Phase 2a Study to Evaluate Suppression of 5-Fluorouracil -Induced Mucositis by TK112690

Patients expected to receive a 500 mg/m2 of Leucovorin by iv \& 500 mg/m2 of Fluorouracil (5FU) by iv bolus for their Colorectal Cancer. The patients will receive a one-hour infusion of TK-90 or equivalent TK-90 placebo depending on randomization at 5 hours \& 11 hours post 5-FU iv bolus. This treatment cycle will continue weekly for 6 weeks. The TK112690 dose will be 45 mg/kg. * 24 patients will be randomized equally into 2 different groups: TK-90 treated or TK-90 placebo treated. * Screening must be completed within 2 weeks. * The treatment period for the study is 6 weeks. * Study follow-up will be scheduled post two weeks of completion of last dose of Chemotherapy \& TK-90 * Blinding: The study will be partially blinded. The patient and investigator as well as site personnel will be blinded as to whether TK-90 or TK-90 placebo is administered. The CRO, sponsor, and site pharmacist will know whether the patient was administered active drug or TK-90 placebo