Capecitabine is a non-cytotoxic fluoropyrimidine carbamate derivative, an oral precursor of the cytotoxic compound 5-fluorouracil (5-FU). Capecitabine is activated by several enzymatic steps. Final conversion to 5-FU occurs under the action of thymidine phosphorylase in tumor tissue, as well as in healthy tissues of the body, usually at low levels. In human cancer xenograft models, capecitabine has demonstrated a synergistic effect in combination with docetaxel, which may be due to an increase in thymidine phosphorylase activity by docetaxel.