BCMA is expressed on human and cynomolgus monkey BM plasma cells but not on B cells. Flow cytometry histogramsdepicting cell surface BCMA expression levels on plasma cells and CD20⁺ B lineage cells from human (A) and cynomolgus monkey (B) BM. Concentrations of anti-BCMA antibody tested and corresponding mean fluorescence intensity (MFI) values are indicated. (C) Flow cytometry pseudocolor plots representing BCMA expression on cynomolgus monkey PB total B cells (TotB), naive B cells (NB), resting memory B cells (RMB), and activated memory B cells (AMB), stained with isotype control (upper panels) or BCMA antibody (lower panels). Plots are representative of 2 donors. (D) T-cell activation shown as CD69⁺ percentage of CD8⁺ cells (left panel) and autologous depletion of CD40⁺ B cells shown as percentage of control (right panel) in cynomolgus monkey whole blood incubated with a negative control HLE BiTE molecule, tool CD20 BiTE molecule, or AMG 701 for 48 hours. Each line represents 1 donor.