CXCR4 and B-cell chronic lymphocytic leukemia: Idelalisib (CAL-101, GS-1101) is the first orally competitive inhibitor of the PI3Kδ isoform, able to block survival and homing signals in CLL including those produced by the BCR and the chemokine receptors CXCR4 and CXCR5 (Brown et al., 2014; Lannutti et al., 2011).