Dose Dense Re-challenge of High Dose Methotrexate With Glucarpidase for Relapsed Primary Central Nervous System Lymphoma

High dose intravenous Methotrexate (HD-MTX) is the key drug in the treatment of primary central nervous system lymphoma (PCNSL). HD-MTX is usually delivered with time interval ranging from 10 to 21 days. Reduction of injection time interval is limited by MTX renal excretion and systemic toxicity. Glucarpidase (CPG2) is a recombinant bacterial rescue enzyme that cleaves circulating MTX into inactive metabolites, reducing plasma MTX concentrations within few minutes. The research hypothesis is that CPG2 used after HD-MTX injection allows to reduce time interval between MTX injections, increase dose intensity of the chemotherapy, reduce systemic toxicity and duration of hospitalization.