The participation in this clinical study will last approximately 21 weeks with a 1 week screening period and a 12 weeks treatment duration. If the study doctor finds, that the patients disease has significantly improved he/she will enter a treatment free follow-up period of 8 weeks. In total the study consists of 5 to 6 clinical visits (V1 - V6) and 1 telephone follow-up call.

Inclusion Criteria:

• Men and women 18 years or older who have given written Informed Consent
• Patients with proven ulcerative colitis
• Active disease course for the last 6 weeks or longer with bloody diarrhea
• Patients with an inadequate response to a treatment with mesalazine or a documented intolerance to mesalazine.

Exclusion Criteria:

• Infectious colitis, including cytomegalovirus or Clostridium difficile induced colitis,
• Crohn's disease,
• Colitis due to other reasons than ulcerative colitis like known diverticulitis, radiation colitis, ischemic colitis, microscopic colitis, or indeterminate colitis,
• Treatment with other investigational medicinal product within 3 months prior to study entry