The IC50 values for the established MM cell lines and primary CD138+ MM cells were about 30-60 nM, while it was more than 5000 nM in the CD19+/CD138- B cells, indicating that GBT is selectively potent in malignant MM cells rather than in the normal cells, thereby limiting the side effects of GBT treatment. Here, CD19 is linked to Miyoshi myopathy.