As a preliminary step towards determining the radiosensitizing capacity of ATR inhibitors for orthotopic GB induced by primary glioma initiating cells (GIC) in animal models, we have investigated the pharmacokinetics of NVP-BEZ235 (also called Dactolisib or BEZ235), a multiple PI3K, and mTOR and ATR inhibitor and of AZD6738, an orally active and selective ATR inhibitor. The gene discussed is ATR; the disease is central nervous system cancer.