Validation of a B cell acute lymphoblastic leukemia xenograft rat model for integrated efficacy, pharmacokinetics and safety of CD19 CAR-T

Abstract In preclinical studies of B cell acute lymphoblastic leukemia (B-ALL), mouse models have limitations related to their small body size, which restricts serial sampling required for integrated assessment of efficacy, safety, and pharmacokinetics (PK) assessments. To overcome these limitations, we developed a B-ALL xenograft rat model as an integrated platform for the preclinical evaluation of cell therapies and validated this platform by testing its ability to simultaneously assess efficacy, PK, and safety using a CD19 CAR-T standard. The B-ALL rat model was established using NALM-6 (human B-ALL cell line) cells, followed by intravenous injection of CD19 CAR-T three days later at doses of 1.0 (low) and 2.0 × 10⁸ cells/kg (high). B-ALL xenograft rat model successfully differentiated dose-dependent responses, demonstrating significant tumor regression without adverse effects in high-dose group, whereas low-dose group showed no efficacy. Kinetic analysis revealed peak expansion of CAR-T cells in high-dose group 3 weeks after injection, while low-dose group displayed no significant expansion. Crucially, this study demonstrates the utility of the model as an integrated PK-Efficacy evaluation platform with exploratory safety monitoring. We identified 2.0 × 10⁸ cells/kg as an effective therapeutic dose with a favorable safety profile, showing complete remission without evident toxicity under the tested conditions. This study is the first to validate a B-ALL xenograft rat model capable of simultaneously analyzing efficacy, safety, and biodistribution. By utilizing rats, a species widely accepted in toxicology, this disease-relevant model provides a robust platform to support the preclinical assessment of next-generation cell-based therapies.