Antifolates are antimetabolites that inhibit the enzyme dihydrofolate reductase (DHFR) which converts dihydrofolate (DHF) to tetrahydrofolate (THF) and/or related enzymes in the same nucleic acid synthesis pathway such as thymidylate synthase. Examples include aminopterin (the first such agent developed for clinical use, been largely replaced by methotrexate), methotrexate (which has been in clinical use since the 1950s), pemetrexed and raltitrexed. These agents with significant activity against human enzymes are widely used as cancer drugs and immunosuppressants.
Some antibiotics and antiprotozoals also inhibit DHFR, examples include: proguanil, pyrimethamine and trimethoprim. Sulfonamides like sulfadoxine inhibit the microbial biosynthesis of folate via the enzyme dihydropteroate synthase and hence can also be loosely called antifolates.
|Chemotherapeutic agents (ATC: L01)|