Description_x000D_ Biochem/physiol Actions_x000D_ S4 is a potent and selective inhibitor against sulfamate carbonic anhydrase (CA) subtypes CAIX & CAXII (Ki = 2, 7, 546, 5600 nM against human CA XII, IX, II, and I, respectively). S4 selectively inhibits migration upon anoxia/hypoxia-induced CAIX expression in cancer cultures (% inhibition/conc./cell line = 54%/100 μM/WRO, 65%/33 μM/MDA-MB-231), while exhibiting no inhibitory effects under normoxia or among non-CAIX-expressing cells (HCT116 & RT112). Daily intraperitoneal injection (10 mg/kg) is reported to reduce the metastatic tumor burden in lungs of mice bearing orthotopic eGFP-MDA-MB-231 tumors in vivo.