Study of Treat to Target Versus Routine Care Maintenance Strategies in Crohn's Disease Patients Treated With Ustekinumab

The purpose of this study is to evaluate the efficacy of a treat to target strategy coupled with early endoscopic assessment versus a clinically driven (routine care) approach in achieving endoscopic response.

Study investigates benefit of treat to target maintenance treatment strategy versus routine care to test hypothesis that 'treat to target' ustekinumab (UST) maintenance treatment strategy coupled with early endoscopic assessment will result in higher endoscopic response rate after 48 weeks of treatment, compared to pragmatic maintenance treatment strategy. It consists of screening (5 weeks); treatment period (Week 0 to 48); extension period (Weeks 48 to 104) and safety follow up visit (16 weeks after last dose). Participants will be given an option to enter ultrasound sub-study to assess intestinal ultrasound (IUS) parameters indicating transmural changes in response to treatment with UST in participants with Crohn's disease. Study treatment will be unaffected by participation in sub-study which is optional for participants of main study.

Eligibility Criteria:
Inclusion Criteria:

Main Study:

* Have active, moderate to severe, ileal and/or colonic Crohn's disease, demonstrated by: baseline CDAI score of greater than or equal to (\>=) 220 and less than equal to (\<=) 450, and endoscopy with evidence of active Crohn's disease (defined as simple endoscopic score for Crohn's disease \[SES-CD\] score \>=3 excluding the contribution of the narrowing component score) obtained within the 5 week screening period. A prior endoscopy may be used only if obtained within 3 months prior to baseline (Week 0), in which case the prior endoscopy must be centrally read again and SES-CD calculated based on this second, centralized read-out
* Has had an inadequate response with, lost response to, was intolerant to, or had medical contraindications to either conventional therapy, or one previous biologic therapy approved for the treatment of Crohn's disease in the countries in which the study is conducted
* Are eligible according to tuberculosis (TB) infection screening criteria
* Must sign an informed consent form (ICF) or their legally acceptable representative if applicable must sign) indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study.

Sub-study:

* Be enrolled into the main study at a participating site
* Sign a separate ICF indicating that they understand the purpose of and procedures required for this sub-study and are willing to participate in the sub-study
* Satisfy all inclusion criteria and none of the exclusion criteria specified in the main study

Exclusion Criteria:

Main Study:

* Has complications of Crohn's disease such as symptomatic strictures or stenoses, short gut syndrome, or any other manifestation that might be anticipated to require surgery, could preclude the use of the Crohn's Disease Activity Index (CDAI) to assess response to therapy, or would possibly confound the ability to assess the effect of treatment with ustekinumab
* Currently has or is suspected to have an abscess. Recent cutaneous and perianal abscesses are not exclusionary if drained and adequately treated at least 3 weeks prior to baseline, or 8 weeks prior to baseline for intra-abdominal abscesses, provided there is no anticipated need for any further surgery. Participants with active fistulas may be included if there is no anticipation of a need for surgery and there are currently no abscesses identified
* Has had any kind of bowel resection within 6 months prior to baseline
* Has a draining (i.e, functioning) stoma or ostomy
* Has received more than one previous biologic therapy approved for the treatment of Crohn's disease in the countries in which the study is conducted

Sub-study:

* Obesity or other characteristics considered likely to preclude intestinal ultrasound (IUS) visualization of the affected bowel segment
* Normal bowel wall thickness (BWT) (that is, \<=2.0 millimeter \[mm\] for the terminal ileum; \<=3.0 mm for the colon) for all bowel segments at baseline (Week 0)