CAL-101 is a cell-permeable inhibitor of the PI3K catalytic subunit p110δ (IC₅₀ = 2.5 nM) that displays 40- to 300-fold selectivity against other PI3K class I enzymes (IC₅₀s = 820, 565, and 89 nM for p110α, β, and γ, respectively). It has also been shown to inhibit the chemotaxis of chronic lymphocytic leukemia cells and to downregulate the secretion of chemokines triggered by B-cell receptor signaling.