Daratumumab, a human IgGκ monoclonal antibody targeting CD38 with a direct on-tumor [5–8] and immunomodulatory [9–11] mechanism of action, demonstrates greater cytotoxicity of multiple myeloma (MM) cells ex vivo compared with analogs of other CD38 antibodies [12], and is approved for MM treatment in many countries worldwide [13, 14]. This evidence concerns the gene CD38 and plasma cell myeloma.