Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), also called phosphatidylinositide 3-kinases, are a family of signal transducer kinases involved in cell growth, proliferation, differentiation, motility, survival and intracellular trafficking. There are four separate classes of PI3K (named Class I, Class II, and so on). Because PI3K overactivity is observed in various cancers types, it is a much sought-after target for potential drug therapies. The drugs wortmannin, a fungal metabolite that irreversibly inhibits PI3K, and LY294002, a small-molecule reversible inhibitor, are commonly used for research purpose but are too broad to be useful therapeutics. Several PI3K inhibitors with higher specificities are undergoing trials for treatment of a wide range of cancer types. Idelalisib, a small molecule inhibitor to PI3K delta, was recently approved by the FDA for treatment of leukemia and two types of lymphoma.