Targeting CD45 by gene-edited CAR T cells for leukemia eradication and hematopoietic stem cell transplantation preconditioning.

Hematopoietic stem cell transplantation (HSCT) is widely used to treat patients with life-threatening hematologic and immune system disorders. Current nontargeted chemo-/radiotherapy conditioning regimens cause tissue injury and induce an array of immediate and delayed adverse effects, limiting the application of this life-saving treatment. The growing demand to replace canonical conditioning regimens has led to the development of alternative approaches, such as antibody-drug conjugates, naked antibodies, and CAR T cells. Here, we introduce a preconditioning strategy targeting CD45 on hematopoietic cells with CAR45 T cells. To avoid fratricide of CD45 CAR T cells, genomic disruption of the CD45 gene was performed on human CD45 CAR T cells in combination with the signaling kinase inhibitor dasatinib. CD45 CAR45 T cells showed high cytotoxicity and depletion of tumor cells These cells were effective in elimination of human hematopoietic cells engrafted in humanized immunodeficient mice by transfusion with human blood-derived hematopoietic stem cells (HSCs). Similarly, CD45 CAR45 natural killer (NK) cells exhibited potent cytotoxicity toward tumor cell lines and human hematopoietic cells . Thus, we provide the proof of concept for the generation and preclinical efficacy of fratricide-resistant CAR45 T and NK cells directed against CD45-expressing tumors and hematopoietic cells.