Activity of B-B4–DM1 on GFP⁺ human MM xenografts. (A) Flow cytometric analysis of OPM1^GFP+ cells indicates that these cells are highly fluorescent. (B) There were 5 animals injected with 5 × 10⁶ OPM1^GFP+ cells, monitored with whole-body fluorescence imaging for tumor development, and then treated with B-B4–DM1 (150 μg DM1/kg) for 3 consecutive days. Tumor sizes were determined directly by the fluorescent imaging of the GFP-expressing tumors. Error bars indicate SD. (C-D) Representative whole-body fluorescence images from a mouse treated with B-B4–DM1. (E-F) Negative images of the representative mouse. Figure shows a marked tumor regression 12 days after treatment.