A randomized, double-blind, double-dummy, active comparator, multi-centers, non-inferiority design clinical trial to assess the efficacy and safety of YYD601 in ERD patients (phase 3).

This phase 3 clinical trial is designed as randomized, active-comparator, double-dummy, multi-center for ERD patients, who take YYD601 40mg or Nexium 40mg for 8 weeks. Each part is assessed by 'LA grade' measured through the endoscopy, target goal is to confirm the non-inferiority of YYD601 40mg to Nexium 40mg.

Inclusion Criteria:

• A man or woman over 20 years old less than 70 years old.

• A man or woman who has experienced symptom (heartburn and acid regurgitation) within 7 days before Visit 1, meet below 1) or 2) criteria, who has been made diagnosis as Erosive esophagitis(LA grade A~D) measured through the endoscopy which is carried out within (-2W±D2)

  * Symptom (heartburn and acid regurgitation) is confirmed by RDQ.

  1. Experienced above 2 days in 1 week, Heartburn of acid regurgitation above the weakness.
  2. Experienced above 1 day in 1 week, Heartburn of acid regurgitation above the middle.

• A man or woman who has a full understanding of this clinical trial through the detailed explanation, agree in writing to participate in this trial.

Exclusion Criteria:

• Who has hyper sensitivity reaction about other drugs, ingredients, components of investigator product or compound of benzimidazole.
• Who has NERD
• Who get a diagnosis as a IBS within the last 3 months.
• Who have taken gastric acid secretion inhibitors including PPIs within 2 weeks before the endoscopy.
• Who have taken drugs about reflux esophagitis (H₂-receptor inhibitor (H2RA) Prostaglandin(PG), Antacid, Prokinetic acid etc.) above 2 times as an usual dose. (* refer to the Concomitant medication in text.)
• Who has been experienced the disease affecting the esophagus(Eosinophilic esophagitis, esophageal varices, cirrhosis, Virus or Fungal infection, Esophageal stricture, primary esophageal motility disorder and gastrointestinal bleeding). Or who has a history of radio therapeutics, freeze treatment about the esophagus.
• Who has clinically significant abnormal result of ECG.
• Abnormal result of Major arrhythmia, Multifocal PVS, 2 AV-blcok etc.
• Who has the Schatzki near the LES(lower esophageal sphincter) except the Barret's esophagus.