An orally bioavailable inhibitor of class I PI3K isoforms, potently blocking, in vitro, both p110α (IC50 = 52 nM) and p110β (IC50 = 166 nM); much less effectively inhibits the class III PI3K Vps34 and mTOR and has no effect on PI4Kβ and several other kinases; inhibits tumor growth in vivo.