NK92 cells stably transfected with CD16 are efficient against multiple myeloma cells <i>ex vivo</i> and <i>in vivo</i> , especially if combined with daratumumab

Adoptive cell therapy and the use of monoclonal antibodies are two therapeutic modalities implemented in the treatment of multiple myeloma (MM). In this study, we combined the anti-CD38 therapeutic mAb daratumumab with different types of NK cells, leveraging the antibody-dependent cell-mediated cytotoxicity (ADCC) performed by these immune cells. Daratumumab was initially combined with activated and expanded NK cells (eNK), resulting in significant cytotoxic activity against human MM cell lines. As an alternative model to minimize the variability among donors of NK cells, the NK92 cell line was used, which showed greater cytotoxic activity than eNK cells against MM cell lines. However, since NK92 cells lacked CD16 receptor expression, they could not be used in combination with mAbs. To circumvent this, we performed a CD16 transfection on NK92 cells, generating the stable NK92-CD16 cell line. These cells were tested in combination with daratumumab against human MM cell lines with excellent results under various conditions, such as 2D and 3D cultures, even at very low effector-to-target ratios. NK92-CD16 cells were then tested in the presence of daratumumab against plasma cells from MM patients, with anti-myeloma activity even against cells from relapsed patients. <i>In vivo</i> experiments using MM xenografts or intravenous injection of MM cells in NGS mice, followed by treatment with NK92-CD16 cells in the presence or absence of daratumumab showed tumor regressions, especially in the second model, with nearly complete elimination of the MM cells when NK92-CD16 cells were combined with daratumumab.