Treatment Effect According to Timing of Administration of DWP14012 40 mg

Subjects will provide written informed consent for study participation and then undergo appropriate screening. Subjects who meet the inclusion criteria and none of the exclusion criteria will be randomized in a 1:1 ratio to either before meal group or after meal group. Subjects will be stratified into two groups according to Los Angeles classification grades (LA grades) A/B or C/D, as determined by upper gastrointestinal (GI) endoscopy. Subjects will visit the site at Week 2 for endoscopic assessment. Subjects whose mucosal breaks have completely healed will be prematurely withdrawn and considered to have reached end of treatment. Subjects whose mucosal breaks have not healed will continue to receive IPs for an additional 2 weeks and will visit the site for endoscopic assessment at Week 4.

• DWP14012 (Drug), also known as fed state: DWP14012 40 mg, orally, once daily just after a meal up to 4 weeks
• DWP14012 (Drug), also known as fasted state: DWP14012 40 mg, orally, once daily before a meal up to 4 weeks

Primary outcomes

• healing rate at 4 week [4 week]: Cumulative healing rate of erosive esophagitis at 4 week by endoscopy

Secondary outcomes

• healing rate at 2 week [2 week]: Cumulative healing rate of erosive esophagitis at 2 week by endoscopy

Sex: All, ages: 19 Years to 75 Years

Inclusion Criteria:

* Adults between 19 and 75 years old based on the date of written agreement
* Those who have been diagnosed with erosive esophagitis of LA Grade A-D on the upper gastrointestinal endoscopy
* Those who experienced symptoms of heartburn or acid regurgitation within the last 7 days

Exclusion Criteria:

* Those who have undergone gastric acid suppression or gastric, esophageal surgery
* Those who with clinically significant liver, kidney, nervous system, respiratory, endocrine, hematologic, cardiovascular, urinary system disease