• The primary endpoint is clinical response at Week 8 for Population 1. Clinical response is defined as a reduction in the CDAI score of = 25% and = 70 points.
  

• Clinical response following treatment with intravenous or subcutaneous C01275 for Population 1;Clinical response at Week 8 for Population 2;Serum C01275 profile and pharmacokinetic (PK) parameters of a single 5 mg/kg intravenous infusion, at 4 weeks
  

This study is a double-blind, placebo-controlled study. A total of approximately 120 patients will participate in this study in Canada, Belgium, and the United States. There will be 2 separate groups of patients evaluated in this study, Population 1 and Population 2. The 100 patients in this study who are considered Population 1 will be patients who still have active Crohn's disease despite treatment with standard Crohn's disease medications, including 5-ASA medications (for example: Pentasa®, Asacol®), corticosteroids (for example: prednisone) and/or other drugs known to suppress the immune system such as azathioprine, 6-mercaptopurine, methotrexate, infliximab or adalimumab (Humira®). The other 20 patients in the study are considered Population 2. These patients will receive infliximab (Remicade®) administered at the maximum dose described in the approved instructions for using infliximab (Remicade®). Infliximab (Remicade®) is another type of antibody that also works to decrease inflammation and works for many patients with moderate to severe Crohn's disease.

Population 1 will be randomized into 1of 4 treatment groups that receive either by an injection of 100 mg C01275 or placebo at weeks 0, 1, 2, 3, 8, 9, 10 and 11 or an infusion of 5 mg/kg C01275 or placebo at weeks 0 and 8. Subjects in Population 2 receive either an injection of 100 mg C01275 at weeks 0, 1, 2 and 3 or an infusion of 5 mg/kg of C01275 at week 0.