Phase I trial of bortezomib in adults with recurrent malignant glioma

Abstract

1567 Background: Bortezomib is a selective inhibitor of the proteasome that has been approved for the treatment of multiple myeloma and has also shown promising evidence of clinical activity against solid tumors. This study was undertaken to determine the maximum tolerated dose (MTD), toxicity profile, and biologic activity of bortezomib for the treatment of recurrent malignant glioma (MG). Methods: Eligible patients (pts) had supratentorial progressive MG upon radiotherapy and ≤ 1 prior regimen of chemotherapy. Dose escalation was conducted separately for pts taking enzyme inducing antiseizure drugs (EIASD+) and for those not (EIASD-). Bortezomib was given by bolus iv injection on weeks 1 and 2 of each 3 week cycle of therapy. The starting dose in both groups was 0.9 mg/m2. Cohorts of at least 3 patients were evaluated at each dose level. 20S proteasome activity was determined in whole blood lysates before and at 1 and 24 h after the first dose. Results: Fifty-nine evaluable pts (41 male/18 female) with a median age of 51 years and median KPS of 90% have been enrolled. All but 2 pts had received 1 prior chemotherapy regimen. In the EIASD- group, the weekly dose was escalated from 0.9 to 1.9 mg/m2 through 3 intermediate dose levels, with 1.7 mg/m2 established as the MTD. DLT experienced by 2 of 6 pts in the 1.90 mg/m2 dose level were grade 3 thrombocytopenia and grade 3 fatigue plus neurosensory toxicities. In the EIASD+ group, the dose has been escalated to 2.3 mg/m2 without the occurrence of any DLT. Ten additional EIASD- pts were treated at 1.7 mg/m2, with the most common adverse events being thrombocytopenia and peripheral neuropathy. The extent of proteasome inhibition in whole blood increased in a dose-dependent manner in both treatment groups. Mean proteasome inhibition in EIASD+ pts 1 h after receiving 2.1 mg/m2 of bortezomib (77 ± 12%) was similar to the 1.7 mg/m2 dose in EIASD- pts (79 ± 6%). Conclusions: The MTD for the weekly x 2 schedule of bortezomib in EIASD- patients, 1.7 mg/m2, is higher than the approved dose of 1.3 mg/m2 for the treatment of multiple myeloma. The enhanced tolerability of the drug when given together with EIASDs, for which the MTD is at least 2.1 mg/m2, is consistent with the diminished inhibition of 20S proteasome activity in these pts. No significant financial relationships to disclose.