JNJ-64407564 can deplete MM cells when incubated with healthy human whole blood. (A-B) Human MM cells (H929) were incubated for 48 hours with whole blood from 6 different healthy donors at a 5:1 E/T ratio in the presence of various concentrations of JNJ-64407564. Percent cytotoxicity and T-cell activation were calculated as in Figure 2. (C) Healthy whole blood was incubated with JNJ-64407564 (black circle), GPRC5DxNull (white square), and NullxCD3 (black triangle) for 48 hours without exogenous target cells. (D) Binding of JNJ-64407564 to different cell populations in healthy human whole blood. The antibody was incubated with whole blood at 4°C for 30 minutes, and the binding profile was measured by flow cytometry (JNJ-64407564, red trace; IgG₄-PAA isotype control, gray filled). Binding was captured using a PE-labeled secondary antibody (HP6025; SouthernBiotech).