 - The multicenter study plans to enroll seventy-two 72 subjects with moderate to severe active Crohns disease that is not controlled by corticosteroids, immunosuppressant e.g. methotrexate or purine metabolites or anti-inflammatory treatment e.g. 5-ASA. At baseline visit, if the eligibility of the subject is confirmed, the subject will be randomized 2:1 ratio to receive either AIN457 or placebo administered as a 2 hours intravenous infusion. A total of two infusions will be given on day 1 and day 22 respectively. 