Impact of sBCMA on teclistamab activity. (A) Plasma from patients with MM had significantly higher levels of sBCMA than plasma from healthy donors (average, 89.91 vs 8.04 ng/mL, respectively). (B) sBCMA levels were higher in patients with refractory MM compared with patients who were treatment (Tx) naive or had active MM. (C) Cytotoxicity. (D) T-cell activation potential of teclistamab was measured in the presence of various concentrations of sBCMA, APRIL, and BAFF.