Definition

A preparation of human cytokine interleukin-21 (IL-21) primed, tumor-activated allogeneic human leukocyte antigen (HLA) haploidentical natural killer (NK) cells, with potential cytolytic and immunoregulatory activities. Allogeneic leukemia cells are genetically modified to express membrane-bound interleukin-21 (mbIL-21) on their cell surfaces. When human peripheral blood mononuclear cells (PBMCs) from an HLA-haploidentical donor are subsequently exposed to these cells, the donor PBMC differentiate into mature, highly cytotoxic NK cells, which are subsequently expanded in ex vivo culture. Upon infusion of the mbIL-21-expanded haploidentical NK cells, the NK cells target, lyse and destroy tumor cells. mbIL-21 promotes sustained ex vivo proliferation of human NK cells and enhances its cytotoxic activity.