6. Patient is not using concomitant medication for treatment of underlying Crohn's disease with the following exceptions: concomitant medications may include: 1) Oral or rectal sulfasalazine, mesalazine (5-ASA), or mesalazine derivative, if receiving it for >6 weeks and if receiving the same dose for at least 4 weeks; 2) Oral prednisone up to 15 mg/day, or budesonide if receiving it for >4 weeks and if receiving the same dose for at least 4 weeks; and 3) Azathioprine (up to 2.5 mg/kg daily) or 6-mercaptopurine (up to 2 mg/kg daily) if receiving it for >3 months and if receiving the same dose for at least 8 weeks prior to Baseline.