Immunotherapeutic strategies are emerging as promising therapeutic approaches in 
multiple myeloma (MM), with several monoclonal antibodies in advanced stages of 
clinical development. Of these agents, CD38-targeting antibodies have marked 
single agent activity in extensively pretreated MM, and preliminary results from 
studies with relapsed/refractory patients have shown enhanced therapeutic 
efficacy when daratumumab and isatuximab are combined with other agents. 
Furthermore, although elotuzumab (anti-SLAMF7) has no single agent activity in 
advanced MM, randomized trials in relapsed/refractory MM have demonstrated 
significantly improved progression-free survival when elotuzumab is added to 
lenalidomide-dexamethasone or bortezomib-dexamethasone. Importantly, there has 
been no significant additive toxicity when these monoclonal antibodies are 
combined with other anti-MM agents, other than infusion-related reactions 
specific to the therapeutic antibody. Prevention and management of infusion 
reactions is important to avoid drug discontinuation, which may in turn lead to 
reduced efficacy of anti-MM therapy. Therapeutic antibodies interfere with 
several laboratory tests. First, interference of therapeutic antibodies with 
immunofixation and serum protein electrophoresis assays may lead to 
underestimation of complete response. Strategies to mitigate interference, based 
on shifting the therapeutic antibody band, are in development. Furthermore, 
daratumumab, and probably also other CD38-targeting antibodies, interfere with 
blood compatibility testing and thereby complicate the safe release of blood 
products. Neutralization of the therapeutic CD38 antibody or CD38 denaturation 
on reagent red blood cells mitigates daratumumab interference with transfusion 
laboratory serologic tests. Finally, therapeutic antibodies may complicate flow 
cytometric evaluation of normal and neoplastic plasma cells, since the 
therapeutic antibody can affect the availability of the epitope for binding of 
commercially available diagnostic antibodies.