ACAR causes cytolysis of primary myeloma cells in vitro. (A) CD138-selected BM-derived primary myeloma cells from 5 patients were cultured in media alone (labeled “Tumor alone”), with allogeneic NT T cells or T cells transduced to express ACAR-H.2A.RQR8 or ACAR-CD8.2A.RQR8. Patients are identified by the numbers allocated in Figure 1B and supplemental Table 1. Tumor antigen densities of BCMA and TACI are indicated (ABC). Relative number of viable tumor cells at D+3 are shown. Cytokine release was determined at D+1 by ELISA, and T-cell numbers after 7 days of coculture with or without tumor cells were determined by staining for RQR8 transgene by using FACS. (B) Summarized tumor kill (percentage cytolysis determined in relation to viable tumor cells on coculture with NT T cells) (i), cytokine release (ii), and T-cell expansion (iii). (C) ACAR-H– transduced PBMCs from 3 donors were cocultured 1:4 with MM.1s, U266, or CD138-selected primary BM-derived tumor cells from 3 further patients. Effectors and targets were cultured in media alone, 150 µg/mL of anti-BCMA antibody (S307118G03), or the equivalent concentration of IgG2a control: BCMA and TACI expression on targets (i) and target kill at 48 hours by FACS (ii). Mean ± SEM, *P < .05 in comparison with control by paired t test. ns, not significant.