180 patients suffering from active Crohn's disease with evidence of mucosal ulceration will be evaluated when taking GLPG0634 or matching placebo once daily in addition to their stable background treatment. The population will include 50% anti-TNF naïve patients and 50% of subjects previously exposed to anti-TNF.~The study will consist of 2 parts, with total treatment duration of 20 weeks. Randomisation in Part 1 will be stratified according to subject's previous anti-TNF exposure, C-reactive protein (CRP) level at Screening and oral corticosteroid use at Day -1. However, at Week 10, subjects will be re-randomized automatically and stratified according to the subject's clinical response (reduction of Crohn's Disease Activity Index (CDAI) of 100 points), previous anti-TNF exposure and corticosteroid use at Day -1 to receive GLPG0634 200 mg q.d., 100 mg q.d. doses, or matching placebo q.d. in a blinded fashion. In Part 2, all will continue the study until Week 20.~As efficacy parameters, the ability to achieve clinical response or remission, endoscopic response & remission as well as mucosal healing with GLPG0634 given once daily compared to placebo will be evaluated after 10 weeks of treatment. In subjects who achieved clinical remission at Week 10, maintenance of the remission will be assessed during Part 2 of the study.~During the course of the study, patients will also be examined for any side effects that may occur (safety and tolerability), and the amount of GLPG0634 present in the blood (Pharmacokinetics) as well as the effects of GLPG0634 on disease- and mechanism of action-related parameters in the blood and stool (Pharmacodynamics) will be determined. Also, the effects of different doses and dose regimens of GLPG0634 administration on subjects' quality of life will be evaluated.
180 patients suffering from active Crohn's disease with evidence of mucosal ulceration will be evaluated for improvement of disease activity (efficacy) when taking GLPG0634 or matching placebo once daily for 20 weeks in addition to their stable background treatment.~During the course of the study, patients will also be examined for any side effects that may occur (safety and tolerability), and the amount of GLPG0634 present in the blood (Pharmacokinetics) as well as the effects of GLPG0634 on disease- and mechanism of action-related parameters in the blood and stool (Pharmacodynamics) will be determined. Also, the effects GLPG0634 administration on subjects' quality of life will be evaluated.