A Study of MDX-1100 in Subjects With Active Ulcerative Colitis

Inclusion Criteria: * Subjects with active UC on either 5-ASA,corticosteroids,azathioprine(AZA) and or/6-mercaptopurine(6-MP); * Mayo score of 6 to 10 points with moderate to severe disease on endoscopy * Subjects on the following medications; 1. prednisolone ≤ 20 mg daily (or equivalent) (dose must be stable for at least 2 weeks prior to study drug administration) 2. 5-ASA (dose must be stable for at least 4 weeks prior to study drug administration) 3. AZA or 6-MP (dose must be stable for at least 3 months prior to study drug administration) 4. Rectal steroids or 5-ASA (must have been stable for at least 4 weeks prior to study drug) Exclusion Criteria: * Anti-TNF therapy within 8 weeks before study drug administration * Contraindication to colonoscopy or sigmoidoscopy * Primary or secondary immunodeficiency * Autoimmune disease besides UC, with the exceptions of Sjogren's syndrome or hypothyroidism * History of malignancy, excluding adequately treated and cured basal or squamous cell of the skin, or cervical carcinoma in situ * Evidence of acute or chronic infection * Clinically significant disease requiring medication