Use of CD122+ natural killer cell precursors for superior anti-leukemia responses.

Acute Myeloid Leukemia (AML) is an aggressive blood cancer in adults. Intensive induction therapy successfully induces a complete response in up to 80% of the adult patients but a fraction of them is refractory or relapses. The fraction of non-responsive or relapsing patients is especially high amongst medically unfit and older patients, who cannot undergo aggressive chemotherapy treatment. Therefore, offering patients failing on first line intensive chemotherapy and medically unfit and older patients an effective treatment option for long-term control or even cure of disease represents a significant yet unmet clinical need. As a component of the innate immunity, NK cells have recently shown great promise for the treatment of patients with different malignancies. Here, we show that injection of human interleukin-2 (IL-2) complexes (IL-2cx) induce the de novo generation and massive expansion of NK cell precursors in vivo. Furthermore, IL-2cx-expanded NK cells exert effector functions with the capacity to control the growth of non-self MHC class I-deficient RMA-S lymphoma cells in vivo, while remaining tolerant towards MHC class-expressing self RMA cells. In an experimental setup mimicking the clinical case of refractory patients after intensive AML induction therapy, IL-2cx treatment mediated strong anti-AML responses following haploidentical bone marrow transplantation without the need for adoptive transfer of donor-derived or in vitro autologous expanded NK cells. Thus, this study demonstrates that IL-2cx immunotherapy allows the in vivo generation and expansion of functionally mature NK cells to achieve long-term response in AML paving the way to an effective treatment option.