B-B4–DM1 reduces MM tumor burden in SCID-hu mice. Mice were bled at the indicated time points after inoculation of 5 × 10⁶ cells from 2 different IgGk MM patients (A-B), monitored for changes in levels of human κ chain as an indicator of disease burden, and then treated with B-B4–DM1 (150 μg DM1/kg; n = 2) or control huC242-DM1 (150 μg DM1/kg; n = 2) for 3 consecutive days. Figure shows a marked reduction of κ levels after treatment with B-B4–DM1.