Anetumab ravtansine versus vinorelbine in patients with relapsed, mesothelin-positive malignant pleural mesothelioma (ARCS-M): a randomised, open-label phase 2 trial

Evaluation of first-line and salvage therapies for unresectable malignant mesothelioma: A systematic review and network meta-analysis

BACKGROUND

Randomized controlled trials (RCTs) of systemic therapies for unresectable malignant mesothelioma have reported conflicting results. It is crucial and urgent to find optimal treatment options for this malignancy, which currently has a poor prognosis.

METHODS

Databases PubMed, EMBASE, Cochrane Library, ClinicalTrials.gov, and major international conferences were searched until February 29, 2024. The main outcomes of interest were overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and grade ≥3 treatment-related adverse events (TRAEs).

RESULTS

We analyzed 16 RCTs with a total of 5018 patients. Among first-line therapies, nivolumab and ipilimumab significantly increased OS and resulted in fewer grade ≥3 TRAEs. Bevacizumab plus chemotherapy significantly increased PFS. Among salvage therapies, ramucirumab and chemotherapy was associated with the best OS and PFS, but resulted in more grade ≥3 TRAEs. Subgroup analysis by histologic types suggested that in first-line settings, bevacizumab and chemotherapy increase OS the most for epithelioid type, while the nivolumab plus ipilimumab treatment increases OS the most for non-epithelioid type. In salvage therapies, ramucirumab and chemotherapy increase OS for both epithelioid and non-epithelioid types.

CONCLUSION

Nivolumab plus ipilimumab was associated with the best OS among first-line treatments. Ramucirumab and chemotherapy was associated with the best clinical outcomes in salvage settings. Treatment for malignant mesothelioma should be tailored based on different clinicopathological characteristics.

Emerging New Targets in Systemic Therapy for Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a heterogeneous cancer composed of distinct molecular and pathologic subtypes. Unfortunately, MPM is aggressive, and current therapies for advanced, unresectable disease remain limited to cytotoxic chemotherapy and immunotherapy. Our understanding of the genomic landscape of MPM is steadily growing, while the discovery of effective targeted therapies in MPM has advanced more slowly than in other solid tumors. Given the prevalence of alterations in tumor suppressor genes in MPM, it has been challenging to identify actionable targets. However, efforts to characterize the genetic signatures in MPM over the last decade have led to a range of novel targeted therapeutics entering early-phase clinical trials. In this review, we discuss the advancements made thus far in targeted systemic therapies in MPM and the future direction of targeted strategies in patients with advanced MPM.

Mesothelin expression in gynecologic carcinosarcoma: clinicopathological significance and correlation with HER2 expression

OBJECTIVE

This study aimed to evaluate mesothelin (MSLN) expression and determine its clinical significance and correlation with human epidermal growth factor receptor 2 (HER2) expression in gynecological carcinosarcoma.

METHODS

We retrospectively evaluated patients with uterine carcinosarcoma (UCS) and ovarian carcinosarcoma (OCS) who underwent surgery between 1997 and 2019. Immunohistochemical staining of formalin-fixed, paraffin-embedded specimens for MSLN (clone SP74) and HER2 (clone 4A5) was also performed. MSLN was scored using the H-score and 4-tired scoring system (0-3+). MSLN positivity was defined as any positive cell at any intensity, while high MSLN expression was defined as an intensity of ≥2+ in ≥30% of tumor cells. HER2 expression was scored according to modified 2018 American Society of Clinical Oncology/College of American Pathologists criteria.

RESULTS

A total of 128 patients were recruited, including 119 with UCS and 9 with OCS. All cases in UCS exhibited MSLN positivity, and 33.9% showed high-MSLN expression. Clinicopathological characteristics were not significantly associated with high or low-MSLN expression. However, the high-MSLN group showed more prolonged overall survival (OS) than the low-MSLN group (not assessed vs. 36.8 months; hazard ratio=0.48, 95% confidence interval=0.26-0.89, p=0.016). HER2-high patients had higher MSLN expression than HER2-negative patients. In high-MSLN and low-MSLN expression groups, HER2 status did not affect OS. OCS showed 100% MSLN positivity, with 66.6% high-MSLN.

CONCLUSION

MSLN expression is widely observed in gynecological carcinosarcomas. Moreover, high-MSLN expression is a favorable prognostic factor for UCS. MSLN could be a promising therapeutic target for UCS, even in the era of anti-HER2 therapy.

Diffuse Pleural Mesothelioma: Advances in Molecular Pathogenesis, Diagnosis, and Treatment

Diffuse pleural mesothelioma (DPM) is a highly aggressive malignant neoplasm arising from the mesothelial cells lining the pleural surfaces. While DPM is a well-recognized disease linked to asbestos exposure, recent advances have expanded our understanding of molecular pathogenesis and transformed our clinical practice. This comprehensive review explores the current concepts and emerging trends in DPM, including risk factors, pathobiology, histologic subtyping, and therapeutic management, with an emphasis on a multidisciplinary approach to this complex disease.

Preclinical assessment of a novel human antibody VH domain targeting mesothelin as an antibody-drug conjugate

Mesothelin (MSLN) has been a validated tumor-associated antigen target for several solid tumors for over a decade, making it an attractive option for therapeutic interventions. Novel antibodies with high affinity and better therapeutic properties are needed. In the current study, we have isolated and characterized a novel heavy chain variable (VH) domain 3C9 from a large-size human immunoglobulin VH domain library. 3C9 exhibited high affinity (KD [dissociation constant] <3 nM) and binding specificity in a membrane proteome array (MPA). In a mouse xenograft model, 3C9 fused to human IgG1 Fc was detected at tumor sites as early as 8 h post-infusion and remained at the site for over 10 days. Furthermore, 3C9 fused to a human Fc domain drug conjugate effectively inhibited MSLN-positive tumor growth in a mouse xenograft model. The X-ray crystal structure of full-length MSLN in complex with 3C9 reveals interaction of the 3C9 domains with two distinctive residue patches on the MSLN surface. This newly discovered VH antibody domain has a high potential as a therapeutic candidate for MSLN-expressing cancers.

Current State-of-the-Art Therapy for Malignant Pleural Mesothelioma and Future Options Centered on Immunotherapy

Malignant pleural mesothelioma (MPM) is a locally aggressive disease related to asbestos exposure with a median survival for untreated patients of 4-8 months. The combination of chemotherapy based on platinum and antifolate is the standard treatment, and the addition of bevacizumab adds two months to median survival. Recently, in first-line treatment, immunotherapy combining nivolumab with ipilimumab has been shown to be superior to chemotherapy in the CheckMate-743 study in terms of overall survival (18.1 months), leading to its approval by the FDA and EMA. The positive results of this study represent a new standard of treatment for patients with MPM; however, not all patients will benefit from immunotherapy treatment. In an effort to improve the selection of patient candidates for immunotherapy for different tumors, biomarkers that have been associated with a greater possibility of response to treatment have been described. MPM is a type of tumor with low mutational load and neo-antigens, making it a relatively non-immunogenic tumor for T cells and possibly less susceptible to responding to immunotherapy. Different retrospective studies have shown that PD-L1 expression occurs in 20-40% of patients and is associated with a poor prognosis; however, the predictive value of PD-L1 in response to immunotherapy has not been confirmed. The purpose of this work is to review the state of the art of MPM treatment in the year 2023, focusing on the efficacy results of first-line or subsequent immunotherapy studies on patients with MPM and possible chemo-immunotherapy combination strategies. Additionally, potential biomarkers of response to immunotherapy will be reviewed, such as histology, PD-L1, lymphocyte populations, and TMB.

The ever-expanding landscape of antibody-drug conjugates (ADCs) in solid tumors: A systematic review

BACKGROUND

The advent of targeted therapies signaled novel avenues for more optimal oncological outcomes. Antibody-drug conjugates (ADCs) have risen as a cornerstone of the ever-expanding targeted therapy era. The purpose of this systematic review is to delineate the rapidly evolving clinical landscape of ADCs for solid tumors.

METHODS

A literature search was performed in Medline, Embase and Cochrane databases for phase II and III clinical trials. Outcomes of interest were the objective response rate, overall survival, progression-free survival and adverse events.

RESULTS

A total of 92 clinical trials (76 phase II and 16 phase III) evaluated the efficacy and safety of ADCs for a plethora of solid tumors. Out of the 30 investigated ADCs, 8 have received approval by regulatory organizations for solid tumors. Currently, 52 phase III clinical trials for ADCs are ongoing.

CONCLUSION

ADCs have shown promising results for several solid tumors and various cancer settings.

New Immunohistochemical Markers for Pleural Mesothelioma Subtyping

Pleural mesothelioma (PM) comprises three main subtypes: epithelioid, biphasic and sarcomatoid, which have different impacts on prognosis and treatment definition. However, PM subtyping can be complex given the inter- and intra-tumour morphological heterogeneity. We aim to use immunohistochemistry (IHC) to evaluate five markers (Mesothelin, Claudin-15, Complement Factor B, Plasminogen Activator Inhibitor 1 and p21-activated Kinase 4), whose encoding genes have been previously reported as deregulated among PM subtypes. Immunohistochemical expressions were determined in a case series of 73 PMs, and cut-offs for the epithelioid and non-epithelioid subtypes were selected. Further validation was performed on an independent cohort (30 PMs). For biphasic PM, the percentage of the epithelioid component was assessed, and IHC evaluation was also performed on the individual components separately. Mesothelin and Claudin-15 showed good sensitivity (79% and 84%) and specificity (84% and 73%) for the epithelioid subtype. CFB and PAK4 had inferior performance, with higher sensitivity (89% and 84%) but lower specificity (64% and 36%). In the biphasic group, all markers showed different expression when comparing epithelioid with sarcomatoid areas. Mesothelin, Claudin-15 and CFB can be useful in subtype discrimination. PAI1 and PAK4 can improve component distinction in biphasic PM.

Chinese expert consensus on the diagnosis and treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a malignant tumor originating from the pleura, and its incidence has been increasing in recent years. Due to the insidious onset and strong local invasiveness of MPM, most patients are diagnosed in the late stage and early screening and treatment for high-risk populations are crucial. The treatment of MPM mainly includes surgery, chemotherapy, and radiotherapy. Immunotherapy and electric field therapy have also been applied, leading to further improvements in patient survival. The Mesothelioma Group of the Yangtze River Delta Lung Cancer Cooperation Group (East China LUng caNcer Group, ECLUNG; Youth Committee) developed a national consensus on the clinical diagnosis and treatment of MPM based on existing clinical research evidence and the opinions of national experts. This consensus aims to promote the homogenization and standardization of MPM diagnosis and treatment in China, covering epidemiology, diagnosis, treatment, and follow-up.

Targeted Approaches to Treatment of Pleural Mesothelioma: A Review

Pleural mesothelioma is an aggressive disease that is enriched for inactivating alterations in tumor suppressor genes. Systemic therapeutic strategies for pleural mesothelioma generally involve chemotherapies and immunotherapies that are chosen without consideration of the tumor's molecular profile. As this generalized approach to treatment rarely yields durable responses, alternative therapeutic regimens are urgently indicated. Preclinical studies have identified synthetic lethal protein and metabolic interactions, recurrently overexpressed proteins, and frequent pathway perturbations that may be therapeutically exploited in mesothelioma. This review discusses the mechanism of action of emerging investigational therapies and summarizes findings from phase I-II clinical trials exploring selective, biomarker-driven therapeutic strategies for mesothelioma, with a focus on five common targets. Finally, using lessons learned from these clinical trials, imperatives for successful implementation of targeted therapy in mesothelioma are discussed.

Toxicity profiles of antibody-drug conjugates for anticancer treatment: a systematic review and meta-analysis

BACKGROUND

Antibody-drug conjugates are attractive targeted agents in anticancer treatment because of their unique mechanism of action and reduced toxicity. Little is known about the spectrum of adverse events associated with antibody-drug conjugates, despite tens of clinical trials.

METHODS

A systematic review of randomized controlled trials evaluating antibody-drug conjugate efficacy in anticancer treatment was conducted. PubMed, EMBASE, and ClinicalTrial.gov were searched for relevant studies. Meta-analyses assessed the odds ratios (ORs) of 12 treatment-related symptoms and toxicities in patients treated with antibody-drug conjugates compared with those receiving other anticancer agents without antibody-drug conjugates. All-grade and high-grade (grade ≥3) toxicities were examined.

RESULTS

Twenty studies involving 10 075 patients were included. Compared with control groups, antibody-drug conjugates were associated with a higher risk of all-grade fatigue (OR = 1.25, 95% confidence interval [CI] = 1.08 to 1.45), anorexia (OR = 1.36, 95% CI = 1.09 to 1.69), nausea (OR = 1.46, 95% CI = 1.09 to 1.97), and sensory neuropathy (OR = 2.18, 95% CI = 1.27 to 3.76) as treatment-related symptoms. Patients treated with antibody-drug conjugates had a statistically significantly lower risk of all-grade febrile neutropenia (OR = 0.46, 95% CI = 0.22 to 0.96). Conversely, they had a higher risk of thrombocytopenia (OR = 2.07, 95% CI = 1.00 to 4.31), increased alanine aminotransferase (OR = 2.51, 95% CI = 1.84 to 3.40), and increased aspartate aminotransferase (OR = 2.83, 95% CI = 2.04 to 3.93). Subgroup analysis showed a similar toxicity profile when comparing the solid tumors with hematologic malignancy groups and the antibody-drug conjugate vs antibody-drug conjugate plus chemotherapy groups, except for some neurologic and hematologic adverse events.

CONCLUSIONS

This comprehensive profile of adverse events associated with antibody-drug conjugate-based treatment shows an increase in various types of all-grade treatment-related symptoms and adverse events, although no increase in high-grade adverse events was seen.

High mesothelin expression by immunohistochemistry predicts improved survival in pleural mesothelioma

AIMS

Mesothelin (MSLN) is a cancer-associated antigen that is overexpressed in malignancies such as mesothelioma, pancreatic and ovarian cancer. It is also a target for novel personalised therapies, including antibodies, antibody-drug conjugates and chimeric antigen receptor T cells. Immunohistochemistry may predict those who would best respond to anti-mesothelin therapies and guide decisions in therapeutic strategy. This study aimed to assess the intensity and distribution of MSLN immunostaining in mesothelioma, and to determine the prognostic value of MSLN expression by histochemical-score (H-score).

METHODS AND RESULTS

The MN1 anti-MSLN antibody was used to stain a formalin-fixed paraffin-embedded tissue microarray of histologically confirmed mesothelioma from 75 consecutive patients who had undergone pleurectomy with or without decortication. MSLN positivity, the staining intensity, distribution of staining and H-score were evaluated. The correlation of H-score with prognosis was investigated. Sixty-six per cent of epithelioid tumours were MSLN-positive (with expression in > 5% tumour cells). Of MSLN-expressing epithelioid tumours, 70.4% had moderate (2+) or strong (3+) intensity MSLN immunostaining, although only 37% of samples had staining in ≥ 50% of tumour cells. In multivariate analysis, MSLN H-score as a continuous variable and an H-score ≥ 33 were independent predictors of improved survival (P = 0.04 and P < 0.001, respectively).

CONCLUSIONS

MSLN expression was more heterogenous in epithelioid mesothelioma than reported previously. Therefore, it would be appropriate to perform an immunohistochemical assessment of MSLN expression to stratify and assess patient suitability for mesothelin-targeted personalised therapies, such as chimeric antigen receptor T cells.

Pleural mesothelioma: a snapshot of emerging drug targets and opportunities for non-surgical therapeutic advancement

INTRODUCTION

Pleural mesothelioma is a rare and aggressive cancer originating in the pleura, with a devastating prognosis and limited treatment options. There have been significant advancements in the management of this disease in recent years. Since 2021, nivolumab and ipilimumab immune checkpoint inhibitors have become the new standard of care for first-line treatment of pleural mesothelioma.

AREAS COVERED

While a combination of chemotherapy and immune checkpoint inhibitors appears to be the next step, targeted therapies are emerging thanks to our understanding of the oncogenesis of pleural mesothelioma. Moreover, several new strategies are currently being investigated, including viral therapy, antibody-drug conjugates, and even cell therapies with CAR-T cells or dendritic cells. In this review, we will explore the various future opportunities that could potentially transform patients' lives in light of the clinical trials that have been conducted.

EXPERT OPINION

Future clinical studies aim to rebiopsy patients after disease progression to identify new molecular alterations and to be associated with ancillary studies, guiding subsequent therapy decisions. Predicting and investigating treatment resistance mechanisms will lead to innovative approaches and improved treatment outcomes.

Important functional role of the protein osteopontin in the progression of malignant pleural mesothelioma

Background

Malignant Pleural Mesothelioma (MPM) is an aggressive cancer of the mesothelial lining associated with exposure to airborne non-degradable asbestos fibers. Its poor response to currently available treatments prompted us to explore the biological mechanisms involved in its progression. MPM is characterized by chronic non-resolving inflammation; in this study we investigated which inflammatory mediators are mostly expressed in biological tumor samples from MPM patients, with a focus on inflammatory cytokines, chemokines and matrix components.

Methods

Expression and quantification of Osteopontin (OPN) was detected in tumor and plasma samples of MPM patients by mRNA, immunohistochemistry and ELISA. The functional role of OPN was investigated in mouse MPM cell lines in vivo using an orthotopic syngeneic mouse model.

Results

In patients with MPM, the protein OPN was significantly more expressed in tumors than in normal pleural tissues and predominantly produced by mesothelioma cells; plasma levels were elevated in patients and associated with poor prognosis. However, modulation of OPN levels was not significantly different in a series of 18 MPM patients receiving immunotherapy with durvalumab alone or with pembrolizumab in combination with chemotherapy, some of whom achieved a partial clinical response. Two established murine mesothelioma cell lines: AB1 and AB22 of sarcomatoid and epithelioid histology, respectively, spontaneously produced high levels of OPN. Silencing of the OPN gene (Spp1) dramatically inhibited tumor growth in vivo in an orthotopic model, indicating that OPN has an important promoting role in the proliferation of MPM cells. Treatment of mice with anti-CD44 mAb, blocking a major OPN receptor, significantly reduced tumor growth in vivo.

Conclusion

These results demonstrate that OPN is an endogenous growth factor for mesothelial cells and inhibition of its signaling may be helpful to restrain tumor progression in vivo. These findings have translational potential to improve the therapeutic response of human MPM.

Antibody-Drug Conjugates in Lung Cancer: Recent Advances and Implementing Strategies

Antibody-drug conjugates (ADCs) are one of the fastest-growing oncology therapeutics, merging the cytotoxic effect of conjugated payload with the high specific ability and selectivity of monoclonal antibody targeted on a specific cancer cell membrane antigen. The main targets for ADC development are antigens commonly expressed by lung cancer cells, but not in normal tissues. They include human epidermal growth factor receptor 2, human epidermal growth factor receptor 3, trophoblast cell surface antigen 2, c-MET, carcinoembryonic antigen-related cell adhesion molecule 5, and B7-H3, each with one or more specific ADCs that showed encouraging results in the lung cancer field, more in non-small-cell lung cancer than in small-cell lung cancer histology. To date, multiple ADCs are under evaluation, alone or in combination with different molecules (eg, chemotherapy agents or immune checkpoint inhibitors), and the optimal strategy for selecting patients who may benefit from the treatment is evolving, including an improvement of biomarker understanding, involving markers of resistance or response to the payload, besides the antibody target. In this review, we discuss the available evidence and future perspectives on ADCs for lung cancer treatment, including a comprehensive discussion on structure-based drug design, mechanism of action, and resistance concepts. Data were summarized by specific target antigen, biology, efficacy, and safety, differing among ADCs according to the ADC payload and their pharmacokinetics and pharmacodynamics properties.

Target Therapy in Malignant Pleural Mesothelioma: Hope or Mirage?

Malignant Pleural Mesothelioma (MPM) is a rare neoplasm that is typically diagnosed in a locally advanced stage, making it not eligible for radical surgery and requiring systemic treatment. Chemotherapy with platinum compounds and pemetrexed has been the only approved standard of care for approximately 20 years, without any relevant therapeutic advance until the introduction of immune checkpoint inhibitors. Nevertheless, the prognosis remains poor, with an average survival of only 18 months. Thanks to a better understanding of the molecular mechanisms underlying tumor biology, targeted therapy has become an essential therapeutic option in several solid malignancies. Unfortunately, most of the clinical trials evaluating potentially targeted drugs for MPM have failed. This review aims to present the main findings of the most promising targeted therapies in MPM, and to explore possible reasons leading to treatments failures. The ultimate goal is to determine whether there is still a place for continued preclinical/clinical research in this area.

Safety and activity of anti-mesothelin antibody-drug conjugate anetumab ravtansine in combination with pegylated-liposomal doxorubicin in platinum-resistant ovarian cancer: multicenter, phase Ib dose escalation and expansion study

OBJECTIVES

Anetumab ravtansine is an antibody-drug conjugate consisting of a fully human anti-mesothelin monoclonal antibody conjugated to cytotoxic maytansinoid tubulin inhibitor DM4. Mesothelin is highly expressed in ovarian cancer. This phase Ib study determines the safety, pharmacokinetics, and anti-tumor activity of anetumab ravtansine and pegylated liposomal doxorubicin in mesothelin-expressing platinum-resistant ovarian cancer.

METHODS

Anetumab ravtansine (5.5 or 6.5 mg/kg) and pegylated liposomal doxorubicin (30 mg/m2) were administered intravenously every 3 weeks to 65 patients with platinum-resistant epithelial ovarian cancer. Mesothelin expression was assessed by central immunohistochemistry. Adverse events, tumor response (RECIST 1.1), and progression-free survival were determined. Biomarker samples were assessed by ELISA and next-generation sequencing.

RESULTS

In dose escalation, nine patients received anetumab ravtansine across two doses (5.5 or 6.5 mg/kg). The maximum tolerated dose of anetumab ravtansine was 6.5 mg/kg every 3 weeks and no dose-limiting toxicities were observed. In dose expansion, 56 patients were treated at the maximum tolerated dose. The most common treatment-emergent adverse events of any grade were nausea (47.7%), decreased appetite (43.1%), fatigue (38.5%), diarrhea (32.3%), and corneal disorder (29.2%). In all treated patients the objective response rate was 27.7% (95% CI 17.3% to 40.2%), including one complete (1.5%) and 17 partial responses (26.2%), with median duration of response of 7.6 (95% CI 3.3 to 10.2) months and median progression-free survival of 5.0 (95% CI 3.2 to 6.0) months. In an exploratory analysis of a sub-set of patients (n=19) with high mesothelin expression who received ≤3 prior lines of systemic therapy, the objective response rate was 42.1% (95% CI 20.3% to 66.5%) with a median duration of response of 8.3 (95% CI 4.1 to 12.0) months and median progression-free survival of 8.5 (95% CI 4.0 to 11.4) months.

CONCLUSIONS

Anetumab ravtansine and pegylated liposomal doxorubicin showed tolerability and promising clinical activity. These results established the dose schedule and the mesothelin-positive target population of this combination for a phase III study in platinum-resistant ovarian cancer.

TRIAL REGISTRATION NUMBER

NCT02751918.

Future potential targets of antibody-drug conjugates in breast cancer

Metastatic breast cancer (BC) remains an incurable disease. Besides endocrine and targeted agents, chemotherapy is still a relevant therapeutic option for this disease. Recently, antibody-drug conjugates (ADCs) have shown to overcome the lack of tumor specificity and systemic toxicity typically associated with traditional chemotherapies, thus improving the therapeutic index. To effectively exploit this technological breakthrough, identification of optimal target antigens (Ags) is of utmost importance. To make the ideal target, differential expression of target Ags between healthy and cancer tissues, as well as specific mechanisms of ADC internalization after Ag-antibody interaction are required. Therefore, several in silico strategies to identify and characterize new promising candidate Ags have been developed. If initial in vitro and in vivo positive data are documented, thus providing a biological rationale for further Ag investigation, early phase clinical trials are designed. In BC, these strategies have already led to the development of effective ADCs, namely trastuzumab emtansine (T-DM1), trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG), primarily targeting HER2 and TROP-2. However, promising new Ags are currently under investigation, with encouraging results especially coming from targeting HER3, FRα, Tissue Factor, LIV-1, ROR1-2, and B7-H4. In this review, we describe the landscape of emergent and future potential targets (i.e., other than HER2 and TROP-2) investigated in BC for ADC development. Predominant target expression, function, preclinical rationale, potential clinical implication, as well as preliminary clinical trial results are provided.

Targeting Mesothelin in Solid Tumours: Anti-mesothelin Antibody and Drug Conjugates

PURPOSE OF REVIEW

This review aims to summarise the pathobiological role of mesothelin and the current data on therapeutic antibodies targeting mesothelin in solid tumours.

RECENT FINDINGS

High mesothelin expression is restricted to the pericardium, pleura, peritoneum and tunica vaginalis. Mesothelin does not seem to have any normal biological function in adult normal tissues. Mesothelin is highly expressed in mesothelioma, serous ovarian cancer, pancreatic cancer and some gastric cancer and adenocarcinoma of the lung and is responsible for tumour proliferation, metastasis, resistance to chemotherapy or radiation and evasion of immune system. To date, antibody, antibody drug conjugates and bispecific antibodies with immune checkpoints have been investigated in mesothelin expressing malignancies. After a couple of decades of clinical investigation in antibody targeting mesothelin, the therapeutic benefit is relatively modest. Novel delivery of mesothelin targeting agents, more potent payload in antibody drug conjugates and immune checkpoint inhibitor, may improve therapeutic benefit.

Immunotherapy targeting mesothelin in acute myeloid leukemia

Mesothelin (MSLN) is an emerging target that exists in soluble and membrane-associated forms. It is usually used for the diagnosis and treatment of MSLN-positive solid tumors. Interestingly, recent studies have shown that MSLN is highly expressed in 36% of acute myeloid leukemia (AML) patients and barely expressed in normal hematopoietic cells, which makes MSLN a promising target for the treatment of AML. It has been shown that MSLN is detectable as a diagnostic marker in its soluble form. Although the mechanism of action is unclear, MSLN remains a promising target for immunotherapy. Most MSLN research has been conducted in solid tumors, and less research has been conducted in hematopoietic tumors. Increasing research on MSLN is underway in AML, a hematopoietic neoplasm. For example, MSLN is related to extramedullary disease, minimal residual disease, and relapse in AML patients. Decreasing the expression of MSLN reduces the severity of the disease course. This information suggests that MSLN may be an ideal target for the treatment of many AML-related diseases to improve the prognosis and survival rate. At present, there are a few immunotherapies targeting MSLN in AML in preclinical and clinical trials, such as antibody-drug conjugates, bispecific T-cell engagers, and chimeric antigen receptor-T cells, which opens new room for the treatment of MSLN-related AML.

The application of cancer stem cell model in malignant mesothelioma

The high mortality rate of malignant pleural mesothelioma led to study the mechanisms for chemoresistance. The cancer stem cell (CSC) model has been proposed to explain chemoresistance. CSCs are characterized by self-renewal capacity, that is detected through tumor-initiating cell assays. As in other malignancies, many studies sought to identify surface markers to isolate CSCs from malignant mesothelioma. Other studies characterized malignant mesothelioma CSCs for the expression of specific genes involved in stemness and the expression of proteins involved in chemoresistance. However, the main methods to characterize isolated CSCs include sphere formation, invasiveness, tumor-initiating capacity and expression of specific surface markers. The better knowledge of malignant mesothelioma CSCs allowed exploring new potential targets to develop specific treatments.