Voraxaze (glucarpidase) contains a recombinant enzyme which rapidly lowers blood levels of methotrexate, reducing its concentration to below the threshold for serious toxicity. Voraxaze converts methotrexate to its inactive metabolites DAMPA and glutamate. DAMPA and glutamate are metabolized by the liver, providing an alternative route of methotrexate elimination to renal clearance during high-dose methotrexate treatment.
Voraxaze is specifically indicated for the treatment of toxic plasma methotrexate concentrations (>1 micromole per liter) in patients with delayed methotrexate clearance due to impaired renal function.
Voraxaze is supplied as a solution for intravenous administration. The recommended dose is a single intravenous injection of 50 Units per kg. as a bolus injection over 5 minutes.
The FDA approval of Voraxaze was based on an efficacy and safety study.
A single clinical study enrolled 22 subjects. All subjects received Voraxaze treatment. The treatment was considered effective if the methotrexate level fell below a critical level within 15 minutes and stayed below the critical level for eight days. Ten of the 22 subjects achieved this standard. Voraxaze eliminated 95% of the methotrexate in all subjects, regardless of whether they reached the efficacy endpoint.
A separate clinical study evaluated the safety of Voraxaze in 290 subjects experiencing problems clearing methotrexate from their blood. The most common side effects observed in greater than one percent of subjects in the clinical study were low blood pressure (hypotension), headache, nausea, vomiting, flushing, and abnormal sensation (paraesthesia).
Adverse events associated with the use of Voraxaze may include, but are not limited to, the following:
Voraxaze (glucarpidase) is a recombinant bacterial enzyme that hydrolyzes the carboxyl-terminal glutamate residue from folic acid and classical antifolates such as methotrexate. Voraxaze converts methotrexate to its inactive metabolites 4-deoxy-4-amino-N10-methylpteroic acid (DAMPA) and glutamate. DAMPA and glutamate are metabolized by the liver, providing an alternative route of methotrexate elimination to renal clearance during high-dose methotrexate treatment.
For additional information regarding Voraxaze or toxic plasma methotrexate concentrations in patients with delayed methotrexate clearance due to impaired renal function, please visit the BTG International web page.