KLK3 and neoplasm: However, since a mono-epitopic interaction of the daratumumab variable regions with sCD38 has been demonstrated [63], a systemic type I hypersensitivity reaction is not expected to occur, as we have described in case of soluble tumor antigens PSA and the extracellular domain of HER2/neu (ECDHER2) bound to anti-HER2/neu IgE and anti-PSA IgE, respectively [23,25].