The purpose of the HARMONY study is to assess the safety and efficacy of an investigational drug called HuZAF, in patients with moderate to severe Crohn's disease (CD). HuZAF is a humanized anti-Interferon-gamma (anti-IFN-γ) monoclonal antibody, which binds and blocks IFN-γ, a protein in the immune system that is involved in inflammation. Antibodies are proteins normally produced by our immune system to help fight off foreign substances. Scientists have been able to make therapeutic humanized monoclonal antibodies, similar to the antibodies in our bodies, to target diseases.

Participants will be randomized, assigned by chance, to one of five treatment groups consisting of: four groups differing in the amount of study drug given and one placebo group. The initial dose of study drug will be given intravenously, injected into a vein in the arm. Four weeks later, three subsequent doses of study drug will be given subcutaneously, through the skin, every four weeks for three doses. Patients will be followed for approximately six months after receiving their final dose.

• Patients 18-70 years old
• Patients with moderate to severe Crohn's disease
• Patients who have had Crohn's disease for at least 6 months
• Patients who have previously been treated for Crohn's disease