APE1-IN-1 is a potent and blood-brain barrier (BBB) penetrant apurinic/apyrimidinic (AP) endonuclease 1 (APE1) inhibitor with an IC50 value of 2 μM. APE1-IN-1 can potentiate the cytotoxicity of the alkylating agents Methylmethane sulfonate and Temozolomide to cancer cells[1].