Claudin-18.2 testing and its impact in the therapeutic management of patients with gastric and gastroesophageal adenocarcinomas: A literature review with expert opinion

Claudin 18 (43-14A clone) expression in pancreatic ductal adenocarcinoma: Assessment of a potential clinical biomarker for zolbetuximab therapy

Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal, with a five-year survival rate below 15 %. Claudin 18.2 (CLDN18.2) has emerged as a novel potential therapeutic target in PDAC. Zolbetuximab, a monoclonal antibody targeting CLDN18.2, has demonstrated therapeutic benefit in gastric cancers and is now in phase 2 clinical trials for PDAC. Trial eligibility for zolbetuximab requires tumor membranous immunohistochemical staining with the pan-claudin 18 companion diagnostic antibody clone 43-14A. However, the expression of CLDN18 detected using this clone has only been evaluated in 62 patients from a single retrospective study. Herein, we report immunohistochemical staining using 43-14A on surgically resected PDAC samples (n = 120). Samples were stained following the protocol used in clinical trials, using the 43-14A VENTANA antibody in a prediluted kit, and according to the manufacturer's recommended protocol. Positive cases were defined as ≥ 75 % of tumor cells exhibiting membranous staining with an intensity of ≥ 2+. Out of 120 PDAC cases, 39 (32.5 %) stained positive for CLDN18 with 43-14A. A significant association was observed between lower tumor grade and higher 43-14A staining (p < 0.05). CLDN18-positive cases demonstrated significantly improved survival at the cohort's median overall survival (23 months, p < 0.05), suggesting that claudin expression could serve as a both a diagnostic and prognostic marker. Our findings indicate that 32.5 % of PDAC tumors in this cohort are positive for CLDN18, suggesting that a significant proportion of patients with PDAC could benefit from zolbetuximab and other CLDN18.2 targeted immunotherapies if pancreatic cancer therapeutic trials prove successful.

Heterogeneity of predictive biomarker expression in gastric and esophago-gastric junction carcinoma with peritoneal dissemination

BACKGROUND

Temporal and spatial molecular heterogeneity contributes to resistance to targeted and immune therapies in gastric and esophagogastric junction carcinoma (G/EGJ). This study evaluates differences in biomarker expression between primary G/EGJ and paired peritoneal metastases (PM).

METHODS

We analyzed 74 cases of primary G/EGJ and paired PM using immunohistochemistry for HER2, PD-L1, Claudin18 (CLDN18), DNA mismatch repair (MMR) proteins, p53, E-cadherin, and in situ hybridization for EBER. Biomarker concordance between primary and metastatic tumors was assessed.

RESULTS

Primary G/EGJ were predominantly poorly cohesive (45.9%) or mixed-type (37.8%). Regarding predictive biomarkers, low rates of HER2 overexpression (5.4%), MMR deficiency (4.1%), and EBER positivity (1.4%) were observed, while PD-L1 CPS ≥ 1 occurred in 79.7% of cases and CLDN18 positivity was observed in 31.1% of cases. Concordance was perfect for MMR and EBER, while PD-L1 showed the highest discordance (32.4%). HER2 had a low discordance rate (2.7%). CLDN18 exhibited good concordance (86.5%) and showed consistent positivity in PD-L1- and HER2-negative primary tumors (28.6%).

CONCLUSION

G/EGJ with PM show distinct molecular features and spatial heterogeneity, with MMR, EBER, and HER2 demonstrating strong concordance, while PD-L1 showed greater variability. As for novel biomarkers, CLDN18.2 shows substantial concordance between primary G/EGJ and PM and could be a promising target in HER2/PD-L1-negative G/EGJ with PM.

Discordance in Claudin 18.2 Expression Between Primary and Metastatic Lesions in Patients With Gastric Cancer

PURPOSE

Claudin 18.2 (CLDN18.2) has emerged as a promising therapeutic target for CLDN18.2-expressing gastric cancer (GC). We sought to examine the heterogeneity of CLDN18.2 expression between primary GC (PGC) and metastatic GC (MGC) using various scoring methods.

MATERIALS AND METHODS

We retrospectively analyzed data from 102 patients with pathologically confirmed paired primary and metastatic gastric or gastroesophageal junction adenocarcinomas. CLDN18.2 expression was evaluated through immunohistochemistry on formalin-fixed paraffin-embedded tissue samples. We assessed CLDN18.2 positivity using multiple scoring approaches, including the immunoreactivity score, H-score, and the percentage of tumor cells showing moderate-to-strong staining intensity. We analyzed the concordance rates between PGC and MGC and the association of CLDN18.2 positivity with clinicopathological features.

RESULTS

CLDN18.2 positivity varied from 25% to 65% depending on the scoring method, with PGC consistently showing higher expression levels than MGC. Intratumoral heterogeneity was noted in 25.5% of PGCs and 19.6% of MGCs. Intertumoral heterogeneity, manifesting as discordance in CLDN18.2 positivity between PGC and MGC, was observed in about 20% of cases, with moderate agreement across scoring methods (κ=0.47 to 0.60). In PGC, higher CLDN18.2 positivity correlated with synchronous metastasis, presence of peritoneal metastasis, poorly differentiated grade, and biopsy specimens. In MGC, positivity was associated with synchronous metastasis, presence of peritoneal metastasis, and metastatic peritoneal tissues.

CONCLUSIONS

CLDN18.2 expression demonstrates significant heterogeneity between PGC and MGC, with a 20% discordance rate. Comprehensive tissue sampling and reassessment of CLDN18.2 status are crucial, especially before initiating CLDN18.2-targeted therapies.

Biomarkers in gastroesophageal cancer 2025: an updated consensus statement by the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP)

Gastroesophageal carcinomas, including gastroesophageal adenocarcinoma (GEA) and esophageal squamous cell carcinoma (ESCC), pose a global health challenge due to their heterogeneity. The approach to diagnosis and treatment should first differentiate between GEA and ESCC. Over the past decade, therapies for metastatic or advanced GEA/ESCC have expanded, with several new therapeutic targets alongside trastuzumab for metastatic HER2-positive GEA. Four key biomarkers are essential for targeted therapy: HER2 overexpression/amplification, deficient mismatch repair/microsatellite instability (dMMR/MSI), PD-L1, and Claudin18.2 expression. Immunohistochemistry is the recommended method for these biomarkers evaluation. In addition, the assessment of biomarkers like FGFR2b is likely to become routine in the near future. Experts from the Spanish Society of Pathology (SEAP) and the Spanish Society of Medical Oncology (SEOM) have formed a consensus to optimize biomarker detection and usage in clinical practice. Their recommendations aim to improve personalized treatment strategies for GEA and ESCC patients, integrating new diagnostic insights into routine care.

Evolving Treatment Landscape for Advanced Esophageal and Gastroesophageal Junction Adenocarcinoma

PURPOSE OF REVIEW

This review highlights advances and recent changes in the treatment paradigm for advanced esophageal adenocarcinoma (EAC) and gastroesophageal junction adenocarcinoma (GEJAC).

RECENT FINDINGS

Chemotherapy remains the backbone of treatment for advanced EAC/GEJAC. New targets/agents include immunotherapy, HER-2, claudin18.2, and FGFR2b, with various mechanisms (CAR-T, bispecific mAB, ADCs) altering the treatment landscape against these targets. The approaches to these targets may act together, in sequence, and even synergistically to improve outcomes. Herein, we review the state of the field, including highlighting ongoing clinical trials and additional emerging agents and approaches.

Extent and clinical significance of the therapy-relevant tight junction protein Claudin 18.2 in pancreatic ductal adenocarcinoma - real-world evidence

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is associated with poor prognosis, wherefore targeted therapies have experienced increasing interest. Zolbetuximab is a novel targeted therapy under investigation in patients with PDAC and targets Claudin 18.2 (CLDN18.2), which is a component of tight junctions and is of significance in various solid tumors. As its role in PDAC is not definitively elucidated, this study aims to clarify the significance of CLDN18.2 expression in PDAC in a real-world setting.

METHODS

All patients (n = 309) were recruited at one of the PANCALYZE study centers and received pancreatic resection with curative intention. Paraffin samples were analyzed using an antibody against CLDN18.2, which is known to be comparable to the antibody used by the SPOTLIGHT and GLOW studies.

RESULTS

94 PDACs are positive for CLDN18.2 (30.4 %). Positive CLDN 18.2 expression was associated with significantly better cancer differentiation (p < 0.001). Patients with positive CLDN18.2 expression showed significantly better overall survival when compared to patients with negative expression (median OS: 30 versus 18 months, p = 0.003). Additionally, in multivariable analyses, CLDN18.2 expression was identified as an independent factor for better survival in patients with PDAC (HR = 0.686, 95 %CI = 0.492-0.956, p = 0.026).

CONCLUSION

Significant improvement in survival could be demonstrated by adding Zolbetuximab to known chemotherapy regimes in patients with gastro-esophageal junction adenocarcinoma with at least 75 % CLDN18.2 positive cancer cells. Our findings demonstrate, that 30.4 % of the included patients with PDAC would potentially be eligible for therapy with Zolbetuximab in a real-world patient cohort. Results of trials targeting Claudin 18.2 are pending in patients with PDAC.

The preclinical discovery and development of zolbetuximab for the treatment of gastric cancer

INTRODUCTION

Gastric cancer remains a formidable challenge in oncology with high mortality rates and few advancements in treatment. Claudin-18.2 (CLDN18.2) is a tight junction protein primarily expressed in the stomach and is frequently overexpressed in certain subsets of gastric cancers. Targeting CLDN18.2 with monoclonal antibodies, such as zolbetuximab (IMAB362), has shown promising efficacy results in combination with chemotherapy.

AREAS COVERED

The molecular cell biology of CLDN18.2 is discussed along with studies demonstrating the utility of CLDN18.2 expression as a biomarker and therapeutic target. Important clinical studies are reviewed, including Phase III trials, SPOTLIGHT and GLOW, which demonstrate the efficacy of zolbetuximab in combination with chemotherapy in patients with CLDN18.2-positive advanced gastric cancer.

EXPERT OPINION

CLDN18.2 is involved in gastric differentiation through maintenance of epithelial barrier function and coordination of signaling pathways, and its expression in gastric cancers reflects a 'gastric differentiation' program. Targeting Claudin-18.2 represents the first gastric cancer specific 'targeted' treatment. Further studies are needed to determine its role within current gastric cancer treatment sequencing, including HER2-targeted therapies and immunotherapies. Management strategies will also be needed to better mitigate zolbetuximab-related treatment side effects, including gastrointestinal (GI) toxicities.

Construction of a Human Immune Library from Gallbladder Cancer Patients for the Single-Chain Fragment Variable (scFv) Antibody Selection against Claudin 18.2 via Phage Display

Gallbladder cancer (GBC) is a very aggressive malignant neoplasm of the biliary tract with a poor prognosis. There are no specific therapies for the treatment of GBC or early diagnosis tools; for this reason, the development of strategies and technologies that facilitate or allow an early diagnosis of GBC continues to be decisive. Phage display is a robust technique used for the production of monoclonal antibodies (mAbs) involving (1) the generation of gene libraries, (2) the screening and selection of isoforms related to an immobilized antigen, and (3) the in vitro maturation of the affinity of the antibody for the antigen. This research aimed to construct a human immune library from PBMCs of GBC patients and the isolation of scFv-phage clones with specificity against the larger extracellular loop belonging to claudin 18.2, which is an important biomarker overexpressed in GBC as well as gastric cancer. The immune-library-denominated GALLBLA1 was constructed from seven GBC patients and has a diversity of 6.12 × 1010pfu mL-1. After three rounds of panning, we were able to identify clones with specificity against claudin 18.2. GALLBLA1 can contribute to the selection, isolation, and recombinant production of new human mAbs candidates for the treatment of gastrointestinal cancers.