CN115947851B - Antibodies that bind CLDN18.2 and uses thereof - Google Patents

Abstract

The present invention relates to an antibody, antigen-binding fragment thereof, or variant thereof, that specifically binds CLDN18.2, comprising a heavy chain variable region and a light chain variable region, wherein: the heavy chain variable region comprises HCDR1 shown as SEQ ID NO.1, HCDR2 shown as SEQ ID NO.2 and HCDR3 shown as SEQ ID NO. 3; and the light chain variable region comprises LCDR1 as shown in SEQ ID NO.4, LCDR2 as shown in SEQ ID NO.5, and LCDR3 as shown in SEQ ID NO. 6. The present invention provides an antibody, a fully human monoclonal antibody that binds to claudin18.2 protein (e.g., human claudin18.2, murine claudin18.2, monkey claudin 18.2), which has higher ADCC activity, CDC activity and/or claudin18.2 protein binding stability and higher endocytic activity than prior art antibody molecules.

Description

Antibodies that bind CLDN18.2 and uses thereof

Technical Field

The present invention relates to the field of biological medicine, in particular to antibodies that bind CLDN18.2 and uses thereof.

Background

Tumors have been severely threatening the life health of humans. Targeted therapy may be specific for abnormal cells in a tumor. The targeted medicine is developed aiming at tumor abnormal molecules and genes, and takes abnormal tumor cells or genes as targets, so that the growth of the tumor cells is prevented and the tumor cells are killed, the normal cells are not accidentally injured by the targeted therapy, and the whole medicine effect is used on the tumor cells, so that the medicine effect is stronger than that of the conventional chemotherapy, and the side effect is much smaller than that of the conventional chemotherapy.

CLDN18.2 was expressed in primary pancreatic ductal adenocarcinoma, non-small cell lung carcinoma (NSCLC) patients, but not in the corresponding normal tissues; increased expression in advanced seal armon cell carcinoma (SRCC), barrett's esophagus, damaged squamous epithelium. In addition, CLDN18.2 expression is not limited to primary foci, but it is also highly expressed in metastases, possibly involved in proliferation and chemotaxis of malignant cells.

The medicine with CLDN18.2 targeting is obtained, and the requirement of various tumor treatments can be met.

Disclosure of Invention

In view of the technical problems existing in the prior art, the present invention proposes an antibody, an antigen-binding fragment thereof or a variant thereof that specifically binds CLDN18.2, comprising a heavy chain variable region and a light chain variable region, wherein: the heavy chain variable region comprises HCDR1 shown as SEQ ID NO.1, HCDR2 shown as SEQ ID NO.2 and HCDR3 shown as SEQ ID NO. 3; and the light chain variable region comprises LCDR1 as shown in SEQ ID NO.4, LCDR2 as shown in SEQ ID NO.5, and LCDR3 as shown in SEQ ID NO. 6.

In some embodiments, the heavy chain comprises the variable region shown in SEQ ID No. 7; and the light chain comprises the variable region shown in SEQ ID NO. 8.

In some embodiments, the antibody or antigen binding portion thereof is selected from the group consisting of: whole antibodies, bispecific antibodies, monoclonal antibodies, chimeric antibodies, humanized antibodies, and fully human antibodies.

In some embodiments, the above antibody, antigen-binding fragment thereof, or variant thereof, further comprises a heavy chain constant region and a light chain constant region, wherein: the antibody heavy chain constant region is selected from the group consisting of IgG series antibodies; the light chain constant region is selected from kappa or lambda chains.

In some embodiments, the IgG series antibody is selected from one or more of IgG1, igG2, and IgG 4.

In some embodiments, the antigen binding fragment is selected from the group consisting of: fab fragments, fab' fragments, F (ab) ₂ Fragments, fv fragments and ScFv.

In some embodiments, the CLDN18.2 is selected from the group consisting of: human CLDN18.2, mouse CLDN18.2 and monkey CLDN18.2.

A fusion protein comprising an antibody, antigen-binding fragment thereof, or variant thereof according to any one of the above.

One or more isolated nucleic acid molecules encoding an antibody, antigen-binding fragment thereof, or variant thereof, as defined in any one of the preceding claims, or a fusion protein as defined above.

One or more vectors comprising one or more isolated nucleic acid molecules as described above.

A cell comprising one or more isolated nucleic acid molecules as above or one or more vectors as above.

In some embodiments, the cell is further a CAR-T or CAR-NK cell comprising one or more isolated nucleic acid molecules as above or one or more vectors as above.

A method for producing an antibody, antigen-binding fragment thereof, or variant thereof, as described above, comprising culturing a cell, as described above, under conditions that enable expression of the antibody, antigen-binding fragment thereof, or variant thereof, as described above, or the fusion protein, as described above.

A composition comprising an antibody, antigen-binding fragment thereof or variant thereof, as defined in any one of the above, a fusion protein, as defined in any one of the above, one or more isolated nucleic acid molecules, as defined in any one of the above, one or more vectors and/or cells as defined in any one of the above, and optionally a pharmaceutically acceptable excipient.

Use of an antibody, antigen binding fragment or variant thereof according to any one of the above, a fusion protein according to the above, one or more isolated nucleic acid molecules according to the above, one or more vectors according to the above and/or a cell according to the above for the preparation of a medicament for the prevention and/or treatment of cancer or tumor.

Further, in some embodiments, the drug is a cell therapy drug.

In some embodiments, the cancer or tumor is a CLDN18.2 expression positive cancer or tumor.

Preferably, wherein the cancer or tumor is selected from bladder cancer, ovarian cancer, lung cancer, adenocarcinoma, gastric cancer, breast cancer, liver cancer, pancreatic cancer, skin cancer, malignant melanoma, head and neck cancer, sarcoma, cholangiocarcinoma, renal cancer, colon cancer, small intestine cancer, testicular embryonal carcinoma, placental choriocarcinoma, cervical cancer, testicular cancer, uterine cancer, esophageal cancer, and gallbladder cancer cells.

Use of an antibody, antigen-binding fragment thereof, or variant thereof, or fusion protein of any of the above, in the preparation of a reagent for determining the presence and/or amount of CLDN18.2 in a sample.

A pharmaceutical composition comprising: an antibody, antigen-binding fragment or variant thereof according to any one of the above, a fusion protein as above, one or more isolated nucleic acid molecules as above or one or more vectors as above and/or cells as above.

An antibody drug conjugate comprising the antibody, antigen-binding fragment thereof, or variant thereof of any one of the above covalently bound to a therapeutic agent.

In some embodiments, the therapeutic agent is a cytotoxic agent or a cell proliferation inhibitor selected from the group consisting of Auristatin (Auristatin), maytansine (DM 1), MMAE (Monomethy lauristatin E, monocrotaline Gui Yisu E), MMAF (Monomethy lauristatin F, monocrotaline Gui Si statin F), PDB, du Kamei, cytochalasin B, ponticin D, ethidium bromide, ipecac, mitomycin, etoposide, teniposide, vincristine, vinblastine, colchicine, doxorubicin, daunorubicin, dihydroxyanthrax (dihydroxy anthracin), maytansinoids (maytansinoids such as DM-1 and DM-4), diketones, mitoxantrone (mitoxantrone), mithramycin, actinomycin D, 1-dehydroketone, glucocorticoid, procaine, tetracaine, lidocaine, procaine, and procyanidins, and epothilones, and the like. The present invention provides an antibody, a fully human monoclonal antibody that binds to claudin18.2 (e.g., human claudin18.2, murine claudin18.2, monkey claudin 18.2), which has higher ADCC activity, CDC activity and/or claudin18.2 binding stability and higher endocytic activity than prior art antibody molecules.

Drawings

Preferred embodiments of the present invention will be described in further detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a human-derived CLDN18.2 and CLDN18.1 specific assay according to one embodiment of the invention; wherein the abscissa is the fluorescence intensity of Anti-hIgG-Fc-AF647, and the binding intensity of the antibody and the CLDN18.1 and the CLDN18.2 is detected; the ordinate SSC-H is the deflection dispersion of the cells, and the complexity of the cells is detected; p1026 is a screened CLDN18.2 specific binding antibody; NC (Negative control) is a negative control, specific antibodies are Human IgG1, kappa Isotype control, brand: crownBio cat: c0001-4, lot AB190016, is a negative control antibody that does not bind to CLDN18.1 and CLDN 18.2; IMAB362 is a positive control, specifically binding to human CLDN18.2, clone according to patent CN101312989a for IMAB362 antibody: 175D10 (heavychain: SEQ ID NO:103;Light Chain:SEQ ID NO:110), light and Heavy Chain sequences were synthesized separately by ExpiCHO ^TM Expression system, transient expression prepares IMAB362 as a positive control antibody that does not bind to CLDN18.1 but binds to CLDN 18.2;

FIG. 2 is an antibody species crossover result test according to one embodiment of the invention, wherein the abscissa is the fluorescence intensity of Anti-hIgG-Fc-AF647, and the binding intensity of the test antibody to CLDN 18.2; the ordinate SSC-H is the deflection dispersion of the cells, and the complexity of the cells is detected; p1026 is a screened CLDN18.2 specific binding antibody; NC (Negative control) is a negative control, specific antibodies are Human IgG1, kappa Isotype control, brand: crownBio cat: c0001-4, lot AB190016, is a negative control antibody that does not bind to CLDN 18.2; IMAB362 is a positive control, specifically binding to human CLDN18.2, clone according to patent CN101312989a for IMAB362 antibody: 175D10 (heavychain: SEQ ID NO:103;Light Chain:SEQ ID NO:110), light and Heavy Chain sequences were synthesized separately by ExpiCHO ^TM Expression system, transient expression prepares IMAB362 as a positive control antibody that does not bind to CLDN18.1 but binds to CLDN 18.2;

FIG. 3 is an antibody binding capacity assay according to one embodiment of the invention; wherein the abscissa is the antibody concentration and the ordinate is the average fluorescence intensity;

FIG. 4 is ADCC activity of a CLDN18.2 antibody on MC38 cells overexpressing human claudin18.2 according to one embodiment of the invention;

FIG. 5 is CDC activity of a CLDN18.2 antibody on MC38 cells overexpressing human claudin18.2 according to one embodiment of the invention; and

fig. 6 is endocytic activity of CLDN18.2 antibody according to an embodiment of the invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the application may be practiced. In the drawings, like reference numerals describe substantially similar components throughout the different views. Various specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to practice the teachings of the present application. It is to be understood that other embodiments may be utilized or structural, logical, or electrical changes may be made to the embodiments of the present application.

Antibody therapy has been approved worldwide for the treatment of a variety of cancers, and significantly improves patient prognosis, increasing patient overall survival. A variety of antibody molecules can specifically bind to tumor surface antigens, and antibodies elicit antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) via Fc fragments, ultimately leading to tumor cell death.

As used herein, the term "antibody" generally refers to an immunoglobulin molecule that consists of two pairs of identical polypeptide chains, each pair of polypeptide chains having one "light" (L) chain and one "heavy" (H) chain. The light chains of antibodies can be divided into kappa and lambda light chains. Heavy chains can be classified as μ, δ, γ, α or ε, and isotypes of antibodies are defined as IgM, igD, igG, igA and IgE, respectively. Within the light and heavy chains, the variable and constant regions are joined by a "J" region of about 12 or more amino acids, and the heavy chain also includes a "D" region of about 3 or more amino acids. Each heavy chain consists of a heavy chain variable region (V _H ) And a heavy chain constant region (C) _H ) Composition is prepared. The heavy chain constant region consists of three domains (CH 1, CH2 and CH 3). Each light chain consists of a light chain variable region (V _L ) And a light chain constant region (C _L ) Composition is prepared. The light chain constant region consists of one domain C _L Composition is prepared. The constant region of an antibody may mediate the binding of an immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component of the classical complement system (Clq). V (V) _H And V _L Regions can also be subdivided into regions of high variability termed Complementarity Determining Regions (CDRs) interspersed between regions that are more conserved termed Framework Regions (FR). Each V _H And V _L From N end to C end as followsThe ordered arrangement consists of 3 CDRs and 4 FRs: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable region (V _H And V _L ) The antibody binding sites are formed separately. The distribution of amino acids into regions or domains follows the Kabat sequence (Kabat Sequences of Proteins of Immunological Interest) (National Institutes of Healt h, bethesda, md. (1987 and 1991)) or Chothia of immunologically relevant proteins&Lesk (1987) J.mol.biol.196:901-917; chothia et al (1989) Nature 342:878-883.

The present antibodies are not limited by any antibody production method. For example, it includes recombinant antibodies, monoclonal antibodies and polyclonal antibodies. The antibodies may be of different types, for example, igG (e.g., igG 1, igG2, igG3, or IgG4 subclasses), igAl, igA2, igD, igE, or IgM antibodies.

As used herein, the term "antigen-binding fragment" generally refers to one or more fragments of a full-length antibody that retain the ability to bind to the same antigen (e.g., CLDN 18.2) to which the antibody binds and compete for antigen-specific binding with the intact antibody. Antigen binding fragments may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. In some cases, the antigen binding site includes Fab, fab ', F (ab') ₂ 、F(ab) ₂ Fd, fv, dAb and Complementarity Determining Region (CDR) fragments, single chain antibodies (e.g., scFv), chimeric antibodies, diabodies, and polypeptides comprising at least a portion of an antibody sufficient to confer specific antigen binding capacity to the polypeptide.

In some embodiments, the antibody or antigen binding fragment comprises an amino acid sequence having one or more modification groups. For example, an antibody or antigen binding fragment of the present disclosure may comprise a malleable linker sequence, or may be modified to add a functional group (e.g., PEG, drug, toxin, or tag).

Antibodies, antigen-binding fragments, disclosed herein include modified derivatives, i.e., modified by covalent attachment of any type of molecule to the antibody or antigen-binding fragment, wherein the covalent attachment does not prevent the antibody or antigen-binding fragment from binding to an epitope. Including but not limited to the following examples, the antibodies or antigen binding fragments may be glycosylated, acetylated, pegylated, phosphorylated, amidated, derivatized with known protecting/blocking groups, proteolytically cleaved, linked to cell ligands or other proteins, and the like. Any of a number of chemical modifications may be made by the prior art, including but not limited to specific chemical cleavage, acetylation, formylation, metabolic synthesis of tunicamycin, and the like.

In some embodiments, the antibody or antigen binding fragment may be conjugated to a therapeutic agent, prodrug, peptide, protein, enzyme, virus, lipid, biological response modifier, pharmaceutical agent, or PEG.

The antibody or antigen binding fragment may be detectably labeled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-tagged antibody or antigen binding fragment is then determined by detecting the luminescence that occurs during the chemical reaction. Examples of chemiluminescent labeling compounds include luminol, isoluminol, aromatic acridinium esters, imidazoles, acridinium salts and oxalic esters.

As used herein, the term "whole antibody" refers to an antibody having the full length sequence of the antibody. In some embodiments, the whole antibody may be a chimeric, humanized or fully human antibody. In other embodiments, the whole antibody may be a monoclonal antibody or a polyclonal antibody. In one embodiment, the whole antibody is an immunogenic fragment that binds to the claudin18.2 antigen. Further, the whole antibody is a CLDN18.2 antibody comprising the full length sequence of the CLDN18.2 antibody.

As used herein, the term "monoclonal antibody" generally refers to an antibody produced by the same immune cell, which is a clone of a unique parent cell. Monoclonal antibodies can have monovalent affinity because they bind to the same epitope (the portion of the antigen recognized by the antibody). It has become an important tool in biochemistry, molecular biology and medicine. A variety of monoclonal antibody techniques have been developed in recent years, such as phage display, single B cell culture, single cell expansion from various B cell populations, and single plasma cell interrogation techniques (single plasma cell interrogation technologies). The present application provides an isolated monoclonal antibody, e.g., a fully human monoclonal antibody that binds to claudin18.2 (human claudin18.2, murine claudin18.2, monkey claudin 18.2), which has higher ADCC activity, CDC activity and/or claudin18.2 binding stability compared to existing anti-CLDN 18.2 antibody molecules.

As used herein, different portions of a "chimeric antibody" are derived from different animal species, such as those antibodies having variable regions derived from murine antibodies and human immunoglobulin constant regions. Chimerisation of antibodies is achieved by linking the variable regions of murine heavy and light chains with the constant regions of human heavy and light chains (e.g., by Kraus et al

Methods in Molecular Biology series, recombinant antibodies for cancer therapy ISB N-O89603-918-8).

As used herein, "CAR-T" refers to: the CAR-T therapy is chimeric antigen receptor T cell immunotherapy, is a novel accurate targeting therapy for treating tumors, has good effect on clinical tumor treatment, and is a novel tumor immunotherapy method which can accurately, rapidly and efficiently cure cancers.

As used herein, "CAR-NK" or "CAR-NK cell" refers to CAR-NK cell therapy, CAR-NK cells, consisting of an extracellular signal domain, a transmembrane region, and an intracellular domain that recognize a tumor-specific antigen, which can establish a new activation pathway to enhance lysis of target cells. CAR-NK cells express tumors by CAR-specific recognition of antigen, while eliminating tumors by NK cell receptors themselves. Wherein the CAR is a chimeric antigen receptor, the NK cells are natural killer cells, and are immune cells that are large granule lymphocytes different from T, B lymphocytes. The activity of NK cells depends on the balance of stimulation and inhibition signals, not antigen specificity.

As used herein, "humanized" refers to: antibodies interact with target antigens primarily through amino acid residues located in the six heavy and light chain Complementarity Determining Regions (CDRs). For this reason, the amino acid sequence inside the CDRs between the respective antibodies is more diverse than the sequence outside the CDRs. Because CDR sequences are responsible for most antibody-antigen interactions, it is possible to express recombinant antibodies that mimic the properties of specific naturally occurring antibodies by constructing expression vectors that include CDR sequences grafted to specific naturally occurring antibodies from framework sequences of different antibodies having different properties (see, e.g., riechmann, L. Et al (1998) Nature 332:323-327; jones, P. Et al (1986) Nature321:522-525 and Queen, C. Et al (1989) Proc. Natl. Acad. Sci. U.S.A.86:10029-10033). Such framework sequences may be obtained from public DNA databases including germline antibody gene sequences. These germline sequences will differ from the mature antibody gene sequences in that they do not include fully assembled variable genes, which are formed by V (D) J ligation during B cell maturation.

The "fully human" or "fully human" refers to the process of transferring the human antibody gene to the genetically engineered antibody gene-deleted animal by transgenic or transchromosomal technology, so that the animal expresses the human antibody and the aim of fully humanizing the antibody is achieved. Generally refers to antibodies having fully human amino acid sequence derived antibody region therapeutics, wherein antigen specificity has been selected in vivo by using genetically modified mice or by antibody engineering methods of binding screening. The fully human antibodies have lower risk of inducing immune responses in humans and have a stronger specific immune effect than humanized antibodies, higher ADCC activity, CDC activity and/or claudin18.2 binding stability.

As used herein, the term "bispecific antibody" generally refers to an artificial protein capable of binding to two different types of antigens simultaneously. The main types of manufacturing methods are quadromas (quadromas), chemical conjugation and gene recombination. The IgG-like format retains the conventional monoclonal antibody (mAb) structure of two Fab arms and one Fc region, except that the two Fab sites bind to different antigens. Each heavy and light chain pair is from a unique mAb. The Fc region made from two heavy chains forms the third binding site. non-IgG-like forms include chemically linked Fab, consisting only of Fab regions, and various types of divalent and trivalent single chain variable fragments (scFvs). There are also fusion proteins that mimic the variable domains of two antibodies. Bispecific antibodies have higher cytotoxic potential and bind to antigens that are expressed relatively poorly at lower effective doses. In addition, targeting more than one molecule can be used to circumvent modulation of parallel pathways and avoid resistance to treatment.

Bispecific antibodies include cross-linked or "heteroconjugate" antibodies. For example, one of the antibodies in the heteroconjugate may be conjugated to avidin, while the other antibody is conjugated to biotin. Any convenient cross-linking method may also be used to generate the heteroconjugate antibodies. Suitable crosslinking agents and techniques are well known in the art and are disclosed in U.S. Pat. No. 4,676,980, which is incorporated herein by reference in its entirety.

As used herein, the term "Fab fragment" generally refers to a portion of an immunoglobulin molecule (such as an antigen binding fragment). Fab fragments may comprise a portion of one light chain and heavy chain, with a single antigen binding site. Fab fragments can be obtained by papain digestion of immunoglobulin molecules. For example, a Fab fragment may consist of one constant domain and one variable domain for each heavy and light chain. The variable domain may contain a paratope (antigen binding site) comprising a set of complementarity determining regions at the amino terminus of the immunoglobulin molecule. Papain can be used to cleave immunoglobulin molecules into two Fab fragments and one Fc fragment. Pepsin cleaves below the hinge region, forming a F (ab') ₂ Fragments and a pFC' fragment. Bivalent F (ab) ₂ Or F (ab') ₂ The fragment has two antigen binding regions linked by disulfide bonds. F (ab) ₂ Or F (ab') ₂ Reduction of the fragment yields 2 monovalent Fab or Fab' fragments with free sulfhydryl groups available for conjugation to other molecules.

The term "Fv fragment" as used herein generally refers to the smallest fragment that can be made by enzymatic cleavage of antibodies of the IgG and IgM classes. Fv fragments have antigen binding sites made up of the VH and VL regions, but they lack the CH1 and CL regions. The VH and VL chains are held together in the Fv fragment by non-covalent interactions.

As used herein, the term "ScFv" generally refers to a single chain antibody fragment. ScFv may refer to a recombinant single chain polypeptide molecule in which the light and heavy chain variable regions of an antibody are linked by a peptide linker. Single chain antibodies (ScFv) typically do not include portions of the Fc region of the antibody that are involved in effector function and are therefore naked antibodies, although methods are known to add such regions to known ScFv molecules, if desired. See Helfrich et al A rapid and versatile method for harnessing ScFv antibody fragments with various bi ological functions J Immunol Methods 237:131-145 (2000) and de Haard et al Creating and engineering human antibodies for immunology advanced Drug Deli very Reviews 31:5-31 (1998).

As used herein, the term "IgG" generally refers to an antibody of one subtype. Each IgG has two antigen binding sites. Representing approximately 75% of human serum antibodies, igG is the most common type of antibody found in the circulation. Recognized immunoglobulin genes include kappa, lambda, alpha, gamma (IgG 1, igG2, igG3, igG 4).

The teachings herein given with respect to a particular amino acid sequence (such as those shown in the sequence listing) should be understood to also refer to variants of the particular sequence, resulting in a sequence that is functionally equivalent to the particular sequence, such as an amino acid sequence that exhibits properties that are equivalent or similar to those of the particular amino acid sequence. One important property is to retain the binding of an antibody to its target or to retain the effector function of an antibody. Preferably, when a sequence that is variant relative to a particular sequence replaces a particular sequence in an antibody, the sequence retains the binding of the antibody to CLDN18.2, and preferably retains the function of the antibody as described herein, such as CDC-mediated cleavage or ADCC-mediated cleavage.

Those skilled in the art will appreciate that sequences, particularly CDRs, hypervariable regions, and variable regions, can be modified without losing the ability to bind CLDN 18.2. For example, the CDR regions are identical or highly homologous to the antibody regions specified herein. It is contemplated that a "highly homologous" is that 1 to 5, preferably 1 to 4, such as 1 to 3 or 1 or 2 substitutions can be made in the CDRs. In addition, the hypervariable and variable regions may be modified such that they exhibit substantial homology with the antibody regions explicitly disclosed herein. As used herein, a CDR may be a CDR region of a heavy chain variable region, or may be a CDR region of a light chain region. Further, CDR regions may refer to CDR1, CDR2, and/or CDR3 of the heavy and/or light chain. Further, HCDR refers to complementarity determining regions of the heavy chain variable region, specifically including HCDR1, HCDR2 and HCDR3; LCDR refers to the complementarity determining regions of the light chain variable region, and specifically includes LCDR1, LCDR2 and LCDR3.

As used herein, the term "variant" generally refers to a protein that differs from the parent molecule by at least one amino acid. A variant may refer to the molecule itself, a composition comprising the molecule. When such a molecule is a polypeptide or a protein, it may also refer to the amino acid sequence of the molecule. In some cases, a variant differs from its parent molecule (e.g., protein) by the addition, deletion, or substitution of one or more amino acids, such as 1-50, 1-40, 1-30, 1-20, 1-15, 1-14, 1-13, 1-12, 1-11, 1-10, 1-9, 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, or 1-2 amino acids. In some cases, a variant may have at least about 80% (e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or more) sequence homology to the amino acid sequence of its parent molecule.

In some embodiments, an antibody or antigen binding fragment described herein can be conjugated to a therapeutic agent. An antibody drug conjugate comprising an antibody or antigen binding fragment thereof may be covalently or non-covalently bound to a therapeutic agent. In certain embodiments, the therapeutic agent is a cytotoxic agent or a cytostatic agent. For example, the therapeutic agent may be Auristatin (Auristatin), maytansine (DM 1), MMAE (Monomethy lauristatin E, monomethylmonth Gui Yisu E), MMAF (Monomethy lauristatin F, monomethylmonth Gui Si Tatin F), PDB, du Kamei, cytochalasin B, ponin D, ethidium bromide, ipecacine, mitomycin, etoposide (etoposide), teniposide (tenoposide), vincristine, vinblastine, colchicine, doxorubicin, daunorubicin (daunorubicin), dihydroxyanthrax (dihydroxy anthracin), maytansinoids (maytansinoids such as DM-1 and DM-4), diketones, mitoxantrone (mitoxantrone), mithramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoid, procaine, tetracaine, lidocaine, promethazine, procyanine, and epothilone, and the like.

"sequence similarity" indicates the percentage of amino acids that are identical or that represent conservative amino acid substitutions. "sequence identity" between two amino acid sequences indicates the percentage of identical amino acids between the sequences.

As used herein, the term "binding specificity" generally refers to the ability of one substance to specifically bind to another substance, and not readily bind randomly to any other substance. For example, one protein may bind specifically to another protein due to its specific structure. For example, the targeting moiety may exhibit binding specificity for a corresponding tumor antigen.

As used herein, the term "claudin18.2" is interchangeable with "CLDN18.2", the claudin18.2 protein contains 4 transmembrane domains, 2 extracellular loops, is available for monoclonal antibody binding, and claudin18.2 antibodies have been used in research to treat cancer. For example, claudiximab (IMAB 362), a human murine chimeric antibody developed by astella, exhibited positive data in clinical trials for the treatment of gastric and gastroesophageal junction cancers. Claudin18.2 is abundantly present in a large proportion of primary gastric cancers and their metastatic cancers and plays an important role in their malignant transformation. For example, frequent ectopic activation of Claudin18.2 is found in pancreatic, esophageal, ovarian and lung tumors ((Niimi et al., (2001) Mol Cell Biol 21 (21): 7380-7390;Tanaka et al. (2011) J Histochem Cytochem (10): 942-952; mick et al., (2014) Int J Cancer 135 (9): 2206-2214;Shimobaba et al. (2016) Biochim Biophys Acta (6 Pt a): 1170-1178; singh et al., (2017) J heat Oncol 10 (1): 105;Tokumitsu et al., (2017) cytovirology 28 (2): 116-121): a variety of cancers or tumors such as bladder Cancer, ovarian Cancer, lung Cancer, adenocarcinoma, stomach Cancer, breast Cancer, liver Cancer, pancreatic Cancer, skin Cancer, malignant melanoma, head and neck Cancer, sarcoma, cholangiocarcinoma, kidney Cancer, colon Cancer, small intestine Cancer, testicular Cancer, choriocarcinoma, esophageal Cancer, gall bladder Cancer, cl2, positive Cell expression of dn 18.18.

As used herein, the terms "claudin18.2 antibody", "CLDN18.2 antibody", "anti-claudin 18.2 antibody" and "anti-CLDN 18.2 antibody" are interchangeable. In some embodiments, the antibodies of the invention, or antigen binding fragments thereof, are capable of specifically binding to CLDN18.2 (claudin 18.2). In some embodiments, the antibody or antigen binding fragment thereof is a murine antibody, a chimeric antibody, a humanized antibody, or a fully human antibody. In some embodiments, the antibodies or antigen binding fragments thereof of the invention have the following properties: a) Specifically binds to CLDN 18.2; b) High affinity; c) Strong ADCC activity; d) Strong CDC activity. In some embodiments, an anti-CLDN 18.2 antibody can impair growth of tumor or cancer cells positive for CLDN18.2 expression. Since Claudin18.2 is present in large amounts in a large proportion of primary gastric cancers and their metastatic cancers, it plays an important role in its malignant transformation. anti-CLDN 18.2 antibodies can damage, for example, tumors in the pancreas, esophagus, ovary, and lung. Further, in some embodiments, the anti-CLDN 18.2 antibodies may also have therapeutic effects against other cancers or tumors including, but not limited to, bladder cancer, ovarian cancer, lung cancer, adenocarcinoma, gastric cancer, breast cancer, liver cancer, pancreatic cancer, skin cancer, malignant melanoma, head and neck cancer, sarcoma, cholangiocarcinoma, renal cancer, colon cancer, small intestine cancer, testicular embryonal cancer, placental choriocarcinoma, cervical cancer, testicular cancer, uterine cancer, esophageal cancer, and gallbladder carcinoma cells.

In some embodiments, the antibody capable of binding CLDN18.2 preferably comprises a heavy chain variable region (V) of a monoclonal antibody against CLDN18.2, preferably a monoclonal antibody against CLDN18.2 as described herein _H ) Such as HCDR1, HCDR2 and HCDR3 regions, and preferably comprises a light chain variable region (V _L ) Such as the LCDR1, LCDR2 and LCDR3 regions. In one embodiment, the one or more Complementarity Determining Regions (CDRs) are selected from the group of Complementarity Determining Regions (CDRs) described hereinThe regions CDR1, CDR2 and CDR3. In a particularly preferred embodiment, the antibody capable of binding CLDN18.2 preferably comprises the heavy chain variable region (V _H ) And/or light chain variable region (V _L ) CDRL, CDR2 and CDR3, and preferably comprises the heavy chain variable region (V _H ) And/or light chain variable region (V _L ) CDR1, CDR2 and CDR3.

In one embodiment, the heavy chain variable region (V _H ) The amino acid sequence of the complementarity determining region HCDRl is shown as SEQ ID NO.1, the amino acid sequence of HCDR2 is shown as SEQ ID NO.2, and the amino acid sequence of HCDR3 is shown as SEQ ID NO. 3. Wherein SEQ ID NO.1 is NYEMN; SEQ ID NO.2 is YITGSGRTIYYADSVKG; SEQ ID NO.3 is YYYGDDF.

In one embodiment, the light chain variable region (V _L ) The amino acid sequence of the complementarity determining region LCDRl is shown as SEQ ID NO.4, the amino acid sequence of LCDR2 is shown as SEQ ID NO.5, and the amino acid sequence of LCDR3 is shown as SEQ ID NO. 6. Wherein SEQ ID NO.4 is RASQGISSWLA; SEQ ID No.5 is AASSLQS; SEQ ID NO.6 is QQANSFPLT.

In one embodiment, an antibody comprising one or more CDRs as described herein, a set of CDRs or a combination of sets of CDRs comprises the CDRs with a framework region interposed therebetween.

In one embodiment, an antibody comprising one or more CDRs, a set of CDRs, or a combination of sets of CDRs as described herein comprises the CDRs in a human antibody framework.

In one embodiment, the heavy chain variable region (V _H ) The amino acid sequence of (a) is shown as SEQ ID NO.7, and is capable of binding to the light chain variable region (V _L ) The amino acid sequence of (C) is shown as SEQ ID NO. 8. Wherein SEQ ID NO.7 is QVQLVESGGGLVQPGGSLRLSCAASGFTFSNYEMNWVRQAPGKGLEWVAYITGSGRTIYYADSVKGRFTISRDNAKKSLYLQMNSLRSEDTAVYYCAIYDYGDFDFWGQGTLVTVSS; SEQ ID NO.8 is DIQMTQSPSSVSASVGDRVTITCRASQGISSWLAWYQQKPGKAPKLLIYAASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQANSFPLTFGGGTKVEIK.

The reference herein to an antibody comprising a specific chain, or a specific region or sequence, relative to its heavy chain preferably relates to the case in which all heavy chains of the antibody comprise said specific chain, region or sequence. This applies correspondingly to the light chain of the antibody.

As used herein, the term "nucleic acid" or "nucleotide" is intended to include DNA and RNA. The nucleic acid may be single-stranded or double-stranded, but is preferably double-stranded DNA.

According to the invention, the term "expression" is used in its most general sense and includes the production of RNA or RNA and proteins/peptides. It also includes partial expression of nucleic acids. Furthermore, expression can be performed transiently or stably.

The term "transgenic animal" refers to an animal having a genome comprising one or more transgenes, preferably heavy and/or light chain transgenes, or transgenes (integrated or not integrated into the animal's native genomic DNA), and preferably capable of expressing the transgenes. For example, a transgenic mouse may have a human light chain transgene and a human heavy chain transgene or a human heavy chain transchromosome such that when immunized with CLDN18.2 antigen and/or cells expressing CLDN18.2, the mouse produces a human anti-CLDN 18.2 antibody. The human heavy chain transgene may be integrated into the chromosomal DNA of the mouse, as in the case of transgenic mice, such as HuMAb mice, such as HCo7 or HCol2 mice, or the human heavy chain transgene may be maintained extrachromosomally, as in the case of transchromosomal (e.g., KM) mice described in WO 02/43478. Such transgenic and transchromosomal mice are capable of producing multiple isotypes (e.g., igG, igA, and/or IgE) of the human monoclonal antibody to CLDN18.2 by undergoing V-D-J recombination and isotype switching.

As used herein, the term "substantially free" generally means little or no binding of a particular substance. For example, very little or no (e.g., less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, less than 0.1%, or less than 0.01%) of an antibody, antigen-binding fragment thereof, or variant thereof according to the present application binds CLDN 18.1.

As used herein, "reduce", "decrease" or "inhibit" means an overall decrease in or capable of causing an overall decrease in a level (e.g., expression level or cell proliferation level), preferably 5% or more, 10% or more, 20% or more, more preferably 50% or more, and most preferably 75% or more.

Terms such as "increasing" or "enhancing" preferably relate to increasing or enhancing by about at least 10%, preferably at least 20%, preferably at least 30%, more preferably at least 40%, more preferably at least 50%, even more preferably at least 80% and most preferably at least 100%, at least 200%, at least 500%, at least 1000%, at least 10000% or even more.

While the following provides considerations regarding the underlying mechanism of therapeutic efficacy of the antibodies of the invention, they should not be construed as limiting the invention in any way.

The antibodies described herein preferably interact with components of the immune system, preferably by ADCC or CDC. The antibodies described herein can also be used to target payloads (e.g., radioisotopes, drugs, or toxins) to directly kill tumor cells or can be used in conjunction with conventional biological or chemotherapeutic agents to attack tumors by complementary mechanisms of action, which may include anti-tumor immune responses that may have been compromised due to cytotoxic side effects of the chemotherapeutic agents on T lymphocytes. However, the antibodies described herein may also function only by binding to CLDN18.2 on the cell surface, thereby blocking cell proliferation, for example.

As used herein, "ADCC", "Antibody-Dependent Cell-mediated cytotoxicity" refers to an Antibody-Dependent Cell-mediated Cytotoxicity, which describes the Cell killing capacity of effector cells, which preferably require target cells labeled with antibodies. ADCC, i.e. ADCC mediated direct killing of immune effector cells against target cells, preferably occurs when the Fab fragment of the antibody binds to an epitope on a tumor cell and the Fc domain of the antibody binds to an Fc receptor (FcR) on the surface of an immune effector cell, such as NK cells, macrophages, neutrophils, etc.

Several families of Fc receptors have been identified, and specific cell populations characteristically express defined Fc receptors. ADCC can be considered as a mechanism that directly induces a variable degree of immediate tumor destruction that leads to antigen presentation and induces tumor-directed T-cell responses. Preferably, in vivo induction of ADCC will result in a tumor-directed T-cell response and a host-derived antibody response.

The terms "CDC" and "complement dependent cytotoxicity" as used herein refer to Complement Dependent Cytotoxicity, another cell killing method that can be directed by antibodies, and are cytotoxic actions involving complement, i.e., activation of the classical pathway of complement by binding specific antibodies to the corresponding antigen on the surface of the cell membrane to form a complex, and the thus formed tapping membrane complex exerts a lytic effect on the target cells.

IgM is the most potent isotype for complement activation. Both IgG1 and IgG3 are also very effective in targeting CDC via the classical complement-activation pathway. Preferably, in this cascade, the formation of antigen-antibody complexes results in the disclosure of multiple C1q binding sites (C1 q is one of the three subcomponents of complement C1) in close proximity to the CH2 domain of an antibody molecule, such as an IgG molecule. Preferably, these disclosed C1q binding sites convert the previously low affinity C1q-IgG interactions to one of the high affinities, which triggers a cascade involving a range of other complement protein events and results in proteolytic release of effector-cell chemokines/activators C3a and C5 a. Preferably, the complement cascade terminates upon formation of a membrane attack complex, which creates a pore in the cell membrane that facilitates free entry and egress of water and solutes into and out of the cell.

In this application, antibodies can be produced by a variety of techniques, including conventional monoclonal antibody methodologies, such as the standard somatic hybridization techniques of Kohler and Milstein (Nature 256:495, 1975). Although somatic hybridization procedures are preferred, in principle, other techniques for producing monoclonal antibodies may be employed, such as oncogenic transformation of viruses or B-lymphocytes or phage display techniques using antibody gene libraries.

The preferred animal system for producing hybridomas secreting monoclonal antibodies is a murine system, more preferably a mouse system. Immunization protocols and techniques for isolating immune cells for fusion are known in the art.

Other preferred animal systems for producing monoclonal antibody secreting hybridomas are the rat and rabbit systems (as described, for example, in Spieker-Polet et al, proc. Natl. Acad. Sci. U.S. A.92:9348 (1995), see also Rossi et al, am. J. Clin. Pathol.124:295 (2005)).

In another preferred embodiment, human monoclonal antibodies may be generated using transgenic or transchromosomal mice carrying a portion of the human immune system rather than the mouse system. These transgenic and transchromosomal mice include mice referred to as HuMAb mice and KM mice, respectively, and are collectively referred to herein as "transgenic mice". The production of human antibodies in such transgenic mice can be performed as described in detail for CD20 in WO 2004035607.

However, another strategy for generating monoclonal antibodies involves the direct isolation of the genes encoding the antibodies from lymphocytes producing defined specific antibodies, as described in Babcock et al (1996;A novel strategy for generating monoclonal antibodies from single,isolated lymphocytes producing antibodies of defined specificities). Details of recombinant antibody engineering can also be found in Welschof and Kraus (Recombinant antibodes for cancer therapy ISBN-0-89603-9l 8-8) and Benny K.C. Lo Antibody Engineering ISBN-58829-092-1.

To generate antibodies, as described above, mice can be immunized with a concentrated preparation of vector-conjugated peptides derived from the antigen sequence (i.e., the sequence directed against the antibody to be directed), recombinantly expressed antigen or fragments thereof, and/or cells expressing the antigen. Alternatively, the mice may be immunized with DNA encoding an antigen or fragment thereof. Where immunization with purified or concentrated antigen preparations does not produce antibodies, the cells expressing the antigen (e.g., cell lines) may also be used to immunize mice to promote an immune response.

To generate hybridomas that produce monoclonal antibodies, spleen cells and lymph node cells can be isolated from the immunized mice and fused to a suitable immortalized cell line, such as a mouse myeloma cell line. The resulting hybridomas can then be screened for the production of antigen-specific antibodies. Individual wells can then be screened for antibody secreting hybridomas by ELISA. Antibodies specific for the antigen can be identified by immunofluorescence and FACS analysis using cells expressing the antigen. Hybridomas secreting antibodies can be re-inoculated, re-screened, and subcloned by limiting dilution if monoclonal antibodies are still positive. The stable subclones can then be cultured in vitro to generate antibodies for characterization in tissue culture medium.

Antibodies can also be produced in host cell transfectomas using, for example, a combination of recombinant DNA techniques and gene transfection methods as are well known in the art (Morrison, s. (1985) Science 229:1202).

For example, in one embodiment, a gene of interest (e.g., an antibody gene) can be linked to an expression vector, such as a eukaryotic expression plasmid as used in the GS gene expression systems disclosed in WO 87/04462, WO 89/01036 and EP 338 841, or other expression systems well known in the art. Purified plasmids with cloned antibody genes may be introduced into eukaryotic host cells, such as CHO cells, NS/0 cells, HEK293T cells or HEK293 cells, or other eukaryotic cells, such as cells of plant origin, fungal cells or yeast cells. Methods for introducing these genes may be methods described in the art, such as electroporation, liposomes (lipofectamine) or other methods. After introduction of these antibody genes into host cells, cells expressing the antibodies can be identified and selected. These cells represent transfectomas, which can then be expanded in expression levels and scaled up to produce antibodies. Recombinant antibodies can be isolated and purified from these culture supernatants and/or cells.

Alternatively, the cloned antibody genes may be expressed in other expression systems, including prokaryotic cells, such as microorganisms, e.g., E.coli. Furthermore, antibodies can be produced in transgenic non-human animals (such as sheep and rabbit milk or hen eggs) or in transgenic plants; see, e.g., verma, r., etc

(1998) J.Immunol. Meth.216:165-181; pollock, et al

(1999) J.Immunol. Meth.231:147-157; and Fischer, r., etc.

(1999)Biol.Chem.380:825-839。

As used herein, the term "one or more isolated nucleic acid molecules" generally refers to polymeric forms of nucleotides (whether deoxyribonucleotides or ribonucleotides or analogs thereof) of any length, either isolated from the natural environment or synthesized.

As used herein, the term "fusion protein" may generally refer to an amino acid sequence of a polypeptide comprising or consisting of an amino acid sequence of a polypeptide fused directly or indirectly (e.g., via a linker) to an amino acid sequence of a heterologous polypeptide (i.e., a polypeptide unrelated to a previous polypeptide or domain thereof).

As used herein, the term "vector or vectors" generally refers to a nucleic acid vector into which a polynucleotide encoding a protein can be inserted and expressed. The genetic material elements carried in the vector may be expressed in a host cell by transforming, transducing or transfecting the host cell with the vector. Embodiments of the vector include plasmids; phagemid; a cosmid; artificial chromosomes, such as Yeast Artificial Chromosomes (YACs), bacterial Artificial Chromosomes (BACs), or P1-derived artificial chromosomes (PACs); phages such as lambda phage or M13 phage and animal viruses. Animal viruses used as vectors include retroviruses (including lentiviruses), adenoviruses, adeno-associated viruses, herpesviruses (such as herpes simplex virus), oncolytic viruses, jaundice viruses, baculoviruses, papilloma viruses, papovaviruses (such as SV40 virus). The vector may contain a variety of elements that control expression, including promoter sequences, transcription initiation sequences, enhancer sequences, selection elements, and reporter genes. In addition, the vector may also comprise an origin of replication. The vector may also include components that facilitate its entry into the cell, such as viral particles, liposomes, or protein shells, but not just these. In some embodiments, the antibodies of the invention, or antigen-binding portions thereof, may also be encoded by or carried by an oncolytic virus.

Standard binding assays (e.g., ELISA, western blots, immunofluorescence, and flow cytometry assays) can be used to determine the ability of an antibody to bind an antigen.

To purify antibodies, selected hybridomas can be grown in spinner flasks for monoclonal antibody purification. Alternatively, antibodies may be produced in dialysis-based bioreactors. The supernatant may be filtered and, if desired, concentrated prior to affinity chromatography with protein G-agarose or protein A-agarose. Eluted IgG can be detected by gel electrophoresis and high performance liquid chromatography to ensure purity. The buffer can be replaced with PBS and the OD can be used with an extinction coefficient of 1.43 ₂₈₀ The concentration is determined. Monoclonal antibodies can be aliquoted and stored at-80 ℃.

To determine whether a selected monoclonal antibody binds to a unique epitope, either directed mutagenesis or multi-site directed mutagenesis can be used.

To determine the isotype of antibodies, isotype ELISA (e.g., zymed, roche Diagnostics) with different commercial kits can be performed. Wells of the microtiter plates may be coated with anti-mouse Ig. After blocking, the plates were reacted with monoclonal antibodies or purified isotype controls for 2 hours at ambient temperature. The wells may then be reacted with mouse IgG1, igG2a, igG2b or IgG3, igA or mouse IgM-specific peroxidase-conjugated probes. After washing, the plates can be visualized with ABTS substrate (1 mg/ml) and at OD _405-650 And (5) analyzing. Alternatively, isoStrip mouse monoclonal antibody typing kits may be used as described by the manufacturer.

To demonstrate the presence of antibodies or monoclonal antibodies in the serum of immunized mice bound to live cells expressing the antigen, flow cytometry can be used. Cell lines expressing the antigen naturally or after transfection and negative controls lacking antigen expression (grown under standard growth conditions) can be mixed with different concentrations of monoclonal antibodies in hybridoma supernatants or in PBS containing 1% fbs and incubated at 4 ℃ for 30min. After washing, APC-or Alexa-fiur 647- (AF 647) -labeled anti-IgG antibodies can bind to antigen-binding monoclonal antibodies as primary antibodies under the same conditions. Single living cells are gated using FACS instruments for light and side scatter properties, and samples can be analyzed by flow cytometry. To distinguish antigen-specific monoclonal antibodies from non-specific binders in a single measurement, a co-transfection method may be employed. Cells transiently transfected with plasmids encoding antigens and fluorescent markers can be stained as described above. Transfected cells may be detected in a different fluorescent channel than antibody-stained cells. Because most transfected cells express two transgenes, antigen-specific monoclonal antibodies preferentially bind to cells expressing fluorescent markers, whereas non-specific antibodies bind to untransfected cells at a comparable rate. In addition to or instead of flow cytometry assays, alternative assays to fluorescence microscopy may be used. As described above, cells may be stained and detected by fluorescence microscopy.

To demonstrate the presence of antibodies or monoclonal antibodies in the serum of immunized mice bound to live cells expressing the antigen, immunofluorescence microscopy can be used for analysis.

Cell extracts from antigen-expressing cells and appropriate negative controls can be prepared and subjected to Sodium Dodecyl Sulfate (SDS) polyacrylamide gel electrophoresis. After electrophoresis, the separated antigens are transferred to nitrocellulose membranes, blocked and probed with the monoclonal antibody to be tested. IgG binding can be detected using anti-mouse IgG peroxidase and visualized with ECL substrate.

The reactivity of the antibodies with the antigen can be further tested by immunohistochemistry in a manner well known to the skilled person, such as using frozen sections from non-cancerous tissue or cancer tissue samples fixed with paraformaldehyde or acetone or paraffin embedded tissue sections from non-cancerous tissue or cancer tissue samples fixed with paraformaldehyde, obtained from patients during conventional surgical procedures or from mice carrying xenograft tumors vaccinated with cell lines that spontaneously express the antigen or express the antigen after transfection.

Antibodies can be tested for their ability to mediate phagocytosis and kill cells expressing CLDN 18.2. The in vitro monoclonal antibody activity test will provide an initial screen prior to testing in vivo models.

ADCC test: polymorphonuclear cells (PMNs), NK cells, monocytes or other effector cells from healthy donors can be purified by Ficoll Hypaque density centrifugation, followed by lysis of the contaminating erythrocytes. Washed effector cells may be suspended in RPMI supplemented with 10% heat-inactivated fetal bovine serum or 5% heat-inactivated human serum and mixed with 51 Cr-labeled CLDN18.2 expressing target cells at different ratios of effector cells to target cells. Alternatively, the target cells may be labeled with a fluorescence enhancing ligand (BATDA). The highly fluorescent chelate of europium with enhanced ligand released from dead cells can be measured by a fluorometer. Another alternative technique may utilize transfection of target cells with luciferase. The added fluorescein can then only be oxidized by living cells. Purified anti-CLDN 18.2 IgG may then be added at various concentrations. An unrelated human IgG may be used as a negative control. The assay may be performed at 37 ℃ for 4 to 20 hours, depending on the effector cell type used. By measuring 51Cr release or the presence of EuTDA chelate in the culture supernatant, cytolysis of the sample can be determined. Alternatively, the luminescence caused by the oxidation of the fluorescent yellow may be a measure of living cells. The anti-CLDN 18.2 monoclonal antibodies can also be tested in different combinations to determine whether multiple monoclonal antibodies enhance cytolysis.

CDC test: monoclonal anti-CLDN 18.2 antibodies can be tested for their ability to mediate CDC using a variety of known techniques. For example, serum complement can be obtained from blood in a manner known to the skilled artisan. To determine CDC activity of a mAb, different methods can be used. For example, 51Cr release may be measured or increased membrane permeability may be assessed using an Propidium Iodide (PI) exclusion assay. Briefly, target cells can be washed and 5X 105/ml incubated with mAb at various concentrations for 10-30min at room temperature or 37 ℃. Serum or plasma can then be added to a final concentration of 20% (v/v) and the cells incubated at 37℃for 20-30min. All cells from each sample can be added to the PI solution in the FACS tube. The mixture can then be analyzed immediately by flow cytometry analysis using a FACSArray.

In an alternative assay, induction of CDC may be determined on adherent cells. In one embodiment of the assay, cells were seeded at a density of 3x 104 cells/well in tissue-culture flat bottom microtiter plates 24h prior to the assay. The next day, the growth medium was removed and the cells were incubated with antibodies in triplicate. Control cells were incubated with growth medium or 0.2% saponin in growth medium for determining background lysis and maximum lysis, respectively. After incubation at room temperature for 20min, the supernatant was removed and DMEM containing 20% (v/v) human plasma or serum (pre-warmed to 37 ℃) was added to the cells and incubated for an additional 20min at 37 ℃. All cells from each sample were added to propidium iodide solution (10. Mu.g/ml). The supernatant was then replaced with PBS containing 2.5. Mu.g/ml ethidium bromide and fluorescence emission after excitation at 520nm was measured at 600nm using a Tecan Safire. The percentage of specific lysis was calculated as follows: specific lysis% = (fluorescent sample-fluorescent background)/(fluorescent maximum lysis-fluorescent background) x 100.

Monoclonal antibody-induced apoptosis and cell proliferation inhibition: to test for the ability to trigger apoptosis, a monoclonal anti-CLDN 18.2 antibody, for example, can be incubated with CLDN18.2 positive tumor cells (e.g., SNU-16, DAN-G, KATO-III or CLDN18.2 transfected tumor cells) for about 20 hours at 37 ℃. Cells can be harvested, washed in annexin-V binding buffer (BD biosciences) and incubated with annexin-V conjugated FITC or APC (BD biosciences) in the dark for 15min. All cells from each sample can be added to the PI solution (10 μg/ml in PBS) in FACS tube and immediately assessed by flow cytometry (as above). Alternatively, the overall inhibition of cell proliferation by monoclonal antibodies can be detected using commercially available kits. The DELFIA cell proliferation kit (Perkin-Elmer, cat. No. AD0200) is a non-isotopic immunoassay based on 5-bromo-2' -deoxyuridine (BrdU) incorporation measurements during DNA synthesis of proliferating cells in microplates. Doped BrdU was detected using europium-labelled monoclonal antibodies. To allow antibody detection, fix cells and denature DNA using Fix solution. Unbound antibodies were washed away and DELFIA inducer was added to dissociate europium ions from the labeled antibodies into solution where they formed highly fluorescent chelates with the components of the DELFIA inducer. The measured fluorescence-using time resolved fluorometry in the assay-is proportional to DNA synthesis in the cells of each well.

Cross-reactivity with 18.1 was detected by flow-through methods using CHO stable cells (Cell Pool), and the antibody CLDN-BC-P1026-hH1 was a CLDN 18.2-specific antibody, which did not react with CLDN 18.1.

The information relating to the P1026 antibody is as follows:

cell line CLDN-BC-P1026-hH1;

the source is as follows: the antigen is obtained by immunizing fully human mice.

As used herein, the term "cell" generally refers to a cell into which a vector is introduced, including many cell types, such as prokaryotic cells, such as Escherichia coli (Escherichia coli) and bacillus subtilis (Bacillus subtilis), fungal cells, such as yeast cells or Aspergillus (Aspergillus) cells, insect cells, such as S2 drosophila cells or Sf9, or animal cells, such as fibroblasts, CHO cells, COS cells, NSO cells, heLa cells, BHK cells, HEK293 cells, MC38 cells or human cells.

As used herein, the term "conditions that enable expression" generally refers to conditions that enable expression of an antibody, antigen-binding fragment thereof, or variant thereof of the present application. In some embodiments, the conditions that enable expression include, but are not limited to, incubation time, temperature, and medium, and may depend on the cell type, and may be readily determined by one of ordinary skill in the art. In some embodiments, during the production of the antibodies, antigen-binding fragments thereof, or variants thereof of the present application, the cells are grown in culture and in any device useful for growing cultures, including fermentors. Cells may be grown as a monolayer or attached to a surface. Alternatively, cells may be grown in suspension. Cells can be grown in serum-free medium.

As used herein, the term "cancer" generally refers to a group of diseases involving abnormal cell growth that have the potential to invade or spread to other parts of the body. Cancer is fundamentally a disease of regulation of tissue growth. In order to transform normal cells into cancer cells, genes that regulate cell growth and differentiation must be altered. The genes affected fall into two broad categories. Oncogenes are genes that promote cell growth and proliferation. Tumor suppressor genes are genes that inhibit cell division and survival. Malignant transformation can occur through the formation of novel oncogenes, inappropriate overexpression of normal oncogenes, or under-expression or inactivation of tumor suppressor genes. In general, to transform normal cells into cancer cells, multiple gene changes are required. Cancers are classified by cell type, including carcinomas, sarcomas, lymphomas and leukemias, germ cell tumors, and blastomas.

As used herein, the term "T cell" generally refers to a type of lymphocyte (a subtype of leukocyte) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes (such as B cells and natural killer cells) by the presence of T cell receptors on the cell surface. They are called T cells because they mature from thymic cells in the thymus. Most human T cells rearrange their alpha and beta chains at the cell receptor and are called alpha beta T cells (αβt cells) which are part of the adaptive immune system. Specialized γδ T cells (a small fraction of T cells in humans, more common in ruminants) have invariant T cell receptors, have limited diversity, can efficiently present antigens to other T cells, and are considered to be part of the innate immune system.

As used herein, the term "MC38" cells refers to mouse colon cancer cells. MC38 mouse colorectal cancer cells overexpress human claudin18.2, mimicking colorectal cancer that highly expressed claudin 18.2. The use of mouse colorectal cancer cells is intended to mimic human conditions as much as possible in the context of immunocompetent mice.

As used herein, the term "pharmaceutically acceptable excipient" generally refers to any and all solvents, dispersion media, coatings, isotonic and absorption delaying agents, and the like, that are compatible with pharmaceutical administration. In some embodiments, the excipient of CLDN18.2 stabilizes or increases its expression. In some embodiments, the CLDN18.2 expression stabilizer or expression enhancer is oxaliplatin and/or 5-FU. In some embodiments, CLDN18.2 is preferably expressed on the cell surface of cancer cells when administered. Further, the cancer cells are cancer cells related to claudin18.2, for example, solid tumor cells such as gastric cancer cells, pancreatic cancer cells, esophageal cancer cells, intestinal cancer cells, liver cancer cells, lung cancer cells, and the like. The CLDN18.2 antibodies or antigen-binding portions thereof of the present application have in vivo anti-tumor effects.

As used herein, the term "about" generally refers to an approximation of a given value that may be reasonably inferred based on ordinary skill in the art, including equivalent values and approximations due to experimental and/or measurement conditions of the given value. For example, it may refer to a value that is no more than 10% higher or lower than the value to which the term is modified. For example, the term "about 5. Mu.g/kg" refers to a range of 4.5. Mu.g/kg to 5.5. Mu.g/kg. As another example, "about 1 hour" means a range of 48 minutes to 72 minutes.

As used herein, the term "effective amount" generally refers to a dosage sufficient to provide a sufficiently high concentration to impart a beneficial effect to its recipient. The particular therapeutically effective dosage level of any particular subject will depend upon a variety of factors including the disorder being treated, the severity of the disorder, the activity of the particular component, the route of administration, the rate of clearance, the duration of treatment, the age, weight, sex, diet and general health of the subject, and other related factors.

As used herein, the term "binding specificity" generally refers to the ability to specifically bind (e.g., immunoreact with) a given target (while not binding or substantially not binding a non-target). The antibodies (or antigen binding fragments or variants thereof) of the present application may be monospecific and comprise one or more binding sites that specifically bind to a target, or may be multispecific (e.g., bispecific or trispecific) and comprise two or more binding sites that specifically bind to the same or different targets.

As used herein, the term "modification" generally refers to any manipulation of the peptide backbone (e.g., amino acid sequence) of a polypeptide or any post-translational modification (e.g., glycosylation). For example, the modification is compared to the sequence of the corresponding wild-type polypeptide. Modifications may be substitutions, additions and/or deletions of one or more amino acids (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more).

As used herein, the term "amino acid substitution" generally refers to the replacement of one amino acid with another at a particular position in a polypeptide.

As used herein, the term "isolated polynucleotide" generally refers to a polymeric form of nucleotides (whether deoxyribonucleotides or ribonucleotides, or analogs thereof) of any length, isolated from its natural environment or synthesized.

In one aspect, the present application provides antibodies, antigen-binding fragments thereof, or variants thereof, that bind to CLDN 18.2. The antibody, antigen-binding fragment thereof, or variant thereof, can specifically bind to CLDN18.2 and does not substantially bind to CLDN 18.1.

In this application, it is preferred that the antibody, antigen-binding fragment thereof, or variant thereof remain in monomeric form (e.g., as dimers, trimers, or other multimers).

Antibodies according to the present application may be selected from: monoclonal antibodies, chimeric antibodies, humanized antibodies, fully human antibodies, and bispecific antibodies.

Antigen binding fragments according to the present application may be selected from: fab fragments, fab' fragments, F (ab) ₂ Fragments, F (ab') ₂ Fragments, fv fragments and ScFv.

In some cases, a variant may be a polypeptide differing from an antibody or antigen binding fragment thereof according to the present application in the addition, deletion, or substitution of one or more amino acids (such as 1-50, 1-40, 1-30, 1-20, 1-15, 1-14, 1-13, 1-12, 1-11, 1-10, 1-9, 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, or 1-2 amino acids).

In some cases, a variant may be a polypeptide having at least 80% (e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or more) sequence identity to an antibody or antigen binding fragment thereof according to the present application.

In some cases, the reference antibody comprises light chain LCDR1-3 and heavy chain HCDR1-3, heavy chain HCDR1 may comprise an amino acid sequence as set forth in SEQ ID NO:1, and heavy chain HCDR2 may comprise an amino acid sequence as set forth in SEQ ID NO

The amino acid sequence shown in SEQ ID NO. 2, heavy chain HCDR3 may comprise the amino acid sequence shown in SEQ ID NO. 3, light chain LCDR1 may comprise the amino acid sequence shown in SEQ ID NO. 4, light chain LCDR2 may comprise the amino acid sequence shown in SEQ ID NO. 5, and light chain LCDR3 may comprise the amino acid sequence shown in SEQ ID NO. 6.

In some embodiments, the method of making an anti-CLDN 18.2 antibody is conventional in the art. In certain embodiments, the antibodies produced do not elicit a detrimental immune response in the animal (e.g., human) to be treated. In some embodiments, the antibodies, antigen binding fragments, or derivatives of the present disclosure are modified to reduce their immunogenicity using art-recognized techniques. For example, the antibodies may be humanized, primatized, deimmunized or chimeric antibodies may be prepared. In some embodiments, the antibodies of the present application are fully human antibodies.

Preparation of scFv can be seen in techniques for producing single chain units (U.S. Pat. No. 4,694,778; bird, science242:423-442 (1988), huston et al, proc. Natl. Acad. Sci. USA 55:5879-5883 (1988) and Ward et al, nature334:544-554 (1989) and Nie et al, antibody Therapeutics)

3 (1):18-62 (2020)). The heavy and light chain fragments of the Fv region are bridged by amino acids to form single chain units, resulting in a single chain fusion peptide. Techniques for assembling functional Fv fragments in E.coli can also be used (Skerra et al Science 242:1038-1041 (1988)).

Examples of techniques that can be used to produce single chain Fv (scFv) and antibodies include, for example, U.S. Pat. Nos. 4,946,778 and 5,258,498, and Huston et al, methods in Enzymology 203:203-46-88 (1991), shu et al, proc.Natl. Sci.USA90:1995-1999 (1993) and Skerra et al, science

240:1038-1040 (1988). For certain uses including the use of antibodies in humans and in vitro detection assays, chimeric, humanized or fully human antibodies may be used. Chimeric antibodies are a class of molecules in which different portions of the antibody are derived from different animal species, such as antibodies having a variable region of murine monoclonal antibodies and a constant region of human immunoglobulins. Methods of producing chimeric antibodies are known in the art, see Morrison, science 229:1202 (1985); oi et al, bioTechniques 4:214 (1986); gillies et al, J.Immunol.methods 125:191-202 (1989); neuberger et al, nature

372:604-608 (1984); takeda et al, nature314:452-454 (1985); and U.S. Pat. nos. 5,807,715, 4,816,567, and 4,816,397, the entire contents of which are incorporated herein by reference.

In some embodiments, hybridoma technology is employed to produce antibodies of the invention. Monoclonal antibodies are prepared using, for example, the hybridoma method, such as described by Kohler and Milstein, nature,256:495 (1975). In the hybridoma method, a mouse, hamster, or other appropriate host animal is typically immunized with an immunizing agent to cause lymphocytes to produce or to produce antibodies that specifically bind the immunizing agent.

The immunizing agent will typically include the protein antigen, a fragment thereof, or a fusion protein thereof. Typically, if a human cell is desired, peripheral blood lymphocytes are used; if a non-human mammalian source is desired, spleen lymphocytes or lymph node cells are used. In some embodiments, spleen lymphocytes are employed; lymphocytes are then fused with an immortalized cell line using a suitable fusion agent, such as polyethylene glycol, to form a hybridoma cell (Goding, monoclone antibodies: principles and Practice, academic Press, (1986) pages 59-103). Immortalized cell lines are typically transformed mammalian cells, in particular myeloma cells of rodent, bovine and human origin. Typically, a rat or mouse myeloma cell line is employed. In some embodiments, spleen lymphocytes and mouse myeloma cells are used for fusion. The hybridoma cells may be cultured in a suitable medium, which in some embodiments contains one or more substances that inhibit the growth or survival of the unfused immortalized cells. For example, if the parent cell lacks hypoxanthine-guanine phosphoribosyl transferase (HGPRT or HPRT), the culture medium for the hybridoma typically includes hypoxanthine, aminopterin, and thymidine ("HAT medium"), which substances prevent HGPRT-deficient cell growth. In some embodiments, the binding specificity of monoclonal antibodies produced by hybridoma cells is determined by immunoprecipitation or by an in vitro binding assay, such as a Radioimmunoassay (RIA) or an enzyme-linked immunosorbent assay (ELISA). Such techniques and assays are known in the art. The binding affinity of monoclonal antibodies can be determined, for example, by Scatchard analysis of Munson and Poluard, anal. Biochem.,107:220 (1980). Furthermore, in therapeutic applications of monoclonal antibodies, it is important to identify antibodies with high specificity and high binding affinity for the target antigen.

After the desired hybridoma cells are identified, the clones can be subcloned using limiting dilution steps and grown using standard methods (see Goding, monoclonal Antibodies: principles and Practice, academic Press, (1986), pages 59-103). Suitable media for this purpose include, for example, dulbecco's modified Eagle's Medium and RPMI-1640 medium, and the like.

In some embodiments, monoclonal antibodies secreted by the subclones may be isolated or purified by conventional techniques, such as protein A-sepharose, hydroxylapatite chromatography, gel electrophoresis, dialysis, or affinity chromatography.

Monoclonal antibodies can also be prepared by recombinant DNA methods, such as described in U.S. Pat. No.4,816,567. DNA encoding the monoclonal antibodies described herein can be isolated and sequenced using conventional methods (e.g., by using oligonucleotide probes that are capable of binding specifically to the genes of the heavy and light chains of the antibodies). The DNA encoding the antibodies described herein may also be synthesized according to conventional methods based on the design of the antibody sequence. The isolated or synthetic DNA is inserted into an expression vector, which is then transfected into a host cell such as Chinese Hamster Ovary (CHO) cells, human Embryonic Kidney (HEK) 293 cells, simian COS cells, per.ns0 cells, SP2/0, YB2/0 or myeloma cells that do not otherwise produce immunoglobulins, thereby obtaining synthetic monoclonal antibodies in the recombinant host cell.

In some embodiments, the antibody or antigen binding fragment thereof of the invention is produced using hybridoma technology, immunizing a mouse with a protein preparation comprising CLDN18.2, fusing splenic lymphocytes from the mouse after immunization with myeloma cells, screening for hybridomas by CLDN18.2 protein, limiting dilution of positive hybridomas, further subcloning, and re-identifying the binding capacity of the hybridoma strain to CLDN18.2 protein to produce an anti-CLDN 18.2 antibody. In some embodiments, the mice are female Balb/c mice that are 6-8 weeks old.

The binding specificity of the antibodies or antigen binding fragments disclosed herein can be detected by in vitro assays, such as co-immunoprecipitation, radioimmunoassay (RIA), or enzyme-linked immunosorbent assay (ELISA).

For certain uses including the use of antibodies in humans and in vitro detection assays, chimeric, humanized or fully human antibodies may be used in some embodiments. Chimeric antibodies are a class of molecules in which different portions of the antibody are derived from different animal species, such as antibodies having a variable region of murine monoclonal antibodies and a constant region of human immunoglobulins. Methods of producing chimeric antibodies are known in the art, see Morrison, science 229:1202 (1985); oi et al, bioTechniques4:214 (1986), gillies et al, J.Immunol. Methods 125:191-202 (1989) and U.S. Pat. Nos. 5,807,715, 4,816,567 and 4,816397, the entire contents of which are incorporated herein by reference.

Fully human antibodies can also be produced by transgenic mice that are incapable of expressing functional endogenous immunoglobulins but are capable of expressing human immunoglobulin genes. For example, human heavy and light chain immunoglobulin gene complexes may be introduced randomly or by homologous recombination into mouse embryonic stem cells. Alternatively, human variable, constant and diversity regions may be introduced into mouse embryonic stem cells in addition to human heavy and light chain genes. Immunoglobulin genes of the mouse heavy and light chains may be introduced into the human immunoglobulin loci by homologous recombination to disable function. In particular, homozygous deletion of the JH region may prevent endogenous antibody production. The modified embryonic stem cells are expanded and microinjected into blasts to generate chimeric mice. The chimeric mice are then bred to produce homozygous offspring expressing the humanized antibody. Transgenic mice are immunized in a conventional manner with a selected antigen, e.g., all or part of the desired polypeptide target. Monoclonal antibodies targeting antigens can be obtained from immunized transgenic mice using conventional hybridoma techniques. The human immunoglobulin transgenes carried by transgenic mice rearrange during B cell differentiation, followed by class switching and somatic mutation. Thus, igG, igA, igM and IgE antibodies useful for therapy can be produced using this technology. In the present application, the anti-CLDN 18.2 antibody may be a fully human antibody.

In other embodiments, DNA encoding the desired monoclonal antibody can be readily isolated and sequenced using conventional procedures (e.g., using oligonucleotide probes capable of specifically binding to genes encoding murine antibody heavy and light chains). Once isolated, the DNA can be placed into an expression vector and then transfected into a prokaryotic or eukaryotic host cell, such as an e.coli cell, simian COS cell, chinese Hamster Ovary (CHO) cell, or myeloma cell that does not otherwise produce immunoglobulin. Isolated DNA (which may be synthetic as described herein) may also be used to prepare sequences of constant and variable regions of antibodies, as described in U.S. patent 5,658,570, which is incorporated herein by reference in its entirety. The method extracts RNA from selected cells and converts it into cDNA, which is then amplified by PCR techniques using Ig-specific primers. Suitable probes for this purpose are also mentioned in U.S. Pat. No. 5,658,570.

Furthermore, one or more CDRs of an antibody or antigen binding fragment of the invention can be inserted into a framework region, e.g., into a human framework region, using conventional recombinant DNA techniques to construct a humanized non-fully human antibody. The framework regions may be naturally occurring or consensus framework regions, preferably human framework regions (see Chothia et al, J. Mol. Biol.278:457-479 (1998), which lists a range of human framework regions). Some polynucleotides may encode antibodies that bind specifically to at least one epitope of an antigen of interest produced by the combination of framework regions and CDRs. One or more amino acid substitutions within the framework regions may be selected to improve binding of the antibody to its antigen. In addition, substitution or deletion of cysteine residues in one or more of the variable regions involved in interchain disulfide formation may be performed in this manner, thereby producing an antibody molecule lacking one or more interchain disulfide bonds. Other variations on polynucleotides within the skill of the art are also encompassed by the present invention.

In addition, another efficient method for producing recombinant antibodies is disclosed in Newman, biotechnology 10:1455-1460 (1992), which in particular enables the production of primate antibodies comprising monkey variable and human constant region sequences, the entire content of which is incorporated herein by reference. In addition, this technology is also mentioned in commonly assigned U.S. Pat. nos. 5,658,570, 5,693,780 and 5,756,096, the entire contents of each of which are incorporated herein by reference.

Antibodies can be prepared by using conventional recombinant DNA techniques. Vectors, cell lines, etc. for antibody production can be selected, constructed and cultured using techniques well known to those skilled in the art. These techniques are described in various laboratory manuals and major publications, such as Recombinant DNA Technology for Production of Protein Therapeutics in Cultured Mammalian Cells, D.L.Hacker, F.M.Wurm, in Reference Module in Life Sciences,2017, the entire contents of which, including the supplementary contents, are incorporated by reference in their entirety.

In some embodiments, DNA encoding an antibody may be synthesized according to conventional methods from the antibody amino acid sequences described herein, placed into an expression vector, and then transfected into a host cell, and the transfected host cell cultured in culture medium to produce monoclonal antibodies. In some embodiments, the expression antibody vector comprises at least one promoter element, an antibody coding sequence, a transcription termination signal, and a polyA tail. Other elements include enhancers, kozak sequences, and donor and acceptor sites for RNA splicing flanking the insertion. Efficient transcription can be obtained by the early and late promoters of SV40, the long terminal repeats from retroviruses such as the early promoters of RSV, HTLV1, HIVI and cytomegalovirus, and other cellular promoters such as actin promoters may be used. Suitable expression vectors may include pIRES1neo, pRetro-Off, pRetro-On, PLXSN, or Plncx, pcDNA3.1 (+/-), pcDNA/Zeo (+/-), pcDNA3.1/Hygro (+/-), PSVL, PMSG, pRSVcat, pSV2dhfr, pBC12MI and pCS2, among others. Commonly used mammalian host cells include 293 cells, cos1 cells, cos7 cells, CV1 cells, murine L cells, CHO cells and the like.

In some embodiments, the insert should contain a selectable marker, common selectable markers including dihydrofolate reductase, glutamine synthetase, neomycin resistance, hygromycin resistance, and the like, to facilitate selection and isolation of transfected cells. The constructed plasmid is transfected into host cells without the genes, and the transfected cells grow in a large quantity after being cultured by a selective medium to generate target proteins to be obtained.

In addition, mutations may be introduced into the nucleotide sequences encoding the antibodies of the invention using standard techniques known to those skilled in the art, including, but not limited to, site-directed mutagenesis and PCR-mediated mutagenesis that result in amino acid substitutions. Variants (including derivatives) encode substitutions of less than 50 amino acids, substitutions of less than 40 amino acids, substitutions of less than 30 amino acids, substitutions of less than 25 amino acids, substitutions of less than 20 amino acids, substitutions of less than 15 amino acids, substitutions of less than 10 amino acids, substitutions of less than 5 amino acids, substitutions of less than 4 amino acids, substitutions of less than 3 amino acids, or substitutions of less than 2 amino acids relative to the original heavy and light chain variable regions. Alternatively, mutations may be introduced randomly along all or part of the coding sequence, for example by saturation mutagenesis, and the resulting mutants may be screened for biological activity to identify mutants that retain activity.

The invention also provides the application of the medicine or the composition taking the anti-CLDN 18.2 antibody or the antigen binding fragment as the main component and the application method. In some embodiments, methods for treating or ameliorating various types of cancer or tumor-related diseases are provided, the methods comprising administering to a patient in need thereof an effective dose of an anti-CLDN 18.2 antibody or antigen-binding fragment. In some embodiments, there is provided the use of an anti-CLDN 18.2 antibody or antigen-binding fragment for treating or ameliorating a cancer or tumor-related disorder. In some embodiments, there is provided the use of the anti-CLDN 18.2 antibody or antigen-binding fragment in the manufacture of a medicament for treating or ameliorating a cancer or tumor-related disorder.

The specific dosage and treatment regimen for any particular patient will depend on a variety of factors including the particular antibody, antigen-binding fragment or derivative used, the age and weight of the patient, the general health, sex and diet of the patient, as well as the time of administration, frequency of excretion, drug combination, and the severity of the particular disease being treated. These factors are judged by medical care personnel included within the scope of one of ordinary skill in the art. The dosage will also depend on the individual patient to be treated, the route of administration, the type of formulation, the nature of the compound used, the severity of the disease and the desired effect. The dosages used can be determined by pharmacological and pharmacokinetic principles well known in the art. For example, in some embodiments, the antibody of the invention is administered to a patient at a dose of 0.01mg/kg to 100mg/kg of patient body weight per time; in some embodiments, the administration is once every 1 week, 2 weeks, 3 weeks, or month.

Methods of administration of antibodies and antigen binding fragments thereof include, but are not limited to, intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, nasal, epidural injection, and oral. The antibody, antigen-binding fragment, or composition may be administered by any convenient route, for example by infusion or bolus injection, absorbed through epithelial or skin mucosa (e.g., oral mucosa, rectal and intestinal mucosa, etc.), and may be co-administered with other bioactive agents. Thus, pharmaceutical compositions comprising the antibodies, antigen binding fragments of the invention may be administered orally, rectally, parenterally, intracisternally, intravaginally, intraperitoneally, topically (e.g., by powders, ointments, drops, or transdermal patches), bucally, or by oral or nasal spray.

The term "parenteral" as used herein refers to modes of administration including intravenous, intramuscular, intraperitoneal, intrasternal, subcutaneous and intra-articular injection and infusion.

The mode of administration may be systemic or local.

The antibodies, antigen-binding fragments, or pharmaceutical compositions of the invention may be topically applied to an area in need of treatment; the following means may be used, but are not limited to: local infusion during surgery, for example local application in combination with a post-operative wound dressing, is achieved by injection, through a catheter, by means of suppositories or by means of implants which are porous, non-porous or gelatinous materials, including membranes (e.g. silicone rubber membranes) or fibres. In some embodiments, when administering the proteins (including antibodies) of the present invention, care must be taken to use materials that do not absorb the protein.

In some embodiments, the compositions of the invention comprise an antibody-encoding nucleic acid or polynucleotide, which can be administered in vivo by constructing it as part of a suitable nucleic acid expression vector to facilitate expression of the protein it encodes, and then administering the part of the vector to become an intracellular part by, for example, using a retroviral vector (see U.S. Pat. No. 4,980,286), or by direct injection, or by using microprojectile bombardment (e.g., gene gun; biolistic, dupont), or coated with a lipid or cell surface receptor or transfection reagent, or by ligation with a homeobox-like peptide known to enter the nucleus (see, e.g., joliot et al, 1991,Proc.Natl.Acad.Sci.USA 88:1864-1868), and the like. Alternatively, the nucleic acid may be introduced into the cell by homologous recombination and integrated into the host cell DNA for expression.

Methods for treating diseases are typically performed in vitro by administering an antibody, antigen binding fragment or derivative of the invention, followed by in vivo testing for the desired therapeutic or prophylactic activity in an acceptable animal model, and finally administration to the human body. Suitable animal models (including transgenic animals) are well known to those of ordinary skill in the art. For example, in vitro assays useful in demonstrating the therapeutic use of the antibodies or antigen binding fragments of the invention include the effect of the antibodies or antigen binding fragments on a cell line or patient tissue sample. The effect of the antibody or antigen binding fragment on the cell line and/or tissue sample may be detected using techniques known to those skilled in the art, such as those disclosed elsewhere herein. In accordance with the present disclosure, in vitro assay experiments useful for determining whether to administer a specific antibody or antigen binding fragment include in vitro cell culture experiments in which a patient tissue sample is cultured in culture and exposed to or otherwise administered a compound, and observing the effect of such compound on the tissue sample.

Various known delivery systems may be used to administer the antibodies of the invention or polynucleotides encoding the antibodies of the invention, e.g., encapsulated in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the compounds, receptor-mediated endocytosis (see, e.g., wu and Wu,1987, j. Biol. Chem. 262:4429-4432), construction of nucleic acids as part of a retrovirus or other vector, and the like.

In some embodiments, the antibodies or antigen binding fragments of the present application are used in combination with other therapeutic methods. The anti-CLDN 18.2 antibodies or antigen-binding fragments of the invention can be used in combination with other therapeutic or prophylactic regimens, including administration of one or more antibodies or antigen-binding fragments of the invention, together with one or more other therapeutic agents or methods. In some embodiments, other treatment regimens include, but are not limited to, radiation therapy, chemotherapy, hormonal therapy, and the like. For combination therapy, the antibody may be administered simultaneously or separately with other therapeutic agents. When administered separately, the antibodies of the invention may be administered before or after administration of another other therapeutic agent.

In some embodiments, the antibodies of the invention are administered in combination with a chemotherapeutic agent. In some embodiments, chemotherapeutic agents that may be administered with an antibody of the invention include, but are not limited to, carboplatin (berdine), cisplatin (cisplatin, cisplatin-AQ), cyclophosphamide (oncodesine, cyclophosphamide), docetaxel (taxotere), doxorubicin (adriamycin), erlotinib (tarceva), etoposide (vas Bi Shi), fluorouracil (5-FU), gemcitabine (exercise), imatinib mesylate (gliguard), irinotecan (irinotecan), methotrexate (diazonium sheet, methotrexate sodium, methotrexate), paclitaxel (Taxol, abraxane), sorafenib (degamme), sunitinib (sotan), topotecan (Hycamtin), vincristine (Oncovin, vincasar PFS), and vinblastine (Velban).

In some embodiments, the antibodies of the invention are administered in combination with a cytokine, chemokine, or costimulatory molecule. In some embodiments, cytokines, chemokines or co-stimulatory molecules that may be administered with an antibody of the invention include, but are not limited to CCR7, CCL19, CCL21, CCL2, CCL3, CCL5, CCL16, CXCR4, CXCR7, CXCL12, interleukins (e.g., IL-1-IL 17), interferons (e.g., IFN alpha 1, IFN alpha 8, IFN alpha 10, IFN alpha 13, IFN alpha 14, IFN alpha 16, IFN alpha 17, IFN alpha 21, IFN beta 1, IFNW, IFNE1 and IFNK), hematopoietins, TGFs (e.g., TGF-alpha, TGF-beta, and other members of the TGF family), 4-1BB-L, CD137, CD 137-4 GITR, GITRL, fas-L, TNFR1, TRAIL-R2, p 75-R, DR, RANK, EDAR1, XR 114, fn, oy/Trade, TAJ, TNFRII, HVEM, CD, CD 40-4, and related gluco receptor (e.g., EDA-35), and the like, and the apoptosis-related proteins (e.g., TNF receptor-related protein(s).

In some embodiments, the antibodies of the present application are administered in combination with an immunotherapeutic agent. In some embodiments, immunotherapeutic agents that may be administered with the antibodies of the invention include, but are not limited to, ab Fu Shan antibody (CA-125), acipimab (CD 41), adamab (EpCAM), alfuzumab (CD 20), pezizumab (VEGFR 2), pentetate, abitumomab (CEA), amatuxi monoclonal antibody (MORAB-009), MSub>A AnnSub>A mab (TAG-72), arabinomab (HLA-DR), aximomab (CEA), bavisuximab (phosphatidylserine), bei Tuo mab (CD 22), belimumab (BAFF), bevacizumab (VEGF-A), bivalitumumab (CD 44 v 6), rituximab (CD 19), brentuximab vedotin (CD 30TNFRSF 8), mecuzumab (mucin Canag), cantuzumab (MUC 1), kSub>A Luo Shankang, pentetan (prostate cancer cells), caruzumab (888), bei Tuo, anti-moxib (CD 2), and other anti-human anti-EGFR (EGFR), and other anti-tumor agents (CAR-1, EGFR-2, EGFR-R-4, EGFR-R-2, and other anti-tumor agents, emamectin (GD 3 ganglioside), efavuxib (EpCAM), elotuzumab (SLAMF 7), enavatuzumab (PDL 192), ensiltuximab (NPC-1C), epalzumab (CD 22), er Ma Suoshan (HER 2/neu, CD 3), irinotecan (integrin αvβ3), farletuzumab (folate receptor 1), FBTA05 (CD 20), ficlatuzumab (SCH 900105), phenytoin (IGF-1 receptor), flanvotuzumab (glycoprotein 75), fusappan monoclonal antibody (PDL 192), callicarpa-80), ganituzumab (IGF-I), gituzumab (CD 33), gevokizumab (IL-1 β), girentuximab (carbonic anhydrase 9 (CA-IX)), irtuzumab (CD 20), farletuzumab (CD 92), phen (CD 35), struzumab (CD 35) and (CD 35), trauzumab (CD 35) and Ustigmatuzumab (CD 35) as (CD 35), TRAuzumab (CD 35) as, TRAuzumab (FcUK-6), TRAuzumab (FcR 2), gatuximab (CD 80) Ganituzumab (Gtuzumab) and Gatuzumab (CD 33) as (CD 35) as well as anti-6) as anti-tumor (Fvjb 2, gevoku 1) and TRAuzumab (FcP 1) may be added, mepolimumab (IL-5), mi Lazhu mab (CD 74), midostat mab (GD 3 ganglioside), mogamulizumab (CCR 4), moxetumo mab pasudotox (CD 22), tamitumumab (C242 antigen), tamitumumab (5T 4), nanatu mab (RON), necitumumab (EGFR), nituzumab (EGFR), nivolumuzumab (IgG 4), ofatuzumab (CD 20), olopatu mab (PDGF-rα), onertuzumab (human discrete factor receptor kinase), mo Aozhu mab (EpCAM), agouti mab (CA-125), oxeluumab (OX-40), panitumumab (EGFR), patrimumab (5T 4), pemtuzumab (MUC 1), pertuzumab (2/neu), panitumumab (adenocarcinoma antigen), rituximab (EGFR), rutuzumab (fauzumab (fauα), ralitumumab (fauzumab) 19), ralitumumab (fauzumab (fauα), ralitumumab (fauzumab) 2-35, ralitumumab (fauαb), ralitumumab (fauzumab (fauαb), ralitumumab (fauju) and fauju-35, tetuzumab (solid-borne protein C), teprotuzumab (CD 221), tiximumab (CTLA-4), teglizumab (TRAIL-R2), TNX-650 (IL-13), tositumomab (CD 20), trastuzumab (HER 2/neu), TRBS07 (GD 2), trastuzumab (CTLA-4), cet Mo Baijie mab (EpCAM), ublituxi mab (MS 4A 1), urilumab (4-1 BB), fu Luoxi mab (integrin. Alpha. 5. Beta.1).

The immune antigen and the anti-CLDN 18.2 antibody of the application can be obtained according to the sequence table disclosed in the application and the conventional technical means in the field, and are not described in detail herein. Antibodies or antigen binding fragments of the present application will be described by way of specific examples.

Example 1 preparation of anti-CLDN 18.2 antibodies

The anti-CLDN 18.2 antibody of the application performs codon optimization through CHO cell preference, synthesizes light and heavy chain sequences respectively, connects the heavy chain to a PEE12.4 expression vector, connects the light chain to a PEE6.4 expression vector, extracts plasmids after sequencing correctly, and utilizes the Expi CHO-S ^TM The expression system transiently transfected and purified the antibody. Wherein the sequence of the anti-CLDN 18.2 antibody is shown in table 1:

TABLE 1 amino acid sequence of anti-CLDN 18.2 antibody P1026

The method of producing antibodies is not described in detail in this application.

Example 2 detection of anti-CLDN 18.2 antibodies

The binding capacity of the anti-CLDN 18.2 antibodies to CLDN18.2 cells was tested using flow cytometry and further tested for their specificity of not binding to CLDN 18.1. Further, species crossover detection was performed against CLDN18.2 antibody.

The outline of the experimental procedure is as follows:

1. affinity detection

Respectively diluting a positive control antibody and an antibody to be detected to 20 mug/mL, taking a proper amount of CLDN18.2 and CLDN18.1 over-expressed cells, subpackaging the cells into 96-well plates, adding a proper amount of antibody into each well to enable the final concentration to be 10 mug/mL, incubating for 30min at 4 ℃, washing for 2 times by using PBS, adding a proper amount of anti-human IgG Fc AF647 fluorescent secondary antibody diluted in a ratio of 1:5000, incubating for 30min at 4 ℃, washing for 2 times by using PBS, adding a proper amount of PBS, and detecting a binding signal by using a flow cytometer. CHO-S and NC blank control were also set up. The activity of each antibody in binding to CLDN18.2 and CLDN18.1, respectively, is analyzed using FlowJo, preferably specifically binding to CLDN18.2 antibodies for the next step of EC50 detection and species crossover detection and affinity detection.

FIG. 1 is a human-derived CLDN18.2 and CLDN18.1 specific assay according to one embodiment of the invention; wherein the abscissa is the fluorescence intensity of Anti-hIgG-Fc-AF647, and the binding intensity of the antibody and the CLDN18.1 and the CLDN18.2 is detected; the ordinate SSC-H is the biased dispersion of the cells, and the complexity of the cells is detected. As shown in fig. 1, fully human antibody P1026 (a specific binding antibody to CLDN 18.2) binds only to CLDN18.2 and not CLDN18.1.

2. Activity detection

Respectively diluting the positive control antibody and the antibody to be detected to 20 mug/mL, taking a proper amount of human, murine and monkey CLDN18.2 over-expression cells CLDN18.2 and human CLDN18.1 over-expression cells, subpackaging the cells to a 96-well plate, adding a proper amount of antibody into each well to make the final concentration of the antibody be 10 mug/mL, incubating for 30min at 4 ℃, washing with PBS for 2 times, adding a proper amount of anti-human IgG Fc AF647 fluorescent secondary antibody diluted in a ratio of 1:5000, incubating for 30min at 4 ℃, washing with PBS for 2 times, adding a proper amount of PBS, and detecting a binding signal by a flow cytometer. CHO-S and NC blank control were also set up. The activity of each antibody in binding to CLDN18.2 and CLDN18.1 of human, murine and monkey origin, respectively, was analyzed using FlowJo.

FIG. 2 is an antibody species crossover result test according to one embodiment of the invention, wherein the abscissa is the fluorescence intensity of Anti-hIgG-Fc-AF647, and the binding intensity of the test antibody to CLDN 18.2; the ordinate SSC-H is the biased dispersion of the cells, and the complexity of the cells is detected. As shown in fig. 2, fully human antibody P1026 (specific binding antibody to CLDN 18.2) binds only to CLDN18.2 and does not bind to CLDN18.1; fully human antibody P1026 binds to CLDN18.2 in humans, mice and cynomolgus monkeys with comparable binding to the known CLDN18.2 inhibitor Zolbetuximab (IMAB 362).

3. Binding force detection

Respectively diluting the positive control antibody and the antibody to be detected in a gradient manner; taking a proper amount of CLDN18.2 over-expressed cells, subpackaging the cells into 96-well plates, adding a proper amount of antibody into each well, incubating for 30min at 4 ℃, washing with PBS for 2 times, and adding a proper amount of 1:5000 proportion diluted anti-human IgG Fc AF647 fluorescent secondary antibody, incubating for 30min at 4 ℃, washing 2 times with PBS, adding an appropriate amount of PBS, and detecting a binding signal by a flow cytometer. CHO-S and NC blank control were also set up. MFI of each antibody bound to CLDN18.2 was analyzed using FlowJo, and MFI was imported into GraphPad Prism analysis to obtain EC of each antibody bound to CLDN18.2 ₅₀ Values.

FIG. 3 is an antibody binding capacity assay according to one embodiment of the invention; wherein the abscissa is the antibody concentration and the ordinate is the average fluorescence intensity; table 2 is antibody binding and affinity detection data according to one embodiment of the present application. As shown in fig. 3 and table 2, the fully human anti-CLDN 18.2 antibody P1026 of the present application has stronger binding and affinity compared to the known CLDN18.2 inhibitor IMAB 362.

TABLE 2 fully humanized anti-CLDN 18.2 antibody binding and affinity assay data

Antibody name	EC 50 (μg/mL)	R 2	ka(1/Ms)	kd(1/s)	KD(M)
						IMAB362-IgG1	1.75	0.99	3.59*10 5	1.04*10 -3	2.89*10 -9
CLN-P1026-hH1	0.10	0.86	1.77*10 6	2.98*10 -4	1.69*10 -10

Example 3 ADCC Activity of anti-CLDN 18.2 antibody (antibody dependent cell-mediated cytotoxicity)

The experimental selection ADCC Reporter Bioassay evaluates ADCC activity of CLDN18.2 antibodies. The biological luminous reporter gene detection system uses artificially constructed effector cells to replace NK cells, and is matched with a high-sensitivity detection reagent, so that the biological activity of therapeutic antibody drugs based on an ADCC action mechanism in the activation path can be quantified, and the biological luminous reporter gene detection system is an action mechanism detection method.

Taking target cell MC 38-hCDN18.2 in logarithmic growth phase and effector cell FcR-TANK for cell counting, and respectively adjusting cell density to 4×10 ⁵ Individual/mL and 1.6X10 ⁶ Each cell was plated in 50. Mu.L/mL 96-well plates (4:1 effective target ratio). The antibodies to be tested were diluted to different concentrations and added to each well, each well having an antibody addition volume of 50 μl. Effector cells, target cells and antibodies were mixed in a ratio of 1:1:1 and incubated at 37℃for 4hr. Cell killing was detected using LDH method.

45min before incubation, adding 1 Xlysate into the maximum release hole of target cells, mixing, and culturing45min. After incubation, the culture plate is taken out, 50 mu L of supernatant is sucked into a new ELISA plate, 50 mu L of LDH detection solution is added into each hole, the hole plate is tapped, and after uniform mixing, incubation is carried out at room temperature and in a dark place for 10-30min. 50 mu L of stop solution is added into each hole, and the hole plates are tapped and mixed uniformly. The enzyme label instrument reads OD respectively ₄₉₀ And OD (optical density) ₆₈₀ And (3) calculating the increment. Cytotoxicity (Cytotoxicity)% was calculated according to the following formula:

wherein,

experimental values (Experimental) Experimental well increment values-culture medium control well increment values

Target cell spontaneous (Target Spontaneous): target cell self-release well increment value-culture medium control well increment value

Effector cell spontaneous value (Effector Spontaneous): effector cell spontaneous release well increment value-Medium control well increment value

Target Maximum (Target Maximum): target cell maximum release well increment value-equal volume control well increment value

Data nonlinear fitting was performed using graphpardprism as a curve, fitting mode [ Agonist]Response- -Variable slope (four parameters), to obtain the EC of the test sample ₅₀ Values. Human IgG1 served as negative control and CLN-Zolbetuximab-IgG1 served as positive antibody control.

Figure 4 is ADCC activity of CLDN18.2 antibodies against MC38 cells overexpressing human claudin18.2 according to one embodiment of the present application. Table 3 shows ADCC activity of the CLDN18.2 antibody against MC38 cells overexpressing human claudin 18.2. Among them, IMAB362-IgG1 served as the antibody positive control. As shown in fig. 4 and table 3, antibody P1026 has strong ADCC effect, and antibody P1026 has stronger ADCC effect than positive antibody CLN-zolbetuximab-IgG 1.

TABLE 3 ADCC Activity of CLDN18.2 antibodies against MC38 cells overexpressing human claudin18.2

Antibody name	EC 50 (μg/mL)	R 2
			IMAB362-IgG1	1.87	0.96
P1026-IgG1	0.31	0.96

Example 4 CDC Activity of anti-CLDN 18.2 antibody (complement dependent cytoxicity)

Taking 5×10 target cells in logarithmic growth phase ⁴ Plating 96-well plates, 90 μl of cell suspension per well, and incubating overnight. And (3) carrying out gradient dilution on the antibody to be tested to obtain different concentrations, and adding the different concentrations into each hole. 37 ℃,5% CO ₂ Incubating target cells with antibody for 30min, adding complement stock solution into all wells at 12.5 μl/well, mixing, and mixing at 37deg.C with 5% CO ₂ Incubate for 2hr. Cell killing was detected using prest Blue.

After the incubation, the plates were removed and the fluorescence values of each well at 560/590nm were measured by a microplate reader. Cytotoxicity (Cytotoxicity)% was calculated according to the following formula:

wherein,

flu s: the fluorescence value of the experimental hole (namely, adding cells and adding test sample holes with different concentrations);

flu c: the average value of the fluorescence values of the experimental control wells (namely, cells are added, culture medium is added, and no test sample is added);

flu b: the mean value of fluorescence values of blank wells (i.e., wells with medium alone, without cells and test article).

Data nonlinear fitting was performed using graphpardprism as a curve, fitting mode [ Agonist ]Response- -Variable slope (four parameters), to obtain the EC of the test sample ₅₀ Values.

IMAB362-IgG1 served as positive antibody control.

Fig. 5 is CDC activity of CLDN18.2 antibodies on MC38 cells overexpressing human claudin18.2 according to one embodiment of the application. Table 4 shows CDC activity of the CLDN18.2 antibody on MC38 cells overexpressing human claudin 18.2. As shown in fig. 5 and table 4, antibody P1026 had a significant CDC effect in the presence of complement.

Table 4CLDN18.2 antibody CDC Activity on MC38 cells overexpressing human claudin18.2

Antibody name	EC 50 (μg/mL)	R 2
			IMAB362-IgG1	/	/
P1026-IgG1	0.12	0.99

Example 5 endocytic Activity of anti-CLDN 18.2 antibodies

CHO-S-hCDN18.2 cells were mixed with CDLN18.2 antibody to be tested at a final concentration of 10nM, negative control hIgG1 at 10nM and control IMAB362 antibody (labeled with pHAb dye as antibody above) respectively, incubated at 37℃for 0hr, 1hr, 4hr, 8hr respectively, and flow cytometry was used to collect endocytosis data after different time treatments. The ratio of CLDN18.2 antibodies and hgg 1 binding to CHO-S-hcldn18.2 cell surface expressed CLDN18.2 endocytosed into cells following different time treatments was analyzed and derived using FlowJo X10.0.7. Data were analyzed using GraphPad Prism 7.00 and endocytic curves were drawn.

Fig. 6 is an endocytic activity profile of an anti-CLDN 18.2 antibody P1026 according to an embodiment of the disclosure. As shown in fig. 6, P1026 can exhibit endocytosis more rapidly than IMAB362, with endocytosis within 1 hour, i.e., close to 40, much higher than IMAB362 and Negative Control (NC).

The above embodiments are provided for illustrating the present invention and not for limiting the present invention, and various changes and modifications may be made by one skilled in the relevant art without departing from the scope of the present invention, therefore, all equivalent technical solutions shall fall within the scope of the present disclosure.

Claims (18)

1. An antibody or antigen-binding fragment thereof that specifically binds CLDN18.2, comprising a heavy chain variable region and a light chain variable region, wherein: the heavy chain variable region comprises HCDR1 shown as SEQ ID NO.1, HCDR2 shown as SEQ ID NO.2 and HCDR3 shown as SEQ ID NO. 3; and the light chain variable region comprises LCDR1 as shown in SEQ ID NO.4, LCDR2 as shown in SEQ ID NO.5, and LCDR3 as shown in SEQ ID NO. 6.

2. The antibody or antigen-binding fragment thereof of claim 1, wherein: the heavy chain comprises the variable region shown in SEQ ID NO. 7; and the light chain comprises the variable region shown in SEQ ID NO. 8.

3. The antibody or antigen-binding fragment thereof of claim 1 or 2, wherein the antibody or antigen-binding portion thereof is selected from the group consisting of: whole antibodies, bispecific antibodies, monoclonal antibodies, chimeric antibodies, humanized antibodies, and fully human antibodies.

4. The antibody or antigen-binding fragment thereof of claim 1, further comprising a heavy chain constant region and a light chain constant region, wherein: the antibody heavy chain constant region is selected from the group consisting of IgG series antibodies; the light chain constant region is selected from kappa or lambda chains.

5. The antibody or antigen binding fragment thereof of claim 4, wherein the IgG series antibody is selected from one or more of IgG1, igG2, and IgG 4.

6. The antibody or antigen-binding fragment thereof of claim 1, wherein the antigen-binding fragment is selected from the group consisting of: fab fragments, fab' fragments, F (ab) ₂ Fragments, fv fragments and ScFv.

7. The antibody or antigen binding fragment thereof of claim 1, wherein the CLDN18.2 is selected from the group consisting of: human CLDN18.2, mouse CLDN18.2 and monkey CLDN18.2.

8. A fusion protein comprising an antibody or antigen-binding fragment thereof according to any one of claims 1-7.

9. One or more isolated nucleic acid molecules encoding an antibody or antigen-binding fragment thereof according to any one of claims 1-7, or a fusion protein according to claim 8.

10. One or more vectors comprising one or more isolated nucleic acid molecules according to claim 9.

11. A cell comprising one or more isolated nucleic acid molecules according to claim 9 or one or more vectors according to claim 10.

12. The cell of claim 11, further being a CAR-T or CAR-NK cell comprising one or more isolated nucleic acid molecules according to claim 9 or one or more vectors according to claim 10.

13. A method for producing an antibody or antigen-binding fragment thereof according to any one of claims 1-7 or a fusion protein according to claim 8, comprising culturing a cell according to claim 11 or 12 under conditions that enable expression of the antibody or antigen-binding fragment thereof according to any one of claims 1-7 or the fusion protein according to claim 8.

14. A composition comprising an antibody or antigen-binding fragment thereof according to any one of claims 1-7, a fusion protein according to claim 8, one or more isolated nucleic acid molecules according to claim 9, one or more vectors according to claim 10 and/or cells according to claim 11 or 12, and optionally a pharmaceutically acceptable excipient.

15. Use of an antibody or antigen-binding fragment thereof according to any one of claims 1-7, a fusion protein according to claim 8, one or more isolated nucleic acid molecules according to claim 9, one or more vectors according to claim 10 and/or a cell according to claim 11 or 12 for the preparation of a medicament for the treatment of cancer or a tumor; wherein the cancer or tumor is a CLDN18.2 expression positive cancer or tumor; wherein the cancer or tumor is selected from ovarian cancer, lung cancer, gastric cancer, pancreatic cancer, and esophageal cancer.

16. The use of claim 15, wherein the medicament is a cytotherapeutic medicament.

17. Use of an antibody or antigen-binding fragment thereof according to any one of claims 1-7, or a fusion protein according to claim 8, in the preparation of a reagent for determining the presence and/or amount of CLDN18.2 in a sample.

18. A pharmaceutical composition comprising: an antibody or antigen binding fragment thereof according to any one of claims 1-7, a fusion protein according to claim 8, one or more isolated nucleic acid molecules according to claim 9 or one or more vectors according to claim 10 and/or cells according to claim 11 or 12.