Phathom Pharmaceuticals, Inc. is a late clinical-stage biopharmaceutical company. The Company is focused on developing and commercializing treatments for gastrointestinal (GI) diseases. Its product candidate, vonoprazan, is an oral small molecule potassium competitive acid blocker (P-CAB). It is developing vonoprazan as an agent in the treatment of gastroesophageal reflux disease (GERD) and in combination with antibiotics for the treatment of Helicobacter pylori (H. pylori) infection. Vonoprazan accumulates in the secretory canaliculus where the proton pumps are present in their active state. Vonoprazan binds to proton pumps in both their inactive and active states and remains in the secretory canaliculus where it continues to inhibit acid secretion over an extended period.