Can a new pill outperform standard care for ulcerative colitis?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Male or female, aged 18 years or above. * Patients diagnosed with active ulcerative colitis at multiple centers including Sir Run Run Shaw Hospital, Zhejiang University School of Medicine (lead center), defined as having a modified Mayo Score (without physician's global assessment) ranging from 3 to 6 points. If ES = 1 point, RBS ≥ 1 point is required. Patients with proctitis are allowed to be enrolled, provided that the proctitis lesion extends more than 5 cm from the anal verge. * Treatment-naive patients at initial visit accounting for no more than 30% of the total sample size; Or patients who have previously received conventional pharmacological therapy (including mesalazine, corticosteroids and immunosuppressants) but have inadequate response, intolerance (excluding mesalazine), or non-standard treatment (including but not limited to insufficient dosage or duration of oral 5-ASA, corticosteroids or immunosuppressants, which shall be determined by the investigator based on individual patient conditions). The proportion of patients receiving combined glucocorticoid therapy at baseline shall not exceed 30% of the total sample size. * Voluntarily participate in this study and sign the informed consent form. Exclusion Criteria: * Subjects with contraindications to etrolimod or mesalazine. * Previously treated with etrasimod or other biologics and small-molecule drugs. * Patients are currently receiving full-dose conventional therapy yet still have active disease, including any one of the following: Treatment with mesalazine (≥3 g/day) for ≥8 weeks; Or continuous treatment with prednisone ≥40 mg/day or equivalent dose for ≥3 days (intravenous administration); Or continuous oral treatment with prednisone \>20 mg/day or equivalent dose for ≥2 weeks; or oral azathioprine (≥0.75 mg/kg/day), 6-mercaptopurine (≥0.5 mg/kg/day), methotrexate (≥15 mg/week) for ≥3 months. * Recent history of acute severe ulcerative colitis (ASUC), toxic megacolon, etc. * Patients with stomas or patients with UC scheduled for inpatient surgical intervention. * Pregnant and lactating women. * Vulnerable groups excluding the elderly and illiterate, including people with mental illnesses, individuals with cognitive impairment, critically ill patients, etc. * Other circumstances where researchers consider participation in this study inappropriate.