Provided is a method for treating a disease associated with target cells expressing CD 138 comprising: administering to a subject, in particular a human subject, in need thereof an immunoconjugate comprising at least one engineered targeting antibody targeting CD138 expressing cells, and at least one effector molecule, wherein said engineered targeting antibody is functionally attached to said effector molecule to form said immunoconjugate, wherein preferably at least a part of the engineered targeting antibody confers lgG4 isotype properties, wherein the immunoconjugate is administered in a multiple dose regimen comprising at least two doses, wherein the aggregate dose administered within an active treatment cycle is an aggregate maximum tolerable dose (AMTD) or a fraction of the AMTD and wherein said AMTD and/or said fraction exceeds the dose resulting in dose limiting toxicity (DLT) when the immunoconjugate is administered as a single dose, including as part of a multiple single dose regimen and/or exceeds the maximum tolerable dose (MTD) when the immunoconjugate is administered as a single dose, including as part of a multiple single dose regimen within said active treatment cycle.
