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Objective To screen a monoclonal antibody (mAb) of anti-human Claudin-18 splice variant 2 (Claudin18.2) and construct chimeric antigen receptor T (CAR-T) cells targeting Claudin18.2 based on this antibody sequence for the development of CAR-T cell therapy. Methods Mice were immunized with human Claudin18.2 antigen, and then mice spleen cells were isolated and fused with SP2/0 cells to generate hybridoma cells. By hybridoma screening, we obtained the mouse against human Claudin18.2 mAb. The heavy chain variable region (VH) and light chain variable region (VL) sequences were amplified by PCR with the antibody sequence serving as the template. The linker peptide was used to link VL and VH into a single chain antibody (scFv) for CAR construction. The CAR was cloned into a lentiviral expression vector, and T cells were infected with the packaged lentivirus to prepare targeting Claudin18.2 CAR-T cells. Results The screened mouse anti-human Claudin18.2 mAb exhibited binding ability to both human and mouse Claudin18.2 antigens, with higher affinity than the control antibody. The constructed CAR-T cells showed a killing rate between 50% to 70% against Claudin18.2-overexpressing positive target cells at an effector-to-target ratio of 1:9. Conclusion The prepared mouse anti-human Claudin18.2 mAb exhibites cross-species specificity to humans and mice antigens, with good tissue specificity and high affinity. The constructed anti-Claudin18.2 CAR-T cells show effective killing of target cells.

Targeted therapy and immunotherapy have revolutionized treatment of various cancers in the past decade. Despite targeted therapy with trastuzumab in Her2-positive gastric cancer patients, survival has been dismal, mostly due to disease progression and toxicity related to the treatments. One area of active development is looking for ideal monoclonal antibodies (IMAB) specific to the proteins only on the tumor and hence avoiding unnecessary side effects. Claudin proteins with isoform 2 are one such protein, specific for several cancers, particularly gastric cancer and its metastases, leading to the development of anti-claudin 18.2 specific antibody, claudiximab. This review will highlight the latest development of claudiximab as first in class IMAB for the treatment of gastric cancer.

Claudins (CLDNs) are a 27-member family of tetra-transmembrane proteins that have pivotal roles in maintaining cellular polarity and sealing the spaces between adjacent cells. Deregulation of their functions is often associated with pathological conditions, including carcinogenesis and inflammation. Some CLDNs are co-receptors for hepatitis C virus. Because CLDN-driven regulation of intercellular seals might be manipulated to enhance drug absorption, CLDNs are attractive targets for drug development. Monoclonal antibodies recognizing the extracellular domain of CLDNs are the first choice for therapeutics, but their development has been delayed. Here, we overview recent advances in the creation of anti-CLDN antibodies and discuss CLDNs as drug development targets., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The majority of pancreatic neoplasms are characterized by a generally lethal progress within a short period of time after primary diagnosis and the mortality of patients is expected to increase further. Due to lack of efficient screening programs and moderate response to treatments, novel compounds for treatment are needed. We investigated the CLDN18.2 expression in affected patients as in vitro feasibility study for a potential treatment with the novel antibody IMAB362. Therefore, we analyzed the expression of CLDN18.2 in normal pancreatic tissues (N = 24), primary lesions (N = 202), metastases (N = 84) and intra-individually matched samples (N = 48) of patients with pancreatic ductal adenocarcinoma (PDAC), neuroendocrine neoplasia (NEN) and acinar cell carcinoma. A standardized method for evaluation by immunohistochemistry was developed. The specific staining was evaluated by two independent raters and analysis of staining intensities (range 0-3+) and relative proportions of tumor cells were performed. One hundred three (59.2%) samples of primary PDAC were found positive. The vast majority of positive samples were characterized to highly express CLDN18.2: 54.6% (N = 95) with staining intensities of ≥ 2+. NEN were positive in 20% of cases (all ≥ 2+). Metastases of pancreatic neoplasms were also frequently found positive with comparable high rates (69.4% of lymph node and 65.7% of liver metastases). The rate of CLDN18.2 positivity is high in pancreatic neoplasms whereby the expression is not limited to the primaries but is also maintained upon metastasis. Thus, a considerable number of patients with pancreatic neoplasms would be in principle eligible for a CLDN18.2-targeting approach., (© 2013 UICC.)