Methotrexate polyglutamate quantification for clinical application in patients with pediatric acute lymphoblastic leukemia in association with genetic polymorphisms.

Abstract We developed and validated a quantification method for methotrexate (MTX) polyglutamates (MTX-PGs, MTX-PG1 to MTX-PG5) by liquid chromatography-tandem mass spectrometry using stable isotope-labeled internal standards and applied to 196 clinical samples collected from pediatric acute lymphoblastic leukemia patients treated with MTX. MTX-PGs levels and their proportions (%) in sum of all MTX-PGs (MTXSum) were evaluated in relation to TPMT, NUDT15, and MTHFR genotypes. For the developed method, linearity ranges 1−500 nmol/L, bias for accuracy 0.3–13.5 %, coefficient of variation for within- and between-run imprecision of 3.2−9.5% and 1.5−12.0%, respectively. Recoveries achieved were 74.2–105.8 %. There was no significant carryover. The median level of the MTXSum for 196 clinical samples was 129.4 nmol/L (interquartile range 28.1−241.2). MTX dose and MTX-PGs were associated (P