1-(5-(1H-indol-5-yl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl)-N-methylmethanamine (KFP-H008), a novel and potent potassium-competitive acid blocker for the treatment of acid secretion related diseases, has not been reported previously. In this study, we demonstrated that KFP-H008 inhibits basal acid secretion, 2-deoxy-d-glucose- (2DG-) stimulated gastric acid secretion in rats. KFP-H008 blocked histamine-stimulated acid secretion in rats and heidenhain pouch dogs and reversed acid output in isolated gastric perfusion under histamine stimulation. In all the animal experiments, KFP-H008 exerted a more effective, potent and longer-lasting inhibitory action in comparison with lansoprazole, a proton pump inhibitor (PPI) commonly used in clinic. KFP-H008 inhibited H+-K+-ATPase activity both at pH 6.5 and pH 7.5, and was unaffected by pH. The inhibitory action was reversible and was achieved in a K+-competitive manner. Furthermore, KFP-H008 did not affect Na+-K+-ATPase activity, thus exhibiting high selectivity, which is different from PPIs. In all, KFP-H008, a novel potassium-competitive acid blocker, may provide new option for the patients with acid-related diseases and provide longer-lasting inhibitory action than drugs commonly used in clinical treatment.