Provided herein are substituted pyrimidine and triazine derivatives, including bicyclic pyrimidine derivatives, their pharmaceutical compositions, their preparation, and their use as agents or drugs for cancer therapy, either alone or in combination with radiation and/or other anticancer drugs. In one embodiment, the pyrimidine and triazine derivatives are morpholino-pyrimidine, morpholino-triazine, pyridyl-pyrimidine, and pyridyl-triazine derivatives which are selective irreversible inhibitors of the p110α isoform of PI3K.