Chicken antibody transformed into cysteine and site-specific conjugation using same

The present invention relates to engineered chicken antibodies which are modified with cysteine residues, and more particularly, to antibodies with application for treatment or diagnosis of diseases. The cysteine-modified antibodies may be conjugated with chemotherapeutic drugs, toxins, peptides, affinity ligands such as biotin, and detection labels such as radioisotopes and fluorophores, and used in the diagnosis or treatment of diseases.

Antibodies are widely used for diagnosis and treatment. Antibodies may have improved functions or may be provided with new functions by chemical binding with drugs, enzymes, dyes, peptides, aptamers, linkers, toxins, isotopes, etc. In the chemical binding with these substances, functional groups such as OH group of a tyrosine residue, NH 3 group of a lysine residue, or a carboxyl group of aspartic acid or glutamic acid of antibodies are involved (literature [Goldenberg D. M. et al., J. Med. (1978) 298:1384-1386; Rainsbury R. M. et al., Lancet (1983) 2:934-938; and Yamada H. et al., Biochemistry (1981) 20:4836-4842]).

However, these functional groups are also present in the antigen-binding sites. Therefore, if the residues in the antigen-binding sites are involved in the chemical binding, affinity of antibody to antigen may be affected. Further, in the binding reaction using cysteine, reduction of disulfide bonds within a chain (polypeptide) of an antibody molecule or between the chains is a prerequisite, which may affect activity of the protein (literature [Stimmel J. B. et al., J. Biol. Chem. (2000) 273: 30445-30450]). Further, proteins may be rendered inactive or non-specific by misfolding or loss of a tertiary structure (literature [Zhang W. et al., Anal. Biochem. (2002) 311:1-9]).

Site-specific conjugation is preferred over random amino modification as it enables chemical modification of a site away from the binding site, promoting complete retention of biological activity and allowing control over the possible number of prosthetic groups added. Cysteine-engineered antibodies have been conjugated through linkers at the newly introduced cysteine thiols with thiol-reactive linker reagents and drug-linker reagents to prepare cysteine-engineered antibody drug conjugates with anti-cancer properties, for example, anti-MUC16 (US 2008/0311134), anti-CD22 (US 2008/0050310), anti-ROBO4 (US 2008/0247951), anti-TENB2 (US 2009/0117100), anti-CD79B (US 2009/0028856; US 2009/0068202) thio ADC. However, one or more antibody heavy-chain and light-chain variable region genes exist in human or other animals, and as a result, each different antibody has a different framework sequence. Accordingly, there is a problem that the cysteine introduction site should be optimized with respect to respective antibodies.

Technical Problem

An aspect of the present invention provides a framework fragment of a chicken antibody, in which a cysteine residue is introduced into a framework region present in a heavy chain variable region or a light chain variable region, a heavy chain variable region or a light chain variable region including the framework fragment, or an antibody including the heavy chain variable region or the light chain variable region.

Another aspect of the present invention provides a conjugate including the antibody or an antigen-binding fragment thereof and a conjugation compound, the conjugate being prepared by conjugating the conjugation compound, such as a chemotherapeutic drug, an enzyme, an aptamer, a toxin, an affinity ligand, or a detection label, to the introduced cysteine residue which is present in the framework fragment of the chicken antibody, the heavy chain variable region or light chain variable region including the framework fragment, or the chicken antibody including the heavy chain variable region or light chain variable region.

Still another aspect provides use of the conjugate including the antibody or the antigen-binding fragment thereof and the conjugation compound in the diagnosis or treatment of a disease.

Technical Solution

The present inventors have selected a residue which is able to maintain antibody activity and affinity although replaced by cysteine, from various amino acid residues present in framework regions in heavy chain variable region and light chain variable region of a chicken antibody, and also provided a framework fragment in a heavy chain variable region and light chain variable region of a chicken antibody, in which a particular amino acid of the framework fragment is modified with cysteine, a heavy chain variable region or light chain variable region including the framework, and an antibody including the heavy chain variable region or light chain variable region, or an antigen-binding fragment thereof.

Preferably, the cysteine-introduced site does not induce formation of disulfide bonds between antibody molecules so that no dimers are formed or a small amount of dimers is formed. Therefore, reactivity of cysteine is maintained. The antibody introduced with the cysteine or the antigen-binding fragment thereof easily binds with a conjugation compound such as a chemotherapeutic drug, an enzyme, an aptamer, a toxin, an affinity ligand, or a detection label, thereby being applied to various fields for diagnosis or treatment of diseases.

Further, the cysteine-modified framework according to the present invention, the heavy chain variable region or light chain variable region including the framework, and the antibody including the heavy chain variable region or light chain variable region or the antigen-binding fragment thereof are derived from a chicken antibody, and the chicken antibody possess one heavy chain variable region gene and one light chain variable region, unlike antibodies of humans or other animals. For this reason, all antibodies have the identical frameworks. Therefore, in the cysteine-modified framework according to the present invention or the antibody including the same, cysteines are located at the same positions, and thus equally applied to all antibodies produced in chickens.

Hereinafter, the present invention will be described in more detail.

An antibody according to an embodiment of the present invention is an antibody including a framework, in which one or more amino acid residues present in a framework region in a heavy chain variable region and a light chain variable region derived from a chicken antibody are replaced by cysteines.

An antibody according to another embodiment of the present invention is an antibody including the framework, in which one or more amino acid residues present in a framework region in a heavy chain variable region and a light chain variable region derived from a chicken antibody are replaced by cysteines, and one or more of the two amino acids flanking both sides of the replaced cysteine are additionally replaced by one or more charged amino acids selected from the group consisting of aspartic acid, glutamic acid, arginine, and lysine.

In the present invention, preparation of the modified antibody including the framework having the replaced cysteine is performed by using a chicken antibody possessing one heavy chain variable region gene and one light chain variable region gene, and thus the cysteine-modified antibody may be rapidly prepared without respective optimization of the introduction site of cysteine residue, unlike antibodies of humans or other animals having a plurality of heavy chain and light chain variable region genes.

In the present invention, the antibody (Cys), in which one or more amino acid residues present in the framework region in the heavy chain variable region and the light chain variable region derived from the chicken antibody are replaced by cysteine, is advantageous in that two or more amino acids as well as one amino acid are replaced by cysteines, and therefore, two conjugation compounds are conjugated thereto, or two or more different conjugation compounds are conjugated thereto to prepare a conjugate having various functions.

Further, the modified antibody according to the present invention is also advantageous in that in addition to the cysteine replacement, at least one amino acid of the two amino acids flanking both sides of the replaced cysteine is replaced by one or more charged amino acids selected from the group consisting of aspartic acid, glutamic acid, arginine, and lysine, thereby effectively inducing a covalent bond with a substance having an opposite charge, and inhibiting formation of disulfide bonds between the cysteine-modified antibodies having the same local charges to prevent antibody aggregation, and replacement of the amino acid with negatively charged aspartic acid or glutamic acid inhibits the breakage of maleimide bonds (literature [Shen B. Q. et al., Nat. Biotechnol. (2012) 30: 184-189]).

In the present invention, the amino acid at position replaceable with cysteine is an amino acid other than cysteine. Any amino acid located within the framework may be replaced, as long as it is able to maintain antibody activity and affinity even though replaced by cysteine.

The amino acids to be replaced, satisfying the above conditions, are located within the framework which is present in the light chain variable region of a chicken antibody, including framework 1 of SEQ ID NO: 1, framework 2 of SEQ ID NO: 2, framework 3 of SEQ ID NO: 3, and framework 4 of SEQ ID NO: 4, and structures of these frameworks are shown in detail in FIG. 1 a.

In an embodiment of the present invention, the modified antibody may be an antibody including only a modified framework of the light chain variable region, only a modified framework of the heavy chain variable region, or both of the modified framework of the light chain variable region and the modified framework of the heavy chain variable region.

In the framework present in the light chain variable region of the chicken antibody, the amino acid to be replaced by cysteine is located at one or more positions selected from the group consisting of positions 3, 4, 5, 12, and 16 in the amino acid sequence of SEQ ID NO: 1 by sequential numbering (corresponding to positions 5, 6, 7, 14, and 18 by Kabat numbering),

positions 31 and 40 in the amino acid sequence of SEQ ID NO: 2 by sequential numbering (corresponding to positions 37 and 45 by Kabat numbering),

positions 52, 53, 56, 58, 59, 60, 61, 64, 65, 71, 78, and 82 in the amino acid sequence of SEQ ID NO: 3 by sequential numbering (corresponding to positions 57, 58, 61, 63, 64, 65, 66, 69, 70, 76, 83, and 87 by Kabat numbering), and

positions 98 and 102 in the amino acid sequence of SEQ ID NO: 4 by sequential numbering (corresponding to positions 102 and 106 by Kabat numbering).

In the framework present in the light chain variable region, the position of the amino acid replaceable by cysteine is shown in Table 1a.

The amino acids to be replaced, satisfying the above conditions, are located within the framework which is present in the heavy chain variable region of a chicken antibody, including framework 1 of SEQ ID NO: 5, framework 2 of SEQ ID NO: 6, framework 3 of SEQ ID NO: 7, and framework 4 of SEQ ID NO: 8, and structures of these frameworks are shown in detail in FIG. 1 a.

In the framework present in the heavy chain variable region of the chicken antibody, the amino acid to be replaced by cysteine is located at one or more positions selected from the group consisting of positions 1, 3, 5, 6, 7, 11, 12, 13, 16, 18, 19, 24, and 25 in the amino acid sequence of SEQ ID NO: 5 by sequential numbering (corresponding to positions 1, 3, 5, 6, 7, 11, 12, 13, 16, 18, 19, 24, and 25 by Kabat numbering),

positions 42 and 48 in the amino acid sequence of SEQ ID NO: 6 by sequential numbering (corresponding to positions 42 and 48 by Kabat numbering),

positions 70, 73, 75, 76, 78, 87, 88, 89, 91, and 93 in the amino acid sequence of SEQ ID NO: 7 by sequential numbering (corresponding to positions 69, 72, 74, 75, 77, 83, 84, 85, 87, and 89 by Kabat numbering), and

positions 123 and 126 in the amino acid sequence of SEQ ID NO: 8 by sequential numbering (corresponding to positions 110 and 113 by Kabat numbering).

In the framework present in the heavy chain variable region, the position of the amino acid replaceable by cysteine is shown in Table 1b.

Further, in the light chain variable region, the amino acid to be replaced by cysteine may be preferably located at one or more positions selected from the group consisting of positions 3, 4 and 5 in the amino acid sequence of SEQ ID NO: 1 by sequential numbering (corresponding to positions 5, 6, and 7 by Kabat numbering). In the heavy chain variable region, the amino acid to be replaced by cysteine may be preferably located at one or more positions selected from the group consisting of positions 13 and 16 in the amino acid sequence of SEQ ID NO: 5 by sequential numbering (corresponding to positions 13 and 16 by Kabat numbering).

In an embodiment of the present invention, at least one of the two amino acids flanking both sides of the replaced cysteine may be replaced by one or more charged amino acids selected from the group consisting of aspartic acid, glutamic acid, arginine, and lysine, in addition to replacement of cysteine at the preferred amino acid position. With respect to the modified antibody, for example, when the amino acid to be replaced by cysteine in the light chain variable region is preferably located at one or more positions selected from the group consisting of positions 3, 4 and 5 in the amino acid sequence of SEQ ID NO: 1 by sequential numbering, or the amino acid to be replaced by cysteine in the heavy chain variable region is preferably located at one or more positions selected from the group consisting of positions 13 and 16 in the amino acid sequence of SEQ ID NO: 5 by sequential numbering, the framework in which the amino acids flanking both sides of the replaced cysteine are replaced by charged amino acids may include modified sequences of Tables 3a and 3b.

Therefore, the modified antibody including replacement of adjacent amino acids as well as replacement of cysteine may be an antibody including a modified light chain variable region having one or more selected from the group consisting of amino acid sequences of SEQ ID NO: 57 to SEQ ID NO: 88, a modified heavy chain variable region having one or more selected from the group consisting of amino acid sequences of SEQ ID NO: 57 to SEQ ID NO: 88, or both of the modified light chain variable region and the modified heavy chain variable region.

Unless stated otherwise, the terms and phrases as used herein are intended to have the following meanings. As used herein, the term “antibody” is used in the broadest sense, and specifically, covers monoclonal antibodies, polyclonal antibodies, dimers, multimers, multispecific antibodies (e.g., bispecific antibodies), and antibody fragments exhibiting the desired biological activity. Antibodies may be murine, human, humanized, chimeric antibodies, or derived from other species. An antibody includes a full-length immunoglobulin molecule or an immunologically active portion of a full-length immunoglobulin molecule, i.e., a molecule containing an antigen binding site that immunospecifically binds a target antigen (such targets including, but not limited to, cancer cells or cells producing autoimmune antibodies associated with an autoimmune disease) or part thereof. The immunoglobulin disclosed herein may be of any type (e.g., IgG, IgE, IgM, IgD, and IgA), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass of immunoglobulin molecule. The immunoglobulins may be derived from any species.

As used herein, the term “antibody fragments” includes a portion of a full length antibody, generally the antigen binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′) 2 , and Fv fragments; diabodies; linear antibodies; minibodies (literature [Olafsen T. et al. Protein Eng. Design & Sel. (2004) 17:315-323]), fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, CDR (complementary determining region), and epitope-binding fragments of any of the above which immunospecifically bind to cancer cell antigens, viral antigens or microbial antigens, single-chain antibody molecules; and multispecific antibodies formed from antibody fragments.

In the present invention, the cysteine-substituted antibody may be prepared by a method including 1) inducing a mutation in a nucleic acid sequence encoding the cysteine-substituted antibody; 2) expressing the cysteine-substituted antibody; and 3) isolating and purifying the cysteine-substituted antibody. Further, the replacement of amino acids flanking both sides of the cysteine may be also performed in the same manner as in the replacement of cysteine.

In another specific embodiment of the present invention, provided is a conjugate including the modified antibody according to the present invention or an antigen-binding fragment thereof and a conjugation compound, the conjugate being prepared by conjugating the conjugation compound, such as a chemotherapeutic drug, an enzyme, a peptide, an aptamer, a toxin, an affinity ligand, or a detection label, to the modified antibody. According to the type of the conjugation compound, the conjugate may be variously applied to diagnosis or treatment of diseases.

In still another embodiment of the present invention, the antibody chemically binding to a peptide may further have a function of contributing to peptide affinity, such as effective penetration across the blood brain barrier via its receptor (literature [Chacko A. M et al., Expert Opin. Drug Deliv. (2013) 10: 907-26; patent: EP2 233 156 B 1]).

The conjugation compound may functions to (i) provide a detectable signal, (ii) interact with a second label to modify the detectable signal provided by the first or second label, e.g. FRET (fluorescence resonance energy transfer), (iii) stabilize interactions or increase affinity of binding, with antigen or ligand, (iv) affect mobility, e.g. electrophoretic mobility, or cell-permeability, by charge, hydrophobicity, shape, or other physical parameters, or (v) provide a capture moiety, in order to modulate ligand affinity, antibody/antigen binding, or ionic complexation.

Labeled cysteine-substituted antibodies may be useful in diagnostic assays, e.g., for detecting expression of an antigen of interest in specific cells, tissues, or serum. For diagnostic applications, the antibody will typically be labeled with a detectable moiety. Numerous labels are available which may be generally grouped into the following categories:

(a) Radioisotopes (radionuclides), such as 3 H, 11 C, 14 C, 18 F, 32 P, 35 S, 64 Cu, 68 Ga, 86 Y, 89 Zr, 99 Tc, 111 In, 123 I, 124 I, 125 I, 131 I, 133 Xe, 177 Lu, 211 At, or 213 Bi. Radioisotope-labeled antibodies are useful in receptor targeted imaging experiments. The antibody may be labeled with ligand reagents that bind, chelate or otherwise complex a radioisotope metal where the reagent is reactive with the engineered cysteine thiol of the antibody.

(b) Fluorescent labels such as rare earth chelates (europium chelates), fluorescein types including FITC, 5-carboxyfluorescein, 6-carboxy fluorescein, etc.; rhodamine types including TAMRA, etc.; dansyl; Lissamine; cyanines; phycoerythrins; Texas Red; and analogs thereof. Fluorescent dyes and fluorescent label reagents include those which are commercially available from Invitrogen/Molecular Probes (Eugene, Oreg., USA) and Pierce Biotechnology, Inc. (Rockford, Ill., USA).

(c) Various enzyme-substrate labels are available or disclosed in literatures (U.S. Pat. No. 4,275,149). The enzyme generally catalyzes a chemical alteration of a chromogenic substrate that may be measured using various techniques. For example, the enzyme may catalyze a color change in a substrate, which may be measured spectrophotometrically. Alternatively, the enzyme may alter the fluorescence or chemiluminescence of the substrate. Techniques for quantifying a change in fluorescence are described above. Examples of enzymatic labels include luciferase, urease, peroxidase such as horseradish peroxidase (HRP), alkaline phosphatase (AP), β-galactosidase, glucoamylase, lysozyme, saccharide oxidase, etc. Techniques for conjugating enzymes to antibodies may be performed by a general method.

In still another embodiment, the cysteine-substituted antibody may be labeled through the cysteine thiol with radionuclides, fluorescent dyes, bioluminescence-triggering substrate moieties, chemiluminescence-triggering substrate moieties, enzymes, and other detection labels for imaging experiments with diagnostic, pharmacodynamic, and therapeutic applications. Generally, the labeled cysteine engineered antibody, i.e. “biomarker” or “probe”, is administered by injection, perfusion, or oral ingestion to a living organism, e.g. human, rodent, or other small animal, a perfused organ, or tissue sample. The distribution of the probe is detected over a time course and represented by an image.

Effect of the Invention

A framework fragment of a chicken antibody according to the present invention, a heavy chain variable region or a light chain variable region including the framework fragment, or an antibody including the heavy chain variable region or the light chain variable region does not induce or prevents formation of disulfide bonds between antibody molecules while maintaining activity and reactivity of the antibody. The antibody introduced with cysteine or an antigen-binding fragment thereof easily binds with a conjugation compound such as a chemotherapeutic drug, an enzyme, an aptamer, a toxin, an affinity ligand, or a detection label, thereby being applied to various fields for diagnosis or treatment of mammalian cells or related diseases.

FIG. 1 a shows a sequential numbering scheme (top row) in comparison with the Kabat numbering scheme (bottom row) for base sequences of wild-type and germ-line of a chicken antibody used in the present experiment;

FIG. 1 b shows a cartoon depiction of Cys-modified antibody phage binding to immobilized PSA with binding of anti-phage HRP antibody for absorbance detection;

FIGS. 1 c and 1 d show binding measurements with detection of absorbance at 405 nm of Cys-modified antibody phages (upper: modified light chain, lower: modified heavy chain);

FIG. 1 e shows a three-dimensional representation of a chicken antibody fragment derived by X-ray crystal coordinates, in which the structure positions of 5 types of the engineered Cys residues of the heavy and light chains are shown;

FIG. 2 shows binding measurements with detection of absorbance at 405 nm of antibody phages including two cysteine residues having thiol reactivity;

FIGS. 3 a and 3 b show binding measurements with detection of absorbance at 405 nm of Cys-modified antibody phages with replaced with cationic amino acids (upper: modified light chain, lower: modified heavy chain);

FIGS. 3 c and 3 d show binding measurements with detection of absorbance at 405 nm of Cys-modified antibody phages with replacement of anionic amino acid (upper: modified light chain, lower: modified heavy chain);

FIG. 4 a shows coomassie blue staining of Cys-modified single chain Fv (scFv)-type antibodies expressed from cell culture for conjugation;

FIG. 4 b shows coomassie blue staining of cationic or anionic Cys-modified scFv-type antibodies expressed from cell culture for conjugation;

FIG. 5 a shows coomassie blue staining of Cys-modified full IgG-type antibodies expressed from cell culture for conjugation;

FIG. 5 b shows coomassie blue staining of cationic or anionic Cys-modified full IgG-type antibodies expressed from cell culture for conjugation;

FIG. 6 shows a cartoon depiction of conjugation of maleimide activated PEG to Cys-modified antibody;

FIG. 7 a shows coomassie blue staining of maleimide PEG-conjugated scFv;

FIG. 7 b shows iodine staining of maleimide PEG-conjugated scFv;

FIG. 7 c shows immunoblotting of maleimide PEG-conjugated scFv;

FIG. 8 a shows coomassie blue staining of maleimide PEG-conjugated full IgG;

FIG. 8 b shows iodine staining of maleimide PEG-conjugated full IgG;

FIG. 8 c shows immunoblotting of maleimide PEG-conjugated full IgG;

FIG. 9 a shows coomassie blue staining of maleimide PEG-conjugated scFv with replacement of cationic or anionic residue;

FIG. 9 b shows iodine staining of maleimide PEG-conjugated scFv with replacement of cationic or anionic residue;

FIG. 9 c shows immunoblotting of maleimide PEG-conjugated scFv with replacement of cationic or anionic residue;

FIG. 10 a shows coomassie blue staining of maleimide PEG-conjugated full IgG with replacement of cationic or anionic residue;

FIG. 10 b shows iodine staining of maleimide PEG-conjugated full IgG with replacement of cationic or anionic residue;

FIG. 10 c shows immunoblotting of maleimide PEG-conjugated full IgG with replacement of cationic or anionic residue;

FIG. 11 a shows a cartoon depiction of conjugation of GMBS-cotinine to Cys-modified antibody;

FIG. 11 b shows a cartoon depiction of GMBS-cotinine-conjugated, Cys-modified antibody binding to immobilized PSA with binding of anti-cotinine HRP antibody for absorbance detection;

FIG. 12 shows detection of absorbance at 450 nm of binding of GMBS-cotinine to C kappa -fused, Cys-modified scFv (upper: detection with anti-cotinine IgG-HRP, lower: detection with anti-C kappa IgG-HRP);

FIG. 13 a shows injection time of cotinine-Cys into mice and blood collection time; and

FIG. 13 b shows detection of absorbance at 450 nm to examine the presence or absence of cotinine-Cys-modified antibody in the serum before and after injection of cotinine-Cys-modified antibody into mice.

The present invention will be described in more detail with reference to specific Examples of the present invention. However, the present invention is not limited to the following Examples, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the scope and spirit of the present invention. Therefore, the appended claims should be interpreted broadly, as may be consistent with the spirit and scope of the present invention.