A randomized, double-blind, placebo-controlled study to assess the efficacy and safety of LT-02 (delayed release phosphatidylcholine granules; administered orally via 1.6 g BID for up to 12 weeks) in subjects with active ulcerative colitis who are refractory to a standard dose of oral mesalamine therapy. Refractory to mesalamine is defined as active disease despite receiving at least ≥ 2.4g mesalamine (or equivalent dose) for at least 8 weeks with or without rectal 5-ASA.