Preclinical targeting of human acute myeloid leukemia and myeloablation using chimeric antigen receptor–modified T cells

Abstract

Key Points• Targeting of CD123 via CAR-engineered T cells results in rejection of human AML and myeloablation in mouse models.Many patients with acute myeloid leukemia (AML) are incurable with chemotherapy and may benefit from novel approaches. One such approach involves the transfer of T cells engineered to express chimeric antigen receptors (CARs) for a specific cell-surface antigen. This strategy depends upon preferential expression of the target on tumor cells. To date, the lack of AML-specific surface markers has impeded development of such CARbased approaches. CD123, the transmembrane a chain of the interleukin-3 receptor, is expressed in the majority of AML cells but is also expressed in many normal hematopoietic cells. Here, we show that CD123 is a good target for AML-directed CAR therapy, because its expression increases over time in vivo even in initially CD123 dim populations, and that human CD123-redirected T cells (CART123) eradicate primary AML in immunodeficient mice. CART123 also eradicated normal human myelopoiesis, a surprising finding because anti-CD123 antibody-based strategies have been reportedly well tolerated. Because AML is likely preceded by clonal evolution in "preleukemic" hematopoietic stem cells, our observations support CART123 as a viable AML therapy, suggest that CART123-based myeloablation may be used as a novel conditioning regimen for hematopoietic cell transplantation, and raise concerns for the use of CART123 without such a rescue strategy. (Blood. 2014;123(15):2343-2354

Antibody darts on target for acute myelogenous leukemia

“…Thus among the strategies under development, DARTs may have superior qualities over BiTEs. When compared with chimeric T cell constructs (CARs) DARTs have the advantage that the requirement for in vitro T cell gene transduction is avoided (13,14). To optimize the physical properties of the chimeric antibody for AML treatment the antibody design ensures that the CD123/DART is more avid for the leukemic cell than the T cell, ensuring that T cells are preferentially bound by antibodies that have reached their target.…”

“…Recombinant technology is used to link the variable heavy and light domains of two antibodies as a single 55 kDa polypeptide chain. In clinical (12); (II) chimeric antigen receptor T cell using anti CD123 to target myeloid cells (13,14) (not yet in clinical trial); (III) single polypeptide chain bispecific engager antibodies (BiTE) recognizing CD3 and CD3 (15) or CD123 (16); (IV) double polypeptide chain dual affinity retargeting antibodies (DART) recognizing CD3 and CD123 (17,18). AML, acute myelogenous leukemia; VL, light chain; VH, heavy chain; CD3z, zeta chain of CD3; Co-stim, costimulatory molecules.…”

Recent advances in T‐cell immunotherapy for haematological malignancies

“…(Gill et al 2014, Mardiros et al 2013) Mardiros et al (2013) reported potent efficacy of two CD123-targeted CARs generated using a lentiviral vector and targeting two distinct scFvs binding two discrete epitopes. These CD123-directed CAR T-cells could be generated from both healthy donors and patients, contained both CD8+ and CD4+ T-cells, and effectively killed CD123+ AML cell lines and autologous blasts.…”

“…While persistence of CD123 CAR T cells (correlating with long-term animal survival) was only observed in the Penn study utilizing the 41BB-CD3ζ construct, significant on-target off–tumour toxicity of myeloid cells, B cells and platelets occurred. (Gill et al 2014) These results have led to recently opened clinical trials, which will not only evaluate safety and efficacy of these constructs, but also will provide insight into the long-term effects of CD123-CAR T-cells on haematopoiesis (NCT02159495; NCT02623582).…”

Adoptive transfer of T cells transduced with a chimeric antigen receptor to treat relapsed or refractory acute leukemia: efficacy and feasibility of immunotherapy approaches

“…Additionally, CD123-CAR-T cells exhibited anti-leukemic activity in vivo in a xenogeneic AML model. Gill and colleagues suggested that CAR-T123-based myeloablation might be used as a novel conditioning regimen for hematopoietic cell transplantations (Gill et al, 2014).…”