Chimeric antigen receptor (CAR) T-cell therapy is a promising treatment for neoplasia and autoimmune diseases. Immunocompromised mice are a common model to test the efficacy and safety of CAR T cells of human origin. Preclinical toxicity associated with human CAR T-cell products encompasses a spectrum of morphologic changes, with currently limited documentation in the scientific literature. The purpose of this retrospective study was to characterize the histopathologic features associated with human CAR T-cell administration in immunodeficient NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice (n = 392) submitted to 3 different academic institutions in the United States between 2017 and 2024. Lesions were categorized into xenogeneic graft-versus-host disease (xGvHD) (n = 287), aberrant proliferation of human T cells (n = 188), vascular pathologies (n = 66), on-target/off-tumor (OTOT) toxicity (n = 44), immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) in mice previously humanized with human CD34+ hematopoietic stem cells (HSCs) (n = 21), and acute lysis syndrome (ALS) (n = 5). This study provides veterinary pathologists with descriptive guidance on the pathology associated with human CAR T-cell therapy in immunodeficient mice. Additional molecular data and detailed information related to each construct are necessary to further investigate the translatability of such liabilities to the clinical setting.
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