Phase II trial of merbarone in patients with malignant brain tumors

The standard treatment for patients with primary malignant glioma includes surgical resection, radiotherapy, and nitrosourea. Despite this multimodality approach, adults with newly diagnosed glioblastoma multiforme (GBM) and high-grade astrocytoma have a median survival duration of 50 weeks and 150 weeks respectively. Chemotherapy has had a limited impact on the survival of these patients. Merbarone (5-phenylcarboxamide-2-thiobarbituric acid) is a nonsedating derivative of barbituric acid that crosses the blood brain barrier. Antitumor activity of merbarone has been described against L1210, B16 melanoma cell line and the M5076 sarcoma cells in phase I studies. Merbarone inhibits DNA synthesis and tumor growth by inducing single strand breaks in DNA. It also inhibits RNA and protein synthesis. We evaluated merbarone in a phase II trial in patients (pts) with recurrent or refractory GBM (7 pts) and high grade anaplastic astrocytoma (7 pts). Fourteen patients (nine males, five females) were treated with merbarone at a dose of 1000 mg per m² per day by continuous intravenous infusion for 5 days every 3 weeks. Every patient received at least two cycles of treatment No complete or partial responses were observed, although one patient had stable disease lasting 20 weeks. Our conclusion is that merbarone is ineffective against GBM and high-grade anaplastic astrocytoma at the dose and schedule in which it was administered in this trial.