Antifolate

A well known example is Methotrexate. This is a folic acid analogue, and owing to structural similarity with it binds and inhibits the enzyme dihydrofolate reductase, and thus prevents the formation of tetrahydrofolate. Tetrahydrofolate essential for purine and pyrimidine synthesis, and this leads to inhibited production of DNA, RNA and proteins (as tetrahydrofolate is also involved in the synthesis of amino acids serine and methionine).

Other examples include trimethoprim, pyrimethamine and pemetrexed.

Since, antifolates interfere with metabolism (of nucleotides), they are categorized as antimetabolites. Their action specifically targets the fast-dividing cells, and tend to have adverse effects on the bone marrow, skin and hair.

Many new drugs are under development to reduce antifolate drug resistance.

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