A Study of the Efficacy and Safety of Risankizumab in Participants With Crohn's Disease

The study consists of 4 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 intravenous 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, another AbbVie risankizumab Crohn's disease study, or participants who responded to induction treatment in Study M16-006 or Study M15-991 with no final endoscopy due to the Covid-19 pandemic. Additional objectives are to further investigate long-term efficacy and tolerability of risankizumab; * Sub-study 4 (Open-label On Body Injector (OBI) administration and long-term extension study) to evaluate patient-reported outcomes, efficacy, safety, tolerability, and pharmacokinetics of risankizumab administered via OBI in participants who are receiving maintenance treatment with risankizumab. * OL CTE to ensure uninterrupted care in accordance with local regulations until risankizumab is commercially available for participants who completed Sub-study 3, Sub-study 4.