To evaluate the efficacy of IBI112 induction therapy in patients with moderate and severe active Ulcerative Colitis (UC) to achieve clinical remission.

This is a phase 2 randomized,double-blind, placebo-controlled study to evaluate the efficacy and safety of IBI112 induction and maintenance therapy in subjects with moderate to severe active ulcerative colitis

Inclusion Criteria:

1. Diagnosis of ulcerative colitis at least 3 months ago, including endoscopy evidence supporting UC and histopathological evidence supporting UC diagnosis;
2. Patients with moderate to severe ulcerative colitis, defined as modified Mayo Score ≥4 and endoscopic score ≥2;
3. Subject must have received at least one prior treatment or first use of a biological agent:

Exclusion Criteria:

1. Diagnosis of ischemic colitis, infectious colitis, radiation colitis, microscopic colitis, uncertain colitis, etc., or crohn's disease;
2. UC lesions were limited to rectum or involved colon < 15cm;
3. Evidence of toxic hirschsprung's disease was found during screening;
4. History or evidence of atypical hyperplasia of the colon, adenomatous polyps (not removed before entering the study) or gastrointestinal tumors;