Comprehensive clinical and molecular characterization of claudin 18.2 expression in advanced gastric or gastroesophageal junction cancer

[Claudine 18.2: A new therapeutic target in digestive cancers]

Therapies targeting HER2 and immune checkpoint inhibitors have improved survival in patients with metastatic gastric or gastro-oesophageal junction adenocarcinoma, but the prognosis associated with these cancers remains poor. Claudin 18.2 is a tight junction protein expressed in the oeso-gastric mucosa. Some gastric and gastro-oesophageal junction adenocarcinoma overexpress this protein, as well as some pancreatic, ovarian and pulmonary cancers. In pathological context, its epitope may be exposed at the surface of cells and therefore makes it an interesting therapeutic target. Zolbetuximab, a monoclonal antibody targeting claudin 18.2, showed a survival benefit in first line metastatic treatment in patients with claudin 18.2 positive gastric and gastro-oesophageal junction adénocarcinoma, in two phase III studies. CAR T-cells specifically targeting this protein have also shown promising efficacy from the second line of treatment. Considering the probable impact of the expression status of claudin 18.2 in future treatment algorithms, this review aims to present the pathophysiology underlying the targeting of claudin 18.2, summarize state of the art results of anti-claudin 18.2 therapies and discuss future challenges for the management of patients with claudin 18.2 positive gastric and gastro-oesophageal junction adenocarcinoma.

Expression of claudin 18.2 in poorly cohesive carcinoma and its association with clinicopathologic parameters in East Asian patients

BACKGROUND

Poorly cohesive carcinoma (PCC) is a distinct subtype of gastric cancer with limited therapeutic options. This study investigated claudin (CLDN) 18.2 expression status in PCCs using a 43-13 A clone.

METHODS

We retrospectively collected 178 consecutive surgically resected stage Ⅱ-Ⅲ gastric cancer samples. Tissue microarray blocks were constructed for CLDN18.2 immunohistochemical staining. We studied CLDN18.2 expression and its association with clinicopathologic parameters.

RESULTS

CLDN18.2 positivity (defined by ≥ 75 % of tumor cells showing moderate to strong membranous positivity) was found in 34.8 % of the PCC cases (62/178). Approximately half of the CLDN18.2 positive PCCs demonstrated heterogeneous expression (51.6 %, 32/62). CLDN18.2 positivity was not associated with any clinicopathologic parameters examined. However, CLDN18.2 positivity tended to be more frequent in E-cadherin-positive PCCs (no loss of expression) than in E-cadherin-negative PCCs (loss of expression) (50 % vs. 27.7 %). The CLDN18.2 expression level, represented by the H-score, gradually decreased as the paraffin block storage time increased (P = 0.046). Overall survival and disease-free survival analyses showed no significant difference between CLDN18.2-positive and negative PCCs.

CONCLUSIONS

A significant portion of surgically resected PCC specimens showed CLDN18.2 positivity. Additionally, since the expression level of CLDN18.2 gradually decreases with increased paraffin block storage time, reflex testing can be considered at the time of the cancer diagnosis.

The Role of CLDN18.2 in Gastric Cancer Prognosis: A Systematic Review and Meta-Analysis

BACKGROUND

Gastric cancer (GC) is a major global cause of cancer mortality, with a median overall survival of just 12 months. CLDN18.2, a specific isoform of Claudin18 normally expressed in the gastric mucosa, has emerged as a potential therapeutic target and prognostic biomarker due to its exposure on the surface of tumor cells following malignant transformation. This exposure allows CLDN18.2's extracellular loops to bind monoclonal antibodies, presenting new opportunities for targeted therapy and improved prognostic assessment.

METHODS

A comprehensive search of PubMed, EMBASE, Cochrane Library and Web of Science databases was conducted for studies that addressed the correlation of CLDN18.2 with: (1) Progression-free survival (PFS), and (2) Overall Survival (OS). Hazard ratio (HR) and odds ratio (OR) with 95% confidence intervals (CIs) were calculated using a fixed-effects model. Heterogeneity was examined with I2 statistics. P values of ≤ 0.05 were considered statistically significant. Statistical analyses were performed using RStudio, version 4.2.3.

RESULTS

A total of 15 studies encompassing a total of 4,085 patients were included. There were 2,691 (65.8%) male, and 1,394 (34.2%) female patients. In the histologic GC analysis, there were 1,582 (38.7%) patients that had intestinal type and 1,280 (31.3%) with diffuse type. Patients with CLDN18.2 negative status exhibited a non-significant trend towards prolonged PFS (HR: 1.25; 95% CI: 0.98-1.61; p = 0.07; I2=18%) and a significant prolonged OS (HR: 1.20; 95% CI: 1.07-1.34; p < 0.01; I2=37%) when compared to CLDN18.2-positive patients.

CONCLUSION

Our findings establish CLDN18.2 as a robust negative prognostic indicator for overall survival in GC patients. While its impact on PFS was not statistically significant, the association with OS suggests CLDN18.2 may serve as a marker for complex biological processes underlying tumor advancement.

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.

Systemic Therapy of Gastric Cancer-State of the Art and Future Perspectives

Background: The prognosis of patients diagnosed with locally advanced and metastatic gastric and esophago-gastric junction cancer is critical. The optimal choice of systemic therapy is essential to optimize survival outcomes. Methods: A comprehensive literature review via PubMed and analysis of major oncology congresses (European Society for Medical Oncology and American Society of Clinical Oncology websites) were conducted to ascertain the current status and latest developments in the systemic treatment of patients with localized or advanced gastric and esophago-gastric junction adenocarcinoma. Results: While neoadjuvant and perioperative chemotherapy for localized tumor stages is the preferred approach in the Western Hemisphere, adjuvant chemotherapy remains the preferred course of action in East Asia. The administration of chemotherapy, typically in the form of combinations comprising platinum and fluoropyrimidine compounds in combination with docetaxel, represents a standard of care. Investigations are underway into the potential of immunotherapy and other biologically targeted agents in the perioperative setting. To select the most appropriate therapy for advanced gastric cancer, including adenocarcinoma of the esophago-gastric junction, it is essential to determine biomarkers such as HER2 expression, PD-L1 combined positive score (CPS) (combined positive score), Claudin 18.2, and microsatellite instability (MSI). In the present clinical context, the standard first-line therapy is a combination of fluoropyrimidine and a platinum derivative. The selection of chemotherapy in combination with antibodies is contingent upon the specific biomarker under consideration. Conclusions: This article reviews the current state of the art based on recent clinical trial results and provides an outlook on the future of systemic therapy.

Molecular genetic analysis of colorectal carcinoma with an aggressive extraintestinal immunohistochemical phenotype

Colorectal cancer (CRC) is a leading global cause of illness and death. There is a need for identification of better prognostic markers beyond traditional clinical variables like grade and stage. Previous research revealed that abnormal expression of cytokeratin 7 (CK7) and loss of the intestinal-specific Special AT-rich sequence-binding protein 2 (SATB2) are linked to poor CRC prognosis. This study aimed to explore these markers' prognostic significance alongside two extraintestinal mucins (MUC5AC, MUC6), claudin 18, and MUC4 in 285 CRC cases using immunohistochemistry on tissue microarrays (TMAs). CK7 expression and SATB2-loss were associated with MUC5AC, MUC6, and claudin 18 positivity. These findings suggest a distinct "non-intestinal" immunohistochemical profile in CRC, often right-sided, SATB2-low, with atypical expression of CK7 and non-colorectal mucins (MUC5AC, MUC6). Strong MUC4 expression negatively impacted cancer-specific survival (hazard ratio = 2.7, p = 0.044). Genetic analysis via next-generation sequencing (NGS) in CK7 + CRCs and those with high MUC4 expression revealed prevalent mutations in TP53, APC, BRAF, KRAS, PIK3CA, FBXW7, and SMAD4, consistent with known CRC mutation patterns. NGS also identified druggable variants in BRAF, PIK3CA, and KRAS. CK7 + tumors showed intriguingly common (31.6%) BRAF V600E mutations corelating with poor prognosis, compared to the frequency described in the literature and databases. Further research on larger cohorts with a non-colorectal immunophenotype and high MUC4 expression is needed.

Expression and Targeted Application of Claudins Family in Hepatobiliary and Pancreatic Diseases

Hepatobiliary and pancreatic diseases are becoming increasingly common worldwide and associated cancers are prone to recurrence and metastasis. For a more accurate treatment, new therapeutic strategies are urgently needed. The claudins (CLDN) family comprises a class of membrane proteins that are the main components of tight junctions, and are essential for forming intercellular barriers and maintaining cellular polarity. In mammals, the claudin family contains at least 27 transmembrane proteins and plays a major role in mediating cell adhesion and paracellular permeability. Multiple claudin proteins are altered in various cancers, including gastric cancer (GC), esophageal cancer (EC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), colorectal cancer (CRC) and breast cancer (BC). An increasing number of studies have shown that claudins are closely associated with the occurrence and development of hepatobiliary and pancreatic diseases. Interestingly, claudin proteins exhibit different effects on cancer progression in different tumor tissues, including tumor suppression and promotion. In addition, various claudin proteins are currently being studied as potential diagnostic and therapeutic targets, including claudin-3, claudin-4, claudin-18.2, etc. In this article, the functional phenotype, molecular mechanism, and targeted application of the claudin family in hepatobiliary and pancreatic diseases are reviewed, with an emphasis on claudin-1, claudin-4, claudin-7 and claudin-18.2, and the current situation and future prospects are proposed.

Unveiling promising targets in gastric cancer therapy: A comprehensive review

Gastric cancer (GC) poses a significant global health challenge, ranking fifth in incidence and third in mortality among all malignancies worldwide. Its insidious onset, aggressive growth, proclivity for metastasis, and limited treatment options have contributed to its high fatality rate. Traditional approaches for GC treatment primarily involve surgery and chemotherapy. However, there is growing interest in targeted therapies and immunotherapies. This comprehensive review highlights recent advancements in GC targeted therapy and immunotherapy. It delves into the mechanisms of various strategies, underscoring their potential in GC treatment. Additionally, the review evaluates the efficacy and safety of relevant clinical trials. Despite the benefits observed in numerous advanced GC patients with targeted therapies and immunotherapies, challenges persist. We discuss pertinent strategies to overcome these challenges, thereby providing a solid foundation for enhancing the clinical effectiveness of targeted therapies and immunotherapies.

CMG901, a Claudin18.2-specific antibody-drug conjugate, for the treatment of solid tumors

Claudin18.2 has been recently recognized as a potential therapeutic target for gastric/gastroesophageal junction or pancreatic cancer. Here, we develop a Claudin18.2-directed antibody-drug conjugate (ADC), CMG901, with a potent microtubule-targeting agent MMAE (monomethyl auristatin E) and evaluate its preclinical profiles. In vitro studies show that CMG901 binds specifically to Claudin18.2 on the cell surface and kills tumor cells through direct cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and bystander killing activity. In vivo pharmacological studies show significant antitumor activity in patient-derived xenograft (PDX) models. Toxicity studies show that the major adverse effects related to CMG901 are reversible hematopoietic changes attributed to MMAE. The highest non-severely toxic dose (HNSTD) is 6 mg/kg in cynomolgus monkeys and 10 mg/kg in rats once every 3 weeks. CMG901's favorable preclinical profile supports its entry into the human clinical study. CMG901 is currently under phase 3 investigation in patients with advanced gastric/gastroesophageal junction adenocarcinoma expressing Claudin18.2 (NCT06346392).

New therapeutic target molecules for gastric and gastroesophageal junction cancer

Molecularly targeted therapy for receptor tyrosine kinases (RTKs) has faced limitations in gastric and gastroesophageal junction (G/GEJ) cancer except for HER2-targeted agents, possibly due to inappropriate assay selection that has hindered identification of sensitive patients, in addition to coexisting genetic abnormalities as well as intratumoral heterogeneity. Immunohistochemistry of RTKs has, thus, proved largely unsuccessful for patient selection, and detection of RTK gene amplification as a true oncogenic driver is problematic given the small numbers of affected individuals. FGFR2 amplification is associated with poor prognosis in G/GEJ cancer, and immunohistochemistry of the FGFR2b protein isoform has proved effective for the detection of such FGFR2-dependent tumors. Phase III and Ib/III trials of the FGFR2-targeted antibody bemarituzumab for G/GEJ cancer overexpressing FGFR2b are ongoing based on the promising result in a phase II trial, especially in cases with an FGFR2b positivity of ≥ 10%. Challenges to EGFR- and MET-targeted therapies are being tackled with antibody-drug conjugates (ADCs) and bispecific antibodies. CLDN18.2 is expressed in some G/GEJ tumors but lacks oncogenic driver potential, and the CLDN18.2-targeted antibody zolbetuximab prolonged the survival of CLDN18.2-positive G/GEJ cancer patients in phase III trials. Antibody-drug conjugates and ADCs that target CLDN18.2 are also being pursued for treatment of such patients. Similarly, targeting of nondriver molecules such as DKK1, TROP2, and CEACAM5 is under investigation in early-stage clinical trials. This shift in focus from target molecules with driver potential to markers for precise drug delivery should increase the number of possible targets in G/GEJ cancer.

HER2-low gastric cancer: is the subgroup targetable?

Therapeutic developments in the targeting of human epidermal growth factor receptor 2 (HER2)-expressing gastric cancer have followed the dramatic success of HER2-expressing breast cancer treatment, which has facilitated the expansion of indications for anti-HER2 agents to include not only conventional HER2-positive breast cancer, but also HER2-low and HER2-ultralow subgroups. The targetability of HER2-low gastric cancer, however, has yet to be established. Hence, further studies are needed to comprehensively understand the clinicopathological features, specific gene alterations, and distinct tumor immune microenvironment of HER2-low gastric cancer and compare them with those for HER2-positive or -negative gastric cancer. Antibody-drug conjugates for HER2 play an important role in making HER2-low gastric cancer targetable. In this context, a deeper understanding of the novel anti-HER2 agents, including antibody-drug conjugates, bispecific T-cell engager antibodies, and a combination of these agents, as well as new forms of immunomodulatory agents are also required. Redefining and re-categorizing HER2 status through not only immunohistochemistry/fluorescence in situ hybridization but also evaluating ERRB2 copy number gain or protein overexpression levels measured using DNA or RNA sequencing might be helpful for identifying populations with HER2-expressing tumors who would ideally benefit from anti-HER2 treatment. The current paper reviewed recent clinical trials, focusing particularly on HER2-low gastric cancer together with basic/translational findings, and discuss perspectives on further therapeutic development in the treatment of this distinct subgroup.

Global prevalence of claudin 18 isoform 2 in tumors of patients with locally advanced unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma

BACKGROUND

Limited data exist for global prevalence of claudin 18 isoform 2 (CLDN18.2) positivity and association of CLDN18.2 status with clinical and tumor characteristics in patients with locally advanced (LA) unresectable or metastatic gastric or gastroesophageal junction (mG/GEJ) adenocarcinoma. We report prevalence of CLDN18.2 positivity (phase 3; SPOTLIGHT, NCT03504397; GLOW, NCT03653507) and concordance of CLDN18.2 status between a subset of pair-matched tumor samples (phase 2, ILUSTRO, NCT03505320; phase 1, NCT03528629) from clinical studies of zolbetuximab.

METHODS

Tumor samples from patients with LA unresectable or mG/GEJ adenocarcinoma were tested for CLDN18.2 status by immunohistochemistry. Human epidermal growth factor receptor 2 (HER2) expression was tested per central or local assessment.

RESULTS

Across SPOTLIGHT and GLOW, the prevalence of CLDN18.2 positivity (≥ 75% of tumor cells demonstrating moderate-to-strong membranous CLDN18 staining) was 38.4%. Prevalence was similar in gastric versus GEJ adenocarcinoma samples and regardless of collection method (biopsy versus resection) or collection site (primary versus metastatic). CLDN18.2 positivity was most prevalent in patients with diffuse-type tumors. In ILUSTRO and the phase 1 study, concordance of CLDN18.2 positivity was 61.1% between archival (i.e., any time before treatment) and baseline (i.e., ≤ 3 months before first treatment) samples, and concordance of any CLDN18 staining (≥ 1% of tumor cells demonstrating moderate-to-strong membranous CLDN18 staining) was 88.9%.

CONCLUSIONS

CLDN18.2 was a highly prevalent biomarker in patients with HER2-negative, LA unresectable or mG/GEJ adenocarcinoma. CLDN18.2 positivity remained relatively stable over time in many patients. Biomarker testing for CLDN18.2 should be considered in standard clinical practice in these patients.

The impact of CLDN18.2 expression on effector cells mediating antibody-dependent cellular cytotoxicity in gastric cancer

Activating antibody-dependent cellular cytotoxicity (ADCC) by targeting claudin-18 isoform 2 (CLDN18.2) using zolbetuximab, a monoclonal antibody against CLDN18.2, has been considered a promising novel therapeutic strategy for gastric cancer (GC). However, the impact of CLDN18.2 expression on natural killer (NK) cells and monocytes/macrophages-crucial effector cells of ADCC-in GC has not been fully investigated. In the present study, we assessed the impact of CLDN18.2 expression on clinical outcomes, molecular features, and the frequencies of tumor-infiltrating NK cells and macrophages, as well as peripheral blood NK cells and monocytes, in GC by analyzing our own GC cohorts. The expression of CLDN18.2 did not significantly impact clinical outcomes of GC patients, while it was significantly and positively associated with Epstein-Barr virus (EBV) status and PD-L1 expression. The frequencies of tumor-infiltrating NK cells and macrophages, as well as peripheral blood NK cells and monocytes, were comparable between CLDN18.2-positive and CLDN18.2-negative GCs. Importantly, both CLDN18.2 expression and the number of tumor-infiltrating NK cells were significantly higher in EBV-associated GC compared to other molecular subtypes. Our findings support the effectiveness of zolbetuximab in CLDN18.2-positive GC, and offer a novel insight into the treatment of this cancer type, highlighting its potential effectiveness for CLDN18.2-positive/EBV-associated GC.

Claudin-18.2 Immunohistochemical Evaluation in Gastric and Gastroesophageal Junction Adenocarcinomas to Direct Targeted Therapy: A Practical Approach

Claudin-18.2 (CLDN18.2) expression evaluated by immunohistochemistry is a new biomarker for gastric and gastroesophageal junction adenocarcinomas that will soon have market authorization for implementation into routine clinical practice. Despite successful testing in the setting of clinical trials, no specific practical testing guidelines have been proposed. Several preanalytical and analytical variables may interfere with adequate CLDN18.2 staining interpretation; thus, this article provides practical guidance on CLDN18.2 testing and scoring in gastric and gastroesophageal junction adenocarcinomas to identify patients who may respond to targeted therapy with monoclonal antibodies directed against CLDN18.2. Based on available data, moderate to strong (2+/3+) membrane staining in ≥75% of adenocarcinoma cells is the proposed cutoff for clinical use of monoclonal antibody anti-CLDN18.2 (zolbetuximab).

Claudin18.2-specific CAR T cells in gastrointestinal cancers: phase 1 trial final results

Claudin18.2 (CLDN18.2) is highly expressed with the development of various malignant tumors, especially gastrointestinal cancers, and is emerging as a new target for cancer treatment. Satricabtagene autoleucel (satri-cel)/CT041 is an autologous chimeric antigen receptor (CAR) T cell targeting CLDN18.2, and the interim results of the CT041-CG4006 trial were reported in June 2022. Here we present the final results of this single-arm, open-label, phase 1 trial, which evaluated the safety and efficacy of satri-cel in patients with CLDN18.2-positive advanced gastrointestinal cancers. This trial included a dose-escalation stage (n = 15) and a dose-expansion stage in four different cohorts (total n = 83): cohort 1, satri-cel monotherapy in 61 patients with standard chemotherapy-refractory gastrointestinal cancers; cohort 2, satri-cel plus anti-PD-1 therapy in 15 patients with standard chemotherapy-refractory gastrointestinal cancers; cohort 3, satri-cel as sequential treatment after first-line therapy in five patients with gastrointestinal cancers; and cohort 4, satri-cel monotherapy in two patients with anti-CLDN18.2 monoclonal antibody-refractory gastric cancer. The primary endpoint was safety; secondary endpoints included efficacy, pharmacokinetics and immunogenicity. A total of 98 patients received satri-cel infusion, among whom 89 were dosed with 2.5 × 108, six with 3.75 × 108 and three with 5.0 × 108 CAR T cells. Median follow-up was 32.4 months (95% confidence interval (CI): 27.3, 36.5) since apheresis. No dose-limiting toxicities, treatment-related deaths or immune effector cell-associated neurotoxicity syndrome were reported. Cytokine release syndrome occurred in 96.9% of patients, all classified as grade 1-2. Gastric mucosal injuries were identified in eight (8.2%) patients. The overall response rate and disease control rate in all 98 patients were 38.8% and 91.8%, respectively, and the median progression-free survival and overall survival were 4.4 months (95% CI: 3.7, 6.6) and 8.8 months (95% CI: 7.1, 10.2), respectively. Satri-cel demonstrates therapeutic potential with a manageable safety profile in patients with CLDN18.2-positive advanced gastrointestinal cancer. ClinicalTrials.gov identifier: NCT03874897 .

Heterogeneity of claudin 18.2 expression in metastatic gastric cancer

Claudin 18.2 has emerged as a viable therapeutic target in gastric cancer (GC), but little is known about the heterogeneity of its expression in GC. This study investigated the heterogeneity of claudin 18.2 expression in 166 patients with metastatic GC whose surgical or paired primary-metastatic specimens were available. The prevalence of claudin 18.2 positivity (moderate-to-strong expression in ≥ 75% by the 43-14A clone) was 47.0%. Claudin 18.2-positive tumors exhibited more frequent peritoneal metastasis and a lower incidence of hepatic and distant lymph node involvement. Survival outcomes were comparable between patients with claudin 18.2-positive and -negative tumors. Intratumoral heterogeneity was noted in 38.5% of surgical specimens. Paired primary-metastatic site analysis revealed that 25.2% of patients had discordant results for claudin 18.2 positivity. Across different metastatic organ categories, peritoneal lesions showed the highest positivity rate (44.3%) and positive concordance rate (31.4%), whereas liver lesions had the lowest positivity rate (17.9%) and concordance rate (12.8%). In conclusion, claudin 18.2 expression exhibits intratumoral and intrapatient spatial heterogeneity in metastatic GC. Claudin 18.2 positivity is associated with more frequent peritoneal metastasis, and peritoneal lesions are more likely to have positively concordant claudin 18.2 results with the primary site than other metastatic sites.

Biomarker-oriented chemo-immunotherapy for advanced gastric cancer

The biomarker-oriented chemo-immunotherapy is useful and promising in the development of new anticancer agents, since the responders can be enriched by selecting patients with biomarkers. Compared to colorectal and lung cancers, the development of biomarker-driven molecular-targeted therapeutics for gastric cancers has been straggled. However, several new biomarkers in gastric cancers have been discovered and clinical trials in enrichment design with certain biomarkers have been conducted. Therefore, there are currently several treatment options to treat gastric cancer patients based on individual biomarker-oriented strategies. In the present review, we describe the useful biomarkers in gastric cancer, with focusing on HER2, PD-L1, and Claudin18.2, in relation to their clinical significance and associated targeted agents.

Potential diagnostic, prognostic, and predictive biomarkers of gastric cancer

Background

Gastric cancer (GC), a malignant epithelial tumor, is the fourth leading cause of cancer-related death worldwide. Therapeutic strategies for GC, despite the biggest challenges, can significantly improve survival rates through early detection and effective screening methods.

Aim

To provide brief information on the necessity of multiple specific diagnostic, prognostic, and predictive markers for GC.

Methods

This review was conducted using a variety of search engines, including PubMed Central, Scopus, Web of Science, Google Scholar, and others.

Results

Some potential biomarkers that provide essential information include circulating tumor cells (CTCs), DNA methylation, claudin 18.2, fibroblast growth factor receptor 2 (FGFR2), long noncoding RNAs (lncRNAs), cell-free DNA (cfDNA), microRNAs, and serum pepsinogens.

Conclusion

Multiple tumor markers are essential for screening, tumor identification, staging, prognostic assessment, and monitoring recurrence after therapy due to the absence of a single tumor indicator for diagnosing, prognosticating, and predicting GC.

Claudin-18 status and its correlation with HER2 and PD-L1 expression in gastric cancer with peritoneal dissemination

BACKGROUND

Gastric cancer with peritoneal dissemination (PD) has a dismal prognosis, and current treatments have shown little efficacy. CLDN18.2-targeted therapies have shown promising efficacy against gastric cancers that express high levels of CLDN18. Because of the limited information regarding CLDN18.2 status in PD, we analyzed PD-positive gastric cancers for CLDN18 status in both primary and PD, along with HER2 and PD-L1 combined positive score (CPS).

METHODS

Immunohistochemical analyses were performed on 84 gastric cancer cases using paired primary and PD tissue samples.

RESULTS

At 40% cut-off, CLDN18 was positive in 57% (48/84) primary tumors and in 44% (37/84) PDs. At 75% cut-off, 28.6% (24/84) primary tumors and 20.2% (17/84) PDs were CLDN18-positive. The concordance rate between primary tumors and PD was 79.8% at 40% cut-off and 75% at 75% cut-off. When comparing biopsy and surgical specimens, the concordance rates were 87.5% at 40% cut-off and 81.3% at 75% cut-off. Within a tumor, the superficial area tended to have a higher CLDN18-positive rate than the invasive front (P = 0.001). Although HER2 -positivity was only 11.9% in this cohort, CLDN18 positivity in HER2-negative tumors (n = 74) was relatively high: 60.8% at 40% cut-off and 28.4% at 75% cut-off. Among double-negative (HER2 - and PD-L1 CPS < 1) tumors, CLDN18 positivity was 67.6% at 40% cut-off and 26.5% at 75% cut-off.

CONCLUSIONS

CLDN18 expression is generally maintained in PD and is relatively high even in double-negative tumors, making it a promising therapeutic target for PD-positive gastric cancer.

Progress of Clinical Studies Targeting Claudin18.2 for the Treatment of Gastric Cancer

Claudin18.2 is a tight junction protein, highly selective, generally expressed only in normal gastric mucosal epithelial cells, which can effectively maintain the polarity of epithelial and endothelial cells, thus effectively regulating the permeability and conductance of the paracellular pathway. Abnormal expression of Claudin18.2 can occur in various primary malignant tumors, especially gastrointestinal tumors, and even in metastatic foci. It regulates its expression by activating the aPKC/MAPK/AP-1 pathway, and therefore, the Claudin18.2 protein is a pan-cancer target expressed in primary and metastatic lesions in human cancer types. Zolbetuximab (IMAB362), an antibody specific for Claudin18.2, has been successfully tested in a phase III clinical trial, and the results of the study showed that combining Zolbetuximab with chemotherapy notably extends patients' survival and is expected to be a potential first-line treatment for patients with Claudin18.2(+)/HER-2(-) gastric cancer. Here, we systematically describe the biological properties and oncogenic effects of Claudin18.2, centering on its clinical-pathological aspects and the progress of drug studies in gastric cancer, which can help to further explore its clinical value.

Molecular Landscape and Clinical Implication of CCNE1-amplified Esophagogastric Cancer

Cyclin E overexpression as a result of CCNE1 amplification is a critical driver of genomic instability in gastric cancer, but its clinical implication is largely unknown. Thus, we integrated genomic, transcriptomic, and immune profiling analysis of 7,083 esophagogastric tumors and investigated the impact of CCNE1 amplification on molecular features and treatment outcomes. We identified CCNE1 amplification in 6.2% of esophageal adenocarcinoma samples, 7.0% of esophagogastric junction carcinoma, 4.2% of gastric adenocarcinoma samples, and 0.8% of esophageal squamous cell carcinoma. Metastatic sites such as lymph node and liver showed an increased frequency of CCNE1 amplification relative to primary tumors. Consistent with a chromosomal instability phenotype, CCNE1 amplification was associated with decreased CDH1 mutation and increased TP53 mutation and ERBB2 amplification. We observed no differences in immune biomarkers such as PD-L1 expression and tumor mutational burden comparing CCNE1-amplified and nonamplified tumors, although CCNE1 amplification was associated with changes in immune populations such as decreased B cells and increased M1 macrophages from transcriptional analysis. Real-world survival analysis demonstrated that patients with CCNE1-amplified gastric cancer had worse survival after trastuzumab for HER2-positive tumors, but better survival after immunotherapy. These data suggest that CCNE1-amplified gastric cancer has a distinct molecular and immune profile with important therapeutic implications, and therefore further investigation of CCNE1 amplification as a predictive biomarker is warranted.

SIGNIFICANCE

Advanced gastric cancer has a relatively dismal outcome with a 5-year overall survival of less than 10%. Furthermore, while comprehensive molecular analyses have established molecular subtypes within gastric cancers, biomarkers of clinical relevance in this cancer type are lacking. Overall, this study demonstrates that CCNE1 amplification is associated with a distinct molecular profile in gastric cancer and may impact response to therapy, including targeted therapy and/or immunotherapy.

68Ga-NC-BCH Whole-Body PET Imaging Rapidly Targets Claudin18.2 in Lesions in Gastrointestinal Cancer Patients

68Ga-labeled nanobody (68Ga-NC-BCH) is a single-domain antibody-based PET imaging agent. We conducted a first-in-humans study of 68Ga-NC-BCH for PET to determine its in vivo biodistribution, metabolism, radiation dosimetry, safety, and potential for quantifying claudin-18 isoform 2 (CLDN18.2) expression in gastrointestinal cancer patients. Methods: Initially, we synthesized the probe 68Ga-NC-BCH and performed preclinical evaluations on human gastric adenocarcinoma cell lines and xenograft mouse models. Next, we performed a translational study with a pilot cohort of patients with advanced gastrointestinal cancer on a total-body PET/CT scanner. Radiopharmaceutical biodistribution, radiation dosimetry, and the relationship between tumor uptake and CLDN18.2 expression were evaluated. Results: 68Ga-NC-BCH was stably prepared and demonstrated good radiochemical properties. According to preclinical evaluation,68Ga-NC-BCH exhibited rapid blood clearance, high affinity for CLDN18.2, and high specific uptake in CLDN18.2-positive cells and xenograft mouse models. 68Ga-NC-BCH displayed high uptake in the stomach and kidney and slight uptake in the pancreas. Compared with 18F-FDG, 68Ga-NC-BCH showed significant differences in uptake in lesions with different levels of CLDN18.2 expression. Conclusion: A clear correlation was detected between PET SUV and CLDN18.2 expression, suggesting that 68Ga-NC-BCH PET could be used as a companion diagnostic tool for optimizing treatments that target CLDN18.2 in tumors.

Current and Future Biomarkers in Esophagogastric Adenocarcinoma

PURPOSE

Biomarker-based therapies have shown improved patient outcomes across various cancer types. The purpose of this review to summarize our knowledge of current and future biomarkers in esophagogastric adenocarcinoma (EGA).

METHODS

In this publication, we will review current standard biomarkers in patients with upper GI cancers. We will also discuss novel biomarkers that are under investigations and their associated therapies that are currently in clinical trials.

RESULTS

EGAa are a group of heterogeneous diseases, both anatomically and molecularly. There are several established biomarkers (HER2, PD-L1, microsattelite instability or mismatch repair protein expression) that allow for individualized treatments for patients with these cancers. There are also several emerging biomarkers for EGA, some of which have clinically relevant associated therapies. Claudin 18.2 is the furthest along among these. Anti-claudin antibody, zolbetuximab, improved overall survival in biomarker select patients with advanced GEA in two phase 3 studies. Other novel biomarkers, such as FGFR2b and DKN01, are also in the process of validation, and treatments based on the presence of these biomarkers are currently in clinical studies.

CONCLUSION

Ongoing efforts to identify novel biomarkers in EGA have led to enhanced subclassification of upper GI cancers. These advances, coupled with the strategic application of targeted therapies and immunotherapy when appropriate, hold promise to further improve patients outcomes.

Incorporating Molecular Data Into Treatment Decision Making in Gastroesophageal and Pancreaticobiliary Cancers: Timing and Strategies

Gastroesophageal (GE) and pancreatobiliary (PB) cancers represent a significant clinical challenge. In this context, it is critical to understand the key molecular targets within these malignancies including how they are assayed for as well as the clinical actionability of these targets. Integrating biomarkers into the standard of care presents a critical avenue for refining treatment paradigms. This review aims to explore these complexities, offering insights into the optimal sequencing of chemotherapy and targeted therapies and their utility in the management of GE and PB cancers. The timely integration of promising investigational therapies into clinical practice has broader implications around strategies for future clinical trial designs, which would pave the way for advancements in the management of GE and PB cancers. This review provides guidance in navigating the evolving landscape of GE and PB cancer care, which ultimately will drive forward progress in the field and lead to improved patient outcomes.

Targeted Agents in Esophagogastric Cancer Beyond Human Epidermal Growth Factor Receptor-2

Gastroesophageal cancers are highly diverse tumors in terms of their anatomic and molecular characteristics, making drug development challenging. Recent advancements in understanding the molecular profiles of these cancers have led to the identification of several new biomarkers. Ongoing clinical trials are investigating new targeted agents with promising results. CLDN18.2 has emerged as a biomarker with established activity of associated targeted therapies. Other targeted agents, such as bemarituzumab and DKN-01, are under active investigation. As new agents are incorporated into the treatment continuum, the questions of biomarker overlap, tumor heterogeneity, and toxicity management will need to be addressed.

Molecular alterations in claudin 18 suppressed and non-suppressed gastric adenocarcinomas to guide targeted therapies

BACKGROUND

Gastric adenocarcinoma represents an aggressive type of cancer and an important cause of cancer mortality. Progress in gastric cancer therapeutics has resulted from a better understanding of the molecular pathogenesis of the disease and introduction of targeted therapies, but most gastric cancer patients still rely on non-targeted chemotherapy as the mainstay of treatment for advanced disease.

METHODS

An analysis of publicly available series from The Cancer Genome Atlas (TCGA) gastric cancer cohort was undertaken to delineate the clinical and genomic landscape of gastric cancers with suppressed expression of claudin 18 compared with cancers with non-suppressed claudin 18. Claudin 18 suppressed cancers were defined as having an mRNA expression z-score relative to normal samples (log RNA Seq V2) of less than -1. Claudin 18 non-suppressed cancers were defined as having an mRNA expression z-score relative to normal samples (log RNA Seq V2) above 0.5.

RESULTS

Gastric cancers with claudin 18 mRNA suppression represented 7.7% of the gastric adenocarcinomas of TCGA cohort, while non-suppressed cancers represented 46.6% of the cases. The two groups did not differ in clinical and genomic characteristics, such as mean age, histology, grade, and stage. The mutation landscape of claudin 18 suppressed cases included high mutation rates of TP53, of genes of the WNT/β-catenin pathway and of ubiquitin ligase FBXW7. Moreover, a subset of both claudin 18 suppressed and non-suppressed cancers displayed mutations in Mismatch Repair (MMR) associated genes or a high tumor mutation burden (TMB). At the mRNA expression level, claudin 18 suppressed gastric cancers showed up-regulation of EMT core transcription factor Snail 2 and down-regulation of genes of HLA cluster. The survival of gastric cancer patients with claudin 18 mRNA suppression was not significantly different compared with patients with non-suppressed claudin 18.

CONCLUSION

Sub-sets of gastric cancers with claudin 18 mRNA suppression displayed characteristics of potential therapeutic interest, such as mutations in WNT and PI3K pathways and MMR defects. These may guide the development of alternative targeted therapies, in this sub-set of gastric cancers which are not candidates for claudin 18 targeting therapies.

Claudin 18.2 as a novel therapeutic target

Claudin 18.2, a tight-junction molecule predominantly found in the nonmalignant gastric epithelium, becomes accessible on the tumour cell surface during malignant transformation, thereby providing an appealing target for cancer therapy. Data from two phase III trials testing the anti-claudin 18.2 antibody zolbetuximab have established claudin 18.2-positive advanced-stage gastric cancers as an independent therapeutic subset that derives benefit from the addition of this agent to chemotherapy. This development has substantially increased the percentage of patients eligible for targeted therapy. Furthermore, newer treatments, such as high-affinity monoclonal antibodies, bispecific antibodies, chimeric antigen receptor T cells and antibody-drug conjugates capable of bystander killing effects, have shown considerable promise in patients with claudin 18.2-expressing gastric cancers. This new development has resulted from drug developers moving beyond traditional targets, such as driver gene alterations or growth factors. In this Review, we highlight the biological rationale and explore the clinical activity of therapies that target claudin 18.2 in patients with advanced-stage gastric cancer and explore the potential for expansion of claudin 18.2-targeted therapies to patients with other claudin 18.2-positive solid tumours.

Whole-transcriptome sequencing in advanced gastric or gastroesophageal cancer: A deep dive into its clinical potential

Advanced gastric and gastroesophageal junction cancers (GC/GEJCs) harbor diverse molecular signatures, highlighting the need for intricate evaluations to identify potential therapeutic targets. Although whole-transcriptome sequencing (WTS) has emerged as a useful tool for understanding these molecular intricacies, its clinical implications have yet to be fully elucidated. This study evaluated the correlation between immunohistochemistry (IHC) and WTS, compared their clinical significance, and identified potential therapeutic targets undetectable through IHC alone. We enrolled 140 patients with advanced GC/GEJC and assessed them using IHC for six pivotal biomarkers: claudin-18 (CLDN18), human epidermal growth factor receptor 2 (HER2), multiple receptor tyrosine kinases (RTKs), and programmed death ligand 1 (PD-L1). Concurrently, WTS was employed as part of the analyses in MONSTAR-SCREEN-2, a multicenter multiomics study. IHC analysis revealed 16.4% HER2, 39.3% CLDN18 (2+/3 + ≥75%), and 15.8% PD-L1 (combined positive score ≥ 10) positivity, among other molecular markers. Significant correlations were observed between IHC and WTS for all six pivotal biomarkers. Among nineteen HER2 IHC-positive patients treated with anti-HER2 therapeutics, ERBB2 status in WTS was significantly associated with progression-free survival (ERBB2-high vs. -low: median 9.0 vs. 5.6 months, log-rank p = 0.046). IHC-based molecular profiling revealed significantly high expression of CLDN18 in RTK-negative patients, with 78.4% positive for either CLDN18 or PD-L1. Additionally, WTS revealed elevated expression of pivotal biomarkers in patients displaying negative targetable biomarkers via IHC. Our findings highlighted the significant correlation between IHC and WTS, reinforcing the clinical utility of WTS. A subset with IHC-negative but WTS-positive status may benefit from specific biomarker-targeted therapies.

Ten-Year Follow-Up After Chemotherapy and Conversion Surgery for Human Epidermal Growth Factor Receptor 2-Positive Stage IV Esophagogastric Junction Cancer With a Pathological Complete Response: A Case Report

Recent reports have focused on the usefulness of conversion surgery, in which chemotherapy is given to patients with unresectable advanced gastric cancer (GC), and radical surgery is subsequently performed if resection becomes possible; however, no consensus has been reached regarding the usefulness of this strategy. We report on a 74-year-old man who was diagnosed with esophagogastric junction cancer (T3N3M1 (LYM): stage IV). Chemotherapy was chosen and seven courses of S1 + cisplatin (SP) + trastuzumab (HCN) and two courses of S1 + HCN were administered. Approximately 10 months after the start of chemotherapy, the tumor had almost disappeared and we therefore decided to perform conversion surgery. Pathologic examination of the specimen and dissected lymph nodes showed no cancer. Postoperatively, the patient underwent chemotherapy until the second postoperative year, and no metastasis or recurrence was observed for nine years after surgery. Conversion surgery after chemotherapy resulted in recurrence-free survival in this case; however, further studies are needed to elucidate the effect of surgery after chemotherapy for patients with stage IV GC, as chemotherapy continues to evolve.

Retrospective Study of Claudin 18 Isoform 2 Prevalence and Prognostic Association in Gastric and Gastroesophageal Junction Adenocarcinoma

PURPOSE

Claudin 18 isoform 2 (CLDN18.2) is an emerging biomarker and therapeutic target in gastric and gastroesophageal junction (G/GEJ) adenocarcinoma. This study aimed to obtain deeper understanding of CLDN18.2 positivity patterns, prognostic implications, and associations with various demographic, clinical, and molecular characteristics in G/GEJ adenocarcinoma.

METHODS

Archived tumor tissue samples from 304 patients with G/GEJ adenocarcinoma in the United States were assessed for CLDN18.2 positivity by immunohistochemistry. CLDN18.2 positivity was defined as ≥50% or ≥75% of tumor cells with CLDN18 staining intensity ≥2+. CLDN18.2 positivity patterns were analyzed for association with prognosis and clinicopathologic/demographic characteristics. Where possible, CLDN18.2 positivity was analyzed for matched tissue samples to assess concordance between primary and metastatic tumors and concordance before and after chemotherapy.

RESULTS

The overall prevalence of CLDN18.2-positive tumors (with ≥75% cutoff) was 44.4% (n = 135 of 304). CLDN18.2-positive tumors had a prevalence of 51.4% (n = 91 of 177) in gastric and 34.6% (n = 44 of 127) in GEJ adenocarcinoma. With a ≥50% cutoff, the prevalence of CLDN18.2-positive tumors was 64.4% (n = 114 of 177) in gastric adenocarcinoma and 44.9% (n = 57 of 127) in GEJ adenocarcinoma. There was no association between overall survival and CLDN18.2 positivity using either threshold. Statistically significant associations were noted between CLDN18.2 positivity and sex, histologic type of G/GEJ adenocarcinoma, and adenocarcinoma subtype (≥75% cutoff), and metastasis site and tumor grade (≥50% cutoff). The overall concordance of CLDN18.2 positivity (≥75% cutoff) was 73% (27 of 37) for matched primary versus metastatic tumor samples and 74% (29 of 39) for matched samples before and after chemotherapy.

CONCLUSION

This study demonstrated that CLDN18.2 positivity did not correlate with survival in G/GEJ adenocarcinoma, consistent with published data. On the basis of matched sample analysis, CLDN18.2 appears to demonstrate >70% concordance as a biomarker. Observed correlations with certain patient/tumor characteristics warrant further study.

High Expression of CLDN 18.2 is Associated with Poor Disease-Free Survival of HER-2 Positive Gastric Cancer

Background

Anti-claudin (CLDN) 18.2 therapy has been proven to be effective in treating advanced gastric cancer with negative human epidermal growth factor receptor 2 (HER-2). This study purposed to investigate the relationship of CLDN 18.2 expression with prognosis of HER-2-positive gastric cancer patients.

Objective

To investigate the expression of claudin (CLDN) 18.2 in Human epidermal growth factor receptor 2 (HER-2) positive gastric cancer patients after radical resection and its relationship with gastric cancer prognosis.

Methods

A total of 55 postoperative HER-2-positive gastric cancer patients were included in this study. CLDN 18.2 protein was detected by immunohistochemistry, and detailed clinical and pathological information was collected. Factors considered potentially important in the univariate analysis were included in the multivariate analysis, which involved COX regression to find the independent prognostic factors affecting disease-free survival (DFS).

Results

Immunohistochemistry showed that different levels of CLDN 18.2 protein were expressed in HER-2 positive gastric cancer tissues, and the Chi-square analysis showed that the expression level of CLDN 18.2 was significantly correlated with the lymph node stage. Higher expression levels of CLDN 18.2 were found in patients with lymph node positivity and were associated with poor prognosis in HER-2-positive gastric cancer patients. Gastric cancer patients with low and high expressions of CLDN 18.2 had postoperative median DFS of 38.5 months (95% confidence interval (CI) 28.8-48.2 months) and 12.1 months (95% CI, 11.7-41.0 months), respectively.

Conclusion

High expression of CLDN 18.2 in HER-2 positive gastric cancer is associated with poor prognosis, and the optimal treatment mode for this population is worth exploring after the approval of anti-CLDN 18.2 drugs.

DR30318, a novel tri-specific T cell engager for Claudin 18.2 positive cancers immunotherapy

BACKGROUND

Claudin 18.2 (CLDN18.2) is a highly anticipated target for solid tumor therapy, especially in advanced gastric carcinoma and pancreatic carcinoma. The T cell engager targeting CLDN18.2 represents a compelling strategy for enhancing anti-cancer efficacy.

METHODS

Based on the in-house screened anti-CLDN18.2 VHH, we have developed a novel tri-specific T cell engager targeting CLDN18.2 for gastric and pancreatic cancer immunotherapy. This tri-specific antibody was designed with binding to CLDN18.2, human serum albumin (HSA) and CD3 on T cells.

RESULTS

The DR30318 demonstrated binding affinity to CLDN18.2, HSA and CD3, and exhibited T cell-dependent cellular cytotoxicity (TDCC) activity in vitro. Pharmacokinetic analysis revealed a half-life of 22.2-28.6 h in rodents and 41.8 h in cynomolgus monkeys, respectively. The administration of DR30318 resulted in a slight increase in the levels of IL-6 and C-reactive protein (CRP) in cynomolgus monkeys. Furthermore, after incubation with human PBMCs and CLDN18.2 expressing cells, DR30318 induced TDCC activity and the production of interleukin-6 (IL-6) and interferon-gamma (IFN-γ). Notably, DR30318 demonstrated significant tumor suppression effects on gastric cancer xenograft models NUGC4/hCLDN18.2 and pancreatic cancer xenograft model BxPC3/hCLDN18.2 without affecting the body weight of mice.

Predictive and prognostic biomarkers in gastrointestinal tract tumours

Tumours of the gastrointestinal tract represent nearly a quarter of all newly diagnosed tumours diagnosed in 2019. Various treatment modalities for gastrointestinal cancers exist, some of which may be guided by biomarkers. Biomarkers act as gauges of either normal or pathogenic processes or responses to an exposure or intervention. They come in many forms. This review explores established and potential molecular/immunohistochemical (IHC) predictive and prognostic biomarkers of the gastrointestinal tract.

Clinicopathological significance and immunotherapeutic outcome of claudin 18.2 expression in advanced gastric cancer: A retrospective study

Objective

Immunotherapeutic outcomes and clinical characteristics of claudin 18 isoform 2 positive (CLDN18.2-positive) gastric cancer (GC) vary in different clinical studies, making it difficult to optimize anti-CLDN18.2 therapy. We conducted a retrospective analysis to explore the association of CLDN18.2 expression with clinicopathological characteristics and immunotherapeutic outcomes in GC.

Methods

A total of 536 advanced GC patients from 2019 to 2021 in the CT041-CG4006 and CT041-ST-01 clinical trials were included in the analysis. CLDN18.2 expression on ≥40% of tumor cells (2+, 40%) and CLDN18.2 expression on ≥70% of tumor cells (2+, 70%) were considered the two levels of positively expressed GC. The clinicopathological characteristics and immunotherapy outcomes of GC patients were analyzed according to CLDN18.2 expression status.

Results

CLDN18.2 was expressed in 57.6% (cut-off: 2+, 40%) and 48.9% (cut-off: 2+, 70%) of patients. Programmed death-ligand 1 (PD-L1) and CLDN18.2 were co-expressed in 19.8% [combined positive score (CPS)≥1, CLDN18.2 (cut-off: 2+, 40%)] and 17.2% [CPS≥5, CLDN18.2 (cut-off: 2+, 70%)] of patients. CLDN18.2 expression positively correlated with younger age, female sex, non-gastroesophageal junction (non-GEJ), and diffuse phenotype (P<0.001). HER2 and PD-L1 expression were significantly lower in CLDN18.2-positive GC (both P<0.05). Uterine adnexa metastasis (P<0.001) was more frequent and liver metastasis (P<0.001) was less common in CLDN18.2-positive GC. Overall survival and immunotherapy-related progression-free survival (irPFS) were inferior in the CLDN18.2-positive group.

Conclusions

CLDN18.2-positive GC is associated with poor prognosis and worse immunotherapeutic outcomes. The combination of anti-CLDN18.2 therapy, anti-PD-L1/PD-1 therapy, and chemotherapy for GC requires further investigation.

Immune checkpoint inhibitors or anti-claudin 18.2 antibodies? A network meta-analysis for the optimized first-line therapy of HER2-negative gastric cancer

Background

Multiple anti-programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) inhibitors and zolbetuximab, an anti-claudin 18.2 antibody, have shown efficacy in the first-line treatment of HER2-negative gastric cancers. How to choose the best regimen remains an unsolved question.

Objectives

We aimed to conduct a comparative analysis of the therapeutic advantages between immunotherapy and anti-claudin-18.2-targeted therapies in the first-line treatment of HER2-negative, unresectable, or metastatic gastric cancers.

Design

Network meta-analysis was employed to systematically compare efficacy and safety data derived from various clinical trials.

Data sources and methods

We included phase III randomized controlled trials in PubMed, Embase, Web of Science, Cochrane Library, and major conference abstracts. Network meta-analysis was used to compare the efficacy of each first-line therapeutic agent and to indirectly compare immunotherapy with anti-claudin-18.2-targeted therapy.

Results

Eight trials comprising a total of 6455 patients were included. For the overall survival (OS) analysis, no statistically significant differences were observed between pembrolizumab [hazard ratios (HR) = 1.00, 95% CI: 0.94-1.07], sintilimab (HR = 0.99, 95% CI: 0.89-1.09), sugemalimab (HR = 0.98, 95% CI: 0.87-1.10), tislelizumab (HR = 0.97, 95% CI: 0.87-1.09), zolbetuximab (HR = 0.98, 95% CI: 0.91-1.07), and nivolumab (HR = 1.00). For the progression-free survival (PFS) analysis, no statistically significant differences were observed between pembrolizumab (HR = 1.00, 95% CI: 0.93-1.06), sintilimab (HR = 0.91, 95% CI: 0.83-1.00), sugemalimab (HR = 0.92, 95% CI: 0.84-1.02), tislelizumab (HR = 0.93, 95% CI: 0.84-1.03), zolbetuximab (HR = 0.96, 95% CI: 0.88-1.05), and nivolumab (HR = 1.00). For the overall response rate analysis, all regimens presented similar effects on ORR. In addition, anti-claudin-18.2-targeted therapies presented similar OS (HR = 0.99, 95% CI: 0.95-1.04) and PFS (HR = 1.01, 95% CI: 0.91-1.12) compared to immunotherapy, although their toxicity profiles were distinct.

Conclusions

Our network meta-analysis showed no significant difference in PFS, OS, or ORR between different checkpoint inhibitors or between immunotherapy and anti-claudin-18.2-targeted therapies in the first-line treatment of HER2-negative, unresectable, or metastatic gastric cancers.

Claudin 18.2 as a New Biomarker in Gastric Cancer-What Should We Know?

Gastric cancer (GC) remains a formidable global health challenge, ranking among the top-five causes of cancer-related deaths worldwide. The majority of patients face advanced stages at diagnosis, with a mere 6% five-year survival rate. First-line treatment for metastatic GC typically involves a fluoropyrimidine and platinum agent combination; yet, predictive molecular markers have proven elusive. This review navigates the evolving landscape of GC biomarkers, with a specific focus on Claudin 18.2 (CLDN18.2) as an emerging and promising target. Recent phase III trials have unveiled the efficacy of Zolbetuximab, a CLDN18.2-targeting antibody, in combination with oxaliplatin-based chemotherapy for CLDN18.2-positive metastatic GC. As this novel therapeutic avenue unfolds, understanding the nuanced decision making regarding the selection of anti-CLDN18.2 therapies over other targeted agents in metastatic GC becomes crucial. This manuscript reviews the evolving role of CLDN18.2 as a biomarker in GC and explores the current status of CLDN18.2-targeting agents in clinical development. The aim is to provide concise insights into the potential of CLDN18.2 as a therapeutic target and guide future clinical decisions in the management of metastatic GC.

Zolbetuximab for Claudin18.2-positive gastric or gastroesophageal junction cancer

Claudins (CLDNs) are a family of major membrane proteins that form components of tight junctions. In normal tissues, CLDNs seal the intercellular space in the epithelial sheets to regulate tissue permeability, paracellular transport, and signal transduction. Claudin18.2 (CLDN18.2), a member of the CLDN family, is expressed specifically in gastric mucosal cells in normal tissue, and its expression is often retained in gastric cancer cells. CLDN18.2 is ectopically expressed in many cancers other than gastric cancer such as esophageal cancer, pancreatic cancer, biliary tract cancer, non-small-cell lung cancer, and ovarian cancer. Structurally, CLDN18.2 is localized on the apical side of the cell membrane and has extracellular loops capable of binding monoclonal antibodies. Upon malignant transformation, CLDN18.2 is exposed to the cell surface of the whole membrane, which enables the binding of monoclonal antibodies. Based on these characteristics, CLDN18.2 was considered to be optimal for target therapy, and zolbetuximab was developed which is a first-in-class chimeric immunoglobulin G1 monoclonal antibody highly specific for CLDN18.2. It binds to CLDN18.2 on the tumor cell surface and stimulates cellular and soluble immune effectors that activate antibody-dependent cytotoxicity and complement-dependent cytotoxicity. Recently, zolbetuximab combined with chemotherapy demonstrated a survival benefit in patients with CLDN18.2-positive and HER-2-negative gastric or gastroesophageal junction cancers in the global phase III SPOTLIGHT and GLOW trials. From these clinically meaningful results, CLDN18.2-targeting therapy including zolbetuximab has attracted a lot of attention. In this review, we summarize the clinical implications of CLDN18.2-positive gastric or GEJ cancer, and CLDN18.2-targeting therapy, mainly for zolbetuximab.

Emerging Targets for Systemic Treatment of Gastric Cancer: HER2 and Beyond

In recent years, remarkable progress has been made in the molecular profiling of gastric cancer. This progress has led to the development of various molecular classifications to uncover subtype-specific dependencies that can be targeted for therapeutic interventions. Human epidermal growth factor receptor 2 (HER2) is a crucial biomarker for advanced gastric cancer. The recent promising results of novel approaches, including combination therapies or newer potent agents such as antibody-drug conjugates, have once again brought attention to anti-HER2 targeted treatments. In HER2-negative diseases, the combination of cytotoxic chemotherapy and programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) inhibitors has become the established standard of care in first-line settings. In the context of gastric cancer, potential biomarkers such as PD-L1 expression, Epstein-Barr virus, microsatellite instability, and tumor mutational burden are being considered for immunotherapy. Recently, promising results have been reported in studies on anti-Claudin18.2 and fibroblast growth factor receptor 2 treatments. Currently, many ongoing trials are aimed at identifying potential targets using novel approaches. Further investigations will be conducted to enhance the progress of these therapies, addressing challenges such as primary and acquired resistance, tumor heterogeneity, and clonal evolution. We believe that these efforts will improve patient prognoses. Herein, we discuss the current evidence of potential targets for systemic treatment, clinical considerations, and future perspectives.

Claudin18.2 in Advanced Gastric Cancer

Globally, the fifth most common cancer and the fourth leading cause of cancer-related mortality is gastric cancer (GC). Recent clinical trials on solid tumors enrolled patients who possess druggable genetic alterations, protein expression, and immune characteristics. In gastric or gastroesophageal junction (GEJ) cancers, trastuzumab combined with first-line chemotherapy in human epidermal growth factor receptor 2 (HER2)-positive patients and ramucirumab combined with second-line paclitaxel remarkably prolonged overall survival (OS) compared with chemotherapy alone, according to phase 3 trial results. Recently, immune checkpoint inhibitor (ICI) monotherapy was approved as third- or later-line treatment. Chemotherapy plus ICIs as first-line treatment exhibited improved survival compared with chemotherapy alone in HER2-negative patients according to Checkmate 649 trial results. Conversely, systemic chemotherapy prognosis remains poor. although some patients may achieve durable response to treatment and prolonged survival in advanced GC. Recently, a first-in-class, chimeric immunoglobulin G1 monoclonal antibody (zolbetuximab) that targets and binds to claudin 18 isoform 2 (CLDN18.2) has emerged as a new target therapy in GC treatment. Global phase Ⅲ trials revealed that the addition of zolbetuximab to first-line chemotherapy prolonged OS in CLDN18.2-positive and HER2-negative GC patients. This review summarizes recent clinical trials of CLDN18.2-targeted therapy.

What Therapeutic Biomarkers in Gastro-Esophageal Junction and Gastric Cancer Should a Pathologist Know About?

Malignancies of upper gastrointestinal tract are aggressive, and most locally advanced unresectable and metastatic cancers are managed by a combination of surgery and neoadjuvant/adjuvant chemotherapy and radiotherapy. Current therapeutic recommendations include targeted therapies based on biomarker expression of an individual tumor. All G/gastro-esophageal junction (GEJ) cancers should be tested for HER2 status as a reflex test at the time of diagnosis. Currently, testing for PDL 1 and mismatch repair protein status is optional. HER2 testing is restricted to adenocarcinomas only and endoscopic biopsies, resections, or cellblocks. Facilities should be available for performing validated immunohistochemical stains and in-situ hybridization techniques, and importantly, pathologists should be experienced with preanalytical and analytical issues and scoring criteria. Genomic profiling via next-generation sequencing (NGS) is another strategy that assess numerous mutations and other molecular events simultaneously, including HER2 amplification, MSS status, tumor mutation burden, and neurotrophic tropomyosin-receptor kinases gene fusions.

Optimizing the Continuum of Care in Gastric Cancer

Gastric cancer (GC) still ranks as the fifth most common malignancy and the fourth leading cause of cancer-related death worldwide. Despite the recent progress in the therapeutic algorithm of the advanced disease with the advent of immune checkpoint inhibitors (ICIs) and next-generation HER2-directed therapies, survival rates remain poor, with a median survival hardly exceeding 12 months. Furthermore, only 40% of patients remain eligible for second- and later-line treatments due to the aggressiveness of the disease and the rapid deterioration of performance status (PS). Thus, current research is focusing either on the identification of novel treatment options or the development of personalized strategies to optimize the continuum of care and ultimately improve patients' outcome. In this article, we provide an overview of the current treatment landscape for advanced GC with a particular emphasis on later-line treatments and outline novel perspectives on the horizon.

Clinicopathologic features and prognostic value of claudin 18.2 overexpression in patients with resectable gastric cancer

Claudin 18.2 has emerged as a promising therapeutic target in gastric cancer based on phase 3 studies. However, clinicopathologic features associated with claudin 18.2 overexpression have not been comprehensively studied specifically for patients with resectable gastric cancer. This retrospective study included 299 patients with stage I-III resectable gastric cancer who underwent curative surgical resection. Possible associations between claudin 18.2 overexpression (moderate-to-strong expression in ≥ 75% by the 43-14A clone) and clinicopathologic features and survival outcomes were analyzed. There were 90 (30.1%), 96 (32.1%), and 113 (37.8%) patients with stage I, II, and III disease, respectively. Claudin 18.2 overexpression was noted in 139 out of 299 patients (46.5%). Claudin 18.2 overexpression was associated with a younger age, a lower invasion depth limited to the mucosa/submucosa, and less frequent lymphovascular invasion. Claudin 18.2 overexpression was also associated with Borrmann type 4 among patients with advanced gastric cancer and the diffuse histological type. Claudin 18.2 overexpression was not an independent factor for survival outcomes. In conclusion, claudin 18.2 was overexpressed in almost half of resectable gastric cancer patients. Claudin 18.2 overexpression was associated with some clinicopathological characteristics, but was not an independent prognostic factor in a localized setting.

Transcriptomic Profiling Reveals Claudin 18.2 as a Diagnostic Biomarker of Ménétrier's Disease and the Role of Hedgehog Signaling in Pathogenesis

Both Ménétrier's disease (MD) and juvenile polyposis syndrome (JPS) are rare premalignant conditions that can lead to gastric cancer development. MD is an acquired disease without known causative mutations. MD patients are characterized by an increased expression of EGF receptor (EGFR) ligand and transforming growth factor alpha (TGF-α) in the stomach. JPS is inherited in an autosomal dominant pattern and is caused by BMPR1A or SMAD4 mutations. It is characterized by multiple polyps throughout the gastrointestinal tract along with certain SMAD4 mutations that can result in gastric polyposis. Although there are many distinct clinico- endoscopic and histopathologic features that differ between the two diseases, they also share similar features that often lead to misdiagnosis. This study aimed to identify markers that can help distinguish MD from JPS and to better understand the pathogenesis of MD by comparing differential gene expression patterns. Upon examination of MD and JPS microscopically, we found almost all cases have patchy areas mimicking each other, making it difficult to make a correct diagnosis with histopathologic examination alone. Comparative analysis between MD and JPS using ingenuity pathway analysis (IPA) revealed both common and differential gene signatures. Common gene signatures included estrogen receptor signaling, integrin signaling, mTOR signaling, and others, which may be responsible for histopathologic similarities. Among differential gene signatures, we found that claudin 18 ( CLDN18 ) is upregulated in MD and confirmed that CLDN18.2 (isoform of CLDN18) protein expression is higher in MD than JPS by immunohistochemistry. Comparative analysis between MD and normal control revealed the hedgehog (Hh) signaling pathway is upregulated in MD. Treatment with a hedgehog pathway inhibitor partially rescued the histopathologic phenotypes in a MD mouse model. The current study provides valuable insight into the potential underlying mechanism of why MD and JPS show similar clinico-pathologic features. We also identified a diagnostic marker CLDN18.2 that can help distinguish MD from JPS, genetically. Furthermore, it also shows that Hh signaling plays an important role in the pathogenesis of MD and can function as a potential therapeutic target.

Current and Emerging Role of Monoclonal Antibody-Based First-Line Treatment in Advanced Gastro-Esophageal and Gastric Cancer

Gastric cancer is the fifth most common malignancy worldwide and one of the main causes of cancer-related death. While surgical treatment is the only curative option for early disease, many have inoperable or advanced disease at diagnosis. Treatment in this case would be a combination of chemotherapy and immunotherapy. Gastro-esophageal (GEJ) and gastric cancer (GC) genetic profiling with current molecular diagnostic techniques has significantly changed the therapeutic landscape in advanced cancers. The identification of key players in GEJ and GC survival and proliferation, such as human epidermal growth factor 2 (HER2), vascular endothelial growth factor (VEGF), and programmed cell death protein 1 (PD-1)/programmed cell death ligand-1 (PD-L1), has allowed for the individualization of advanced cancer treatment and significant improvement in overall survival and progression-free survival of patients. This review comprehensively examines the current and emerging role of monoclonal antibody-based first-line treatments in advanced GEJ and GC. We explore the impact of monoclonal antibodies targeting HER2, VEGF, PD-1/PD-L1, and Claudin 18.2 (CLDN18.2) on the first-line treatment landscape by talking about key clinical trials. This review emphasizes the importance of biomarker testing for optimal treatment selection and provides practical recommendations based on ASCO guidelines.

SPOTlight on GLOW

The GLOW randomized double-blind phase 3 trial1 shows that Claudin-18.2 targeting antibody zolbetuximab combined with capecitabine and oxaliplatin improves outcome compared to placebo and chemotherapy as first-line treatment in Claudin-18.2-positive, HER2-negative gastric or gastroesophageal junction adenocarcinomas.