Glucarpidase mode of action. (A) Glucarpidase cleaves the glutamate residue from MTX resulting in the nontoxic metabolite DAMPA. (B) Rapid decrease of the MTX blood concentration after glucarpidase administration in a patient with osteosarcoma and acute kidney injury after HDMTX therapy. Quantification by high-performance liquid chromatography (HPLC) demonstrates an increase of the metabolite DAMPA parallel to the decrease of MTX, whereas the MTX concentration is overestimated by immunoassay (IA) measurements due to interference with the DAMPA metabolite.