The purpose of this study is to evaluate the effectiveness and safety of infliximab in Chinese patients with active ulcerative colitis (swelling and ulceration of large intestine and rectum).

This is a multicenter (study conducted at multiple sites), randomized (the study medication is assigned by chance), placebo controlled (placebo is an inactive substance that is compared with a medication to test whether the medication has a real effect in a clinical study), double blind (neither investigator nor patient knows the treatment that the patient receives), 2-arm (2 groups), parallel group (a clinical study comparing the response in two or more groups of participants receiving different treatments) study with infliximab in patients with active ulcerative colitis. The study consists of screening period (4 weeks prior to baseline [patient's medical status before any treatment or research is done] at Week 0), treatment period (Week 0 to Week 22) and follow up period (Week 26). Participants completing treatment till Week 22 and benefit from continued treatment (in the opinion of the investigator) may enter a study extension period from Week 30 until Week 58. Hundred participants will be randomized to 2 groups: Group 1 (50 participants receiving placebo) and Group 2 (50 participants receiving infliximab). Effectiveness and safety (physical examination, and a review of AEs, vital signs, laboratory analyses, and concomitant medications) will be evaluated at Week 8 and Week 26 and at Week 58 (for participants who enter extension phase). The maximum duration for participants in the main study is 26 weeks. The maximum duration for participants including study extension is 58 weeks. One of the specialized procedures used to calculate efficacy will be Mayo score which is calculated using the subscore (recorded in Mayo Diary Card by each participant) of the following 4 variables (1) stool frequency (scores ranging from 0 [normal number stools for this patient] to 3 [5 or more stools more than normal]), (2) rectal bleeding (scores ranging from 0 [no blood seen] to 3 [blood alone passed]), (3) endoscopic findings (scores ranging from 0 [normal or inactive disease] to 3 [severe disease ie, spontaneous bleeding and ulceration]), and (4) the physician's global assessment (scores ranging from 0 [normal] to 3 [severe disease]).

Inclusion Criteria:

• Has active ulcerative colitis of at least 3 months duration at screening with score of ≥2 on the endoscopy subscore of the Mayo score and baseline Mayo score of 6 to 12
• Concomitant medications: either have concurrent treatment with at least 1 of the therapies (eg, oral corticosteroids and 6-Mercaptopurine [6-MP]).
• Has to be eligible according to the tuberculosis (TB) eligibility assessment

Exclusion Criteria:

• Has severe extensive colitis or ulcerative colitis limited to only the rectum or to less than 20 cm of the colon
• Requires or required within 2 months prior to screening any surgery for active gastrointestinal bleeding, peritonitis (inflammation of abdominal lining), intestinal obstruction, or intra-abdominal or pancreatic abscess (a localized collection of pus in pancreas) requiring surgical drainage -Has severe fixed symptomatic stenosis (narrowing of the opening or hollow of any passage) of large or small intestine
• Has colonic obstruction or history within the 6 months prior to baseline
• Has colonic mucosal dysplasia (colonic mucosal cell maturation abnormality) or its history
• Has a history of extensive colonic resection (extensive partial removal of colon), lymphoproliferative disease (disease in which lymphocytes are produced in excessive quantities), demyelinating disease (disease of the nervous system)
• Has adenomatous colonic polyps (benign projecting mass of large intestine), stoma (opening either natural or surgically created connecting a portion of the body cavity to the outside environment), known infection of Human immunodeficiency virus (HIV), hepatitis B and C
• Has had treatment with cyclosporine, tacrolimus, sirolimus, or mycophenolate mofetil within 8 weeks prior to screening