Methotrexate;甲氨蝶呤;1959-5-2 Formula:C20H22N8O5 Methotrexate (MTX; alphamethopterin; amethopterin; methylaminopterin; CL-14377; NCIC04671; WR19039; NCI-C04671) is an FDA approved antineoplastic and immunosuppressant drug that belongs to the antimetabolite and antifolate class of drugs. It acts by inhibiting the metabolism of folic acid in activated peripheral T cells. Specifically, 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.