Development of CAR T cells Targeting U5 snRNP200 for the Treatment of Acute Myeloid and B-Lymphoid Leukemias

Developing chimeric antigen receptor (CAR) T cells for acute myeloid leukemia (AML) has been challenging due to a lack of known AML-associated antigens which spare normal hematopoietic precursor cells. Here we reasoned that donor auto-antibodies from AML recipients cured following allogeneic transplant and responsible for graft-versus-leukemia effect could be engineered to create effective CAR-T cells. We generated CAR-T cells against one such antigen - U5 snRNP200, an RNA helicase localized to the surface of AML cells and absent from normal hematopoietic precursors. Anti-U5 snRNP200 CAR T cells were effective in human and syngeneic models of AML as well as B acute lymphoblastic leukemia (B-ALL), a setting where surface U5 snRNP200 was also present. IL-18 armoring augmented target antigen expression due to cell surface trafficking of U5 snRNP200 with CD32A. These data thereby identify a CAR-T cell platform which addresses prior limitations in tumor-selectivity and safety for patients with acute leukemias. Overall design: We employed Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq) and T-cell Receptor Sequencing (TCR-seq) to simultaneously capture gene expression, surface proteomes, and the T-cell receptor repertoire. The TotalSeq-C Mouse Universal Cocktail (BioLegend) was applied to CD45.1+ endogenous blood cells as well as CD45.2+ RN2 leukemia, donor-derived T, and control or anti-U5 snRNP200 IL18-armored chimeric antigen receptor (CAR) T cells.