This study consists of a 2-week placebo-controlled double-blind inter-group efficacy study in moderate to severe refractory ulcerative colitis (UC) patients followed by a maximum of 12-week open-label efficacy and safety study in responders.

Inclusion Criteria:

• Moderate to severe refractory UC patients
• Disease activity: more than 4 times of stool a day, bloody stool, moderate to severe endoscopic finding
• Steroid resistance or dependence to meet at least one of the following condition:no efficacy with more than 40mg/day or 1mg/kg/day of steroid over at least 1 week, no efficacy with 30-40mg/day of steroid over at least 2 weeks,exacerbation along with steroid reduction

Exclusion Criteria:

• Mild or fulminant type
• Renal failure patients, hepatic failure patients
• Patients taking 6-mercaptopurine, cyclosporin or other immunosuppressants within 12 weeks prior to entry
• Patients who received LCAP or GCAP within 2 weeks prior to entry
• Patients who changed the dose of steroid or started steroid within 2 weeks prior to entry.
• Patients who changed the dose of steroid or started steroid within 1 week prior to entry in case they received more than 40 mg/ day or 1mg/kg/day of steroid just before the study.