Oncolytic Herpes Simplex Research Articles

Construction of a stable 4T1 cell line expressing UL19 by the PiggyBac transposon system

To investigate the mechanism of the major capsid protein VP5 (encoded by the UL19 gene) of oncolytic herpes simplex virus type Ⅱ (oHSV2) in regulating the antitumor function of immune cells, we constructed a mouse breast cancer cell line 4T1-iRFP-VP5-GFP stably expressing VP5 protein, near-infrared fluorescent protein (iRFP), and green fluorescent protein (GFP) by using the PiggyBac transposon system. Flow cytometry and Western blotting were employed to screen the monoclonal cell lines expressing both GFP and VP5 and examine the expression stability of UL19 in the constructed cell line. The results of SYBR Green I real-time PCR and Western blotting showed that the copies of UL19 and the expression level of VP5 protein in the 15th passage of 4T1-iRFP-VP5-GFP cells were significantly higher than those in the 4T1 cells transiently transfected with UL19, demonstrating the stable insertion of UL19 into the 4T1 cell genome. The real-time cell analysis (RTCA) was employed to monitor the proliferation of 4T1-iRFP-VP5-GFP cells, which showed similar proliferation activity to their parental 4T1 cells. Further studies confirmed that NK92 cells exhibited stronger cytotoxicity against 4T1-iRFP-VP5-GFP cells than against 4T1 cells. This study layed a foundation for elucidating the role of VP5 protein in regulating immune cells, including T cells and NK cells, via HLA-E in 4T1 cells to exert the anti-tumor function.

DDDR-37. OHSV AND RADIATION THERAPIES SENSITIZE GLIOBLASTOMA TO IGF1R-TARGETED THERAPY AND SYNERGIZE IN TRIPLE COMBINATION THERAPY

Abstract Glioblastoma (GBM) continues to have a dismal prognosis despite remarkable advances in the field due to both tumor-intrinsic factors (i.e., IDH1 or EGFRvIII mutations) and extrinsic factors (i.e., relating to the tumor microenvironment (TME)), necessitating therapeutic innovation. Oncolytic herpes simplex virus-1 (oHSV) is an FDA-approved therapy that has shown promising results in clinical trials; however, therapeutic efficacy is limited to a small subset of patients. Thus, elucidating both the tumor-TME interplay and feedback/feedforward tumor-cell signaling in the context of viro-immunotherapy is essential in augmenting therapeutic outcomes. We recently discovered a novel mechanism of resistance to oHSVs, in which infection increases secretion of Insulin-like growth factor 2 (IGF2), activating the Insulin-like Growth Factor-1 Receptor (IGF1R). Upregulation of the IGF1R signaling pathway in GBM is correlated with poor prognosis and has been implicated in resistance to conventional therapies including radiotherapy (RTx). Herein, we further elucidate the impact of oHSVs on IGF1R activation, demonstrating a dose-dependent enhancement of downstream signaling. While IGF1R targeting therapies (e.g., OSI-966, Picropodophyllin (PPP)) have displayed limited efficacy in clinical trials, they significantly increased oHSV-induced cytotoxicity in all tested primary GBM cells compared to either agent alone in vitro and in vivo, resulting in a dose-dependent increase in PARP and caspase 3 activity by western blot and immunohistochemistry. We further found that RTx-induced IGF1 secretion and subsequent IGF1R activation were enhanced when combined with oHSV treatment. Triple combination therapy with oHSV, IGF1R inhibition, and RTx significantly increased tumor cell killing in vitro and improved survival of orthotopic GBM tumor-bearing mice. Collectively, our study provides preclinical evidence of enhanced therapeutic efficacy of oHSVs and RTx in combination with IGF1R blockade, supporting future use of IGF1R inhibitors in combination with the standard of care and FDA-approved oHSV therapies in patients with GBM.

TMIC-61. DEVELOPMENT OF A NOVEL NOTCH-TARGETING ONCOLYTIC HSV FOR GBM TUMORS

Abstract Glioblastoma (GBM) is the most aggressive brain malignancy, which despite continuing worldwide efforts to develop new therapies, remains a deadly disease with limited treatment options. The NOTCH signaling pathway is often hyperactive in GBM tumors, and its activity contributes to tumor progression and resistance to treatment. The role of NOTCH signaling in tumor growth and resistance is well studied, but the significance of this pathway for immunotherapy of GBM is not very well understood. We have recently shown that NOTCH activation following virotherapy contributes to tumor regrowth and induces recruitment of monocytic MDSC cells into the tumor, which limit optimal immune activation to kill tumor cells. For this study, we have discovered a NOTCH interfering intracellular ligand (NIIL) that blocks NOTCH activation from inside glioma cells. RNA sequencing shows the expression of NIIL downregulates NOTCH signaling in vitro. To evaluate the effect of NIIL on virotherapy, we generated an oncolytic herpes simplex virus (oHSV) that also encodes for NIIL. This virus showed a slower spread in vitro but improved therapeutic efficacy in vivo in multiple models of intracranial tumors. In immune competent mice there was a significant improvement in the survival of mice treated with the NIIL-encoding virus, with a fraction of mice showing a complete response after a single treatment. Single-cell RNA sequencing analysis of immune infiltrates is ongoing to understand how NIIL impacts tumor microenvironment and anti-tumor immune therapy.

EXTH-75. IMMUNOVIROTHERAPY WITH PP2A AND PD-1 INHIBITION IN PEDIATRIC HIGH-GRADE GLIOMA

Abstract Pediatric high-grade gliomas (HGGs) represent a significant clinical challenge with poor survival rates. Engineered oncolytic herpes simplex virus (oHSV) has shown potential in several clinical trials at targeting HGGs through their direct lytic effect and induction of an immune response. We have learned from our clinical trial experience (NCT02457845) that a critical barrier to more durable response is augmenting and sustaining the anti-tumor immune response generated by oHSV. LB-100, a protein phosphatase 2A (PP2A) inhibitor, is known to enhance T-cell activity. We hypothesized that LB-100 with anti-PD-1 therapy would overcome the immunosuppressive barriers, enhancing the immunotherapeutic effects of oHSV and improve survival in an immunocompetent murine model. We investigated the therapeutic impact of clinically available, next-generation oHSV, M002, which expresses murine interleukin-12, combined with LB-100 and PD-1 inhibition compared to M002 with LB-100 or anti-PD-1 antibody, each therapy alone, or control by measuring median survival and changes in the tumor immune microenvironment. The triple combination of M002, LB-100, and anti-PD-1 antibody significantly extended median survival compared to control (45 days vs 22.5 days, P=0.001) or each treatment alone, and compared to M002 and LB-100 (44 days vs 28 days, P=0.017) or M002 and anti-PD-1 (45.5 days vs 41 days, P=0.023). This increase in survival was correlated with a robust increase in CD45+ immune cell infiltration and a reduction in T-regulatory cells. We will further investigate the changes in the tumor microenvironment to better understand the specific contributions of different immune cell populations. These data support the hypothesis that LB-100 enhances the efficacy of oHSV by amplifying T-cell-mediated immune responses against tumor cells. This combination therapy demonstrates a promising strategy that warrants further exploration and potential clinical application, emphasizing the critical role of targeting multiple aspects of immune regulation to enhance the efficacy of oncolytic virotherapy in pediatric tumors.

The anti-tumor efficacy of a recombinant oncolytic herpes simplex virus mediated CRISPR/Cas9 delivery targeting in HPV16-positive cervical cancer

Cervical cancer, often driven by high-risk human papillomavirus (HPV) infections such as HPV16 or HPV18, remains a leading cause of cancer-related deaths. HPV16, found in about 90% of cervical cancer patients, harbors key oncogenic related genes (E6, E7, E2, E5) and an upstream regulatory region (URR) that contribute to cancer progression. This study introduces a novel approach using a recombinant oncolytic herpes simplex virus type 1 (HSV-1) named SONC103, armed with a CRISPR/Cas9 gene editing system. The aim was to target and disrupt integrated HPV16 genes in cervical cancer cells. Results demonstrated SONC103's capability to specifically and effectively knock down HPV16 oncogenes, thereby reducing cell proliferation and promoting apoptosis. Analyses further revealed loss of HPV16 DNA probes in infected cells' chromosomes, significant regulation of cellular processes related to tumor apoptosis, and downregulation of E6/E7 oncoproteins while increasing tumor suppressor proteins P53 and pRB. Notably, SONC103 exhibited substantial inhibition of tumor growth in a murine xenograft cervical cancer model. This study showcases the potential of the recombinant oncolytic HSV-1 virus (SONC103) in combating HPV16-positive cervical cancer by targeting oncogenes and facilitating oncolysis.

Improved antitumor effectiveness of oncolytic HSV-1 viruses engineered with IL-15/IL-15Rα complex combined with oncolytic HSV-1-aPD1 targets colon cancer

Oncolytic virotherapy is emerging as a promising therapeutic avenue for cancer treatment, harnessing both innate and tumor-specific immune responses for targeted tumor elimination. In this study, we present a novel oncolytic virus (oHSV1-IL15B) derived from herpes simplex virus-1 (HSV-1), armed with IL-15/IL-15Rα complex, with a focus on treating colon cancer combined with oncolytic HSV-1 expressing anti-PD-1 antibody (oHSV1-aPD1). Results from our study reveal that recombinant oHSV-1 virus equipped with IL-15/IL-15Rα complex exhibited significant anti-tumor effects in a murine CT26 colon adenocarcinoma model. Notably, oHSV1-IL15B combined with oHSV-1-aPD1 demonstrates superior tumor inhibition and prolonged overall survival compared to oHSV1-mock and monotherapy groups. Further exploration highlights the impact of oHSV1-IL15B, oHSV-1-aPD1 and combined group on antitumor capacity, revealing a substantial increase in CD8+ T and CD4+ T cell proportions of CT26-bearing BALB/c mice and promoting apoptosis in tumor tissue. The study emphasizes the pivotal role of cytotoxic CD8+T cells in oncolytic virotherapy, demonstrating that recombinant oHSV1-IL15B combined with oncolytic HSV-1-aPD1 induces a robust tumor-specific T cell response. RNA sequence analysis highlighted oHSV1-IL15B combined with oHSV1-aPD1 improved tumors immune microenvironment on immune response, antiviral response-related genes and apoptosis-related genes, which contributed to anti-tumor immunotherapy. The findings underscore the promising antitumor activity achieved through the combination of IL-15/IL-15Rα complex and anti-PD-1 antibody with oHSV-1. This research opens avenues for diverse therapeutic strategies, suggesting the potential of synergistically utilizing cytokines and anti-PD-1 antibody with oncolytic viruses to enhance immunotherapy for cancer management.

An oncolytic HSV-1 vector induces a therapeutic adaptive immune response against glioblastoma

BackgroundGlioblastoma (GBM) is the most frequent and aggressive brain tumor in adults with the lowest survival rates five years post-diagnosis. Oncolytic viruses (OVs) selectively target and damage cancer cells, and for this reason they are being investigated as new therapeutic tools also against GBM.MethodsAn oncolytic herpes simplex virus type 1 (oHSV-1) with deletions in the γ34.5 neurovirulence gene and the US12 gene, expressing enhanced green fluorescent protein (EGFP-oHSV-1) as reporter gene was generated and tested for its capacity to infect and kill the murine GL261 glioblastoma (GBM) cell line. Syngeneic mice were orthotopically injected with GL261cells. Seven days post-implantation, EGFP-oHSV-1 was administered intratumorally. Twenty-one days after parental tumor challenge in the opposite brain hemisphere, mice were sacrified and their brains were analysed by immunohistochemistry to assess tumor presence and cell infiltrate.ResultsoHSV-1 replicates and induces cell death of GL261 cells in vitro. A single intracranial injection of EGFP-oHSV-1 in established GL261 tumors significantly prolongs survival in all treated mice compared to placebo treatment. Notably, 45% of treated mice became long-term survivors, and rejected GL261 cells upon rechallenge in the contralateral brain hemisphere, indicating an anamnestic antitumoral immune response. Post-mortem analysis revealed a profound modification of the tumor microenvironment with increased infiltration of CD4 + and CD8 + T lymphocytes, intertumoral vascular collapse and activation and redistribution of macrophage, microglia, and astroglia in the tumor area, with the formation of intense fibrotic tissue suggestive of complete rejection in long-term survivor mice.ConclusionsEGFP-oHSV1 demonstrates potent antitumoral activity in an immunocompetent GBM model as a monotherapy, resulting from direct cell killing combined with the stimulation of a protective adaptive immune response. These results open the way to possible application of our strategy in clinical setting.

Oncolytic virotherapy augments self-maintaining natural killer cell line cytotoxicity against neuroblastoma

BackgroundNeuroblastoma is the most common extracranial solid tumor in children and accounts for 15% of pediatric cancer related deaths. Targeting neuroblastoma with immunotherapies has proven challenging due to a paucity of immune cells in the tumor microenvironment and the release of immunosuppressive cytokines by neuroblastoma tumor cells. We hypothesized that combining an oncolytic Herpes Simplex Virus (oHSV) with natural killer (NK) cells might overcome these barriers and incite tumor cell death.MethodsWe utilized MYCN amplified and non-amplified neuroblastoma cell lines, the IL-12 expressing oHSV, M002, and the human NK cell line, NK-92 MI. We assessed the cytotoxicity of NK cells against neuroblastoma with and without M002 infection, the effects of M002 on NK cell priming, and the impact of M002 and priming on the migratory capacity and CD107a expression of NK cells. To test clinical applicability, we then investigated the effects of M002 and NK cells on neuroblastoma in vivo.ResultsNK cells were more attracted to neuroblastoma cells that were infected with M002. There was an increase in neuroblastoma cell death with the combination treatment of M002 and NK cells both in vitro and in vivo. Priming the NK cells enhanced their cytotoxicity, migratory capacity and CD107a expression.ConclusionsTo the best of our knowledge, these investigations are the first to demonstrate the effects of an oncolytic virus combined with self-maintaining NK cells in neuroblastoma and the priming effect of neuroblastoma on NK cells. The current studies provide a deeper understanding of the relation between NK cells and neuroblastoma and these data suggest that oHSV increases NK cell cytotoxicity towards neuroblastoma.

Oncolytic herpes simplex virus propagates tertiary lymphoid structure formation via CXCL10/CXCR3 to boost antitumor immunity.

Inducing tertiary lymphoid structure (TLS) formation can fuel antitumor immunity. It is necessary to create mouse models containing TLS to explore strategies of TLS formation. Oncolytic herpes simplex virus-1 (oHSV) exhibited intense effects in preclinical and clinical trials. However, the role of oHSV in TLS formation remains to be elucidated. Here, we observed the presence of TLS in 4MOSC1 and MC38 subcutaneous tumour models. Interestingly, oHSV evoked TLS formation, and increased infiltration of B cells and stem-like TCF1+CD8+ T cells proliferation. Mechanistically, oHSV increased the expression of TLS-related chemokines, along with upregulated CXCL10/CXCR3 to facilitate TLS formation. Notably, CXCL10 and CXCR3 were favourable prognostic factors for cancer patients, and closely related with immune cells infiltration. Inhibiting CXCL10/CXCR3 reduced TCF1+CD8+ T cells and granzyme B expression, and impaired oHSV-mediated TLS formation. Furthermore, oHSV-mediated TLS formation revealed superior response and survival rate when combined with αPD-1 treatment. Collectively, these findings indicate that oHSV recruits stem-like TCF1+CD8+ T cells through CXCL10/CXCR3 pathway to propagate TLS formation, and warrants future antitumor immunity development.

658P First-in-human phase I trial of oncolytic herpes simplex virus ONCR-177 alone or in combination with pembrolizumab in advanced solid tumors

658P First-in-human phase I trial of oncolytic herpes simplex virus ONCR-177 alone or in combination with pembrolizumab in advanced solid tumors

Advances in antitumour therapy with oncolytic herpes simplex virus combinations.

Oncolytic Virus (OVs) is an emerging approach to tumour immunity that allows the use of natural or genetically modified viruses to specifically infect and lyse tumour cells without damaging normal cells. Oncolytic herpes simplex virus (oHSV) is one of the more widely researched and applied OVs in the field of oncology, which can directly kill tumour cells to promote anti-tumour immune responses. oHSV is one of the few viruses with good antiviral drugs, so oHSV is also more clinically safe. In recent years, in addition to monotherapy of oHSV in tumours, more and more studies have been devoted to exploring the anti-tumour effects of oHSV in combination with other therapeutic approaches. In this article we describe the progress of oHSV combination therapy against tumours in the nervous system, digestive system, reproductive system and other systems.

Dual-Responsive Epigenetic Inhibitor Nanoprodrug Combined with Oncolytic Virus Synergistically Boost Cancer Immunotherapy by Igniting Gasdermin E-Mediated Pyroptosis.

Cancer immunotherapy has emerged as a promising approach for the treatment of various cancers. However, the immunosuppressive tumor microenvironment (TME) limits the efficacy of current immunotherapies. In this study, we designed a dual-responsive DNA methyltransferase inhibitor nanoprodrug ACNPs for combination therapy with oncolytic herpes simplex virus (oHSV). We found that the epigenetic inhibitor 5-Azacytidine (5-Aza) upregulated gasdermin E (GSDME) expression at the gene level, whereas the oHSV decreased the ubiquitination and degradation of GSDME to elevate its levels. Based on these observations, we further discovered that ACNPs and oHSV synergistically enhanced GSDME-mediated pyroptosis. Additionally, the combination therapy of ACNPs and oHSV effectively inhibited tumor growth, remodeled the immunosuppressive TME, and improved the efficacy of immune checkpoint blockade (ICB) therapy. These results demonstrate the potential to overcome immunosuppression through synergistic combinations, offering a promising approach for cancer immunotherapy.

Myelomodulatory treatments augment the therapeutic benefit of oncolytic viroimmunotherapy in murine models of malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNST) pose a significant therapeutic challenge due to high recurrence rates after surgical resection and a largely ineffective response to traditional chemotherapy. An alternative treatment strategy is oncolytic viroimmunotherapy, which can elicit a durable and systemic antitumor immune response and is Food and Drug Administration (FDA)-approved for the treatment of melanoma. Unfortunately, only a subset of patients responds completely, underscoring the need to address barriers hindering viroimmunotherapy effectiveness. Here we investigated the therapeutic utility of targeting key components of the MPNST immunosuppressive microenvironment to enhance viroimmunotherapy's antitumor efficacy in three murine models, one of which showed more immunogenic characteristics than the others. Myelomodulatory therapy with pexidartinib, a small molecule inhibitor of CSF1R tyrosine kinase, and the oncolytic herpes simplex virus T-VEC exhibited the most significant increase in median survival time in the highly immunogenic model. Additionally, targeting myeloid cells with the myelomodulatory therapy trabectedin, a small molecule activator of caspase-8 dependent apoptosis, augmented the survival benefit of T-VEC in a less immunogenic MPNST model. However, tumor regressions or shrinkages were not observed. Depletion experiments confirmed that the enhanced survival benefit relied on a T cell response. Furthermore, flow cytometry analysis following combination viroimmunotherapy revealed decreased M2 macrophages and myeloid-derived suppressor cells and increased tumor-specific gp70+ CD8 T cells within the tumor microenvironment. In summary, our findings provide compelling evidence for the potential to leverage viroimmunotherapy with myeloid cell targeting against MPNST and warrant further investigation.

Combination Immunotherapy with Vaccine and Oncolytic HSV Virotherapy Is Time Dependent.

Oncolytic virotherapy or immunovirotherapy is a strategy that utilizes viruses to selectively infect and kill tumor cells while also stimulating an immune response against the tumor. Early clinical trials in both pediatric and adult patients using oncolytic herpes simplex viruses (oHSV) have demonstrated safety and promising efficacy; however, combinatorial strategies designed to enhance oncolysis while also promoting durable T-cell responses for sustaining disease remission are likely required. We hypothesized that combining the direct tumor cell killing and innate immune stimulation by oHSV with a vaccine that promotes T cell-mediated immunity may lead to more durable tumor regression. To this end, we investigated the preclinical efficacy and potential synergy of combining oHSV with a self-assembling nanoparticle vaccine codelivering peptide antigens and Toll-like receptor 7 and 8 agonists (referred to as SNAPvax),which induces robust tumor-specific T-cell immunity. We then assessed how timing of the treatments (i.e., vaccine before or after oHSV) impacts T-cell responses, viral replication, and preclinical efficacy. The sequence of treatments was critical, as survival was significantly enhanced when the SNAPvax vaccine was given prior to oHSV. Increased clinical efficacy was associated with reduced tumor volume and increases in virus replication and tumor antigen-specific CD8+ T cells. These findings substantiate the criticality of combination immunotherapy timing and provide preclinical support for combining SNAPvax with oHSV as a promising treatment approach for both pediatric and adult tumors.

Enhanced treatment of breast cancer brain metastases with oncolytic virus expressing anti-CD47 antibody and temozolomide

Limited therapeutic options are available for patients with breast cancer brain metastases (BCBM), and thus there is an urgent need for novel treatment approaches. We previously engineered an effective oncolytic herpes simplex virus-1 (oHSV) expressing a full-length anti-CD47 monoclonal antibody (mAb) with a human IgG1 scaffold (OV-αCD47-G1) that was used to treat both ovarian cancer and glioblastoma. Here, we demonstrate that the combination of OV-αCD47-G1 and temozolomide (TMZ) improve outcomes in preclinical models of BCBM. The combination of TMZ with OV-αCD47-G1 synergistically increased macrophage phagocytosis against breast tumor cells and led to greater activation of NK cell cytotoxicity. Additionally, the combination of OV-αCD47-G1 with TMZ significantly prolonged the survival of tumor-bearing mice when compared to TMZ or OV-αCD47-G1 alone. Combination treatment with the mouse counterpart of OV-αCD47-G1, termed OV-A4-IgG2b, also enhanced mouse macrophage phagocytosis, NK cell cytotoxicity, and survival in an immunocompetent model of mice bearing BCBM compared to TMZ or OV-A4-IgG2b alone. Collectively, these results suggest that OV-αCD47-G1 combined with TMZ should be explored in patients with BCBM.

The Oncolytic virus VT1092M and an Anti-PD-L1 antibody synergize to induce systemic antitumor immunity in a murine bilateral tumor model

This study investigated the synergistic potential of an oncolytic herpes simplex virus armed with interleukin 12 (VT1092M) in combination with immune checkpoint inhibitors for enhancing antitumor responses. The potential of this combination treatment to induce systemic antitumor immunity was assessed using bilateral subcutaneous tumor and tumor re-challenge mouse models. The antitumor efficacy of various OV and ICI treatment combinations and the underlying mechanisms were explored through diverse analytical techniques, including flow cytometry and RNA sequencing. Using VT1092M, either alone or in combination with an anti-PD-L1 antibody, significantly reduced the sizes of both the injected and untreated abscopal tumors in a bilateral tumor mouse model. The combination therapy demonstrated superior antitumor efficacy to the other treatment conditions tested, which was accompanied by an increase in T cell numbers and CD8+T cell activation. Results from the survival and tumor re-challenge experiments showed that the combination therapy elicited long-term, tumor-specific immune responses, which were associated with tumor clearance and prolonged survival. Immune cell depletion assays identified CD8+T cells as the crucial mediators of systemic antitumor immunity during combination therapy. In conclusion, the combination of VT1092M and PD-L1 blockade emerged as a potent inducer of antitumor immune responses, surpassing the efficacy of each monotherapy. This synergistic approach holds promise for achieving robust and sustained antitumor immunity, with potential implications for preventing tumor metastasis in patients with cancer.

Enhanced IL-12 transgene expression improves oncolytic viroimmunotherapy.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas with unacceptably low cure rates occurring often in patients with neurofibromatosis 1 defects. To investigate oncolytic Herpes Simplex Virus (oHSV) as an immunotherapeutic approach, we compared viral replication, functional activity, and immune response between unarmed and interleukin 12 (IL-12)-armed oncolytic viruses in virus-permissive (B109) and -resistant (67C-4) murine MPNSTs. This study compared two attenuated IL-12-oHSVs with γ134.5 gene deletions (Δγ134.5) and the same transgene expression cassette. The primary difference in the IL-12-oHSVs was in their ability to counter the translational arrest response in infected cells. Unlike M002 (Δγ134.5, mIL-12), C002 (Δγ134.5, mIL-12, IRS1) expresses an HCMV IRS1 gene and evades dsRNA activated translational arrest in infected cells. Our results show that oHSV replication and gene expression results in vitro were not predictive of oHSV direct oncolytic activity in vivo. Tumors that supported viral replication in cell culture studies resisted viral replication by both oHSVs and restricted M002 transgene expression in vivo. Furthermore, two IL-12-oHSVs with equivalent transcriptional activity differed in IL-12 protein production in vivo, and the differences in IL-12 protein levels were reflected in immune infiltrate activity changes as well as tumor growth suppression differences between the IL-12-oHSVs. C002-treated tumors exhibited sustained IL-12 production with improved dendritic cells, monocyte-macrophage activity (MHCII, CD80/CD86 upregulation) and a polyfunctional Th1-cell response in the tumor infiltrates. These results suggest that transgene protein production differences between oHSVs in vivo, in addition to replication differences, can impact OV-therapeutic activity.

Effect of oncolytic herpes simplex virus on fusion-positive rhabdomyosarcoma to radiotherapy.

10063 Background: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Despite multimodal interventions including surgery, chemotherapy, and radiotherapy, nearly a third of patients with localized disease will experience tumor recurrence. Patients with tumors harboring an oncogenic FOXO1 fusion are at greater risk of relapse and are most in need of novel therapies. Oncolytic viruses are being explored as treatments for pediatric tumors, and data suggest that oncolytic viruses may enhance responses to chemoradiotherapy. M002 is a genetically engineered oncolytic herpes simplex virus (oHSV) that exhibits aneurovirulence in normal cells. M002 selectively replicates in malignant cells, eliminating these cells through cellular burst during the lytic cycle. In the present study, we explored the efficacy of the M002 virus alone and in combination with low-dose ionizing radiotherapy in a human patient-derived xenograft (PDX) model of fusion-positive RMS (FP-RMS). Methods: A human FP-RMS PDX was established and maintained by injection into the quadriceps femoris muscle of athymic nude mice under Institutional Animal Care and Use Committee guidelines (IACUC-09363). Tumors were dissociated and cells were treated with increasing multiplicity of infection (MOI) of either the oHSV, R3659 or its genetically engineered variant, M002. A colorimetric assay evaluated the cytotoxicity of oHSV treatments on the RMS PDX cells after 24, 48, and 72 hours of infection. In separate experiments, cells treated with vehicle (control) or infected with M002 were exposed to irradiation (2 Gy), and viability was determined at 24, 48, 72, and 96 hours. Results: Treatment with M002 or its parent construct, R3659, significantly reduced RMS PDX cell viability in a dose-dependent manner at all time points. M002 showed slightly higher cytotoxicity than R3659 as measured by lethal dose 50% (LD50, 37±1.25 vs 44±0.95 PFU/cell, M002 vs R3659, at 24 hours, p=0.02). When sub-lethal doses of M002 were combined with low-dose irradiation, RMS PDX cell viability was significantly decreased compared to cells treated with either M002 or irradiation alone (26% decrease at 10 PFU/cell). Conclusions: Our preliminary data highlight that M002 exhibits cytotoxicity in a PDX model of FP-RMS. Treatment with M002 further increased the cytotoxicity of ionizing radiation compared to individual treatments, suggesting that oHSV sensitized the cells to radiotherapy. Future studies in vivo may provide more pre-clinical evidence for the radio-sensitizing and therapeutic potential of M002 in FP-RMS.

An open-label, multicenter study investigating RP2 oncolytic immunotherapy in combination with second-line systemic atezolizumab combined with bevacizumab in patients with locally advanced unresectable or metastatic hepatocellular carcinoma.

TPS4191 Background: Despite advances in treatment for unresectable hepatocellular carcinoma (HCC), long-term survival rates remain poor. The combination of atezolizumab (Atezo) plus bevacizumab (Bev) is approved as frontline therapy for advanced HCC, but only a minority of patients (pts) respond and secondary resistance usually occurs within months. HCC has an immune-suppressed tumor microenvironment (TME), mediated by activated immune checkpoint signaling and angiogenesis pathways, which may contribute to therapeutic resistance. RP2 is an enhanced potency oncolytic herpes simplex virus type 1 (HSV-1) that expresses the fusogenic gibbon ape leukemia virus glycoprotein with the R sequence deleted (GALV-GP-R–), GM-CSF, and an anti–CTLA-4 antibody-like molecule. The direct oncolytic effect coupled with immune stimulation by RP2 in the TME is intended to provide systemic antitumor activity and synergize with anti–PD-1/PD-L1 agents, such as Atezo. Preclinical data have demonstrated improved distribution of oncolytic HSV within tumors in combination with Bev, supporting the clinical combination of RP2 with Bev. This study will evaluate the safety and efficacy of RP2 combined with Atezo plus Bev as second-line systemic therapy for unresectable and advanced HCC (NCT05733598). Methods: This is an open-label, single arm, phase 2 trial. Up to 30 pts will be enrolled and receive RP2 in combination with Atezo plus Bev. Key inclusion criteria include advanced unresectable HCC with ≥1 measurable tumor of ≥1 cm in longest diameter, Child-Pugh class A, an Eastern Cooperative Oncology Group performance status of 0 to 1, and progression on 1 prior systemic treatment, which must have included a PD-1/PD-L1–directed agent. Key exclusion criteria include untreated/incompletely treated esophageal and/or gastric varices with bleeding or at high risk for bleeding and macroscopic invasion of the tumor into any major blood vessel(s) and/or main bile ducts. Pts will receive intratumoral RP2 Q2W for 4 doses, then Q3W for up to 4 doses. Bev will be given at 10 mg/kg Q2W starting with the first dose of RP2 then at 15 mg/kg Q3W starting with cycle 4; Atezo will be given at 840 mg Q2W for cycles 2 and 3, then at 1200 mg Q3W starting with cycle 4. Pts will receive treatment until confirmed progressive disease, loss of clinical benefit, or unacceptable toxicity. The primary endpoint is overall response rate (ORR), defined as the proportion of pts achieving a best overall response of complete response or partial response per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 as modified for this study. Secondary endpoints are safety, ORR using HCC-modified RECIST, duration of response, complete response rate, and progression-free survival. Clinical trial information: NCT05733598 .

EXPRESSION OF CONCERN: Therapeutic targeting of chemoresistant and recurrent glioblastoma stem cells with a proapoptotic variant of oncolytic herpes simplex virus.

Nusrat Jahan, Jae M. Lee, Khalid Shah, Hiroaki Wakimoto, "Therapeutic targeting of chemoresistant and recurrent glioblastoma stem cells with a proapoptotic variant of oncolytic herpes simplex virus", International Journal of Cancer 141, no. 8 (2017): 1671-1681. https://doi.org/10.1002/ijc.30811. This Expression of Concern is for the above article, published online on 31 May 2017, in Wiley Online Library (wileyonlinelibrary.com), and has been published by agreement between the authors, the journal's Editor-in-Chief, Christoph Plass, the Union for International Cancer Control and John Wiley & Sons, Ltd. The Expression of Concern has been agreed following concerns raised regarding figure 4g and 5d. The Control (PBS) 4X DAPI image in figure 5d was found to contain elements similar to the Control (PBS) DAPI image presented in figure 4g. The authors admitted that they had mistakenly supplied the incorrect image to represent DAPI in figure 5d. Since the original DAPI image for figure 5d is no longer available, this issue could not be resolved. The journal has decided to issue an Expression of Concern to alert the readers.