Abstract PR005: Closed-Loop Sonothermogenetic Control of CAR T Cells for Precision Immunotherapy of Brain Tumors

Abstract Achieving durable chimeric antigen receptor (CAR) T cell responses against primary and metastatic brain tumors requires strategies that enable precise intracranial control of therapeutic activity while maintaining safety. Solid tumors in the central nervous system pose major barriers to immunotherapy, including antigen heterogeneity, immunosuppressive tumor microenvironments, and the need to avoid systemic toxicity. Here, we report a closed-loop sonothermogenetic platform that enables remote, noninvasive, and repeatable spatiotemporal control of CAR T cell function through intact skull. CAR T cells were engineered with a genetically encoded thermal switch (TS) that enables heat-induced expression of transgenes, including NKG2D-based T cell engagers (TCEs). Using magnetic resonance imaging–guided focused ultrasound (MRgFUS) integrated with real-time MR thermometry and a closed-loop proportional–integral–derivative (PID) control algorithm, we achieved the precise temperature control (41. 5 ± 0. 1 °C) required for targeted activation of CAR T cells. This closed-loop system enabled repeatable and spatially confined induction of gene expression within brain tumors (sonothermogenetic control), allowing metronomic activation of CAR T cell engagers. Comprehensive histological and imaging analyses confirmed that closed-loop MRgFUS–mediated heating was well tolerated, producing only transient neuroinflammatory changes without evidence of neuronal degeneration or lasting tissue damage. We demonstrate that sonothermogenetic control enables robust and reversible activation of CAR T cells in vitro and in vivo, with transgene expression returning to baseline 24 hours after activation and remain inducible upon subsequent heating. In murine models of breast cancer brain metastasis (BCBM), localized sonothermogenetic induction of NKG2D TCEs redirected CAR T cell cytotoxicity toward antigen-negative tumor cells, overcoming intratumoral antigen heterogeneity and resulting in durable tumor control and extended survival. In a syngeneic glioblastoma model characterized by myeloid-derived suppressor cell (MDSC) –mediated immunosuppression, sonothermogenetic production of murinized TCEs significantly reduced both the percentage and absolute count of tumor-infiltrating monocytic MDSCs (M-MDSCs) in the TS. TCE. CART+FUS cohort compared to unheated or WT controls and significantly improved antitumor responses compared to CAR T cell therapy alone. Collectively, these findings establish closed-loop sonothermogenetics as a powerful and clinically translatable platform for spatial and temporal regulation of CAR T cell activity in the brain. This approach provides a new framework for metronomic, remotely controlled immunotherapy capable of overcoming antigen escape and immunosuppressive tumor microenvironments while maintaining safety, thereby advancing next-generation cell therapies for intracranial malignancies. Citation Format: Costas Arvanitis, Chulyong Kim, Ali Zamat, Gabriel A. Kwong. Closed-Loop Sonothermogenetic Control of CAR T Cells for Precision Immunotherapy of Brain Tumors abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Brain Cancer; 2026 Mar 23-25; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86 (6Suppl): Abstract nr PR005.