This is a phase 2 randomized, placebo-controlled, double-blind, parallel-group multicenter study with an optional open-label extension (OLE) period. The purpose of this study is to evaluate the efficacy and safety of oral BT-11 compared to placebo in subjects with UC. This study includes 3 periods: induction, maintenance, and an optional OLE period.

Key Inclusion Criteria:

1. . Male and female subjects aged 18 to 75 years, inclusive.
2. . Diagnosis of UC for at least 3 months prior to screening.
3. . UC, as defined by a total Mayo Score of 4 to 10 inclusive at baseline with a MES 2 (confirmed by central reader).
4. . Able to participate fully in all aspects of this clinical trial.
5. . Written informed consent must be obtained and documented.

Key Exclusion Criteria:

1. . A diagnosis of CD, indeterminate colitis, or presence or history of the fistula with CD.
2. . Modified Truelove and Witts criteria (2: 6 bloody stools per day and one or more of the following: pulse > 90 bpm, temperature > 37.8°C, hemoglobin < 10.5 g/dl, or hs-CRP > 30 mg/I).
3. . Disease activity limited to distal 15 cm (proctitis).
4. . Treatment with an immunosuppressant (azathioprine, 6- mercaptopurine [6-MP]) within 25 days prior to randomization.
5. . Unable to attend study visits or comply with procedures.
6. . Concurrent participation in any other interventional study.
7. . Prior enrollment in the current study and had received study treatment.