of B-lymphocytes. One suitable animal system for preparing hybridomas is the murine system, which is a very well established procedure. Immunization protocols and techniques for isolation of immunized splenocytes for fusion are known in the art. For such procedures, B cells from immunized mice are fused with a suitable immortalized fusion partner, such as a murine myeloma cell line. If desired, rats or other mammals besides can be immunized instead of mice and B cells from such animals can be fused with the murine myeloma cell line to form hybridomas. Alternatively, a myeloma cell line from a source other than mouse may be used. Fusion procedures for making hybridomas also are well known.

The single chain antibodies that are provided may be formed by linking heavy and light chain variable domain (Fv region) fragments (see, e.g., Table 2) via an amino acid bridge (short peptide linker), resulting in a single polypeptide chain. Such single-chain Fvs (scFvs) may be prepared by fusing DNA encoding a peptide linker between DNAs encoding the two variable domain polypeptides (V.sub.L and V.sub.H). The resulting polypeptides can fold back on themselves to form antigen-binding monomers, or they can form multimers (e.g., dimers, trimers, or tetramers), depending on the length of a flexible linker between the two variable domains (Kortt et al., 1997, Prot. Eng. 10:423; Kortt et al., 2001, Biomol. Eng. 18:95-108). By combining different V.sub.L and V.sub.H-comprising polypeptides, one can form multimeric scFvs that bind to different epitopes (Kriangkum et al., 2001, Biomol. Eng. 18:31-40). Techniques developed for the production of single chain antibodies include those described in U.S. Pat. No. 4,946,778; Bird, 1988, Science 242:423; Huston et al., 1988, Proc. Natl. Acad. Sci. USA 85:5879; Ward et al., 1989, Nature 334:544, de Graaf et al., 2002, Methods Mol Biol. 178:379-87. Single chain antibodies derived from antibodies provided herein include, but are not limited to scFvs comprising the variable domain combinations: VL1VH1, VL1VH2, VL1VH3, VL1VH4, VL1VH5, VL1VH6, VL1VH7, VL1VH8, VL1VH9, VL1VH10, VL2VH1, VL2VH2, VL2VH3, VL2VH4, VL2VH5, VL2VH6, VL2VH7, VL2VH8, VL2VH9, VL2VH10, VL3VH1, VL3VH2, VL3VH3, VL3VH4, VL3VH5, VL3VH6, VL3VH7, VH3VL8, VL3VH9, VL3VH10.

Antibodies provided herein that are of one subclass can be changed to antibodies from a different subclass using subclass switching methods. Thus, IgG antibodies may be derived from an IgM antibody, for example, and vice versa. Such techniques allow the preparation of new antibodies that possess the antigen-binding properties of a given antibody (the parent antibody), but also exhibit biological properties associated with an antibody isotype or subclass different from that of the parent antibody. Recombinant DNA techniques may be employed. Cloned DNA encoding particular antibody polypeptides may be employed in such procedures, e.g., DNA encoding the constant domain of an antibody of the desired isotype. See, e.g., Lantto et al., 2002, Methods Mol. Biol. 178:303-16.

Accordingly, the antibodies that are provided include those comprising, for example, the following variable domain combinations: VL1VH1, VL1VH2, VL1VH3, VL1VH4, VL1VH5, VL1VH6, VL1VH7, VL1VH8, VL1VH9, VL1VH10, VL2VH1, VL2VH2, VL2VH3, VL2VH4, VL2VH5, VL2VH6, VL2VH7, VL2VH8, VL2VH9, VL2VH10, VL3VH1, VL3VH2, VL3VH3, VL3VH4, VL3VH5, VL3VH6, VL3VH7, VL3VH8, VL3VH9, VL3VH10 having a desired isotype (for example, IgA, IgG1, IgG2, IgG3, IgG4, IgM, IgE, and IgD) as well as Fab or F(ab').sub.2 fragments thereof. Moreover, if an IgG4 is desired, it may also be desired to introduce a point mutation (CPSCP.fwdarw.CPPCP) in the hinge region as described in Bloom et al., 1997, Protein Science 6:407, incorporated by reference herein) to alleviate a tendency to form intra-H chain disulfide bonds that can lead to heterogeneity in the IgG4 antibodies.

Moreover, techniques for deriving antibodies having different properties (i.e., varying affinities for the antigen to which they bind) are also known. One such technique, referred to as chain shuffling, involves displaying immunoglobulin variable domain gene repertoires on the surface of filamentous bacteriophage, often referred to as phage display. Chain shuffling has been used to prepare high affinity antibodies to the hapten 2-phenyloxazol-5-one, as described by Marks et al., 1992, BioTechnology, 10:779.

Conservative modifications may be made to the heavy and light chains described in Table 1 (and corresponding modifications to the encoding nucleic acids) to produce an anti-Dkk-1 antibody having functional and biochemical characteristics. Methods for achieving such modifications are described above.

Antibodies and functional fragments thereof according to the invention may be further modified in various ways. For example, if they are to be used for therapeutic purposes, they may be conjugated with polyethylene glycol (pegylated) to prolong the serum half-life or to enhance protein delivery. Alternatively, the V region of the subject antibodies or fragments thereof may be fused with the Fc region of a different antibody molecule. The Fc region used for this purpose may be modified so that it does not bind complement, thus reducing the likelihood of inducing cell lysis in the patient when the fusion protein is used as a therapeutic agent. In addition, the subject antibodies or functional fragments thereof may be conjugated with human serum albumin to enhance the serum half-life of the antibody or fragment thereof Another useful fusion partner for the inventive antibodies or fragments thereof is transthyretin (TTR). TTR has the capacity to form a tetramer, thus an antibody-TTR fusion protein can form a multivalent antibody which may increase its binding avidity.

Alternatively, substantial modifications in the functional and/or biochemical characteristics of the antibodies and fragments described herein may be achieved by creating substitutions in the amino acid sequence of the heavy and light chains that differ significantly in their effect on maintaining (a) the structure of the molecular backbone in the area of the substitution, for example, as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site, or (c) the bulkiness of the side chain. A "conservative amino acid substitution" may involve a substitution of a native amino acid residue with a nonnative residue that has little or no effect on the polarity or charge of the amino acid residue at that position. Furthermore, any native residue in the polypeptide may also be substituted with alanine, as has been previously described for alanine scanning mutagenesis.

Amino acid substitutions (whether conservative or non-conservative) of the subject antibodies can be implemented by those skilled in the art by applying routine techniques. Amino acid substitutions can be used to identify important residues of the antibodies provided herein, or to increase or decrease the affinity of these antibodies for human Dkk-1 or for modifying the binding affinity of other anti-Dkk-1 antibodies described herein.

VI. Expression of Anti-Dkk-1 Antibodies

The anti-Dkk-1 antibodies and immunological functional fragments can be prepared by any of a number of conventional techniques. For example, anti-Dkk-1 antibodies may be produced by recombinant expression systems, using any technique known in the art. See, for example, Monoclonal Antibodies, Hybridomas: A New Dimension in Biological Analyses, Kennet et al. (eds.) Plenum Press, New York (1980): and Antibodies: A Laboratory Manual, Harlow and Lane (eds.), Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1988).

Antibodies of the present invention can be expressed in hybridoma cell lines or in cell lines other than hybridomas. Expression constructs encoding the antibodies can be used to transform a mammalian, insect or microbial host cell. Transformation can be performed using any known method for introducing polynucleotides into a host cell, including, for example packaging the polynucleotide in a virus or bacteriophage and transducing a host cell with the construct by transfection procedures known in the art, as exemplified by U.S. Pat. Nos. 4,399,216, 4,912,040, 4,740,461, and 4,959,455 (which patents are hereby incorporated herein by reference for any purpose). The optimal transformation procedure used will depend upon which type of host cell is being transformed. Methods for introduction of heterologous polynucleotides into mammalian cells are well known in the art and include, but are not limited to, dextran-mediated transfection, calcium phosphate precipitation, polybrene mediated transfection, protoplast fusion, electroporation, encapsulation of the polynucleotide(s) in liposomes, mixing nucleic acid with positively-charged lipids, and direct microinjection of the DNA into nuclei.

Recombinant expression constructs of the invention typically comprise a nucleic acid molecule encoding a polypeptide comprising one or more of the following: a heavy chain constant region (e.g., C.sub.H1, C.sub.H.sup.2 and/or C.sub.H.sup.3); a heavy chain variable region; a light chain constant region; a light chain variable region; one or more CDRs of the light or heavy chain of the anti-Dkk-1 antibody. These nucleic acid sequences are inserted into an appropriate expression vector using standard ligation techniques. In one embodiment, the 11H10 heavy or light chain constant region is appended to the C-terminus of the Dkk-1-specific heavy or light chain variable region and is ligated into an expression vector. The vector is typically selected to be functional in the particular host cell employed (i.e., the vector is compatible with the host cell machinery, permitting amplification and/or expression of the gene can occur). In some embodiments, vectors are used that employ protein-fragment complementation assays using protein reporters, such as dihydrofolate reductase (see, for example, U.S. Pat. No. 6,270,964, which is hereby incorporated by reference). Suitable expression vectors can be purchased, for example, from Invitrogen Life Technologies or BD Biosciences (formerly "Clontech"). Other useful vectors for cloning and expressing the antibodies and fragments of the invention include those described in Bianchi and McGrew, Biotech Biotechnol Bioeng 84(4):439-44 (2003), which is hereby incorporated by reference. Additional suitable expression vectors are discussed, for example, in Methods Enzymol, vol. 185 (D. V. Goeddel, ed.), 1990, New York: Academic Press, which is hereby incorporated by reference.

Typically, expression vectors used in any of the host cells contain sequences for plasmid or virus maintenance and for cloning and expression of exogenous nucleotide sequences. Such sequences, collectively referred to as "flanking sequences" typically include one or more of the following operatively linked nucleotide sequences: a promoter, one or more enhancer sequences, an origin of replication, a transcriptional termination sequence, a complete intron sequence containing a donor and acceptor splice site, a sequence encoding a leader sequence for polypeptide secretion, a ribosome binding site, a polyadenylation sequence, a polylinker region for inserting the nucleic acid encoding the polypeptide to be expressed, and a selectable marker element.

Optionally, the vector may contain a "tag"-encoding sequence, that is, an oligonucleotide molecule located at the 5' or 3' end of the coding sequence, the oligonucleotide sequence encoding polyHis (such as hexaHis), or another "tag" for which commercially available antibodies exist, such as FLAG.RTM., HA (hemaglutinin from influenza virus), or myc. The tag is typically fused to the antibody protein upon expression, and can serve as a means for affinity purification of the antibody from the host cell. Affinity purification can be accomplished, for example, by column chromatography using antibodies against the tag as an affinity matrix. Optionally, the tag can subsequently be removed from the purified antibody polypeptide by various means such as using certain peptidases for cleavage.

Flanking sequences in the expression vector may be homologous (i.e., from the same species and/or strain as the host cell), heterologous (i.e., from a species other than the host cell species or strain), hybrid (i.e., a combination of flanking sequences from more than one source), synthetic or native. As such, the source of a flanking sequence may be any prokaryotic or eukaryotic organism, any vertebrate or invertebrate organism, or any plant, provided that the flanking sequence is functional in, and can be activated by, the host cell machinery.

Flanking sequences useful in the vectors of this invention may be obtained by any of several methods well known in the art. Typically, flanking sequences useful herein will have been previously identified by mapping and/or by restriction endonuclease digestion and can thus be isolated from the proper tissue source using the appropriate restriction endonucleases. In some cases, the full nucleotide sequence of a flanking sequence may be known. Here, the flanking sequence may be synthesized using the methods described herein for nucleic acid synthesis or cloning.

Where all or only a portion of the flanking sequence is known, it may be obtained using PCR and/or by screening a genomic library with a suitable oligonucleotide and/or flanking sequence fragment from the same or another species. Where the flanking sequence is not known, a fragment of DNA containing a flanking sequence may be isolated from a larger piece of DNA that may contain, for example, a coding sequence or even another gene or genes. Isolation may be accomplished by restriction endonuclease digestion to produce the proper DNA fragment followed by isolation using agarose gel purification, Qiagen.RTM. column chromatography (Chatsworth, Calif.), or other methods known to the skilled artisan. The selection of suitable enzymes to accomplish this purpose will be readily apparent to those skilled in the art.

An origin of replication is typically a part of prokaryotic expression vectors, particularly those purchased commercially, and the origin aids in the amplification of the vector in a host cell. If the vector of choice does not contain an origin of replication site, one may be chemically synthesized based on a known sequence, and ligated into the vector. For example, the origin of replication from the plasmid pBR322 (New England Biolabs, Beverly, Mass.) is suitable for most gram-negative bacteria and various origins (e.g., SV40, polyoma, adenovirus, vesicular stomatitis virus (VSV), or papillomaviruses such as HPV or BPV) are useful for cloning vectors in mammalian cells. Generally, a mammalian origin of replication is not needed for mammalian expression vectors (for example, the SV40 origin is often used only because it contains the early promoter).

The expression and cloning vectors of the present invention will typically contain a promoter that is recognized by the host organism and operably linked to nucleic acid encoding the anti-Dkk-1 antibody or immunologically functional fragment thereof Promoters are untranscribed sequences located upstream (i.e., 5') to the start codon of a structural gene (generally within about 100 to 1000 bp) that control transcription of the structural gene. Promoters are conventionally grouped into one of two classes: inducible promoters and constitutive promoters. Inducible promoters initiate increased levels of transcription from DNA under their control in response to some change in culture conditions, such as the presence or absence of a nutrient or a change in temperature. Constitutive promoters, on the other hand, initiate continuous gene product production; that is, there is little or no experimental control over gene expression. A large number of promoters, recognized by a variety of potential host cells, are well known. A suitable promoter is operably linked to the DNA encoding anti-Dkk-1 antibody by removing the promoter from the source DNA by restriction enzyme digestion or amplifying the promoter by polymerase chain reaction and inserting the desired promoter sequence into the vector.

Suitable promoters for use with yeast hosts are also well known in the art. Yeast enhancers are advantageously used with yeast promoters. Suitable promoters for use with mammalian host cells are well known and include, but are not limited to, those obtained from the genomes of viruses such as polyoma virus, fowlpox virus, adenovirus (such as Adenovirus 2), bovine papilloma virus, avian sarcoma virus, cytomegalovirus, retroviruses, hepatitis-B virus and most preferably Simian Virus 40 (SV40). Other suitable mammalian promoters include heterologous mammalian promoters, for example, heat-shock promoters and the actin promoter.

Particular promoters useful in the practice of the recombinant expression vectors of the invention include, but are not limited to: the SV40 early promoter region (Bemoist and Chambon, 1981, Nature 290: 304-10); the CMV promoter; the promoter contained in the 3' long terminal repeat of Rous sarcoma virus (Yamamoto, et al., 1980, Cell 22: 787-97); the herpes thymidine kinase promoter (Wagner et al., 1981, Proc. Natl. Acad. Sci. U.S.A. 78: 1444-45); the regulatory sequences of the metallothionine gene (Brinster et al., 1982, Nature 296: 39-42); prokaryotic expression vectors such as the beta-lactamase promoter (Villa-Kamaroff et al., 1978, Proc. Natl. Acad. Sci. U.S.A., 75: 3727-31); or the tac promoter (DeBoer et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80: 21-25). Also available for use are the following animal transcriptional control regions, which exhibit tissue specificity and have been utilized in transgenic animals: the elastase I gene control region that is active in pancreatic acinar cells (Swift et al., 1984, Cell 38: 63946; Ornitz et al., 1986, Cold Spring Harbor Symp. Quant. Biol. 50: 399409; MacDonald, 1987, Hepatology 7: 425-515); the insulin gene control region that is active in pancreatic beta cells (Hanahan, 1985, Nature 315: 115-22); the mouse mammary tumor virus control region that is active in testicular, breast, lymphoid and mast cells (Leder et al., 1986, Cell 45: 485-95); the albumin gene control region that is active in liver (Pinkert et al., 1987, Genes and Devel. 1: 268-76); the alpha-feto-protein gene control region that is active in liver (Krumlauf et al., 1985, Mol. Cell. Biol. 5: 1639-48; Hammer et al., 1987, Science 235: 53-58); the alpha 1-antitrypsin gene control region that is active in the liver (Kelsey et al., 1987, Genes and Devel. 1: 161-71); the beta-globin gene control region that is active in myeloid cells (Mogram et al., 1985, Nature 315: 338-40; Kollias et al., 1986, Cell 46: 89-94); the myelin basic protein gene control region that is active in oligodendrocyte cells in the brain (Readhead et al., 1987, Cell 48: 703-12); the myosin light chain-2 gene control region that is active in skeletal muscle (Sani, 1985, Nature 314: 283-86); the gonadotropic releasing hormone gene control region that is active in the hypothalamus (Mason et al., 1986, Science 234: 1372-78); and most particularly the immunoglobulin gene control region that is active in lymphoid cells (Grosschedl et al., 1984, Cell 38: 647-58; Adames et al., 1985, Nature 318: 533-38; Alexander et al., 1987, Mol. Cell Biol. 7: 1436-44).

An enhancer sequence may be inserted into the vector to increase the transcription in higher eukaryotes of a nucleic acid encoding an anti-Dkk-1 antibody or immunologically functional fragment thereof of the present invention. Enhancers are cis-acting elements of DNA, usually about 10-300 bp in length, that act on promoters to increase transcription. Enhancers are relatively orientation and position independent. They have been found 5' and 3' to the transcription unit. Several enhancer sequences available from mammalian genes are known (e.g., globin, elastase, albumin, alpha-feto-protein and insulin). An enhancer sequence from a virus also can be used. The SV40 enhancer, the cytomegalovirus early promoter enhancer, the polyoma enhancer, and adenovirus enhancers are exemplary enhancing elements for the activation of eukaryotic promoters. While an enhancer may be spliced into the vector at a position 5' or 3' to a nucleic acid molecule, it is typically placed at a site 5' to the promoter.

In expression vectors, a transcription termination sequence is typically located 3' of the end of a polypeptide-coding region and serves to terminate transcription. A transcription termination sequence used for expression in prokaryotic cells typically is a G-C rich fragment followed by a poly-T sequence. While the sequence is easily cloned from a library or even purchased commercially as part of a vector, it can also be readily synthesized using methods for nucleic acid synthesis such as those described herein.

A selectable marker gene element encodes a protein necessary for the survival and growth of a host cell grown in a selective culture medium. Typical selection marker genes used in expression vectors encode proteins that (a) confer resistance to antibiotics or other toxins, e.g., ampicillin, tetracycline, or kanamycin for prokaryotic host cells; (b) complement auxotrophic deficiencies of the cell; or (c) supply critical nutrients not available from complex media. Examples of selectable markers include the kanamycin resistance gene, the ampicillin resistance gene and the tetracycline resistance gene. A bacterial neomycin resistance gene can also be used for selection in both prokaryotic and eukaryotic host cells.

Other selection genes can be used to amplify the gene that will be expressed. Amplification is a process whereby genes that cannot in single copy be expressed at high enough levels to permit survival and growth of cells under certain selection conditions are reiterated in tandem within the chromosomes of successive generations of recombinant cells. Examples of suitable amplifiable selectable markers for mammalian cells include dihydrofolate reductase (DHFR) and promoterless thymidine kinase. In the use of these markers mammalian cell transformants are placed under selection pressure wherein only the transformants are uniquely adapted to survive by virtue of the selection gene present in the vector. Selection pressure is imposed by culturing the transformed cells under conditions in which the concentration of selection agent in the medium is successively increased, thereby permitting survival of only those cells in which the selection gene has been amplified. Under these circumstances, DNA adjacent to the selection gene, such as DNA encoding an antibody of the invention, is co-amplified with the selection gene. As a result, increased quantities of anti-Dkk-1 polypeptide are synthesized from the amplified DNA.

A ribosome-binding site is usually necessary for translation initiation of mRNA and is characterized by a Shine-Dalgarno sequence (prokaryotes) or a Kozak sequence (eukaryotes). The element is typically located 3' to the promoter and 5' to the coding sequence of the polypeptide to be expressed.

In some cases, for example where glycosylation is desired in a eukaryotic host cell expression system, various presequences can be manipulated to improve glycosylation or yield. For example, the peptidase cleavage site of a particular signal peptide can be altered, or pro-sequences added, which also may affect glycosylation. The final protein product may have, in the -1 position (relative to the first amino acid of the mature protein) one or more additional amino acids incident to expression, which may not have been totally removed. For example, the final protein product may have one or two amino acid residues found in the peptidase cleavage site, attached to the amino-terminus. Alternatively, use of some enzyme cleavage sites may result in a slightly truncated yet active form of the desired polypeptide, if the enzyme cuts at such area within the mature polypeptide.

Where a commercially available expression vector lacks some of the desired flanking sequences as described above, the vector can be modified by individually ligating these sequences into the vector. After the vector has been chosen and modified as desired, a nucleic acid molecule encoding an anti-Dkk-1 antibody or immunologically functional fragment thereof is inserted into the proper site of the vector.

The completed vector containing sequences encoding the inventive antibody or immunologically functional fragment thereof is inserted into a suitable host cell for amplification and/or polypeptide expression. The transformation of an expression vector for an anti-Dkk-1 antibody immunologically functional fragment thereof into a selected host cell may be accomplished by well-known methods including methods such as transfection, infection, calcium chloride, electroporation, microinjection, lipofection, DEAE-dextran method, or other known techniques. The method selected will in part be a function of the type of host cell to be used. These methods and other suitable methods are well known to the skilled artisan.

The transformed host cell, when cultured under appropriate conditions, synthesizes an anti-Dkk-1 antibody or functional fragment thereof that can subsequently be collected from the culture medium (if the host cell secretes it into the medium) or directly from the host cell producing it (if it is not secreted). The selection of an appropriate host cell will depend upon various factors, such as desired expression levels, polypeptide modifications that are desirable or necessary for activity (such as glycosylation or phosphorylation) and ease of folding into a biologically active molecule.

Mammalian cell lines available as hosts for expression are well known in the art and include, but are not limited to, many immortalized cell lines available from the American Type Culture Collection (ATCC), such as Chinese hamster ovary (CHO) cells, HeLa cells, baby hamster kidney (BHK) cells, monkey kidney cells (COS), human hepatocellular carcinoma cells (e.g., Hep G2), and a number of other cell lines. In certain embodiments, the best cell line for expressing a particular DNA construct may be selected by testing various cell lines to determine which ones have the highest levels of expression levels and produce antibodies with constitutive Dkk-1 binding properties.
 

Claim 1 of 24 Claims

1. An isolated antibody or immunologically functional fragment thereof, comprising: (a) the following three light chain (LC) complementary determining regions (CDRs): (i) a LC CDR1 comprising the amino acid sequence of SEQ ID NO:70; (ii) a LC CDR2 comprising the amino acid sequence of SEQ ID NO:72; and (iii) a LC CDR3 comprising the amino acid sequence of SEQ ID NO:74; and (b) the following three heavy chain (HC) CDRs: (i) a HC CDR1 with comprising the amino acid sequence of SEQ ID NO:76; (ii) a HC CDR2 comprising the amino acid sequence of SEQ ID NO:78; and (iii) a HC CDR3 comprising the amino acid sequence of SEQ ID NO:80, wherein the antibody or immunologically functional fragment thereof can specifically bind a Dkk-1 polypeptide consisting of amino acids 32-266 of SEQ ID NO:2 or amino acids 32 272 of SEQ ID NO:4.

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