Apheresis CD8⁺CCR7⁺CD45RA^- T-Cells as a Novel Biomarker Associated with CAR T-Cell Kinetics and Clinical Outcome

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of relapsed or refractory (r/r) diffuse large B-cell lymphoma (DLBCL); however, a significant proportion of patients fail to achieve a durable response, underscoring the need for reliable predictive biomarkers. We characterize T-lymphocyte subpopulations in apheresis samples from 23 r/r large B-cell lymphoma (LBCL) patients who received axicabtagene ciloleucel (axi-cel) to identify pre-treatment cell biomarkers associated with CAR T-cell kinetics and clinical outcomes. Immunophenotyping of T-cells within fresh apheresis samples and monitoring of circulating CAR T-cells were performed by multiparametric flow cytometry. The median peak CAR T-cell count was 45.2 CAR T-cells/mL. Strong CAR-T expanders (≥45.2 CAR T-cells/mL) exhibited higher values of both CD4⁺ (p = 0.011) and CD8⁺ (p = 0.023) central memory T-cells (T_CM; CCR7⁺CD45RA^-), as well as lower proportions of CD8⁺CD38⁺ T-cells in apheresis samples. In apheresis, a cut-off value of >4.3% of CD8⁺ T_CM predicted strong CAR-T expansion (AUC: 0.80; p = 0.023) and superior progression-free survival (p = 0.04) compared with patients who had CD8⁺ T_CM below the cut-off. Our data suggest that high frequencies of CD8⁺ T_CM cells in apheresis samples may represent a promising pre-treatment biomarker associated with strong CAR-T expansion and superior clinical outcome in r/r LBCL patients following axi-cel.