Anti-human claudin-18.2 antibodies for in vitro diagnostics

Abstract

The disclosure provides binding agents (e.g., antibodies) against a human Claudin-18.2 protein, as well as kits and methods for using the same (e.g., immunoassays) as part of a companion diagnostic and for other applications. In some aspects, the binding agents described herein may be used in assays for detecting, e.g., a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian carcer, a lung cancer, or an esophageal cancer.

Description

20240028-02_039062.00183ANTI-HUMAN CLAUDIN-18.2 ANTIBODIES FOR IN VITRO DIAGNOSTICSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority to U.S. Provisional Application No. 63 / 717,049, filed November 6, 2024, the content of which is hereby incorporated by reference in its entirety.SEQUENCE LISTING

[0002] The present application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on November 3, 2025, is named 039062.00183_ST26. xml and is 44,662 bytes in size.TECHNICAL FIELD

[0003] This invention generally relates to binding agents (e.g., antibodies), as well as kits and methods for using the same (e.g., immunoassays) as part of a companion diagnostic and for other applications.BACKGROUND

[0004] Cancer is the second leading cause of mortality worldwide, and the global burden is expected to rise to 29 million new cancer cases by 2040. Tight junction proteins are frequently dysfunctional or modified in several types of cancer cells, and their controlled paracellular permeation and polarity are lost in tumor cells. Tight junction proteins modulate cytoskeletal elements and signaling molecules bound to these proteins, leading to the loss of regulated cell migration and proliferation. “Claudin-18.2” (GenBank Accession No. NP 001002026.1; SEQ ID NO: 1), a 261 amino acid isoform of Claudin-18, is a member of the tight junction protein family. It is a highly selective marker protein expressed only in differentiated gastric mucosal membrane epithelial cells, with very limited expression in20240028-02_039062.00183 normal healthy tissues and no expression in undifferentiated gastric stem cells. There is evidence that abnormal Claudin-18.2 expression throughout the manifestation and growth of several primary malignant tumors, such as gastric cancer / gastroesophageal junction (GC / GEJ) cancer, liver cancer, head and neck cancer, breast cancer, colon cancer, bronchial cancer, and non-small-cell lung cancer. With its distinct pattern of expression, Claudin-18.2 has emerged as a unique molecule for targeted therapy for several cancers, particularly in gastric cancer (“GC”), which is currently the third most common and deadliest cancer globally, with poor prognosis, a high rate of recurrence and metastasis.BRIEF SUMMARY OF THE DISCLOSURE

[0005] Antibodies and other binding agents specific for Claudin-18.2 are commercially available. However, there remains a need in the art for additional high affinity Claudin-18.2- binding agents. In alternative embodiments, provided herein are chimeric or recombinant antibodies (Abs), or an antigen (Ag) binding fragments thereof, or a monomeric or dimeric antigen binding protein, capable of specifically binding to a human Claudin-18.2 polypeptide, or a fragment thereof, including human Claudin-18.2 polypeptides (or fragments thereof) expressed on the surface of tumor cells (e.g., tumor cells, including breast cancers, colon cancers, gastric cancers, gliomas, liver cancers, non-small cell lung cancers, melanomas, myelomas, pancreatic cancers and prostate cancers).

[0006] In a first general aspect, the disclosure provides a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigenbinding protein, capable of specifically binding to isoform 2 of a human Claudin-18 polypeptide (Claudin-18.2) having an amino acid sequence comprising or consisting of SEQ ID NO: 1, or a fragment thereof.

[0007] In some aspects, the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of claim 1, fabricated as20240028-02_039062.00183 or in the form of: an antigen-binding fragment, a F(ab')2, a Fab', a single-chain variable fragment (“scFv”), a (scFv)2, a minibody, a diabody, or a tetrabody.

[0008] In some aspects, the sequence of the heavy chain variable domain comprises SEQ ID NO: 8, 24, or 38, or any contiguous fragment thereof. In some aspects, a fragment may comprise at least, 10, 15, 20, 25, 30, 35, 40 or 50 amino acids, or a length within a range with endpoints selected from any pair of the foregoing lengths. The heavy chain variable domain, or the fragment thereof, may further comprise one or more amino acid substitutions compared to SEQ ID NO: 8, 24, or 38.

[0009] In some aspects, the sequence of the light chain variable domain comprises SEQ ID NO: 9, 25, or 39, or any contiguous fragment thereof. In some aspects, a fragment may comprise at least, 10, 15, 20, 25, 30, 35, 40 or 50 amino acids, or a length within a range with endpoints selected from any pair of the foregoing lengths. The heavy chain variable domain, or the fragment thereof, may further comprise one or more amino acid substitutions compared to SEQ ID NO: 9, 25, or 39.

[0010] In some aspects, the sequence of the heavy chain variable domain is SEQ ID NO: 8, and the sequence of the light chain variable domain is SEQ ID NO: 9; or the sequence of the heavy chain variable domain is SEQ ID NO: 24, and the sequence of the light chain variable domain is SEQ ID NO: 25; or the sequence of the heavy chain variable domain is SEQ ID NO: 38, and the sequence of the light chain variable domain is SEQ ID NO: 39.

[0011] In some aspects, the amino acid sequence of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, further comprises: (a) a heavy chain variable domain and a constant domain having any one of SEQ ID NOs: 14, 28, or 42; (b) a heavy chain signal peptide having SEQ ID NO: 12; (c) a heavy chain variable domain and a signal peptide sequence having any one of SEQ ID NOs: 16, o 30, or 44; (d) a heavy chain variable domain and a constant domain and a signal peptide sequence20240028-02_039062.00183 having any one of SEQ ID NOs: 10, 26, or 40; (e) a light chain variable domain and a constant domain having any one of SEQ ID NOs: 15, 29, or 43; (f) a light chain signal peptide having SEQ ID NO: 13; (g) a light chain variable domain and signal peptide sequence having any one of SEQ ID NOs: 17, 31, or 45; (h) a light chain variable domain and a constant domain and a signal peptide sequence having any one of SEQ ID NOs: 11, 27, or 41; (i) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 2, 3, or 4; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 2, 3, 4, optionally wherein the one or more substitutions are conservative substitutions; (j) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 5, 6, or 7; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 5, 6, or 7, optionally wherein the one or more substitutions are conservative substitutions; (k) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 18, 19, or 20; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 18, 19, or 20, optionally wherein the one or more substitutions are conservative substitutions; (1) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 21, 22, or 23; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 21, 22, or 23, optionally wherein the one or more substitutions are conservative substitutions; (m) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 32, 33, or 34; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 32, 33, or 34, optionally20240028-02_039062.00183 wherein the one or more substitutions are conservative substitutions; and / or (n) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 35, 36, or 37; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 35, 36, or 37, optionally wherein the one or more substitutions are conservative substitutions.

[0012] In some aspects, the sequence of the heavy chain variable domain comprises SEQ ID NO: 8, 24, or 38 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the heavy chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a light chain variable domain.

[0013] In some aspects, the sequence of the light chain variable domain comprises SEQ ID NO: 9, 25, or 39 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the light chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a heavy chain variable domain.

[0014] In some aspects, the sequence of the heavy chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs: 8, 24, or 38.

[0015] In some aspects, the sequence of the light chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs: 9, 25, or 39.20240028-02_039062.00183

[0016] In some aspects, the sequence of the heavy chain variable domain and the amino acid sequence of SEQ ID NOs: 8, 24, or 38 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment.

[0017] In some aspects, the sequence of the light chain variable domain and the amino acid sequence of SEQ ID NOs: 9, 25, or 39 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment.

[0018] In some aspects, the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, comprises three complementarity determining regions (CDRs), wherein the CDRs are selected from the CDRs of any one of SEQ ID NOs: 8, 24, or 38.

[0019] In some aspects, the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, comprises three complementarity determining regions (CDRs), wherein the CDRs are selected from the CDRs of any one of SEQ ID NOs: 9, 25, or 39.

[0020] In some aspects, the antibody heavy chain is an IgM, IgG, IgA or IgE isotype heavy chain, and / or the light chain is a kappa or a lambda light chain.

[0021] In some aspects, the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, further comprises, or is bound to or covalently conjugated to, a detectable agent or a binding moiety. In some aspects, the detectable agent comprises: an enzyme, a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7- methoxycoumarin (Mca), dabcyl, [2-(4-nitro-2,l,3-benzoxadiazol-7- yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron-dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten or an antibody binding epitope or domain. In some aspects, the20240028-02_039062.00183 enzyme is a peroxidase, an alkaline phosphatase, or a beta-galactosidase. In some aspects, the peroxidase is a horse radish peroxidase (HRP). In some aspects, the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine. In some aspects, the dye comprises a cyanine dye; or Cy3 or Cy5. In some aspects, the fluorophore comprises dansyl, fluorescein or carboxyfluorescein (FAM) or 6-FAM. In some aspects, the binding moiety comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein.

[0022] In a second general aspect, the disclosure provides a recombinant nucleic acid molecule encoding a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any of the aspects described herein.

[0023] In some aspects, the recombinant nucleic acid further comprises and is operatively linked to a transcriptional regulatory element. In some aspects, the transcriptional regulatory element comprises a promoter. In some aspects, the promoter is an inducible promoter or a constitutive promoter.

[0024] In some aspects, the recombinant nucleic acid further comprises a sequence encoding an additional protein or peptide moiety or domain. In some aspects, the additional protein or peptide moiety or domain comprises a purification moiety or domain to aid in the purification or isolation of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, encoded by the recombinant nucleic acid. In some aspects, the additional protein or peptide moiety or domain comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein.20240028-02_039062.00183

[0025] In some aspects, the recombinant nucleic acid further comprises a sequence encoding a protease cleavage site positioned between the purification moiety or domain and the sequence encoding the chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein.

[0026] In a third general aspect, the disclosure provides an expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid comprising a recombinant nucleic acid molecule according to any of the aspects described herein.

[0027] In a fourth general aspect, the disclosure provides a cell comprising a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any of the aspects described herein, a recombinant nucleic acid molecule according to any of the aspects described herein, or an expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid according to any of the aspects described herein. In some aspects, the cell is a bacterial, fungal, mammalian, yeast, insect, avian or plant cell.

[0028] In a fifth general aspect, the disclosure provides a method for generating a polyclonal antibody, or for generating a polyclonal immune serum, that is specific for or specifically binds to isoform 2 of a human Claudin-18 polypeptide (i.e., Claudin-18.2), the method comprising administering to or immunizing a mammal or an avian species with a peptide or polypeptide, or an epitope, comprising the amino acid sequence of SEQ ID NO: 1, or a fragment thereof

[0029] In a sixth general aspect, the disclosure provides a method for detecting the presence of isoform 2 of a human Claudin-18 polypeptide (i.e., Claudin-18.2) in a cell, a tissue, an organ, or a portion thereof, comprising: (a) contacting the cell, tissue, organ, or portion thereof with a chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein according to any of the aspects described herein, or encoded20240028-02_039062.00183 by a recombinant nucleic acid molecule according to any of the aspects described herein, and (b) detecting the specific binding of the chimeric or recombinant antibody (Ab), or antigenbinding fragment thereof, or monomeric or dimeric antigen-binding protein, with a human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, in the cell, tissue, organ, or portion thereof. In some aspects, contacting comprises use of an immunohistochemistry (IHC) assay.

[0030] In some aspects, the method further comprises contacting the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein with a detectable agent to indicate or signal the specific binding of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein to the human Claudin-18.2 polypeptide or the fragment thereof.

[0031] In some aspects of the methods described herein, the detectable agent specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein. In some aspects, the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein which is bound to the human Claudin-18.2 polypeptide. In some aspects, the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to a hapten or tag attached or conjugated to the chimeric or recombinant antibody (Ab) or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein. In some aspects, the antibody or an antigen-binding fragment or the secondary antibody further comprises or has attached or conjugated thereto a second detectable agent or an enzyme. In some aspects, the enzyme is an alkaline phosphatase, a beta-galactosidase or a peroxidase.20240028-02_039062.00183

[0032] In some aspects of the methods described herein, the antibody or an antigen-binding fragment or the secondary antibody further comprises or has attached or conjugated thereto a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7-m ethoxy coumarin (Mca), dabcyl, [2-(4-nitro- 2,l,3-benzoxadiazol-7-yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron- dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten. In some aspects, the dye comprises a cyanine dye, or Cy3 or Cy5. In some aspects, the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine.

[0033] In a seventh general aspect, the disclosure provides a method for diagnosing a human cancerthat expresses isoform 2 of Claudin-18 (i.e., Claudin 18.2), comprising: detecting the expression or presence of a Claudin-18.2 polypeptide or fragment thereof, in a cell, tissue, or organ sample, or a portion thereof, by contacting the cell, tissue, organ sample, or portion thereof with a chimeric or recombinant antibody or antigen-binding fragment thereof according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule according to any of the aspects described herein, and detecting whether or not the chimeric or recombinant antibody specifically binds to the human Claudin- 18.2 polypeptide or fragment thereof in the cell, tissue, organ sample, or portion thereof, wherein the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue, or organ sample, or the portion thereof. In some aspects, the cell is (i) a differentiated epithelial cell, optionally from gastric mucosa or (ii) a tumor cell, optionally derived from a gastrointestinal epithelial cell. In some aspects, the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue or organ sample, or portion thereof, thereby diagnosing the cancer. In some aspects, the cancer is a) selected from the group consisting of: a pancreatic20240028-02_039062.00183 cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; or b) a solid tumor. In some aspects, the cancer is an adenocarcinoma. In some aspects, the detection comprises using or conducting an immunohistochemistry (IHC) assay or a flow cytometry. In some aspects, the conducting or using of the flow cytometry comprises use of a fluorescence-activated cell sorter (FACS) or an impedance flow cytometer. In some aspects, the cell, tissue, organ sample, or portion thereof is or is derived from a biopsy from a patient.

[0034] In an eighth general aspect, the disclosure provides a method for treating, ameliorating or preventing a cancer comprising first detecting or diagnosing the cancer in an individual in need thereof using a method of any of the methods described herein, followed by treatment of the individual in need thereof. In some aspects, the cancer to be treated is a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; b) a solid tumor; and / or c) an adenocarcinoma.

[0035] In a ninth general aspect, the disclosure provides use of a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigenbinding protein according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule of any of the aspects described herein, for detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer, e.g., a cancer a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; b) a solid tumor; and / or c) an adenocarcinoma.

[0036] In a tenth general aspect, the disclosure provides a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigenbinding protein according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule of any of the aspects described herein, for use in detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer, e.g., a cancer a) selected from the20240028-02_039062.00183 group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; b) a solid tumor; and / or c) an adenocarcinoma.

[0037] In an eleventh general aspect, the disclosure provides a kit comprising a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule of any of the aspects described herein. In some aspects, the kit further comprises components needed for an immunohistochemistry (IHC) assay. In some aspects, the kit further comprises instructions for practicing any of the methods described herein. In some aspects, the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or dimeric antigen-binding protein, included in the kit, is substantially purified or isolated.

[0038] In a twelfth general aspect, the disclosure provides a product of manufacture comprising a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule of any of the aspects described herein. In some aspects, the product of manufacture comprises or is fabricated as or manufactured as a slide, a well, a chip, a biochip, an array, a tray, a dish or a microtiter plate or dish. In some aspects, the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or dimeric antigen-binding protein, is substantially purified or isolated, or is in the form of an unpurified or partially purified culture supernatant.

[0039] In a thirteenth general aspect, the disclosure provides a phage or a phagemid comprising or expressing on its surface a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any of the aspects described herein, or encoded by a recombinant nucleic acid molecule of any of the aspects described herein.20240028-02_039062.00183

[0040] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.DETAILED DESCRIPTION

[0041] In alternative embodiments, provided are chimeric or a recombinant antibodies (Ab), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, that can specifically bind to a human Claudin-18.2 polypeptide (SEQ ID NO: 1) or a fragment thereof. In alternative embodiments, provided are products of manufacture and kits comprising the chimeric or a recombinant Abs, or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, as provided herein, or nucleic acid molecules encoding them, and methods for making and using them. In alternative embodiments, chimeric or a recombinant antibodies (Ab), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins as provided herein are used for in vitro diagnostics, for example, by immuno-histochemistry (IHC), for example, in IHC protocols to diagnose, detect and / or treat a cancer, for example a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer, or a solid tumor or adenocarcinoma as a general class, by their ability to specifically bind to Claudin-18.2 on (or expressed by) one or more cancer cells. Thus, the chimeric or a recombinant antibodies (Abs), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, as provided herein, can be used as a companion diagnostic for the diagnosis and treatment of cancer by specifically staining cancer cells. In some aspects, the chimeric or a recombinant antibodies (Abs), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, as20240028-02_039062.00183 provided herein, specifically bind to a Claudin-18.2 protein expressed by or on (i) a differentiated epithelial cell, optionally from gastric mucosa or (ii) a tumor cell, optionally derived from a gastrointestinal epithelial cell. In some aspects, the chimeric or a recombinant antibodies (Abs), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, as provided herein, specifically bind to a Claudin-18.2 protein, as opposed to other isoforms of this protein (e.g., isoform 1).

[0042] Expression of Recombinant Chimeric Antibodies

[0043] In alternative embodiments, chimeric and / or recombinant antibodies (Abs), the antigen binding fragments thereof, or the monomeric or dimeric antigen binding proteins are provided herein, including exemplary chimeric or recombinant anti-human Claudin-18.2 Abs comprising the heavy chain variable domain of any one of SEQ ID NOs: 8, 24, and 38; and / or the light chain variable domain of any one of SEQ ID NOs: 9, 25, or 39, with or without a signal peptide, can be expressed as a recombinant Ab using, for example, a plasmid or any expression vehicle encoding the respective heavy and light chains, or the heavy chain and the light chain can be encoded in separate expression vehicles.

[0044] In some embodiments, the heavy and light chains can be (cis- or trans-) expressed from any plasmid, cosmid, recombinant virus or equivalent vector, for example, from apTT5™ vector(s) (National Research Council Canada, NRC-CNRC, Canada) or equivalents.

[0045] In alternative embodiments, the expression vehicles (such as a plasmid) containing exemplary Ab-encoding nucleic acid(s) as provided herein are expressed in in vitro expression systems or are expressed in cultured tissues, cells or organoids, which can be a bacterial, fungal, mammalian, yeast, insect or plant cell expression systems, or hybrid or synthetic expression system. For example, exemplary Ab-encoding nucleic acid(s) can be expressed in a human embryonic kidney (HEK) cell such as an HEK293- 6E cell. In alternative embodiment, the vector or vectors expressing exemplary Ab- encoding nucleic acid(s), for example, exemplary20240028-02_039062.00183 heavy and / or light chains, are episomal or are chromosomally integrated, for example, in a stable cell line capable of synthesizing, optionally inducibly synthesizing, the heavy and / or light chains.

[0046] In alternative embodiments, provided are nucleic acid molecules encoding chimeric or recombinant Abs as provided herein. Nucleic acid molecules as provided herein can be made, isolated and / or manipulated by, for example, cloning and expression of cDNA libraries, amplification of message or genomic DNA by PCR, and the like. Nucleic acid molecules used to practice embodiments as provided herein, whether RNA, cDNA, genomic DNA, vectors, viruses or hybrids thereof, may be isolated from a variety of sources, genetically engineered, amplified, and / or expressed / generated recombinantly. Recombinant polypeptides generated from these nucleic acid molecules can be individually isolated or cloned and tested for a desired activity. Any recombinant expression system can be used, including bacterial, fungal, mammalian, yeast, insect or plant cell expression systems, or hybrid or synthetic expression systems.

[0047] Alternatively, these nucleic acid molecules can be synthesized in vitro by well- known chemical synthesis techniques, as described in, for example, Martin et al, ACS Synth. Biol. (2017) 6, 7, 1370-1379; Adams (1983) J. Am. Chem. Soc. 105:661; Belousov (1997) Nucleic Acid Res. 25:3440-3444; Frenkel (1995) Free Radic. Biol. Med. 19:373- 380; Blommers (1994) Biochemistry 33:7886-7896; Narang (1979) Meth. Enzymol. 68:90; Brown (1979) Meth. Enzymol. 68: 109; Beaucage (1981) Tetra. Lett. 22: 1859; U.S. Patent No. 4,458,066.

[0048] Techniques for the manipulation of nucleic acid molecules, such as, for example, subcloning, labeling probes (for example, random-primer labeling using Klenow polymerase, nick translation, amplification), sequencing, hybridization and the like are well described in the scientific and patent literature, see, for example, Sambrook, ed., Molecular Cloning: A20240028-02_039062.00183Laboratory Manual (2ndEd.), Vols. 1-3, Cold Spring Harbor Laboratory, (1989); Current Protocols In Molecular Biology, Ausubel, ed. John Wiley & Sons, Inc., New York (1997); Laboratory Techniques In Biochemistry And Molecular Biology. Hybridization With Nucleic Acid Probes, Part I. Theory and Nucleic Acid Preparation, Tijssen, ed. Elsevier, N.Y. (1993).

[0049] Another useful means of obtaining and manipulating nucleic acid molecules used to practice embodiments as provided herein comprises screening and re-cloning inserts isolated or amplified from, for example, genomic clones or cDNA clones. Sources of nucleic acid molecules include recombinant nucleic acid sequences, genomic or cDNA libraries contained and / or expressed in, for example, mammalian artificial chromosomes (MACs), see, for example, U.S. Patent Nos. 5,721,118; 6,025,155; human artificial chromosomes, see, for example, Rosenfeld (1997) Nat. Genet. 15:333-335; yeast artificial chromosomes (YAC); bacterial artificial chromosomes (BAC); Pl artificial chromosomes, see, for example, Woon (1998) Genomics 50:306-316; Pl-derived vectors (PACs), see, for example, Kern (1997) Biotechniques 23: 120-124; cosmids, recombinant viruses, phages or plasmids.

[0050] In alternative embodiments, nucleic acid molecules as provided herein are operably linked to transcriptional regulatory elements, including promoters, with can be constitutive or inducible transcriptional regulatory elements.

[0051] In alternative aspects, provided are “expression cassettes” comprising a nucleotide sequence as provided herein, for example encoding a chimeric or recombinant antibody as provided herein. Expression cassettes can include at least a transcriptional regulatory element, for example, a promoter, operably linked with an antibody coding sequence, and optionally can also include transcription termination signals. Additional factors necessary or helpful in effecting expression may also be used, for example, enhancers.

[0052] In alternative aspects, expression cassettes used to practice embodiments as provided herein include plasmids, expression vectors, recombinant viruses, any form of20240028-02_039062.00183 recombinant “naked DNA” vector, and the like. In alternative aspects, a “vector” used to practice embodiments as provided herein can comprise a nucleic acid molecule that can infect, transfect, transiently or permanently transduce a cell. In alternative aspects, a vector used to practice embodiments as provided herein can be a naked nucleic acid molecule, or a nucleic acid molecule complexed with protein or lipid. In alternative aspects, vectors used to practice embodiments as provided herein can comprise viral or bacterial nucleic acid molecules and / or proteins, and / or membranes (for example, a cell membrane, a viral lipid envelope, etc.).

[0053] In alternative aspects, vectors used to practice embodiments as provided herein can include, but are not limited to replicons (for example, RNA replicons, bacteriophages) to which fragments of DNA may be attached and become replicated. Vectors thus include, but are not limited to RNA, autonomous self-replicating circular or linear DNA or RNA (for example, plasmids, viruses, and the like, see, for example, U.S. Patent No. 5,217,879), and can include both the expression and non-expression plasmids. In alternative aspects, the vector used to practice embodiments as provided herein can be stably replicated by the cells during mitosis as an autonomous structure, or can be incorporated within the host’s genome.

[0054] In alternative aspects, “promoters” used to practice embodiments as provided herein include all sequences capable of driving transcription of a coding sequence in a cell, for example, a bacterial, yeast, fungal, plant, insect (for example, baculovirus) or mammalian cell. Thus, promoters used in the constructs include c / .s-acting transcriptional control elements and regulatory sequences that are involved in regulating or modulating the timing and / or rate of transcription of a gene. For example, a promoter used to practice embodiments as provided herein can be a c / .s-acting transcriptional control element, including an enhancer, a promoter, a transcription terminator, an origin of replication, a chromosomal integration sequence, 5' and 3' untranslated regions, or an intronic sequence, which are involved in transcriptional20240028-02_039062.00183 regulation. These cis-acting sequences can interact with proteins or other biomolecules to carry out (turn on / off, regulate, modulate, etc.) transcription.

[0055] Constitutive” promoters used to practice embodiments as provided herein can be those that drive expression continuously under most environmental conditions and states of development or cell differentiation. “Inducible” or “regulatable” promoters used to practice embodiments as provided herein can direct expression of a nucleic acid sequence as provided herein under the influence of environmental conditions or developmental conditions. Examples of environmental conditions that may affect transcription by inducible promoters used to practice embodiments as provided herein include the presence of an inducing factor administered to a cell.

[0056] In alternative embodiments, antibodies used to practice embodiments as provided herein can comprise any “mimetic” and / or “peptidomimetic” form. In alternative embodiments, peptides and polypeptides used to practice embodiments as provided herein can comprise synthetic chemical compounds which have substantially the same structural and / or functional characteristics of the natural polypeptide, for example, a chimeric or recombinant antibody as provided herein. The mimetic used to practice embodiments as provided herein can be either entirely composed of synthetic, non- natural analogues of amino acids, or, is a chimeric molecule of partly natural peptide amino acids and partly non-natural analogs of amino acids. The mimetic can also incorporate any amount of natural amino acid conservative substitutions as long as such substitutions also do not substantially alter the mimetic’s structure and / or activity. Routine experimentation will determine whether a mimetic is effective for practicing the invention, for example, if a mimetic composition is effective in specifically binding to a human Claudin-18.2 polypeptide. Methodologies detailed herein and others known to persons skilled in the art may be used to select or guide one to choose effective mimetic for practicing the compositions and / or methods as provided herein.20240028-02_039062.00183

[0057] Polypeptide mimetic compositions for practicing embodiments as provided herein can comprise any combination of non-natural structural components. In alternative aspects, mimetic compositions for practicing embodiments as provided herein can comprise one or all of the following three structural groups: a) residue linkage groups other than the natural amide bond (“peptide bond”) linkages; b) non-natural residues in place of naturally occurring amino acid residues; or c) residues which induce secondary structural mimicry, i.e., to induce or stabilize a secondary structure, for example, a beta turn, gamma turn, beta sheet, alpha helix conformation, and the like. For example, a polypeptide can be characterized as a mimetic when all or some of its residues are joined by chemical means other than natural peptide bonds.

[0058] Purification and Isolation of Recombinant Proteins

[0059] In alternative embodiments, chimeric or the recombinant antibodies, antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, are substantially purified or isolated, and optionally the substantially purified or isolated forms are the forms used in immunohistochemistry methodologies and / or as reagents, kits and / or products of manufacture as provided herein.

[0060] In alternative embodiments, chimeric or the recombinant antibodies, antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, are substantially purified or isolated using: physicochemical fractionation, for example, using differential precipitation, size-exclusion or solid-phase binding of immunoglobulins based on size, charge or other shared chemical characteristics of antibodies in typical samples; class-specific affinity, for example, solid-phase binding of particular antibody classes (for example, IgG or IgM) by immobilized biological ligands (for example, proteins, lectins, and the like) that have specific affinity to immunoglobulins, and this can purify all antibodies of the target class without regard to antigen specificity; or antigen- specific affinity, for example, affinity purification of only those antibodies in a sample that bind to a particular antigen molecule through their specific20240028-02_039062.00183 antigen-binding domains, where this purifies all antibodies that bind the antigen without regard to antibody class or isotype.

[0061] In alternative embodiments, chimeric or the recombinant antibodies, antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, are substantially purified or isolated using standard isolation methodologies such as chromatography, for example, Ion Exchange (IEX) Chromatography, Hydrophobic Interaction Chromatography (HIC), countercurrent chromatography, immunoaffinity and / or size exclusion chromatography.

[0062] In alternative embodiments, chimeric or the recombinant antibodies, antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, are generated in bioreactors, for example, a perfusion bioreactor, using continuous expression and purification processes, for example, as described by Vogg et al., in Methods Mol Biol. 2018; vol 1850: 147- 178, or using stirred-tank or rocking bioreactor systems, followed by purification.

[0063] Products of manufacture and Kits

[0064] In some aspects, products of manufacture and kits comprising at least one antihuman Claudin-18.2 Ab, or an antigen-binding fragment thereof, are provided, as well as methods of using the same; optionally, the products of manufacture and kits can further comprise some or all reagents needed to perform an IHC, and optionally can comprise instructions for practicing any of the methods described herein. Such products of manufacture and kits may comprise one or more anti-human Claudin-18.2 Abs disclosed herein (e.g., recombinant or chimeric Abs), or antigen-binding fragments thereof.

[0065] In alternative embodiments, products of manufacture have attached thereto or affixed (optionally covalently bound) on or onto chimeric or a recombinant antibodies (Abs), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins as provided herein, and optionally products of manufacture as provided herein are or comprise arrays, biochips, slides, trays, dishes (for example, microtiter dishes), phages or phagemids.20240028-02_039062.00183

[0066] Immunohistochemistry

[0067] In alternative embodiments, immunohistochemistry methodologies and / or reagents used to practice compositions, products of manufacture, kits or methods as provided herein can include or comprise or comprise use of any IHC protocol, IHC armamentarium, device and / or image or data analysis system, for practicing IHC or IHC reagents known in the art, for example, as described in U.S. patent nos. (USPNs) 10,565,479 (describing methods for identifying blurred areas in digital images of stained tissue); 10,564,076 (describing systems for analytical ( or IHC) sample preparation); 10,551,395 (describing an automated histological staining system); 10,551,378 (describing a tissue staining method); 10,504,224 (describing a digital tissue image analysis system for IHC); 10,501,777 (describing simultaneous, multiplexed detection and quantification of protein expression in IHC); 10,488,340 (describing method for extracting an image of a target fluorophore in a biological material); 10,453,195 (describing methods of detecting tissue areas of interest using digital pathology imaging); 10,438,381 (describing devices, systems and methods for generating a digital image of a tissue section); 10,416,176 (describing methods for processing specimens in an automated histological staining system); 10,393,633 (describing methods for processing and inhibiting the degradation of an IHC sample); 10,217,011 (describing handling of IHC slides); 10,209,165 (describing automated or semi-automated methods for assessing the quality of staining of a specimen containing cells); 10,126,216 (describing methods for fixing tissue samples for IHC); 9,423,322.

[0068] In alternative embodiments, chimeric or the recombinant antibodies, antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins, in IHC protocols, or kits, as provided herein are substantially purified or isolated or are in the form of an unpurified or partially purified culture supernatant.20240028-02_039062.00183

[0069] In alternative embodiments, methods as provided herein can use or comprise reagents for detecting or visualizing an antibody-antigen interaction using any products or methods know in the art, for example, and IHC protocol or reagents.

[0070] In alternative embodiments, methods as provided herein comprise use of chromogenic immunohistochemistry (CIH), wherein a primary antibody (for example, chimeric or a recombinant antibodies (Ab), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins as provided herein) or secondary antibody (for example, where the secondary antibody binds to (the primary antibody) chimeric or a recombinant antibodies (Ab), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins as provided herein after they have specifically bound to, paired with, associated with, or configured with a LAG-3 epitope or polypeptide) is conjugated to an enzyme, such as peroxidase (or immunoperoxidase), for example, a horseradish peroxidase (HRP), that can catalyze a color-producing reaction.

[0071] In alternative embodiments, methods as provided herein comprise use of immunofluorescence, where a primary or a secondary antibody is tagged to a fluorophore, such as fluorescein or fluorescein isothiocyanate (FITC), a triarylmethane dye such as rhodamine or rhodamine derivatives (for example, tetramethylrhodamine (TRITC), rhodamine 6G, rhodamine 123, rhodamine B, carboxytetramethylrhodamine (TAMRA), tetramethylrhodamine (TMR), sulforhodamine 101), aminomethylcoumarin acetate (AMCA), ALEXA™ or DYLIGHT™ fluors. 3,3’-Diaminobenzidine (DAB) also can be used.

[0072] In alternative embodiments, methods as provided herein comprise use of a direct method or one-step staining method where a primary antibody (for example, chimeric or a recombinant antibodies (Ab), or antigen binding fragments thereof, or monomeric or dimeric antigen binding proteins as provided herein) is labeled and reacts directly with an antigen, for20240028-02_039062.00183 example, in a tissue sections. While this technique utilizes only one antibody and therefore is simple and rapid, the sensitivity may be lower due to little signal amplification.

[0073] In alternative embodiments, methods as provided herein comprise use of an indirect method where an unlabeled primary antibody (first layer) binds to a target antigen (human Claudin-18.2, or a fragment thereof), for example, in a tissue or organ, and a labeled secondary antibody (second layer) then is reacted with the primary antibody. The secondary antibody can be against the isotype, for example, IgG, of the animal species in which the primary antibody is derived. This method can be more sensitive than direct detection strategies because of signal amplification due to the binding of several secondary antibodies to each primary antibody if the secondary antibody is conjugated to a detecting agent such as a fluorescent or enzyme reporter.

[0074] In alternative embodiments, further amplification is achieved if the secondary antibody is conjugated to several detecting molecules, for example, biotin molecules, which can recruit complexes of avidin-, streptavidin- or NEUTRA VIDIN™ protein- bound enzyme.

[0075] In alternative embodiments, the IHC is performed on tissue sections or tissue biopsies, for example, paraformaldehyde (PF A) fixed tissues or organs, or formalin-fixed paraffin-embedded tissues. In alternative embodiments, a tissue is sliced or used whole. Before sectioning, the tissue sample can be embedded in a medium, for example, paraffin wax or cryomedia. Tissue sections can be sliced on a variety of instruments, most commonly using a microtome, cryostat, or vibratome. Specimens can be sliced at a range of about 3 pm to 5 urn. The slices can be mounted on slides, dehydrated using alcohol washes of increasing concentrations (for example, 50%, 75%, 90%, 95%, 100%), and cleared using a detergent like xylene before being imaged under a microscope.

[0076] Depending on the method of fixation and tissue preservation, the sample may require additional steps to make the Claudin-18.2 epitopes available for antibody binding,20240028-02_039062.00183 including deparaffinization and antigen retrieval. For formalin-fixed paraffin-embedded tissues, antigen-retrieval is often necessary, and can comprise pre-treating the sections with heat or proteases.

[0077] In alternative embodiments, the IHC is performed using an ENVISION DUOFLEX DOUBLESTAIN SYSTEM™ (EnVision DuoFLEX Doublestain System) (Agilent, San Jose, CA), which allows for staining of two or more markers on a single slide. In alternative embodiments, the IHC is performed using an EnVision FLEX HRP Magenta, High pH (Dako Omnis) system, and binding can be visualized by EnVision FLEX HRP Magenta Chromogen. In alternative embodiments, the IHC is performed using EnVision FLEX Mini Kit, High pH, which is a high-sensitivity visualization system intended for use in IHC together with Dako AUTOSTAINER™ instruments; this dual link system detects primary mouse and rabbit antibodies and the reaction is visualized by 3,3’-Diaminobenzidine (DAB) chromogen (DAB forms a water-insoluble brown precipitate when oxidized, for example, by a peroxidase).

[0078] Methods of Use

[0079] In some aspects, the Claudin-18.2 antibodies (or antigen-binding fragments thereof), as well as the kits and products of manufacture comprising the same, described herein, may be used in clinical or diagnostic applications. For example, a Claudin-18.2 antibody, or antigen-binding fragment thereof, may be used to detect a Claudin-18.2 polypeptide via an in vitro IHC assay in order to determine whether a subject has a cancer or other disease, or is likely to develop cancer or a disease. Potential applications included, e.g., use as a companion diagnostic to identify patients that could benefit from a Claudin-18.2-targeting antibody-drug conjugate (ADC) therapy. Potential indications, include without limitation, pancreatic cancer, gastric cancer, colo-rectal cancer, ovarian career, lung cancer (e.g., non-small cell lung cancer), or esophageal cancer, as well as adenocarcinoma and solid tumors, respectively, as a general class.20240028-02_039062.00183

[0080] Exemplary aspects of the disclosure.1. A chimeric or a recombinant antibody (“Ab”), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein, capable of specifically binding to isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”) having an amino acid sequence comprising or consisting of SEQ ID NO: 1, or a fragment thereof.2. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 1, fabricated as or in the form of: an antigen-binding fragment, a F(ab')2, a Fab', a single-chain variable fragment (“scFv”), a (SCFV)2, a minibody, a diabody, or a tetrabody.3. The chimeric or recombinant antibody (Ab), or antigen-binding-fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 1 or aspect 2, wherein the sequence of the heavy chain variable domain is:QSVEESGGRLVTPGTPLTLTCTVSGFSLSYYNMAWVRQAPGKGLEWIGGIATVGTTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYFLNLWGQGTLVTVSS (SEQ ID NO: 8),QSVEESGGRLVTPGTPLTLTCTVSGFSLSRYNMAWVRQAPGKGLEWIGGIATVGSTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYLLNLWGQGTLVTVSS (SEQ ID NO: 24), or20240028-02_039062.00183QSVEESGGRLVTPGTPLTLTCTASGFSLSKHDMNWVRQAPGKGLEYIGFISYGGSAY YARWAKGRFI ISKTSTTVDLKI ISPTTEDTATYFCARSGI ITLTLWGQGTLVTVSS(SEQ ID NO: 38).4. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 3, wherein the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYNNNYLSWFQQKPGQPPKLLIYGASTLASGVPSRFKGSGSGTQLTLTISDVQCVDAATYYCAGGYSSTIDARAFGGGTEVWK(SEQ ID NO: 9),AQVLTQTPSSVSAAVGGTVTINCQSSQSVYSHNYLSWYQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQFTLTISDVQCDDAATYYCAGGYSSS IDARAFGGGTEVWK(SEQ ID NO: 25), orAAVLTQTPSSTSAAVGGTVTINCQSSQSVYSNNYLSWYQQKPGQPPKLLIYKASTLA SGVPSRFRGSGSGTQFTLTINDLECDDAATYFCAGGYSSSGDITDNAFGGGTEVWK(SEQ ID NO: 39).5. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 4, wherein the sequence of the heavy chain variable domain is:QSVEESGGRLVTPGTPLTLTCTVSGFSLSYYNMAWVRQAPGKGLEWIGGIATVGTTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYFLNLWGQGTLVTVSS (SEQ ID NO: 8), and the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYNNNYLSWFQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQLTLTISDVQCVDAATYYCAGGYSSTIDARAFGGGTEVWK (SEQ ID NO: 9); or the sequence of the heavy chain variable domain is:20240028-02_039062.00183QSVEESGGRLVTPGTPLTLTCTVSGFSLSRYNMAWVRQAPGKGLEWIGGIATVGSTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYLLNLWGQGTLVTVSS (SEQ ID NO: 24), and the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYSHNYLSWYQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQFTLTISDVQCDDAATYYCAGGYSSS IDARAFGGGTEVWK (SEQ ID NO: 25); or the sequence of the heavy chain variable domain isQSVEESGGRLVTPGTPLTLTCTASGFSLSKHDMNWVRQAPGKGLEYIGFISYGGSAY YARWAKGREI ISKTSTTVDLKI ISPTTEDTATYFCARSGI ITLTLWGQGTLVTVSS (SEQ ID NO: 38), and the sequence of the light chain variable domain is:AAVLTQTPSSTSAAVGGTVTINCQSSQSVYSNNYLSWYQQKPGQPPKLLIYKASTLA SGVPSRFRGSGSGTQFTLTINDLECDDAATYFCAGGYSSSGDITDNAFGGGTEVWK (SEQ ID NO: 39).6. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 5, having an amino acid sequence further comprising:(a) a heavy chain variable domain and a constant domain having any one of SEQ ID NOs: 14, 28, or 42;(b) a heavy chain signal peptide having SEQ ID NO: 12;(c) a heavy chain variable domain and a signal peptide sequence having any one of SEQ ID NOs: 16, o 30, or 44;(d) a heavy chain variable domain and a constant domain and a signal peptide sequence having any one of SEQ ID NOs: 10, 26, or 40;(e) a light chain variable domain and a constant domain having any one of SEQ ID NOs: 15, 29, or 43;20240028-02_039062.00183(f) a light chain signal peptide having SEQ ID NO: 13;(g) a light chain variable domain and signal peptide sequence having any one of SEQ ID NOs: 17, 31, or 45;(h) a light chain variable domain and a constant domain and a signal peptide sequence having any one of SEQ ID NOs: 11, 27, or 41;(i) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 2, 3, or 4; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 2, 3, 4, optionally wherein the one or more substitutions are conservative substitutions;(j) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 5, 6, or 7; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 5, 6, or 7, optionally wherein the one or more substitutions are conservative substitutions;(k) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 18, 19, or 20; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 18, 19, or 20, optionally wherein the one or more substitutions are conservative substitutions;(l) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 21, 22, or 23; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 21, 22, or 23, optionally wherein the one or more substitutions are conservative substitutions;20240028-02_039062.00183(m) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 32, 33, or 34; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 32, 33, or 34, optionally wherein the one or more substitutions are conservative substitutions; and / or(n) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 35, 36, or 37; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 35, 36, or 37, optionally wherein the one or more substitutions are conservative substitutions.7. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 6, wherein the sequence of the heavy chain variable domain comprises SEQ ID NO: 8, 24, or 38 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the heavy chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a light chain variable domain.8. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 7, wherein the sequence of the light chain variable domain comprises SEQ ID NO: 9, 25, or 39 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the light chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a heavy chain variable domain.20240028-02_039062.001839. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 8, wherein the sequence of the heavy chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs: 8, 24, or 38.10. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 9, wherein the sequence of the light chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs: 9, 25, or 39.11. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 10, wherein the sequence of the heavy chain variable domain and the amino acid sequence of SEQ ID NOs:8, 24, or 38 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment.12. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 11, wherein the sequence of the light chain variable domain and the amino acid sequence of SEQ ID NOs:9, 25, or 39 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment.13. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 12, comprising the three CDR1, CDR2 and CDR3 complementarity determining regions (CDRs) of any one of SEQ ID NOs: 8, 24, or 38.14. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 13, comprising20240028-02_039062.00183 the three CDR1, CDR2 and CDR3 complementarity determining regions (CDRs) of any one of SEQ ID NOs: 9, 25, or 39.15. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 14, wherein the antibody heavy chain is an IgM, IgG, IgA or IgE isotype heavy chain, and / or the light chain is a kappa or a lambda light chain.16. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 15, further comprising, or is bound to or covalently conjugated to, a detectable agent or a binding moiety.17. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of aspects 1 to 16, wherein the detectable agent comprises: an enzyme, a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7- methoxycoumarin (Mca), dabcyl, [2-(4-nitro-2,l,3-benzoxadiazol-7- yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron-dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten or an antibody binding epitope or domain.18. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 17, wherein the enzyme is a peroxidase, an alkaline phosphatase, or a beta-galactosidase.19. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 17, wherein the peroxidase is a horse radish peroxidase (HRP).20240028-02_039062.0018320. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 17, wherein the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine.21. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 17, wherein the dye comprises a cyanine dye; or Cy3 or Cy5.22. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 17, wherein the fluorophore comprises dansyl, fluorescein or carboxyfluorescein (FAM) or 6-FAM.23. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of aspect 16, wherein the binding moiety comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein.24. A recombinant nucleic acid molecule encoding a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigenbinding protein according to any one of aspects 1 to 23.25. The recombinant nucleic acid molecule of aspect 24, wherein the recombinant nucleic acid further comprises and is operatively linked to a transcriptional regulatory element.26. The recombinant nucleic acid molecule of aspect 25, wherein the transcriptional regulatory element comprises a promoter.27. The recombinant nucleic acid molecule of aspect 26, wherein the promoter is an inducible promoter or a constitutive promoter.20240028-02_039062.0018328. The recombinant nucleic acid molecule of any of aspects 20 to 27, wherein the recombinant nucleic acid further comprises a sequence encoding an additional protein or peptide moiety or domain.29. The recombinant nucleic acid molecule of aspect 28, wherein the additional protein or peptide moiety or domain comprises a purification moiety or domain to aid in the purification or isolation of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, encoded by the recombinant nucleic acid.30. The recombinant nucleic acid molecule of aspect 28 or aspect 29, wherein the additional protein or peptide moiety or domain comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein.31. The recombinant nucleic acid molecule of any of aspects 24 to 30, wherein the recombinant nucleic acid further comprises a sequence encoding a protease cleavage site positioned between the purification moiety or domain and the sequence encoding the chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein.32. An expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid comprising a recombinant nucleic acid molecule of any of aspects 24 to 31.33. A cell comprising a chimeric or a recombinant antibody (Ab), or an antigenbinding fragment thereof, or a monomeric or dimeric antigen-binding protein of any of any one of aspects 1 to 23, a recombinant nucleic acid molecule of any of aspects 24 to 31, or an expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid of aspect 32.20240028-02_039062.0018334. The cell of aspect 33, wherein the cell is a bacterial, fungal, mammalian, yeast, insect, avian or plant cell.35. A method for generating a polyclonal antibody, or for generating a polyclonal immune serum, that is specific for or specifically binds to isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”), the method comprising administering to or immunizing a mammal or an avian species with a peptide or polypeptide, or an epitope, comprising the amino acid sequence of SEQ ID NO: 1, or a fragment thereof.36. A method for detecting the presence of isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”) in a cell, a tissue, an organ, or a portion thereof, comprising:(a) contacting the cell, tissue, organ, or portion thereof with a chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein of any of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31, and(b) detecting the specific binding of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, with a human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, in the cell, tissue, organ, or portion thereof.37. The method of aspect 36, wherein the contacting comprises use of an immunohistochemistry (IHC) assay.38. The method of aspect 36 or aspect 37, further comprising contacting the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein with a detectable agent to indicate or signal the specific binding of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or20240028-02_039062.00183 monomeric or dimeric antigen-binding protein to the human Claudin-18.2 polypeptide or the fragment thereof.39. The method of aspect 38, wherein the detectable agent specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein.40. The method of aspect 38 or aspect 39, wherein the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein which is bound to the human Claudin-18.2 polypeptide.41. The method of any of aspects 38 to 40, wherein the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to a hapten or tag attached or conjugated to the chimeric or recombinant antibody (Ab) or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein.42. The method of any of aspects 38 to 41, wherein the antibody or an antigenbinding fragment or the secondary antibody further comprises or has attached or conjugated thereto a second detectable agent or an enzyme.43. The method of aspect 42, wherein the enzyme is an alkaline phosphatase, a betagalactosidase or a peroxidase.44. The method of aspect 36 or aspect 37, wherein the antibody or an antigenbinding fragment or the secondary antibody further comprises or has attached or conjugated thereto a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7-m ethoxy coumarin (Mca), dabcyl, [2-(4-nitro- 2,l,3-benzoxadiazol-7-yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron-20240028-02_039062.00183 dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten.45. The method of aspect 44, wherein the dye comprises a cyanine dye, or Cy3 or Cy5.46. The method of aspect 44, wherein the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine.47. A method for diagnosing a human cancer that expresses isoform 2 of Claudin- 18 (“Claudin-18.2”), comprising: detecting the expression or presence of a Claudin-18.2 polypeptide or fragment thereof, in a cell, tissue, or organ sample, or a portion thereof, by contacting the cell, tissue, organ sample, or portion thereof with a chimeric or recombinant antibody or antigen-binding fragment thereof of any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31, and detecting whether or not the chimeric or recombinant antibody specifically binds to the human Claudin-18.2 polypeptide or fragment thereof in the cell, tissue, organ sample, or portion thereof, wherein the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue, or organ sample, or the portion thereof.48. The method of aspect 47, wherein the cell is (i) a differentiated epithelial cell, optionally from gastric mucosa or (ii) a tumor cell, optionally derived from a gastrointestinal epithelial cell.49. The method of aspect 47 or aspect 48, wherein the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue or organ sample, or portion thereof, thereby diagnosing the cancer.20240028-02_039062.0018350. The method of any of aspects 47 to 49, wherein the cancer is a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; or b) a solid tumor.51. The method of any of aspects 47 to 49, wherein the cancer is an adenocarcinoma.52. The method of any of aspects 47 to 51, wherein the detection comprises using or conducting an immunohistochemistry (IHC) assay or a flow cytometry.53. The method of aspect 52, wherein the conducting or using of the flow cytometry comprises use of a fluorescence-activated cell sorter (FACS) or an impedance flow cytometer.54. The method of any of aspects 47 to 53, wherein the cell, tissue, organ sample, or portion thereof is or is derived from a biopsy from a patient.55. A method for treating, ameliorating or preventing a cancer comprising first detecting or diagnosing the cancer in an individual in need thereof using a method of any of aspects 47 to 54, followed by treatment of the individual in need thereof.56. The method of aspect 55, wherein the cancer is a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; b) a solid tumor; and / or c) an adenocarcinoma.57. Use of a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31, for detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer.20240028-02_039062.0018358. A chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31, for use in detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer.59. A kit comprising a chimeric or a recombinant antibody (Ab), or an antigenbinding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31.60. The kit of aspect 59, further comprising components needed for an immunohistochemistry (IHC) assay.61. The kit of aspect 59 or aspect 60, comprising instructions for practicing a method of any of the preceding aspects.62. The kit of any of aspects 59 to 61, wherein the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or dimeric antigenbinding protein, is substantially purified or isolated.63. A product of manufacture comprising a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31.64. The product of manufacture of aspect 63, wherein the product of manufacture comprises or is fabricated as or manufactured as a slide, a well, a chip, a biochip, an array, a tray, a dish or a microtiter plate or dish.65. The product of manufacture of aspect 63 or aspect 64, wherein the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or20240028-02_039062.00183 dimeric antigen-binding protein, is substantially purified or isolated, or is in the form of an unpurified or partially purified culture supernatant.66. A phage or a phagemid comprising or expressing on its surface a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of aspects 1 to 23, or encoded by a recombinant nucleic acid molecule of any of aspects 24 to 31.EXAMPLE

[0081] Unless stated otherwise in the Examples, all recombinant DNA techniques are carried out according to standard protocols, for example, as described in Sambrook et al. (2012) Molecular Cloning: A Laboratory Manual, 4th Edition, Cold Spring Harbor Laboratory Press, NY and in Volumes 1 and 2 of Ausubel et al. (1994) Current Protocols in Molecular Biology, Current Protocols, USA. Other references for standard molecular biology techniques include Sambrook and Russell (2001) Molecular Cloning: A Laboratory Manual, 3rdEdition, Cold Spring Harbor Laboratory Press, NY, Volumes I and II of Brown (1998) Molecular Biology LabFax, Second Edition, Academic Press (UK). Standard materials and methods for polymerase chain reactions can be found in Dieffenbach and Dveksler (1995) PCR Primer: A Laboratory Manual, Cold Spring Harbor Laboratory Press, and in McPherson at al. (2000) PCR - Basics: From Background to Bench, 1stEdition, Springer Verlag, Germany.

[0082] Example 1 : Development of an exemplary anti-Claudin-18.2 antibody

[0083] This example describes the development of an exemplary rabbit anti-human Claudin-18.2 antibody. An antigen comprising a fragment of human Claudin-18.2 was selected for study. A KLH-conjugated synthetic peptide comprising this fragment was used to immunize several rabbits. Animal bleeds were later taken to confirm serum reactivity to human Claudin- 18.2 protein in several positive and negative clinically relevant human tissues by IHC. Blood20240028-02_039062.00183 from rabbits that displayed a strong immune response against human Claudin-18.2 antigens was used to carry out several B-cell selections. Briefly, B-cells expressing antigen-specific antibodies were isolated as monoclonals and cultured before testing by ELISA and IHC on human tissues with high and low pH antigen retrieval buffers. The best performing clones were chosen based on IHC performance on normal gastric tissues (Claudin-18.2- / Claudin-18.2+) and normal lung tissues (Claudin-18.2+ / Claudin-18.2-). The antibody variable sequences were sequenced and cloned into a custom-made expression vector, containing either the constant domains of the heavy chain or kappal light chain. Recombinant antibodies were expressed in HEK293-6E cells. Recombinant antibodies were tested for human Claudin-18.2 antigen binding by biolayer interferometry (BLI), and subsequently tested in IHC by standard FLEX protocols on normal and clinical tissues. Multiple antibodies generated and screened using the foregoing protocols were found to show human Claudin-18.2 specific staining in IHC.* * *

[0084] In closing, it is to be understood that although aspects of the present specification are highlighted by referring to specific embodiments, one skilled in the art will readily appreciate that these disclosed embodiments are only illustrative of the principles of the subject matter disclosed herein. Therefore, it should be understood that the disclosed subject matter is in no way limited to a particular compound, composition, article, apparatus, methodology, protocol, and / or reagent, etc., described herein, unless expressly stated as such. In addition, those of ordinary skill in the art will recognize that certain changes, modifications, permutations, alterations, additions, subtractions and sub-combinations thereof can be made in accordance with the teachings herein without departing from the spirit of the present specification. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such changes, modifications, permutations, alterations, additions, subtractions and sub- combinations as are within their true spirit and scope.20240028-02_039062.00183

[0085] Certain aspects of the present disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the present disclosure to be practiced otherwise than specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described embodiments in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0086] Groupings of alternative embodiments, elements, or steps of the present disclosure are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other group members disclosed herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0087] Use of the terms “may” or “can” in reference to an embodiment or aspect of an embodiment also carries with it the alternative meaning of “may not” or “cannot.” As such, if the present specification discloses that an embodiment or an aspect of an embodiment may be or can be included as part of the inventive subject matter, then the negative limitation or exclusionary proviso is also explicitly meant, meaning that an embodiment or an aspect of an embodiment may not be or cannot be included as part of the inventive subject matter. In a similar manner, use of the term “optionally” in reference to an embodiment or aspect of an embodiment means that such embodiment or aspect of the embodiment may be included as20240028-02_039062.00183 part of the inventive subject matter or may not be included as part of the inventive subject matter. Whether such a negative limitation or exclusionary proviso applies will be based on whether the negative limitation or exclusionary proviso is recited in the claimed subject matter.

[0088] Notwithstanding that the numerical ranges and values setting forth the broad scope of the disclosure are approximations, the numerical ranges and values set forth in the specific examples are reported as precisely as possible. Any numerical range or value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Recitation of numerical ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate numerical value falling within the range. Unless otherwise indicated herein, each individual value of a numerical range is incorporated into the present specification as if it were individually recited herein.

[0089] The terms “a,” “an,” “the” and similar references used in the context of describing aspects of the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, ordinal indicators — such as “first,” “second,” “third,” etc. — for identified elements are used to distinguish between the elements, and do not indicate or imply a required or limited number of such elements, and do not indicate a particular position or order of such elements unless otherwise specifically stated. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or “exemplary” language (e.g., “such as”) provided herein is intended merely to better illuminate the present disclosure and does not pose a limitation on the scope of the invention otherwise claimed. No language in the present specification should be construed as indicating any non-claimed element essential to the practice of the invention.20240028-02_039062.00183

[0090] When used in the claims, whether as filed or added per amendment, the open-ended transitional term “comprising” (and equivalent open-ended transitional phrases thereof like including, containing and having) encompasses all the expressly recited elements, limitations, steps and / or features alone or in combination with unrecited subject matter; the named elements, limitations and / or features are essential, but other unnamed elements, limitations and / or features may be added and still form a construct within the scope of the claim. Specific embodiments disclosed herein may be further limited in the claims using the closed-ended transitional phrases “consisting of’ or “consisting essentially of’ in lieu of or as an amended for “comprising.” When used in the claims, whether as filed or added per amendment, the closed-ended transitional phrase “consisting of’ excludes any element, limitation, step, or feature not expressly recited in the claims. The closed-ended transitional phrase “consisting essentially of’ limits the scope of a claim to the expressly recited elements, limitations, steps and / or features and any other elements, limitations, steps and / or features that do not materially affect the basic and novel characteristic(s) of the claimed subject matter. Thus, the meaning of the open-ended transitional phrase “comprising” is being defined as encompassing all the specifically recited elements, limitations, steps and / or features as well as any optional, additional unspecified ones. The meaning of the closed-ended transitional phrase “consisting of’ is being defined as only including those elements, limitations, steps and / or features specifically recited in the claim whereas the meaning of the closed-ended transitional phrase “consisting essentially of’ is being defined as only including those elements, limitations, steps and / or features specifically recited in the claim and those elements, limitations, steps and / or features that do not materially affect the basic and novel characteristic(s) of the claimed subject matter. Therefore, the open-ended transitional phrase “comprising” (and equivalent open- ended transitional phrases thereof) includes within its meaning, as a limiting case, claimed subject matter specified by the closed-ended transitional phrases “consisting of’ or “consisting20240028-02_039062.00183 essentially of.” As such embodiments described herein or so claimed with the phrase “comprising” are expressly or inherently unambiguously described, enabled and supported herein for the phrases “consisting essentially of’ and “consisting of.”

[0091] All patents, patent publications, and other publications referenced and identified in the present specification are individually and expressly incorporated herein by reference in their entirety for the purpose of describing and disclosing, for example, the compositions and methodologies described in such publications that might be used in connection with the present disclosure. These publications are provided solely for their disclosure prior to the filing date of the present application. Nothing in this regard should be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior disclosure or for any other reason. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicants and does not constitute any admission as to the correctness of the dates or contents of these documents.

[0092] Lastly, the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention, which is defined solely by the claims. Accordingly, the present invention is not limited to that precisely as shown and described.20240028-02_039062.00183SEQUENCE LISTING20240028-02_039062.0018320240028-02_039062.0018320240028-02_039062.0018320240028-02_039062.0018320240028-02_039062.00183

Claims

20240028-02_039062.00183CLAIMSWe claim:

1. A chimeric or a recombinant antibody (“Ab”), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein, capable of specifically binding to isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”) having an amino acid sequence comprising or consisting of SEQ ID NO: 1, or a fragment thereof.

2. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of claim 1, fabricated as or in the form of: an antigen-binding fragment, a F(ab')2, a Fab', a single-chain variable fragment (“scFv”), a (SCFV)2, a minibody, a diabody, or a tetrabody.

3. The chimeric or recombinant antibody (Ab), or antigen-binding-fragment thereof, or monomeric or dimeric antigen-binding protein, of claim 1 or claim 2, wherein the sequence of the heavy chain variable domain is:QSVEESGGRLVTPGTPLTLTCTVSGFSLSYYNMAWVRQAPGKGLEWIGGIATVGTTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYFLNLWGQGTLVT VSS (SEQ ID NO: 8), QSVEESGGRLVTPGTPLTLTCTVSGFSLSRYNMAWVRQAPGKGLEWIGGIATVGSTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYLLNLWGQGTLVTVSS (SEQ ID NO: 24), orQSVEESGGRLVTPGTPLTLTCTASGFSLSKHDMNWVRQAPGKGLEYIGFISYGGSAY YARWAKGREI ISKTSTTVDLKI ISPTTEDTATYFCARSGI ITLTLWGQGTLVTVSS (SEQ ID NO: 38).20240028-02_039062.001834. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of claims 1 to 3, wherein the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYNNNYLSWFQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQLTLTISDVQCVDAATYYCAGGYSSTIDARAFGGGTEVWK (SEQ ID NO: 9),AQVLTQTPSSVSAAVGGTVTINCQSSQSVYSHNYLSWYQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQFTLTISDVQCDDAATYYCAGGYSSS IDARAFGGGTEVWK(SEQ ID NO: 25), orAAVLTQTPSSTSAAVGGTVTINCQSSQSVYSNNYLSWYQQKPGQPPKLLIYKASTLA SGVPSRFRGSGSGTQFTLTINDLECDDAATYFCAGGYSSSGDITDNAFGGGTEVWK (SEQ ID NO: 39).

5. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of claims 1 to 4, wherein the sequence of the heavy chain variable domain is:QSVEESGGRLVTPGTPLTLTCTVSGFSLSYYNMAWVRQAPGKGLEWIGGIATVGTTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYFLNLWGQGTLVTVSS (SEQ ID NO: 8), and the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYNNNYLSWFQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQLTLTISDVQCVDAATYYCAGGYSSTIDARAFGGGTEVWK (SEQ ID NO: 9); or the sequence of the heavy chain variable domain is:QSVEESGGRLVTPGTPLTLTCTVSGFSLSRYNMAWVRQAPGKGLEWIGGIATVGSTY YASWVNGRFTISKTSTTVDLKMTSLTAADTATYFCARDLTTNNGYLLNLWGQGTLVTVSS (SEQ ID NO: 24), and the sequence of the light chain variable domain is:AQVLTQTPSSVSAAVGGTVTINCQSSQSVYSHNYLSWYQQKPGQPPKLLIYGASTLA SGVPSRFKGSGSGTQFTLTISDVQCDDAATYYCAGGYSSS IDARAFGGGTEVWK (SEQ ID NO: 25); or the sequence of the heavy chain variable domain isQSVEESGGRLVTPGTPLTLTCTASGFSLSKHDMNWVRQAPGKGLEYIGFISYGGSAY YARWAKGREI ISKTSTTVDLKI ISPTTEDTATYFCARSGI ITLTLWGQGTLVTVSS (SEQ ID NO: 38), and the sequence of the light chain variable domain is:20240028-02_039062.00183AAVLTQTPS S TSAAVGGTVT INCQS SQSVYSNNYLSWYQQKPGQPPKLL IYKAS TLA SGVPSRFRGSGSGTQFTLT INDLECDDAATYFCAGGYS S SGDI TDNAFGGGTEVWK (SEQ ID NO: 39).

6. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of claims 1 to 5, having an amino acid sequence further comprising:(a) a heavy chain variable domain and a constant domain having any one of SEQ ID NOs: 14, 28, or 42;(b) a heavy chain signal peptide having SEQ ID NO: 12;(c) a heavy chain variable domain and a signal peptide sequence having any one of SEQ ID NOs: 16, o 30, or 44;(d) a heavy chain variable domain and a constant domain and a signal peptide sequence having any one of SEQ ID NOs: 10, 26, or 40;(e) a light chain variable domain and a constant domain having any one of SEQ ID NOs: 15, 29, or 43;(f) a light chain signal peptide having SEQ ID NO: 13;(g) a light chain variable domain and signal peptide sequence having any one of SEQ ID NOs: 17, 31, or 45;(h) a light chain variable domain and a constant domain and a signal peptide sequence having any one of SEQ ID NOs: 11, 27, or 41;(i) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 2, 3, or 4; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 2, 3, 4, optionally wherein the one or more substitutions are conservative substitutions;(j) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 5, 6, or 7; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 5, 6, or 7, optionally wherein the one or more substitutions are conservative substitutions;(k) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 18, 19, or 20; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions20240028-02_039062.00183 compared to any one of SEQ ID NOs: 18, 19, or 20, optionally wherein the one or more substitutions are conservative substitutions;(l) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from any one of SEQ ID NOs: 21, 22, or 23; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 21, 22, or 23, optionally wherein the one or more substitutions are conservative substitutions;(m) a heavy chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 32, 33, or 34; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 32, 33, or 34, optionally wherein the one or more substitutions are conservative substitutions; and / or(n) a light chain variable domain comprising one or more complementarity determining regions (CDRs) having an amino acid sequence selected from SEQ ID NOs: 35, 36, or 37; or an amino acid sequence having 1, 2, 3, 4, or 5 amino acid substitutions compared to any one of SEQ ID NOs: 35, 36, or 37, optionally wherein the one or more substitutions are conservative substitutions.

7. The chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, of any of claims 1 to 6, wherein the sequence of the heavy chain variable domain comprises SEQ ID NO: 8, 24, or 38 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the heavy chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a light chain variable domain; wherein the sequence of the light chain variable domain comprises SEQ ID NO: 9, 25, or 39 having at least one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve conservative amino acid substitutions, wherein the light chain variable domain is capable of specifically binding to the human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, when either unpaired or paired with a heavy chain variable domain;20240028-02_039062.00183 wherein the sequence of the heavy chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs:8, 24, or 38; wherein the sequence of the light chain variable domain has at least about 25%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90% or 95% sequence identity compared to SEQ ID NOs:9, 25, or 39; wherein the sequence of the heavy chain variable domain and the amino acid sequence of SEQ ID NOs: 8, 24, or 38 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment; wherein the sequence of the light chain variable domain and the amino acid sequence of SEQ ID NOs: 9, 25, or 39 has a Z score of from about 2 to about 8, or a Z score of at least 8, when aligned using distance matrix alignment; comprising the three CDR1, CDR2 and CDR3 complementarity determining regions (CDRs) of any one of SEQ ID NOs: 8, 24, or 38; comprising the three CDR1, CDR2 and CDR3 complementarity determining regions (CDRs) of any one of SEQ ID NOs: 9, 25, or 39; wherein the antibody heavy chain is an IgM, IgG, IgA or IgE isotype heavy chain, and / or the light chain is a kappa or a lambda light chain; or further comprising, or is bound to or covalently conjugated to, a detectable agent or a binding moiety, optionally, wherein the detectable agent comprises: an enzyme, a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7-methoxy coumarin (Mca), dabcyl, [2-(4-nitro-2,l,3- benzoxadiazol-7-yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron- dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten or an antibody binding epitope or domain, optionally, wherein the enzyme is a peroxidase, an alkaline phosphatase, or a betagalactosidase, optionally, wherein the peroxidase is a horse radish peroxidase (HRP), optionally, wherein the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine, optionally, wherein the dye comprises a cyanine dye; or Cy3 or Cy5, optionally, wherein the fluorophore comprises dansyl, fluorescein or carboxyfluorescein (FAM) or 6-FAM, optionally, wherein the binding moiety comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein.20240028-02_039062.001838. A recombinant nucleic acid molecule encoding a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigenbinding protein according to any one of claims 1 to 7.

9. The recombinant nucleic acid molecule of claim 8, wherein the recombinant nucleic acid further comprises and is operatively linked to a transcriptional regulatory element, optionally, wherein the transcriptional regulatory element comprises a promoter optionally, wherein the promoter is an inducible promoter or a constitutive promoter; wherein the recombinant nucleic acid further comprises a sequence encoding an additional protein or peptide moiety or domain, optionally, wherein the additional protein or peptide moiety or domain comprises a purification moiety or domain to aid in the purification or isolation of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, encoded by the recombinant nucleic acid, optionally, wherein the additional protein or peptide moiety or domain comprises: a glutathione S-transferase (GST) or ligandin tag, a polyhistidine (poly-his) tag, a chitin binding protein (CBP), a STREP-TAG™ (SEQ ID NO:46) peptide tag, a FLAG tag (SEQ ID NO:47) peptide tag, or a maltose binding protein; or wherein the recombinant nucleic acid further comprises a sequence encoding a protease cleavage site positioned between the purification moiety or domain and the sequence encoding the chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein.

10. An expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid comprising a recombinant nucleic acid molecule of claim 8 or 9.

11. A cell comprising a chimeric or a recombinant antibody (Ab), or an antigenbinding fragment thereof, or a monomeric or dimeric antigen-binding protein of any of any one of claims 1 to 7, a recombinant nucleic acid molecule of claim 8 or 9, or an expression cassette, vector, recombinant virus, artificial chromosome, cosmid or plasmid of claim 10, optionally, wherein the cell is a bacterial, fungal, mammalian, yeast, insect, avian or plant cell.20240028-02_039062.0018312. A method for generating a polyclonal antibody, or for generating a polyclonal immune serum, that is specific for or specifically binds to isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”), the method comprising administering to or immunizing a mammal or an avian species with a peptide or polypeptide, or an epitope, comprising the amino acid sequence of SEQ ID NO: 1, or a fragment thereof.

13. A method for detecting the presence of isoform 2 of a human Claudin-18 polypeptide (“Claudin-18.2”) in a cell, a tissue, an organ, or a portion thereof, comprising:(a) contacting the cell, tissue, organ, or portion thereof with a chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein of any of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of claim 8 or 9, and(b) detecting the specific binding of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, with a human Claudin-18.2 polypeptide having the amino acid sequence of SEQ ID NO: 1, or a fragment thereof, in the cell, tissue, organ, or portion thereof.

14. The method of claim 36, wherein the contacting comprises use of an immunohistochemistry (IHC) assay; or further comprising contacting the chimeric or recombinant antibody (Ab), or antigenbinding fragment thereof, or monomeric or dimeric antigen-binding protein with a detectable agent to indicate or signal the specific binding of the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein to the human Claudin-18.2 polypeptide or the fragment thereof, optionally, wherein the detectable agent specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, optionally, wherein the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to the chimeric or recombinant antibody (Ab), or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein which is bound to the human Claudin-18.2 polypeptide, optionally, wherein the detectable agent is or comprises an antibody or an antigen-binding fragment or a secondary antibody thereof that specifically binds to a hapten or tag attached or conjugated to the chimeric or recombinant antibody (Ab) or antigen-binding fragment thereof, or monomeric or dimeric antigen-binding protein, optionally, wherein the antibody or an antigen-binding fragment or the secondary20240028-02_039062.00183 antibody further comprises or has attached or conjugated thereto a second detectable agent or an enzyme, optionally, wherein the enzyme is an alkaline phosphatase, a beta-galactosidase or a peroxidase, optionally, wherein the antibody or an antigen-binding fragment or the secondary antibody further comprises or has attached or conjugated thereto a biotin, a fluorescent or chemiluminescent label, a fluorophore, sulfoindo-cyanine, nile red, rhodamine, perylene, fluorenyl, coumarin, 7-methoxy coumarin (Mca), dabcyl, [2-(4-nitro-2,l,3-benzoxadiazol-7- yl)aminoethyl]trimethylammonium (NBD), Nile blue, Tamra, boron-dipyrromethene (BODIPY), or derivatives thereof), a dye, a radioisotope, a quantum dot or photoluminescent aqueous nanocrystal, a hapten, optionally, wherein the dye comprises a cyanine dye, or Cy3 or Cy5, optionally, wherein the hapten comprises a biotin, theophylline, digoxigenin, carborane, fluorescein or bromodeoxyuridine.

15. A method for diagnosing a human cancer that expresses isoform 2 of Claudin- 18 (“Claudin-18.2”), comprising: detecting the expression or presence of a Claudin-18.2 polypeptide or fragment thereof, in a cell, tissue, or organ sample, or a portion thereof, by contacting the cell, tissue, organ sample, or portion thereof with a chimeric or recombinant antibody or antigen-binding fragment thereof of any one of claims 1 to 23, or encoded by a recombinant nucleic acid molecule of any of claims 24 to 31, and detecting whether or not the chimeric or recombinant antibody specifically binds to the human Claudin-18.2 polypeptide or fragment thereof in the cell, tissue, organ sample, or portion thereof, wherein the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue, or organ sample, or the portion thereof.

16. The method of claim 15, wherein the cell is (i) a differentiated epithelial cell, optionally from gastric mucosa or (ii) a tumor cell, optionally derived from a gastrointestinal epithelial cell; wherein the detecting of specific binding indicates the expression or presence of the human Claudin-18.2 polypeptide or fragment thereof, in the cell, tissue or organ sample, or portion thereof, thereby diagnosing the cancer; wherein the cancer is a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; or20240028-02_039062.00183 b) a solid tumor, optionally, wherein the cancer is an adenocarcinoma; wherein the detection comprises using or conducting an immunohistochemistry (IHC) assay or a flow cytometry, optionally, wherein the conducting or using of the flow cytometry comprises use of a fluorescence-activated cell sorter (FACS) or an impedance flow cytometer; or wherein the cell, tissue, organ sample, or portion thereof is or is derived from a biopsy from a patient.

17. A method for treating, ameliorating or preventing a cancer comprising first detecting or diagnosing the cancer in an individual in need thereof using a method claim 15 or claim 16, followed by treatment of the individual in need thereof.

18. The method of claim 17, wherein the cancer is a) selected from the group consisting of: a pancreatic cancer, a gastric cancer, a colo-rectal cancer, an ovarian career, a lung cancer, or an esophageal cancer; b) a solid tumor; and / or c) an adenocarcinoma.

19. Use of a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of claim 8 or 9, for detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer.

20. A chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of any of claim 8 or 9, for use in detecting or diagnosing a cancer, or treating, ameliorating or preventing a cancer.

21. A kit comprising a chimeric or a recombinant antibody (Ab), or an antigenbinding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of claim 8 or 9.

22. The kit of claim 21, further comprising components needed for an immunohistochemistry (IHC) assay;20240028-02_039062.00183 comprising instructions for practicing a method of any of the preceding claims; or wherein the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or dimeric antigen-binding protein, is substantially purified or isolated.

23. A product of manufacture comprising a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of claim 8 or 9.

24. The product of manufacture of claim 23, wherein the product of manufacture comprises or is fabricated as or manufactured as a slide, a well, a chip, a biochip, an array, a tray, a dish or a microtiter plate or dish; or wherein the chimeric or the recombinant antibody (Ab), the antigen-binding fragment thereof, or the monomeric or dimeric antigen-binding protein, is substantially purified or isolated, or is in the form of an unpurified or partially purified culture supernatant.

25. A phage or a phagemid comprising or expressing on its surface a chimeric or a recombinant antibody (Ab), or an antigen-binding fragment thereof, or a monomeric or dimeric antigen-binding protein according to any one of claims 1 to 7, or encoded by a recombinant nucleic acid molecule of claim 8 or 9.

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