Indisulam, also known as E7070, is a carbonic anhydrase inhbitor, is also a novel synthetic sulfonamide that targets the G1 phase of the cell cycle.. The potential antitumor activity of Indisulam was discovered through optimization of the structure-activity relationships of a series of sulfonamide structures. Indisulam causes a blockade in the G1/S transition through inhibition of the activation of both cyclin-dependent kinase 2 and cyclin E. Preclinical studies with Indisulam showed activity in multiple tumor types, most prominently in colon and lung cancer.