DMG-13. Cognitive and motor effects of TIM-3 blockade in diffuse midline glioma murine models

Diffuse midline gliomas (DMGs) are aggressive pediatric brain tumors with dismal prognoses and limited treatment options. Importantly, radiotherapy remains the standard of care, but it is not curative and often leads to significant cognitive impairment due to therapy-induced neuroinflammation. In this context, TIM-3 (T cell immunoglobulin mucin-3) emerges as a promising immunotherapy target. We previously showed that inhibition of TIM-3 improved survival in preclinical immunocompetent DMG models resulting in 50% of cured-mice with immune memory. However, its long-term effects on cognitive and motor functions remain unexplored. This study evaluates the motor and cognitive consequences of TIM-3 blockade therapy in the long-term survivor (anti-TIM-3 LTS) mice, investigating its impact on neuroinflammation and brain resident populations. Interestingly, motor coordination, memory, and learning remained intact in anti-TIM-3 LTS mice compared to non-tumor controls, measured by motor (rotarod, pole, and bar) and cognitive (NORT, FCT, and MWM) tests one and two months after tumor clearance. Importantly, no differences were found between the different sexes in both motor and cognitive tests. Moreover, immunofluorescence analyses two months after tumor elimination showed no persistent activation of reactive astrocytes or microglia, with no chronic T cell infiltration detected in the cortex, cerebellum, hippocampus, and pons of the anti-TIM-3 LTS mice. Expression levels of pro-inflammatory cytokines and chemokines, including TNF-α, IL-1β, and IFN-γ, were comparable across groups, and neuronal markers linked to synaptic function and neurogenesis, such as Dcx and Syn1, also remained unaffected in the above-mentioned locations of the brain. Overall, we demonstrated that TIM-3 inhibition controls DMG growth, and does not lead to long-term neuroinflammation that in turn could result in cognitive and/or motor dysfunction. These findings highlight TIM-3 as a promising immunotherapeutic target for DMG, with the potential to enhance survival while maintaining the quality of life of patients.