ChEBI: Methotrexate is a member of pteridines, a monocarboxylic acid amide and a dicarboxylic acid. It has a role as an antineoplastic agent, an antirheumatic drug, an EC 1.5.1.3 (dihydrofolate reductase) inhibitor, a DNA synthesis inhibitor, an abortifacient, a dermatologic drug, an antimetabolite and an immunosuppressive agent. It derives from a L-glutamic acid. It is a conjugate acid of a methotrexate(1-).NCI Thesaurus (NCIt): Methotrexate is an antimetabolite and antifolate agent with antineoplastic and immunosuppressant activities. Methotrexate binds to and inhibits the enzyme dihydrofolate reductase, resulting in inhibition of purine nucleotide and thymidylate synthesis and, subsequently, inhibition of DNA and RNA syntheses. Methotrexate also exhibits potent immunosuppressant activity although the mechanism(s) of actions is unclear.