Early cytokine and chemokine signals shape the anti-AML activity of bispecific engager-secreting T cells

Immunotherapies, including cell therapies, are effective anti-cancer agents. However, cellular product persistence can be limiting with short functional duration of activity contributing to disease relapse. A variety of manufacturing protocols are used to generate therapeutic engineered T-cells; these differ in techniques used for T-cell isolation, activation, genetic modification, and other methodology. We sought to determine how preselection affected the phenotype of T cells engineered to secrete a CD123xCD3 bispecific engager (ENG-T). These cells were designed to treat acute myeloid leukemia (AML). We evaluated the effect of T-cell selection on transduction efficiency, T-cell activation, short- and long-term anti-AML cytotoxicity, and gene transcription. Unselected, CD4, CD8, and CD4/CD8 pre-selected ENG-T cells have minor differences in T-cell subset components, equivalent activation, and equal cytotoxicity in short-term assays. While unselected and CD4/CD8-selected ENG-T cells have identical CD4:CD8 composition prior to target cell exposure, serial stimulation in vitro showed CD4/CD8 pre-selection supports ENG-T cell survival and long-term activity. Likewise, CD4 and CD4/CD8 pre-selected ENG-T cells display superior anti-tumor efficacy and prolong murine survival in AML xenografts. Unselected ENG-T cells are exposed to cytokines during early manufacture that imprint upregulation of intracellular inflammatory pathways. This early activation likely underpins long-term observed functional differences. Pre-selection of T cells from banked patient biospecimens decreased blast contamination, exposure to inflammatory cytokines, and may improve T-cell expansion during manufacture. Pre-selection of T-cell products should continue to be performed to enhance the quality of clinical cellular therapeutics.