Combination of loco-regional radiotherapy with a TIM-3 aptamer improves survival in diffuse midline glioma models

Pediatric diffuse midline gliomas (DMG) with H3-K27M-altered are aggressive brain tumors that arise during childhood. Despite advances in genomic knowledge and the significant number of clinical trials testing new targeted therapies, patient outcomes are still insufficient. Immune checkpoint blockades with small molecules, such as aptamers, are opening new therapeutic options that represent hope for this orphan disease. Here, we demonstrated that a TIM-3 aptamer as monotherapy increased the immune infiltration and elicited a strong specific immune response with a tendency to improve the overall survival of treated DMG-bearing mice. Importantly, combining TIM-3 Apt with radiotherapy increased the overall median survival and led to long-term survivor mice in two pediatric DMG orthotopic murine models. Interestingly, TIM-3 aptamer administration increased the number of myeloid populations and the pro-inflammatory ratios of CD8: Tregs in the tumor microenvironment as compared to non-treated groups after radiotherapy. Importantly, the depletion of T-cells led to a major loss of the therapeutic effect achieved by the combination. This work uncovers TIM-3 targeting as an immunotherapy approach to improve the radiotherapy outcome in DMGs and offers a strong foundation for propelling a phase I clinical trial using radiotherapy and TIM-3 blockade combination as a treatment for these tumors.