Abstract 7265: Using PBMC-humanized mice to identify optimal autologous CAR T products for maximized efficacy and minimized toxicity at an individual level: a study of CD19, CD22, and CD19x22-specific constructs in multiple PBMC donors

Abstract Chimeric antigen receptor T-cell (CAR T) therapy has revolutionized cancer treatment by providing targeted eradication of cancer cells. However, the efficacy and toxicity of CAR T cells can vary widely between individuals, posing challenges for patient-specific optimization. To address these gaps, we evaluated the efficacy, expansion, and cytokine induction profiles of CAR T using PBMC-humanized mice. Three autologous CAR T products with 4-1BB co-stimulation were manufactured from the PBMCs of three healthy human donors: CD19-specific, CD22-specific, and CD19x22-specific (dual) CAR T cells. The dual CAR T cells were transduced with lentiviral vectors encoding either CD19- or CD22-specific CARs, resulting in three distinct CAR T cell compositions: those targeting CD19 alone, CD22 alone, or both CD19 and CD22. NSG-MHC Class I/II double knock-out (DKO) mice were irradiated and engrafted with 10 million PBMCs from the same donors used for the autologous CAR T cells. Six days post-humanization, the mice were treated with one of the three autologous CAR T cells. We found that all CAR T products effectively eliminated B cells in vivo within three weeks post-treatment, while CD19 CAR Ts achieved clearance significantly faster than CD22 CAR Ts. Expansion levels of CAR T cells differed significantly by donors and constructs. Overall, mice treated with CD19 CAR Ts showed peak expansion earlier than those treated with the other two CAR Ts. Mice treated with CD22 CAR Ts reached the highest expansion across all donors during the 28-day study period. Notably, one donor treated with CD22 CAR Ts displayed more than a 10-fold higher expansion compared to the other two donors, which corresponded to decreased survival and significant body weight loss. In dual CAR T-treated mice, CAR T cells targeting CD19 alone showed more robust expansion than the others (54 to 99% of total CAR T cells, depending on timepoints and donors). Cytokine induction was both donor-dependent and CAR construct-dependent, particularly for IL-1β, IL-2, IL-3, IL-5, IL-6, and IL-10. In summary, PBMC-humanized mice are a valuable platform to assess individual variability in CAR T efficacy and toxicity. These insights highlight the need for personalized preclinical evaluations to optimize CAR T construct selection and predict patient-specific outcomes. Citation Format: Won Lee, Destanie Rose, Beau H. Parry, Joshua Gustafson, Rebecca Gardner, Heather Gustafson, James G. Keck, Jiwon Yang. Using PBMC-humanized mice to identify optimal autologous CAR T products for maximized efficacy and minimized toxicity at an individual level: a study of CD19, CD22, and CD19x22-specific constructs in multiple PBMC donors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7265.