 This is a Phase 2, multicenter, randomized, double-blind, placebo-controlled, parallel-group,study to evaluate the efficacy and safety of 2 doses of apremilast in subjects with active UC defined as a total Mayo score TMS of 6 to 11, with an endoscopic subscore 2. Treatment assignment will be stratified based on concomitant use of oral corticosteroids and previous exposure to immunosuppressants eg, 6-mercaptopurine 6-MP, azathioprine AZA, or methotrexate MTX.The number of subjects with previous exposure to immunosuppressants is targeted to comprise no more than 50 of the subjects enrolled, and no less than 30. 