Lumiliximab is a chimeric (primate/human) monoclonal antibody that targets CD23, the low-affinity receptor for immunoglobulin E (IgE). CD23 is expressed on malignant B cells in chronic lymphocytic leukemia (CLL) and on normal activated B cells. Lumiliximab was designed to bind to CD23 and induce apoptosis in CD23-positive B cells, potentially through direct signaling and antibody-dependent cellular cytotoxicity (ADCC). It was clinically evaluated, both as a single agent and in combination with chemotherapy (e.g., fludarabine and rituximab), for the treatment of relapsed or refractory CLL. However, its development has been discontinued.