Endocopic remission rates of moderate to severe ulcerative colitis are low. Biologics including Vedolizumab, infliximab, and adalimumab are effective in induction and maintainence of ulcerative colitis. The role of 5-ASA in promoting a higher rate of endocsopic remission is unclear. We aim to evaluate the efficacy of combination of 5-ASA and biologics in treating ulcerative colitis.

Inclusion Criteria:

1. Patients with moderate and severe ulcerative colitis;
2. Subjects were above 18 years old and below 80 years;
3. Indications of 5-ASA or biological treatment;
4. According to the clinical symptoms, ulcerative colitis was diagnosed by endoscopic changes, pathological manifestations. The disease activity of UC was assessed according to the modified Mayo scoring system (modified Mayo: 6~12 for patients with moderate to severe ulcerative colitis);
5. If the subject is a woman, a pregnancy test at baseline is needed to exclude pregnancy. Female patients must follow the contraceptive recommendations of the project;
6. Subjects must be able and willing to provide written informed consent and comply with the requirements of this study protocol.

Exclusion Criteria:

1. No indications of 5-ASA or biological treatment;
2. ulcerative colitis patients who had previously undergone a partial colectomy;
3. Patients who are unable to use 5-ASA for a long time;
4. Patients with severe, progressive, or uncontrolled kidney, liver, blood, or endocrine diseases or symptoms;
5. Presence of infected persons, Patients with a contraindication to the use of biological agents such as C. difficile infection or other intestinal pathogens, active tuberculosis or intestinal tuberculosis infection, human immunodeficiency virus (HIV) infection, active hepatitis B or hepatitis C (defined as: ① HBV: hepatitis B surface antigen (HBs Ag) positive (+), Or patients with positive for hepatitis B core antibody (HBcAb) and the qualitative test results of HBV deoxyribonucleic acid (DNA) polymerase chain reaction (PCR) meet the detection criteria; ② HCV: Any patient with an anti-HCV antibody (HCV Ab) -positive patient with a detectable HCV ribonucleic acid (RNA);
6. Patients with a history of gastrointestinal dysplasia, or dysplasia on any biopsy performed on endoscopy, excluding low-grade dysplasia lesions; known history of lymphoproliferative disease (including lymphoma), or signs and symptoms (e. g., lymphadenopathy and / or splenomegaly); patients with current or previous malignancy;
7. Has been involved in other clinical studies.