Going viral: a review of replication-selective oncolytic adenoviruses. Oncotarget. 2015;6:19976-19989. [PMID: 26280277 PMCID: PMC4652981 DOI: 10.18632/oncotarget.5116]

TGF-β trap of AdAPT-001 turns up the heat on tumors and turns down checkpoint blocker resistance

At the ASCO 2024 meeting, Anthony P Conley, coauthor on this editorial, presented promising data from the phase 1/2 clinical trial called BETA PRIME (ClinicalTrials.gov NCT04673942) with AdAPT-001 plus a checkpoint inhibitor (CI). All participants gave informed consent to participate in BETA PRIME before taking part. AdAPT-001 is an oncolytic adenovirus that expresses a transforming growth factor beta (TGF-β) trap to neutralize active TGF-β. This editorial proposes that the TGF-β trap of AdAPT-001 reverses the immunosuppressive environment of tumor cells, and thus makes these tumors susceptible to CIs like the anti-PD-1 agent, nivolumab, and potentially other therapies as well.

Optimizing Pancreatic Cancer Therapy: The Promise of Immune Stimulatory Oncolytic Viruses

Pancreatic cancer presents formidable challenges due to rapid progression and resistance to conventional treatments. Oncolytic viruses (OVs) selectively infect cancer cells and cause cancer cells to lyse, releasing molecules that can be identified by the host's immune system. Moreover, OV can carry immune-stimulatory payloads such as interleukin-12, which when delivered locally can enhance immune system-mediated tumor killing. OVs are very well tolerated by cancer patients due to their ability to selectively target tumors without affecting surrounding normal tissues. OVs have recently been combined with other therapies, including chemotherapy and immunotherapy, to improve clinical outcomes. Several OVs including adenovirus, herpes simplex viruses (HSVs), vaccinia virus, parvovirus, reovirus, and measles virus have been evaluated in preclinical and clinical settings for the treatment of pancreatic cancer. We evaluated the safety and tolerability of a replication-competent oncolytic adenoviral vector carrying two suicide genes (thymidine kinase, TK; and cytosine deaminase, CD) and human interleukin-12 (hIL12) in metastatic pancreatic cancer patients in a phase 1 trial. This vector was found to be safe and well-tolerated at the highest doses tested without causing any significant adverse events (SAEs). Moreover, long-term follow-up studies indicated an increase in the overall survival (OS) in subjects receiving the highest dose of the OV. Our encouraging long-term survival data provide hope for patients with advanced pancreatic cancer, a disease that has not seen a meaningful increase in OS in the last five decades. In this review article, we highlight several preclinical and clinical studies and discuss future directions for optimizing OV therapy in pancreatic cancer. We envision OV-based gene therapy to be a game changer in the near future with the advent of newer generation OVs that have higher specificity and selectivity combined with personalized treatment plans developed under AI guidance.

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.

Enhancing cancer therapy: the integration of oncolytic virus therapy with diverse treatments

As one of the significant challenges to human health, cancer has long been a focal point in medical treatment. With ongoing advancements in the field of medicine, numerous methodologies for cancer therapy have emerged, among which oncolytic virus therapy has gained considerable attention. However, oncolytic viruses still exhibit limitations. Combining them with various therapies can further enhance the efficacy of cancer treatment, offering renewed hope for patients. In recent research, scientists have recognized the promising prospect of amalgamating oncolytic virus therapy with diverse treatments, potentially surmounting the restrictions of singular approaches. The central concept of this combined therapy revolves around leveraging oncolytic virus to incite localized tumor inflammation, augmenting the immune response for immunotherapeutic efficacy. Through this approach, the patient's immune system can better recognize and eliminate cancer cells, simultaneously reducing tumor evasion mechanisms against the immune system. This review delves deeply into the latest research progress concerning the integration of oncolytic virus with diverse treatments and its role in various types of cancer therapy. We aim to analyze the mechanisms, advantages, potential challenges, and future research directions of this combination therapy. By extensively exploring this field, we aim to instill renewed hope in the fight against cancer.

Hypothesis: AdAPT-001 and pseudoprogression - when seeing is not necessarily believing

The purpose of this commentary is to highlight the high occurrence of clinical pseudoprogression and delayed responses that have been observed to date with the locally injected oncolytic adenovirus, AdAPT-001, currently in a Phase 1/2 clinical trial (NCT04673942) for the treatment of treatment-refractory tumors. Not surprisingly, these have led to confusion about response assessment and whether to continue patients on treatment. AdAPT-001 carries a transforming growth factor (TGF)-beta trap (TGF-β), which sequesters TGF-β, a cytokine that potently regulates inflammation, fibrosis, and immunosuppression in cancer. Pseudoprogression (PsP) or progression prior to response or stabilization, has been widely recognized with radiotherapy for primary brain tumors and immune checkpoint inhibitors (ICIs). PsP has also been described and documented in the context of oncolytic virotherapy but perhaps to a lesser extent. However, repeated intratumoral injections with these immunostimulatory agents may induce a more intense immune response and release more antigenic epitopes than with ICIs, for example, which are strictly T-cell directed rather than also tumor-directed like AdAPT-001.

A viral attack on brain tumors: the potential of oncolytic virus therapy

Managing malignant brain tumors remains a significant therapeutic hurdle that necessitates further research to comprehend their treatment potential fully. Oncolytic viruses (OVs) offer many opportunities for predicting and combating tumors through several mechanisms, with both preclinical and clinical studies demonstrating potential. OV therapy has emerged as a potent and effective method with a dual mechanism. Developing innovative and effective strategies for virus transduction, coupled with immune checkpoint inhibitors or chemotherapy drugs, strengthens this new technique. Furthermore, the discovery and creation of new OVs that can seamlessly integrate gene therapy strategies, such as cytotoxic, anti-angiogenic, and immunostimulatory, are promising advancements. This review presents an overview of the latest advancements in OVs transduction for brain cancer, focusing on the safety and effectiveness of G207, G47Δ, M032, rQNestin34.5v.2, C134, DNX-2401, Ad-TD-nsIL12, NSC-CRAd-S-p7, TG6002, and PVSRIPO. These are evaluated in both preclinical and clinical models of various brain tumors.

Oncolytic Adenovirus for the Targeting of Paclitaxel-Resistant Breast Cancer Stem Cells

Adjuvant systemic therapies effectively reduce the risk of breast cancer recurrence and metastasis, but therapy resistance can develop in some patients due to breast cancer stem cells (BCSCs). Oncolytic adenovirus (OAd) represents a promising therapeutic approach as it can specifically target cancer cells. However, its potential to target BCSCs remains unclear. Here, we evaluated a Cox-2 promoter-controlled, Ad5/3 fiber-modified OAd designed to encode the human sodium iodide symporter (hNIS) in breast cancer models. To confirm the potential of OAds to target BCSCs, we employed BCSC-enriched estrogen receptor-positive (ER+) paclitaxel-resistant (TaxR) cells and tumorsphere assays. OAd-hNIS demonstrated significantly enhanced binding and superior oncolysis in breast cancer cells, including ER+ cells, while exhibiting no activity in normal mammary epithelial cells. We observed improved NIS expression as the result of adenovirus death protein deletion. OAd-hNIS demonstrated efficacy in targeting TaxR BCSCs, exhibiting superior killing and hNIS expression compared to the parental cells. Our vector was capable of inhibiting tumorsphere formation upon early infection and reversing paclitaxel resistance in TaxR cells. Importantly, OAd-hNIS also destroyed already formed tumorspheres seven days after their initiation. Overall, our findings highlight the promise of OAd-hNIS as a potential tool for studying and targeting ER+ breast cancer recurrence and metastasis.

BETA prime: a first-in-man phase 1 study of AdAPT-001, an armed oncolytic adenovirus for solid tumors

AdAPT-001 is an oncolytic adenovirus (OAV) with a transforming growth factor beta (TGF-ß) trap, which neutralizes the immunosuppressive and profibrotic cytokine, TGF-ß. The aim or purpose of this phase 1 study was to assess the safety and tolerability and, secondarily, the efficacy of AdAPT-001 after single intratumoral injection (IT) (Part 1) and multidose IT injection (Part 2) in patients with superficially accessible, advanced refractory solid tumors. Part 1 enrolled 9 patients with a 3 + 3 single dose-escalation safety run-in involving 2.5 × 1011, 5.0 × 1011, 1.0 × 1012 viral particles (vps). No dose-limiting toxicities or treatment-related serious adverse events (SAEs) were seen. In Part 2, a dose-expansion phase, 19 patients received AdAPT-001 at 1.0 × 1012 vps until disease progression according to Response Evaluation Criteria in Solid Tumors or RECIST 1.1. The overall responses to treatment included confirmed partial responses (3), durable stable disease ≥ 6 months (5), and progressive disease (13). AdAPT-001 is well tolerated. Evidence of an anti-tumor effect was seen in both injected and uninjected lesions. The recommended Phase 2 dose was 1.0 × 1012 vp administered by intratumoral injection once every 2 weeks. Combination of AdAPT-001 with a checkpoint inhibition is enrolling.

TheraVision: Engineering platform technology for the development of oncolytic viruses based on herpes simplex virus type 1

Viruses are able to efficiently penetrate cells, multiply, and eventually kill infected cells, release tumor antigens, and activate the immune system. Therefore, viruses are highly attractive novel agents for cancer therapy. Clinical trials with first generations of oncolytic viruses (OVs) are very promising but show significant need for optimization. The aim of TheraVision was to establish a broadly applicable engineering platform technology for combinatorial oncolytic virus and immunotherapy. Through genetic engineering, an attenuated herpes simplex virus type 1 (HSV1) was generated that showed increased safety compared to the wild-type strain. To demonstrate the modularity and the facilitated generation of new OVs, two transgenes encoding retargeting as well as immunomodulating single-chain variable fragments (scFvs) were integrated into the platform vector. The resulting virus selectively infected epidermal growth factor receptor (EGFR)-expressing cells and produced a functional immune checkpoint inhibitor against programmed cell death protein 1 (PD-1). Thus, both viral-mediated oncolysis and immune-cell-mediated therapy were combined into a single viral vector. Safety and functionality of the armed OVs have been shown in novel preclinical models ranging from patient-derived organoids and tissue-engineered human in vitro 3D tumor models to complex humanized mouse models. Consequently, a novel and proprietary engineering platform vector based on HSV1 is available for the facilitated preclinical development of oncolytic virotherapy.

Vector-Mediated Cancer Gene Therapy Reduces Toxicity and Inhibition of Lung Carcinoma Growth in Nude Mice

Replication-competent oncolytic adenovirus (TOA2) gene therapy is a recently introduced anti-tumor treatment regimen with superior results. The biodistribution studies of virus vector-based medicine seem more cautious and have been given much attention recently in terms of its quality and safety in preclinical trials. The current study determined the biodistribution and safety of a replication-competent adenovirus in different organs to predict its toxicity threshold. The present study has used TOA2, while biodistribution analysis was performed in human lung carcinoma A549-induced tumor-bearing nude mice model. Intratumoral injection was applied onto tumor-bearing mice with the adenovirus (3×1010 VP per mouse). Mice were sacrificed at the end of the experiment and the organs were dissected. Biodistribution analysis was done with complete hexon gene detection in each organ using quantitative real-time polymerase chain reaction (qRT-PCR). The biodistribution and concentration profiles showed that the TOA2 is well distributed in the entire tumor tissue. After dose 3 at day 11, the concentration of the virus has increased in the tumor tissue from 2240.54 (± 01.69) copies/100 ng genome to 13,120.28 (± 88.21) copies/100 ng genome on the 18th day, which eventually approached 336.45 (± 23.41) copies/100ng genome on the day 36. On the contrary, the concentration of the same decreased in the order of the liver, kidney, spleen, lung, and heart over time but no distributional traces in gonads. But the concentration found decreased dramatically in blood and other organs, while at the end of the experiment no detectable distribution was seen besides tumor tissue. The study confirms that adenovirus-based tumor therapy using conditionally replicating competent oncolytic TOA2 exhibited great efficiency with no toxicity at all.

Commentary on oncolytic viruses: past, present, and future

Whither oncolytic viruses? From the peak of their popularity in the early 2000s, when the ONYX-015 adenovirus had just entered the clinic, and then again in 2015 when the Food and Drug Administration-approved talimogene laherparepvec (also known as OncoVEXGM-CSF), which briefly revived interest, oncolytic viruses (OVs) have mostly fallen out of favor despite the many pharmaceutical companies with OVs in development.This commentary enumerates and addresses the core conceptions, perceptions, and misconceptions that characterize the current 'trough of disillusionment' in which the field of anticancer virotherapy finds itself and suggests reasons for optimism.

Breaking the barriers in cancer care: The next generation of herpes simplex virus-based oncolytic immunotherapies for cancer treatment

Since the US Food and Drug Administration first approved talimogene laherparepvec for the treatment of melanoma in 2015, the field of oncolytic immunotherapy (OI) has rapidly evolved. There are numerous ongoing clinical studies assessing the clinical activity of OIs across a wide range of tumor types. Further understanding of the mechanisms underlying the anti-tumor immune response has led to the development of OIs with improved immune-mediated preclinical efficacy. In this review, we discuss the key approaches for developing the next generation of herpes simplex virus-based OIs. Modifications to the viral genome and incorporation of transgenes to promote safety, tumor-selective replication, and immune stimulation are reviewed. We also review the advantages and disadvantages of intratumoral versus intravenous administration, summarize clinical evidence supporting the use of OIs as a strategy to overcome resistance to immune checkpoint blockade, and consider emerging opportunities to improve OI efficacy in the combination setting.

Clinical Advances and Future Directions of Oncolytic Virotherapy for Head and Neck Cancer

Oncolytic viruses (OVs), without harming normal tissues, selectively infect and replicate within tumor cells, to release immune molecules and tumor antigens, achieving immune-mediated destruction of tumors and making them one of the most promising immunotherapies for cancer. Many clinical studies have demonstrated that OVs can provide clinical benefits for patients with different types of tumors, at various stages, including metastatic and previously untreatable cases. When OVs are used in combination with chemotherapy, radiotherapy, immunotherapy, and other treatments, they can synergistically enhance the therapeutic effects. The concept of oncolytic virotherapy (OVT) was proposed in the early 20th century. With advancements in genetic engineering, genetically modified viruses can further enhance the efficacy of cancer immunotherapy. In recent years, global research on OV treatment of malignant tumors has increased dramatically. This article comprehensively reviews the findings from relevant research and clinical trials, providing an overview of the development of OVT and its application in the clinical treatment of head and neck cancer. The aim is to offer insights for future clinical and fundamental research on OVT.

Update of latest data for combined therapy for esophageal cancer using radiotherapy and immunotherapy: A focus on efficacy, safety, and biomarkers

Esophageal cancer usually has a poor prognosis. Given the significant breakthrough with tumor immunotherapy, an increasing number of clinical studies have demonstrated that the combination of radiotherapy and immune checkpoint inhibitors (ICIs) may have a synergistic effect and good outcome in esophageal cancer. Clinical studies of immunoradiotherapy (iRT) for esophageal cancer have proliferated enormously from 2021 to the present. However, a summary of the efficacy and toxicity of combined therapy to guide esophageal cancer treatment in clinical practice is lacking. For this review, we integrate the latest data to analyze and assess the efficacy and safety of iRT for esophageal cancer. In addition, we discuss better predictive biomarkers, therapeutic options for specific populations, and other challenges to identify directions for future research design.

Anticancer Activity of Measles-Mumps-Rubella MMR Vaccine Viruses against Glioblastoma

BACKGROUND

Oncolytic viruses (OVs) have been utilized since 1990s for targeted cancer treatment. Our study examined the Measles-Mumps-Rubella (MMR) vaccine's cancer-killing potency against Glioblastoma (GBM), a therapy-resistant, aggressive cancer type.

METHODOLOGY

We used GBM cell lines, primary GBM cells, and normal mice microglial cells, to assess the MMR vaccine's efficacy through cell viability, cell cycle analysis, intracellular viral load via RT-PCR, and Transmission Electron Microscopy (TEM).

RESULTS

After 72 h of MMR treatment, GBM cell lines and primary GBM cells exhibited significant viability reduction compared to untreated cells. Conversely, normal microglial cells showed only minor changes in viability and morphology. Intracellular viral load tests indicated GBM cells' increased sensitivity to MMR viruses compared to normal cells. The cell cycle study also revealed measles and mumps viruses' crucial role in cytopathic effects, with the rubella virus causing cell cycle arrest.

CONCLUSION

Herein the reported results demonstrate the anti-cancer activity of the MMR vaccine against GBM cells. Accordingly, the MMR vaccine warrants further study as a potential new tool for GBM therapy and relapse prevention. Therapeutic potential of the MMR vaccine has been found to be promising in earlier studies as well.

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.

Oncolytic Virotherapy for High-Grade Glioma and Current Evidence and Factors to Consider for Incorporation into Clinical Practice

Brain tumor incidence is on the rise, and glioblastoma comprises the majority of primary tumors. Despite maximal safe resection and adjuvant chemoradiation, median survival for high-grade glioma remains poor. For this reason, it is important to develop and incorporate new treatment strategies. Oncolytic virotherapy has emerged as a viable new therapeutic entity to fill this gap. Preclinical research has shown oncolytic virotherapy to be a robust and effective treatment option for brain tumors, and clinical trials for both adult and pediatric high-grade glioma are underway. The unique and protected environment of the nervous system, in part due to the blood-brain barrier, prevents traditional systemic therapies from achieving adequate penetration. Brain tumors are also heterogenous in nature due to their diverse molecular profiles, further complicating systemic treatment efforts. Oncolytic viruses may serve to fill this gap in brain tumor treatment given their amenability to genetic modification and ability to target unique tumor epitopes. In addition, direct inoculation of the oncolytic virus agent to the tumor bed following surgical resection absolves risk of systemic side effects and ensures adequate delivery. As virotherapy transitions from bench to bedside, it is important to discuss factors to make this transition more seamless. In this article, we describe the current clinical evidence as it pertains to oncolytic virotherapy and the treatment of brain tumors as well as factors to consider for its incorporation into neurosurgical workflow.

Current Status and Challenges of Oncolytic Virotherapy for the Treatment of Glioblastoma

Despite decades of research and numerous clinical trials, the prognosis of patients diagnosed with glioblastoma (GBM) remains dire with median observed survival at 8 months. There is a critical need for novel treatments for GBM, which is the most common malignant primary brain tumor. Major advances in cancer therapeutics such as immune checkpoint inhibitors and chimeric antigen receptor (CAR) T-cell therapy have not yet led to improved outcomes for GBM. Conventional therapy of surgery followed by chemoradiation with or without tumor treating fields remains the standard of care. One of the many approaches to GBM therapy currently being explored is viral therapies. These typically work by selectively lysing target neoplastic cells, called oncolysis, or by the targeted delivery of a therapeutic transgene via a viral vector. In this review, we discuss the underlying mechanisms of action and describe both recent and current human clinical trials using these viruses with an emphasis on promising viral therapeutics that may ultimately break the field's current stagnant paradigm.

Combination IFNβ and Membrane-Stable CD40L Maximize Tumor Dendritic Cell Activation and Lymph Node Trafficking to Elicit Systemic T-cell Immunity

Oncolytic virus therapies induce the direct killing of tumor cells and activation of conventional dendritic cells (cDC); however, cDC activation has not been optimized with current therapies. We evaluated the adenoviral delivery of engineered membrane-stable CD40L (MEM40) and IFNβ to locally activate cDCs in mouse tumor models. Combined tumor MEM40 and IFNβ expression induced the highest cDC activation coupled with increased lymph node migration, increased systemic antitumor CD8+ T-cell responses, and regression of established tumors in a cDC1-dependent manner. MEM40 + IFNβ combined with checkpoint inhibitors led to effective control of distant tumors and lung metastases. An oncolytic adenovirus (MEM-288) expressing MEM40 + IFNβ  in phase I clinical testing induced cancer cell loss concomitant with enhanced T-cell infiltration and increased systemic presence of tumor T-cell clonotypes in non-small cell lung cancer (NSCLC) patients. This approach to simultaneously target two major DC-activating pathways has the potential to significantly affect the solid tumor immunotherapy landscape.

History of how viruses can fight cancer: From the miraculous healings to the approval of oncolytic viruses

Since the nineteenth century, several reports in the historical medical literature emphasized that, occasionally, cancer patients showed a clinical remission, called "Saint Peregrine tumor" as a result of natural infections. Moreover, additional evidence indicated that viruses show a tropism toward cancer cells, leading to the discovery of oncolytic activity of several viruses, called oncolytic viruses (OVs). With the technological and scientific advancements, the advent of rodent models, the establishment of in vitro cell lines, the introduction of methods for virus propagation, several attempts through the 1950s and 1970s have been made to increase OVs specificity, efficacy and safety; however, inconclusive/negative results have been reached and many researchers abandoned the field. Only in the later 1990s, the genetic engineering and the recombinant DNA techniques that allowed the generation of potent, specific and safe OVs and a better understanding of cancer cells renewed the interest in virotherapy. Currently, virotherapy represents a cancer therapeutic strategy based on the use of OVs that selectively infect and lyse cancer cells, without harming normal cells. Over the past years, several "natural" and "genetic engineered" viruses, have been investigated in clinical studies and some of them revealed encouraging results. Recently, the clinical use of OVs has also been supported by the immune stimulatory property of OVs against tumor cells. Here, we analyze the early oncolytic virotherapy before genetic engineering to highlight the relevant progresses reached, and the mechanism to stimulate host immune response, a significant challenge in current virotherapy field.

The Adenovirus Vector Platform: Novel Insights into Rational Vector Design and Lessons Learned from the COVID-19 Vaccine

The adenovirus vector platform remains one of the most efficient toolboxes for generation of transfer vehicles used in gene therapy and virotherapy to treat tumors, as well as vaccines to protect from infectious diseases. The adenovirus genome and capsids can be modified using highly efficient techniques, and vectors can be produced at high titers, which facilitates their rapid adaptation to current needs and disease applications. Over recent years, the adenovirus vector platform has been in the center of attention for vaccine development against the ongoing coronavirus SARS-CoV-2/COVID-19 pandemic. The worldwide deployment of these vaccines has greatly deepened the knowledge on virus-host interactions and highlighted the need to further improve the effectiveness and safety not only of adenovirus-based vaccines but also of gene therapy and oncolytic virotherapy vectors. Based on the current evidence, we discuss here how adenoviral vectors can be further improved by intelligent molecular design. This review covers the full spectrum of state-of-the-art strategies to avoid vector-induced side effects ranging from the vectorization of non-canonical adenovirus types to novel genome engineering techniques.

Immunovirotherapy: The role of antibody based therapeutics combination with oncolytic viruses

Despite the fact that the new drugs and targeted therapies have been approved for cancer therapy during the past 30 years, the majority of cancer types are still remain challenging to be treated. Due to the tumor heterogeneity, immune system evasion and the complex interaction between the tumor microenvironment and immune cells, the great majority of malignancies need multimodal therapy. Unfortunately, tumors frequently develop treatment resistance, so it is important to have a variety of therapeutic choices available for the treatment of neoplastic diseases. Immunotherapy has lately shown clinical responses in malignancies with unfavorable outcomes. Oncolytic virus (OV) immunotherapy is a cancer treatment strategy that employs naturally occurring or genetically-modified viruses that multiply preferentially within cancer cells. OVs have the ability to not only induce oncolysis but also activate cells of the immune system, which in turn activates innate and adaptive anticancer responses. Despite the fact that OVs were translated into clinical trials, with T-VECs receiving FDA approval for melanoma, their use in fighting cancer faced some challenges, including off-target side effects, immune system clearance, non-specific uptake, and intratumoral spread of OVs in solid tumors. Although various strategies have been used to overcome the challenges, these strategies have not provided promising outcomes in monotherapy with OVs. In this situation, it is increasingly common to use rational combinations of immunotherapies to improve patient benefit. With the development of other aspects of cancer immunotherapy strategies, combinational therapy has been proposed to improve the anti-tumor activities of OVs. In this regard, OVs were combined with other biotherapeutic platforms, including various forms of antibodies, nanobodies, chimeric antigen receptor (CAR) T cells, and dendritic cells, to reduce the side effects of OVs and enhance their efficacy. This article reviews the promising outcomes of OVs in cancer therapy, the challenges OVs face and solutions, and their combination with other biotherapeutic agents.

Oncolytic Adenoviruses: The Cold War against Cancer Finally Turns Hot

Oncolytic viruses, colloquially referred to as "living drugs", amplify themselves and the therapeutic transgenes that they carry to stimulate an immune response both locally and systemically. Remarkable exceptions aside, such as the recent 14-patient trial with the PD-1 inhibitor, dostarlimab, in mismatch repair (MMR) deficient rectal cancer, where the complete response rate was 100%, checkpoint inhibitors are not cure-alls, which suggests the need for a combination partner like oncolytic viruses to prime and augment their activity. This review focuses on adenoviruses, the most clinically investigated of all the oncolytic viruses. It covers specific design features of clinical adenoviral candidates and highlights their potential both alone and in combination with checkpoint inhibitors in clinical trials to turn immunologically "cold" and unresponsive tumors into "hotter" and more responsive ones through a domino effect. Finally, a "mix-and-match" combination of therapies based on the paradigm of the cancer-immunity cycle is proposed to augment the immune responses of oncolytic adenoviruses.

BETA PRIME: Phase I study of AdAPT-001 as monotherapy and combined with a checkpoint inhibitor in superficially accessible, treatment-refractory solid tumors

AdAPT-001 is an investigational therapy consisting of a replicative type 5 adenovirus armed with a TGF-β receptor-immunoglobulin Fc fusion trap, designed to neutralize isoforms 1 and 3 of the profibrotic and immunosuppressive cytokine, TGF-β. In preclinical studies with an immunocompetent mouse model, AdAPT-001 eradicated directly treated 'cold' tumors as well as distant untreated tumors, and, from its induction of systemic CD8+ T cell-mediated antitumor immunity, protected the mice from rechallenge with tumor cells. AdAPT-001 also sensitized resistant tumors to checkpoint blockade. This manuscript describes the rationale and design of the first-in-human phase I, dose-escalation and dose-expansion study of AdAPT-001 alone and in combination with a checkpoint inhibitor in adults with treatment-refractory superficially accessible solid tumors.

Strategies for Advanced Oncolytic Virotherapy: Current Technology Innovations and Clinical Approaches

Oncolytic virotherapy is a type of nanomedicine with a dual antitumor mechanism. Viruses are engineered to selectively infect and lyse cancer cells directly, leading to the release of soluble antigens which induce systemic antitumor immunity. Representative drug Talimogene laherparepvec has showed promising therapeutic effects in advanced melanoma, especially when combined with immune checkpoint inhibitors with moderate adverse effects. Diverse viruses like herpes simplex virus, adenovirus, vaccina virus, and so on could be engineered as vectors to express different transgenic payloads, vastly expanding the therapeutic potential of oncolytic virotherapy. A number of related clinical trials are under way which are mainly focusing on solid tumors. Studies about further optimizing the genome of oncolytic viruses or improving the delivering system are in the hotspot, indicating the future development of oncolytic virotherapy in the clinic. This review introduces the latest progress in clinical trials and pre-clinical studies as well as technology innovations directed at oncolytic viruses. The challenges and perspectives of oncolytic virotherapy towards clinical application are also discussed.

AdAPT-001, an oncolytic adenovirus armed with a TGF-β trap, overcomes in vivo resistance to PD-L1-immunotherapy

Monoclonal antibodies targeting the programmed cell death protein-1/programmed cell death-ligand 1 (PD-1/PD-L1) and cytotoxic T lymphocyte-associated protein-4 (CTLA-4) axes have permanently changed the therapeutic landscape for multiple tumor types previously associated with a dismal prognosis such as melanoma, non-small cell lung cancer, renal cell carcinoma, bladder cancer, head and neck squamous cell carcinoma, MSI-high colorectal carcinoma, Merkel cell carcinoma, and Hodgkin lymphoma. However, only a subset of patients initially benefits from these inhibitors, and increasing clinical experience indicates that in a substantial proportion of initial responders, lethal secondary resistance ultimately develops months or years later. In this paper we evaluated combination therapy with a Phase 1 oncolytic adenovirus called AdAPT-001, armed with a TGF-β "trap" that binds to and neutralizes the immunosuppressive cytokine, TGF-β, and a checkpoint inhibitor, anti-PD-L1, in PD-L1 resistant tumors. The study, which was performed in an immunocompetent syngeneic ADS-12 mouse model, demonstrated that the combination of AdAPT-001 with PD-L1 blockade reversed PD-L1 resistance, potentially representing a future paradigm shift for patients that are primarily or secondarily resistant to checkpoint inhibitors.

Targeting Triple Negative Breast Cancer With Oncolytic Adenoviruses

Breast cancer (BC) is the most common cancer globally, accounting for 685,000 deaths in 2020. Triple-negative breast cancers (TNBC) lack oestrogen (ER) and progesterone (PR) hormone receptor expression and HER2 overexpression. TNBC represent 10–15% of all BC with high incidence in women under 50-years old that have BRCA mutations, and have a dismal prognosis. African American and Hispanic women are at higher risk partly due to the common occurrence of BRCA mutations. The standard treatment for TNBC includes surgery, radiotherapy, and chemotherapy although, resistance to all standard-of-care therapies eventually develops. It is crucial to identify and develop more efficacious therapeutics with different mechanisms of action to improve on survival in these women. Recent findings with oncolytic adenoviruses (OAds) may generate a new strategy to improve on the outcomes for women afflicted by TNBC and other types of BC. OAds are genetically engineered to selectively lyse, eliminate and recruit the host antitumour immune responses, leaving normal cells unharmed. The most common modifications are deletions in the early gene products including the E1B55 KDa protein, specific regions of the E1A protein, or insertion of tumour-specific promoters. Clinical trials using OAds for various adenocarcinomas have not yet been sufficiently evaluated in BC patients. Preclinical studies demonstrated efficacy in BC cell lines, including TNBC cells, with promising novel adenoviral mutants. Here we review the results reported for the most promising OAds in preclinical studies and clinical trials administered alone and in combination with current standard of care or with novel therapeutics. Combinations of OAds with small molecule drugs targeting the epidermal growth factor receptor (EGFR), androgen receptor (AR), and DNA damage repair by the novel PARP inhibitors are currently under investigation with reported enhanced efficacy. The combination of the PARP-inhibitor Olaparib with OAds showed an impressive anti-tumour effect. The most promising findings to date are with OAds in combination with antibodies towards the immune checkpoints or expression of cytokines from the viral backbone. Although safety and efficacy have been demonstrated in numerous clinical trials and preclinical studies with cancer-selective OAds, further developments are needed to eliminate metastatic lesions, increase immune activation and intratumoural viral spread. We discuss shortcomings of the OAds and potential solutions for improving on patient outcomes.

Remission of Liquid Tumors and SARS-CoV-2 Infection: a Literature Review

The coronavirus disease 2019 (COVID-19) pandemic has produced a new global challenge for patients with cancer. The disease and the immunosuppression induced by cancer therapies have generated a perfect storm of conditions to increase the severity of the symptoms and worsen the prognosis. However, a few clinical reports showcased the power of viruses to induce remission in some patients suffering from liquid tumors. Here, we reviewed six cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that resulted in cancer remission, simultaneously highlighting the strengths and the unique challenges of oncolytic virotherapy. Virotherapy has become a special case of cancer immunotherapy. This paradigm-shifting concept suggests that oncolytic viruses are not only promising agents to combat particularly immunologically suppressed, immunotherapy-resistant tumors but also that the trigger of local inflammation, such as SARS-CoV-2 infection of the respiratory pathways, may trigger an abscopal effect sufficient to induce the remission of systemic cancer.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

The Multi-Faceted Role of Autophagy During Animal Virus Infection

Autophagy is a process of degradation to maintain cellular homeostatic by lysosomes, which ensures cellular survival under various stress conditions, including nutrient deficiency, hypoxia, high temperature, and pathogenic infection. Xenophagy, a form of selective autophagy, serves as a defense mechanism against multiple intracellular pathogen types, such as viruses, bacteria, and parasites. Recent years have seen a growing list of animal viruses with autophagy machinery. Although the relationship between autophagy and human viruses has been widely summarized, little attention has been paid to the role of this cellular function in the veterinary field, especially today, with the growth of serious zoonotic diseases. The mechanisms of the same virus inducing autophagy in different species, or different viruses inducing autophagy in the same species have not been clarified. In this review, we examine the role of autophagy in important animal viral infectious diseases and discuss the regulation mechanisms of different animal viruses to provide a potential theoretical basis for therapeutic strategies, such as targets of new vaccine development or drugs, to improve industrial production in farming.

Ixovex-1, a novel oncolytic E1B-mutated adenovirus

There is a great demand for improved oncolytic viruses that selectively replicate within cancer cells while sparing normal cells. Here, we describe a novel oncolytic adenovirus, Ixovex-1, that obtains a cancer-selective replication phenotype by modulating the level of expression of the different, alternatively spliced E1B mRNA isoforms. Ixovex-1 is a recombinant adenovirus that carries a single point mutation in the E1B-93R 3' splice acceptor site that results in overexpression of the E1B-156R splice isoform. In this paper, we studied the characteristics of this novel oncolytic adenovirus by validating its in vitro behaviour in a panel of normal cells and cancer cells. We additionally studied its anti-tumour efficacy in vivo. Ixovex-1 significantly inhibited tumour growth and prolonged survival of mice in an immune-deficient lung carcinoma tumour implantation model. In complementation experiments, overexpression of E1B-156R was shown to increase the oncolytic index of both Ad5wt and ONYX-015. In contrast to prior viruses of similar type, Ixovex-1 includes a functional E3B region for better in vivo efficacy. Throughout this study, the Ixovex-1 virus has been proven to be superior in competency compared to a virus with multiple deletions.

Clinical Trials of Oncolytic Viruses in Breast Cancer

Breast cancer is the second most common kind of cancer worldwide and oncolytic viruses may offer a new treatment approach. There are three different types of oncolytic viruses used in clinical trials; (i) oncolytic viruses with natural anti-neoplastic properties; (ii) oncolytic viruses designed for tumor-selective replication; (iii) oncolytic viruses modified to activate the immune system. Currently, fourteen different oncolytic viruses have been investigated in eighteen published clinical trials. These trials demonstrate that oncolytic viruses are well tolerated and safe for use in patients and display clinical activity. However, these trials mainly studied a small number of patients with different advanced tumors including some with breast cancer. Future trials should focus on breast cancer and investigate optimal routes of administration, occurrence of neutralizing antibodies, viral gene expression, combinations with other antineoplastic therapies, and identify subtypes that are particularly suitable for oncolytic virotherapy.

Oncolytic Viruses: Newest Frontier for Cancer Immunotherapy

Cancer remains a leading cause of death worldwide. Despite many signs of progress, currently available cancer treatments often do not provide desired outcomes for too many cancers. Therefore, newer and more effective therapeutic approaches are needed. Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively targets and kills cancer cells while sparing normal ones. In the past several decades, many different OV candidates have been developed and tested in both laboratory settings as well as in cancer patient clinical trials. Many approaches have been taken to overcome the limitations of OVs, including engineering OVs to selectively activate anti-tumor immune responses. However, newer approaches like the combination of OVs with current immunotherapies to convert "immune-cold" tumors to "immune-hot" will almost certainly improve the potency of OVs. Here, we discuss strategies that are explored to further improve oncolytic virotherapy.

Oncolytic virus therapy in cancer: A current review

In view of the advancement in the understanding about the most diverse types of cancer and consequently a relentless search for a cure and increased survival rates of cancer patients, finding a therapy that is able to combat the mechanism of aggression of this disease is extremely important. Thus, oncolytic viruses (OVs) have demonstrated great benefits in the treatment of cancer because it mediates antitumor effects in several ways. Viruses can be used to infect cancer cells, especially over normal cells, to present tumor-associated antigens, to activate "danger signals" that generate a less immune-tolerant tumor microenvironment, and to serve transduction vehicles for expression of inflammatory and immunomodulatory cytokines. The success of therapies using OVs was initially demonstrated by the use of the genetically modified herpes virus, talimogene laherparepvec, for the treatment of melanoma. At this time, several OVs are being studied as a potential treatment for cancer in clinical trials. However, it is necessary to be aware of the safety and possible adverse effects of this therapy; after all, an effective treatment for cancer should promote regression, attack the tumor, and in the meantime induce minimal systemic repercussions. In this manuscript, we will present a current review of the mechanism of action of OVs, main clinical uses, updates, and future perspectives on this treatment.

Oncolytic Virotherapy for Melanoma Brain Metastases, a Potential New Treatment Paradigm?

INTRODUCTION

Melanoma brain metastases remain a devastating disease process with poor prognosis. Recently, there has been a surge in studies demonstrating the efficacy of oncolytic virotherapy for brain tumor treatment. Given their specificity and amenability to genetic modification, the authors explore the possible role of oncolytic virotherapy as a potential treatment option for patients with melanoma brain metastases.

METHODS

A comprehensive literature review including both preclinical and clinical evidence of oncolytic virotherapy for the treatment of melanoma brain metastasis was performed.

RESULTS

Oncolytic virotherapy, specifically T-VEC (Imlygic™), was approved for the treatment of melanoma in 2015. Recent clinical trials demonstrate promising anti-tumor changes in patients who have received T-VEC; however, there is little evidence for its use in metastatic brain disease based on the existing literature. To date, only two single cases utilizing virotherapy in patients with metastatic brain melanoma have been reported, specifically in patients with treatment refractory disease. Currently, there is not sufficient data to support the use of T-VEC or other viruses for intracranial metastatic melanoma. In developing a virotherapy treatment paradigm for melanoma brain metastases, several factors must be considered, including route of administration, need to bypass the blood-brain barrier, viral tumor infectivity, and risk of adverse events.

CONCLUSIONS

Evidence for oncolytic virotherapy treatment of melanoma is limited primarily to T-VEC, with a noticeable paucity of data in the literature with respect to brain tumor metastasis. Given the promising findings of virotherapy for other brain tumor types, oncolytic virotherapy has great potential to offer benefits to patients afflicted with melanoma brain metastases and warrants further investigation.

Clinical translation of immunomodulatory therapeutics

Immunomodulatory therapeutics represent a unique class of drug products that have tremendous potential to rebalance malfunctioning immune systems and are quickly becoming one of the fastest-growing areas in the pharmaceutical industry. For these drugs to become mainstream medicines, they must provide greater therapeutic benefit than the currently used treatments without causing severe toxicities. Immunomodulators, cell-based therapies, antibodies, and viral therapies have all achieved varying amounts of success in the treatment of cancers and/or autoimmune diseases. However, many challenges related to precision dosing, off-target effects, and manufacturing hurdles will need to be addressed before we see widespread adoption of these therapies in the clinic. This review provides a perspective on the progress of immunostimulatory and immunosuppressive therapies to date and discusses the opportunities and challenges for clinical translation of the next generation of immunomodulatory therapeutics.

The spontaneous remission of cancer: Current insights and therapeutic significance

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Spontaneous remission (SR) of cancer is a rare but well-documented phenomenon.

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Mechanisms of SR are described in detail.

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Knowing the intricacies of SR would help in devising novel treatment strategies.

Many diseases heal spontaneously. The common cold, for example, remedies itself within a few days in people with an uncompromised immune system. If a disease with a poor prognosis heals in the absence of a targeted therapeutic, many even call it a miracle cure. Such is the case with the spontaneous regression (SR) of malignant neoplasms, a rare but well-documented phenomenon that finds its first mention in the Ebers Papyrus of 1550 BCE. Given the challenges associated with current cancer treatment modalities such as rapidly evolving drug resistance mechanisms, dose-limiting side effects, and a failure to completely eliminate cancer cells, knowledge of how a tumour heals itself would be immensely helpful in developing more effective therapeutic modalities. Although the intricate mechanisms of SR have yet to be fully elucidated, it has been shown that infection-mediated immune system activation, biopsy procedures, and disruptions of the tumour microenvironment play pivotal roles in the self-healing of many tumours. Bacterial and viral infections are especially well-documented in instances of SR. Insights from these findings are paving the way for novel therapeutic strategies. Inspired by bacteria-mediated SR, Bacillus Calmette-Guérin (BCG) has been used as an approved treatment option for non-muscle-invasive bladder cancer (NMIBC). Similarly, Talimogene laherparepvec (T-VEC), the first engineered oncolytic herpes simplex virus (HSV), has been approved by the United States Food and Drug Administration for the treatment of some forms of advanced melanoma. Here we describe the current understanding of SR, explore its therapeutic significance, and offer perspectives on its future.

An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression

A majority of mesothelioma specimens were defective of p14 and p16 expression due to deletion of the INK4A/ARF region, and the p53 pathway was consequently inactivated by elevated MDM2 functions which facilitated p53 degradaton. We investigated a role of p53 elevation by MDM2 inhibitors, nutlin-3a and RG7112, in cytotoxicity of replication-competent adenoviruses (Ad) lacking the p53-binding E1B55kDa gene (Ad-delE1B). We found that a growth inhibition by p53-activating Ad-delE1B was irrelevant to p53 expression in the infected cells, but combination of Ad-delE1B and the MDM2 inhibitor produced synergistic inhibitory effects on mesothelioma with the wild-type but not mutated p53 genotype. The combination augmented p53 phosphorylation, activated apoptotic but not autophagic pathway, and enhanced DNA damage signals through ATM-Chk2 phosphorylation. The MDM2 inhibitors facilitated production of the Ad progenies through augmented expression of nuclear factor I (NFI), one of the transcriptional factors involved in Ad replications. Knocking down of p53 with siRNA did not increase the progeny production or the NFI expression. We also demonstrated anti-tumor effects by the combination of Ad-delE1B and the MDM2 inhibitors in an orthotopic animal model. These data collectively indicated that upregulation of wild-type p53 expression contributed to cytotoxicity by E1B55kDa-defective replicative Ad through NFI induction and suggested that replication-competent Ad together with augmented p53 levels was a therapeutic strategy for p53 wild-type mesothelioma.

Considering the potential for gene-based therapy in prostate cancer

Therapeutic gene manipulation has been at the forefront of popular scientific discussion and basic and clinical research for decades. Basic and clinical research applications of CRISPR-Cas9-based technologies and ongoing clinical trials in this area have demonstrated the potential of genome editing to cure human disease. Evaluation of research and clinical trials in gene therapy reveals a concentration of activity in prostate cancer research and practice. Multiple aspects of prostate cancer care - including anatomical considerations that enable direct tumour injections and sampling, the availability of preclinical immune-competent models and the delineation of tumour-related antigens that might provide targets for an induced immune system - make gene therapy an appealing treatment option for this common malignancy. Vaccine-based therapies that induce an immune response and new technologies exploiting CRISPR-Cas9-assisted approaches, including chimeric antigen receptor (CAR) T cell therapies, are very promising and are currently under investigation both in the laboratory and in the clinic. Although laboratory and preclinical advances have, thus far, not led to oncologically relevant outcomes in the clinic, future studies offer great promise for gene therapy to become established in prostate cancer care.

Combining IL-10 and Oncolytic Adenovirus Demonstrates Enhanced Antitumor Efficacy Through CD8+ T Cells

Oncolytic viruses are of growing importance in cancer therapeutics since they combine direct oncolytic effect and the stimulation of antitumor immunity. Emerging evidences showed that the function of oncolytic viruses is dependent on immune response in tumor microenvironment, and the modulation of immunity could influence their efficacy. Here we combined the interleukin 10 (IL-10) and oncolytic adenovirus Ad-hTERT to treat lung cancer and explored the underlying mechanism under combination therapy. Lewis lung carcinoma (LLC) and B16F10 tumor-bearing immunocompetent C57BL/6 mice that received Ad-hTERT or IL-10 alone showed mild antitumor effect, while the combination therapy shrink tumor bulks and prolonged survival remarkably. In addition, IL-10 didn’t show direct influence on tumor cell viability or Ad-hTERT mediated tumor cell lysis in vitro. To further explore the influence of combination therapy mediated antitumor capacity, we eliminated CD8⁺ T, CD4⁺ T or natural killer (NK) cells in LLC and B16F10-bearing C57BL/6 mice, and found that CD8⁺ T cells were critical mediator in the combination therapy. The combination therapy induced intensive infiltration of CD8⁺ T cells in tumors, increased tumor-specific IFN-γ secretion by CD8⁺ T cells. The long-term tumor-specific immune memory induced by the combination therapy rejected rechallenge by respective tumor cell lines. This study demonstrated that the therapy combining IL-10 and Ad-hTERT augmented antitumor efficacy which was CD8⁺ T cells dependent. Our findings paved the way to combine cytokines and oncolytic viruses to enhance antitumor immunotherapy in treating cancer.

Personalizing Oncolytic Virotherapy for Glioblastoma: In Search of Biomarkers for Response

Simple Summary

Glioblastoma (GBM) is the most frequent and aggressive primary brain tumor. Despite multimodal treatment, the prognosis of GBM patients remains very poor. Oncolytic virotherapy is being evaluated as novel treatment for this patient group and clinical trials testing oncolytic viruses have shown impressive responses, albeit in a small subset of GBM patients. Obtaining insight into specific tumor- or patient-related characteristics of the responding patients, may in the future improve response rates. In this review we discuss factors related to oncolytic activity of the most widely applied oncolytic virus strains as well as potential biomarkers and future assays that may allow us to predict response to these agents. Such biomarkers and tools may in the future enable personalizing oncolytic virotherapy for GBM patients.

Abstract

Oncolytic virus (OV) treatment may offer a new treatment option for the aggressive brain tumor glioblastoma. Clinical trials testing oncolytic viruses in this patient group have shown promising results, with patients achieving impressive long-term clinical responses. However, the number of responders to each OV remains low. This is thought to arise from the large heterogeneity of these tumors, both in terms of molecular make-up and their immune-suppressive microenvironment, leading to variability in responses. An approach that may improve response rates is the personalized utilization of oncolytic viruses against Glioblastoma (GBM), based on specific tumor- or patient-related characteristics. In this review, we discuss potential biomarkers for response to different OVs as well as emerging ex vivo assays that in the future may enable selection of optimal OV for a specific patient and design of stratified clinical OV trials for GBM.

Intraarterial delivery of virotherapy for glioblastoma

Oncolytic viruses (OVs) have been used in the treatment of cancer, in a focused manner, since the 1990s. These OVs have become popular in the treatment of several cancers but are only now gaining interest in the treatment of glioblastoma (GBM) in recent clinical trials. In this review, the authors discuss the unique applications of intraarterial (IA) delivery of OVs, starting with concepts of OV, how they apply to IA delivery, and concluding with discussion of the current ongoing trials. Several OVs have been used in the treatment of GBM, including specifically several modified adenoviruses. IA delivery of OVs has been performed in the hepatic circulation and is now being studied in the cerebral circulation to help enhance delivery and specificity. There are some interesting synergies with immunotherapy and IA delivery of OVs. Some of the shortcomings are discussed, specifically the systemic response to OVs and feasibility of treatment. Future studies can be performed in the preclinical setting to identify the ideal candidates for translation into clinical trials, as well as the nuances of this novel delivery method.

Delta-24 adenoviral therapy for glioblastoma: evolution from the bench to bedside and future considerations

Delta-24-based oncolytic viruses are conditional replication adenoviruses developed to selectively infect and replicate in retinoblastoma 1 (Rb)-deficient cancer cells but not normal cell with intact Rb1 pathways. Over the years, there has been a significant evolution in the design of Delta-24 based on a better understanding of the underlying basis for infection, replication, and spread within cancer. One example is the development of Delta-24-RGD (DNX-2401), where the arginine-glycine-aspartate (RGD) domain enhances the infectivity of Delta-24 for cancer cells. DNX-2401 demonstrated objective biological and clinical responses during a phase I window of opportunity clinical trial for recurrent human glioblastoma. In long-term responders (> 3 years), there was evidence of immune infiltration (T cells and macrophages) into the tumor microenvironment with minimal toxicity. Although more in-depth analysis and phase III studies are pending, these results indicate that Delta-24-based adenovirus therapy may induce an antitumor response in glioblastoma, resulting in long-term antitumor immune response. In this review, the authors discuss the preclinical and clinical development of Delta-24 oncolytic adenoviral therapy for glioblastoma and describe structural improvements to Delta-24 that have enhanced its efficacy in vivo. They also highlight ongoing research that attempts to address the remaining obstacles limiting efficacy of Delta-24 adenovirus therapy for glioblastoma.

Oncolytic Viruses and Hematological Malignancies: A New Class of Immunotherapy Drugs

The use of viruses for tumour treatment has been imagined more than one hundred years ago, when it was reported that viral diseases were occasionally leading to a decrease in neoplastic lesions. Oncolytic viruses (OVs) seem to have a specific tropism for tumour cells. Previously, it was hypothesised that OVs’ antineoplastic actions were mainly due to their ability to contaminate, proliferate and destroy tumour cells and the immediate destructive effect on cells was believed to be the single mechanism of action of OVs’ action. Instead, it has been established that oncolytic viruses operate via a multiplicity of systems, including mutation of tumour milieu and a composite change of the activity of immune effectors. Oncolytic viruses redesign the tumour environment towards an antitumour milieu. The aim of our work is to evaluate the findings present in the literature about the use of OVs in the cure of haematological neoplastic pathologies such as multiple myeloma, acute and chronic myeloid leukaemia, and lymphoproliferative diseases. Further experimentations are essential to recognize the most efficient virus or treatment combinations for specific haematological diseases, and the combinations able to induce the strongest immune response.

Hitting the Target but Missing the Point: Recent Progress towards Adenovirus-Based Precision Virotherapies

More people are surviving longer with cancer. Whilst this can be partially attributed to advances in early detection of cancers, there is little doubt that the improvement in survival statistics is also due to the expansion in the spectrum of treatments available for efficacious treatment. Transformative amongst those are immunotherapies, which have proven effective agents for treating immunogenic forms of cancer, although immunologically "cold" tumour types remain refractive. Oncolytic viruses, such as those based on adenovirus, have great potential as anti-cancer agents and have seen a resurgence of interest in recent years. Amongst their many advantages is their ability to induce immunogenic cell death (ICD) of infected tumour cells, thus providing the alluring potential to synergise with immunotherapies by turning immunologically "cold" tumours "hot". Additionally, enhanced immune mediated cell killing can be promoted through the local overexpression of immunological transgenes, encoded from within the engineered viral genome. To achieve this full potential requires the development of refined, tumour selective "precision virotherapies" that are extensively engineered to prevent off-target up take via native routes of infection and targeted to infect and replicate uniquely within malignantly transformed cells. Here, we review the latest advances towards this holy grail within the adenoviral field.

Effective combinations of radiotherapy and immunotherapy in the treatment of esophageal squamous cell carcinoma

The traditional treatments for esophageal squamous cell carcinoma include surgery and radiation as local therapies, then chemotherapy and targeted therapy as systemic treatments. These treatments, either alone or in combination, however, are not satisfactory because of limited efficacy and unfavorable toxicity, calling for new therapeutic strategies. In recent years, immunotherapy, a new weapon in the arsenal against cancer, has shown substantial clinical benefits in patients with esophageal squamous cell carcinoma, particularly ones with locally advanced or metastatic disease. Importantly, accumulating evidence suggests that traditional radiation therapy functions as a powerful adjuvant for immunotherapy by contributing to systemic antitumor immunity, resulting in reduced recurrence risk and improved survival of patients. Here the authors summarize the emerging data on immunotherapy- and radiation therapy-based treatment of esophageal squamous cell carcinoma and discuss the pros and cons of different combinations, aiming at a comprehensive understanding of the proper rationale for the design of effective therapeutic regimens.

The Oncolytic Virus in Cancer Diagnosis and Treatment

Cancer has always been an enormous threat to human health and survival. Surgery, radiotherapy, and chemotherapy could improve the survival of cancer patients, but most patients with advanced cancer usually have a poor survival or could not afford the high cost of chemotherapy. The emergence of oncolytic viruses provided a new strategy for us to alleviate or even cure malignant tumors. An oncolytic virus can be described as a genetically engineered or naturally existing virus that can selectively replicate in cancer cells and then kill them without damaging the healthy cells. There have been many kinds of oncolytic viruses, such as herpes simplex virus, adenovirus, and Coxsackievirus. Moreover, they have different clinical applications in cancer treatment. This review focused on the clinical application of oncolytic virus and predicted the prospect by analyzing the advantages and disadvantages of oncolytic virotherapy.