In vitro activity: IPI-3063 is a PI3K p110δ selective compound with an IC50 of 0.1 nM in p110δ-specific cell-based assays and cellular IC50 values for the other class I PI3K isoforms are at least 1,000-fold higher. IPI-3063 potently reduces mouse B cell proliferation, survival, and plasmablast differentiation.

Kinase Assay: Human recombinant PI3K-α, PI3K-β, PI3K-δ, and PI3K-γ are used. Phosphatidylinositol 4,5 bis phosphate (diC8-PtdIns(4,5)P2) is used. PI3K-α, β, and δ are heterodimers consisting of full length p110α, p110β, or p110δ catalytic subunit and the p85α regulatory subunit. PI3K-γ is a monomer of the p110γ catalytic subunit. Samples of kinase (10 nM-α, β, and δ; 20 nM-γ) are incubated with IPI-3063 for 30 min at room temperature in reaction buffer (15 mM HEPES pH 7.4, 20 mM NaCl, 1 mM EGTA, 0.02% Tween 20, 10 mM MgCl2, 0.2 mg/mL bovine-γ-globulins) followed by addition of ATP/diC8-PtdIns(4,5)P2 mixture to give final concentrations of 3 mM ATP and 500 μM diC8-PtdIns(4,5)P2. Reactions are incubated at room temperature for 2 h, with PI3K activity is assessed. Plates are read on plate reader in luminescence mode.

Cell Assay: Purified mouse B cells are incubated for 48 h in either B-cell activating factor (BAFF) or interleukin-4 (IL-4) with various concentrations of IPI-3063 and IPI-443.