Development of Immunostimulatory Virotherapy Without Neurotoxicity for the Treatment of Brain Malignancies

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PROJECT SUMMARY Glioblastoma is one of the most lethal and recalcitrant of all malignant solid tumors. Treatment modalities have not improved significantly in two decades. Glioblastoma is difficult to treat because of its inherent heterogeneity, a low mutational load that reduces its intrinsic immunogenicity, and a highly immunosuppressive microenvironment that prevents infiltration by critical immune cells. Although immunotherapy has transformed modern cancer treatment, patients with glioblastoma have generally not demonstrated strong or durable responses, leading to the classification of glioblastoma as an immunologically ‘cold’ tumor. Novel therapies that can augment immunotherapy and enhance the anti-tumor immune response are urgently needed. Oncolytic virotherapy is a novel platform for treating brain malignancies and potentiating tumors that respond poorly to standard therapeutic approaches, including immunotherapy. Recombinantly-modified oncolytic viruses permit a multifaceted and synergistic therapeutic drug design approach that directly destroys the tumor through targeted lysis, while also expressing immunostimulatory transgenes in a complementary manner that enhance immune-mediated tumor eradication. Implicyte, Inc. has developed two non-neurotoxic chimeric vesicular stomatitis viruses (VSV) that selectively infect and destroy glioblastoma cells, but not normal brain tissue. This virotherapy platform features several key innovations: it is non-neurotoxic and safe for use in the brain; it can be further engineered to express multiple immunostimulatory transgenes; it has the ability to destroy secondary tumors in the brain; it can evade neutralizing antibodies allowing for re-dosing; and it can target multiple cancer types. Here we propose to further advance our novel non-neurotoxic chimeric VSVs by engineering them to express immunostimulatory transgenes that will significantly enhance the anti- tumor immune response. In Specific Aim 1, we will further improve Implicyte’s chimeric VSV viruses by ‘arming’ them with two immunostimulatory transgenes. These novel viruses will be validated using in vitro cell culture assays to ensure they replicate as well as the parental viruses, are non-toxic to primary human neurons, and express the immunostimulatory transgenes at high levels. In Specific Aim 2, we will use in vivo syngeneic mouse models to evaluate the efficacy and immunostimulatory enhancement of these viruses. In these in vivo studies, we expect expression of the immunostimulatory transgenes to accelerate elimination of the tumor, improve overall survival, and induce immunological memory in mice challenged with a second tumor. Once this study is complete, we will have a lead clinical candidate that can be advanced to Phase II-supported IND-enabling studies to secure approval for future clinical trials. Implicyte’s non-neurotoxic oncolytic virotherapy, which combines direct tumor lysis with an anti-tumor immune response, has the potential to not only eradicate a patient’s tumor, but prevent its reoccurrence aswell.