THER-02. Pediatric brain tumor cultures reveal differential susceptibility to four oncolytic viruses

INTRODUCTION: New therapeutic modalities such as Oncolytic viruses (OVs) are considered possible treatment options for pediatric brain tumors (PBTs) either as monotherapy or as adjuvants to immunotherapies. OVs specifically lyse tumor cells and can induce anti-tumor immune responses. Here, we evaluate the oncolytic potency of different clinically relevant OVs against various PBT entities. METHODS: The effect of four different OVs, Reovirus (R124), Newcastle Disease virus (NDV), Adenovirus (DNX-2401) and Herpes simplex virus-1 (rQNestin 34.5v.1), was assessed on patient-derived cell cultures belonging to four different PBT entities. Cell viability 5 days after virus treatment of diffuse midline gliomas (DMG n=6), atypical teratoid rhabdoid tumors (n=4), glioblastomas (n=1) and ependymomas (n=2) was measured using Cell Titer Glo assay to demonstrate the cytotoxic potency of each virus. RESULTS: Our screenings revealed that DNX-2401, rQNestin and NDV could infect and kill the majority of cell cultures (12 out of 13, 11 out of 13 and 11 out of 13, respectively). rQNestin34.5v.1 required lower amounts of infectious particles per cell (MedianEC50: 0.65±2.7) compared to NDV (3.5±1.7) and DNX-2401 (7.5±14.5), with DMGs being more sensitive for rQNestin34.5v.1 than non-DMGs. R124 was effective in only 6 out of 13 cultures, with DMGs being more resistant with EC50 > 100 (5 out of 6) compared to non-DMG cell lines with EC50 < 8 (5 out of 7). CONCLUSION: All cell lines revealed differential susceptibility to the 4 different OVs with at least one effective OV per cell line. Further analysis of transcriptome and methylome data might uncover genes and pathways which correlate with specific OV susceptibility and provide biomarkers for response prediction. Further investigation is ongoing to interpret how differential susceptibility affects OV-induced anti-tumor immunity.