Clinical-grade, large-scale, feeder-free expansion of highly active human natural killer cells for adoptive immunotherapy using an automated bioreactor

Background aims. Natural killer (NK) cell-based adoptive immunotherapy is a promising approach for the treatment of cancer. Ex vivo expansion and activation of NK cells under good manufacturing practice (GMP) conditions are crucial for facilitating large clinical trials. The goal of this study was to optimize a large-scale, feeder-free, closed system for efficient NK cell expansion. Methods. Peripheral blood mononuclear cells (PBMCs) from healthy donors and myeloma patients were cultured for 21 days using flasks, cell culture bags and bioreactors. Final products from different expansions were evaluated comparatively for phenotype and functionality. Results. Significant NK cell expansions were obtained in all systems. The bioreactor yielded a final product rich in NK cells (mean 38%) ensuring that a clinically relevant cell dose was reached (mean 9.8 x 10