CA9 and cancer: In particular, for solid tumors, they havea fundamental role in maintaining the acidity of the tumor environment., Specifically, two isozymes, CA IX and CA II, have been prominently associated with cancer.−, ,  Currently, many sulfonamide-based drugs are clinically used forthe treatment of different pathological conditions,−, , ,  because these drugs are bable to inhibit CAs thanksto their ability to displace ligands at the zinc catalytic site.