Although we have reported preclinical work, as well as clinical trials, that arm ATC with (a) anti-CD3 x anti-HER2 BiAb (HER2 BATs) for the treatment of breast and prostate cancer (5, 6), and (b) anti-CD3 x anti-CD20 BiAb (CD20 BATs) for the treatment non-Hodgkin's lymphoma (7) and MM in combination with stem cell transplantation, specific targeting to MM lines by CS1-BATs has not been shown. Here, ERBB2 is linked to prostate cancer.