7-hydroxy Methotrexate

7-hydroxy Methotrexate (7-hydroxy MTX) is the major metabolite of the folic acid derivative MTX (Item No. 13960).{34769} It is formed by the 7-oxidation of MTX by hepatic aldehyde oxidases. Unlike MTX, 7-hydroxy MTX does not inhibit thymidylate synthase in isolated human acute myeloid and acute lymphoblastic leukemia cells.{64002} 7-hydroxy MTX has a maximum tolerated dose of 0.1 g/kg, which is 30- to 50-fold lower than MTX, in rats.{64003} Serum levels of 7-hydroxy MTX have been used as a marker of MTX toxicity during chemotherapy.{34772,34770}