Zastaprazan (JAQBO®) is a next-generation potassium-competitive acid blocker being developed by Onconic Therapeutics, a subsidiary of Jeil Pharmaceutical, for the treatment of acid-related diseases. Zastaprazan binds directly to proton pumps in a competitive manner to reduce gastric acid secretion, allowing for a quick onset of action. On 24 April 2024, zastaprazan received approval in South Korea for the treatment of erosive gastroesophageal reflux disease (GERD). Zastaprazan is also undergoing phase III development for the treatment of gastric ulcer and for the prevention of non-steroidal anti-inflammatory drug (NSAID)-induced peptic ulcer. This article summarizes the milestones in the development of zastaprazan leading to this first approval for erosive GERD.