Optimizing environmental safety and cell-killing potential of oncolytic Newcastle Disease virus with modifications of the V, F and HN genes.

Newcastle Disease Virus (NDV) is an avian RNA virus, which was shown to be effective and safe for use in oncolytic viral therapy for several tumour malignancies. The presence of a multi basic cleavage site (MBCS) in the fusion protein improved its oncolytic efficacy in vitro and in vivo. However, NDV with a MBCS can be virulent in poultry. We aimed to develop an NDV with a MBCS but with reduced virulence for poultry while remaining effective in killing human tumour cells. To this end, the open reading frame of the V protein, an avian specific type I interferon antagonist, was disrupted by introducing multiple mutations. NDV with a mutated V gene was attenuated in avian cells and chicken and duck eggs. Although this virus still killed tumour cells, the efficacy was reduced compared to the virulent NDV. Introduction of various mutations in the fusion (F) and hemagglutinin-neuraminidase (HN) genes slightly improved this efficacy. Taken together, these data demonstrated that NDV with a MBCS but with abrogation of the V protein ORF and mutations in the F and HN genes can be safe for evaluation in oncolytic viral therapy.

Specificity, Safety, Efficacy of EGFRvIII-Retargeted Oncolytic HSV for Xenotransplanted Human Glioblastoma.

Glioblastoma is a lethal primary brain tumor lacking effective therapy. The secluded onset site, combined with the infiltrative properties of this tumor, require novel targeted therapies. In this scenario, the use of oncolytic viruses retargeted to glioblastoma cells and able to spread across the tumor cells represent an intriguing treatment strategy. Here, we tested the specificity, safety and efficacy of R-613, the first oncolytic HSV fully retargeted to EGFRvIII, a variant of the epidermal growth factor receptor carrying a mutation typically found in glioblastoma. An early treatment with R-613 on orthotopically transplanted EGFRvIII-expressing human glioblastoma significantly increased the median survival time of mice. In this setting, the growth of human glioblastoma xenotransplants was monitored by a secreted luciferase reporter and showed that R-613 is able to substantially delay the development of the tumor masses. When administered as late treatment to a well-established glioblastomas, R-613 appeared to be less effective. Notably the uninfected tumor cells derived from the explanted tumor masses were still susceptible to R-613 infection ex vivo, thus suggesting that multiple treatments could enhance R-613 therapeutic efficacy, making R-613 a promising oncolytic HSV candidate for glioblastoma treatment.

Understanding and addressing barriers to successful adenovirus-based virotherapy for ovarian cancer.

Ovarian cancer is the leading cause of death among women with gynecological cancer, with an overall 5-year survival rate below 50% due to a lack of specific symptoms, late stage at time of diagnosis and a high rate of recurrence after standard therapy. A better understanding of heterogeneity, genetic mutations, biological behavior and immunosuppression in the tumor microenvironment have allowed the development of more effective therapies based on anti-angiogenic treatments, PARP and immune checkpoint inhibitors, adoptive cell therapies and oncolytic vectors. Oncolytic adenoviruses are commonly used platforms in cancer gene therapy that selectively replicate in tumor cells and at the same time are able to stimulate the immune system. In addition, they can be genetically modified to enhance their potency and overcome physical and immunological barriers. In this review we highlight the challenges of adenovirus-based oncolytic therapies targeting ovarian cancer and outline recent advances to improve their potential in combination with immunotherapies.

Viruses of protozoan parasites and viral therapy: Is the time now right?

Infections caused by protozoan parasites burden the world with huge costs in terms of human and animal health. Most parasitic diseases caused by protozoans are neglected, particularly those associated with poverty and tropical countries, but the paucity of drug treatments and vaccines combined with increasing problems of drug resistance are becoming major concerns for their control and eradication. In this climate, the discovery/repurposing of new drugs and increasing effort in vaccine development should be supplemented with an exploration of new alternative/synergic treatment strategies. Viruses, either native or engineered, have been employed successfully as highly effective and selective therapeutic approaches to treat cancer (oncolytic viruses) and antibiotic-resistant bacterial diseases (phage therapy). Increasing evidence is accumulating that many protozoan, but also helminth, parasites harbour a range of different classes of viruses that are mostly absent from humans. Although some of these viruses appear to have no effect on their parasite hosts, others either have a clear direct negative impact on the parasite or may, in fact, contribute to the virulence of parasites for humans. This review will focus mainly on the viruses identified in protozoan parasites that are of medical importance. Inspired and informed by the experience gained from the application of oncolytic virus- and phage-therapy, rationally-driven strategies to employ these viruses successfully against parasitic diseases will be presented and discussed in the light of the current knowledge of the virus biology and the complex interplay between the viruses, the parasite hosts and the human host. We also highlight knowledge gaps that should be addressed to advance the potential of virotherapy against parasitic diseases.

An Update on the Role of Talimogene Laherparepvec (T-VEC) in the Treatment of Melanoma: Best Practices and Future Directions.

Talimogene laherparepvec (T-VEC) is the first agent approved for cancer in the emerging class of oncolytic viral therapies. While T-VEC was approved for the treatment of advanced melanoma in 2015, clinical utilization has been hampered by rapid changes in the therapeutic landscape of melanoma related to advances in both immune checkpoint blockade and targeted therapy, cumbersome logistics involved in T-VEC administration, biosafety concerns, and a perception that T-VEC has limited impact on uninjected, visceral disease. However, with further survival follow-up from the phase III OPTiM (OncovexGM-CSF Pivotal Trial in Melanoma), along with new real-world data and consensus guidelines on safe administration of oncolytic viruses, a roadmap for when and how to use T-VEC has been emerging. In addition, preliminary data have demonstrated improved therapeutic responses to T-VEC in combination with immune checkpoint blockade in patients with melanoma without additive toxicity. This review provides an update on recent data with T-VEC alone and in combination with other agents. The emerging data provide guidance for how to better utilize T-VEC for patients with melanoma and identifies critical areas for clinical investigation to expand the role of T-VEC in combination strategies for the treatment of melanoma and perhaps other cancers.

A Roadmap for the Success of Oncolytic Parvovirus-Based Anticancer Therapies.

Autonomous rodent protoparvoviruses (PVs) are promising anticancer agents due to their excellent safety profile, natural oncotropism, and oncosuppressive activities. Viral infection can trigger immunogenic cell death, activating the immune system against the tumor. However, the efficacy of this treatment in recent clinical trials is moderate compared with results seen in preclinical work. Various strategies have been employed to improve the anticancer activities of oncolytic PVs, including development of second-generation parvoviruses with enhanced oncolytic and immunostimulatory activities and rational combination of PVs with other therapies. Understanding the cellular factors involved in the PV life cycle is another important area of investigation. Indeed, these studies may lead to the identification of biomarkers that would allow a more personalized use of PV-based therapies. This review focuses on this work and the challenges that still need to be overcome to move PVs forward into clinical practice as an effective therapeutic option for cancer patients.

Immunomodulatory effects of ablation therapy on tumors: Potentials for combination with immunotherapy.

As a promising area of tumor treatment, immunotherapies, such as immune checkpoint inhibitors, have been applied to various types of cancer. However, many patients do not respond to such therapies. Increasing application of tumor ablation therapy, a minimally invasive treatment, has been observed in the clinic. Although it can boost the anti-tumor immune response of patients in many ways, ablation alone is not sufficient to remove the tumor completely or stop tumor recurrence in the long term. Currently, there is emerging research focusing on ablation in combination with immunotherapy, aiming to confirm the therapeutic value of this treatment for cancer patients. Hence, in this article, we review the classification, guideline recommendations, and immunomodulatory effects of ablation therapy, as well as the pre-clinical and clinical research of this combination therapy.

Development of a Nursing Policy for the Administration of an Oncolytic Virus in the Outpatient Setting.

OBJECTIVE: To describe the development of a nursing policy for the administration of oncolytic viruses in therapeutic clinical trials and the unique challenges for infection control and nursing. DATA SOURCE: Journal articles, web-based resources, peer-reviewed literature. CONCLUSION: Early nursing involvement and inclusion of multidisciplinary hospital departments facilitated the creation of a nursing policy that maintained fidelity to the research protocol and minimized potential risk to nursing staff. A total of 18 doses of oncolytic viruses were administered with no inadvertent exposures to staff or other patients of the oncolytic virus. IMPLICATIONS FOR NURSING PRACTICE: Nursing should be involved at the initiation of a clinical trial to determine whether policies need to be created or changed to maintain the integrity of the research protocol while ensuring the safety of staff and patients.

The use of the NIS reporter gene for optimizing oncolytic virotherapy.

INTRODUCTION: Oncolytic viruses are experimental cancer therapies being translated to the clinic. They are unique in their ability to amplify within the body, therefore requiring careful monitoring of viral replication and biodistribution. Traditional monitoring strategies fail to recapitulate the dynamic nature of oncolytic virotherapy. Consequently, clinically relevant, noninvasive, high resolution strategies are needed to effectively track virotherapy in real time. AREAS COVERED: The expression of the sodium iodide symporter (NIS) reporter gene is tightly coupled to viral genome replication and mediates radioisotope concentration, allowing noninvasive molecular nuclear imaging of active viral infection with high resolution. This provides insight into replication kinetics, biodistribution, the impact of vector design, administration, and dosing on therapeutic outcomes, and highlights the heterogeneity of spatial distribution and temporal evolution of infection. NIS-mediated imaging in clinical trials confirms the feasibility of this technology to noninvasively and longitudinally observe oncolytic virus infection, replication, and distribution. EXPERT OPINION: NIS-mediated imaging provides detailed functional and molecular information on the evolution of oncolytic virus infection in living animals. The use of NIS reporter gene imaging has rapidly advanced to provide unparalleled insight into the spatial and temporal context of oncolytic infection which will be integral to optimization of oncolytic treatment strategies.

Bioavailability, biodistribution, and CNS toxicity of clinical-grade parvovirus H1 after intravenous and intracerebral injection in rats.

The autonomous parvovirus H1 (H1PV) is transmitted in rodent populations. The natural host is the rat, in which H1PV infection is pathogenic only in fetuses and newborns. H1PV infection of human cancer cells leads to strong oncolytic effects in preclinical models. In preparation for a clinical trial of H1PV injection in patients with malignant brain tumors, H1PV had to be prepared to Good Manufacturing Practice standards, including extensive toxicology testing in rats. Because the trial involves direct intracerebral injection of H1PV into the tumor and around the resection cavity, possible toxicity to CNS tissue had to be investigated. In addition, quantitative blood levels and the tissue distribution of H1PV after single intracerebral or intravenous injection were measured. Direct injection of H1PV into rat brain at 3 dose levels (maximum, 7.96 × 107 pfu) did not cause any macroscopic or histologic pathology. Furthermore, H1PV infection of the brain did not alter central or autonomous nervous system function. H1PV DNA was detected in almost all organs at 6 h, 48 h, and 14 d after intravenous and intracerebral injection, with the highest levels in liver and spleen. H1PV concentrations in most organs were similar after intravenous and intracerebral injection, indicating high permeability of the blood-brain barrier for this small virus. The current results demonstrate wide organ distribution of H1PV after intravenous or intracerebral injection, confirm that H1PV is nonpathogenic in adult rats even after direct injection into the brain, and form the basis for the ongoing ParvOryx01 clinical trial.

Biosafety of non-human therapeutic viruses in clinical gene therapy.

The concept of using viruses as oncolytic agents is not a new one. In an effort to improve the applicability of viral anti-cancer agents various non-human viruses are being evaluated preclinically and clinically. The application of replication- competent non-human viruses poses new potential hazards, i.e. those associated with the possible adaptation of the therapeutic viruses to the human hosts. Therefore it is essential to weigh the potential benefits for the patients against the risk for the patients, their close contacts, and the greater public. Many aspects of such assessment parallel with the risks and dilemmas associated with the use of live porcine cells, tissues and organs in a clinical xenotransplantation setting. In this review we will summarize the potential biological hazards and list the points that need to be considered in a formal biosafety risk evaluation. The risk evaluation should include the possible environmental aspects of the non-human viruses used, also in case the non-human viruses are not formally designated as genetically modified organisms.

Optimization and preclinical design of genetically engineered viruses for human oncolytic therapy.

INTRODUCTION: Oncolytic viruses (OVs) occupy a strategic niche in the dynamic era of biological and gene therapy of human cancers. However, the use of OVs is the subject of close scrutiny due to impediments such as the insufficiency of patient generalizations posed by heterogeneous tumor responses to treatment, inherent or potentially lethal viral pathogenicities, unanticipated host- or immune-related adverse effects, and the emergence of virus-resistant cancer cells. These challenges can be overcome by the design and development of more definitive (optimized, targeted, and individualized) cancer virotherapeutics. AREAS COVERED: The translation of current knowledge and recent innovations into rational treatment prospects hinges on an iterative loop of variables pertaining to genetically engineered viral oncolytic efficacy and safety profiles, mechanism-of-action data, potencies of synergistic oncolytic viral combinations with conventional tumor, immuno-, chemo-, and radiation treatment modalities, optimization of the probabilities of treatment successes in heterogeneous (virus-sensitive and -resistant) tumor cell populations by mathematical modeling, and lessons learned from preclinical studies and human clinical trials. EXPERT OPINION: In recent years, it has become increasingly clear that proof-of-principle is critical for the preclinical optimization of oncolytic viruses to target heterogeneous forms of cancer and to prioritize current concerns related to the efficacy and safety of oncolytic virotherapy.