Neurotoxicity associated with chimeric antigen receptor T-cell therapy

Chimeric antigen receptor T cell (CAR-T) therapy involves reengineering patient-derived or donor-derived T cells to express a synthetic CAR that can recognise specific cell-surface antigens, independently of major histocompatibility complex molecules. As of March 2025, six autologous CAR-T cell products have received regulatory approval from the United States Food and Drug Administration (FDA) for B-cell derived haematological malignancies and multiple myeloma, delivering effective and durable treatment responses. All currently approved CAR-T cell therapy products target either CD19 or B-cell maturation antigen (BCMA). However, there is an expansive list of new CAR-T constructs and/or indications currently being explored in the pre-clinical stages and clinical trials. Although the therapeutic potential of CAR-T cell therapy is substantial, the more widespread application of CAR-T cell therapy faces challenges, including overcoming unique and clinically significant CAR-T therapy-associated toxicities, namely cytokine release syndrome (CRS) and immune-effector cell associated neurotoxicity syndrome (ICANS). CAR-T cell-associated neurotoxicity can present with a diverse range of neurological and cognitive symptoms and signs, including tremor, dysgraphia, cognitive dysfunction, aphasia, seizures, and rarely cerebral oedema and death. As new CAR-T constructs and indications enter the therapeutic landscape, new class-specific toxicities have also emerged, including delayed-onset neurotoxicity with features of parkinsonism, as seen with BCMA-directed therapies in the pivotal clinical trials for multiple myeloma. Whilst much progress has been made in understanding CRS, comprehensive information about the clinical, biological and radiological correlates of CAR-T cell-associated neurotoxicity, and its mechanistic underpinnings remain largely unknown. Furthermore, prophylactic or pre-emptive intervention strategies have been hindered by the lack of predictive or diagnostic biomarkers for ICANS. Considering the lack of targeted therapies for ICANS, detailed analysis of the associated biomarkers remains a key area of unmet need in the field. This review provides a detailed analysis of CAR-T cell-associated neurotoxicity, with a focus on the novel pathophysiological insights into disease mechanisms, the clinical manifestations and diagnostic evaluation, candidate biomarkers for neurotoxicity, and the current therapeutic landscape for ICANS management.