The study will combine a new investigational drug with standard anti-cancer drugs for the treatment of advanced colorectal cancer. The standard and approved treatment for colorectal cancer is to undergo chemotherapy with a combination of irinotecan (also known as CPT-11, Camptosar), 5-fluorouracil (also known as 5-FU), and leucovorin (also known as LV). This is known as the triple therapy. One of the major side effects of CPT-11/5-FU/LV chemotherapy treatment is diarrhea. The purpose of this research study is to see whether adding this investigational drug to the standard treatment for advanced colorectal cancer can reduce the amount of diarrhea a patient experiences. This study will also determine if adding the investigational drug to triple therapy has a positive effect on tumors.

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