ISB 1342 in vitro potency is not affected by the concomitant or pretreatment with daratumumab. (A) Schematic representation depicting the MMoAK assay with concomitant treatment with ISB 1342 and daratumumab. (B-C) Cytotoxicity of the NCI-H929 MM cell line (B) and CD8⁺ T-cell response (C) after treatment with increasing doses of ISB 1342 and a fixed dose of daratumumab or monoclonal antibody control (mAb) in the presence of healthy PBMC (E:T, 5:1), normal human serum, and rhIL-2 for 48 hours. Data represent mean ± SD of EC₅₀ or the maximum response, from 12 donors in 3 independent experiments that were compared using an unpaired t test. (D) Schematic representation depicting the MMoAK assay of pretreatment with daratumumab followed by ISB 1342. (E-F) Cytotoxicity of the NCI-H929 MM cell line (E) and CD8⁺ T-cell response (F) in the presence of healthy PBMC (E:T, 5:1), normal human serum, and rhIL-2 with increasing doses of ISB 1342 for 48 hours after pretreatment with a fixed dose of daratumumab or monoclonal antibody control for 24 hours. Data represent mean ± SD of EC₅₀ or the maximum response from up to 9 donors in 3 independent experiments that were compared using an unpaired t test; ns, not significant.