Participants in Level 1 of the Top-Hold treatment group (IV infliximab at Week 0, 2, and 6 and every 8 weeks thereafter) that have not achieved response at Week 4 will receive IV infliximab 5 mg/kg at reduced intervals of 4 weeks (Level 2) starting with the Week 10 infusion. Participants suffering a flare after initial response in Level 1 will be switched to to Level 2. Participants that do not respond to treatment at reduced intervals after 3 infusions (12 weeks), or that develop a further flare after initial response at Level 2, will be switched to treatment with oral prednisolone + AZA (Level 3) following colonoscopy to confirm eligibility.