A Trial of Carboxypeptidase-G2 (CPDG2) and Thymidine for the Management of Patients With Methotrexate Toxicity and Renal Dysfunction

High dose methotrexate with leucovorin rescue has demonstrated activity in numerous malignancies. Although high dose methotrexate is generally well tolerated, unpredictable life-threatening toxicity can occur. For patients who have markedly delayed clearance of methotrexate secondary to renal dysfunction, therapeutic options are few and are of limited efficacy. Carboxypeptidase-G2 inactivates methotrexate by hydrolyzing its C-terminal glutamate residue. Carboxypeptidase-G2 could be used to rescue patients with renal dysfunction and delayed methotrexate excretion, as it provides an alternative to renal clearance as a route of elimination.

Patients of any age at risk for life-threatening toxicity following MTX administration secondary to delayed drug excretion as defined by:

Plasma MTX concentration at least 10 micromoles/liter more than 42 hours after the start of the MTX infusion; OR

Creatinine at least 1.5 times the upper limit of normal or creatinine clearance less than 60 ml/sqm/min and delayed MTX excretion documented by plasma MTX concentration measurements (at least 2 standard deviations above the mean) at least 12 hours following MTX administration.