SINGLE-CELL TRANSCRIPTOME ANALYSIS REVEALS DISTINCT CHARACTERISTICS OF ANTI-CD22 CAR T-CELL INFUSION PRODUCTS ASSOCIATED WITH EFFICACY AND TOXICITY.

Background & Aim: CAR T-cell therapy has demonstrated remarkable success particularly for hematological malignancies. Nonetheless, treatment failure and toxicities remain obstacles to optimal response. Intrinsic CAR T-cell characteristics may play a pivotal role in their effectiveness. Therefore, studying infusion products may reveal insights into how clinical efficacy and toxicities stem from inherent CAR T-cell factors. Eleven autologous CD22 CAR T-cell products manufactured to treat children and young adults with B-ALL enrolled in a phase II study (NCT02315612) were analyzed by CITE-seq on the BD Rhapsody platform (Fig.1a). Illumina sequencing data was processed using BD Rhapsody Targeted Analysis Pipeline on Sevenbridge. Analysis and visualization were performed with Seurat and ggplot2 in Rstudio. Non-responders were defined as patients who failed to achieve or maintain a measurable residual disease (MRD)-negative remission 28-30 days after CAR T-cell infusion. Sequencing of 17,866 cells identified 19 distinct T-cell subpopulations (Fig.1b). Samples from the non-responder group exhibited a reduced number of clusters compared to the responder group, suggesting lower T-cell diversity among non-responders (Fig.1c). Non-responder sample NR4 was an outlier for unknown reasons. A distinctive pattern emerged between non-responders and responders. Samples from non-responders displayed a higher abundance of subpopulations (red arrow) which lacked CCR7 expression and were identified as effector T-cells (Teff) and effector memory T cells (Tem). While more prevalent subpopulations (red circle) in the responder group had CCR7high expression that were characterized as stem cell-like memory T-cells (Tscm) and central memory T cells (Tcm) (Fig.2). In the context of CAR-related hemophagocytic lymphohistiocytosis (HLH) toxicity (carHLH), cells demonstrated 12 clusters with no clear separation between carHLH (+) and carHLH(-) groups (Fig.3a). Analysis of cell percentages and subtypes revealed cluster10 had 82% cells from the carHLH(+) group, characterized as Tem, while cluster4 and cluster7 contained 29% and 34% cells, respectively, from the carHLH(+) group and were classified as Tscm and Tcm (Fig.3b/c/d). [ABSTRACT FROM AUTHOR]