(5) The first study showing an in vivo antitumor effect due to CA IX inhibition was from Neri’s group [42], followed shortly thereafter by similar studies from different laboratories, on diverse models and cancer types, which demonstrated that sulfonamide/sulfamate [42,43,44,45,46] or coumarin [47] CA IX/XII inhibitors have a profound effect in inhibiting the growth of the primary tumors and the metastases expressing CA IX/XII. Here, CA9 is linked to cancer.