The purpose of this study was to test the efficacy of expanded natural killer cells (eNKs) as a treatment against multiple myeloma (MM) cell lines and MM patient bone marrow aspirates. The cytotoxic effect of eNKs was studied alone and in combination with daratumumab, anti-CD38 monoclonal antibody approved for use in multiple myeloma patients. In multiple myeloma cell lines, eNKs were found to have a dramatic cytotoxic effect against the cells. For the patient samples, when eNKs were harvested during the optimum expansion period, they produced a cytotoxic effect against the MM cells. Daratumumab was also effective against some of the patient samples. However, when combined, eNKs and daratumumab produced a greater percent of specific cell death than both separately, on all cells tested. Combination therapy maximizes the effect of each individual treatment. This important finding supports the possible use of combination eNKs with daratumumab therapy against multiple myeloma in further trials
