Abstract 5929: microRNA control of an oHSV vector allows for robust oncolysis and selective control of viral replication in normal tissues
Authors: Kennedy Edward M. , Farkaly Terry , Goshert Caitlin , Colthart Allison , Behera Prajna , Grzesik Peter , Grant Kyle , Paglia Michael , Grandi Paola , Quéva Christophe , Finer Mitchell , Lerner Lorena 
Published: August 2018

Abstract
Effective treatment of advanced stage cancer with oncolytic viruses requires potent cancer cell-specific oncolytic activity. We modified oncolytic HSV (oHSV) to utilize a novel conditional-lethal strategy that retains all viral genes to maintain potency of the oncolytic virus, yet block replication in normal cells. In addition, we armed the virus with extracellular matrix decreasing enzyme to promote viral spread and immunomodulatory payloads to increase recruitment and effector function of immune cells. To enhance the selectivity of viral replication to tumor cells, Oncorus engineered oHSVs containing microRNA (miRNA)-binding cassettes (miR-T) in essential genes required for viral replication. The first Oncorus clinical candidate, ONCR-1, under development for the treatment recurrent glioblastoma multiform (GBM), has been attenuated for replication in neurons, the most trophic cell type for HSV. Neuronal attenuation was achieved by inserting binding sites for a highly specific neuronal miRNA, miR-124, into the 3′UTR of the essential ICP4 gene. We demonstrate that these engineered miR-124 response elements can selectively inhibit the expression of ICP4 and VP5 as well as the expression of ONCR-1 payloads. This attenuation strategy eliminates viral replication in miR-124 expressing cells without compromising oncolytic activity in cancer cells, thereby providing a therapeutic window. We extended the design oHSV attenuation by profiling of miRNAs expression in panels of solid tumors and non-diseased tissue counterparts in other potentially high-risk tissues, prioritized to indications amenable to local or systemic administration. We leveraged our comprehensive normal and malignant tissue dataset to identify numerous highly expressed unique non-cancerous tissue-specific candidate miRNAs. Insertion of miR-T cassettes into HSV-1 genes collaborated to stall the early steps in the viral replication cycle and further increased the depth and breadth of oHSV attenuation in non-disease tissue relative to the single miR-T cassette in ICP4. We found that miR-122, a highly expressed miRNA in normal hepatocytes, is low or absent in many carcinoma cells. Insertion of miR-122 cassette into the 3′UTR of an immediate early gene, ICP27, inhibited completely viral replication in miR-122 expressing cells. oHSV with dual miR-124 and miR-122 was potently attenuated cells expressing one or both miRs while displaying a robust oncolytic activity in malignant cells. We have shown that insertion of miR-T cassettes in essential viral genes effectively attenuates oHSV replication in normal human cells, and most importantly, robust oncolysis was retained in cancer cells. This work extends the miR-T paradigm to multiple viral genes with diverse miRNA targets, thus expanding the protection of normal tissues and facilitating the application of oHSV to the treatment of multiple malignancies.
Citation Format: Edward M. Kennedy, Terry Farkaly, Caitlin Goshert, Allison Colthart, Prajna Behera, Peter Grzesik, Kyle Grant, Michael Paglia, Paola Grandi, Christophe Quéva, Mitchell Finer, Lorena Lerner. microRNA control of an oHSV vector allows for robust oncolysis and selective control of viral replication in normal tissues [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 5929.