ATR and cancer: Having observed a differential sensitivity to drugs that target DNA repair such as BEZ-235, a PI3K/ATR inhibitor believed to kill cancer cells primarily through ATR inhibition [25] and the CDK inhibitors THZ-2-49 and THZ-2-1020-1 (CDK’s regulate the DNA damage response [26]), we compared our previously published DNA repair score between the two subsets [5].