Nepaprazole Na is the salt form of Nepaprazole Free Base, also known as TY-11345, is a proton pump inhibitor potentially for treatment of gastric ulcer. TY-11345 potently inhibited H+/K(+)-ATPase activity in isolated rabbit gastric mucosal microsomes; and the inhibitory effect was enhanced under weak acid conditions, the IC50 (concentrations that inhibit the enzyme activity by 50%) being 5.8 microM and 9.9 microM at pH 6.0 and pH 7.4, respectively. TY-11345 should be useful for the clinical treatment of peptic ulcer diseases.