Phase 2 study of glucarpidase in patients with delayed methotrexate elimination after high-dose methotrexate therapy.

Purpose: High-dose methotrexate therapy (HD-MTX) is a standard treatment for various malignant tumors, but approximately 1-10% of patients experience delayed MTX elimination (DME) that can induce organ damage. Glucarpidase can hydrolyze MTX and thereby lower the level of active MTX in the blood. A multicenter, open-label, phase II investigator-initiated trial (CPG2-PII study) was conducted to evaluate glucarpidase rescue therapy in Japanese patients who showed DME after HD-MTX treatment. To confirm the robustness of this therapy, further corporate-sponsored clinical trial (OP-07-001 study) was conducted.

Methods: The primary endpoint in the CPG2-PII study was to evaluate the proportion of patients of the percentage clinical important reduction (CIR) as an indicator of MTX concentration, which can be managed with leucovorin and supportive care. The primary endpoint of the OP-07-001 study was to evaluate the decreasing rate of plasma MTX concentration at 20 min after glucarpidase administration from the baseline for four patients. Glucarpidase was administered at a dose of 50 U/kg for 15 and 4 patients, respectively in the two studies, and safety was analyzed for each of them.

Results: The rate of CIR was 76.9% (95% confidence interval, 46.2-95.0%) in the CPG2-PII study. The median reduction rate of plasma MTX was 98.83% in the OP-07-001 study. Hypersensitivity, blood bilirubin increased, and headache for each patient were the only study drug-related events.

Conclusion: Glucarpidase showed an effect of reducing plasma MTX concentration in Japanese patients with DME as that observed in a previous US study, confirming its favorable safety and tolerability.