Definition

The fumarate salt form of vonoprazan, a pyrrole derivative and reversible potassium-competitive acid blocker (P-CAB), with potential antacid activity. Upon administration, vonoprazan specifically and competitively binds to the gastric hydrogen-potassium ATPase (H+/K+ ATPase) proton pump at or, more likely, near its potassium ion (K+) binding site and sterically inhibits K+ binding. This blocks the activation of the H+/K+ ATPase by K+, inhibits the proton pump and prevents gastric acid secretion, thereby lowering gastric acid levels.