• To evaluate the clinical response of ustekinumab vs placebo at Week 6 as measured by the reduction from baseline in CDAI.
  

• To evaluate the efficacy of ustikenumab in inducing clinical remission, fistula response and mucosal healing and to obtain data to support the selection of a maintenance dose for continued clinical development.
  

In Crohns disease there is inflammation (changes in body tissue which normally happen during injury or infection) and or ulceration (open sores) in the intestines.This occurs because the immune system (the part of the body that fights off infection) has an abnormal and overactive response against the intestine and bowel tissues of the body. Crohns disease is usually treated with medications that either directly decrease inflammation or decrease the general activity of the immune system to improve the diarrhea, abdominal pain, and other symptoms of Crohns Disease. Ustekinumab antibodies (natural substances made by your immune system to stick to and help remove foreign materials in your body that cause diseases) have been created to stick to and block the activity of two of the immune substances thought to cause abnormal inflammation of Crohns disease. Patients who are eligible and who have received Remicade, Humira, or Cimzia and failed or been intolerant to one of these drugs will be randomized to either active drug (ustekinumab) or placebo. All patients will be randomized (like flipping a coin) at week 0 to be in one of 4 groups. At week 0 the study drug will be given by IV administration and at weeks 8 and 16 by subcutaneous injection. There will be 11 study visits in total and the study will continue until week 36. Blood and stool samples will be collected and studied, questionnaires to check on how you are doing in terms of your disease will be completed, an Electrocardiogram (EKG) obtained, safety evaluations conducted and diary cards distributed to be completed during the entire study. One of 4 groups: Grp 1-placebo, Grp 2-active drug 1mg/kg IV, Grp 3-active drug 3mg/kg IV, Grp 4-active drug 6mg/kg IV. Based on the clinical response status at Week 6, patients from Grps 2, 3 and 4 will be re-randomized at week 8 to receive either placebo or 90 mg SC at both weeks 8 and 16 and patients from Grp 1 will receive placebo at Week 8 and Week 16 or a 270 mg SC injection at Week 8 and 90 mg SC at Week 16.