A phenylquinazolin derivative, idelalisib demonstrated 240- to 2500-fold selectivity for p110δ over the other class I PI3K isoforms in cell-based assays [71], exerted far greater pro-apoptotic activity in B-ALL and CLL cell lines compared with AML cells in a dose- and time-dependent fashion [71,72], and inhibited CLL cell chemotaxis toward CXCL12 and CXCL13 [73]. The gene discussed is CXCL13; the disease is B-cell chronic lymphocytic leukemia.