As a prodrug, Capecitabine is selectively activated by tumor
cells to its cytotoxic moiety, 5-fluorouracil (5-FU). 5-FU is
metabolized to two active metabolites, 5-fluoro-2-
deoxyuridine monophosphate (FdUMP) and 5-fluorouridine
triphosphate (FUTP) by both tumor cells and normal cells.
FdUMP inhibits DNA synthesis and cell division by reducing
normal thymidine production, while FUTP inhibits RNA and
protein synthesis by competing with uridine triphosphate for
incorporation into the RNA strand.