Treatment of Crohn's Disease

The study consists of 3 sub-studies, as follows: - Sub-study 1 (Randomized, double-blind, placebo controlled study) to evaluate the efficacy and safety of risankizumab versus placebo as maintenance therapy in participants with moderately to severely active Crohn's disease (CD) who responded to risankizumab induction treatment in Study M16-006 or Study M15-991. - Sub-study 2 (Randomized, exploratory maintenance study) to evaluate the efficacy and safety of two different dosing regimens for risankizumab as maintenance therapy in participants who responded to induction treatment in Study M16-006 or Study M15-991. - Sub-study 3 (Open-label, long-term extension study) to evaluate long-term safety of risankizumab in participants who completed Sub-study 1, Sub-study 2 or the Phase 2, open-label extension study M15-989.