Vaccine Educated T cells and a CD123 Bi-Specific T-Cell Engager for Treatment of Acute Myeloid Leukemia

Immunotherapy strategies in acute myeloid leukemia remain limited. CD123 is a promising target as it is overexpressed in myeloid blasts. This preclinical work investigates possible synergy of CD123 T cell engager and dendritic cell based vaccine, which can induce the expansion of leukemia specific T cells. Efficacy of combination therapy was evaluated in a patient-derived xenograft model and the infused T cells were later collected for single cell rnaseq to determine effects on gene expression pathways and clonality. In the present study, we demonstrated that the combination of DC/AML fusion vaccine and a CD123 T cell engager SAR440234 led to an increase in tumor specific T cell immunity and enhanced anti-leukemia effect in vitro. Furthermore, the combination treatment was shown to increase cytotoxic T cell subsets and clonotypic expansion and eradicate disease in vivo. Thus the combination of T cell engager and vaccination or adoptive T cell transfer is a novel approach that merits further investigation in clinical trials. Overall design: Cell suspensions following harvesting of bone marrow and spleen tissues from individual mice were cryopreserved. NSG mice had been injected with human T cells. Upon thawing, samples underwent dead cell removal (Miltenyi MACS kit) and human CD45 enrichment (Stem Cell Technologies). Based on cell yield, samples from 4 mice per treatment group (no treatment, Tc+IgG, uTc+SAR, veTc+IgG, veTc+SAR) were chosen for single cell RNA and TCR sequencing, yielding 20 samples from bone marrow and spleen compartments each. 5 spleen or bone marrow samples were pooled together (one sample per treatment group), and 32,000-40,000 cells were loaded in one channel of a Chromium Chip K (10x Genomics) and profiled using the Chromium Next GEM Single Cell 5' Kit v2 (10x Genomics). Full-length paired a/ß TCR libraries were obtained using the Chromium Single Cell V(D)J Enrichment Human T Cell (10x Genomics). cDNA, gene expression, and TCR library quality was assessed using the DNA High Sensitivity Bioanalyzer Chip (Agilent). Gene expression or TCR libraries were pooled and sequenced on a NovaSeq 6000 sequencer (Illumina).