- At least a consecutive 90 day course of azathioprine or 6-mercaptopurine (6 MP) prior to Baseline, with a dose of azathioprine >= 1.5 mg/kg/day or 6 MP >= 1 mg/kg/day (rounded to the nearest available tablet formulation), or a dose that is the highest tolerated by the participant (e.g., due to leukopenia, elevated liver enzymes, nausea) during that time. Participant was to be on a stable dose for at least 28 days prior to Baseline.