This double-blind, randomized, comparator-controlled Phase II study is designed to establish
the safety and efficacy of Zoenasa Rectal Gel compared to mesalamine enema in subjects with
left-sided ulcerative colitis, as measured by the modified ulcerative colitis disease
activity index (UCDAI), over 6 weeks of treatment. In this study, two cohorts of subjects
will receive either Zoenasa-1:4 (1.0g NAC; 4.0g 5-ASA) investigational drug enema therapy or
comparator mesalamine enema (4.0g 5-ASA). The study will enroll subjects randomized equally
into the 2 cohorts. Each cohort will enroll approximately 60 subjects. The two arms of the
trial will be enrolled concurrently in a randomized fashion.