TN/SCM pre-selection generates CAR T-cell products driving superior anti-tumor responses while curtailing severe CRS

Chimeric antigen receptor (CAR) T-cell expansion and persistence represent key factors to achieve complete responses and prevent relapses. These features are typical of early memory T cells, which can be highly enriched through optimized manufacturing protocols. Here, we investigated the efficacy and safety profiles of CAR T-cell products generated from pre-selected naive/stem memory T cells (TN/SCM), as compared to unselected T cells (TBULK). Notwithstanding their reduced effector signature in vitro, limiting CAR TN/SCM doses showed superior antitumor activity and the unique ability to counteract leukemia re-challenge in hematopoietic stem/precursor cell-humanized mice, featuring increased expansion rates and persistence, together with an ameliorated exhaustion and memory phenotype. Most relevantly, CAR TN/SCM proved to be intrinsically less prone to induce severe cytokine release syndrome, independently of the costimulatory endodomain employed. This safer profile was associated with milder T-cell activation, which translated in reduced monocyte activation and cytokine release. These data suggest that CAR TN/SCM are endowed with a wider therapeutic index compared to CAR TBULK. Overall design: Examination of monocytes transcriptomic differences when in the presence of pre-selected naive/stem memory T cells (TN/SCM) compared to unselected T cells (TBULK).