If a participant experiences a second flare after initial response at Week 4 (Level 1), the participant will enter treatment Level 2. In Level 2, participants will receive a prednisolone induction at the same effective dose as previously used in Level 1 + maintenance treatment with oral azathioprine (AZA) at a dose of 2.0-2.5 mg/kg/day. Participants that do not respond to this treatment at Level 2 or that develop a further flare after initial response at Level 2 will enter Level 3 and will receive treatment with IV infliximab following endoscopy to confirm treatment eligibility.