Capecitabine-d11 is intended for use as an internal standard for the quantification of capecitabine by GC- or LC-MS. Capecitabine is a prodrug form of 5-fluorouracil .1 It is converted to 5-FU via several enzymatic steps beginning in the liver and ending with conversion in tumor tissue by thymidine phosphorylase, an enzyme that is more concentrated in tumor tissue compared with normal tissue. Capecitabine is cytotoxic only at high concentrations in Scaber, SIHA, and MKN45 cells (IC50s = 97, 578, and 994 µM, respectively) and is inactive in a variety of cancer cell lines, including COLO 205, HCT116, and MCF-7 cells (IC50s = >1,000 µM).
1.Miwa, M., Ura, M., Nishida, M., et al.Design of a novel oral fluoropyrimidine carbamate, capecitabine, which generates 5-fluorouracil selectively in tumours by enzymes concentrated in human liver and cancer tissueEur. J. Cancer34(8)1274-1281(1998)