Any substance that inhibits phosphatidylinositol 3-kinase (phosphatidylinositide 3-kinase), an enzyme that catalyzes the phosphorylation of the 3 position hydroxyl group of the inositol ring of phosphatidylinositol and functions as an intracellular signal transducer in cell growth, proliferation, differentiation, motility, survival and intracellular trafficking. Inhibition of phosphatidylinositol 3-kinase produces antiproliferative and antiangiogenic effects.