Boosting CAR T-cell functionality with oncolytic viruses for the treatment of pediatric diffuse midline gliomas

Although the potential of CAR (chimeric antigen receptor) T-cells has been demonstrated in hematological malignancies, their efficacy remains limited in the treatment of solid tumors such as pediatric diffuse midline gliomas (DMGs). Contributing factors hampering the success of CAR T-cells include the immunosuppression induced by the DMGs and the surrounding tumor microenvironment (TME). Oncolytic viruses (OVs) have shown to reverse this immunosuppressive effect, suggesting a potential combinatorial benefit of OV and CAR T-cells. Infection with high concentrations of the Goravir adenovirus and R124 reovirus induced DMG (n=6 cultures) lysis without affecting viability of GD2 or B7H3 directed CAR T-cells. In addition, RNA sequencing of tumor cells showed altered gene expression of cell cycle and antiviral response pathways. When used in combination, cytotoxicity of the CAR T-cells was enhanced and complemented with increased release of pro-inflammatory cytokines and chemokines, especially with R124. Furthermore, CAR T-cells co-cultured with OV-infected DMGs demonstrated a more cytotoxic effector phenotype compared to co-cultures with non-infected DMGs. Finally, these data demonstrate the enhanced benefit of DMG pre-infection with OVs for boosted CAR T-cell activity.