Selection and Efficacy-Influencing Factors of First-Line Biologic Agents in Moderate-to-Severe Ulcerative Colitis

This study is looking at the real-world effectiveness of two types of biologic medications — infliximab (IFX) and vedolizumab (VDZ) — as first-line treatments for people with moderate to severe ulcerative colitis (UC), a chronic inflammatory bowel condition. Researchers want to understand which drug works best and for whom. **You may be eligible if...** - You are between 18 and 70 years old - You have been diagnosed with ulcerative colitis (not infection-related or cancer-related bowel disease) - Your UC is rated moderate to severe based on a clinical scoring tool called the Mayo score - You will not be using other treatments (medications or surgery) that would interfere with evaluating the biologic drug **You may NOT be eligible if...** - You have unstable blood circulation (hemodynamic instability) - You have significant liver or kidney impairment - You are allergic to infliximab or vedolizumab - You have gastrointestinal cancer - You have active infections (including hepatitis B, hepatitis C, TB, HIV, or syphilis) - You are pregnant or breastfeeding - You cannot attend regular follow-up visits Talk to your doctor to see if this trial is right for you.