Whereas compound 1 was non-toxic (GI50>300 μM), the GI50 (cell growth inhibition) ranged between 1 and 50 μM for the other APE1 inhibitors: compound 2=50 μM, compound 3=1 μM, compound 4=17 μM (glioma cell lines) and 20 μM (melanoma cell lines), compound 5=14 μM, compound 6=50 μM and compound 7=40 μM. Here, APEX1 is linked to central nervous system cancer.