Abstract 4572: mONCR-177 oncolytic virotherapy stimulates anti-tumor and anti-viral immunogenicity

Oncolytic viruses represent a promising class of therapeutic agents for the treatment of cancers that poorly respond to immune checkpoint inhibitors. Oncorus is developing ONCR-177, an oncolytic herpes simplex virus engineered for potent oncolysis and stimulation of antitumor immunity. ONCR-177 is replication competent in tumor cells, but its replication and neuropathic activities are attenuated in healthy cells using microRNA-dependent degradation of viral transcripts and by mutations in UL37 that prevent retrograde transport in neurons. In addition, ONCR-177 encodes five immune-stimulatory transgenes: IL-12, CCL4, FLT3LG, a PD-1 humanized antagonist VHH nanobody, and a CTLA4 blocking monoclonal antibody. Transgenes were chosen to efficiently recruit effector T (CD8 and CD4 Th1), NK, and classical dendritic cells to the tumor, and to counter upregulation of immune checkpoints. The individual and collective mechanisms of action of the transgenes are designed to augment local and distant innate and adaptive anti-tumor immune responses.

Tumor-specific response was evaluated using mONCR-177, a mouse functional surrogate for ONCR-177, that is built on the same base vector ONCR-159 but expresses the immune transgenes suitable for murine studies. In a CT26 bilateral colon carcinoma tumor model and a MC38 colon adenocarcinoma model, immune responses elicited by intratumoral injection of mONCR-177 and ONCR-159 were compared. Intratumoral T cell responses were evaluated for a tumor-associated antigen (TAA) and an HSV specific antigen in the MC38 model.

In the CT26 tumor model, treatment with mONCR-177 resulted in greater immune infiltration with a higher activation status and an improved CD8:Treg ratio. Treatment with mONCR-177 elicited significantly more tumor antigen specific IFNγ and TNFα producing, intratumoral CD8T cells. The increase in anti-tumor response with mONCR-177 treatment was further evidenced by the increase in polyfunctional CD8 T cells producing IFNγ, TNFα, and/or IL-2 in response to TAA stimulation.

In the MC38 tumor model, treatment with mONCR-177 resulted in greater immune infiltration in both the injected and non-injected tumor. The CD8:Treg ratio was improved and PD-1 expression was decreased. Tumor antigen specific cytokine production was higher with mONCR-177 treatment. Additionally, a significant increase in HSV-specific polyfunctional CD8+ T cells was observed.

mONCR-177 effectively stimulates an intratumoral immune response to both tumor and viral antigens. Treatment results in increased infiltrating immune cells, activation, and polyfunctional CD8+ T cells. These results highlight the dual modality mechanism of action of mONCR-177 treatment through direct tumor cell killing and immune stimulation through the antiviral response, and their enhancement by the immune stimulatory transgenes.

Citation Format: Melissa Hayes, Agnieszka Denslow, Jacqueline Hewett, Daniel Wambua, Lingxin Kong, Jacob Spinale, Peter Grzesik, Jennifer Lee, Terry Farkaly, Edward M. Kennedy, Lorena Lerner, Christophe Queva, Brian Haines, Sonia Feau. mONCR-177 oncolytic virotherapy stimulates anti-tumor and anti-viral immunogenicity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4572.

Abstract 940: Development of ONCR-177, an miR-attenuated oncolytic HSV-1 designed to potently activate systemic antitumor immunity

ONCR-177 is a highly modified recombinant oncolytic Herpes Simplex Virus (oHSV) designed to be a safe and efficacious therapy for the treatment of solid tumor indications. Complementary safety mechanisms, such as tissue-specific miR attenuation of essential viral genes and UL37 mutation, were introduced to reduce replication, neuropathic activity, and latency in normal cells, while preserving oncolytic ability in tumor cells. In addition, ONCR-177 is armed with five transgenes: the NK and T cell activating cytokine IL-12, the chemokines CCL4 and FLT3LG (extracellular domain) to allow for expansion and recruitment of classical dendritic cells, and antagonists to the clinically validated immune checkpoint targets PD-1 and CTLA-4 to counter T cell exhaustion. Therefore, ONCR-177 is proposed to have a dual mechanism of action whereby the miR attenuation strategy allows for selective oncolysis of tumors cells and the transgenes mediate potent stimulation of systemic anti-tumor immunity. Since human IL-12 and the anti-CTLA-4 antagonist do not cross-react with the mouse targets, most nonclinical pharmacology studies were conducted with the mouse surrogate mONCR-171, which expresses within the same base vector as ONCR-177 the mouse equivalent to the ONCR-177 transgenes. Intra-tumoral administration of mONCR-171 in the oHSV-sensitive A20 BALB/c lymphoma bilateral tumor model resulted in response rates (partial and complete tumor regressions) of 100% and 80%, respectively, on the injected (ipsilateral) and distant (contralateral) tumor. mONCR-171 was also highly efficacious in the B16F10 melanoma model, an oHSV-resistant C57BL/6 based tumor model engineered to be permissive to oHSV by introduction of Nectin-1, and in the oHSV-resistant MC38 C57BL/6 colon carcinoma model. Abscopal anti-tumor activity could not be explained by propagation of the virus since viral DNA and transgenes were only detectable in the injected tumor. Rather, mONCR-171 treatment resulted in increased numbers of activated NK cells, CD8 and CD4 T cells, and classical dendritic cells. The proportion of Tregs decreased, resulting in large CD8/Treg ratios. These changes in immune contexture occurred in both the ipsilateral and contralateral tumor and were more pronounced with mONCR-171 treatment compared to the base vector without transgenes, indicating that the observed abscopal effects were due to the elicitation of systemic anti-tumor immunity mediated in part by the transgenes. These encouraging preclinical data warrant the clinical investigation of ONCR-177 in patients with metastatic cancer.

Citation Format: Brian B. Haines, Agnieszka Denslow, Michael S. Ball, Jacqueline Gursha, Daniel Wambua, Cecilia Kwong, Lingxin Kong, Prajna Behera, Peter Grzesik, Caitlin Goshert, Allison Colthart, Jennifer S. Lee, Terry Farkaly, Edward M. Kennedy, Lorena Lerner, Christophe Queva. Development of ONCR-177, an miR-attenuated oncolytic HSV-1 designed to potently activate systemic antitumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 940.

Abstract 4698: ONCR-1, a novel herpes simplex virus expressing MMP9 and ULBP3 transgenes, evokes potent oncolysis and development of antitumor immune responses

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor associated with poor prognosis and resistance to current therapies. ONCR-1 is a novel oncolytic herpes simplex virus type-1 vector in development for the treatment of GBM. ONCR-1 utilizes a unique conditional-lethal strategy in which miR124 binding sites are inserted into the ICP4 locus to prevent viral replication in neuronal cells while preserving one copy of the γ34.5 gene and enabling potent cytotoxicity in tumor cells. ONCR-1 is armed with a matrix metalloproteinase 9 (MMP9) transgene to facilitate viral spread in the tumor extracellular matrix. Further, ONCR-1 expresses a UL16 binding protein 3 (ULBP3) transgene to activate NK and CD8+ T cells via the NKG2D receptor and promote antitumor immune responses. In human and murine tumor cells in vitro, ONCR-1 evoked potent cytotoxicity. ONCR-1 increased proteolytic MMP in cell supernatants and ULBP3 cell surface expression with no effect on related NKG2D ligands. In mice bearing subcutaneous or orthotopic human U251 GBM tumors, ONCR-1 administered intratumorally (3x105-3x106 PFU QDx1) inhibited tumor growth and prolonged survival. Ex vivo analysis of immune cells in subcutaneous tumors showed significant increases in virally evoked NKG2D+ NK cells with ONCR-1 treatment. In mice bearing dual flank subcutaneous syngeneic A20 tumors, ONCR-1 significantly inhibited tumor growth in injected tumors (1x105-3x105 PFU, Q2Dx3) and evoked potent systemic antitumor immune responses as evidenced by significant inhibition of distal noninjected left flank tumors. IFNγ production from isolated splenocytes cultured in the absence and presence of A20 tumor cells was significantly augmented in ONCR-1-treated animals, providing further evidence of an enhanced antitumor immune response. Moreover, in mice bearing subcutaneous A20 tumors in which ONCR-1 evoked complete tumor regression, complete protection from rechallenge with A20 tumor cells was observed. Depletion of NK cells or CD8+ T cells in mice resulted in inhibition of ONCR-1-mediated antitumor effects in both injected and noninjected murine A20 tumors, supporting an immune mechanism of action. Our preclinical studies demonstrate that ONCR-1 evokes tumor cell killing by direct oncolysis and by enhancing antitumor immune responses. ONCR-1 represents a novel clinical candidate for the treatment of GBM.

Citation Format: Alexandra Hicks, Paola Grandi, Michael Paglia, Jingzang Miu, Cecilia Kwong, Jacqueline Gursha, Michael Ball, Weiguo Yao, Daniel Wambua, Terry Farkaly, Kyle Grant, Laura Viggiano Salta, Lorenz Ponce, Joseph Glorioso, Christophe Queva, Mitchell Finer. ONCR-1, a novel herpes simplex virus expressing MMP9 and ULBP3 transgenes, evokes potent oncolysis and development of antitumor immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4698.

Targeting PI3K signaling to ameliorate chronic graft versus host disease

The phosphoinositide 3-kinase (PI3K) pathway is a key signaling pathway necessary for T cell activation, differentiation and metabolism. T effector cells rely on increased PI3K signaling to fuel glycolysis for their metabolic needs, while T regulatory cells downregulate PI3K and favor lipid oxidation. The metabolic processes of lymphocytes modulating chronic graft versus host disease (cGVHD) have remained largely unexamined and represent a novel therapeutic strategy for this disease. Here, we investigated the role of PI3K signaling in a murine model of cGVHD that is etiologically linked to up regulated germinal centers (GCs) and characterized by multisystem organ disease; including fibrosis of the lung, which results in pulmonary dysfunction. We hypothesized that inhibition of PI3K signaling would alter the activation and/or function of GC-facilitating T follicular helper (TFH) cells resulting in lessened disease. The findings in this study are that mice treated with a PI3Kd inhibitor had decreased pulmonary dysfunction similar to that of the control, non-cGVHD mice. The frequencies of splenic TFH cells as well as GC B cells were decreased by a PI3K delta inhibitor compared to non-treated cGVHD controls. In a similar manner, mice that received PI3K kinase delta dead Tregs also had decreased TFH frequency as well as reduced pulmonary dysfunction. Our results indicate the differential requirement for signaling through PI3K delta and suggest that targeting this pathway may be a potential new therapy for treatment of cGVHD. Additional studies are required to validate the potential therapeutic use.

AZD7762, a novel checkpoint kinase inhibitor, drives checkpoint abrogation and potentiates DNA-targeted therapies

Insights from cell cycle research have led to the hypothesis that tumors may be selectively sensitized to DNA-damaging agents resulting in improved antitumor activity and a wider therapeutic margin. The theory relies on the observation that the majority of tumors are deficient in the G1-DNA damage checkpoint pathway resulting in reliance on S and G2 checkpoints for DNA repair and cell survival. The S and G2 checkpoints are regulated by checkpoint kinase 1, a serine/threonine kinase that is activated in response to DNA damage; thus, inhibition of checkpoint kinase 1 signaling impairs DNA repair and increases tumor cell death. Normal tissues, however, have a functioning G1 checkpoint signaling pathway allowing for DNA repair and cell survival. Here, we describe the preclinical profile of AZD7762, a potent ATP-competitive checkpoint kinase inhibitor in clinical trials. AZD7762 has been profiled extensively in vitro and in vivo in combination with DNA-damaging agents and has been shown to potentiate response in several different settings where inhibition of checkpoint kinase results in the abrogation of DNA damage-induced cell cycle arrest. Dose-dependent potentiation of antitumor activity, when AZD7762 is administered in combination with DNA-damaging agents, has been observed in multiple xenograft models with several DNA-damaging agents, further supporting the potential of checkpoint kinase inhibitors to enhance the efficacy of both conventional chemotherapy and radiotherapy and increase patient response rates in a variety of settings.

Amphicoup-TF, a nuclear orphan receptor of the lancelet Branchiostoma floridae, is implicated in retinoic acid signalling pathways

In vertebrates, the orphan nuclear receptors of the COUP-TF group function as negative transcriptional regulators that inhibit the hormonal induction of target genes mediated by classical members of the nuclear hormone superfamily, such as the retinoic acid receptors (RARs) or the thyroid hormone receptors (TRs). To investigate the evolutionary conservation of the roles of COUP-TF receptors as negative regulators in the retinoid and thyroid hormone pathways, we have characterized AmphiCOUP-TF, the homologue of COUP-TFI and COUP-TFII, in the chordate amphioxus (Branchiostoma floridae), the closest living invertebrate relative of the vertebrates. Electrophoretic mobility shift assays (EMSA) showed that AmphiCOUP-TF binds to a wide variety of response elements, as do its vertebrate homologues. Furthermore, AmphiCOUP-TF is a transcriptional repressor that strongly inhibits retinoic acid-mediated transactivation. In situ hybridizations revealed expression of AmphiCOUP-TF in the nerve cord of late larvae, in a region corresponding to hindbrain and probably anterior spinal cord. Although the amphioxus nerve cord appears unsegmented at the gross anatomical level, this pattern reflects segmentation at the cellular level with stripes of expressing cells occurring adjacent to the ends and the centers of each myotomal segment, which may include visceral motor neurons and somatic motor neurons respectively, among other cells. A comparison of the expression pattern of AmphiCOUP-TF with those of its vertebrate homologues, suggests that the roles of COUP-TF in patterning of the nerve cord evolved prior to the split between the amphioxus and vertebrate lineages. Furthermore, in vitro data also suggest that Amphi-COUP-TF acts as a negative regulator of signalling by other nuclear receptors such as RAR, TR or ER.

Mlx, a novel Max-like BHLHZip protein that interacts with the Max network of transcription factors

Mad:Max heterodimers oppose the growth-promoting action of Myc:Max heterodimers by recruiting the mSin3-histone deacetylase (mSin3. HDAC) complex to DNA and functioning as potent transcriptional repressors. There are four known members of the Mad family that are indistinguishable in their abilities to interact with Max, bind DNA, repress transcription, and block Myc + Ras co-transformation. To investigate functional differences between Mad family proteins, we have identified additional proteins that interact with this family. Here we present the identification and characterization of the novel basic-helix-loop-helix zipper protein Mlx (Max-like protein x), which is structurally and functionally related to Max. The similarities between Mlx and Max include 1) broad expression in many tissues, 2) long protein half-life, and 3) formation of heterodimers with Mad family proteins that are capable of specific CACGTG binding. We show that transcriptional repression by Mad1:Mlx heterodimers is dependent on dimerization, DNA binding, and recruitment of the mSin3A.HDAC corepressor complex. In contrast with Max, Mlx interacts only with Mad1 and Mad4. Together, these findings suggest that Mlx may act to diversify Mad family function by its restricted association with a subset of the Mad family of transcriptional repressors.