A compound for use in inhibiting endo-exonuclease activity and treating cancer, having the formula (I):wherein R3 is selected from the group consisting of lower alkyl, oxyalkyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, aminoalkyl or halogen； r4 is selected from the group consisting of hydrogen, lower alkyl, oxyalkyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, aminoalkyl or halogen；and wherein R5 is lower alkyl； or of formula (II):wherein R1 is selected from the group consisting of lower alkyl, oxyalkyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, aminoalkyl or halogen； r2 is selected from the group consisting of hydrogen, lower alkyl, oxyalkyl, cycloalkyl, aryl, heteroaryl, heterocycloalkyl, aminoalkyl or halogen； wherein R5 is a lower alkyl group that includes a linear carbon chain of at least two carbons connecting a first "O" and a second "O".
