Rational design of new tumoractivated cytotoxic agents.
5-Fluorouracil (5-FU) plays an important role in the treatment of several tumor types, particularly colorectal cancer and breast cancer. Xeloda (capecitabine; 5'-deoxy-5-fluoro-N-[(pentyloxy)carbonyl-cytidine]) is a new rationally designed fluoropyrimidine carbamate. It is administrated orally and after absorption it is first metabolized to 5'-deoxy-5-fluorocytidine (5'-DFCR) by carboxylesterase from the liver and then converted to 5'-deoxy-5-fluorouridine (5'-DFUR) by cytidine deaminase from the liver and tumor tissues. Finally, thymidine phosphorylase (TP) converts 5'-DFUR to 5-FU. TP is more active in tumor tissues than in normal tissue. This tissue localization pattern results in preferential metabolism and generates higher levels of 5-FU in malignant tissue, thus enhancing efficacy but minimizing side effects. The tumor tissue selectivity was confirmed in a study of 19 patients with colorectal cancer. After Xeloda administration, concentrations of 5-FU were 2.5 times higher in the primary tumor compared with adjacent healthy tissue. Xeloda was highly active in human tumor xenografts. It was more active than 5-FU, 5'-DFUR and tegafur plus uracil (UFT) and had a better therapeutic index. Xeloda also demonstrated synergistic or additive activity when used in combination with cyclophosphamide, methotrexate, doxorubicin, paclitaxel and docetaxel. This may be in part a result of up-regulation of TP by the cytotoxic agents. Phase I and II clinical trials have shown that Xeloda is active across a range of tumor types, and phase III studies are ongoing.
Verweij
J
J
Department of Medical Oncology, Rotterdam Cancer Institute (Dr Daniel den Hoed Kliniek) and University Hospital, Rotterdam, The Netherlands. verweij@onch.azr.nl
D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D000069287:Capecitabine; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D005472:Fluorouracil / Q000031:analogs & derivatives; D006801:Humans
D000970:Antineoplastic Agents; D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil