Translating TriPRIL CARTs into clinical application. (A) Luciferase-based cytotoxicity assays of TriPRIL CARTs against MM.1S myeloma in the presence of sBCMA, sTACI, and sAPRIL. Cells were cocultured at various E:T ratios, as indicated on the x-axis. The concentrations of sBCMA, sTACI, and sAPRIL added to the assay are denoted in the graph legend. Luciferase activity of targets was measured after 8 hours. Bars indicate means ± SEM of triplicates from 1 normal donor; †closest to median concentration reported in BM of MM patients; ‡closest to median concentration reported in PB of MM patients. (B-C) Flow cytometry-based cytotoxicity assay of TriPRIL CARTs or UTDs from the same donors against primary myeloma cells from r/r MM patients. T cells and MM bone marrow mononuclear cells (BMMCs) were cocultured at a 1:1 ratio for 24 hours. (B) Bar graphs depict mean percentage of MM cell lysis ± SD of 3 representative MM patient cells cocultured each with T cells from 3 allogeneic normal donors. (C) Scatter plot indicating mean percentage of MM cell lysis ± SD of combined data set of 7 MM patients and 4 normal T-cell donors. *P < .05; ***P < .001, by 2-tailed Student t test.