Gamma Delta T Cells for Acute Myeloid Leukemia

Pediatric acute myeloid leukemia (AML) represents 15%-20% of all pediatric acute leukemias. Despite advances in treatment, 30% of all pediatric AML patients will suffer from relapse and 5-10% will die due to complications or treatment side effects. Chimeric antigen receptors (CAR), which combine antibody recognition of a tumor antigen to a T-cell signaling domain, can prospectively offer therapeutic benefits than other therapies as it targets tumor-specific antigens. One of the drawbacks of current CAR trials is use of autologous T cells, which is limiting due to cost, manufacturing failures, time delay, and limited efficacy. Therefore, there is a need to develop allogeneic cell therapies, which besides being cost effective can provide a ready to use "off the shelf" product for multiple patients. Gamma delta (γδ) T cells are an ideal substrate for allogenic CAR therapy because they play a key role in tissue homeostatsis, cancer immunesurveillance and have been successfully administered in patients without causing GvHD. However, there are limitations in expansion methods using Zoledronic acid, thus we now report an improved approach to propagate γδ T cells with a polyclonal TCR repertoire to clinical meaningful numbers. We have adapted K562 cell line, which is a natural target for γδ T cells to express CD32, CD64, CD86, CD137L along with IL15/IL15Rα fusion protein (membrane-bound IL-15; mIL15), to provide activation and proliferation signals to expand γδ T cells. γδ T cells isolated from normal donor peripheral blood when cultured on K562 feeder cells resulted in efficient proliferation with 2.9x10³ fold expansion of γδ T cells over 28 days. The resulting population was >99% TCR γδ⁺ T cells representing all three Vδ repertoire (Vδ1, Vδ2, Vδ3). Furthermore polyclonal γδ T cells expressed central memory markers, were able to generate an inflammatory response by production of proinflammatory cytokines such as IFN-γ and efficiently lysed a panel of AML cell lines (HL60, MOLM13, TF1) while sparing autologous or allogeneic B cells. Specificity of γδ T cells can be further augment by introduction of a CAR moiety, and we are currently working to redirect the specificity of γδ T cells towards an AML-specific target antigen. Our data have implication for generation of an "off the shelf" CAR T cell product for treatment of various pediatric cancers.

Mahadeo:Jazz Pharmaceuticals: Other: PI; Atara Biotherapeutics: Consultancy; Jazz Pharmaceuticals: Consultancy; Atara Biotherapeutics: Other: PI.