Study of the Safety and Efficacy of Zoenasa® Versus Mesalamine Enema in Subjects With Left-Sided Ulcerative Colitis

Inclusion Criteria:

• Male and female subjects are eligible if they are ≥ 18 years of age and ≤ 64 years.

• They have a documented history of idiopathic ulcerative colitis based on endoscopicand/or histologic findings involving the left side of the colon, with mild to moderateactive disease.

• Eligible subjects will have a documented history of ulcerative colitis, and a modifiedUCDAI score of 4-10, inclusive, with a Physician's rating of disease score of 2 pointsor less (mild or moderate active ulcerative colitis), rectal bleeding score of 1 ormore (based on subject diary), and mucosal appearance score (based on endoscopy) of 1point or more at baseline.

• Laboratory data:

• White blood cell count between 4.0 - 12.0 K/mm3

• Platelet count: 150 - 500 K/mm3

• Hemoglobin > 10.0 g/dL

• Total bilirubin < 1.5 mg/dL

• Aspartate aminotransferase < 100 u/dL

• Alanine aminotransferase < 100 u/dL

• Alkaline phosphatase < 250 u/dL

• Blood urine nitrogen < 40 mg/dL

• Creatinine < 1.5 mg/dL

• Satisfies one of the following:

• Female subjects of childbearing potential must have a negative urine pregnancy test atscreening; surgically sterile, post-menopausal, abstinent, or patient or partner agreeto use a medically appropriate form of birth control from screening to until 1 monthafter the last dose of study medication.

• Male subjects must be surgically sterile, abstinent, or patient or partner compliantwith a contraceptive regimen from screening to until 1 month after the last dose ofstudy medication.

• They are able to understand and sign a written informed consent form, which must beobtained prior to initiation of study procedures.

Exclusion Criteria:

• They have documented history of proximal or universal ulcerative colitis, proctitis oractive proctitis confined to 15cm or less from the anal verge.

• They demonstrate signs and symptoms of fulminant colitis, bowel stricture, toxicmegacolon, an anticipated need for blood transfusion for gastrointestinal bleeding, ordemonstrate evidence of peritonitis.

• They receive a Physician's rating of disease severity as part of the modified UCDAI of 3 (severe disease) or an aggregate score of 11 or greater.

• They have shown prior documented history of evidence of high grade dysplasia on biopsyfrom endoscopic examinations.

• Their stool contains enteric pathogens or Clostridium difficile toxins.

• They have a history of recurrent Clostridium difficile infection.

• They have prior history of biologic therapy within the previous 4 years.

• They have received systemic steroids or immunosuppressants within the previous 4weeks.

• Treatment in the last 14 days that included antibiotic, antifungal, antiparasiticmedications, or rectally administered steroids (e.g. Cortenema®) or mesalamine enema (Rowasa®).

• Treatment in the last 7 days that included mesalamine (5-ASA) via oral administration (e.g. Asacol®, Lialda®, balsalazide, etc).

• They have a history of cancer (defined as malignancy within 5 years except forsquamous cell or basal cell cancers of the skin), asthma, or bronchospasm.

• Positive pregnancy test or lactating subjects.

• There is evidence of chemical substance abuse.

• They have had repeated anti-inflammatory drug treatment (longer than 3 days at dosesthat exceed those available without a prescription) within the previous 7 days (withexception of aspirin at doses of 325mg/day or less for prophylaxis of cardiacdisease), or initiated new non-steroidal anti-inflammatory (NSAID) treatment withinthe last 30 days.

• They have a known allergy to N-acetylcysteine or mesalamine, or have a history ofserious AEs related to their use (including, but not limited to pancreatitis orhepatitis).

• They have a history of failure to retain enemas.

• Other clinically significant diseases that could interfere with the protocolcompliance appear. These would include clinically important hematological, renal,hepatic, metabolic, psychiatric, central nervous system (CNS), pulmonary orcardiovascular disease.

• Use of any investigational medication within the previous 90 days.

• Any condition which the study physician judges to preclude safe participation in thestudy or to confound the evaluation of the study outcome.