Fig. 1: Study overview and workflow.

a, Swimmer plot illustrating the responses of individual pediatric patients with B-ALL to CAT CAR T-cell therapy and timepoints of sample collection. Attainment of complete remission was associated with attainment of B cell aplasia in all cases. Patient 5 had an isolated unilateral ocular relapse of CD19⁺ leukemia, which was treated with enucleation and remains in ongoing minimal residual disease (MRD) negative remission with no other intervention. Heat map to the right demonstrates timepoint representation per patient. Filled black boxes indicate the presence of the timepoint. Product = infusion products (M0); early = M1–M3; mid = M4–M6; late = M7–M60. b, Schematic workflow of study design. Samples were collected from infusion products (PROD), peripheral blood (PB) and bone marrow (BM) between M0 and M60. Samples were used either for flow-based immunophenotyping or for single-cell GEX and TCR sequencing on the Chromium 10x platform. RT, reverse transcription; Seq, sequencing. c, UMAP of all cells in the dataset highlighting cell types captured (left) and expression of the CAT-scFv CAR construct (right). CAT-scFv, low-affinity CAR (CAT) incorporating a CD19-specific scFv.