Antimetabolite

An antimetabolite is a chemical with a similar structure to a substance (a metabolite) required for normal biochemical reactions, yet different enough to interfere with the normal functions of cells, including cell division.

Function

Cancer treatment

Antimetabolites can be used in cancer treatment, as they interfere with DNA production and therefore cell division and the growth of tumors. Because cancer cells spend more time dividing than other cells, inhibiting cell division harms tumor cells more than other cells.

Anti-metabolites masquerade as a purine (azathioprine, mercaptopurine) or a pyrimidine - which become the building blocks of DNA. They prevent these substances becoming incorporated in to DNA during the S phase (of the cell cycle), stopping normal development and division.

They 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.

Due to their efficiency, these drugs are the most widely used cytostatics.

In the ATC system, they are classified under L01B.

Antibiotics

Antimetabolites may also be antibiotics, such as sulfanilamide drugs, which inhibit dihydrofolate synthesis in bacteria by competing with para-aminobenzoic acid.

Types

Main representatives of these drugs are:

• purine analogues
• pyrimidine analogues
• antifolates