A sulfonamide derivate and carbonic anhydrase inhibitor with potential antineoplastic activity. Methazolamide inhibits tumor-associated carbonic anhydrase IX (CAIX), which may result in increased cell death in hypoxic tumors. As a hypoxia-inducible transmembrane glycoprotein, CAIX catalyzes the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions, helping to maintain acidification of the tumor microenvironment and enhance resistance to cytotoxic therapy in some hypoxic tumors.