Study to Evaluate the Safety and Efficacy of CJ-12420 in Patients With Erosive Esophagitis

Inclusion Criteria: * Aged between 20-70 * Diagnosed with Erosive Esophagitis by Esophagogastroduodenoscopy (EGD) and classified into LA Grade A to D within 14 days before randomization to treatment Exclusion Criteria: * Patients who cannot undergo EGD * Patients diagnosed with irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), or suspected IBS * Patients who took PPIs within 2 weeks prior to study drug administration * Long-term use of nonsteroidal anti-inflammatory drugs throughout the study * Clinically significant abnormal laboratory values during screening