Which medications in the drug class Antineoplastic Agent, Antimetabolite (pyrimidine analog) are used in the treatment of Colon Cancer?

Updated: Apr 15, 2020
  • Author: Tomislav Dragovich, MD, PhD; Chief Editor: N Joseph Espat, MD, MS, FACS  more...
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Answer

Antineoplastic Agent, Antimetabolite (pyrimidine analog)

These agents inhibit cell growth and proliferation.

5-Fluorouracil

Fluoropyrimidine analog. Cell cycle-specific with activity in the S-phase as single agent and has for many years been combined with biochemical modulator leucovorin. It inhibits DNA replication and transcription. Cytotoxicity is cell-cycle nonspecific. Classic antimetabolite anticancer drug with chemical structure similar to endogenous intermediates or building blocks of DNA or RNA synthesis. 5-FU inhibits tumor cell growth through at least 3 different mechanisms that ultimately disrupt DNA synthesis or cellular viability. These effects depend on intracellular conversion of 5-FU into 5-FdUMP, 5-FUTP, and 5-FdUTP. 5-FdUMP inhibits thymidylate synthase (key enzyme in DNA synthesis), which leads to accumulation of dUMP, which then gets misincorporated into the DNA in the form of 5-FdUTP resulting in inhibition of DNA synthesis and function with cytotoxic DNA strand breaks. 5-FUTP is incorporated into RNA and interferes with RNA processing.

Capecitabine (Xeloda)

Fluoropyrimidine carbamate prodrug from of 5-fluorouracil (5-FU). Capecitabine itself is inactive. Undergoes hydrolysis in liver and tissues to form the active moiety (fluorouracil), inhibiting thymidylate synthetase, which in turn blocks methylation of deoxyuridylic acid to thymidylic acid. This step interferes with DNA and to a lesser degree with RNA synthesis.


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