Crohn's & Colitis

Inclusion criteria:

• - A history of Crohn's disease or fistulizing Crohn's disease of at least 3 months' duration, with colitis, ileitis, or ileocolitis, confirmed at any time in the past by radiography, histology, and/or endoscopy - Initially responded to ustekinumab induction therapy, administered according to the local label, followed by secondary loss of response (LoR) to ustekinumab.

Secondary LoR to ustekinumab is defined as active disease at study baseline, proven by a Crohn's Disease Activity Index (CDAI) score of greater than or equal to (>=) 220 and <=450 with at least one of the following: Elevated C-reactive protein (CRP) (>3.0 milligram per liter [mg/L]); and/or elevated Fecal calprotectin (FeCa) >250 milligram per kilogram [mg/kg]); and/or endoscopy (performed within the 3 months before baseline) with evidence of active Crohn's disease during the current disease flare (that is [i.e.], ulcerations in the ileum and/or colon)

• - Participants receiving either oral 5-aminosalicylic acid (5-ASA) compounds, oral corticosteroids (for example {e.g.}, prednisone, budesonide) at a prednisone-equivalent dose of <=40 mg/day or <=9 mg/day of budesonide, antibiotics used as the primary treatment of Crohn's disease, or conventional immunomodulators (i.e., azathioprine [AZA], 6-mercaptopurine [6-MP], or methotrexate [MTX]) are permitted providing the doses indicated are stable before baseline or have been discontinued before baseline within the protocol defined durations

  Exclusion Criteria:

  - 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 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 before baseline (or 8 weeks before 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 - Any kind of bowel resection within 6 months or any other intra-abdominal surgery within 3 months before baseline - A draining (i.e., functioning) stoma or ostomy - Received any of the following prescribed medications or therapies within a specified period including any off-label use of ustekinumab, additional IV re-induction or shortened frequency of subcutaneous dose administration, after the initial weight-tiered based IV induction dose of ustekinumab

This study compares the efficacy and safety of a single weight-tiered based IV re-induction dose of approximately 6 mg/kg ustekinumab versus continuing with regular SC q8w 90 mg ustekinumab administration. It consists of screening (5 weeks); treatment period (Week 0 to 24); and safety follow up visit (20 weeks after last dose). The primary hypothesis is that a single IV re-induction dose of ustekinumab is superior to continuing with regular SC q8w maintenance treatment as measured by clinical response after 16 weeks of treatment. Study assessments will include Crohn's disease activity index (CDAI), video ileocolonoscopy, patient-reported outcomes (PROs), laboratory evaluations, biomarkers, review of concomitant medications and adverse events (AEs), and evaluation of serum concentrations of study agent as well as development of antibodies to study agent. All participants will be randomly assigned to receive either ustekinumab IV re-induction or regular SC q8w 90 mg ustekinumab injection at baseline in a double dummy design. No participants will be treated with placebo only.