Clinical Scale Generation of Functional Human Natural Killer Cells From Umbilical Cord Blood CD34-Positive Cells for Immunotherapy.

Abstract 2666

Poster Board II-642

Immunotherapy based on natural killer (NK) cell infusions is a potential adjuvant treatment for many cancers. Such therapeutic application in humans requires large numbers of functional NK cells that have been isolated and expanded using clinical grade protocols. We established an extremely efficient cytokine-based culture system for ex vivo expansion of NK cells from hematopoietic stem and progenitor cells from umbilical cord blood (UCB). Systematic refinement of this two-step system using a novel clinical grade medium resulted in a therapeutically applicable cell culture protocol. The use of GBGM culture media in a clinical applicable protocol allows the ex vivo expansion and differentiation of CD34+ cells to more than 4-logs into CD56+CD3- NK cells with very high purity. These ex vivo-generated CD56+ cell products contain NK cell subsets expressing CD94/NKG2A and KIR as well express high levels of activating NKG2D and NCRs. Functional analysis showed that CD56+ cell products containing alloreactive NK cells efficiently kill myeloid leukemia and melanoma tumor cells as well as primary acute myeloid leukemia (AML) cells. We have currently translated the protocol to clinical scale production using a closed cell culture bioprocess. CD34+ selection from frozen UCB samples (n=9) using the CliniMACS device was optimized and the selection resulted in a CD34+ enrichment with a mean number of 2,2 ± 1,6 × 10⁶ cells and a purity of 71 ± 14 % CD34+ cells. Validation experiments using the CliniMACS selected cells showed, that the generation of sufficient numbers of NK cells without contaminating T-cells or B-cells under a closed system process is feasible. The cell cultures using bags show a mean expansion of 1273 ± 506 fold (range 759–1770 fold, which generated 8,6×10⁸ − 1,9×10⁹ NK cells from cord blood-derived CD34+ cells within maximal 6 weeks of culture. The mean purity of the NK cell product was 71 ± 9 % (range 63–80%) of the total cells in the bag cultures. These NK cell products will be used for immunotherapy in elderly AML patients. This study is a phase I dose escalation study in a series of 12 AML patients who have successfully achieved CR (<5% blasts in the bone marrow) after standard intensive chemotherapy.