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. The currently used nontargeted chemo-/radiotherapy conditioning regimens cause tissue injury and induce an array of immediate and delayed adverse effects, which limits the use of this potentially curative treatment. The growing demand to replace canonical conditioning regimens has led to the development of alternative approaches based on antibody‒drug conjugates, naked antibodies and CAR T cells. Here, we propose a preconditioning strategy based on targeting CD45 on hematopoietic cells with CAR45 T cells. To avoid fratricide of CD45 CAR T cells, targeted genomic disruption of the CD45 gene was performed in human CD45 CAR T cells in combination with dasatinib treatment. CD45 Δ CAR45 T cells showed impressive activity in terms of target cell elimination in vitro and depletion of tumor cells in vivo or human hematopoietic cells in humanized immunodeficient mice engrafted with human blood-derived HSCs. CD45 Δ CAR45 NK cells also exhibited potent killing activity against tumor cell lines and human hematopoietic cells. Therefore, fratricide-resistant CAR45 T and NK cells have the potential to provide the benefits of full myeloablative conditioning and therapy for hematologic malignancies. Thus, we provide the proof of concept for the generation and preclinical efficacy of CAR T cells directed against CD45-expressing cells.