This is a multi-center trial to test the safety, efficacy and tolerability of alicaforsen (ISIS 2302), a new type of drug called an antisense drug, in patients with mild to moderate active Ulcerative Colitis (UC). Alicaforsen is designed to reduce the production of a specific protein, called ICAM-1, a substance that plays a significant role in the increase of inflammation and is likely to be involved in inflammatory bowel diseases such as ulcerative colitis. The ISIS 2302-CS22 study will examine the effects of one of two dosages of alicaforsen delivered by enema over a six-week period as compared to an active control, mesalamine enema (The probability of receiving the alicaforsen formulation is 2:1). The primary objective of this study is to evaluate the percentage reduction in DAI at Week 6.

Inclusion criteria

Patients must meet the following criteria at screening to be eligible for enrollment:

• Age greater than or equal to 18 years

• Diagnosis of ulcerative colitis of at least 6 months duration

• Current left-sided flare, defined as activity in the colon 5-50 cm from the anal verge, extending at least 15 cm proximal to the anal verge and confirmed by endoscopic evaluation within 14 days of baseline visit.

• Baseline DAI score of 4-10 including abnormal endoscopic score

• On at least one or more of the following treatments for ulcerative colitis prior to baseline visit:

  1. Stable background oral mesalamine therapy for greater than or equal to 30 days, and/or
  2. Stable background mercaptopurine for greater than or equal to 60 days prior to baseline, and/or
  3. Stable azathiprine therapy for greater than or equal to 60 days prior to baseline

• Written informed consent prior to performing screening evaluations.

Exclusion criteria

Patients who meet any of the following criteria at screening are not eligible for enrollment:

• Bowel stricture, toxic megacolon, colonic dysplasia, adenoma or carcinoma
• Uncontrolled hematologic, renal, hepatic, metabolic, psychiatric, CNS, pulmonary or cardiovascular disease, or sufficient level of disease that could interfere with the patient's ability to comply with protocol participation
• Enteric pathogens or presence of Clostridium difficile toxin in stool
• History of colon resection
• Major surgical procedure within one month of baseline visit
• Steroid or mesalamine enema within 14 days of baseline visit
• Systemic steroids (including ACTH) within 30 days of baseline visit
• Tumor necrosis factor-alpha (TNF-α) inhibitor treatment within 90 days of baseline visit
• Non-steroidal anti-inflammatory agents (NSAIDs), including cyclooxygenase-2 (COX-2) inhibitors, within 14 days of baseline visit
• Methotrexate, cyclosporin or thalidomide within 90 days of baseline visit
• Any active infection currently requiring treatment
• Malignancy within 5 years except for squamous cell or basal cell cancers of the skin
• Current infectious, ischemic, or immunological disease with gastrointestinal involvement
• ISIS 2302 treatment within 12 months of baseline visit
• History of allergy to mesalamine
• Treatment with an investigational or off-label drug within 90 days of screening or currently in long-term follow up for another investigational treatment protocol