Oncolytic herpesvirus therapy for mesothelioma - A phase I/IIa trial of intrapleural administration of HSV1716

Immunotherapy for Treatment of Pleural Mesothelioma: Current and Emerging Therapeutic Strategies

Pleural mesothelioma is a rare malignancy associated with asbestos exposure and very poor prognosis, with a 5-year overall survival of 12%. Outcomes may vary according to stage at time of diagnosis and histologic subtype. Most recently, clinical trials utilizing dual checkpoint inhibitor regimens and chemotherapy in combination with immune oncologic agents have demonstrated impactful changes in outcomes. In this article, we review studies that have led to the successful implementation of immunotherapy in clinical practice for the treatment of this disease and highlight ongoing clinical trials exploring the use of different immunotherapy strategies for the treatment of pleural mesothelioma. We also discuss the challenges of immunotherapy-based approaches in the context of mesothelioma and future strategies currently being investigated to overcome them.

Progression of oncolytic virus in liver cancer treatment

The liver plays a crucrial role in detoxification, metabolism, and nutrient storage. Because liver cancer ranks among the top three leading causes of death globally, there is an urgent need for developing treatment strategies for liver cancer. Although traditional approaches such as radiation, chemotherapy, surgical removal, and transplantation are widely practiced, the number of patients with liver cancer continues to increase rapidly each year. Some novel therapeutics for liver cancer have been studied for many years. In the past decade, oncolytic therapy has emerged, in which viruses selectively infect and destroy cancer cells while sparing normal cells. However, oncolytic virotherapy for liver cancer remains relatively obscure due to the aggressive nature of the disease and the limited effectiveness of treatment. To keep pace with the latest developments in oncolytic tumor therapy for liver cancer, this review summarizes basic science studies and clinical trials conducted within 5 years, focusing on the efficacy and safety profiles of the five most commonly used oncolytic viruses: herpes simplex virus, adenovirus, influenza virus, vaccinia virus, and coxsackievirus.

Advances in Immunotherapy for Malignant Pleural Mesothelioma: From Emerging Strategies to Translational Insights

MPM stands as a rare malignancy necessitating improved therapeutic strategies due to its limited treatment choices and unfavorable prognosis. The advent of immune checkpoint inhibitors has heralded a paradigm shift in the therapeutic landscape of MPM, offering promising avenues across diverse clinical scenarios. In the context of advanced stages of the disease, Immune check-point inhibitors targeting programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-as-sociated protein 4 (CTLA-4), have exhibited encouraging potential in clinical trials, particularly manifesting efficacy among patients exhibiting disease progression following chemotherapy regimens. Innovative combination regimens, exemplified by the concurrent administration of nivolumab and ipilimumab, have demonstrated marked improvement in survival and patient's benefits. A deeper comprehension of the intricate genetic underpinnings of MPM, encompassing key mutations such as cyclin-dependent kinase inhibitor 2A (CDKN2A), neurofibromin 2 (NF2), and BRCA1-associated protein 1 (BAP1) mutations, has elucidated novel avenues for targeted therapeutic interventions. This review accentuates the transformative capacity of immunotherapy in revolutionizing the therapeutic outlook for MPM, thereby potentially translating into augmented survival rates and offering glimpses of new approaches on the horizon. Despite the persisting challenges, the synergistic crossroads of interdisciplinary research and collaborative clinical endeavors portend a hopeful landscape for MPM treatment.

VP5 protein of oncolytic herpes simplex virus type 2 induces apoptosis in A549 cells through TP53I3 protein

Oncolytic virotherapy stands out as a burgeoning and promising therapeutic paradigm, harnessing the intrinsic cytotoxicity of oncolytic viruses for selective replication and dissemination within tumors. The primary mode of action revolves around the direct eradication of tumor cells. In our previous investigations, we formulated an oncolytic herpes simplex virus type 2 (OH2) and substantiated its anti-tumor efficacy both in vivo and in vitro. Subsequently, we embarked on a phase I/II clinical trial in China (NMPA, 2018L02743) and the USA (FDA, IND 27137) to assess OH2's safety, biodistribution, and anti-tumor activity as a standalone agent in patients with advanced solid tumors. In this investigation, our primary focus was to comprehend the influence of the major capsid protein VP5 of OH2 on its efficacy as an antitumor agent. Our findings underscore that the VP5 protein significantly amplifies OH2's oncolytic impact on A549 cells. Additionally, we observed that VP5 actively promotes the induction of apoptosis in A549 cells, both in vivo and in vitro. Through comprehensive transcriptional sequencing, we further authenticated that the VP5 protein triggers apoptosis-related signaling pathways and Gene Ontology (GO) terms in A549 cells. Moreover, we scrutinized differentially expressed genes in the p53-dependent apoptosis pathway and conducted meticulous in vitro validation of these genes. Subsequently, we delved deeper into unraveling the functional significance of the TP53I3 gene and conclusively affirmed that the VP5 protein induces apoptosis in A549 cells through the TP53I3 gene. These revelations illuminate the underlying mechanisms of OH2's antitumor activity and underscore the pivotal role played by the VP5 protein. The outcomes of our study harbor promising implications for the formulation of effective oncolytic virotherapy strategies in cancer treatment.

An Update on the Clinical Status, Challenges, and Future Directions of Oncolytic Virotherapy for Malignant Gliomas

OPINION STATEMENT

Malignant gliomas are common central nervous system tumors that pose a significant clinical challenge due to the lack of effective treatments. Glioblastoma (GBM), a grade 4 malignant glioma, is the most prevalent primary malignant brain tumor and is associated with poor prognosis. Current clinical trials are exploring various strategies to combat GBM, with oncolytic viruses (OVs) appearing particularly promising. In addition to ongoing and recently completed clinical trials, one OV (Teserpaturev, Delytact®) received provisional approval for GBM treatment in Japan. OVs are designed to selectively target and eliminate cancer cells while promoting changes in the tumor microenvironment that can trigger and support long-lasting anti-tumor immunity. OVs offer the potential to remodel the tumor microenvironment and reverse systemic immune exhaustion. Additionally, an increasing number of OVs are armed with immunomodulatory payloads or combined with immunotherapy approaches in an effort to promote anti-tumor responses in a tumor-targeted manner. Recently completed oncolytic virotherapy trials can guide the way for future treatment individualization through patient preselection, enhancing the likelihood of achieving the highest possible clinical success. These trials also offer valuable insight into the numerous challenges inherent in malignant glioma treatment, some of which OVs can help overcome.

Leveraging the pleural space for anticancer therapies in pleural mesothelioma

Most patients with pleural mesothelioma (PM) present with symptomatic pleural effusion. In some patients, PM is only detectable on the pleural surfaces, providing a strong rationale for intrapleural anticancer therapy. In modern prospective studies involving expert radiological staging and specialist multidisciplinary teams, the population incidence of stage I PM (an approximate surrogate of pleura-only PM) is higher than in historical retrospective series. In this Viewpoint, we advocate for the expansion of intrapleural trials to serve these patients, given the paucity of data supporting licensed systemic therapies in this setting and the uncertainties involved in surgical therapy. We begin by reviewing the unique anatomical and physiological features of the PM-bearing pleural space, before critically appraising the evidence for systemic therapies in stage I PM and previous intrapleural PM trials. We conclude with a summary of key challenges and potential solutions, including optimal trial designs, repurposing of indwelling pleural catheters, and new technologies.

Contemporary management of mesothelioma

Pleural mesothelioma (PM) is an aggressive asbestos-associated thoracic malignancy with a median survival of 12-18 months. Due to continued asbestos use in many nations, global incidence is rising. Causes due to non-occupational, environmental exposure are also rising in many countries despite utilisation bans. For many years, platinum--pemetrexed chemotherapy was the solitary licensed therapy, but first-line combination immune checkpoint blockade has recently demonstrated improved outcomes, with both regimes tested in predominantly late-stage cohorts. In the second-line setting, single-agent nivolumab has been shown to extend survival and is now available for routine use in some regions, while second-line chemotherapy has no proven role and opportunities for clinical trials should be maximised in relapsed disease. Surgery for "technically resectable" disease has been offered for decades in many expert centres, but the recent results from the phase III MARS2 trial have challenged this approach. There remains no robustly proven standard of care for early-stage PM. The clinical trial landscape for PM is complex and increasingly diverse, making further development of specialist PM multidisciplinary teams an important priority in all countries. The observation of improving outcomes in centres that have adopted this service model emphasises the importance of high-quality diagnostics and equitable access to therapies and trials. Novel therapies targeting a range of aberrations are being evaluated; however, a better understanding of the molecular drivers and their associated vulnerabilities is required to identify and prioritise treatment targets.

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.

A promising future in cancer immunotherapy: Oncolytic viruses

Alongside the conventional methods, attention has been drawn to the use of immunotherapy-based methods for cancer treatment. Immunotherapy has developed as a therapeutic option that can be more specific with better outcomes in tumor treatment. It can boost or regulate the immune system behind the targeted virotherapy. Virotherapy is a kind of oncolytic immunotherapy that investigated broadly in cancer treatment in recent decades, due to its several advantages. According to recent advance in the field of understanding cancer cell biology and its occurrence, as well as increasing the knowledge about conditionally replicating oncolytic viruses and their destructive function in the tumor cells, nowadays, it is possible to apply this strategy in the treatment of malignancies. Relying on achievements in clinical trials of oncolytic viruses, we can certainly expect that this therapeutic perception can play a more central role in cancer treatment. In cancer treatment, combination therapy using oncolytic viruses alongside standard cancer treatment methods and other immunotherapy-based treatments can expect more promising results in the future.

Potential targeting of the tumor microenvironment to improve cancer virotherapy

In 2015, oncolytic virotherapy was approved for clinical use, and in 2017, recombinant adeno-associated virus (AAV) delivery was also approved. However, systemic administration remains challenging due to the limited number of viruses that successfully reach the target site. Although the US Food and Drug Administration (FDA) permits the use of higher doses of AAV to achieve greater rates of transduction, most AAV still accumulates in the liver, potentially leading to toxicity there and elsewhere. Targeting the tumor microenvironment is a promising strategy for cancer treatment due to the critical role of the tumor microenvironment in controlling tumor progression and influencing the response to therapies. Newly discovered evidence indicates that administration routes focusing on the tumor microenvironment can promote delivery specificity and transduction efficacy within the tumor. Here, we review approaches that involve modifying viral surface features, modulating the immune system, and targeting the physicochemical characteristics in tumor microenvironment to regulate therapeutic delivery. Targeting tumor acidosis presents advantages that can be leveraged to enhance virotherapy outcomes and to develop new therapeutic approaches that can be integrated with standard treatments.

Oncolytic Viruses: An Inventory of Shedding Data from Clinical Trials and Elements for the Environmental Risk Assessment

Attenuated and/or genetically modified oncolytic viruses (OV) gain increasing interest as a promising approach for cancer therapy. Beside the assessment of subject safety, quality and efficacy aspects of medicinal products for human use, genetically modified viruses are also governed by EU regulatory frameworks requiring an environmental risk assessment (ERA). An important element to be assessed as part of the ERA is the incidence of exposure to OV of individuals, other than the trial subjects, and the environment. The evidence-based evaluation of shedding data is considered to be decisive in that context, as it may impact the OV capacity to be transmitted. This is particularly true for OV still able to (conditionally) replicate as opposed to replication-defective viral vectors commonly used in gene therapy or vaccination. To our knowledge, this article presents the most extensive and up-to-date review of shedding data reported with OV employed in clinics. Besides the identification of a topical need for improving the collection of shedding data, this article aims at providing an aid to the design of an appropriate shedding study, thereby relying on and further complementing principles described in existing guidelines issued by European and international institutions.

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.

Oncolytic virotherapy evolved into the fourth generation as tumor immunotherapy

BACKGROUND

Oncolytic virotherapy (OVT) is a promising anti-tumor modality that utilizes oncolytic viruses (OVs) to preferentially attack cancers rather than normal tissues. With the understanding particularly in the characteristics of viruses and tumor cells, numerous innovative OVs have been engineered to conquer cancers, such as Talimogene Laherparepvec (T-VEC) and tasadenoturev (DNX-2401). However, the therapeutic safety and efficacy must be further optimized and balanced to ensure the superior safe and efficient OVT in clinics, and reasonable combination therapy strategies are also important challenges worthy to be explored.

MAIN BODY

Here we provided a critical review of the development history and status of OVT, emphasizing the mechanisms of enhancing both safety and efficacy. We propose that oncolytic virotherapy has evolved into the fourth generation as tumor immunotherapy. Particularly, to arouse T cells by designing OVs expressing bi-specific T cell activator (BiTA) is a promising strategy of killing two birds with one stone. Amazing combination of therapeutic strategies of OVs and immune cells confers immense potential for managing cancers. Moreover, the attractive preclinical OVT addressed recently, and the OVT in clinical trials were systematically reviewed.

CONCLUSION

OVs, which are advancing into clinical trials, are being envisioned as the frontier clinical anti-tumor agents coming soon.

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.

Intrapleural Anticancer Therapy for Malignant Pleural Diseases: Facts or Fiction?

Malignant pleural diseases involves both primary pleural malignancies (e.g., mesothelioma) as well as metastatic disease involving the pleura. The management of primary pleural malignancies remains a challenge, given their limited response to conventional treatments such as surgery, systemic chemotherapy, and immunotherapy. In this article, we aimed to review the management of primary pleural malignancy as well as malignant pleural effusion and assess the current state of intrapleural anticancer therapies. We review the role intrapleural chemotherapy, immunotherapy, and immunogene therapy, as well as oncolytic viral, therapy and intrapleural drug device combination. We further discuss that while the pleural space offers a unique opportunity for local therapy as an adjuvant option to systemic therapy and may help decrease some of the systemic side effects, further patient outcome-oriented research is needed to determine the exact role of these treatments within the armamentarium of currently available options.

The Clinical Advances of Oncolytic Viruses in Cancer Immunotherapy

A promising future for oncology treatment has been brought about by the emergence of a novel approach utilizing oncolytic viruses in cancer immunotherapy. Oncolytic viruses are viruses that have been exploited genetically to assault malignant cells and activate a robust immune response. Several techniques have been developed to endow viruses with an oncolytic activity through genetic engineering. For instance, redirection capsid modification, stimulation of anti-neoplastic immune response, and genetically arming viruses with cytokines such as IL-12. Oncolytic viral clinical outcomes are sought after, particularly in more advanced cancers. The effectiveness and safety profile of the oncolytic virus in clinical studies with or without the combination of standard treatment (chemotherapy, radiotherapy, or primary excision) has been assessed using response evaluation criteria in solid tumors (RECIST). This review will comprehensively outline the most recent clinical applications and provide the results from various phases of clinical trials in a variety of cancers in the latest published literature.

Oncolytic virotherapy in lung cancer

Lung tumors are one of the most aggressive threats affecting humans. Current therapeutic approaches have improved patients' survival; however, further efforts are required to increase effectiveness and protection against tumor relapse and metastasis. Immunotherapy presents an alternative to previous treatments that focuses on stimulating of the patient's immune system to destroy tumor cells. Viruses can be used as part of the immune therapeutic approach as agents that could selectively infect tumor cells, triggering an immune response against the infection and against the tumor cells. Some viruses have been selected for specifically infecting and destroying cancer cells, activating the immune response, enhancing access, amplifying the cytotoxicity against the tumor cells, and improving the long-term memory that can prevent tumor relapse. Oncolytic virotherapy can then be used as a strategy to target the destruction of transformed cells at the tumor site and act in locations distant from the primary targeted tumor site. Some of the current challenges in lung cancer treatment can be addressed using traditional therapies combined with oncolytic virotherapy. Defining the best combination, including the choice of the right settings will be at the next frontier in lung cancer treatment.

The Dilemma of HSV-1 Oncolytic Virus Delivery: The Method Choice and Hurdles

Oncolytic viruses (OVs) have emerged as effective gene therapy and immunotherapy drugs. As an important gene delivery platform, the integration of exogenous genes into OVs has become a novel path for the advancement of OV therapy, while the herpes simplex virus type 1 (HSV-1) is the most commonly used. However, the current mode of administration of HSV-1 oncolytic virus is mainly based on the tumor in situ injection, which limits the application of such OV drugs to a certain extent. Intravenous administration offers a solution to the systemic distribution of OV drugs but is ambiguous in terms of efficacy and safety. The main reason is the synergistic role of innate and adaptive immunity of the immune system in the response against the HSV-1 oncolytic virus, which is rapidly cleared by the body's immune system before it reaches the tumor, a process that is accompanied by side effects. This article reviews different administration methods of HSV-1 oncolytic virus in the process of tumor treatment, especially the research progress in intravenous administration. It also discusses immune constraints and solutions of intravenous administration with the intent to provide new insights into HSV-1 delivery for OV therapy.

Oncolytic viral vectors in the era of diversified cancer therapy: from preclinical to clinical

With the in-depth research and wide application of immunotherapy recently, new therapies based on oncolytic viruses are expected to create new prospects for cancer treatment via eliminating the suppression of the immune system by tumors. Currently, an increasing number of viruses are developed and engineered, and various virus vectors based on effectively stimulating human immune system to kill tumor cells have been approved for clinical treatment. Although the virus can retard the proliferation of tumor cells, the choice of oncolytic viruses in biological cancer therapy is equally critical given their therapeutic efficacy, safety and adverse effects. Moreover, previously known oncolytic viruses have not been systematically classified. Therefore, in this review, we summarized and distinguished the characteristics of several common types of oncolytic viruses: herpes simplex virus, adenovirus, measles virus, Newcastle disease virus, reovirus and respiratory syncytial virus. Subsequently, we outlined that these oncolytic viral vectors have been transformed from preclinical studies in combination with immunotherapy, radiotherapy, chemotherapy, and nanoparticles into clinical therapeutic strategies for various advanced solid malignancies or circulatory system cancers.

Herpes simplex virus 1 as an oncolytic viral therapy for refractory cancers

The need for efficacious and non-toxic cancer therapies is paramount. Oncolytic viruses (OVs) are showing great promise and are introducing new possibilities in cancer treatment with their ability to selectively infect tumor cells and trigger antitumor immune responses. Herpes Simplex Virus 1 (HSV-1) is a commonly selected OV candidate due to its large genome, relative safety profile, and ability to infect a variety of cell types. Talimogene laherparevec (T-VEC) is an HSV-1-derived OV variant and the first and only OV therapy currently approved for clinical use by the United States Food and Drug Administration (FDA). This review provides a concise description of HSV-1 as an OV candidate and the genomic organization of T-VEC. Furthermore, this review focuses on the advantages and limitations in the use of T-VEC compared to other HSV-1 OV variants currently in clinical trials. In addition, approaches for future directions of HSV-1 OVs as cancer therapy is discussed.

Understanding Immune Responses to Viruses-Do Underlying Th1/Th2 Cell Biases Predict Outcome?

Emerging and re-emerging viral diseases have increased in number and geographical extent during the last decades. Examples include the current COVID-19 pandemic and the recent epidemics of the Chikungunya, Ebola, and Zika viruses. Immune responses to viruses have been well-characterised within the innate and adaptive immunity pathways with the outcome following viral infection predominantly attributed to properties of the virus and circumstances of the infection. Perhaps the belief that the immune system is often considered as a reactive component of host defence, springing into action when a threat is detected, has contributed to a poorer understanding of the inherent differences in an individual's immune system in the absence of any pathology. In this review, we focus on how these host factors (age, ethnicity, underlying pathologies) may skew the T helper cell response, thereby influencing the outcome following viral infection but also whether we can use these inherent biases to predict patients at risk of a deviant response and apply strategies to avoid or overcome them.

Novel Insights Into Mesothelioma Therapy: Emerging Avenues and Future Prospects

Malignant mesothelioma is a rare and aggressive cancer that develops in the thin layer surrounding the mesothelium and is mainly caused by asbestos exposure. Despite improvements in patient prognosis with conventional cancer treatments, such as surgery, chemotherapy, and radiotherapy, there are still no curative treatment modalities for advanced disease. In recent years, new therapeutic avenues have been explored. Improved understanding of the mechanisms underlying the dynamic tumor interaction with the immune system has led to the development of immunotherapeutic approaches. Numerous recent clinical trials have shown a desire to develop more effective treatments that can be used to fight against the disease. Immune checkpoint inhibitors, oncolytic adenoviruses, and their combination represent a promising strategy that can be used to synergistically overcome immunosuppression in the mesothelioma tumor microenvironment. This review provides a synthesized overview of the current state of knowledge on new therapeutic options for mesothelioma with a focus on the results of clinical trials conducted in the field.

Inconsistencies in Modeling the Efficacy of the Oncolytic Virus HSV1716 Reveal Potential Predictive Biomarkers for Tolerability

Treatment with HSV1716 via intralesional administration has proven successful for melanoma patients with the hope that oncolytic virotherapy would become another weapon in the systemic anticancer therapy (SACT) arsenal. In addition to challenges surrounding the systemic delivery of oncolytic viruses (OVs), problems associated with its in vivo modeling have resulted in low predictive power, contributing to the observed disappointing clinical efficacy. As OV's efficacy is elicited through interaction with the immune system, syngeneic orthotopic mouse models offer the opportunity to study these with high reproducibility and at a lower cost; however, inbred animals display specific immune characteristics which may confound results. The systemic delivery of HSV1716 was, therefore, assessed in multiple murine models of breast cancer. Tolerability to the virus was strain-dependent with C57/Bl6, the most tolerant and Balb/c experiencing lethal side effects, when delivered intravenously. Maximum tolerated doses were not enough to demonstrate efficacy against tumor growth rates or survival of Balb/c and FVB mouse models; therefore; the most susceptible strain (Balb/c mice) was treated with immunomodulators prior to virus administration in an attempt to reduce side effects. These studies demonstrate the number of variables to consider when modeling the efficacy of OVs and the complexities involved in their interpretation for translational purposes. By reporting these observations, we have potentially revealed a role for T-cell helper polarization in viral tolerability. Importantly, these findings were translated to human studies, whereby a Th1 cytokine profile was expressed in pleural effusions of patients that responded to HSV1716 treatment for malignant pleural mesothelioma with minimal side effects, warranting further investigation as a biomarker for predictive response.

Immunotherapy for mesothelioma: Moving beyond single immune check point inhibition

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm with low survival rates. Platinum-based chemotherapy has represented the cornerstone of treatment for over a decade, prompting the investigation of new therapeutic strategies both in the early stage of the disease and in the advanced setting. The advent of immune check-point inhibitors (ICIs) has recently revamped the enthusiasm for using immunotherapy also in MPM. However, results from first clinical trials using single immune check-point inhibition have been conflicting, and this may be mainly attributed to the lack of specific biomarkers as well as to intra- and inter- patient heterogeneity. The phase III Checkmate743 firstly demonstrated the superiority of an ICI combination (nivolumab plus ipilimumab) over chemotherapy in the first-line treatment of unresectable MPM, leading to FDA approval of this regimen and showing that moving beyond single immune check point inhibition might be a successful strategy to overcome resistance in the majority of MPM patients. In this review, we describe the emerging immunotherapy strategies for the treatment of MPM. We also discuss how refining the approach in pre-clinical studies towards a more holistic perspective (which takes into account not only genetic but also pathophysiological vulnerabilities) and strengthening multi-institutional collaboration in clinical trials is finally helping the clinical development of immunotherapy in MPM.

Current Management and Future Perspective in Pleural Mesothelioma

Pleural mesothelioma is an aggressive malignancy arising from pleural mesothelial cell lining, predominantly associated with prior exposure to asbestos. The ban on asbestos use has led to its lower incidence in many countries, but globally the disease burden is expected to rise. Therefore, well-planned research is needed to develop more effective, tolerable and affordable drugs. The development of novel treatment has been too slow, with only two regimens of systemic therapy with robust phase 3 data approved formally to date. The treatment scenario for resectable disease remains controversial. However, recent developments in the understanding of disease and clinical trials have been encouraging, and may add better treatment options in the coming years. In this review, we discuss the current treatment options for pleural mesothelioma and shed light on some recent studies and ongoing trials.

A Glimpse in the Future of Malignant Mesothelioma Treatment

Malignant mesothelioma (MMe) is a rare neoplasm with few therapeutic options available. The landscape of effective therapy for this disease remained unchanged in the last two decades. Recently, however, the introduction of Immune Checkpoint Inhibitors (ICIs) led to small, but nevertheless, promising improvements. However, many efforts are still needed to radically improve the prognosis of MMe. In this review, we analyze all those therapeutic strategies for MMe that are still in a preclinical or early clinical phase of development. In particular, we focus on novel antiangiogenic drugs and their possible combination with immunotherapy. Furthermore, we describe also more complex strategies such as microRNA-loaded vectors, oncolytic viruses, and engineered lymphocytes.

In Situ Cancer Vaccination and Immunovirotherapy Using Oncolytic HSV

Herpes simplex virus (HSV) can be genetically altered to acquire oncolytic properties so that oncolytic HSV (oHSV) preferentially replicates in and kills cancer cells, while sparing normal cells, and inducing anti-tumor immune responses. Over the last three decades, a better understanding of HSV genes and functions, and improved genetic-engineering techniques led to the development of oHSV as a novel immunovirotherapy. The concept of in situ cancer vaccination (ISCV) was first introduced when oHSV was found to induce a specific systemic anti-tumor immune response with an abscopal effect on non-injected tumors, in the process of directly killing tumor cells. Thus, the use of oHSV for tumor vaccination in situ is antigen-agnostic. The research and development of oHSVs have moved rapidly, with the field of oncolytic viruses invigorated by the FDA/EMA approval of oHSV talimogene laherparepvec in 2015 for the treatment of advanced melanoma. Immunovirotherapy can be enhanced by arming oHSV with immunomodulatory transgenes and/or using them in combination with other chemotherapeutic and immunotherapeutic agents. This review offers an overview of the development of oHSV as an agent for ISCV against solid tumors, describing the multitude of different oHSVs and their efficacy in immunocompetent mouse models and in clinical trials.

The Effect of Herpes Simplex Virus-Type-1 (HSV-1) Oncolytic Immunotherapy on the Tumor Microenvironment

The development of cancer causes disruption of anti-tumor immunity required for surveillance and elimination of tumor cells. Immunotherapeutic strategies aim for the restoration or establishment of these anti-tumor immune responses. Cancer immunotherapies include immune checkpoint inhibitors (ICIs), adoptive cellular therapy (ACT), cancer vaccines, and oncolytic virotherapy (OVT). The clinical success of some of these immunotherapeutic modalities, including herpes simplex virus type-1 derived OVT, resulted in Food and Drug Administration (FDA) approval for use in treatment of human cancers. However, a significant proportion of patients do not respond or benefit equally from these immunotherapies. The creation of an immunosuppressive tumor microenvironment (TME) represents an important barrier preventing success of many immunotherapeutic approaches. Mechanisms of immunosuppression in the TME are a major area of current research. In this review, we discuss how oncolytic HSV affects the tumor microenvironment to promote anti-tumor immune responses. Where possible we focus on oncolytic HSV strains for which clinical data is available, and discuss how these viruses alter the vasculature, extracellular matrix and immune responses in the tumor microenvironment.