Vatalanib in malignant mesothelioma: a phase II trial by the Cancer and Leukemia Group B (CALGB 30107)

Unleashing precision: A review of targeted approaches in pleural mesothelioma

This review delves into the intricate landscape of pleural mesothelioma (PM), emphasizing the need for nuanced therapeutic strategies. While platinum-based chemotherapy remains a cornerstone, the advent of immune checkpoint inhibitors (ICIs), notably through the Checkmate 743 trial, has reshaped treatment paradigms. Challenges persist due to patient heterogeneity and a lack of specific biomarkers. Targeting genotypic and phenotypic alterations emerges as a promising avenue, demanding precision oncology in this rare disease. CDKN2A loss, prevalent in PM, may respond to CDK4/6 inhibitors. Defects in MMR and HR suggest tailored approaches with ICI or PARP inhibitors, respectively. Ongoing trials explore novel inhibitors and promising targets like mesothelin. Implementing these strategies requires overcoming challenges in patient selection, combination therapies, biomarker identification, and cost considerations. Collaboration is crucial for transforming these insights into impactful clinical interventions, heralding the era of personalized and precision medicine for PM.

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.

Malignant pleural mesothelioma nodules remodel their surroundings to vascularize and grow

Background

The microanatomical steps of malignant pleural mesothelioma (MPM) vascularization and the resistance mechanisms to anti-angiogenic drugs in MPM are unclear.

Methods

We investigated the vascularization of intrapleurally implanted human P31 and SPC111 MPM cells. We also assessed MPM cell's motility, invasion and interaction with endothelial cells in vitro.

Results

P31 cells exhibited significantly higher two-dimensional (2D) motility and three-dimensional (3D) invasion than SPC111 cells in vitro. In co-cultures of MPM and endothelial cells, P31 spheroids permitted endothelial sprouting (ES) with minimal spatial distortion, whereas SPC111 spheroids repealed endothelial sprouts. Both MPM lines induced the early onset of submesothelial microvascular plexuses covering large pleural areas including regions distant from tumor colonies. The development of these microvascular networks occurred due to both intussusceptive angiogenesis (IA) and ES and was accelerated by vascular endothelial growth factor A (VEGF-A)-overexpression. Notably, SPC111 colonies showed different behavior to P31 cells. P31 nodules incorporated tumor-induced capillary plexuses from the earliest stages of tumor formation. P31 cells deposited a collagenous matrix of human origin which provided "space" for further intratumoral angiogenesis. In contrast, SPC111 colonies pushed the capillary plexuses away and thus remained avascular for weeks. The key event in SPC111 vascularization was the development of a desmoplastic matrix of mouse origin. Continuously invaded by SPC111 cells, this matrix transformed into intratumoral connective tissue trunks, providing a route for ES from the diaphragm.

Conclusions

Here, we report two distinct growth patterns of orthotopically implanted human MPM xenografts. In the invasive pattern, MPM cells invade and thus co-opt peritumoral capillary plexuses. In the pushing/desmoplastic pattern, MPM cells induce a desmoplastic response within the underlying tissue which allows the ingrowth of a nutritive vasculature from the pleura.

Pleural mesothelioma (PM) - The status of systemic therapy

Pleural mesothelioma (PM) remains a malignancy with poor prognosis. Despite initial disappointing response rates to single-agent chemotherapy, upfront platinum and anti-folate-based combination chemotherapy has remained the backbone of treatment for PM for the last three decades. The role of maintenance chemotherapy remains unclear; switch-maintenance gemcitabine has shown improvements in progression-free but not overall survival. The addition of antiangiogenic agents to chemotherapy yielded modest improvements in survival, both upfront in combination with platinum-pemetrexed, and in the relapsed setting. Immunotherapy, particularly PD-(L)1 inhibitors, has shown important but variable effectiveness in relapsed PM when used as monotherapy, and is an important salvage treatment after first-line chemotherapy. Furthermore, the randomized phase 3 trial of ipilimumab-nivolumab versus platinum-pemetrexed chemotherapy demonstrated improved overall survival favouring ipilimumab-nivolumab (HR 0.74, 96.6% CI 0.60-0.91; p = 0.0020), establishing this regimen as the new standard first-line treatment for PM, particularly in those with non-epithelioid histology. Increased interest in PM genomics has led to development of novel personalized therapeutics, such as those targeting DNA repair and EZH2 pathways, however with variable outcomes in trials. Targeting the membrane glycoprotein mesothelin and arginine deprivation are other important strategies under ongoing investigation. The field of PM is changing and new treatments bring hope to a largely lethal and poor prognostic malignancy. Despite these developments, current challenges include understanding the role of combination and multimodality treatments, drivers of resistance to treatment, and establishing predictive biomarkers to improve patient selection and treatment sequencing.

ERS/ESTS/EACTS/ESTRO guidelines for the management of malignant pleural mesothelioma

The European Respiratory Society (ERS)/European Society of Thoracic Surgeons (ESTS)/European Association for Cardio-Thoracic Surgery (EACTS)/European Society for Radiotherapy and Oncology (ESTRO) task force brought together experts to update previous 2009 ERS/ESTS guidelines on management of malignant pleural mesothelioma (MPM), a rare cancer with globally poor outcome, after a systematic review of the 2009-2018 literature. The evidence was appraised using the Grading of Recommendations, Assessment, Development and Evaluation approach. The evidence syntheses were discussed and recommendations formulated by this multidisciplinary group of experts. Diagnosis: pleural biopsies remain the gold standard to confirm the diagnosis, usually obtained by thoracoscopy but occasionally via image-guided percutaneous needle biopsy in cases of pleural symphysis or poor performance status. Pathology: standard staining procedures are insufficient in ∼10% of cases, justifying the use of specific markers, including BAP-1 and CDKN2A (p16) for the separation of atypical mesothelial proliferation from MPM. Staging: in the absence of a uniform, robust and validated staging system, we advise using the most recent 2016 8th TNM (tumour, node, metastasis) classification, with an algorithm for pretherapeutic assessment. Monitoring: patient's performance status, histological subtype and tumour volume are the main prognostic factors of clinical importance in routine MPM management. Other potential parameters should be recorded at baseline and reported in clinical trials. Treatment: (chemo)therapy has limited efficacy in MPM patients and only selected patients are candidates for radical surgery. New promising targeted therapies, immunotherapies and strategies have been reviewed. Because of limited data on the best combination treatment, we emphasize that patients who are considered candidates for a multimodal approach, including radical surgery, should be treated as part of clinical trials in MPM-dedicated centres.

Analysis of angiogenic and stromal biomarkers in a large malignant mesothelioma cohort

BACKGROUND

Malignant mesothelioma (MM) is an aggressive malignancy of the pleura and other mesothelial membranes. Agents targeting vascular endothelial growth factor (VEGF) such as bevacizumab; and multi-kinase inhibitors such as nintedanib [angiokinase inhibitor of VEGF, platelet-derived growth factor (PDGF) receptor and fibroblast growth factor receptor (FGFR)] have recently demonstrated efficacy in MM.

METHODS

Tissue microarrays (TMAs) were created from formalin-fixed, paraffin-embedded tissue samples obtained from 326 patients with MM who were treated surgically. PDGF-CC, FGFR-1, VEGF and CD31 expression were analysed by immunohistochemical (IHC) staining. The H-score method assigned a score of 0-300 to each sample, based on the percentage of cells stained at different intensities. CD31 was evaluated via Chalkley's method to evaluate microvessel density. We evaluated the association between expression of the biomarkers, clinicopathological factors and outcomes, in patients with MM.

RESULTS

CD31 high (≥5) was seen in only 31/302 (10.3%) irrespective of histology. PDGF-CC high (≥150) was seen in 203 /310 (65%) of all samples. VEGF high (≥80) was seen in 219/322 (68%) of all MM with 143/209 (68%) of epithelioid histology. FGFR-1 high (≥40) was seen in 127/310 (41%) of all MM. There was no association of VEGF and FGFR-1 IHC with survival nor differences between histological subtypes. There was a non-significant trend towards poorer survival in epithelioid tumours with increased PDGF-CC expression (OS 18.5 vs 13.2 months; HR 0.7928; 95% CI 0.5958 to 1.055, P = 0.1110). High CD31 score was associated with significantly poorer survival (OS 12 vs 8.6 months; HR 0.48; 95% CI 0.2873 to 0.7941, P = 0.0044). Of the 31 patients with high CD31 scores; 23/31 (74%) were also high for PDGF-CC and 20/31 (64%) with high VEGF scores. CD31 was found to be an independent prognostic factor in multivariate analysis (HR 1.540; 95% CI 1.018 to 2.330; p = 0.041).

CONCLUSIONS

High CD31 was an independent poor prognostic factor and high PDGF-CC expression was associated with poor survival in MM. Abrogating these pathways may have prognostic implications.

Anticancer potential of new 3-nitroaryl-6-(N-methyl)piperazin-1,2,4-triazolo[3,4-a]phthalazines targeting voltage-gated K+ channel: Copper-catalyzed one-pot synthesis from 4-chloro-1-phthalazinyl-arylhydrazones

A series of six 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines were prepared through a facile and efficient one-pot copper-catalyzed procedure from 4-chloro-1-phthalazinyl-arylhydrazones with relatively good yields (62-83%). The one-pot copper-catalytic procedure consists of two simultaneous reactions: (i) a direct intramolecular dehydrogentaive cyclization between ylidenic carbon and adjacent pyrazine nitrogen to form 1,2,4-triazolo ring and, (ii) a direct N-amination on carbon-chlorine bond. Then, an in vitro anticancer evaluation was performed for the synthesized compounds against five selected human cancer cells (A549, MCF-7, SKBr3, PC-3 and HeLa). The nitro-derivatives were significantly more active against cancer strains than against the rest of tested compounds. Specifically, compound 8d was identified as the most promising anticancer agent with significant biological responses and low relative toxicities on human dermis fibroblast. The cytotoxic effect of compound 8d was more significant on PC3, MCF-7 and SKBr3 cancer cells with low-micromolar IC₅₀ value ranging from 0.11 to 0.59 μM, superior to Adriamycin drug. Mechanistic experimental and theoretical studies demonstrated that compounds 8d act as a K⁺ channel inhibitor in cancer models. Further molecular docking studies suggest that the EGFR Tyrosine Kinase enzyme may be a potential target for the most active 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines.

ERS/ESTS/EACTS/ESTRO guidelines for the management of malignant pleural mesothelioma

The European Respiratory Society (ERS)/European Society of Thoracic Surgeons (ESTS)/European Association for Cardio-Thoracic Surgery (EACTS)/European Society for Radiotherapy and Oncology (ESTRO) task force brought together experts to update previous 2009 ERS/ESTS guidelines on management of malignant pleural mesothelioma (MPM), a rare cancer with globally poor outcome, after a systematic review of the 2009-2018 literature. The evidence was appraised using the Grading of Recommendations, Assessment, Development and Evaluation approach. The evidence syntheses were discussed and recommendations formulated by this multidisciplinary group of experts. Diagnosis: pleural biopsies remain the gold standard to confirm the diagnosis, usually obtained by thoracoscopy but occasionally via image-guided percutaneous needle biopsy in cases of pleural symphysis or poor performance status. Pathology: standard staining procedures are insufficient in ∼10% of cases, justifying the use of specific markers, including BAP-1 and CDKN2A (p16) for the separation of atypical mesothelial proliferation from MPM. Staging: in the absence of a uniform, robust and validated staging system, we advise using the most recent 2016 8th TNM (tumour, node, metastasis) classification, with an algorithm for pre-therapeutic assessment. Monitoring: patient's performance status, histological subtype and tumour volume are the main prognostic factors of clinical importance in routine MPM management. Other potential parameters should be recorded at baseline and reported in clinical trials. Treatment: (chemo)therapy has limited efficacy in MPM patients and only selected patients are candidates for radical surgery. New promising targeted therapies, immunotherapies and strategies have been reviewed. Because of limited data on the best combination treatment, we emphasise that patients who are considered candidates for a multimodal approach, including radical surgery, should be treated as part of clinical trials in MPM-dedicated centres.

Antiangiogeneic Strategies in Mesothelioma

There is a strong rationale for inhibiting angiogenesis in mesothelioma. Vascular endothelial growth factor (VEGF) is an autocrine growth factor in mesothelioma and a potent mitogen for mesothelial cells. Further, the abnormal tumor vasculature promotes raised interstitial pressure and hypoxia, which may be detrimental to both penetration and efficacy of anticancer agents. Antiangiogenic agents have been trialed in mesothelioma for close to two decades, with early phase clinical trials testing vascular targeting agents, the VEGF-A targeting monoclonal antibody bevacizumab, and numerous tyrosine kinase inhibitors, many with multiple targets. None of these have shown efficacy which has warranted further development as single agents in any line of therapy. Whilst a randomized phase II trial combining the multitargeted tyrosine kinase inhibitor nintedanib with platinum/pemetrexed chemotherapy was positive, these results were not confirmed in a subsequent phase III study. The combination of cisplatin and pemetrexed with bevacizumab, in appropriately selected patients, remains the only anti-angiogenic combination showing efficacy in mesothelioma. Extensive efforts to identify biomarkers of response have not yet been successful.

Chemotherapy options versus "novel" therapies: how should we treat patients with malignant pleural mesothelioma

Today there are several options for the treatment of patients with malignant pleural mesothelioma (MPM). The therapeutic arsenal has expanded from only chemotherapy with or without surgery in selected cases to a variety of new compounds that target the malignant cell or its micro-environment. Immunotherapy has been the latest achievement and now single arm and randomized studies are being presented. A renewed interest has occurred in the combination of surgery, chemotherapy and radiation therapy. In this review we present the available data on previous and running studies and try to give a recommendation how to select the best patient for the most optimal therapy.

Malignant Pleural Mesothelioma: State-of-the-Art on Current Therapies and Promises for the Future

Malignant pleural mesothelioma (MPM) is a rare, aggressive cancer of the pleural surface associated with asbestos exposure. The median survival of MPM patients is a mere 8-14 months, and there are few biomarkers and no cure available. It is hoped that, eventually, the incidence of MPM will drop and remain low and constant, given that most nations have banned the use of asbestos, but in the meantime, the incidence in Europe is still growing. The exact molecular mechanisms that explain the carcinogenicity of asbestos are not known. Standard therapeutic strategies for MPM include surgery, often coupled with chemotherapy and/or radiotherapy, in a small percentage of eligible patients and chemotherapy in tumors considered unresectable with or without adjuvant radiotherapy. In recent years, several new therapeutic avenues are being explored. These include angiogenesis inhibitors, synthetic lethal treatment, miRNA replacement, oncoviral therapies, and the fast-growing field of immunotherapy alone or in combination with chemotherapy. Of particular promise are the multiple options offered by immunotherapy: immune checkpoint inhibitors, tumor vaccines, and therapies taking advantage of tumor-specific antigens, such as specific therapeutic antibodies or advanced cell-based therapies exemplified by the CAR-T cells. This review comprehensively presents both old and new therapeutic options in MPM, focusing on the results of the numerous recent and on-going clinical trials in the field, including the latest data presented at international meetings (AACR, ASCO, and ESMO) this year, and concludes that more work has to be done in the framework of tailored therapies to identify reliable targets and novel biomarkers to impact MPM management.

The Immune Microenvironment in Mesothelioma: Mechanisms of Resistance to Immunotherapy

Although mesothelioma is the consequence of a protracted immune response to asbestos fibers and characterized by a clear immune infiltrate, novel immunotherapy approaches show less convincing results as compared to those seen in melanoma and non-small cell lung cancer. The immune suppressive microenvironment in mesothelioma is likely contributing to this therapy resistance. Therefore, it is important to explore the characteristics of the tumor microenvironment for explanations for this recalcitrant behavior. This review describes the stromal, cytokine, metabolic, and cellular milieu of mesothelioma, and attempts to make connection with the outcome of immunotherapy trials.

Emerging therapies in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare cancer of the pleural surfaces frequently related to asbestos exposure. It is characterized by a poor prognosis even for patients treated with trimodality therapy, including surgery, chemotherapy and radiotherapy. Moreover, the majority of patients are not candidates for surgery due to disease advanced stage or medical comorbidities. For these patients, the survival rate is even lower and few therapeutic options are currently available. Nevertheless, many interesting novel approaches are under investigation, among which immunotherapy represents one of the most promising emerging strategies. In this review, we will discuss the role of new therapeutic options, particularly immunotherapy, and present the results of the most important and promising clinical trials.

What can independent research for mesothelioma achieve to treat this orphan disease?

Introduction: Malignant pleural mesothelioma (MPM) is a rare neoplasm with a poor prognosis, as current therapies are ineffective. Despite the increased understanding of the molecular biology of mesothelioma, there is still a lack of drugs that dramatically enhance patient survival. Area Covered: This review discusses recent and complete clinical trials supported by the NIH, other U.S. Federal agencies, universities and organizations found on clinicaltrials.gov. Firstly, chemotherapy-based trials are described, followed by immunotherapy and multitargeted therapy. Then we introduce drug repositioning and the use of drug docking as tools to find new interesting molecules. Finally, we highlight potential molecular pathways that may play a role in mesothelioma biology and therapy. Expert Opinion: Numerous biases are present in the clinical trials due to a restricted number of cases, inappropriate endpoints and inaccurate stratification of patients which delay the finding of a treatment for MPM. The most crucial issue of independent research for MPM is the lack of more substantive funding to translate these findings to the clinical setting. However, this approach is not necessarily scientific given the low mutational load of mesothelioma relative to other cancers, and therefore patients need a more solid rationale to have a good chance of successful treatment.

Antisense Oligonucleotides Targeting Angiogenic Factors as Potential Cancer Therapeutics

Cancer is one of the leading causes of death worldwide, and conventional cancer therapies such as surgery, chemotherapy, and radiotherapy do not address the underlying molecular pathologies, leading to inadequate treatment and tumor recurrence. Angiogenic factors, such as EGF, PDGF, bFGF, TGF-β, TGF-α, VEGF, endoglin, and angiopoietins, play important roles in regulating tumor development and metastasis, and they serve as potential targets for developing cancer therapeutics. Nucleic acid-based therapeutic strategies have received significant attention in the last two decades, and antisense oligonucleotide-mediated intervention is a prominent therapeutic approach for targeted manipulation of gene expression. Clinical benefits of antisense oligonucleotides have been recognized by the U.S. Food and Drug Administration, with full or conditional approval of Vitravene, Kynamro, Exondys51, and Spinraza. Herein we review the scope of antisense oligonucleotides that target angiogenic factors toward tackling solid cancers.

Current and Future Management of Malignant Mesothelioma: A Consensus Report from the National Cancer Institute Thoracic Malignancy Steering Committee, International Association for the Study of Lung Cancer, and Mesothelioma Applied Research Foundation

On March 28- 29, 2017, the National Cancer Institute (NCI) Thoracic Malignacy Steering Committee, International Association for the Study of Lung Cancer, and Mesothelioma Applied Research Foundation convened the NCI-International Association for the Study of Lung Cancer- Mesothelioma Applied Research Foundation Mesothelioma Clinical Trials Planning Meeting in Bethesda, Maryland. The goal of the meeting was to bring together lead academicians, clinicians, scientists, and the U.S. Food and Drug Administration to focus on the development of clinical trials for patients in whom malignant pleural mesothelioma has been diagnosed. In light of the discovery of new cancer targets affecting the clinical development of novel agents and immunotherapies in malignant mesothelioma, the objective of this meeting was to assemble a consensus on at least two or three practice-changing multimodality clinical trials to be conducted through NCI's National Clinical Trials Network.

Heterogeneous Contributing Factors in MPM Disease Development and Progression: Biological Advances and Clinical Implications

Malignant pleural mesothelioma (MPM) tumors are remarkably aggressive and most patients only survive for 5–12 months; irrespective of stage; after primary symptoms appear. Compounding matters is that MPM remains unresponsive to conventional standards of care; including radiation and chemotherapy. Currently; instead of relying on molecular signatures and histological typing; MPM treatment options are guided by clinical stage and patient characteristics because the mechanism of carcinogenesis has not been fully elucidated; although about 80% of cases can be linked to asbestos exposure. Several molecular pathways have been implicated in the MPM tumor microenvironment; such as angiogenesis; apoptosis; cell-cycle regulation and several growth factor-related pathways predicted to be amenable to therapeutic intervention. Furthermore, the availability of genomic data has improved our understanding of the pathobiology of MPM. The MPM genomic landscape is dominated by inactivating mutations in several tumor suppressor genes; such as CDKN2A; BAP1 and NF2. Given the complex heterogeneity of the tumor microenvironment in MPM; a better understanding of the interplay between stromal; endothelial and immune cells at the molecular level is required; to chaperone the development of improved personalized therapeutics. Many recent advances at the molecular level have been reported and several exciting new treatment options are under investigation. Here; we review the challenges and the most up-to-date biological advances in MPM pertaining to the molecular pathways implicated; progress at the genomic level; immunological progression of this fatal disease; and its link with developmental cell pathways; with an emphasis on prognostic and therapeutic treatment strategies.

A review of bevacizumab in the treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer with poor prognosis. Systemic chemotherapy is the primary treatment modality for the majority of patients. VEGF plays a key mitogen for MPM cells physiopathology. Bevacizumab, a monoclonal anti-VEGF antibody, was a rational approach to be tested in MPM. Based on the results of the Phase III IFCT-0701 mesothelioma avastin cisplatin pemetrexed study, cisplatin-pemetrexed-bevacizumab is now the accepted standard in France. The National Comprehensive Cancer Network guidelines have also included this combination as an option for standard front-line therapy. This review summarized the efficacy and safety data of bevacizumab in the treatment of patients with MPM.

Promising investigational drug candidates in phase I and phase II clinical trials for mesothelioma

INTRODUCTION

Malignant mesothelioma is a rare and lethal malignancy primarily affecting the pleura and peritoneum. Mesothelioma incidence is expected to increase worldwide and current treatments remain ineffective, leading to poor prognosis. Within this article potential targets to improve the quality of life of the patients and assessment of further avenues for research are discussed. Areas covered: This review highlights emerging therapies currently under investigation for malignant mesothelioma with a specific focus on phase I and phase II clinical trials. Three main areas are discussed: immunotherapy (immune checkpoint blockade and cancer vaccines, among others), multitargeted therapy (such as targeting pro-angiogenic genes) and gene therapy (such as suicide gene therapy). For each, clinical trials are described to detail the current or past investigations at phase I and II. Expert opinion: The approach of applying existing treatments from other cancers does not show significant benefit, with the most promising outcome being an increase in survival of 2.7 months following combination of chemotherapy with bevacizumab. It is our opinion that the hypoxic microenvironment, the role of the stroma, and the metabolic status of mesothelioma should all be assessed and characterised to aid in the development of new treatments to improve patient outcomes.

Novel systemic therapy against malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive tumor of the pleura with an overall poor prognosis. Even with surgical resection, for which only a subset of patients are eligible, long term disease free survival is rare. Standard first-line systemic treatment consists of a platinum analog, an anti-metabolite, and sometimes anti-angiogenic therapy, but there is currently no well-established standard therapy for refractory or relapsed disease. This review focuses on efforts to develop improved systemic therapy for the treatment of malignant pleural mesothelioma (MPM) including cytotoxic systemic therapy, a variety of tyrosine kinase inhibitors and their downstream effector pathways, pharmacologic targeting of the epigenome, novel approaches to target proteins expressed on mesothelioma cells (such as mesothelin), arginine depletion therapy, and the emerging role of immunotherapy. Overall, these studies demonstrate the challenges of improving systemic therapy for MPM and highlight the need to develop therapeutic strategies to control this disease.

Spotlight on bevacizumab and its potential in the treatment of malignant pleural mesothelioma: the evidence to date

Malignant pleural mesothelioma (MPM) is a rare, but aggressive cancer. Surgery and radiation offer limited benefit, and systemic chemotherapy remains the primary treatment modality for the majority of patients. Vascular endothelial growth factor (VEGF) and its receptor have been recognized as important players in the biology of this disease. Bevacizumab is a monoclonal antibody that binds VEGF and blocks its interaction with the VEGF receptor. Recent studies have shown benefit with the addition of bevacizumab to the combination of cisplatin and pemetrexed in MPM. This combination is now included in the National Comprehensive Cancer Network guidelines (with a category 2A recommendation) as a possible first-line treatment for unresectable MPM in appropriately selected patients. This review discusses the rationale behind the use of bevacizumab in MPM, as well as summarizes the pharmacology, efficacy, safety, and toxicity of bevacizumab across multiple trials. The use of small-molecule inhibitors of angiogenesis in the treatment of MPM is also discussed.

Validation of Progression-Free Survival as a Surrogate Endpoint for Overall Survival in Malignant Mesothelioma: Analysis of Cancer and Leukemia Group B and North Central Cancer Treatment Group (Alliance) Trials

PURPOSE

The aim of this study was to investigate whether progression-free survival (PFS) can be considered a surrogate endpoint for overall survival (OS) in malignant mesothelioma.

MATERIALS AND METHODS

Individual data were collected from 15 Cancer and Leukemia Group B (615 patients) and 2 North Central Cancer Treatment Group (101 patients) phase II trials. The effects of 5 risk factors for OS and PFS, including age, histology, performance status (PS), white blood cell count, and European Organisation for Research and Treatment of Cancer (EORTC) risk score, were used in the analysis. Individual-level surrogacy was assessed by Kendall's tau through a Clayton bivariate Copula survival (CBCS) model. Summary-level surrogacy was evaluated via the association between logarithms of the hazard ratio (log HR)-log HR_OS and log HR_PFS-measured in R² from a weighted least-square (WLS) regression model and the CBCS model.

RESULTS

The median PFS for all patients was 3.0 months (95% confidence interval [CI], 2.8-3.5 months) and the median OS was 7.2 months (95% CI, 6.5-8.0 months). Moderate correlations between PFS and OS were observed across all risk factors at the individual level, with Kendall's tau ranging from 0.46 to 0.47. The summary-level surrogacy varied among risk factors. The Copula R² ranged from 0.51 for PS to 0.78 for histology. The WLS R² ranged from 0.26 for EORTC and PS to 0.67 for age.

CONCLUSIONS

The analyses demonstrated low to moderate individual-level surrogacy between PFS and OS. At the summary level, the surrogacy between PFS and OS varied significantly across different risk factors. With a short postprogression survival and a moderate correlation between PFS and OS, there is no evidence that PFS is a valid surrogate endpoint for OS in malignant mesothelioma. The Oncologist 2017;22:189-198Implications for Practice: For better disease management and for more efficient clinical trial designs, it is important to know if progression-free survival (PFS) is a good surrogate endpoint for overall survival in malignant mesothelioma. With a relatively large database of 17 phase II trials and 716 patients from Cancer and Leukemia Group B and North Central Cancer Treatment Group, we conducted statistical analyses and found that there is no evidence to suggest that PFS is a valid surrogate endpoint for OS for malignant mesothelioma. Future research work is needed to find alternative surrogate endpoints for OS.

The resistance related to targeted therapy in malignant pleural mesothelioma: Why has not the target been hit yet?

Malignant pleural mesothelioma (MPM) is an aggressive tumor of the pleura with a poor prognosis. The most active first-line regimens are platinum compounds and pemetrexed. There is no standard second-line treatment in MPM. Advances in the understanding of tumor molecular biology have led to the development of several targeted treatments, which have been evaluated in clinical trials. Unfortunately none of the explored targeted treatments can currently be recommended as routine treatment in MPM. We reviewed the biological pathways involved in MPM, the clinical trials about targeted therapy, and possible related mechanisms of resistance. We suggest that specific genetic markers are needed as targets of selective therapy. By this way the selection of patients based on the molecular profile may facilitate a therapeutic strategy that allows the use of the most appropriate drug for each patient.

Malignant pleural mesothelioma: an update on diagnosis and treatment options

Malignant pleural mesothelioma (MPM) represents a significant diagnostic and therapeutic challenge and is almost always a fatal disease. Imaging abnormalities are common, but have a limited role in distinguishing mesothelioma from metastatic pleural disease. Similarly, minimally invasive biomarkers have shown promise but also have limitations in the diagnosis of mesothelioma. In experienced centers, cytology and immunohistochemistry are now sufficient to diagnose the epithelioid subtype of mesothelioma, which can reduce the need for more invasive diagnostic investigations. Prognosis of MPM is modestly impacted by oncological treatments. Chemotherapy with cisplatin and pemetrexed is considered the standard of care, though the addition of bevacizumab to the platinum doublet may be the new standard of care. New targeted therapies have demonstrated some promise and are being addressed in clinical trials. This review focuses on the current data on the diagnostic and therapeutic issues of MPM.

Closing faucets: the role of anti-angiogenic therapies in malignant pleural diseases

Malignant pleural effusion (MPE) represents 15-35 % of pleural effusions and markedly worsens the prognosis and quality of life of patients with cancer. Malignant mesothelioma (MM) and lung adenocarcinoma are the most frequent primary and secondary causes, respectively, of MPE. Effective treatments for cancer-related MPE are warranted in order to improve symptoms, reduce the number of invasive pleural procedures, and prolong patient life. Since angiogenesis plays a key role in MPE development, the potential role of bevacizumab and other anti-angiogenic therapies have been explored in this review. No relevant phase III trials have specifically analysed the benefit from adding bevacizumab to platinum-based chemotherapy in lung cancer-related MPE. However, small retrospective series reported 71.4-93.3 % MPE control rate, a reduction in invasive procedures, and a safe profile with this combination. Being approved for the first-line treatment of non-squamous advanced NSCLC, the addition of bevacizumab should be considered for patients presenting with MPE. In addition, further studies in this are recommended. In MM, the addition of bevacizumab to platinum-based chemotherapy did not meet primary endpoints in two phase II trials. However, the beneficial results on OS reported in comparison with historical cohorts and the statistically significant benefit on PFS and OS observed in the phase III MAPS trial foretell an eventual role for the combination of platinum/pemetrexed/bevacizumab as front-line systemic therapy for pleural MM. To date, no other anti-angiogenic drug has showed significant benefit in the treatment of patients with either MPE or MM. However, new promising drugs such as ramucirumab or recombinant human endostar warrant further investigation.

New directions in mesothelioma treatment

For most patients with mesothelioma, symptom control and palliative chemotherapy are mainstays of care. First-line cisplatin/pemetrexed chemotherapy has demonstrated survival and quality-of-life benefits. A randomized controlled trial adding bevacizumab to cisplatin and pemetrexed recently reported improved survival and time to progression, and may constitute a new standard of care where economically viable. Immunotherapy is under active investigation and positive results have been reported from single-arm studies of the anti-CTLA4 antibody tremelimumab; the anti-PD-1 antibody pembrolizumab; and mesothelin-targeting strategies. Symptom control remains critical for patient well-being, and includes management of pleural effusion, analgesia, treatment of symptomatic masses and management of systemic symptoms. There is increasing evidence that tunneled pleural catheters are preferred over talc pleurodesis for recurrent pleural effusion.

1-Piperazinylphthalazines as potential VEGFR-2 inhibitors and anticancer agents: Synthesis and in vitro biological evaluation

In our endeavor towards the development of effective VEGFR-2 inhibitors, three novel series of phthalazine derivatives based on 1-piperazinyl-4-arylphthalazine scaffold were synthesized. All the newly prepared phthalazines 16a-k, 18a-e and 21a-g were evaluated in vitro for their inhibitory activity against VEGFR-2. In particular, compounds 16k and 21d potently inhibited VEGFR-2 at sub-micromolar IC50 values 0.35 ± 0.03 and 0.40 ± 0.04 μM, respectively. Moreover, seventeen selected compounds 16c-e, 16g, 16h, 16j, 16k, 18c-e and 21a-g were evaluated for their in vitro anticancer activity according to US-NCI protocol, where compounds 16k and 21d proved to be the most potent anticancer agents. While, compound 16k exhibited potent broad spectrum anticancer activity with full panel GI50 (MG-MID) value of 3.62 μM, compound 21d showed high selectivity toward leukemia and prostate cancer subpanels [subpanel GI50 (MG-MID) 3.51 and 5.15 μM, respectively]. Molecular docking of compounds16k and 21d into VEGFR-2 active site was performed to explore their potential binding mode.

Systemic Approach to Malignant Pleural Mesothelioma: What News of Chemotherapy, Targeted Agents and Immunotherapy?

Malignant pleural mesothelioma is a rare cancer with a cause-effect relationship to asbestos exposure. The prognosis is poor and chemotherapy seems the best treatment option. In the last two decades a deeper understanding of mesothelioma carcinogenesis and invasiveness mechanisms has prompted research efforts to test new agents in patients with malignant pleural mesothelioma, but the results have been modest. Attractive preclinical data disappointed in subsequent experimental phases. Other promising agents failed to improve patient outcomes due to high toxicity. Interesting suggestions have come from preliminary data on immunotherapy. Several trials are ongoing and the results are eagerly awaited. The aim of this review is to discuss the most recent news on systemic therapy for advanced malignant pleural mesothelioma.

Latest developments in our understanding of the pathogenesis of mesothelioma and the design of targeted therapies

Malignant mesothelioma is an aggressive cancer whose pathogenesis is causally linked to occupational exposure to asbestos. Familial clusters of mesotheliomas have been observed in settings of genetic predisposition. Mesothelioma incidence is anticipated to increase worldwide in the next two decades. Novel treatments are needed, as current treatment modalities may improve the quality of life, but have shown modest effects in improving overall survival. Increasing knowledge on the molecular characteristics of mesothelioma has led to the development of novel potential therapeutic strategies, including: molecular targeted approaches, that is the inhibition of vascular endothelial growth factor with bevacizumab; immunotherapy with chimeric monoclonal antibody, immunotoxin, antibody drug conjugate, vaccine and viruses; inhibition of asbestos-induced inflammation, that is aspirin inhibition of HMGB1 activity may decrease or delay mesothelioma onset and/or growth. We elaborate on the rationale behind new therapeutic strategies, and summarize available preclinical and clinical results, as well as efforts still ongoing.

Mesothelioma treatment: Are we on target? A review

Targeted treatment is a therapy directed at a specific molecular target close to a hallmark of cancer. The target should be measurable with a biomarker and measurement of the target should correlate with clinical outcome when targeted treatment is administered. Current clinical guidelines do not recommend targeted or biological therapy in MPM. However, since these recommendations came out, new agents have been investigated in MPM. This review updates the use of targeted and biological treatment in patients with mesothelioma.

Receptor tyrosine kinase inhibitors: Are they real tumor killers?

Inhibiting tumor growth by targeting the tumor vasculature was first proposed by Judah Folkman almost 40 years ago. Since then, different approaches and numerous drugs and agents have been developed to achieve this goal, either with the aim of inhibiting tumor neoangiogenesis or normalizing the tumor vasculature. Among the most promising therapeutic targets are receptor tyrosine kinases (RTKs), some of which are predominantly expressed on tumor endothelial cells, although they are sometimes also present on tumor cells. The majority of RTK inhibitors investigated over the past two decades competes with ATP at the active site of the kinase and therefore block the phosphorylation of intracellular targets. Some of these drugs have been approved for therapy, whereas others are still in clinical trials. Here, we discuss the scientific basis, current status, problems and future prospects of RTK inhibition in anti-tumor therapy.

New and emerging therapeutic options for malignant pleural mesothelioma: review of early clinical trials

Malignant pleural mesothelioma (MPM) is a rare tumor that is challenging to control. Despite some benefit from using the multimodality-approach (surgery, combination chemotherapy and radiation), survival remains poor. However, current research produced a list of potential therapies. Here, we summarize significant new preclinical and early clinical developments in treatment of MPM, which include mesothelin specific antibody and toxin therapies, interleukin-4 (IL-4) receptor toxins, dendritic cell vaccines, immune checkpoint inhibitors, and gene-based therapies. In addition, several local modalities such as photodynamic therapy, postoperative lavage using betadine, and cryotherapy for local recurrence, have also shown to be effective for local control of disease.

Systemic treatment of malignant pleural mesothelioma: new agents in clinical trials raise hope of relevant improvements

PURPOSE OF REVIEW

Malignant pleural mesothelioma (MPM) is a rare malignancy with limited therapeutic options and its incidence is still increasing in both Europe and the developing nations. Prognosis of MPM patients is poor even if the median survival durations have been slightly improved after the introduction of the up-to-date chemotherapy combination with pemetrexed and cisplatin. There is a continuing unmet need to develop better systemic treatment for this disease, but the rarity of the tumor type creates formidable challenges in clinical trial research.

RECENT FINDINGS

Better understanding of the molecular machinery of MPM leads to the design and synthesis of novel compounds targeted against pathways identified as crucial for MPM cell proliferation and metastasis. Most efforts aim at improving standard first-line therapy, or developing effective second-line treatments. Several classes of drugs are currently being explored either in combination with cisplatin and pemetrexed or as single agent for relapsed or progressive MPM.

SUMMARY

This review focuses on several ongoing or recently completed clinical trials investigating novel, promising agents as first-line or second-line therapy for advanced MPM.

Serum amyloid A stimulates cultured endothelial cells to migrate and proliferate: inhibition by the multikinase inhibitor BIBF1120

In the present study, we tested whether serum amyloid A (SAA) protein, an established biomarker of inflammation, also plays a role in stimulating neovascularization. To evaluate this possibility, human carotid artery endothelial (HCtAE) cells were cultured and cellular migration and the proinflammatory and/or thrombotic activity of SAA (0, 1 or 10 μg/mL) on vascular endothelial cells was verified by determining gene regulation relative to control (in the absence of SAA). Exposure of HCtAE cells to SAA increased expression of the transcription factor nuclear factor-κB (NFKB), tumour necrosis factor (TNF) and pro-coagulative tissue factor (F3), and stimulated phosphorylation of the P65 subunit of the NFKB complex. Enhanced production of TNF and NFKB was paralleled by increased vascular endothelial growth factor (VEGF) mRNA and protein expression, as demonstrated by quantitative polymerase chain reaction, western blotting and ELISA. Administration of 10 μg/mL SAA enhanced endothelial cell migration (1.6-fold vs control), stimulated regrowth of HCtAE cells after mechanical injury (~1.2-fold vs control) and increased endothelial tube formation relative to control after 6 h. The SAA-mediated enhancement of endothelial cell migration, proliferation and tube formation were markedly inhibited by pretreatment of HCtAE cells with the multi-angiokinase receptor inhibitor BIBF1120 (100 nmol/L), although SAA-stimulated gene responses for F3 and NFKB were unaffected by 100 nmol/L BIBF1120 pretreatment. Overall, BIBF1120 inhibited the pro-angiogenic activity of SAA on vascular endothelial cells in this experimental model of inflammation.

Phase 2 study of sorafenib in malignant mesothelioma previously treated with platinum-containing chemotherapy

INTRODUCTION

The incidence of mesothelioma is rising. First-line cisplatin and pemetrexed confers a survival benefit, with a median progression-free survival (PFS) of 5.7 months. Sorafenib inhibits tyrosine kinases, including receptors for vascular endothelial growth factor, which are implicated in mesothelioma pathogenesis by preclinical and clinical data.

METHODS

Sorafenib, at 400 mg twice daily, was assessed in a single-arm multicenter phase 2 study, using Simon's two-stage design. Eligible patients had received platinum combination chemotherapy earlier. The primary endpoint was PFS at 6 months, with secondary endpoints, including response rate and metabolic response, assessed using fluorodeoxyglucose positron emission tomography. Published reference values for PFS in mesothelioma provide a benchmark for the null hypothesis of 28% progression-free at 6 months, and for moderate or significant clinical activity of 35% or 43% progression-free at 6 months, respectively.

RESULTS

Fifty-three patients (72%) were treated. Most had epithelioid histology. Ninety-three percent of patients had a performance status 0 or 1. Treatment was well tolerated with few grade 3 or 4 toxicities. Median PFS was 5.1 months, with 36% of patients being progression-free at 6 months. Nine percent of patients remained on study beyond 1 year. Changes in fluorodeoxyglucose positron emission tomography parameters did not predict clinical outcome.

CONCLUSIONS

Sorafenib is well tolerated in patients with mesothelioma after completion of platinum-containing chemotherapy. PFS of sorafenib compares favorably with that reported for other targeted agents, and suggests moderate activity in this disease.

A phase II study of the oral VEGF receptor tyrosine kinase inhibitor vatalanib (PTK787/ZK222584) in myelodysplastic syndrome: Cancer and Leukemia Group B study 10105 (Alliance)

BACKGROUND

Angiogenesis is implicated in the pathophysiology and progression of myelodysplastic syndromes (MDS). Vatalanib (PTK787/ZK222584; Novartis and Schering AG) inhibits receptor tyrosine kinases of vascular endothelial growth factor, platelet derived growth factor and c-Kit. We examined whether vatalanib induces hematological responses in MDS and/or delays progression to acute myeloid leukemia (AML) or death.

METHODS

Two cohorts were studied. Vatalanib 1250 mg orally was given once daily (cohort 1) or 750-1250 mg once daily in an intra-patient dose escalating schedule (cohort 2) in 28-day cycles to 155 patients with MDS; 142 patients were evaluable for response and 153 for toxicity.

RESULTS

The median age was 70.5 years; 51 % had low risk (International Prognostic Scoring System {IPSS} Low/Intermediate-1) and 32 % had high risk (IPSS Intermediate-2/High) MDS. Hematological improvement was achieved in 7/142 (5 %) patients; all 7 were among the 47 patients able to remain on vatalanib for at least 3 months (hematological improvement achieved in 15 % of these 47 patients). For patients with low risk and high risk MDS, respectively, median progression-free survivals were 15 and 6 months, median times to transformation to AML were 28 and 6 months, and median overall survivals were 36 and 10 months. The most frequent non-hematological adverse events grade ≥ 2 were fatigue, nausea or vomiting, dizziness, anorexia, ataxia, diarrhea, and pain. Two deaths (one intra-cerebral hemorrhage and one sudden death) were possibly related to vatalanib.

CONCLUSIONS

Vatalanib induces improvement in blood counts in a small proportion of MDS patients. Clinical applicability is limited by side effects.

Vascular endothelial growth factor (VEGF) receptors: drugs and new inhibitors

The recent launch onto the market of five VEGFR inhibitors indicates the therapeutic value of these agents and the importance of the research in the field of angiogenesis inhibitors for future oncologic therapy. In this Perspective we briefly report the inhibitors that are in clinical use, while we dedicate two wider sections to the compounds that are in clinical trials and to the new derivatives appearing in the literature. We especially consider the medicinal chemistry aspect of the topic and report the structure-activity relationship studies and the binding mode of some inhibitors as well as the biological data of the compounds discovered in the past 5 years.

Cediranib in patients with malignant mesothelioma: a phase II trial of the University of Chicago Phase II Consortium

INTRODUCTION

Malignant mesothelioma (MM) is an aggressive disease with limited therapeutic options. In preclinical models, vascular endothelial growth factor (VEGF) stimulates MM proliferation. In MM patients, higher plasma VEGF levels correlate inversely with survival. Cediranib is an orally administered tyrosine kinase inhibitor of VEGF receptors-1, -2, and -3.

METHODS

We conducted a multi-center phase II trial of cediranib in patients with unresectable, histologically-confirmed MM who had received ≤1 prior regimen of chemotherapy. The primary endpoint was objective response rate. Initial cediranib dosing was 45 mg daily during a 28-day cycle. Due to substantial toxicity, the starting dose was subsequently lowered to 30 mg daily.

RESULTS

Fifty-one patients enrolled at 9 centers; 50 were evaluable for response. Partial responses were observed in 10% of patients; stable disease was seen in 34%. Disease control (PR+SD) was higher at the 45 mg cediranib dose level (67% vs. 34%, p=0.04). Median progression-free survival was 1.8 months (95% CI 0.1, 14.2); median overall survival (OS) was 4.4 months (95% CI 0.9, 41.7). The 1-year survival rate was 15%. Grade 3/4 toxicities were more frequent in the 45 mg dose level group (87% vs. 43%, p=0.002). These included fatigue, hypertension, pulmonary embolism, angioedema, and reversible posterior leukoencephalopathy. Median OS was superior in patients who developed ≥grade 3 hypertension (8.5 vs. 4.1 months, p=0.024).

CONCLUSION

This trial did not meet its pre-specified response endpoint. A higher cediranib dose level was associated with improved disease control, but this dose was poorly tolerated.

A multicenter phase II study of cisplatin, pemetrexed, and bevacizumab in patients with advanced malignant mesothelioma

INTRODUCTION

Malignant mesothelioma (MM) cells express the vascular endothelial growth factor (VEGF) receptor, and VEGF protein expression is detected in a majority of human mesothelioma biopsy specimens. Bevacizumab is a recombinant humanized monoclonal antibody that blocks the binding of VEGF to its receptor. We evaluated the addition of bevacizumab to cisplatin and pemetrexed as first-line treatment in patients with advanced, unresectable MM.

METHODS

Previously untreated MM patients with advanced, unresectable disease received cisplatin (75 mg/m(2)), pemetrexed (500 mg/m(2)), and bevacizumab (15 mg/kg) intravenously every 21 days for a maximum of 6 cycles. Patients with responsive or stable disease received bevacizumab (15 mg/kg) intravenously every 21 days until progression or intolerance. The primary endpoint was progression-free survival rate at 6 months.

RESULTS

53 patients were enrolled at 4 centers; 52 were evaluable for this analysis. The progression-free survival rate at 6 months was 56% and the median progression-free survival was 6.9 months (95% confidence interval [CI], 5.3-7.8 months). The partial response rate was 40% and 35% of patients had stable disease. Median overall survival was 14.8 months (95% CI; 10.0-17.0 months). Grade 3/4 toxicities included neutropenia in 11%, hypertension in 6%, and venous thromboembolism in 13% of patients.

CONCLUSION

This trial evaluating the addition of bevacizumab to cisplatin and pemetrexed in patients with previously untreated, advanced MM failed to meet the primary endpoint of a 33% improvement in the progression-free survival rate at 6 months compared with historical controls treated with cisplatin and pemetrexed alone.