Applications of coxsackievirus A21 in oncology

Oncolytic viruses: a promising therapy for malignant pleural effusion and solid tumors

Oncolytic viruses (OVs) are natural or recombinant viruses that can directly lyse tumor cells without damaging normal cells. They enhance anti-tumor immunity by releasing antigens and activating inflammatory responses within the tumor microenvironment (TME). This offers a new therapeutic approach for MPE and solid tumors. This review discusses the progress of OVs administered via intrapleural and intratumoral routes, emphasizing their potential in MPE treatment and the challenges posed by the complex intrapleural environment, which affects the direct interaction between OVs, tumor cells, and immune cells. This review also discusses the regulatory barriers, safety concerns and accessibility of oncolytic virus therapy.

Viral Vector-Based Cancer Vaccines

Viral vectors have been frequently used as vaccine-delivery vehicles. Both DNA and RNA viruses have been employed for vaccine development. Viral vectors based on adenoviruses (Ad), adeno-associated viruses (AAV), herpes simplex viruses (HSV), lentiviruses (LV), alphaviruses, flaviviruses, measles viruses (MV), rhabdoviruses, Newcastle disease virus (NDV), poxviruses and picornaviruses have been utilized. Approaches have included the expression of tumor-associated antigens and immunostimulatory genes as well as administration of oncolytic viruses. Prophylactic and therapeutic proof-of-concept has been established in preclinical animal tumor models, and therapeutic efficacy has been obtained in clinical trials in human cancer patients. Model viral vector systems and their applications in cancer vaccine development are described here.

The Potential of Oncolytic Virotherapy in the Treatment of Head and Neck Cancer: A Comprehensive Review

Head and neck cancer (HNC) represents a challenging oncological entity with significant morbidity and mortality rates. Despite advances in conventional therapies, including surgery, chemotherapy, and radiation therapy, the overall survival rates for advanced HNC remain suboptimal. In recent years, the emerging field of oncolytic virotherapy has gained attention as a promising therapeutic approach for various malignancies, including HNC. This review provides a comprehensive overview of the current understanding of oncolytic viruses (Ovs) in the context of HNC treatment, including their mechanisms of action, preclinical and clinical studies, challenges, and future directions. Future oncolytic virotherapy focuses on improving delivery and specificity through nanoparticle carriers and genetic modifications to enhance tumor targeting and immune response. Combining different OVs and integrating them with immunotherapies, such as checkpoint inhibitors, could overcome tumor resistance and improve outcomes. Personalized approaches and rigorous clinical trials are key to ensuring the safety and effectiveness of virotherapy in treating HNC.

Oncolytic Coxsackievirus B3 Strain PD-H Is Effective Against a Broad Spectrum of Pancreatic Cancer Cell Lines and Induces a Growth Delay in Pancreatic KPC Cell Tumors In Vivo

Pancreatic cancer is one of the deadliest cancers globally, with limited success from existing therapies, including chemotherapies and immunotherapies like checkpoint inhibitors for patients with advanced pancreatic ductal adenocarcinoma (PDAC). A promising new approach is the use of oncolytic viruses (OV), a form of immunotherapy that has been demonstrated clinical effectiveness in various cancers. Here we investigated the potential of the oncolytic coxsackievirus B3 strain (CVB3) PD-H as a new treatment for pancreatic cancer. In vitro, PD-H exhibited robust replication, as measured by plaque assays, and potent lytic activity, as assessed by XTT assays, in most pancreatic tumor cell lines, outperforming two other coxsackievirus strains tested, H3N-375/1TS and CVA21. Thus, H3N-375/1TS showed efficient replication and lytic efficiency in distinctly fewer tumor cell lines, while most tumor cells were resistant to CVA21. The oncolytic efficiency of the three OV largely correlated with mRNA expression levels of viral receptors and their ability to induce apoptosis, as measured by cleaved caspase 3/7 activity in the tumor cells. In a syngeneic mouse model with subcutaneous pancreatic tumors, intratumoral administration of PD-H significantly inhibited tumor growth but did not completely stop tumor progression. Importantly, no virus-related side effects were observed. Although pancreatic tumors respond to PD-H treatment, its therapeutic efficacy is limited. Combining PD-H with other treatments, such as those aiming at reducing the desmoplastic stroma which impedes viral infection and spread within the tumor, may enhance its efficacy.

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.

Receptors and Host Factors for Enterovirus Infection: Implications for Cancer Therapy

Enteroviruses, with their diverse clinical manifestations ranging from mild or asymptomatic infections to severe diseases such as poliomyelitis and viral myocarditis, present a public health threat. However, they can also be used as oncolytic agents. This review shows the intricate relationship between enteroviruses and host cell factors. Enteroviruses utilize specific receptors and coreceptors for cell entry that are critical for infection and subsequent viral replication. These receptors, many of which are glycoproteins, facilitate virus binding, capsid destabilization, and internalization into cells, and their expression defines virus tropism towards various types of cells. Since enteroviruses can exploit different receptors, they have high oncolytic potential for personalized cancer therapy, as exemplified by the antitumor activity of certain enterovirus strains including the bioselected non-pathogenic Echovirus type 7/Rigvir, approved for melanoma treatment. Dissecting the roles of individual receptors in the entry of enteroviruses can provide valuable insights into their potential in cancer therapy. This review discusses the application of gene-targeting techniques such as CRISPR/Cas9 technology to investigate the impact of the loss of a particular receptor on the attachment of the virus and its subsequent internalization. It also summarizes the data on their expression in various types of cancer. By understanding how enteroviruses interact with specific cellular receptors, researchers can develop more effective regimens of treatment, offering hope for more targeted and efficient therapeutic strategies.

Tutorial: design, production and testing of oncolytic viruses for cancer immunotherapy

Oncolytic viruses (OVs) represent a novel class of cancer immunotherapy agents that preferentially infect and kill cancer cells and promote protective antitumor immunity. Furthermore, OVs can be used in combination with established or upcoming immunotherapeutic agents, especially immune checkpoint inhibitors, to efficiently target a wide range of malignancies. The development of OV-based therapy involves three major steps before clinical evaluation: design, production and preclinical testing. OVs can be designed as natural or engineered strains and subsequently selected for their ability to kill a broad spectrum of cancer cells rather than normal, healthy cells. OV selection is further influenced by multiple factors, such as the availability of a specific viral platform, cancer cell permissivity, the need for genetic engineering to render the virus non-pathogenic and/or more effective and logistical considerations around the use of OVs within the laboratory or clinical setting. Selected OVs are then produced and tested for their anticancer potential by using syngeneic, xenograft or humanized preclinical models wherein immunocompromised and immunocompetent setups are used to elucidate their direct oncolytic ability as well as indirect immunotherapeutic potential in vivo. Finally, OVs demonstrating the desired anticancer potential progress toward translation in patients with cancer. This tutorial provides guidelines for the design, production and preclinical testing of OVs, emphasizing considerations specific to OV technology that determine their clinical utility as cancer immunotherapy agents.

miRNA-Mediated Mechanisms in the Generation of Effective and Safe Oncolytic Viruses

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by inhibiting the translation of target transcripts. The expression profiles of miRNAs vary in different tissues and change with the development of diseases, including cancer. This feature has begun to be used for the modification of oncolytic viruses (OVs) in order to increase their selectivity and efficacy. OVs represent a relatively new class of anticancer drugs; they are designed to replicate in cancer tumors and destroy them. These can be natural viruses that can replicate within cancer tumor cells, or recombinant viruses created in laboratories. There are some concerns regarding OVs' toxicity, due to their ability to partially replicate in healthy tissues. In addition, lytic and immunological responses upon OV therapy are not always sufficient, so various OV editing methods are used. This review discusses the latest results of preclinical and clinical studies of OVs, modifications of which are associated with the miRNA-mediated mechanism of gene silencing.

Cancer therapy with the viral and bacterial pathogens: The past enemies can be considered the present allies

Cancer continues to be one of the leading causes of mortality worldwide despite significant advancements in cancer treatment. Many difficulties have arisen as a result of the detrimental consequences of chemotherapy and radiotherapy as a common cancer therapy, such as drug inability to penetrate deep tumor tissue, and also the drug resistance in tumor cells continues to be a major concern. These obstacles have increased the need for the development of new techniques that are more selective and effective against cancer cells. Bacterial-based therapies and the use of oncolytic viruses can suppress cancer in comparison to other cancer medications. The tumor microenvironment is susceptible to bacterial accumulation and proliferation, which can trigger immune responses against the tumor. Oncolytic viruses (OVs) have also gained considerable attention in recent years because of their potential capability to selectively target and induce apoptosis in cancer cells. This review aims to provide a comprehensive summary of the latest literature on the role of bacteria and viruses in cancer treatment, discusses the limitations and challenges, outlines various strategies, summarizes recent preclinical and clinical trials, and emphasizes the importance of optimizing current strategies for better clinical outcomes.

Global landscape of coxsackieviruses in human health

Coxsackieviruses-induced infections, particularly in infants and young children, are one of the most important public health issues in low- and middle-income countries, where the surveillance system varies substantially, and these manifestations have been disregarded. They are widespread throughout the world and are responsible for a broad spectrum of human diseases, from mildly symptomatic conditions to severe acute and chronic disorders. Coxsackieviruses (CV) have been found to have 27 identified genotypes, with overlaps in clinical phenotypes between genotypes. In this review, we present a concise overview of the most recent studies and findings of coxsackieviruses-associated disorders, along with epidemiological data that provides comprehensive details on the distribution, variability, and clinical manifestations of different CV types. We also highlight the significant roles that CV infections play in the emergence of neurodegenerative illnesses and their effects on neurocognition. The current role of CVs in oncolytic virotherapy is also mentioned. This review provides readers with a better understanding of coxsackieviruses-associated disorders and pointing the impact that CV infections can have on different organs with variable pathogenicity. A deeper knowledge of these infections could have implications in designing current surveillance and prevention strategies related to severe CVs-caused infections, as well as encourage studies to identify the emergence of more pathogenic types and the etiology of the most common and most severe disorders associated with coxsackievirus infection.

Development of a robust cell-based potency assay for a coxsackievirus A21 oncolytic virotherapy

Oncolytic viruses (OV) are part of a burgeoning field of investigational oncolytic therapy (OT), in which lytic viruses dissolve advanced tumors productively and specifically. One such OT is a Coxsackievirus A21 (CVA21) based OV that is currently under clinical evaluation. A tissue culture infectious dose (TCID50) assay was used for CVA21 potency release and stability testing in early clinical development. The titer measured in this method was an extrapolated value from cytopathic effect (CPE) observed during the serial dilution but doesn't represent direct viral killing of cells. Moreover, the assay was not deemed to be optimal to carry into late phase clinical development due to limitations in assay precision, turn-around time, and sample throughput. To address these points, we developed a plaque assay to measure viral plaque forming units to measure the potency value for drug substance (DS), drug product (DP) and virus seed (master and working) stocks. In this manuscript, we describe the steps taken to develop this plaque assay for the late-stage clinical development, which include the assay qualification, validation, and robustness protocols, and describe statistical methods for data analysis. Moreover, the method was validated for linearity, accuracy, precision, and specificity. Furthermore, the plaque assay quantifies OV infectivity with better precision (32% vs 58%), with higher sample throughput (22 samples/week vs 3 samples/week) and shorter assay turnaround time (4 days vs 7 days) than the TCID50 method. This assay development strategy can provide guidance for the development of robust cell-based potency methods for OVs and other infectious viral products.

The Effects of Mesenchymal Stem Cells Loaded with Oncolytic Coxsackievirus A21 on Mouse Models of Colorectal Cancer

BACKGROUND

Cancer is a major cause of death worldwide. Colorectal cancer is the second most common type. Additional treatments like chemotherapy and radiation therapy may be recommended. Developing new techniques is vital due to drug resistance and a lack of targeted therapies.

OBJECTIVE

In this study, the effects of mesenchymal stem cells (MSCs) loaded with oncolytic Coxsackievirus A21 (CVA21) on a mouse model of CRC were investigated.

METHODS

The therapeutic potency of MSCs loaded with oncolytic CVA21 were evaluated in an experimental mouse model of colorectal cancer which received an injection CT26 cells per mouse subcutaneously. Splenocyte proliferation index, lactate dehydrogenase (LDH) assay, nitric oxide (NO) production assessment, and cytokine assay (IFN-γ, IL-4, IL-10, and TGF-β) in the splenocyte supernatant were all used to evaluate the impact of MSCs loaded with CVA21.

RESULTS

The results of this study showed that the treatment of a mouse model of colorectal cancer with MSCs loaded with oncolytic CVA21 could significantly suppress the tumor growth, which was accompanied by stimulation of splenocytes proliferation index, an increase of NO and LDH. Also, MSCs loaded with oncolytic CVA21 increased the secretion of IFN-γ and decreased the secretion of IL-4, IL-10, and TGF-β.

CONCLUSION

The results of the current study suggest that MSCs loaded with oncolytic CVA21 therapy for the CRC mouse model may have some potential advantages. On the other hand, the results of the study showed that, in addition to activating the acquired immune system, the use of MSCs loaded with oncolytic CVA21 also stimulates the innate immune system by increasing level of nitric oxide.

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.

Hypoxia effects on oncolytic virotherapy in Cancer: Friend or Foe?

Researchers have tried to find novel strategies for cancer treatment in the past decades. Among the utilized methods, administering oncolytic viruses (OVs) alone or combined with other anticancer therapeutic approaches has had promising outcomes, especially in solid tumors. Infecting the tumor cells by these viruses can lead to direct lysis or induction of immune responses. However, the immunosuppressive tumor microenvironment (TME) is considered a significant challenge for oncolytic virotherapy in treating cancer. Based on OV type, hypoxic conditions in the TME can accelerate or repress virus replication. Therefore, genetic manipulation of OVs or other molecular modifications to reduce hypoxia can induce antitumor responses. Moreover, using OVs with tumor lysis capability in the hypoxic TME may be an attractive strategy to overcome the limitations of the therapy. This review summarizes the latest information available in the field of cancer virotherapy and discusses the dual effect of hypoxia on different types of OVs to optimize available related therapeutic methods.

Oncolytic Virus Engineering and Utilizations: Cancer Immunotherapy Perspective

Oncolytic viruses have positively impacted cancer immunotherapy over the past 20 years. Both natural and genetically modified viruses have shown promising results in treating various cancers. Various regulatory authorities worldwide have approved four commercial oncolytic viruses, and more are being developed to overcome this limitation and obtain better anti-tumor responses in clinical trials at various stages. Faster advancements in translating research into the commercialization of cancer immunotherapy and a comprehensive understanding of the modification strategies will widen the current knowledge of future technologies related to the development of oncolytic viruses. In this review, we discuss the strategies of virus engineering and the progress of clinical trials to achieve virotherapeutics.

Therapeutic potential of oncolytic viruses in the era of precision oncology

Oncolytic virus (OV) therapy has been shown to be an effective targeted cancer therapy treatment in recent years, providing an avenue of treatment that poses no damage to surrounding healthy tissues. Not only do OVs cause direct oncolysis, but they also amplify both innate and adaptive immune responses generating long-term anti-tumour immunity. Genetically engineered OVs have become the common promising strategy to enhance anti-tumour immunity, safety, and efficacy as well as targeted delivery. The studies of various OVs have been accomplished through phase I-III clinical trial studies. In addition, the uses of carrier platforms of organic materials such as polymer chains, liposomes, hydrogels, and cell carriers have played a vital role in the potentially targeted delivery of OVs. The mechanism, rational design, recent clinical trials, applications, and the development of targeted delivery platforms of OVs will be discussed in this review.

Glutathione affinity chromatography for the scalable purification of an oncolytic virus immunotherapy from microcarrier cell culture

Therapeutic viral vectors are an emerging technology with several clinical applications in gene therapy, vaccines, and immunotherapy. Increased demand has required the redevelopment of conventional, low-throughput cell culture and purification manufacturing methods such as static cell stacks and ultracentrifugation. In this work, scalable methods were investigated for the manufacture of an oncolytic virus immunotherapy application consisting of a prototype strain of coxsackievirus A21 (CVA21) produced in adherent MRC-5 cells. Cell culture was established in stirred-tank microcarrier bioreactors, and an efficient affinity chromatography method was developed for the purification of harvested CVA21 through binding of the viral capsids to an immobilized glutathione (GSH) ligand. Bioreactor temperature during infection was investigated to maximize titer, and a decrease in temperature from 37°C to 34°C yielded a two-three-fold increase in infectivity. After purification of the 34°C harvests, the GSH affinity chromatography elution not only maintained a >two-fold increase in infectivity and viral genomes but also increased the proportion of empty capsids compared to 37°C harvests. Using material generated from both infection temperature setpoints, chromatographic parameters and mobile phase compositions were studied at the laboratory scale to maximize infectious particle yields and cell culture impurity clearance. Empty capsids that co-eluted with full capsids from 34°C infection temperature harvests were poorly resolved across the conditions tested, but subsequent polishing anion exchange and cation exchange chromatography steps were developed to clear residual empty capsids and other impurities. Oncolytic CVA21 production was scaled-up 75-fold from the laboratory scale and demonstrated across seven batches in 250 L single-use microcarrier bioreactors and purified with customized, prepacked, single-use 1.5 L GSH affinity chromatography columns. The large-scale bioreactors controlled at 34°C during infection maintained a three-fold increase in productivity in the GSH elution, and excellent clearance of host cell and media impurities was observed across all batches. This study presents a robust method for the manufacture of an oncolytic virus immunotherapy application that may be implemented for the scalable production of other viruses and viral vectors which interact with glutathione.

Development and application of oncolytic viruses as the nemesis of tumor cells

Viruses and tumors are two pathologies that negatively impact human health, but what occurs when a virus encounters a tumor? A global consensus among cancer patients suggests that surgical resection, chemotherapy, radiotherapy, and other methods are the primary means to combat cancer. However, with the innovation and development of biomedical technology, tumor biotherapy (immunotherapy, molecular targeted therapy, gene therapy, oncolytic virus therapy, etc.) has emerged as an alternative treatment for malignant tumors. Oncolytic viruses possess numerous anti-tumor properties, such as directly lysing tumor cells, activating anti-tumor immune responses, and improving the tumor microenvironment. Compared to traditional immunotherapy, oncolytic virus therapy offers advantages including high killing efficiency, precise targeting, and minimal side effects. Although oncolytic virus (OV) therapy was introduced as a novel approach to tumor treatment in the 19th century, its efficacy was suboptimal, limiting its widespread application. However, since the U.S. Food and Drug Administration (FDA) approved the first OV therapy drug, T-VEC, in 2015, interest in OV has grown significantly. In recent years, oncolytic virus therapy has shown increasingly promising application prospects and has become a major research focus in the field of cancer treatment. This article reviews the development, classification, and research progress of oncolytic viruses, as well as their mechanisms of action, therapeutic methods, and routes of administration.

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.

Coxsackievirus A11 is an immunostimulatory oncolytic virus that induces complete tumor regression in a human non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. Innovative treatment is required to improve overall survival rates for advanced NSCLC. Oncolytic virotherapy using enteroviruses has emerged as a promising anticancer strategy. To identify a novel, potent virotherapy with an improved safety profile, we assessed the oncolytic activity of 28 enteroviral strains and focused on coxsackievirus A11 (CVA11). CVA11 infection caused extensive oncolytic activity in all three of the examined human NSCLC cell lines, with high intercellular adhesion molecule-1 (ICAM-1) expression associated with greater CVA11-induced cytotoxicity. In vitro inhibition analysis using a pan-caspase inhibitor and western blot detection of cleaved poly (ADP-ribose) polymerase (PARP) indicated that apoptosis partly contributed to CVA11-driven cytotoxicity. CVA11 infection-induced immunogenic cell death in vitro was strongly suggested by substantial calreticulin expression and release of high mobility group box-1 protein (HMGB1). Moreover, in vivo treatment of human NSCLC xenografts with intratumoral CVA11 injection caused complete tumor regression in all treated mice, without significant weight loss. Our findings indicate that novel oncolytic virotherapy utilizing CVA11 may be less toxic and more effective than current treatments for human NSCLC, thus warranting further investigation in clinical trial settings, especially in combination with immunotherapy.

Polycytidine tract deletion from microRNA-detargeted oncolytic Mengovirus optimizes the therapeutic index in a murine multiple myeloma model

Mengovirus is an oncolytic picornavirus whose broad host range allows for testing in immunocompetent cancer models. Two pathogenicity-ablating approaches, polycytidine (polyC) tract truncation and microRNA (miRNA) targets insertion, eliminated the risk of encephalomyocarditis. To investigate whether a polyC truncated, miRNA-detargeted oncolytic Mengovirus might be boosted, we partially or fully rebuilt the polyC tract into the 5' noncoding region (NCR) of polyC-deleted (MC0) oncolytic constructs (NC) carrying miRNA target (miRT) insertions to eliminate cardiac/muscular (miR-133b and miR-208a) and neuronal (miR-124) tropisms. PolyC-reconstituted viruses (MC24-NC and MC37-NC) replicated in vitro and showed the expected tropism restrictions, but reduced cytotoxicity and miRT deletions were frequently observed. In the MPC-11 immune competent mouse plasmacytoma model, both intratumoral and systemic administration of MC0-NC led to faster tumor responses than MC24-NC or MC37-NC, with combined durable complete response rates of 75%, 0.5%, and 30%, respectively. Secondary viremia was higher following MC0-NC versus MC24-NC or MC37-NC therapy. Sequence analysis of virus progeny from treated mice revealed a high prevalence of miRT sequences loss among MC24- and MC37- viral genomes, but not in MC0-NC. Overall, MC0-NC was capable of stably retaining miRT sites and provided a more effective treatment and is therefore our lead Mengovirus candidate for clinical translation.

Viral Vectors in Gene Therapy: Where Do We Stand in 2023?

Viral vectors have been used for a broad spectrum of gene therapy for both acute and chronic diseases. In the context of cancer gene therapy, viral vectors expressing anti-tumor, toxic, suicide and immunostimulatory genes, such as cytokines and chemokines, have been applied. Oncolytic viruses, which specifically replicate in and kill tumor cells, have provided tumor eradication, and even cure of cancers in animal models. In a broader meaning, vaccine development against infectious diseases and various cancers has been considered as a type of gene therapy. Especially in the case of COVID-19 vaccines, adenovirus-based vaccines such as ChAdOx1 nCoV-19 and Ad26.COV2.S have demonstrated excellent safety and vaccine efficacy in clinical trials, leading to Emergency Use Authorization in many countries. Viral vectors have shown great promise in the treatment of chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, hemophilia, β-thalassemia, and sickle cell disease (SCD). Proof-of-concept has been established in preclinical studies in various animal models. Clinical gene therapy trials have confirmed good safety, tolerability, and therapeutic efficacy. Viral-based drugs have been approved for cancer, hematological, metabolic, neurological, and ophthalmological diseases as well as for vaccines. For example, the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, the oncolytic HSV T-VEC for melanoma, lentivirus-based treatment of ADA-SCID disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease have been approved for human use.

Advances in Intralesional Therapy for Locoregionally Advanced and Metastatic Melanoma: Five Years of Progress

Locoregionally advanced and metastatic melanoma are complex diagnoses with a variety of available treatment options. Intralesional therapy for melanoma has been under investigation for decades; however, it has advanced precipitously in recent years. In 2015, the Food and Drug Administration (FDA) approved talimogene laherparepvec (T-VEC), the only FDA-approved intralesional therapy for advanced melanoma. There has been significant progress since that time with other oncolytic viruses, toll-like receptor agonists, cytokines, xanthene dyes, and immune checkpoint inhibitors all under investigation as intralesional agents. Further to this, there has been exploration of numerous combinations of intralesional therapies and systemic therapies as various lines of therapy. Several of these combinations have been abandoned due to their lack of efficacy or safety concerns. This manuscript presents the various types of intralesional therapies that have reached phase 2 or later clinical trials in the past 5 years, including their mechanism of action, therapeutic combinations under investigation, and published results. The intention is to provide an overview of the progress that has been made, discuss ongoing trials worth following, and share our opinions on opportunities for further advancement.

Preexisting immunity: Barrier or bridge to effective oncolytic virus therapy?

Oncolytic viruses (OVs) represent a highly promising treatment strategy for a wide range of cancers, by mediating both the direct killing of tumor cells as well as mobilization of antitumor immune responses. As many OVs circulate in the human population, preexisting OV-specific immune responses are prevalent. Indeed, neutralizing antibodies (NAbs) are abundantly present in the human population for commonly used OVs, such as Adenovirus type 5 (Ad5), Herpes Simplex Virus-1 (HSV-1), Vaccinia virus, Measles virus, and Reovirus. This review discusses (pre)clinical evidence regarding the effect of preexisting immunity against OVs on two distinct aspects of OV therapy; OV infection and spread, as well as the immune response induced upon OV therapy. Combined, this review provides evidence that consideration of preexisting immunity is crucial in realizing the full potential of the highly promising therapeutic implementation of OVs. Future investigation of current gaps in knowledge highlighted in this review should yield a more complete understanding of this topic, ultimately allowing for better and more personalized OV therapies.

Gene Therapy Cargoes Based on Viral Vector Delivery

Viral vectors have been proven useful in a broad spectrum of gene therapy applications due to their possibility to accommodate foreign genetic material for both local and systemic delivery. The wide range of viral vectors has enabled gene therapy applications for both acute and chronic diseases. Cancer gene therapy has been addressed by the delivery of viral vectors expressing anti-tumor, toxic, and suicide genes for the destruction of tumors. Delivery of immunostimulatory genes such as cytokines and chemokines has also been applied for cancer therapy. Moreover, oncolytic viruses specifically replicating in and killing tumor cells have been used as such for tumor eradication or in combination with tumor killing or immunostimulatory genes. In a broad meaning, vaccines against infectious diseases and various cancers can be considered gene therapy, which has been highly successful, not the least for the development of effective COVID-19 vaccines. Viral vector-based gene therapy has also demonstrated encouraging and promising results for chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, and hemophilia. Preclinical gene therapy studies in animal models have demonstrated proof-of-concept for a wide range of disease indications. Clinical evaluation of drugs and vaccines in humans has showed high safety levels, good tolerance, and therapeutic efficacy. Several gene therapy drugs such as the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, lentivirus-based treatment of SCID-X1 disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease, and adenovirus-based vaccines against COVID-19 have been developed.

Analysis of ICAM-1 Expression on Bladder Carcinoma Cell Lines and Infectivity and Oncolysis by Coxsackie Virus A21

Oncolytic viruses are biological agents which can easily be delivered at high doses directly to the bladder through a catheter (intravesical), with low risk of systemic uptake and toxicity. To date, a number of viruses have been delivered intravesically in patients and in murine models with bladder cancer and antitumour effects demonstrated. Here, we describe in vitro methods to evaluate Coxsackie virus, CVA21, as an oncolytic virus for the treatment of human bladder cancer by determining the susceptibility of bladder cancer cell lines expressing differing levels of ICAM-1 surface receptor to CVA21.

Phase 1, open-label, dose-escalation study on the safety, pharmacokinetics, and preliminary efficacy of intravenous Coxsackievirus A21 (V937), with or without pembrolizumab, in patients with advanced solid tumors

BACKGROUND

Oncolytic virus V937 showed activity and safety with intratumoral administration. This phase 1 study evaluated intravenous V937±pembrolizumab in patients with advanced solid tumors.

METHODS

Patients had advanced non-small cell lung cancer (NSCLC), urothelial cancer, metastatic castration-resistant prostate cancer, or melanoma in part A (V937 monotherapy), and metastatic NSCLC or urothelial cancer in part B (V937+pembrolizumab). Prior immunotherapy was permitted >28 days before study treatment. Patients received intravenous V937 on days 1, 3, and 5 (also on day 8 in part B) of the first 21-day cycle and on day 1 of subsequent cycles for eight cycles. Three ascending dose-escalation cohorts were studied. Dose-escalation proceeded if no dose-limiting toxicities (DLTs) occurred in cycle 1 of the previous cohort. In part B, patients also received pembrolizumab 200 mg every 3 weeks from day 8 for 2 years; dose-expansion occurred at the highest-dose cohort. Serial biopsies were performed.

RESULTS

No DLTs occurred in parts A (n=18) or B (n=85). Grade 3-5 treatment-related adverse events (AEs) were not observed in part A and were experienced by 10 (12%) patients in part B. The most frequent treatment-related AEs (any grade) in part B were fatigue (36%), pruritus (18%), myalgia (14%), diarrhea (13%), pyrexia (13%), influenza-like illness (12%), and nausea (12%). At the highest tested dose, median intratumoral V937 concentrations were 117,631 copies/mL on day 8, cycle 1 in part A (n=6) and below the detection limit for most patients (86% (19/22)) on day 15, cycle 1 in part B. Objective response rates were 6% (part A), 9% in the NSCLC dose-expansion cohort (n=43), and 20% in the urothelial cancer dose-expansion cohort (n=35).

CONCLUSIONS

Intravenous V937+pembrolizumab had a manageable safety profile. Although V937 was detected in tumor tissue, in NSCLC and urothelial cancer, efficacy was not greater than that observed in previous studies with pembrolizumab monotherapy.

TRIAL REGISTRATION NUMBER

NCT02043665.

Oncolytic Viruses for the Treatment of Bladder Cancer: Advances, Challenges, and Prospects

Bladder cancer is one of the most prevalent cancers. Despite recent advancements in bladder cancer therapy, new strategies are still required for improving patient outcomes, particularly for those who experienced Bacille Calmette-Guerin failure and those with locally advanced or metastatic bladder cancer. Oncolytic viruses are either naturally occurring or purposefully engineered viruses that have the ability to selectively infect and lyse tumor cells while avoiding harming healthy cells. In light of this, oncolytic viruses serve as a novel and promising immunotherapeutic strategy for bladder cancer. A wide diversity of viruses, including adenoviruses, herpes simplex virus, coxsackievirus, Newcastle disease virus, vesicular stomatitis virus, alphavirus, and vaccinia virus, have been studied in many preclinical and clinical studies for their potential as oncolytic agents for bladder cancer. This review aims to provide an overview of the advances in oncolytic viruses for the treatment of bladder cancer and highlights the challenges and research directions for the future.

High-resolution structural analysis of enterovirus-reactive polyclonal antibodies in complex with whole virions

Non-polio enteroviruses (NPEVs) cause serious illnesses in young children and neonates, including aseptic meningitis, encephalitis, and inflammatory muscle disease, among others. While over 100 serotypes have been described to date, vaccine only exists for EV-A71. Efforts toward rationally designed pan-NPEV vaccines would greatly benefit from structural biology methods for rapid and comprehensive evaluation of vaccine candidates and elicited antibody responses. Toward this goal, we introduced a cryo-electron-microscopy-based approach for structural analysis of virus- or vaccine-elicited polyclonal antibodies (pAbs) in complex with whole NPEV virions. We demonstrated the feasibility using coxsackievirus A21 and reconstructed five structurally distinct pAbs bound to the virus. The pAbs targeted two immunodominant epitopes, one overlapping with the receptor binding site. These results demonstrate that our method can be applied to map broad-spectrum polyclonal immune responses against intact virions and define potentially cross-reactive epitopes.

Construction of a Vero Cell Line Expressing Human ICAM1 for the Development of Rhinovirus Vaccines

Human rhinoviruses (HRVs) are small non-enveloped RNA viruses that belong to the Enterovirus genus within the Picornaviridae family and are known for causing the common cold. Though symptoms are generally mild in healthy individuals, the economic burden associated with HRV infection is significant. A vaccine could prevent disease. The Vero-cell-based viral vaccine platform technology was considered for such vaccine development. Unfortunately, most HRV strains are unable to propagate on Vero cells due to a lack of the major receptor of HRV group A and B, intercellular adhesion molecule (ICAM1, also known as CD54). Therefore, stable human ICAM1 expressing Vero cell clones were generated by transfecting the ICAM1 gene in Vero cells and selecting clones that overexpressed ICAM1 on the cell surface. Cell banks were made and expression of ICAM1 was stable for at least 30 passages. The Vero_ICAM1 cells and parental Vero cells were infected with four HRV prototypes, B14, A16, B37 and A57. Replication of all four viruses was detected in Vero_ICAM1, but not in the parental Vero cells. Altogether, Vero cells expressing ICAM1 could efficiently propagate the tested HRV strains. Therefore, ICAM1-expressing cells could be a useful tool for the development and future production of polyvalent HRV vaccines or other viruses that use ICAM1 as a receptor.

Reverse-Phase Ultra-Performance Chromatography Method for Oncolytic Coxsackievirus Viral Protein Separation and Empty to Full Capsid Quantification

Oncolytic virus immunotherapy is emerging as a novel therapeutic approach for cancer treatment. Immunotherapy clinical drug candidate V937 is currently in phase I/II clinical trials and consists of a proprietary formulation of Coxsackievirus A21 (CVA21), which specifically infects and lyses cells with overexpressed ICAM-1 receptors in a range of tumors. Mature Coxsackievirus virions, consisting of four structural virion proteins, (VPs) VP1, VP2, VP3, and VP4, and the RNA genome, are the only viral particles capable of being infectious. In addition to mature virions, empty procapsids with VPs, VP0, VP1, and VP3, and other virus particles are produced in V937 production cell culture. Viral protein VP0 is cleaved into VP2 and VP4 after RNA genome encapsidation to form mature virions. Clearance of viral particles containing VP0, and quantification of viral protein distribution are important in V937 downstream processing. Existing analytical methods for the characterization of viral proteins and particles may lack sensitivity or are low throughput. We developed a sensitive and robust reverse-phase ultra-performance chromatography method to separate, identify, and quantify all five CVA21 VPs. Quantification of virus capsid concentration and empty/full capsid ratio was achieved with good linearity, accuracy, and precision. ClinicalTrials.gov ID: NCT04521621 and NCT04152863.

Application of cation exchange chromatography in bind and elute and flowthrough mode for the purification of enteroviruses

Members of the enterovirus genus are promising oncolytic agents. Their morphogenesis involves the generation of both genome-packed infectious capsids and empty capsids. The latter are typically considered as an impurity in need of removal from the final product. The separation of empty and full capsids can take place with centrifugation methods, which are of low throughput and poorly scalable, or scalable chromatographic processes, which typically require peak cutting and a significant trade-off between purity and yield. Here we demonstrate the application of packed bed cation exchange (CEX) column chromatography for the separation of empty capsids from infectious virions for a prototype strain of Coxsackievirus A21. This separation was developed using high throughput chromatography techniques and scaled up as a bind and elute polishing step. The separation was robust over a wide range of operating conditions and returned highly resolved empty and full capsids. The CEX step could be operated in bind and elute or flowthrough mode with similar selectivity and returned yields greater than 70% for full mature virus particles. Similar performance was also achieved using a selection of other bead based CEX chromatography media, demonstrating general applicability of this type of chromatography for Coxsackievirus A21 purification. These results highlight the wide applicability and excellent performance of CEX chromatography for the purification of enteroviruses, such as Coxsackievirus A21.

Double Trouble: Immunotherapy Doublets in Melanoma-Approved and Novel Combinations to Optimize Treatment in Advanced Melanoma

Immune checkpoint inhibitors, particularly anti-PD-1-based immune checkpoint inhibitors, have dramatically improved outcomes for patients with advanced melanoma and are currently deemed a standard of care. Ipilimumab/nivolumab is the first combination of immune checkpoint inhibitors to improve progression-free survival and overall survival in the first-line setting, with durable responses and the longest median overall survival, 72.1 months, of any drug therapy approved for advanced melanoma. However, its use is limited by the high rate of severe (grade 3-4) treatment-related adverse events. More recently, the novel immune checkpoint inhibitor combination of nivolumab/relatlimab (anti-PD-1/anti-LAG3) showed improved progression-free survival compared with nivolumab alone in the first-line setting and was well tolerated; thus, it is likely this combination will be added to the armamentarium as a first-line treatment for advanced melanoma. These changes in the treatment landscape have several treatment implications for decision-making. The choice of first-line systemic drug therapy, and the decision between immune checkpoint inhibitor monotherapy or combination therapy, requires a comprehensive assessment of disease-related factors and patient characteristics. Despite this striking progress, many patients' disease still progresses. Several new agents and therapeutic approaches are under investigation in clinical trials. Intralesional treatments hold promise for accessible metastases, although their broad application in the clinic will be limited. Prognostic and predictive biomarkers, as well as strategies to reduce treatment-related toxicities and overcome resistance, are required and are now the focus of clinical and translational research.

SEC coupled with in-line multiple detectors for the characterization of an oncolytic Coxsackievirus

V937 is an oncolytic virus immunotherapy clinical drug candidate consisting of a proprietary formulation of Coxsackievirus A21 (CVA21). V937 specifically binds to and lyses cells with over-expressed ICAM-1 receptors in a range of tumor cell types and is currently in phase I and II clinical trials. Infectious V937 particles consist of a ∼30 nm icosahedral capsid assembled from four structural viral proteins that encapsidate a viral RNA genome. Rapid and robust analytical methods to quantify and characterize CVA21 virus particles are important to support the process development, regulatory requirements, and validation of new manufacturing platforms. Herein, we describe a size-exclusion chromatography (SEC) method that was developed to characterize the V937 drug substance and process intermediates. Using a 4-in-1 combination of multi-detectors (UV, refractive index, dynamic and static light scattering), we demonstrate the use of SEC for the quantification of the virus particle count, the determination of virus size (molecular weight and hydrodynamic diameter), and the characterization of virus purity by assessing empty-to-full capsid ratios. Through a SEC analysis of stressed V937 samples, we propose CVA21 thermal degradation pathways that result in genome release and particle aggregation.

The treatment of advanced melanoma: a review of systemic and local therapies in combination with immune checkpoint inhibitors in phase 1 and 2 clinical trials

INTRODUCTION

While the incidence of melanoma continues to rise, the mortality of the disease appears to have stabilized. This may, in part, be due to the development and application of immune checkpoint inhibitors as standard of care in advanced melanoma. However, many patients do not respond to these therapies alone. Combining immune checkpoint inhibitors with other classes of therapeutics appears to be a promising direction to improve response and survival in advanced melanoma.

AREAS COVERED

This review article aims to discuss phase 1 and 2 clinical trials examining immune checkpoint inhibitors in combination therapy for the treatment of advanced, unresectable melanoma. In particular, these regimens include various kinase inhibitors, tumor-infiltrating lymphocytes, toll-like receptor agonists, cytokines, and oncolytic viral therapies. The combinations under discussion include both systemic and combination systemic/local therapies.

EXPERT OPINION

Drug combinations discussed here appear to be promising therapeutic regimens for advanced melanoma. Improved understanding of the mechanisms of primary, adaptive, and acquired resistance to immune checkpoint inhibitors may guide the development of future combination regimens.

Oncolytic virotherapy as promising immunotherapy against cancer: mechanisms of resistance to oncolytic viruses

Oncolytic virotherapy has currently emerged as a powerful therapeutic approach in cancer treatment. Although the history of using viruses goes back to the early 20th century, the approval of talimogene laherparepvec (T-VEC) in 2015 increased interest in oncolytic viruses (OVs). OVs are multifaceted biotherapeutic agents because they replicate in and kill tumor cells and augment immune responses by releasing immunostimulatory molecules from lysed cells. Despite promising results, some limitations hinder the efficacy of oncolytic virotherapy. The delivery challenges and the upregulation of checkpoints following oncolytic virotherapy also mediate resistance to OVs by diminishing immune responses. Furthermore, the localization of receptors of viruses in the tight junctions, interferon responses, and the aberrant expression of genes involved in the cell cycle of the virus, including their infection and replication, reduce the efficacy of OVs. In this review, we present different mechanisms of resistance to OVs and strategies to overcome them.

Advances in viral oncolytics for treatment of multiple myeloma - a focused review

INTRODUCTION

Oncolytic viruses are genetically engineered viruses that target myeloma-affected cells by detecting specific cell surface receptors (CD46, CD138), causing cell death by activating the signaling pathway to induce apoptosis or by immune-mediated cellular destruction.

AREAS COVERED

This article summarizes oncolytic virotherapy advancements such as the therapeutic use of viruses by targeting cell surface proteins of myeloma cells as well as the carriers to deliver viruses to the target tissues safely. The major classes of viruses that have been studied for this include measles, myxoma, adenovirus, reovirus, vaccinia, vesicular-stomatitis virus, coxsackie, and others. The measles virus acts as oncolytic viral therapy by binding to the CD46 receptors on the myeloma cells to utilize its surface H protein. These H-protein and CD46 interactions lead to cellular syncytia formation resulting in cellular apoptosis. Vesicular-stomatitis virus acts by downregulation of anti-apoptotic factors (Mcl-2, BCL-2). Based upon the published literature searches till December 2020, we have summarized the data supporting the advances in viral oncolytic for the treatment of MM.

EXPERT OPINION

Oncolytic virotherapy is an experimental approach in multiple myeloma (MM); many issues need to be addressed for safe viral delivery to the target tissue.

Prior Exposure to Coxsackievirus A21 Does Not Mitigate Oncolytic Therapeutic Efficacy

Oncolytic viruses (OVs) are being developed as a type of immunotherapy and have demonstrated durable tumor responses and clinical efficacy. One such OV, Coxsackievirus A21 (CVA21), exhibited therapeutic efficacy in early phase clinical trials, demonstrating the ability to infect and kill cancer cells and stimulate anti-tumor immune responses. However, one of the major concerns in using this common cold virus as a therapeutic is the potential for innate and adaptive immune responses to mitigate the benefits of viral infection, particularly in individuals that have been exposed to coxsackievirus prior to treatment. In this study, we assess melanoma responses to CVA21 in the absence or presence of prior exposure to the virus. Melanomas were transplanted into naïve or CVA21-immunized C57BL6 mice and the mice were treated with intratumoral (IT) CVA21. We find that prior exposure to CVA21 does not dramatically affect tumor responses, nor does it alter overall survival. Our results suggest that prior exposure to coxsackievirus is not a critical determinant of patient selection for IT CVA21 interventions.

Clinical Responses of Oncolytic Coxsackievirus A21 (V937) in Patients With Unresectable Melanoma

PURPOSE

We evaluated the activity of intratumoral Coxsackievirus A21 (V937) in 57 patients with unresectable stage IIIC or IV melanoma.

PATIENTS AND METHODS

In this multicenter, open-label, phase II study, patients received up to a total V937 dose of 3 × 10⁸ TCID₅₀ (50% tissue culture infectious dose) in a maximum 4.0-mL volume by intratumoral injection. Ten sets of V937 injections were administered between days 1 and 127 (NCT01227551). Patients who had stable disease or were responding could continue treatment in an extension study (NCT01636882). Response and progression status were based on contrast-enhanced computed tomography, magnetic resonance imaging, or caliper measurement and were categorized using immune-related Response Evaluation Criteria in Solid Tumors (irRECIST). Other evaluations included monitoring of adverse events and serum levels of V937 and anti-V937 antibody titers. The primary efficacy end point was 6-month progression-free survival (PFS) rate per irRECIST.

RESULTS

The primary efficacy end point, 6-month PFS rate per irRECIST, was 38.6% (95% CI, 26.0 to 52.4). Durable response rate (partial or complete response for ≥ 6 months) was 21.1% per irRECIST. Best overall response rate (complete plus partial response) was 38.6% (unconfirmed) and 28.1% (confirmed) per irRECIST. Regression of melanoma was observed in noninjected lesions. Based on Kaplan-Meier estimation, 12-month PFS was 32.9% (95% CI, 19.5 to 46.9) per irRECIST and 12-month overall survival was 75.4% (95% CI, 62.1 to 84.7). No treatment-related grade ≥ 3 adverse events occurred. Viral RNA was detected in serum within 30 minutes of administration. Neutralizing antibody titers increased to > 1:16 in all patients after day 22, without effect on clinical or immunologic response.

CONCLUSION

V937 was well tolerated and warrants further investigation for treatment of patients with unresectable melanoma. Studies of combination approaches with V937 and immune checkpoint inhibitors are ongoing.

A review on the advances and challenges of immunotherapy for head and neck cancer

Head and neck cancer (HNC), which includes lip and oral cavity, larynx, nasopharynx, oropharynx, and hypopharynx malignancies, is one of the most common cancers worldwide. Due to the interaction of tumor cells with immune cells in the tumor microenvironment, immunotherapy of HNCs, along with traditional treatments such as chemotherapy, radiotherapy, and surgery, has attracted much attention. Four main immunotherapy strategies in HNCs have been developed, including oncolytic viruses, monoclonal antibodies, chimeric antigen receptor T cells (CAR-T cells), and therapeutic vaccines. Oncorine (H101), an approved oncolytic adenovirus in China, is the pioneer of immunotherapy for the treatment of HNCs. Pembrolizumab and nivolumab are mAbs against PD-L1 that have been approved for recurrent and metastatic HNC patients. To date, several clinical trials using immunotherapy agents and their combination are under investigation. In this review, we summarize current the interaction of tumor cells with immune cells in the tumor microenvironment of HNCs, the main strategies that have been applied for immunotherapy of HNCs, obstacles that hinder the success of immunotherapies in patients with HNCs, as well as solutions for overcoming the challenges to enhance the response of HNCs to immunotherapies.

Combinatorial Approaches for Cancer Treatment Using Oncolytic Viruses: Projecting the Perspectives through Clinical Trials Outcomes

Recent cancer immunotherapy breakthroughs have fundamentally changed oncology and revived the fading hope for a cancer cure. The immune checkpoint inhibitors (ICI) became an indispensable tool for the treatment of many malignant tumors. Alongside ICI, the application of oncolytic viruses in clinical trials is demonstrating encouraging outcomes. Dozens of combinations of oncolytic viruses with conventional radiotherapy and chemotherapy are widely used or studied, but it seems quite complicated to highlight the most effective combinations. Our review summarizes the results of clinical trials evaluating oncolytic viruses with or without genetic alterations in combination with immune checkpoint blockade, cytokines, antigens and other oncolytic viruses as well. This review is focused on the efficacy and safety of virotherapy and the most promising combinations based on the published clinical data, rather than presenting all oncolytic virus variations, which are discussed in comprehensive literature reviews. We briefly revise the research landscape of oncolytic viruses and discuss future perspectives in virus immunotherapy, in order to provide an insight for novel strategies of cancer treatment.

Development of Group B Coxsackievirus as an Oncolytic Virus: Opportunities and Challenges

Oncolytic viruses have emerged as a promising strategy for cancer therapy due to their dual ability to selectively infect and lyse tumor cells and to induce systemic anti-tumor immunity. Among various candidate viruses, coxsackievirus group B (CVBs) have attracted increasing attention in recent years. CVBs are a group of small, non-enveloped, single-stranded, positive-sense RNA viruses, belonging to species human Enterovirus B in the genus Enterovirus of the family Picornaviridae. Preclinical studies have demonstrated potent anti-tumor activities for CVBs, particularly type 3, against multiple cancer types, including lung, breast, and colorectal cancer. Various approaches have been proposed or applied to enhance the safety and specificity of CVBs towards tumor cells and to further increase their anti-tumor efficacy. This review summarizes current knowledge and strategies for developing CVBs as oncolytic viruses for cancer virotherapy. The challenges arising from these studies and future prospects are also discussed in this review.

Current status of intralesional agents in treatment of malignant melanoma

Prognosis of metastatic melanoma has undergone substantial improvement with the discovery of checkpoint inhibitors. Immunotherapies and targeted therapies have improved the median overall survival (OS) of metastatic melanoma from 6 months to more than 3 years. However, still about half of the patients die due to uncontrolled disease. Therefore, multiple strategies are currently being investigated to improve outcomes. One such strategy is intralesional/intratumoral (IT) therapies which can either directly kill the tumor cells or make the tumor more immunogenic to be recognized by the immune system. Talimogene laherparepvec (T-VEC), an oncolytic virus, is the first FDA approved IT therapy. This review focuses on the current status of IT agents currently under clinical trials in melanoma. Reviewed therapies include T-VEC, T-VEC with immune checkpoint inhibitors including ipilimumab and pembrolizumab or other agents, RP1, OrienX010, Canerpaturev (C-REV, HF10), CAVATAK (coxsackievirus A21, CVA21) alone or in combination with checkpoint inhibitors, oncolytic polio/rhinovirus recombinant (PVSRIPO), MAGE-A3-expressing MG1 Maraba virus, VSV-IFNbetaTYRP1, suicide gene therapy, ONCOS-102, OBP-301 (Telomelysin), Stimulation of Interferon Genes Pathway (STING agonists) including DMXAA, MIW815 (ADU-S100) and MK-1454, PV-10, toll-like receptors (TLRs) agonists including TLR-9 agonists (SD-101, CMP-001, IMO-2125 or tilsotolimod, AST-008 or cavrotolimod, MGN1703 or lefitolimod), CV8102, NKTR-262 plus NKTR-214, LHC165, G100, intralesional interleukin-2, Daromun (L19IL2 plus L19TNF), Hiltonol (poly-ICLC), electroporation including calcium electroporation and plasmid interleukin-12 electroporation (pIL-12 EP), IT ipilimumab, INT230-6 (cisplatin and vinblastine with an amphiphilic penetration enhancer), TTI-621 (SIRPαFc), CD-40 agonistic antibodies (ABBV-927 and APX005M), antimicrobial peptide LL37 and other miscellaneous agents.

Coxsackievirus B3-Its Potential as an Oncolytic Virus

Oncolytic virotherapy represents one of the most advanced strategies to treat otherwise untreatable types of cancer. Despite encouraging developments in recent years, the limited fraction of patients responding to therapy has demonstrated the need to search for new suitable viruses. Coxsackievirus B3 (CVB3) is a promising novel candidate with particularly valuable features. Its entry receptor, the coxsackievirus and adenovirus receptor (CAR), and heparan sulfate, which is used for cellular entry by some CVB3 variants, are highly expressed on various cancer types. Consequently, CVB3 has broad anti-tumor activity, as shown in various xenograft and syngeneic mouse tumor models. In addition to direct tumor cell killing the virus induces a strong immune response against the tumor, which contributes to a substantial increase in the efficiency of the treatment. The toxicity of oncolytic CVB3 in healthy tissues is variable and depends on the virus strain. It can be abrogated by genetic engineering the virus with target sites of microRNAs. In this review, we present an overview of the current status of the development of CVB3 as an oncolytic virus and outline which steps still need to be accomplished to develop CVB3 as a therapeutic agent for clinical use in cancer treatment.

Oncolytic viruses encoding bispecific T cell engagers: a blueprint for emerging immunovirotherapies

Bispecific T cell engagers (BiTEs) are an innovative class of immunotherapeutics that redirect T cells to tumor surface antigens. While efficacious against certain hematological malignancies, limited bioavailability and severe toxicities have so far hampered broader clinical application, especially against solid tumors. Another emerging cancer immunotherapy are oncolytic viruses (OVs) which selectively infect and replicate in malignant cells, thereby mediating tumor vaccination effects. These oncotropic viruses can serve as vectors for tumor-targeted immunomodulation and synergize with other immunotherapies. In this article, we discuss the use of OVs to overcome challenges in BiTE therapy. We review the current state of the field, covering published preclinical studies as well as ongoing clinical investigations. We systematically introduce OV-BiTE vector design and characteristics as well as evidence for immune-stimulating and anti-tumor effects. Moreover, we address additional combination regimens, including CAR T cells and immune checkpoint inhibitors, and further strategies to modulate the tumor microenvironment using OV-BiTEs. The inherent complexity of these novel therapeutics highlights the importance of translational research including correlative studies in early-phase clinical trials. More broadly, OV-BiTEs can serve as a blueprint for diverse OV-based cancer immunotherapies.

Oncolytic Virotherapy and Microenvironment in Multiple Myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by the accumulation of bone marrow (BM) clonal plasma cells, which are strictly dependent on the microenvironment. Despite the improvement of MM survival with the use of new drugs, MM patients still relapse and become always refractory to the treatment. The development of new therapeutic strategies targeting both tumor and microenvironment cells are necessary. Oncolytic virotherapy represent a promising approach in cancer treatment due to tumor-specific oncolysis and activation of the immune system. Different types of human viruses were checked in preclinical MM models, and the use of several viruses are currently investigated in clinical trials in MM patients. More recently, the use of alternative non-human viruses has been also highlighted in preclinical studies. This strategy could avoid the antiviral immune response of the patients against human viruses due to vaccination or natural infections, which could invalid the efficiency of virotherapy approach. In this review, we explored the effects of the main oncolytic viruses, which act through both direct and indirect mechanisms targeting myeloma and microenvironment cells inducing an anti-MM response. The efficacy of the oncolytic virus-therapy in combination with other anti-MM drugs targeting the microenvironment has been also discussed.

Current Trends in Cancer Immunotherapy

The search for an effective drug to treat oncological diseases, which have become the main scourge of mankind, has generated a lot of methods for studying this affliction. It has also become a serious challenge for scientists and clinicians who have needed to invent new ways of overcoming the problems encountered during treatments, and have also made important discoveries pertaining to fundamental issues relating to the emergence and development of malignant neoplasms. Understanding the basics of the human immune system interactions with tumor cells has enabled new cancer immunotherapy strategies. The initial successes observed in immunotherapy led to new methods of treating cancer and attracted the attention of the scientific and clinical communities due to the prospects of these methods. Nevertheless, there are still many problems that prevent immunotherapy from calling itself an effective drug in the fight against malignant neoplasms. This review examines the current state of affairs for each immunotherapy method, the effectiveness of the strategies under study, as well as possible ways to overcome the problems that have arisen and increase their therapeutic potentials.