Antimetabolite

An antimetabolite is a chemical that inhibits the use of a metabolite, which is another chemical that is part of normal metabolism. Such substances are often similar in structure to the metabolite that they interfere with, such as the antifolates that interfere with the use of folic acid; thus, competitive inhibition can occur, and the presence of antimetabolites can have toxic effects on cells, such as halting cell growth and cell division, so these compounds are used as chemotherapy for cancer. Antimetabolites can be used in cancer treatment, as they interfere with DNA production and therefore cell division and tumor growth. Because cancer cells spend more time dividing than other cells, inhibiting cell division harms tumor cells more than other cells. Antimetabolite drugs are commonly used to treat leukemia, cancers of the breast, ovary, and the gastrointestinal tract, as well as other types of cancers. In the Anatomical Therapeutic Chemical Classification System antimetabolite cancer drugs are classified under L01B. Antimetabolites generally impair DNA replication machinery, either by incorporation of chemically altered nucleotides or by depleting the supply of deoxynucleotides needed for DNA replication and cell proliferation. Examples of cancer drug antimetabolites include, but are not limited to the following: 5-Fluorouracil (5-FU) 6-Mercaptopurine (6-MP) Capecitabine (Xeloda®) Cytarabine (Ara-C®) Floxuridine Fludarabine Gemcitabine (Gemzar®) Hydroxycarbamide Methotrexate Pemetrexed (Alimta®) Phototrexate Anti-metabolites masquerade as a purine (azathioprine, mercaptopurine) or a pyrimidine, chemicals that become the building-blocks of DNA. They prevent these substances from becoming incorporated into DNA during the S phase (of the cell cycle), stopping normal development and cell division. Anti-metabolites also affect RNA synthesis. However, because thymidine is used in DNA but not in RNA (where uracil is used instead), inhibition of thymidine synthesis via thymidylate synthase selectively inhibits DNA synthesis over RNA synthesis.