CAL-101 is a selective inhibitor of p110δ(IC50 : 2.5 nM; in cell-free assays); shown to have 40- to 300-fold greater selectivity for p110δ than p110α/β/γ, and 400- to 4000-fold more selectivity to p110δ than C2β, hVPS34, DNA-PK and mTOR.