The Purpose of This Study is to Evaluate the Efficacy and Safety of 627 in the Treatment of UC

Inclusion Criteria: 1. Able to understand and comply with the requirements of the study protocol, and sign the written informed consent form (ICF). 2. Male or female subjects aged 18-75 years old when signing the ICF. 3. Subjects must have been diagnosed with UC for at least 3 months prior to randomization. 4. Moderate to Severe Active Ulcerative Colitis (UC). 5. Inadequate or lost response, intolerance to one or more therapies, or corticosteroid dependence. 6. Female subjects of childbearing potential and male subjects (and their female partners) must use highly effective contraception from the screening period through at least 6 months after the last dose. The subjects must have no plans for pregnancy, sperm donation, or oocyte donation during the same period (from screening through at least 6 months post-last dose). Exclusion Criteria: 1. History of severe opportunistic infection within 2 months prior to screening or randomization that remains not adequately controlled. 2. Receiving protocol-prohibited treatments prior to screening or randomization. 3. Presence of any laboratory test abnormalities during screening and/or determination by the investigator that enrollment in the study may pose uncontrollable safety risks to the subject. 4. Positive hepatitis B test result, positive hepatitis C virus antibody (HCV Ab), positive human immunodeficiency virus antibody (HIV Ab), or positive serum Treponema pallidum antibody (TP Ab) during screening, as specified in the protocol. 5. History of clinically significant cardiovascular and cerebrovascular diseases within 6 months prior to screening. 6. History of any malignancy within 5 years prior to screening or currently active malignancy. 7. Allergy to the investigational medicinal product, any of its components, or excipients. 8. History of alcohol or substance abuse within 6 months prior to screening. 9. Undergone major surgery within 6 months prior to screening or planned major surgery during the study period. 10. Blood donation or significant blood loss within 4 weeks prior to screening. 11. Participation in any drug clinical trial within 3 months prior to screening or within 5 half-lives of the investigational drug (whichever is longer). 12. Vaccination with live/attenuated live vaccines within 4 weeks prior to screening or planned vaccination during the study period. 13. Pregnant or lactating female subjects. 14. Other conditions deemed unsuitable for trial participation by the investigator.