A Trial of an Investigational Drug for the Prevention of Diarrhea Associated With Irinotecan/5FU/Leucovorin Chemotherapy in Previously Untreated Metastatic Colorectal Cancer

Other specific inclusion/exclusion criteria may apply. In order to determine eligibility, further examination by the investigator is necessary. Inclusion Criteria: * Age 18 years or older * Diagnosis of colorectal cancer or adenocarcinoma of the appendix * A tumor mass that can be measured * Resolution of all toxic effects of any radiotherapy or surgical procedures to NCI CTC grade less than or equal to 1 * Willingness and ability to comply with scheduled visits, treatment plan, and laboratory tests, and other study procedures Exclusion Criteria: * Women that are pregnant or lactating * Prior treatment with Irinotecan * Partial or complete bowel obstruction, known chronic malabsorption, or total colectomy or other major abdominal surgery that might result in substantial alteration in transit or absorption of oral medication * Administration of the last dose of any previous adjuvant therapy for colorectal cancer within 6 months previous to randomization * Current enrollment in another clinical trial * Administration of any prior systemic anticancer therapy for metastatic colorectal cancer