Potent and selective DNA-dependent protein kinase (DNA-PK) inhibitor (IC50 values are 14, 1700, 5000, >100000 and >100000 nM for DNA-PK, mTOR, PI 3-K, ATM and ATR respectively). Displays no activity at a range of 60 diverse kinases at 10 μM. Potentiates the effects of radiation, doxorubicin (Cat. No. 2252) and etoposide (Cat. No. 1226) in human tumor cell lines in vitro and etoposide in a human tumor xenograft model in vivo.