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Concept: Oncolytic virus

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The field of oncolytic virus therapy, the use of live, replicating viruses for the treatment of cancer, has expanded rapidly over the past decade. Preclinical models have clearly demonstrated anticancer activity against a number of different cancer types. Several agents have entered clinical trials and promising results have led to late stage clinical development for some viruses. The early clinical trials have demonstrated that oncolytic viruses by themselves have potential to result in tumor regression. Engineering of viruses to express novel genes have also led to the use of these vectors as a novel form of gene therapy. As a result, interest in oncolytic virus therapy has gained traction. The following review will focus on the first wave of clinical translation of oncolytic virus therapy, what has been learned so far, and potential challenges ahead for advancing the field.

Concepts: DNA, Gene, Cancer, Oncology, Microbiology, Virus, Oncolytic virus, Viruses

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With the recent regulatory approval of Talimogene laherparepvec (T-VEC) for the treatment of advanced of melanoma in the United States, Europe and Australia, oncolytic virus immunotherapy has earned its place in the clinic. However, the adoption of T-VEC by the U.S. oncology community has been slow, and so far has been largely limited to specialized cancer centers. Limiting factors include the intratumoral route of administration, which is unfamiliar to medical oncologists, biosafety concerns related to the use of a live virus in the clinic, and the explosion of other therapeutic strategies now available for the treatment of advanced melanoma. Herein, we review the development of T-VEC, and suggest how it fits into the in the current clinical treatment paradigm, and provide pearls for drug preparation, administration, and monitoring of response to therapy.

Concepts: Medicine, Oncology, Microbiology, United States, Chemotherapy, Therapy, Oncolytic virus, Viruses

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Oncolytic virus (OV) therapy is an emerging anti-cancer approach that utilizes viruses to preferentially infect and kill cancer cells, while not harming healthy cells. Vesicular stomatitis virus (VSV) is a prototypic non-segmented, negative-strand RNA virus with inherent OV qualities. Antiviral responses induced by type I interferon pathways are believed to be impaired in most cancer cells, making them more susceptible to VSV than normal cells. Several other factors make VSV a promising OV candidate for clinical use, including its well-studied biology, a small, easily manipulated genome, relative independence of a receptor or cell cycle, cytoplasmic replication without risk of host-cell transformation, and lack of pre-existing immunity in humans. Moreover, various VSV-based recombinant viruses have been engineered via reverse genetics to improve oncoselectivity, safety, oncotoxicity and stimulation of tumour-specific immunity. Alternative delivery methods are also being studied to minimize premature immune clearance of VSV. OV treatment as a monotherapy is being explored, although many studies have employed VSV in combination with radiotherapy, chemotherapy or other OVs. Preclinical studies with various cancers have demonstrated that VSV is a promising OV; as a result, a human clinical trial using VSV is currently in progress.

Concepts: Immune system, DNA, Oncology, Microbiology, Virus, Chemotherapy, Oncolytic virus, Vesicular stomatitis virus

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Functional genomic screening has emerged as a powerful approach for understanding complex biological phenomena. Of the available tools, genome-wide RNA interference (RNAi) technology is unquestionably the most incisive, as it directly probes gene function. Recent applications of RNAi screening have been impressive. Notable amongst these are its use in elucidated mechanism(s) for signal transduction, various aspects of cell biology, tumourigenesis and metastasis, resistance to cancer therapeutics, and the host’s response to a pathogen. Herein we discuss how recent RNAi screening efforts have helped turn our attention to the targetability of non-oncogene support pathways for cancer treatment, with a particular focus on a recent study that identified a non-oncogene addiction to the ER stress response as a synergist target for oncolytic virus therapy (OVT). Moreover, we give our thoughts on the future of RNAi screening as a tool to enhance OVT and describe recent technical improvements that are poised to make genome-scale RNAi experiments more sensitive, less noisy, more applicable in vivo, and more easily validated in clinically relevant animal models.British Journal of Cancer advance online publication, 20 November 2012; doi:10.1038/bjc.2012.467www.bjcancer.com.

Concepts: Gene, Oncology, Molecular biology, Biology, Microbiology, Virus, RNA interference, Oncolytic virus

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Second mitochondrial activator of caspase (Smac)-mimetic compounds and oncolytic viruses were developed to kill cancer cells directly. However, Smac-mimetic compound and oncolytic virus therapies also modulate host immune responses in ways we hypothesized would complement one another in promoting anticancer T-cell immunity. We show that Smac-mimetic compound and oncolytic virus therapies synergize in driving CD8(+) T-cell responses toward tumors through distinct activities. Smac-mimetic compound treatment with LCL161 reinvigorates exhausted CD8(+) T cells within immunosuppressed tumors by targeting tumor-associated macrophages for M1-like polarization. Oncolytic virus treatment with vesicular stomatitis virus (VSV(ΔM51)) promotes CD8(+) T-cell accumulation within tumors and CD8(+) T-cell activation within the tumor-draining lymph node. When combined, LCL161 and VSV(ΔM51) therapy engenders CD8(+) T-cell-mediated tumor control in several aggressive mouse models of cancer. Smac-mimetic compound and oncolytic virus therapies are both in clinical development and their combination therapy represents a promising approach for promoting anticancer T-cell immunity.Oncolytic viruses (OV) and second mitochondrial activator of caspase (Smac)-mimetic compounds (SMC) synergistically kill cancer cells directly. Here, the authors show that SMC and OV therapies combination also synergize in vivo by promoting anticancer immunity through an increase in CD8(+) T-cell response.

Concepts: Immune system, Cancer, Oncology, Microbiology, T helper cell, Oncolytic virus, Viruses, Vesicular stomatitis virus

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Purpose We evaluated the combination of talimogene laherparepvec plus ipilimumab versus ipilimumab alone in patients with advanced melanoma in a phase II study. To our knowledge, this was the first randomized trial to evaluate addition of an oncolytic virus to a checkpoint inhibitor. Methods Patients with unresectable stages IIIB to IV melanoma, with no more than one prior therapy if BRAF wild-type, no more than two prior therapies if BRAF mutant, measurable/injectable disease, and without symptomatic autoimmunity or clinically significant immunosuppression were randomly assigned 1:1 to receive talimogene laherparepvec plus ipilimumab or ipilimumab alone. Talimogene laherparepvec treatment began in week 1 (first dose, ≤ 4 mL × 10(6) plaque-forming units/mL; after 3 weeks, ≤ 4 mL × 10(8) plaque-forming units/mL every 2 weeks). Ipilimumab (3 mg/kg every 3 weeks; up to four doses) began week 1 in the ipilimumab alone arm and week 6 in the combination arm. The primary end point was objective response rate evaluated by investigators per immune-related response criteria. Results One hundred ninety-eight patients were randomly assigned to talimogene laherparepvec plus ipilimumab (n = 98), or ipilimumab alone( n = 100). Thirty-eight patients (39%) in the combination arm and 18 patients (18%) in the ipilimumab arm had an objective response (odds ratio, 2.9; 95% CI, 1.5 to 5.5; P = .002). Responses were not limited to injected lesions; visceral lesion decreases were observed in 52% of patients in the combination arm and 23% of patients in the ipilimumab arm. Frequently occurring adverse events (AEs) included fatigue (combination, 59%; ipilimumab alone, 42%), chills (combination, 53%; ipilimumab alone, 3%), and diarrhea (combination, 42%; ipilimumab alone, 35%). Incidence of grade ≥ 3 AEs was 45% and 35%, respectively. Three patients in the combination arm had fatal AEs; none were treatment related. Conclusion The study met its primary end point; the objective response rate was significantly higher with talimogene laherparepvec plus ipilimumab versus ipilimumab alone. These data indicate that the combination has greater antitumor activity without additional safety concerns versus ipilimumab.

Concepts: Epidemiology, Clinical trial, Randomized controlled trial, Chemotherapy, Dose, Randomness, Oncolytic virus, Ablative brain surgery

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Oncolytic virotherapy is rapidly progressing through clinical evaluation. However, the therapeutic efficacy of oncolytic viruses in humans has been less than expected from preclinical studies. We describe an anticancer drug screen for compounds that enhance M1 oncolytic virus activity in hepatocellular carcinoma (HCC). An inhibitor of the valosin-containing protein (VCP) was identified as the top sensitizer, selectively increasing potency of the oncolytic virus up to 3600-fold. Further investigation revealed that VCP inhibitors cooperated with M1 virus-suppressed inositol-requiring enzyme 1α (IRE1α)-X-box binding protein 1 (XBP1) pathway and triggered irresolvable endoplasmic reticulum (ER) stress, subsequently promoting robust apoptosis in HCC. We show that VCP inhibitor improved the oncolytic efficacy of M1 virus in several mouse models of HCC and primary HCC tissues. Finally, this combinatorial therapeutic strategy was well tolerated in nonhuman primates. Our study identifies combined VCP inhibition and oncolytic virus as a potential treatment for HCC and demonstrates promising therapeutic potential.

Concepts: Protein, Oncology, Microbiology, Virus, Endoplasmic reticulum, Oncolytic virus, Viruses, Vesicular stomatitis virus

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Combining immunotherapeutic agents with different mechanisms of action may enhance efficacy. We describe the safety and efficacy of talimogene laherparepvec (T-VEC; an oncolytic virus) in combination with ipilimumab (a cytotoxic T-lymphocyte-associated antigen 4 checkpoint inhibitor) in patients with advanced melanoma.

Concepts: Microbiology, Interferon, Cytotoxic T cell, Oncolytic virus, Viruses

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Isolated Limb Perfusion (ILP) is a treatment for advanced extremity sarcoma and in-transit melanoma. Advancing this procedure by investigating the addition of novel agents, such as cancer-selective oncolytic viruses, may improve both the therapeutic efficacy of ILP and the tumour-targeted delivery of oncolytic virotherapy. Standard in vitro assays were used to characterise single agent and combinatorial activities of melphalan, tumour necrosis factor-alpha (TNF-α) and Lister strain vaccinia virus (GLV-1h68) against BN175 rat sarcoma cells. An orthotopic model of advanced extremity sarcoma was used to evaluate survival of animals after ILP with combinations of TNF-α, melphalan and GLV-1h68. We investigated the efficiency of viral tumour delivery by ILP compared to intravenous therapy, the locoregional and systemic biodistribution of virus after ILP, and the effect of mode of administration on antibody response. The combination of melphalan and GLV-1h68 was synergistic in vitro. The addition of virus to standard ILP regimens was well tolerated and demonstrated superior tumour targeting compared to intravenous administration. Triple therapy (melphalan/TNF-α/GLV-1h68) resulted in increased tumour growth delay and enhanced survival compared to other treatment regimens. Live virus was recovered in large amounts from perfused regions, but in smaller amounts from systemic organs. The addition of oncolytic vaccinia virus to existing TNF-α/melphalan-based ILP strategies results in survival advantage in an immunocompetent rat model of advanced extremity sarcoma. Virus administered by ILP has superior tumour targeting compared to intravenous delivery. Further evaluation and clinical translation of this approach is warranted. © 2014 Wiley Periodicals, Inc.

Concepts: Oncology, Microbiology, Virus, Chemotherapy, Intravenous therapy, Oncolytic virus, Viruses, Vaccinia

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Oncolytic viruses (OVs) comprise a versatile and multi-mechanistic therapeutic platform in the growing arsenal of anticancer biologics. These replicating therapeutics find favorable conditions in the tumor niche, characterized among others by increased metabolism, reduced anti-tumor/antiviral immunity, and disorganized vasculature. Through a self-amplification that is dependent on multiple cancer-specific defects, these agents exhibit remarkable tumor selectivity. With several OVs completing or entering Phase III clinical evaluation, their therapeutic potential as well as the challenges ahead are increasingly clear. One key hurdle is tumor heterogeneity, which results in variations in the ability of tumors to support productive infection by OVs and to induce adaptive anti-tumor immunity. To this end, mounting evidence suggests tumor epigenetics may play a key role. This review will focus on the epigenetic landscape of tumors and how it relates to OV infection. Therapeutic strategies aiming to exploit the epigenetic identity of tumors in order to improve OV therapy are also discussed.

Concepts: Immune system, Cancer, Oncology, Microbiology, Virus, Therapy, Oncolytic virus, Viruses