Inclusion Criteria:

• A clinical diagnosis of acute diverticulitis
• Female patients must be postmenopausal (at least 1 year without spontaneous menses) or surgically sterile or have a negative urine pregnancy test and practice acceptable contraception (e.g., abstinence; oral, intramuscular, or implanted hormonal contraception [at least 3 months prior to enrollment]; 2-barrier methods [e.g., condom, diaphragm, or spermicide]; intrauterine device or verbal report of partner with history of non-reversed vasectomy)
• Willing and able to participate in the study and provide a signed informed consent

Exclusion Criteria:

• Presence of diverticular complications (e.g., fistula, abscess, obstruction, stenosis);
• Active or recent history (within 6 months) of a peptic ulcer;
• Prior history of irritable bowel syndrome (IBS), as determined by the Investigator;
• History of major abdominal surgery (as determined by the Investigator);
• History of GI surgery within 3 months of diagnosis of acute diverticulitis;
• History of immunocompromising disease, human immunodeficiency virus (HIV) infection, or acquired immunodeficiency syndrome (AIDS);
• If female patient, active or recent history of endometriosis or dysmenorrhea;
• Received a dose of a product that contains, or is metabolized to, mesalamine by any route within 4 weeks before the screening visit;