CXCR4 and B-cell chronic lymphocytic leukemia: Ulocuplumab, an IgG4 mAb that inhibits the binding of CXCL12 to CXCR4 and induces caspase-independent apoptosis on multiple cell lines and primary samples from patients with AML, chronic lymphocytic leukemia (CLL), and multiple myeloma (108–110).