Daratumumab, a CD38 antagonist, is a human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody that binds CD38 expressed on the cell surface in a variety of hematological malignancies, including myeloma, lymphomas, and leukemias, as well as on other cell types and tissues with various expression levels. Here, CD38 is linked to plasma cell myeloma.