NS-2028 is a specific inhibitor of soluble guanylyl cyclase. It inhibits purified bovine lung guanylyl cyclase in a concentration dependent and irreversible manner with IC50 values of 30 and 200 nM for basal and NO-stimulated enzymes, respectively. S-nitroso-glutathione-enhanced guanylyl cyclase activity in mouse cerebellum homogenates is inhibited by NS-2028 with an IC50 value of 17 nM, making it about 4.7 fold more potent than ODQ, which has an IC50 value of 80 nM for inhibition of soluble guanylyl cyclase in the same assay. NS-2028 does not inhibit particulate guanylyl cyclase or adenylyl cyclase.