ROR2-expressing acute myelogenous leukemia cells can be selectively targeted by anti-ROR2 CAR T cells

Chimeric antigen receptor (CAR) T cells have revolutionized the treatment of B-cell malignancies but have not yet succeeded in acute myeloid leukemia (AML), largely due to the lack of cell surface antigens that can distinguish leukemia cells from essential normal hematopoietic stem cells (HSCs). Here, we used a newly developed high-affinity monoclonal antibody (mAb) B16, which is specific for the surface ROR2 in both human and mouse. Although ROR2 is a developmentally restricted protein that is primarily expressed during embryogenesis, we find that ROR2 protein is generally expressed by AML cells, including leukemia stem cells (LSCs), in patients with adverse-risk disease. Consistently, ROR2 is undetectable in most normal postnatal tissues and HSCs. Additionally, ROR2 can activate STAT3 signaling in response to Wnt11 in AML. Employing the binding domain of the anti-ROR2 mAb, we generated anti-ROR2 CAR T cells that selectively eliminated ROR2-positive AML cells of these patients while sparing normal HSCs. Intravenous infusion of such anti-ROR2 CAR T cells into immune-deficient mice selectively eradicated engrafted ROR2-positive human AML cells, including LSCs, without adversely affecting non-neoplastic normal mouse tissues or hematopoiesis. We propose that anti-ROR2 CAR T cells may offer therapeutic benefit for AML patients.