An orally bioavailable specific oral inhibitor of the pan-class I phosphatidylinositol 3-kinase (PI3K) family of lipid kinases with potential antineoplastic activity. PI3K inhibitor BKM120 specifically inhibits class I PIK3 in the PI3K/AKT kinase (or protein kinase B) signalling pathway in an ATP-competitive manner, thereby inhibiting the production of the secondary messenger phosphatidylinositol-3,4,5-trisphosphate and activation of the PI3K signalling pathway. This may result in inhibition of tumour cell growth and survival in susceptible tumour cell populations. Activation of the PI3K signalling pathway is frequently associated with tumorigenesis. Dysregulated PI3K signalling may contribute to tumour resistance to a variety of antineoplastic agents.