Ibrutinib enhances stem-cell-memory T cell generation during early T cell activation but inhibits T cell proliferation

Ibrutinib has been demonstrated to restore T cell immunity of chronic lymphocytic leukemia patients, and enhance ex vivo expansion and function of CAR-T cells. In attempt to explore the effect of ibrutinib on unmanipulated T cells, we activated human PBMCs from healthy donors with CD3/CD28 stimulation and cultured them with or without ibrutinib under various conditions. Phenotypic and functional assessments were then performed using flow cytometry. Results showed that ibrutinib could downregulate programmed cell death protein 1 expression and reduce activation-induced cell death of T cells. Additionally, ibrutinib added at the onset of T cell activation, rather than 48 h later, could further promote the generation of CD45RA⁺CCR7⁺CD95⁺ stem-cell-memory T cell subset in the presence of IL-7 and IL-15. However, ibrutinib also suppressed the proliferation and cytokine-secretion capacity of T cells in a dose-dependent manner. Further RNA sequencing of activated CD8⁺ T cells demonstrated that ibrutinib administration at the onset of T cell activation modulated multiple TCR downstream signaling pathways, notably downregulating mTORC1 signaling and upregulating FOXO1 signaling. In contrast, ibrutinib added 48 h post-activation did not show these effects. These findings suggest that caution should be exercised when incorporating ibrutinib into ex vivo expansion system for adoptive non-genetically engineered T cells or combining ibrutinib with these T cell immunotherapies in clinical trial settings.