This study, which is designed as a multicenter, open-label, single-arm, phase 3b clinical trial, is intended to evaluate the efficacy and safety of vedolizumab in biologic-naïve Korean patients with moderate-to-severe bowel disease.~The study is conducted with a single arm, and the subjects to be recruited consist of 30 patients with Crohn's disease and 30 patients with ulcerative colitis (considering dropout rate of 20%).~The total period after the subject enrollment is 54 weeks, and a total of 10 visits are made with screening, baseline, 2 weeks, 6 weeks, 14 weeks, 22 weeks, 30 weeks, 38 weeks, 46 weeks, and 54 weeks.~Crohn's disease (CD): If a subject does not respond to vedolizumab 300mg iv 0, 2, and 6 weeks for induction, an additional dose of vedolizumab 300 mg will be given at week 10. On the other hand, Maintenance therapy should be continued every 8 weeks from week 14 in responding patients, and for some patients who have experienced a decrease in their response, it can be given every 4 weeks.The maximum dosing period is 54 weeks.~Ulcerative colitis (UC): If a subject responds to vedolizumab 300mg iv 0, 2, and 6 weeks for induction, maintenance therapy should be continued every 8 weeks from week 14, and for some patients who have experienced a decrease in their response, it can be given every 4 weeks.The maximum dosing period is 54 weeks.
If subjects voluntarily consent to participation in the study, those who are finally determined to be eligible for the study after whether all of the inclusion criteria and none of the exclusion criteria are met is checked will receive the study drug. Efficacy and safety will be evaluated at baseline, baseline, 2 weeks, 6 weeks, 14 weeks, 22 weeks, 30 weeks, 38 weeks, 46 weeks, and 54 weeks.