Successful carboxypeptidase G2 rescue in delayed methotrexate elimination due to renal failure.

We report on an 18.5-year-old woman with osteosarcoma and delayed methotrexate (MTX) elimination due to renal failure after high-dose MTX, in whom rescue with high doses of folinic acid caused intolerable side effects. In this life-threatening clinical situation, the patients was rescued by the administration of recombinant carboxypeptidase G2, a bacterial enzyme that rapidly hydrolyzes MTX into inactive metabolites. This is the first report on the successful clinical use of this alternative catabolic route for the elimination of MTX.