- 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.