CAL-101 is a highly selective and potent p110δ inhibitor with IC50 of 2.5 nM, is 40- to 300-fold more selective for p110δ relative to other PI3K class I enzymes (p110α, p110β, and p110γ; IC50 are 820, 565, and 89nM, respectively).CAL-101 is a highly selective and potent p110δ inhibitor (EC50=8 nM). Greater selectivity (400- to 4000-fold) is seen against related kinases C2β, hVPS34, DNA-PK, and mTOR, whereas no activity is observed against a panel of 402 diverse kinases at 10 μM. CAL-101 reduces PDGF-induced pAkt by only 25% at 10 μM. CAL-101 inhibits LPA-induced pAkt with an EC50 of 1.9 μM. CAL-101 blocks FcϵRI p110δ-mediated CD63 expression with an EC50 of 8 nM, whereas formyl-methionyl-leucyl-phenylalanine activation of p110γ is inhibited with an EC50 of 3 μM. Thus, in cell-based assays, CAL-101 has 240- to 2500-fold selectivity for p110δ over the other class I PI3K isoforms. CAL-101-induced apoptosis of chronic lymphocytic leukemia (CLL) cells is significant compare with vehicle treatment alone (P<0.001). CAL-101 induces selective cytotoxicity in CLL cells independent of IgVH mutational status or interphase cytogenetics.A significant reduction is observed in the CD11b+Ly6G+ neutrophils from brain homogenates of bothp110δD910A/D910A mice and CAL-101 (40 mg/kg, i.v.) post-treated mice.