Pathology associated with human CAR T cell administration in NOD.Cg- Prkdc scid Il2rg tm1Wjl /SzJ (NSG) mice: A retrospective analysis

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- Prkdc scid Il2rg tm1Wjl /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.