Recombinant Newcastle Disease Virus Immunotherapy Drives Oncolytic Effects and Durable Systemic Antitumor Immunity.

A recombinant Newcastle Disease Virus (NDV), encoding either a human (NDVhuGM-CSF, MEDI5395) or murine (NDVmuGM-CSF) GM-CSF transgene, combined broad oncolytic activity with the ability to significantly modulate genes related to immune functionality in human tumor cells. Replication in murine tumor lines was significantly diminished relative to human tumor cells. Nonetheless, intratumoral injection of NDVmuGM-CSF conferred antitumor effects in three syngeneic models in vivo; with efficacy further augmented by concomitant treatment with anti-PD-1/PD-L1 or T-cell agonists. Ex vivo immune profiling, including T-cell receptor sequencing, revealed profound immune-contexture changes consistent with priming and potentiation of adaptive immunity and tumor microenvironment (TME) reprogramming toward an immune-permissive state. CRISPR modifications rendered CT26 tumors significantly more permissive to NDV replication, and in this setting, NDVmuGM-CSF confers immune-mediated effects in the noninjected tumor in vivo Taken together, the data support the thesis that MEDI5395 primes and augments cell-mediated antitumor immunity and has significant utility as a combination partner with other immunomodulatory cancer treatments.

Potential and clinical translation of oncolytic measles viruses.

INTRODUCTION: Oncolytic viruses represent a novel treatment modality that is unencumbered by the standard resistance mechanisms limiting the therapeutic efficacy of conventional antineoplastic agents. Attenuated engineered measles virus strains derived from the Edmonston vaccine lineage have undergone extensive preclinical evaluation with significant antitumor activity observed in a broad range of preclinical tumoral models. These have laid the foundation for several clinical trials in both solid and hematologic malignancies, which have demonstrated safety, biologic activity and the ability to elicit antitumor immune responses. Areas covered: This review examines the published preclinical data which supported the clinical translation of this therapeutic platform, reviews the available clinical trial data and expands on ongoing phase II testing. It also looks at approaches to optimize clinical applicability and offers future perspectives. Expert opinion: Reverse genetic engineering has allowed the generation of oncolytic MV strains retargeted to increase viral tumor specificity, or armed with therapeutic and immunomodulatory genes in order to enhance anti-tumor efficacy. Continuous efforts focusing on exploring methods to overcome resistance pathways and determining optimal combinatorial strategies will facilitate further development of this encouraging antitumor strategy.

Magnetic Resonance Imaging-Based Assessment of Gadolinium-Conjugated Diethylenetriamine Penta-Acetic Acid Test-Infusion in Detecting Dysfunction of Convection-Enhanced Delivery Catheters.

BACKGROUND: In a phase 1 trial conducted at our institute, convection-enhanced delivery (CED) was used to administrate the Delta-24-RGD adenovirus in patients with a recurrent glioblastoma multiforme. Infusion of the virus was preceded by a gadolinium-conjugated diethylenetriamine penta-acetic acid (Gd-DTPA) test-infusion. In the present study, we analyzed the results of Gd-DTPA test infusion through 50 catheters. METHODS: Thirteen adults with a recurrent glioblastoma multiforme were enrolled in a larger phase 1 multicenter, dose-finding study, in which a conditionally replication-competent adenovirus was administered by CED. Up to 4 infusion catheters per patient were placed intra- and/or peritumorally. Before infusion of the virus, a Gd-DTPA infusion was performed for 6 hours, directly followed by a MRI scan. The MRIs were evaluated for catheter position, Gd-DTPA distribution outcome, and contrast leakage. RESULTS: Leakage of Gd-DTPA into the cerebrospinal fluid was detected in 17 of the 50 catheters (34%). Sulcus crossing was the most frequent cause of leakage. In 8 cases, leakage could only be detected on the fluid-attenuated inversion recovery sequence. Nonleaking catheters showed a significantly larger Gd-DTPA distribution fraction (volume of distribution/volume of infusion) than leaking catheters (P = 0.009). A significantly lower volume of distribution/volume of infusion was observed in intratumoral catheters, compared with peritumoral catheters (P = 0.004). Gd-DTPA test infusion did not result in significant changes in Karnofsky Performance Score and Neurological Status. CONCLUSIONS: Pre-CED treatment infusion of Gd-DTPA is an adequate and safe method to identify dysfunctional catheters. The use of an optimized drug delivery catheter is necessary to reduce leakage and improve the efficacy of intracerebral drug infusion.

Doxycycline Inducible Melanogenic Vaccinia Virus as Theranostic Anti-Cancer Agent.

We reported earlier the diagnostic potential of a melanogenic vaccinia virus based system in magnetic resonance (MRI) and optoacoustic deep tissue imaging (MSOT). Since melanin overproduction lead to attenuated virus replication, we constructed a novel recombinant vaccinia virus strain (rVACV), GLV-1h462, which expressed the key enzyme of melanogenesis (tyrosinase) under the control of an inducible promoter-system. In this study melanin production was detected after exogenous addition of doxycycline in two different tumor xenograft mouse models. Furthermore, it was confirmed that this novel vaccinia virus strain still facilitated signal enhancement as detected by MRI and optoacoustic tomography. At the same time we demonstrated an enhanced oncolytic potential compared to the constitutively melanin synthesizing rVACV system.

Type III interferon attenuates a vesicular stomatitis virus-based vaccine vector.

UNLABELLED: Vesicular stomatitis virus (VSV) has been extensively studied as a vaccine vector and oncolytic agent. Nevertheless, safety concerns have limited its widespread use in humans. The type III lambda interferon (IFN-λ) family of cytokines shares common signaling pathways with the IFN-α/ß family and thus evokes similar antiviral activities. However, IFN-λ signals through a distinct receptor complex that is expressed in a cell type-specific manner, which restricts its activity to epithelial barriers, particularly those corresponding to the respiratory and gastrointestinal tracts. In this study, we determined how IFN-λ expression from recombinant VSV would influence vector replication, spread, and immunogenicity. We demonstrate that IFN-λ expression severely attenuates VSV in cell culture. In vivo, IFN-λ limits VSV replication in the mouse lung after intranasal administration and reduces virus spread to other organs. Despite this attenuation, however, the vector retains its capacity to induce protective CD8 T cell and antibody responses after a single immunization. These findings demonstrate a novel method of viral vector attenuation that could be used in both vaccine and oncolytic virus applications. IMPORTANCE: Viruses such as VSV that are used as vaccine vectors can induce protective T cell and antibody responses after a single dose. Additionally, IFN-λ is a potent antiviral agent that has certain advantages for clinical use compared to IFN-α/ß, such as fewer patient side effects. Here, we demonstrate that IFN-λ attenuates VSV replication and spread following intranasal virus delivery but does not reduce the ability of VSV to induce potent protective immune responses. These findings demonstrate that the type III IFN family may have widespread applicability for improving the safety and efficacy of viral vaccine and oncolytic vectors.

Cavitation-enhanced delivery of a replicating oncolytic adenovirus to tumors using focused ultrasound.

Oncolytic viruses (OV) and ultrasound-enhanced drug delivery are powerful novel technologies. OV selectively self-amplify and kill cancer cells but their clinical use has been restricted by limited delivery from the bloodstream into the tumor. Ultrasound has been previously exploited for targeted release of OV in vivo, but its use to induce cavitation, microbubble oscillations, for enhanced OV tumor extravasation and delivery has not been previously reported. By identifying and optimizing the underlying physical mechanism, this work demonstrates that focused ultrasound significantly enhances the delivery and biodistribution of systemically administered OV co-injected with microbubbles. Up to a fiftyfold increase in tumor transgene expression was achieved, without any observable tissue damage. Ultrasound exposure parameters were optimized as a function of tumor reperfusion time to sustain inertial cavitation, a type of microbubble activity, throughout the exposure. Passive detection of acoustic emissions during treatment confirmed inertial cavitation as the mechanism responsible for enhanced delivery and enabled real-time monitoring of successful viral delivery.

Vesicular stomatitis virus as an oncolytic agent against pancreatic ductal adenocarcinoma.

Vesicular stomatitis virus (VSV) is a promising oncolytic agent against a variety of cancers. However, it has never been tested in any pancreatic cancer model. Pancreatic ductal adenocarcinoma (PDA) is the most common and aggressive form of pancreatic cancer. In this study, the oncolytic potentials of several VSV variants were analyzed in a panel of 13 clinically relevant human PDA cell lines and compared to conditionally replicative adenoviruses (CRAds), Sendai virus and respiratory syncytial virus. VSV variants showed oncolytic abilities superior to those of other viruses, and some cell lines that exhibited resistance to other viruses were successfully killed by VSV. However, PDA cells were highly heterogeneous in their susceptibility to virus-induced oncolysis, and several cell lines were resistant to all tested viruses. Resistant cells showed low levels of very early VSV RNA synthesis, indicating possible defects at initial stages of infection. In addition, unlike permissive PDA cell lines, most of the resistant cell lines were able to both produce and respond to interferon, suggesting that intact type I interferon responses contributed to their resistance phenotype. Four cell lines that varied in their permissiveness to VSV-ΔM51 and CRAd dl1520 were tested in mice, and the in vivo results closely mimicked those in vitro. While our results demonstrate that VSV is a promising oncolytic agent against PDA, further studies are needed to better understand the molecular mechanisms of resistance of some PDAs to oncolytic virotherapy.

Equine herpesvirus type 1-mediated oncolysis of human glioblastoma multiforme cells.

The cytolytic animal virus equine herpesvirus type 1 (EHV-1) was evaluated for its oncolytic potential against five human glioblastoma cell lines. EHV-1 productively infected four of these cell lines, and the degree of infection was positively correlated with glioma cell death. No human major histocompatibility complex class 1 (MHC-I) was detected in the resistant glioma line, while infection of the susceptible glioma cell lines, which expressed human MHC-I, were blocked with antibody to MHC-I, indicating that human MHC-I acts as an EHV-1 entry receptor on glioma cells.

Δγ1134.5 herpes simplex viruses encoding human cytomegalovirus IRS1 or TRS1 induce interferon regulatory factor 3 phosphorylation and an interferon-stimulated gene response.

The chimeric herpes simplex viruses (HSV) are Δγ134.5 vectors encoding the human cytomegalovirus (HCMV) IRS1 or TRS1 genes. They are capable of late viral protein synthesis and are superior to Δγ134.5 HSVs in oncolytic activity. The interferon (IFN) response limits efficient HSV gene expression and replication. HCMV TRS1 and IRS1 restore one γ134.5 gene function: evasion of IFN-inducible protein kinase R, allowing late viral protein synthesis. Here we show that, unlike wild-type HSV, the chimeric HSV do not restore another γ134.5 function, the suppression of early IFN signaling mediated by IFN regulatory factor 3 (IRF3).

Oncolytic virus therapy using genetically engineered herpes simplex viruses.

Genetically engineered, conditionally replicating herpes simplex viruses type 1 (HSV-1) are promising therapeutic agents for cancer. They can replicate in situ, spread, and exhibit oncolytic activity via a direct cytocidal effect. In addition, oncolytic HSV-1 can transfer and express foreign genes in host cells. The phase I clinical study with G207, a double-mutated HSV-1, in recurrent malignant glioma patients has shown that oncolytic HSV-1 can be safely administered into human brains. The therapeutic benefits of oncolytic HSV-1 depend on the extent of both intratumoral viral replication and induction of host antitumor immune responses. We develop new-generation oncolytic HSV-1 by enhancing these properties while retaining the safety features. G47delta was created from G207 by introducing another genetic mutation. Compared with G207, G47delta showed 1) better stimulation of human antitumor immune cells, 2) better growth properties leading to higher virus yields and increased cytopathic effect in vitro, 3) better antitumor efficacy in both immuno-competent and -incompetent animals, and 4) preserved safety in the brain of HSV-1-sensitive mice. Preparation is under way for a clinical trial using G47delta in progressive glioblastoma patients. G47delta is also suited as a backbone vector for expressing foreign molecules. Using bacterial artificial chromosome and two DNA recombinases, we have created an "armed" oncolytic HSV-1 generation system that allows insertion of transgene(s) into the genome of G47delta in a rapid and accurate manner. We found that expression of immunostimulatory molecules can significantly enhance the antitumor efficacy of G47delta. Based on these advances, we anticipate that oncolytic virus therapy using oncolytic HSV-1 will soon be established as an important modality of cancer treatment.

Virotherapy with a type 2 herpes simplex virus-derived oncolytic virus induces potent antitumor immunity against neuroblastoma.

PURPOSE: We recently constructed an oncolytic virus from type 2 herpes simplex virus (HSV-2) that selectively targets and kills tumor cells with an activated Ras signaling pathway. Designated FusOn-H2, this virus has shown several discrete killing mechanisms. Here, we evaluated the antitumor immune responses after FusOn-H2-mediated virotherapy in a syngeneic murine neuroblastoma model. EXPERIMENTAL DESIGN: We directly injected FusOn-H2 into established tumors and then measured its antitumor effect and the accompanying tumor-specific immune responses. Several oncolytic HSVs constructed from HSV-1 were included in the same experiments for comparisons. RESULTS: Our data show that tumor destruction by FusOn-H2 in vivo induces potent antitumor immune responses in this syngeneic neuroblastoma model. The elicited cellular immunity not only eradicated neuroblastoma cells in vitro but also inhibited the growth of tumors at sites distant from the virus injection site. Moreover, adoptive transfer of splenocytes from mice receiving virotherapy to naïve mice resulted in a measurable antitumor effect. CONCLUSION: We conclude that the ability of FusOn-H2 to induce tumor-specific cellular immunity expands the oncolytic repertoire of this virus and increases the likelihood that its use in patients would produce significant therapeutic benefits.