Methods of Quantifying Methotrexate Metabolites

Abstract

The present invention provides a method for efficiently converting methotrexate polyglutamates to methotrexate in a cellular extract by contacting the cellular extract with gamma glutamyl hydrolase under conditions suitable for efficient conversion of methotrexate polyglutamates to methotrexate.

1 . A method for predicting therapeutic efficacy or reducing toxicity associated with methotrexate (MTX) therapy administered to an individual, comprising the steps of: (a) converting methotrexate polyglutamates (MTXPGs) to MTX in a cellular extract from said individual under conditions suitable for efficient conversion of MTXPGs to MTX; (b) determining a level of MTX in said cellular extract, said level of MTX correlating with a level of MTXPGs, thereby determining a level of MTXPGs in said cellular extract, wherein a drug or dosage subsequently administered to said individual is selected based on said level of MTXPGs.